Adhesive protective film, optical component, and optical display device

Abstract

This invention provides an adhesive protective film that exhibits high adhesion under high temperature and high humidity conditions to polyimide-based optical elements, including polyimide-based ash. [Solution] An adhesive protective film for a polyimide optical element containing polyimide ash, wherein the adhesive protective film comprises a cured product of a composition containing a (meth)acrylic copolymer, a curing agent, a (meth)acrylic oligomer, and a monofunctional or more (meth)acrylic monomer containing an aromatic group, the adhesive protective film has a storage modulus of 0.1 MPa or less at -20°C, the adhesive protective film has a peel strength of 350 gf / inch or more at 60°C and 93% relative humidity for a polyimide optical element containing polyimide ash, and the adhesive protective film has a creep of 40% or less at 60°C.

Description

Technical Field

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

Background Art

[0002] In conventional devices such as optical members and electronic members, in order to prevent scratches on the surface of the device during processes such as processing, assembly, and inspection, an adhesive layer or a protective film composed of a base film and an adhesive layer may be attached to the surface of the device. Such a protective film is used after removing the release film that protects the adhesive layer. In recent years, as an optical member, there has been an active movement from liquid crystal devices to organic light-emitting diode (OLED) devices. In addition, the number of OLED devices having flexible characteristics has been increasing.

[0003] Flexible OLED devices are very flexible, unlike liquid crystal devices and ordinary OLED devices. Therefore, flexible OLED devices require a process protection film for protecting the surface and the OLED panel during processes such as processing, assembly, and inspection. When there are defects such as appearance abnormalities and foreign matters during panel inspection, low peel strength and re-work characteristics are required to easily remove the protective film. After the inspection, a P-film (patterned film) that is permanently attached to support the panel and protect the panel from moisture and the external environment is required. Since the P-film must be permanently attached to the panel, high peel strength and reliability are required.

[0004] Therefore, in the conventional panel manufacturing process, a process protection film with low peel strength that is temporarily used and a P-film that requires high peel strength are needed, so a process protection film lamination process, a process protection film peeling process, and a P-film lamination process are required.

[0005] In recent years, efforts have been made to reduce costs and optimize processes. In particular, when a process protective film is used before UV irradiation, this protective film is patterned using a laser. At this time, if the initial peel strength to the polyimide substrate exceeds a certain level, there is a risk that the success rate of peeling will decrease, leading to a decrease in yield. Therefore, when laminating to a polyimide substrate, an adhesive protective film that can integrate a process protective film and a P-film that exhibits high peel strength after UV irradiation, while having low peel strength initially, may be preferable.

[0006] The background art of this invention is disclosed in Japanese Patent No. 5683369, etc. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5683369 specification [Overview of the project] [Problems that the invention aims to solve]

[0008] The object of the present invention is to provide an adhesive protective film that exhibits high adhesion to polyimide-based optical elements containing polyimide-based ash, even under high temperature and high humidity conditions.

[0009] Another object of the present invention is to provide an adhesive protective film with excellent folding properties.

[0010] Another object of the present invention is to provide an adhesive protective film that exhibits good wettability for polyimide-based optical elements, including polyimide-based ash. [Means for solving the problem]

[0011] One aspect of the present invention is an adhesive protective film for polyimide optical elements containing polyimide ash.

[0012] The adhesive protective film comprises a cured product of a composition containing a (meth)acrylic copolymer, a curing agent, a (meth)acrylic oligomer, and a monofunctional (meth)acrylic monomer containing an aromatic group, wherein the adhesive protective film has a storage modulus of 0.1 MPa or less at -20°C, a peel strength of 350 gf / inch or more at 60°C and 93% RH (relative humidity) against a polyimide optical element containing polyimide ash, and a creep of 40% or less at 60°C.

[0013] Another aspect of the present invention is an optical component.

[0014] The optical component includes a polyimide optical element containing polyimide ash on at least one surface, and an adhesive layer bonded to the surface containing the polyimide ash, the adhesive layer including the adhesive protective film.

[0015] Another aspect of the present invention is an optical display device.

[0016] The optical display device includes a cured product of the adhesive protective film or the optical member. [Effects of the Invention]

[0017] The present invention can provide an adhesive protective film that exhibits high peel strength under high temperature and high humidity conditions for polyimide-based optical elements containing polyimide-based ash.

[0018] This invention can provide an adhesive protective film with excellent folding properties.

[0019] The present invention can provide an adhesive protective film that exhibits good wettability for polyimide-based optical elements, including polyimide-based ash. [Brief explanation of the drawing]

[0020] [Figure 1]An embodiment of a method for manufacturing a polyimide resin layer containing polyimide ash will be described. [Figure 2] An embodiment of a method for manufacturing a polyimide resin layer containing polyimide ash will be described. [Figure 3] It is a schematic diagram of a laser irradiation process during the manufacturing process of a polyimide resin layer containing polyimide ash. [Figure 4] It is a cross-sectional view of an optical member according to an embodiment. [Figure 5] It is a schematic diagram for evaluating the bubble reproduction ratio. [Figure 6] It is the evaluation result of the bubble reproduction ratio.

