Protective film for visual display device process

Abstract

The present application provides a kind of visual display device process protective film, including substrate layer and urethane adhesive layer, the urethane adhesive layer is the cured product of the composition comprising polyurethane main agent resin, plasticizer and silicone modified polyacrylate (Silicone modified Polyacrylate), and satisfies condition (1) and condition (2).

Description

Technical Field

[0001] This invention relates to a protective film used in the manufacturing process of a visual display device. Background Technology

[0002] Visual display devices undergo numerous steps during their manufacturing and processing. During these processes, scratches and other damage may occur on the surface of the visual display device, which can increase the rejection rate of the final product.

[0003] For example, display devices typically have thin-film transistor (TFT) circuitry formed on a bare glass substrate, followed by encapsulation. Display devices manufactured in this way undergo thinning processes to reduce their overall thickness, are cut to specified units, and then undergo necessary circuit wiring processes such as attaching a flexible printed circuit board (FPCB) and driver IC attachment processes to achieve various display functions. In addition, many extra steps, such as inspection processes, are performed. During these numerous processes, scratches and other damage may occur on the surface of the display device, and this surface damage increases the rejection rate of the final product.

[0004] To address this problem, a protective film is used to protect the surface of the visual display device from damage during processing.

[0005] The protective film is attached to the surface of a visual display device to prevent contamination or damage during processing and is removed after processing. Therefore, the protective film must adhere firmly to the surface of the display device, and should be removable with low peel force, leaving minimal adhesive residue. Furthermore, the adhesive layer of the protective film must not be easily broken by impacts applied during the visual display device manufacturing process. Summary of the Invention

[0006] The technical problem to be solved The purpose of this invention is to provide a protective film for use in the manufacturing process of a visual display device, which includes an adhesive layer with a surface energy within a specified range. The adhesive layer is not easily broken by impacts or other factors applied during the manufacturing process of the visual display device, thereby reducing adhesive residue after the protective film is removed.

[0007] Furthermore, the object of the present invention is to provide a protective film for use in the process of a visual display device, which can be easily removed with low peeling force when removed from the visual display device.

[0008] Furthermore, the object of the present invention is to provide a protective film for use in the process of a visual display device, which can be easily removed not only from the glass included in the visual display device, but also from other adhered objects with low peeling force.

[0009] The objectives of this invention are not limited to those described above. Other objectives and advantages of this invention not mentioned herein may be understood through the following description and will become clearer through embodiments of the invention. Furthermore, it will be readily understood that the objectives and advantages of this invention can be achieved through methods and combinations thereof within the scope of the claims.

[0010] Technical solutions to solve technical problems The present invention can provide a protective film for a visual display device process, comprising a substrate layer and a urethane adhesive layer, wherein the urethane adhesive layer is a cured product of a composition comprising a polyurethane main resin, a plasticizer and a silicone modified polyacrylate, and satisfies conditions (1) and (2).

[0011] Condition (1): The surface energy of the urethane adhesive layer is 18.7 mN / m to 38.5 mN / m. Condition (2): The residual adhesion rate of the urethane adhesive layer according to Formula 1 below is 90% or more. Formula 1: Residual adhesion ratio = (Adhesion force B / Adhesion force A) × 100 In Equation 1 above, the adhesion force A is the result of attaching Nitto 31B tape to a glass surface and leaving it at room temperature for 24 hours, then applying it at 180°C. The adhesive strength was measured by peeling the nitto 31B tape from the glass at a peel angle, a peel length of 120 mm, and a speed of 5 mm / s. Adhesion force B is determined by applying the urethane adhesive layer to the glass surface and leaving it at room temperature for 24 hours, then removing it. Next, nitto 31B tape is applied to the area where the urethane adhesive layer was removed and left at room temperature for 24 hours. Then, 180... The adhesive strength was measured by peeling the nitto 31B tape from the glass at a peel angle, a peel length of 120 mm, and a speed of 5 mm / s.

[0012] The protective film used in the visual display device process can meet condition (3).

[0013] Condition (3): The urethane adhesive layer is attached to the glass and left at room temperature for 24 hours, then at 180°C. The peeling force when peeling the protective film from the glass at a peeling angle of 5 mm / s and a peeling speed of 5 mm / s is 1 to 3 gf / in.

[0014] The protective film used in the visual display device process can meet condition (4).

[0015] Condition (4): Attach the urethane adhesive layer to the acrylic sheet and leave it at room temperature for 24 hours, then heat it at 180°C. At a peeling angle of 5 mm / s, the peeling force when peeling the protective film from the acrylic plate is 1–3 gf / in. In the adhesive composition, the content of the silicone modified polyacrylate may be from 0.19 parts by weight to 0.6 parts by weight relative to 100 parts by weight of the polyurethane main resin solids.

[0016] In the adhesive composition, the content of the plasticizer may be from 10 parts by weight to 35 parts by weight relative to 100 parts by weight of the polyurethane main resin solids.

[0017] The plasticizer can be a compound containing two or more ester groups.

[0018] The plasticizer may include triethylene glycol bis(2-ethylhexanoate), acetyl tributyl citrate, or a combination thereof.

[0019] The protective film used in the visual display device process may include an antistatic coating disposed on the other side of the substrate layer where the adhesive layer is not disposed.

[0020] The protective film used in the visual display device process may also include a release layer disposed on the other side of the adhesive layer where no substrate layer has been formed.

[0021] Invention Effects The protective film for the visual display device process of the present invention includes an adhesive layer having a surface energy within a specified range. The adhesive layer is not easily broken by impacts or other factors applied during the visual display device processing, and the adhesive residue can be reduced after the protective film is removed.

[0022] Furthermore, when the protective film for the visual display device process of the present invention is removed from the visual display device, it can be removed with low peeling force.

[0023] Furthermore, the protective film for the visual display device process of the present invention can be removed not only from the glass included in the visual display device, but also from other adhered objects with low peeling force.

[0024] In addition to the effects described above, the specific effects of the present invention will be described while explaining the following specific embodiments. Attached Figure Description

[0025] Figure 1 A protective film for use in the manufacturing process of a visual display device according to an embodiment of the present invention is briefly shown.

[0026] Figure 2 A protective film for use in the manufacturing process of a visual display device according to another embodiment of the present invention is briefly shown.

[0027] Figure 3 A brief illustration shows the state in which a protective film is attached to an object during the visual display device process according to another embodiment of the present invention.

[0028] Figure 4 The results of a pencil scratch test are shown for a protective film used in the process of a visual display device according to another example of the present invention, based on Example 4.

[0029] Figure 5 The protective film used in the process of the visual display device shown in the comparative example is based on the results of the pencil scratch test in Experimental Example 4.

[0030] Explanation of reference numerals in the attached figures 100: Protective film for visual display device processes 10: Substrate layer 20: Ethyl carbamate adhesive layer 30: Release layer (release film) 200: The object to be adhered to. Detailed Implementation

[0031] The aforementioned objectives, features, and advantages will be described in detail later, thus enabling those skilled in the art to readily grasp the technical concept of this invention. In describing this invention, detailed descriptions of related prior art will be omitted if it is determined that such descriptions may unnecessarily obscure the main points of the invention. Preferred embodiments of the invention will now be described in detail.

[0032] In the following, the phrase "any structure is positioned on the upper (or lower) part" or "above (or below)" of a structural element not only means that any structure is configured to contact the upper (or lower) surface of the structural element, but may also mean that other structures may be positioned between the structural element and any structure positioned on (or below) the structural element.

[0033] In this specification, "main resin" refers to the resin that constitutes the largest weight percentage of the components of the composition, excluding the solvent.

[0034] In this specification, "weight-average molecular weight" refers to the conversion value of standard polystyrene as determined by gel permeation chromatography (GPC).

[0035] In this instruction manual, "room temperature" refers to a temperature of approximately 23°C.

[0036] In this specification, the adherend refers to the substance to which the adhesive layer can adhere. In one embodiment, the adherend includes the encapsulation layer of the organic light-emitting device and the plastic substrate applied to the device, but is not limited thereto.

[0037] The following will describe a protective film for a visual display device process according to some examples of the present invention.

[0038] Figure 1 A protective film for use in a visual display device according to an embodiment of the present invention is briefly illustrated, comprising a substrate layer and a urethane adhesive layer laminated on one side of the substrate layer. Each structure will be described in detail below.

[0039] The substrate layer serves to protect the surface of the visual display device. The substrate layer may, without limitation, include materials commonly used in the art for protective films. For example, it may include polyethylene terephthalate (PET) film.

[0040] Furthermore, an antistatic coating can be formed on the side of the substrate layer where no adhesive layer is provided. This antistatic coating can exhibit antistatic properties by containing a conductive polymer.

[0041] The thickness of the substrate layer is not limited, as long as it is the thickness of a substrate film commonly used for protective films. Preferably, it can be 50 to 100 μm, more preferably 70 to 80 μm, but it is not limited thereto.

[0042] The protective film used in the visual display device process includes an adhesive layer that allows the substrate layer to adhere to the surface of the visual display device. The adhesive layer is a urethane adhesive layer, comprising a cured product of a composition containing a polyurethane base resin, a plasticizer, and a silicone-modified polyacrylate. Each structure will be described in detail below.