Embodiments for Carrying Out the Invention

[0021] The present invention will be described in detail by the attached embodiments so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement it. The present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0022] The terms used herein are for illustrative purposes only to describe exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0023] As used herein, “(meth)acrylic” means acrylic and / or methacrylic.

[0024] As used herein, “copolymer” can include polymers or resins.

[0025] In this specification, "glass transition temperature" may refer to the glass transition temperature (Tg) measured for the monomer under test using TA Instrument's DSC Discovery. Specifically, the temperature of the homopolymer of the monomer under test can be raised to 180°C at a rate of 20°C / min, then gradually cooled to -100°C, and then heated again to 100°C at a rate of 10°C / min. After obtaining data for the endothermic transition curve, the inflection point of the endothermic transition curve can be determined as the glass transition temperature.

[0026] In this specification, when a numerical range is described, "X~Y" means "X or greater and Y or less" (X ≤ and ≤Y).

[0027] According to one embodiment of the present invention, the adhesive protective film has a peel hardness of 350 gf / inch or more at 60°C and 93% RH (relative humidity) against a polyimide optical element containing polyimide ash, a storage modulus of 0.1 MPa or less at -20°C, and creep of 40% or less at 60°C.

[0028] "Polyimide-based optical elements" are polymer films manufactured by the polymerization reaction of polyamic acid precursors, containing imide groups and aromatic groups within repeating units. They possess excellent mechanical and heat-resistant properties and can be used as substrates for flexible OLED panels.

[0029] In one embodiment, the polyimide optical element may have the form of a polyimide resin layer.

[0030] First, we will explain how to manufacture a polyimide resin layer that includes a surface containing polyimide ash.

[0031] Figure 1 illustrates an example of a method for manufacturing a polyimide resin layer containing polyimide ash.

[0032] Referring to Figure 1, (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 11.

[0033] (2) The polyimide varnish coating 11 is dried and cured to form a polyimide resin layer 12 on the lower surface of the glass plate 10.

[0034] (3) A laser is irradiated from the upper side of the glass plate 10 using the laser irradiation device 13 to form polyimide ash 14 on the upper surface of the polyimide resin layer 12.

[0035] Laser irradiation can form polyimide ash by burning a portion of the polyimide resin layer. The polyimide ash can form a fine step between the laser-treated and untreated areas as irregular and fine irregularities in the form of dust. This step allows the glass plate to be easily peeled off in step (4) below. The extent to which polyimide ash 14 is formed, or the area ratio of polyimide ash 14 (the ratio of the total area of ​​polyimide ash to the total area of ​​the polyimide resin layer), can be adjusted by the type of polyimide varnish, the overall thickness of the polyimide resin layer, the degree of laser irradiation, etc.

[0036] (4) The glass plate 10 can be peeled off from the polyimide resin layer 12 to produce a polyimide resin layer 15 having a surface containing polyimide ash 14.

[0037] Figure 2 illustrates another example of a method for manufacturing a polyimide resin layer containing polyimide ash.

[0038] Referring to Figure 2, (1) a polyimide varnish is applied to the upper surface of the release substrate film 16 to a predetermined thickness to form a polyimide varnish coating 11.

[0039] (2) The polyimide varnish coating 11 is dried and cured to form a polyimide resin layer 12 on the upper surface of the release substrate film 16.

[0040] (3) The upper surface of the polyimide resin layer 12 is covered with a glass plate 10.

[0041] (4) A laser is irradiated from the upper side of the glass plate 10 using a laser irradiation device 13 to form polyimide ash 14 on the upper surface of the polyimide resin layer 12. The laser treatment can form polyimide ash by burning a portion of the polyimide resin layer. The polyimide ash can form a fine step between the laser-treated and untreated parts as irregular and fine irregularities in the form of dust. This step allows the glass plate to be easily peeled off in step (5) below. The extent to which polyimide ash 14 is formed, or the area ratio of polyimide ash 14 (the ratio of the total area of ​​polyimide ash to the total area of ​​the polyimide resin layer), can be adjusted by the type of polyimide varnish, the overall thickness of the polyimide resin layer, the degree of laser irradiation, etc.

[0042] (5) The glass plate 10 can be peeled off from the polyimide resin layer 12 to produce a laminate of a polyimide resin layer 15 having a surface containing polyimide ash 14 and a release substrate film 16.

[0043] The release substrate film 16 can be easily removed because it has been treated with a release agent such as silicone.

[0044] Figure 3 is a schematic diagram of the laser irradiation process during the manufacturing process of a polyimide resin layer containing polyimide ash.

[0045] Referring to Figure 3, a laminate is prepared in which a polyimide resin layer 12 and a glass plate 10 are sequentially laminated on the upper surface of a release substrate film 16. A laser 18 is irradiated from a laser irradiation device 17 located above the glass plate 10 in the laminate, thereby forming polyimide ash 14 on the upper surface of the polyimide resin layer 12. The laminate is moved in a certain direction (arrow direction), and by adjusting the on-off (on-off) of the laser irradiation, polyimide ash 14 can be formed discontinuously on the upper surface of the polyimide resin layer 12.