[0043] The weight-average molecular weight of the polyurethane main agent resin can be 50,000 to 150,000 g / mol, preferably 60,000 to 90,000 g / mol. When the weight-average molecular weight of the polyurethane main agent resin is less than the range, it may lead to a decrease in flexibility; when it is greater than the range, it may lead to a decrease in the hardness and abrasion resistance of the adhesive layer, but it is not limited thereto.

[0044] The polyurethane main resin can be a compound copolymerized from polyol and polyfunctional isocyanate. There are no particular limitations on the polyol and isocyanate, as long as the polyurethane resin has a weight-average molecular weight within the specified range.

[0045] The polyol may contain one polyol, and preferably, it may contain two or more polyols.

[0046] Furthermore, one of the two or more polyols may include a polyol having three or more OH groups, specifically, it may include one or more selected from polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols and castor oil polyols.

[0047] Polyester polyols can be obtained through esterification reactions between polyol components and acid components. The polyol components may include one or more selected from ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerol, trimethylolpropane, pentaerythritol, hexanediol, and polypropylene glycol. The acid component may include one or more selected from succinic acid, methylsuccinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanoic acid, 1,14-tetradecanoic acid, dimer acid, 2-methyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-biphenylcarboxylic acid, and their anhydrides.

[0048] Polyether polyols can be obtained by using water, low molecular weight polyols (propylene glycol, ethylene glycol, glycerol, trimethylolpropane, pentaerythritol, etc.), bisphenols (bisphenol A, etc.), and dihydroxybenzenes (dihydroxybenzene, resorcinol, hydroquinone, etc.) as initiators to induce the addition polymerization of alkyl oxidants selected from ethylene oxide, propylene oxide, or butane oxide. As a specific example, polyether polyols include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0049] Polycaprolactone polyols can be caprolactone-based polyester diols obtained through ring-opening polymerization of cyclic ester monomers such as ε-caprolactone or σ-valerolactone. As a specific example, polycaprolactone polyols can be polycarbonate polyols obtained by polycondensation of a polyol component with phosgene; polycarbonate polyols obtained by transesterification and condensation reactions of a polyol component with carbonate diesters such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, dibutyl carbonate, ethyl butyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, or dibenzyl carbonate; copolymer polycarbonate polyols obtained by combining two or more polyol components; and polycarbonate polyols obtained by esterification reactions of various polycarbonate polyols with carboxyl-containing compounds. Polycarbonate polyols; polycarbonate polyols obtained by etherification of various polycarbonate polyols with hydroxyl-containing compounds; polycarbonate polyols obtained by transesterification of various polycarbonate polyols with ester compounds; polycarbonate polyols obtained by transesterification of various polycarbonate polyols with hydroxyl-containing compounds; polyester polycarbonate polyols obtained by polycondensation of various polycarbonate polyols with dicarboxylic acid compounds; and copolymer polyether polycarbonate polyols obtained by copolymerization of various polycarbonate polyols with epoxides, etc.

[0050] Castor oil polyols can be obtained by reacting castor oil fatty acids with polyol components.

[0051] The polyol having three or more OH groups is a polyol containing 1 to 99% by weight of two or more polyol components, more preferably, it can be a polyol containing 10 to 90% by weight.

[0052] The polyfunctional isocyanate may include one or more selected from polyfunctional aliphatic isocyanates, polyfunctional alicyclic isocyanates, polyfunctional aromatic diisocyanates, and trimers having an isocyanurate ring.

[0053] As an example of a multifunctional aliphatic isocyanate, it may include one selected from trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,2-propene diisocyanate, 1,3-butene diisocyanate, dodecane diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate.

[0054] As an example of a polyfunctional alicyclic isocyanate compound, it may contain one or more selected from 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylene diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated tetramethylxylene diisocyanate.

[0055] The polyfunctional aromatic diisocyanate compound may contain one or more selected from phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate and xylene diisocyanate.

[0056] Furthermore, the polyfunctional isocyanate may include one or more of the following: trimethylolpropane adducts selected from various polyfunctional isocyanates, biuret obtained by reaction with water, and trimers having an isocyanurate ring.

[0057] The composition contains a plasticizer. Existing urethane adhesives incorporate a single ester-based plasticizer, such as isopropyl myristate (IPM) or isopropyl palmitate (IPP), to reduce peel strength. However, while low peel strength can be achieved when plasticizers as described above are included, the plasticizer can diffuse into other substances in contact with the product surface and be lost (migration), leading to surface contamination and a decrease in residual adhesive yield.