[0046] The glass plate is alkali-free glass, and its thickness can be 1 mm to 2 mm.

[0047] Polyimide varnishes may contain 90% by weight or more of one or more selected from polyimide copolymers, polyimide oligomers, and polyimide monomers, but are not limited to these. For example, polyimide varnishes such as SD Flex (DuPont) can be used, but are not limited to these.

[0048] Polyimide varnishes can be applied by conventional methods known to those skilled in the art. For example, polyimide varnishes 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.

[0049] A polyimide varnish coating can dry and harden to form a polyimide resin layer.

[0050] This drying may include a heat treatment at 50°C to 200°C for 5 to 60 minutes. Drying may include one or more heat treatments, for example, two or more. In one example, drying may include two or more heat treatments. For example, drying may include a primary heat treatment at 50°C to 100°C for 5 to 30 minutes, and a secondary heat treatment at 100°C to 200°C for 5 to 30 minutes. Preferably, the primary heat treatment may be performed at 80°C for 10 minutes, and the secondary heat treatment at 120°C for 20 minutes.

[0051] The dried polyimide varnish coating can have a thickness of 20 μm to 30 μm, preferably 20 μm.

[0052] Furthermore, curing may include heat treatment at a relatively higher temperature and for a relatively longer time compared to the drying described above. Such heat treatment can form a polyimide resin layer by causing an imidation reaction in the dried polyimide varnish coating. The heat treatment may include heat treatment at a temperature above 200°C and below 400°C for 30 to 120 minutes. In one example, the heat treatment may be performed one or more times. Preferably, curing may include heat treatment at 250°C for 60 minutes.

[0053] The polyimide resin layer can have a thickness of 20 μm to 30 μm, preferably 20 μm.

[0054] The laser irradiation is 100 mJ / cm². 2 ~500 mJ / cm 2 For example, 150 mJ / cm² 2 ~200 mJ / cm 2 This can be done with the irradiation dose. Within the above range, polyimide ash that is easily peeled from the glass plate can be formed. Laser irradiation includes light irradiation in the wavelength region of 308 nm and can include picosecond, nanosecond, or femtosecond irradiation.

[0055] The adhesive protective film has a peel strength of 350 gf / inch or more at 60°C and 93% RH() against polyimide optical elements containing polyimide ash, thus easily providing excellent folding properties when the adhesive protective film is bonded to polyimide optical elements containing polyimide ash. For example, the peel strength may be between 350 gf / inch and 600 gf / inch.

[0056] The adhesive protective film has a storage modulus of 0.1 MPa or less at -20°C. Within this range, when the adhesive protective film is bonded to a polyimide optical element containing polyimide ash, excellent folding can be easily provided. For example, the storage modulus may be 0.03 MPa to 0.1 MPa.

[0057] The adhesive protective film has a creep of 40% or less at 60°C. Within this range, when the adhesive protective film is bonded to a polyimide optical element containing polyimide ash, excellent folding can be easily provided. For example, the creep of the adhesive protective film may be between 15% and 40%.

[0058] The adhesive protective film has a simulated bubble fraction of 3.5% or less. Within this range, it may be easier to provide good wettability when the adhesive protective film is bonded to a polyimide optical element containing polyimide ash.

[0059] To achieve the above-mentioned peel strength, elastic modulus, creep, and pseudo-bubble rate, the adhesive protective film comprises a cured product of a composition containing a (meth)acrylic copolymer, a curing agent, a (meth)acrylic oligomer, and one or more monofunctional (meth)acrylic monomers containing aromatic groups.

[0060] In one example, the adhesive protective film may contain a (meth)acrylic copolymer, a curing agent, a (meth)acrylic oligomer, and one or more (meth)acrylic monomers containing aromatic groups. These components may be derived from the above-described compositions.

[0061] In one example, the cured product described above may be a thermosetting product.

[0062] The components of the composition are described in detail below.

[0063] (meth)acrylic copolymer The (meth)acrylic copolymer forms the matrix of the adhesive protective film, and curing it with an isocyanate-based curing agent can facilitate the provision of the initial peel strength of the aforementioned adhesive protective film.

[0064] (Meth)acrylic copolymers may have a glass transition temperature (Tg) of -10°C or lower, specifically -80°C to -20°C. Within this range, they can be useful in providing wettability (adhesion) to polyimide optical elements and initial peel strength of adhesive protective films.

[0065] (Meth)acrylic copolymers can be copolymers of monomer mixtures containing (meth)acrylic monomers having a homopolymer glass transition temperature of 60°C or less, and (meth)acrylic monomers having crosslinkable functional groups such as hydroxyl group-containing (meth)acrylic monomers.

[0066] In one example, the total amount of (meth)acrylic monomers having a homopolymer glass transition temperature of 60°C or less, and (meth)acrylic monomers having a crosslinkable functional group, can be 95% by weight or more, for example, 99% to 100% by weight, or 100% by weight, in the monomer mixture.

[0067] For example, a (meth)acrylic monomer whose homopolymer glass transition temperature is 60°C or lower may have a homopolymer glass transition temperature of -80°C to 60°C. Within this range, the effects of the adhesive protective film described above can be easily achieved.

[0068] (Meth)acrylic monomers having a homopolymer glass transition temperature of 60°C or less can be included in the monomer mixture in amounts of 80% by weight or more, for example, 80% to 99% by weight, for example, 80% to 95% by weight, or 85% to 99% by weight.

[0069] A (meth)acrylic monomer having a homopolymer glass transition temperature of 60°C or less may be a mixture of two or more (meth)acrylic monomers having homopolymer glass transition temperatures that differ from each other.

[0070] In one example, a (meth)acrylic monomer having a homopolymer glass transition temperature of 60°C or less may be a mixture of a (meth)acrylic monomer (referred to as the first monomer for convenience) having a homopolymer glass transition temperature of -80°C to -20°C, for example -70°C to -55°C, and a (meth)acrylic monomer (referred to as the second monomer for convenience) having a homopolymer glass transition temperature of -80°C to -20°C, for example -60°C to -40°C.

[0071] For example, as a (meth)acrylic monomer whose homopolymer glass transition temperature is 60°C or lower, a mixture of (meth)acrylic acid esters having a linear alkyl group with 1 to 20 carbon atoms and a branched alkyl group with 1 to 20 carbon atoms can be used.

[0072] In one example, the linear (meth)acrylic acid ester having a C1-C20 alkyl group and the branched (meth)acrylic acid ester having a C1-C20 alkyl group can be selected from the above-mentioned list of (meth)acrylic acid esters having a C1-C20 alkyl group. For example, the linear (meth)acrylic acid ester having a C1-C20 alkyl group may be n-propyl (meth)acrylate, n-butyl (meth)acrylate, etc. The branched (meth)acrylic acid ester having a C1-C20 alkyl group may be 2-ethylhexyl (meth)acrylate, etc.

[0073] In one example, the (meth)acrylic acid ester having a linear alkyl group with 1 to 20 carbon atoms may be present in 5% to 50% by weight of the monomer mixture, for example, 5% to 45% or 10% to 40% by weight. The (meth)acrylic acid ester having a branched alkyl group with 1 to 20 carbon atoms may be present in 50% to 90% by weight of the monomer mixture, for example, 50% to 80% by weight. Within these ranges, the effect of the adhesive film may be easily achieved.

[0074] A hydroxyl group-containing (meth)acrylic monomer may be a (meth)acrylate containing one or more hydroxyl groups. For example, a hydroxyl group-containing (meth)acrylate may be at least one selected from 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, trimethylolpropanedi(meth)acrylate, trimethylolethanedi(meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, 4-hydroxycyclopentyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, and cyclohexanedimethanol mono(meth)acrylate.

[0075] The hydroxyl group-containing (meth)acrylic monomer can be present in the monomer mixture in an amount of 0.1% to 20% by weight, specifically 1% to 20% by weight, 5% to 20% by weight, or 0.5% to 15% by weight. Within this range, it is possible to impart cohesive force to the adhesive layer, thereby forming an adhesive layer and effectively providing initial peel strength for the adhesive protective film.

[0076] In one example, the monomer mixture may not contain monomers having aromatic groups. A tacky protective film made from a (meth)acrylic copolymer formed from monomers having aromatic groups may have difficulty achieving the effects of the tacky protective film described above.

[0077] In one example, the total amount of alkyl group-containing (meth)acrylic acid esters and hydroxyl group-containing (meth)acrylic monomers in the monomer mixture may be 99% by weight or more, for example, 99% to 100% by weight, or 100% by weight.

[0078] (Meth)acrylic copolymers can be produced by polymerizing monomer mixtures using conventional polymerization methods. These polymerization methods may include conventional methods known to those skilled in the art. For example, (meth)acrylic copolymers can be produced by conventional copolymer polymerization, such as suspension polymerization, emulsion polymerization, or solution polymerization, after adding an initiator to the monomer mixture. The polymerization temperature may be 60°C to 70°C, and the polymerization time may be 4 to 8 hours. Conventional initiators can be used, including azo polymerization initiators and / or peroxides such as benzoyl peroxide or acetyl peroxide.

[0079] (Meth)acrylic oligomers (Meth)acrylic oligomers have a glass transition temperature of 60°C or less and a weight-average molecular weight of 100,000 g / mol or less. Within the range of glass transition temperature and weight-average molecular weight, they can provide excellent folding properties under room temperature and high-temperature, high-humidity conditions.

[0080] For example, (meth)acrylic oligomers may have a glass transition temperature of -10°C to 60°C or 0°C to 30°C. For example, (meth)acrylic oligomers may have a weight-average molecular weight of 10,000 g / mol to 100,000 g / mol, for example, 20,000 g / mol to 50,000 g / mol.