[0058] The composition may contain compounds with two or more ester groups as plasticizers. A low peel strength within a specified range can be maintained by containing compounds with two or more ester groups as plasticizers. Furthermore, making the adhesive layer soft makes it less susceptible to breakage from impacts or other forces applied during processing, and results in less adhesive residue after removal of the protective film, thus exhibiting a high residual adhesion rate. For example, the plasticizer may include, but is not limited to, triethylene glycol bis(2-ethylhexanoate) having two ester groups, or acetyl tributyl citrate having four ester groups, or combinations thereof.

[0059] Triethylene glycol bis(2-ethylhexanoate)

[0060] Acetyl tributyl citrate

[0061] The molecular weight of the plasticizer can be from about 300 g / mol to 550 g / mol. Furthermore, the boiling point of the plasticizer can be from 300°C to 420°C, and the melting point of the plasticizer can be from -80°C to -48°C, but is not limited thereto.

[0062] The composition may contain 10 to 35 parts by weight of the plasticizer relative to 100 parts by weight of the polyurethane main resin solids component.

[0063] The composition comprises silicone-modified polyacrylate. Therefore, the surface energy of the urethane adhesive layer can be maintained within a specified range, exhibiting low peel strength even to substrates other than glass, thus allowing for easy removal from the visual display device.

[0064] The silicone-modified polyacrylate can be added to the composition in the form of a solution contained in the solvent methoxypropylacetate. The solution has a specific gravity (at 20°C) of 1 g / mol, a flash point of 30°C to 50°C, and can be treated at 150°C for 30 minutes to obtain 25% by weight of solids. The silicone-modified polyacrylate may have hydroxyl groups (-OH) with an OH value of approximately 20 mg KOH / g to 40 mg KOH / g.

[0065] The silicone-modified polyacrylate can be a polymer of a (meth)acrylate monomer containing silicone and monomers containing other (meth)acrylate monomers. The silicone-modified polyacrylate may contain a (meth)acrylate monomer containing silicone as a monomer unit. The other (meth)acrylate monomers can be used without limitation, as long as they are monomers that can polymerize without inhibiting the effects of the present invention. For example, it may also contain (meth)acrylate monomers such as alkyl (meth)acrylates, cyclohexyl (meth)acrylates, and aromatic (meth)acrylates with 5 to 22 carbon atoms, but is not limited thereto.

[0066] The content of the silicone-modified polyacrylate can be from 0.19 parts by weight to 0.6 parts by weight relative to 100 parts by weight of the polyurethane main resin solids. For example, its content can be 0.57 parts or less. When the content of the silicone-modified polyacrylate exceeds the range described above, the desired effect cannot be achieved because the surface energy of the urethane adhesive layer exceeds the range of the present invention. Moreover, there may be a problem of a significant reduction in the peel strength to glass.

[0067] Furthermore, the composition may also contain a curing agent, and more particularly, may contain one or more selected from a delaying agent and an antistatic agent. Preferably, it may contain a curing agent, a delaying agent, and an antistatic agent.

[0068] Specifically, the curing agent may include an isocyanate curing agent, preferably, it may include one or more selected from hexamethylene diisocyanate (HDI), methylene diphenyl isocyanate (MDI) and toluene diisocyanate (TDI), more preferably, it may include hexamethylene diisocyanate (HDI).

[0069] The content of the curing agent can be 2 to 10 parts by weight relative to 100 parts by weight of the solid component of the polyurethane main agent resin. Therefore, while increasing the curing density, it can prevent the adhesive layer from breaking and generating foreign matter during the visual display device manufacturing process. For example, when the content of the curing agent is less than the specified range, there may be a problem of difficulty in reducing peel force due to poor curing; when it is greater than the specified range, there may be a problem of excessive curing density causing the adhesive layer to break and generate foreign matter during the manufacturing process, leading to an increased defect rate of the final product, but this is not the only possibility.

[0070] The composition may contain a retarding agent, specifically a diketone retarding agent as a curing retarding agent, preferably one or more selected from acetylacetone, butadiene sulfone, anhydrous acid, phosphoric acid and p-toluenesulfonic acid, more preferably acetylacetone.

[0071] Relative to 100 parts by weight of the polyurethane main resin solids, the composition may contain 1 to 10 parts by weight of a curing retarder, preferably 3 to 9 parts by weight, and more preferably 5 to 8 parts by weight. For example, when the content of the retarder is less than the range, there may be a problem of gel foreign matter being generated due to rapid curing; when it is greater than the range, there may be a problem of delayed curing reaction of urethane.

[0072] The composition can prevent the generation of static electricity by including an antistatic agent. For example, it can include one or more inorganic salts selected from alkali metals and organic salts of alkali metals as antistatic agents, and preferably, it can include lithium metal salts. For example, lithium bis(trifluoromethanesulfonyl)imide can be used as an antistatic agent.