[0081] (Meth)acrylic oligomers can be produced by selecting a portion of known monomers to provide the aforementioned glass transition temperature and weight-average molecular weight.

[0082] In one example, the monomer mixture may include (meth)acrylic monomers having hydroxyl groups.

[0083] A hydroxyl group-containing (meth)acrylic monomer may include one or more (meth)acrylic monomers having a hydroxyl group-containing C1-C20 alkyl group, a hydroxyl group-containing cycloalkyl group, and a hydroxyl group-containing aromatic group having C6-C20. Specifically, a hydroxyl group-containing (meth)acrylic monomer is a hydroxyl group-containing (meth)acrylic monomer having a hydroxyl group-containing C1-C20 alkyl group, and may include one or more of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. These may be included individually or in combination of two or more.

[0084] The (meth)acrylic monomer having a hydroxyl group may be present in an amount of 2% to 5% by weight of the monomer mixture, for example, more than 2% but less than or equal to 5% by weight. Within this range, the effects of the adhesive film of the present invention can be easily realized.

[0085] The monomer mixture may further contain (meth)acrylic monomers having alkyl groups, in addition to (meth)acrylic monomers having hydroxyl groups.

[0086] (Meth)acrylic monomers having alkyl groups can be (meth)acrylic acid esters having linear or branched alkyl groups with 1 to 20 carbon atoms in the ester moiety. Specifically, (meth)acrylic acid esters may contain one or more of the following: butyl (meth)acrylates such as n-butyl (meth)acrylate, pentyl (meth)acrylates such as n-pentyl (meth)acrylate, hexyl (meth)acrylates such as n-hexyl (meth)acrylate, heptyl (meth)acrylates such as n-heptyl (meth)acrylate, octyl (meth)acrylates such as n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylates such as n-nonyl (meth)acrylate, and decyl (meth)acrylates such as n-decyl (meth)acrylate.

[0087] (Meth)acrylic monomers having alkyl groups can be included in the monomer mixture at an amount of 40% to 60% by weight. Within this range, the adhesive film can be provided with sufficient peel strength and an appropriate modulus of elasticity.

[0088] The monomer mixture may further include (meth)acrylic monomers having hydroxyl groups and (meth)acrylic monomers having alkyl groups, as well as comonomers copolymerizable with these.

[0089] In one example, a (meth)acrylic oligomer can be produced by polymerizing a monomer mixture using a conventional polymerization method. The polymerization method may include conventional methods known to those skilled in the art. For example, a (meth)acrylic oligomer can be produced by conventional copolymer polymerization, such as suspension polymerization, emulsion polymerization, or solution polymerization, after adding an initiator to the monomer mixture. The polymerization temperature may be 65°C to 70°C, and the polymerization time may be 6 to 8 hours. Conventional initiators can be used, including azo polymerization initiators and / or peroxides such as benzoyl peroxide or acetyl peroxide.

[0090] The (meth)acrylic oligomer may be included in an amount of 0.1 to 3 parts by weight, for example, 0.5 to 2 parts by weight or 0.5 to 1 part by weight, per 100 parts by weight of the (meth)acrylic copolymer. Within this range, the effects of the adhesive film described above can be easily achieved.

[0091] (Meth)acrylic monomers containing one or more aromatic groups A (meth)acrylic monomer containing one or more aromatic groups has one or more functional groups that can react with an aromatic group and an initiator. "Aromatic" can mean a monocyclic or heterocyclic functional group having 6 to 50 carbon atoms. For example, aromatic can mean substituted or unsubstituted benzyl, phenyl, biphenylyl, terphenylyl, naphthyl, etc. Also, "functional group" may mean a vinyl group or a (meth)acrylate group.

[0092] Aromatic group-containing monofunctional or more (meth)acrylic monomers, by containing aromatic groups, can enhance the adhesion between the adhesive layer of the adhesive protective film and the polyimide film through a stacking effect via π-π bonding with the adherend, such as a plastic film having aromatic groups, specifically a polyimide film, thereby contributing to an improvement in the adhesive strength of the adhesive protective film to the adherend.

[0093] (Meth)acrylic monomers containing one or more aromatic groups can increase the cohesive force and / or elastic modulus of adhesive protective films.

[0094] It is preferable that the glass transition temperature of the homopolymer of a monofunctional or greater aromatic group-containing (meth)acrylic monomer is within a predetermined range relative to the glass transition temperature of the (meth)acrylic copolymer. This suppresses shrinkage of the adhesive protective film even after curing, thereby increasing the peel strength.

[0095] The glass transition temperature of homopolymers of (meth)acrylic monomers containing one or more aromatic groups is higher than that of (meth)acrylic copolymers, with a difference of 20°C or more, preferably 20°C to 120°C or 40°C to 100°C. Within this range, good wettability to polyimide optical elements can be provided.

[0096] Aromatic group-containing monofunctional (meth)acrylic monomers may have a homopolymer glass transition temperature of -30°C or higher, for example, -30°C to 50°C. Within this range, the glass transition temperature is higher than that of (meth)acrylic copolymers, and an effect of improving the peel strength of adhesive protective films due to improved cohesive force can be obtained.

[0097] A (meth)acrylic monomer containing one or more aromatic groups may include, but is not limited to, the compound of the following chemical formula 1. [ka] ...(chemical formula 1)

[0098] In chemical formula 1, R 1 is a hydrogen or methyl group, s is an integer from 0 to 10, and 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, and 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.

[0099] In this specification, "substituted or unsubstituted" means that one or more hydrogen atoms are substituted with a C1-C10 alkyl group, a C1-C10 thioalkyl group, a C1-C10 alkoxy group, a halogen (F, Cl, Br or I), a C3-C10 cycloalkyl group, or a C6-C20 aryl group.

[0100] Specifically, R 2These may be substituted or unsubstituted phenoxy groups, benzyl groups, phenyl groups, biphenylyl groups, terphenylyl groups, naphthyl groups, etc.Specifically, aromatic group-containing monofunctional (meth)acrylic monomers include phenoxy(meth)acrylate, phenoxybenzyl(meth)acrylate, phenoxypolyethylene glycol(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, and 2-(2-methylphenyl)ethyl(meth)acrylate. Nyl(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, 2-(4-bromophenyl)ethyl (meth)acrylate, 2-(3-phenylphenyl)ethyl (meth)acrylate, orthobiphenyl (meth)acrylate, metabiphenyl (meth)acrylate, parabiphenyl (meth)acrylate, 2,6-terphenyl (meth)acrylate, orthoterphenyl (meth)acrylate, metaterphenyl (meth)acrylate, paraterphenyl (meth)acrylate, 4-(4-methylphenyl)phenyl ( It may contain one or more of the following: meth)acrylate, 4-(2-methylphenyl)phenyl(meth)acrylate, 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 individually or as a mixture of two or more.

[0101] Preferably, the (meth)acrylic monomer containing one or more aromatic groups may include one or more of phenoxybenzyl (meth)acrylate and phenoxypolyethylene glycol (meth)acrylate.

[0102] The aromatic group-containing (meth)acrylic monomer can be included in amounts exceeding 0 parts by weight but not exceeding 10 parts by weight per 100 parts by weight of the (meth)acrylic copolymer, for example, 0.1 parts by weight to 10 parts by weight, 1 part by weight to 5 parts by weight, or 1 part by weight to 3 parts by weight. Within the above range, the aromatic group-containing (meth)acrylic monomer can contribute to increasing the peel strength of the adhesive protective film and can suppress the shrinkage of the adhesive protective film.

[0103] Thermosetting agent The thermosetting agent can cure (meth)acrylic copolymers and (meth)acrylic oligomers, facilitate the formation of the matrix of the adhesive film, and increase the peel strength of the adhesive film.

[0104] The thermosetting agent may contain one or more of the following: isocyanate-based curing agents, metal chelating curing agents, epoxy-based curing agents, amine-based curing agents, and aziridine-based curing agents.

[0105] The isocyanate curing agent may include a bifunctional to hexafunctional isocyanate curing agent. Specifically, the isocyanate curing agent may include one or more aromatic isocyanate curing agents such as toluene diisocyanate, xylylene diisocyanate, halogen-substituted toluene diisocyanate, phenylene diisocyanate including m-phenylene diisocyanate, and tetramethyl-xylylene diisocyanate, one or more aliphatic isocyanate curing agents such as hexamethylene diisocyanate and pentamethylene diisocyanate, alicyclic isocyanate curing agents such as cyclohexamethylene diisocyanate, or adducts thereof, such as one or more adducts of a polyol such as trimethylolpropane (TMP) and the above-mentioned curing agents.

[0106] A metal chelating curing agent is a crosslinking agent composed of a metal and chelate bonds, and may include metal chelating crosslinking agents commonly used by those skilled in the art. In one example, a metal chelating crosslinking agent may include a crosslinking agent having two or more chelate bonds with the metal, for example, three to six. For example, the metal may include aluminum, zirconium, titanium, cobalt, preferably aluminum. For example, the chelate may include, but is not limited to, acetylacetonate, ethyl acetoacetate, etc. Specifically, a metal chelating crosslinking agent may include, but is not limited to, one or more of acetylacetonate aluminate, aluminum tris(acetylacetonate), aluminum tris(ethyl acetoacetate), aluminum bis(acetoacetate), zirconium tris(acetylacetonate), and cobalt tris(acetylacetonate).

[0107] The thermosetting agent may be included in an amount of 0.01 to 1 part by weight per 100 parts by weight of (meth)acrylic copolymer, for example, 0.01 to 0.5 parts by weight, 0.01 to 0.3 parts by weight, or 0.2 to 0.3 parts by weight. Within this range, the thermosetting agent can easily achieve improvements in the peel strength, shear deformation rate, and storage modulus of the adhesive film.

[0108] The adhesive composition may further contain a curing accelerator.