[0073] The thickness of the urethane adhesive layer is not limited, as long as it is a thickness that is commonly used for adhesive layers in protective films. For example, preferably, the thickness of the adhesive layer can be 50-100 μm, more preferably, 70-80 μm, but it is not limited thereto.

[0074] Figure 2 A protective film for use in a visual display device process, another embodiment of the present invention, is briefly shown. This protective film further includes a release layer disposed on the other side of the adhesive layer where the substrate layer has not yet formed. Therefore, it can be a protective film consisting of a substrate layer, an adhesive layer, and a release layer stacked sequentially. The release layer protects both the urethane adhesive layer and the substrate layer. Figure 2 Example: A protective film with a substrate layer thickness of 75 μm, an adhesive layer thickness of 75 μm, and a release layer thickness of 50 μm.

[0075] The process of the visual display device is to use a protective film attached to the surface of the visual display device, and the release film of the release layer can be peeled off, and the adhesive layer can be attached to the upper part of the visual display device.

[0076] The release film may include materials commonly used in the art without limitation, and preferably may include polyethylene terephthalate (PET) film.

[0077] Furthermore, the release layer can be treated with an antistatic coating on the side of the release film where the adhesive layer is not attached. Moreover, an antistatic coating and a release coating with silicone can be applied to the other side of the release film.

[0078] The protective film used in the visual display device process can be antistatically coated on the substrate layer, release layer, or both simultaneously to reduce the amount of antistatic agent. Therefore, when the protective film is peeled off, static electricity can be prevented from forming on the surface of the adhesive layer. Furthermore, the thickness of the release film is not limited, as long as it is a thickness commonly used for protective films; preferably, it can be 10–50 μm, but is not limited thereto.

[0079] The protective film used in the process of the visual display device can meet the following conditions (1).

[0080] Condition (1): The surface energy of the urethane adhesive layer is 18.7 mN / m to 38.5 mN / m. The urethane adhesive layer exhibits a surface energy within the specified range, allowing it to adhere well to the surface of the visual display device to effectively protect it, and enabling easy removal with low peel force when the protective film is removed. Furthermore, it exhibits a low peel force within a defined range, unaffected by the material of the adhered object. That is, the peel force may be very low depending on the material of the adhered object. For example, when the surface energy of the urethane adhesive layer is less than the specified range, the interfacial attraction with the adhered object is too low, potentially making it difficult to meet the peel force required for the process. Moreover, when the surface energy of the urethane adhesive layer is greater than the specified range, there may be a problem where the peel force varies greatly depending on the material of the adhered surface. For example, it may exhibit low peel force for the glass portion of the visual display device, but there may be excessively high peel force for acrylic or other materials on the edges of the visual display device, such as the screen frame.

[0081] Furthermore, the protective film used in the visual display device process can meet the following condition (2).

[0082] Condition (2): The residual adhesion rate of the urethane adhesive layer according to Formula 1 below is 90% or more. Formula 1: Residual adhesion rate = (Adhesion force B / Adhesion force A) × 100 In Formula 1, the adhesive force A is the standard adhesive force, representing the force obtained by applying Nitto 31B tape to a glass surface and leaving it at room temperature for 24 hours, followed by application at 180°C. The adhesive strength was measured by peeling the nitto 31B tape from the glass at a peel angle, a peel length of 120 mm, and a speed of 5 mm / s. Adhesion force B indicates that after the urethane adhesive layer is applied to the glass surface and left at room temperature for 24 hours, it is removed. Then, Nitto 31B tape is applied to the area where the urethane adhesive layer has been removed and left at room temperature for 24 hours. Then, it is applied at 180°C. The adhesive strength was measured by peeling the nitto 31B tape from the glass at a peel angle, a peel length of 120 mm, and a speed of 5 mm / s.

[0083] According to Formula 1, a higher residual adhesion rate means less residue when the protective film is removed. For example, a residual adhesion rate of 100% means no adhesive layer remains.

[0084] According to Formula 1, the residual adhesion rate of the urethane adhesive layer is above 90%, resulting in minimal adhesive residue after removing the protective film, thus preventing contamination of the adhered material. For example, when the residual adhesion rate of the adhesive layer is less than this range, the adhesive may transfer to the visual display device panel. Therefore, removing the protective film may affect the product adhered to the panel surface and the thin film encapsulation (TFE) layer. This could potentially increase the defect rate of the final product.

[0085] Furthermore, the protective film used in the visual display device process can meet the following condition (3).

[0086] Condition (3): The urethane adhesive layer is attached to the glass and left at room temperature for 24 hours, then at 180°C. The peeling force when peeling the protective film from the glass at a peeling angle of 5 mm / s can be 1 to 3 gf / in.

[0087] Therefore, it can adhere well to the surface of the visual display device to protect the surface of the visual display device, and the protective film can be easily removed without damaging the visual display device.

[0088] Furthermore, the protective film used in the visual display device process can meet the following condition (4).

[0089] Condition (4): Attach the urethane adhesive layer to the acrylic sheet and leave it at room temperature for 24 hours, then heat it at 180°C. The peeling force when peeling the protective film from the acrylic plate at a peeling angle of 5 mm / s can be 1 to 3 gf / in.

[0090] The urethane adhesive layer of the protective film used in the visual display device process exhibits the same or similar peel force not only on the glass of the visual display device, but also on acrylic and other materials at the edges of the visual display device, such as the screen frame. Therefore, when the protective film is removed from the visual display device, it does not cause damage to the visual display device and prevents adhesive residue.

[0091] For example, when the peel force is less than the specified range, warping and / or bubbles may occur during the fabrication and processing of the visual display device. Furthermore, when the peel force is greater than the specified range, there is a risk that the protective film may not be peeled off, or that the thin-film encapsulation (TFE) layer of the panel may be torn during peeling.

[0092] The protective film used in the visual display device process can have a peel force difference of 0 to 1.4 or less depending on the substrate. This difference (Δ) can be a value calculated according to the following formula 2: Formula 2: Difference (Δ) = | Peeling force on glass (A) g1 - Peeling force on materials other than glass (A) g2 )| The adhesive layer of the protective film used in the visual display device process has a small difference value as described above, so that when the protective film is removed from the visual display device, it causes almost no damage to the visual display device, and it is easier to prevent the formation of adhesive residue. The difference value can be 0 to 1.2 or 0 to 1.1.

[0093] Furthermore, the protective film used in the visual display device process can meet the following condition (5): Condition (5): The water contact angle of the surface of the urethane adhesive layer can be 70° to 100°.

[0094] The urethane adhesive layer has a water contact angle within the stated range, thereby exhibiting the desired peel force and preventing peel force differences due to surface energy variations in the adhered surfaces. For example, when the water contact angle is less than the stated range, the adhesive force may vary significantly depending on the surface energy of the adhered surfaces; when the water contact angle is greater than the stated range, the interfacial attraction between the adhesive layer and the adhered surfaces is too low to meet the required peel force for the process.

[0095] Existing protective films used in visual display device processes achieve low peel strength by including a large amount of curing agent to increase curing density. However, such protective films are prone to breakage during processing due to the adhesive layer becoming too hard. Figure 5 The problem of particle dispersion is shown.

[0096] The protective film for the visual display device process possesses the aforementioned characteristics, thus the adhesive layer is less susceptible to breakage from impacts or other factors applied during the visual display device manufacturing process. Furthermore, it prevents an increase in the defect rate of the final product due to particle scattering. Specifically, when the adhesive layer is scratched with a pen, the protective film for the visual display device process can... Figure 4 The area shown presents a strip or bar shape.

[0097] like Figure 3 As shown, the protective film for the visual display device process can be attached to the surface of the object to protect it. The object can be an organic light-emitting device, which may sequentially include a backplane, a plastic substrate, a thin-film transistor, an organic light-emitting diode, and an encapsulation layer. The protective film for the visual display device process can be attached to the top of the OLED panel during the OLED panel manufacturing process to prevent damage to the panel.

[0098] (Example) Example 1 Using a polyurethane resin (manufactured by Sanwa Coatings, SERATER UA10) with a weight-average molecular weight of 80,000 g / mol as the main resin, 66.35 parts by weight of the polyurethane resin were prepared based on the solid content of 100 parts by weight of the adhesive composition. Furthermore, the adhesive composition, relative to 100 parts by weight of the solid component of the polyurethane resin, comprises 0.57 parts by weight of silicone modified polyacrylate (INNO F&C, SD37S), 7.58 parts by weight of hexamethylene diisocyanate trimer (HDITrimer) as a curing agent, 34.85 parts by weight of triethylene glycol bis(2-ethylhexanoate) as a plasticizer, 0.15 parts by weight of lithium bis(trifluoromethanesulfonyl)imide (INNO F&C, AS10F) as an antistatic agent, and 7.58 parts by weight of acetylacetone as a curing delay agent.

[0099] A 75 μm thick polyethylene terephthalate (PET) film is prepared as the substrate layer, on the other side of which is treated with an antistatic coating of a conductive polymer. A release film is prepared as the release layer, on both sides of a 50 μm thick polyethylene terephthalate (PET) film, treated with an antistatic coating and on the side in contact with the adhesive layer treated with silicone.

[0100] The adhesive composition is applied to one side of the substrate layer on a coating machine and dried at 120°C for 5 minutes to form an urethane adhesive layer (thickness: 75 μm).