[0109] Curing accelerators assist in the curing reaction of adhesive protective films and can further enhance the cohesive force of the adhesive layer. Curing accelerators may include conventional curing accelerators known to those skilled in the art. Examples of curing accelerators include tin-based metal compounds, zinc-based 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 dimalate, and dimalate tin.

[0110] The curing accelerator may be included in an amount of 0.001 to 3 parts by weight per 100 parts by weight of the (meth)acrylic copolymer. Within this range, it may help to increase the curing speed of the adhesive protective film and improve its cohesive strength.

[0111] The adhesive composition may further contain a silane coupling agent.

[0112] Silane coupling agents can further enhance the peel strength of adhesive protective films. Silane coupling agents may include conventional silane coupling agents known to those skilled in the art. For example, silane coupling agents may include, but are not limited to, epoxy group-containing silane coupling agents such as glycidoxypropyltrimethoxysilane and glycidoxypropylmethyldimethoxysilane.

[0113] The silane coupling agent can be included in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the (meth)acrylic copolymer. Within this range, the effect of improving peel strength can be further achieved.

[0114] The adhesive composition may further contain additives. These additives are those contained in the 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 pigments, UV absorbers, antioxidants, leveling agents, antistatic agents, retarders, catalysts, and rework agents.

[0115] The adhesive composition may further contain a solvent. The solvent can function to enhance the coatability of the adhesive composition and form an adhesive protective film having a thin and uniform surface. The solvent may include common types 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 example, the adhesive composition may have a solid content of 15% to 40% by weight, specifically 20% to 30% by weight, in the adhesive protective film. Within this range, the composition may have excellent coatability.

[0116] The adhesive protective film may have a haze of 5% or less (specifically 0.1% to 2%) and a total light transmittance of 80% or more (specifically 85% to 95%) in the visible light region (e.g., wavelengths of 380nm to 780nm). Within this range, the adhesive protective film has good optical transparency and can be used in optical display devices.

[0117] The thickness of the adhesive layer of the adhesive protective film may be 200 μm or less, specifically between 0 μm and 100 μm, and more specifically between 5 μm and 50 μm. Within this range, it may help provide a protective effect on the flexible panel.

[0118] The adhesive protective film may further include a base film formed on one surface.

[0119] The adhesive protective film may further include a release film formed on another side.

[0120] Another real form is an optical component.

[0121] The optical component includes a polyimide optical element containing polyimide ash on at least one surface, and an adhesive layer bonded to the polyimide ash surface, the adhesive layer containing a photocured product of the adhesive protective film described above.

[0122] In one example, the polyimide-based optical element may be a flexible substrate. The flexible substrate can serve to support optical elements such as organic light-emitting diodes.

[0123] Any additional optical elements can be further laminated on at least one surface of a polyimide-based optical element. Such optical elements can provide predetermined optical functions in an optical display device, such as light emission, polarization, optical compensation, display image quality improvement, and / or conductivity. Examples of optical elements include OLED elements, window films, windows, polarizers, color filters, phase difference films, elliptic polarizing films, reflective polarizing films, anti-reflective films, compensation films, brightness enhancement films, alignment films, light diffusion films, glass shatterproof films, surface protection films, OLED element barrier layers, plastic LCD substrates, transparent electrode films containing ITO (indium tin oxide), FTO (fluorinated tin oxide), AZO (aluminum dopped zinc oxide), CNT (carbon nanotube), Ag nanowires, graphene, etc.

[0124] The adhesive layer includes a photocured adhesive protective film. The adhesive protective film is substantially identical to the one described above.

[0125] In one example, the adhesive layer may be patterned.

[0126] A protective layer can be further laminated onto at least one surface of the adhesive layer.

[0127] The protective layer can protect the adhesive layer or the polyimide optical element. The protective layer is not particularly limited as long as it is optically transparent and provides flexibility. For example, the protective layer may include a polyester film containing polyethylene terephthalate film, polyethylene naphthalate film, polycarbonate film, polyethersulfone film, etc.

[0128] Figure 4 is a cross-sectional view of an example of an optical component. Referring to Figure 4, the optical component may include a polyimide optical element 15 containing polyimide ash on its lower surface, an optical element 20 formed on the upper side of the polyimide optical element 15, and an adhesive layer 33 formed on the lower side of the polyimide optical element 15.

[0129] Another embodiment is an optical display device.

[0130] The optical display device includes a cured product of an adhesive protective film or an optical component. The cured product may be a photocured product.

[0131] The optical display device may include an organic light-emitting element display device, a liquid crystal display device, etc. The optical display device may include a flexible display device. However, the optical display device may also include a non-flexible display device.