[0101] The release film was laminated onto one side of the urethane adhesive layer using a 2kg manual laminator and aged at 50°C for 2 days to prepare a protective film for the visual display device process.

[0102] Examples 2-5 and Comparative Examples 1-6 In Example 1, the protective films for the visual display device process of Examples 2-5 and Comparative Examples 1-6 were prepared by changing the contents of silicone-modified polyacrylate and plasticizer as shown in Table 1.

[0103] In this case, Comparative Example 5 used isopropyl myristate (IPM) instead of plasticizer, and Comparative Example 6 used isopropyl palmitate (IPP) instead of plasticizer.

[0104] Table 1

[0105] evaluate Experimental Example 1: Peeling Force (gf / in) The protective films of the aforementioned embodiments and comparative examples were cut into 25 mm (width) × 240 mm (length) pieces to prepare samples. Furthermore, the release layer was removed from the protective film, and an adhesive layer was attached to the glass. The samples with the adhesive layer attached were stored at room temperature (23°C) for 24 hours. Moreover, UTM was used at 180... The peeling force was determined by peeling the sample at a peeling angle of 5 mm / s and a peeling speed of 5 mm / s.

[0106] Furthermore, the glass was replaced with acrylic (Acryl) plates, silicon nitride (SiNx) plates, and silicon oxide (SiOx) plates, and the peel strength was measured respectively. The results are shown in Table 2 below.

[0107] Experimental Example 2: Water Contact Angle ( ） The contact angles of each urethane adhesive layer in the examples and comparative examples were measured using deionized water as the sample. The measurement conditions were as follows: 10 μL of sample was dropped onto the urethane adhesive layer at 23°C and 55% RH, and the contact angle was measured 10 seconds later. The contact angles were measured using the droplet method with a contact angle meter (SEO Ltd., Model Phoenix-150). In the droplet method, a droplet was dropped onto the urethane adhesive layer, and the shape of the dropped layer was photographed from the side using an optical camera mounted on the device. The angle formed by the droplet and the sample surface was then used as the contact angle for measurement.

[0108] Experimental Example 3: Surface Energy (mN / m) The surface energy of each urethane adhesive layer in the examples and comparative examples was determined using the Owens-Wendt method. The Owens-Wendt method measures the contact angle (θ) when a liquid (L) as a sample is dropped onto the surface of a solid (S) as the test object, i.e., each urethane adhesive layer in the examples and comparative examples, and calculates the surface energy (γ) of the solid (S) as the test object. SThe method is as follows: Surface energy (γ) is calculated based on the following formula. S ).

[0109] Mathematical formula 1:

[0110] γ L Surface energy of liquid (sample) γ L d Component of liquid dispersion force γ S d Solid dispersion force component γ L h Components of nondispersive forces in liquids γ S h Solid nondispersive force components Mathematical formula 2: γ S =γ S d +γ S h γ S Surface energy of a solid (sample) In used to determine surface energy (γ) S ) of γ S d and γ S h In the calculation, γ L γ L d γ L h The contact angles of the two liquids used as the basis for the committee's assessment were determined and calculated based on the aforementioned mathematical formula 1. In this invention, the two suitable liquids as samples are a combination of a solvent with a larger polar component and a solvent with a smaller polar component. Specifically, they may include water (γ-ray diffusive precipitate). L (W), γ L (W) d =21.8 mN / m, γ L (W) h =51 mN / m) and diiodomethane (γ L (M), γ L (M) d =48.5 mN / m, γ L (M) h =2.3mN / m). These two solvents are γ, which has a relatively large polar component. L h polar solvents and those with smaller γ Lh The combination of nonpolar solvents is suitable for the samples used in this invention. Furthermore, γ is calculated by solving the following simultaneous equations. S d γ S h Their sum is the surface energy (γ) of the adhesive layer. s ).

[0111] Mathematical formula 3:

[0112] Experiment Example 4: Pencil Scratch Test (Does it produce foreign matter?) The protective films of the examples and comparative examples were cut into 5cm (width) × 5cm (length) sizes to prepare samples. The substrate layer was then attached to a glass plate using double-sided tape. The urethane adhesive layer of the examples and comparative examples was placed face up and then fixed to the lower plate of a UTM (SurTA) device. The shape of the urethane adhesive layer was then confirmed after scraping it for 15 seconds at a speed of 1mm / sec with a 1mm diameter SUS pen under applied load (100g, 500g).

[0113] If each urethane adhesive layer is as follows Figure 4 If the shape shown forms a band or strip, it is marked as "OK". Figure 5 As shown, if the adhesive breaks or produces loose particles, it is marked as "NG".

[0114] Experimental Example 4: Residual Adhesion Rate (%) The adhesion of nitto 31B tape to the glass surface is taken as the standard (ref.) adhesion (A).

[0115] Furthermore, the residual adhesion rate of the adhesive layer in the embodiments and comparative examples was calculated according to Formula 1 below. The results are shown in Table 2. In this case, a residual adhesion rate of 100% means that there is no adhesive layer residue.

[0116] Formula 1: Residual adhesion rate = (Adhesion force B / Adhesion force A) × 100 In Formula 1, the adhesion force A (ref.) represents the adhesion force after applying nitto 31B tape to a glass surface and leaving it at 23°C for 24 hours, followed by a 180°C test. The adhesive strength was measured by peeling the nitto 31B tape from the glass at a peel angle, a peel length of 120 mm, and a speed of 5 mm / s. The adhesion force B refers to the application of the adhesive layer of the embodiments and comparative examples to the glass surface, followed by removal after being placed at 23°C for 24 hours, then application of Nitto 31B tape to the area where the adhesive layer was removed, and placement at 23°C for 24 hours, followed by application at 180°C. The adhesive strength was measured by peeling the nitto 31B tape from the glass at a peel angle, a peel length of 120 mm, and a speed of 5 mm / s.

[0117] Table 2

[0118] As described above, the present invention has been illustrated, but it is obvious that the present invention is not limited to the embodiments disclosed in this specification, and those skilled in the art can make various modifications within the scope of the technical concept of the present invention. Moreover, even if the effects of the structure according to the present invention are not explicitly described in the description of the embodiments of the present invention, the predictable effects of this structure should be acknowledged.

Claims

1. A protective film for use in the manufacturing process of a visual display device, characterized in that, Includes a substrate layer and a urethane adhesive layer. The urethane adhesive layer is a cured product of a composition comprising a polyurethane base resin, a plasticizer, and a silicone-modified polyacrylate. And it meets the following conditions (1) and (2): Condition (1): The surface energy of the urethane adhesive layer is 18.7 mN / m to 38.5 mN / m. Condition (2): The residual adhesion rate of the urethane adhesive layer according to Formula 1 below is 90% or more. Formula 1: Residual adhesion rate = (Adhesion force B / Adhesion force A) × 100 In Equation 1 above, the adhesion force A is the result of attaching Nitto 31B tape to a glass surface and leaving it at room temperature for 24 hours, then applying it at 180°C. The adhesive strength was measured by peeling the nitto 31B tape from the glass at a peel angle, a peel length of 120 mm, and a speed of 5 mm / s. Adhesion force B is determined by applying the urethane adhesive layer to the glass surface and leaving it at room temperature for 24 hours, then removing it. Next, nitto 31B tape is applied to the area where the urethane adhesive layer was removed and left at room temperature for 24 hours. Then, 180... The adhesive strength was measured by peeling the nitto 31B tape from the glass at a peel angle, a peel length of 120 mm, and a speed of 5 mm / s.

2. The protective film for the visual display device process according to claim 1, characterized in that, The following condition (3) must be met: Condition (3): The urethane adhesive layer is attached to the glass and left at room temperature for 24 hours, then at 180°C. The peeling force when peeling the protective film from the glass at a peeling angle of 5 mm / s and a peeling speed of 5 mm / s is 1 to 3 gf / in.

3. The protective film for the visual display device process according to claim 1, characterized in that, The following condition (4) must be met: Condition (4): Attach the urethane adhesive layer to the acrylic sheet and leave it at room temperature for 24 hours, then heat it at 180°C. The peeling force when peeling the protective film from the acrylic plate at a peeling angle of 5 mm / s is 1 to 3 gf / in.

4. The protective film for the visual display device process according to claim 1, characterized in that, In the composition, the content of the silicone-modified polyacrylate is from 0.19 parts by weight to 0.6 parts by weight relative to 100 parts by weight of the polyurethane main resin solids.

5. The protective film for the visual display device process according to claim 1, characterized in that, In the composition, the plasticizer content is from 10 parts by weight to 35 parts by weight relative to 100 parts by weight of the polyurethane main resin solids.

6. The protective film for the visual display device process according to claim 1, characterized in that, The plasticizer is a compound containing two or more ester groups.

7. The protective film for the visual display device process according to claim 1, characterized in that, The plasticizers include triethylene glycol bis(2-ethylhexanoate), tributyl acetyl citrate, or combinations thereof.

8. The protective film for the visual display device process according to claim 1, characterized in that, It includes an antistatic coating disposed on the other side of the substrate layer where the adhesive layer is not disposed.

9. The protective film for the process of a visual display device according to claim 1, characterized in that, It also includes a release layer disposed on the other side of the adhesive layer where no substrate layer is formed.

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