[0132] The structure and operation of the present invention will be described in more detail below through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way. [Examples]

[0133] [Example 1] Ethyl acetate was added as a solvent 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 55% by weight of 2-ethylhexyl acrylate (2-EHA), 40% by weight of n-butyl acrylate (n-BA), and 5% by weight of 4-hydroxybutyl acrylate (4-HBA) was added to the reactor. After removing oxygen from the monomer mixture by adding nitrogen gas for 30 minutes, the internal temperature of the reactor was maintained at 62°C. The monomer mixture was uniformly stirred, and 0.07 parts by weight of azobisisobutyronitrile was added as an initiator. The reaction was carried out at 62°C for 8 hours to produce a (meth)acrylic copolymer (glass transition temperature: -60°C, weight-average molecular weight: 600,000 g / mol). Ethyl acetate was added as a solvent to prepare a (meth)acrylic copolymer solution (solids content 24% by weight).

[0134] Fabrication of adhesive protective film A composition for adhesive films with a solid content of 20% by weight was prepared by mixing 100 parts by weight of a manufactured (meth)acrylic copolymer, 1 part by weight of a (meth)acrylic oligomer (weight-average molecular weight of 30,000 g / mol, glass transition temperature of 30°C, and manufactured from a monomer mixture containing 5% by weight of a hydroxyl group-containing (meth)acrylic monomer), 0.23 parts by weight of an isocyanate-based curing agent Coronate-L (TOSOH Corporation), and 1 part by weight of phenoxybenzyl acrylate (PBA).

[0135] The prepared adhesive film composition was applied to the antistatic coated side of a polyethylene terephthalate (PET) film (MCC, T914J50, thickness: 50 μm, with an antistatic layer coated on one side) to a thickness of 25 μm. After drying at 110°C for 4 minutes, a release film (thickness: 50 μm, with a silicone release treatment on one side, MHF50, MCC) was bonded to the resulting adhesive layer. After leaving it at 60°C for 3 days, an adhesive protective film-containing sheet was prepared in which an adhesive protective film (thickness: 25 μm) and a release film were sequentially laminated on the base film.

[0136] [Examples 2-4] A sheet containing an adhesive protective film 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.

[0137] [Comparative Example 1 to Comparative Example 5] A sheet containing an adhesive protective film 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.

[0138] The physical properties of the adhesive protective film-containing sheets prepared in the examples and comparative examples were evaluated as shown in Table 1 below, and the results are shown in Table 1 below.

[0139] [Reference example: Preparation of a polyimide resin layer with polyimide ash covering one surface] A polyimide resin layer containing polyimide ash was fabricated across the entire surface.

[0140] A polyimide varnish coating film was prepared by applying a 20 μm thick layer of polyimide varnish (SD Flex, DuPont) to the upper surface of an alkali-free glass plate (thickness: 1.1 mm) using a doctor blade coating device (gauge diameter: 0.65 mm).

[0141] A polyimide varnish coating film was heat-treated at 80°C for 10 minutes, and then at 120°C for 20 minutes to prepare a dried polyimide varnish coating film (thickness: 20 μm).

[0142] A polyimide varnish coating was cured in a high-temperature chamber at 250°C for 60 minutes to create a laminate of a polyimide resin layer (thickness: 20 μm) and a glass plate.

[0143] Within the laminate, a laser irradiation device (MicroLAS, COHERENT) was positioned above the glass plate, and the laser was irradiated while the laminate was moved from one direction to the other. The laser irradiation conditions were: wavelength 308 nm, femtosecond, and light intensity 170 mJ / cm². 2 That is the case.

[0144] After being held at room temperature for one hour, the glass plate was peeled off the laminate to create a polyimide resin layer containing polyimide ash on one surface.

[0145] (1) Storage modulus (unit: MPa): The adhesive protective films prepared in the examples and comparative examples were laminated to a thickness of 800 μm, and the storage modulus at -20°C was measured using a DHR3 with an axial force of 1.0 N, a sensitivity of 0.1 N, and a frequency of 1.0 Hz.

[0146] (2) Creep (unit: %) The adhesive protective films prepared in the examples and comparative examples were laminated to a thickness of 800 μm, and creep was measured at 60°C using a DHR3 with an axial force of 1.0 N, a sensitivity of 0.1 N, and a frequency of 1.0 Hz.

[0147] (3) Peel strength at high temperature and high humidity (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 surface of the exposed adhesive protective film was bonded to the surface containing polyimide ash in the prepared polyimide resin layer containing polyimide ash. Then, it was pressed with a roll with a 1 kg load, and specimens were prepared by cutting them to a size of 25 mm × 100 mm in width × length. The specimens consisted of a PET film, an adhesive protective film, and a polyimide resin layer containing polyimide ash, laminated in that order.

[0148] The specimens were left at 23°C and 50% RH (relative humidity) for 30 minutes. Subsequently, at 60°C and 93% RH (relative humidity), the peel strength of the adhesive protective film was measured using an Instron peel strength measuring device based on JIS Z 2037, with a peel temperature of 60°C, a peel speed of 300 mm / min, and a peel angle of 180°.

[0149] (4) Simulated bubble fraction (unit: %) The pseudo-bubble rate is evaluated with reference to Figures 5 and 6. The adhesive protective film-containing sheet was cut into a rectangular shape of a predetermined length and width. Then, a polyimide (PI) film was placed on a glass plate, and the release film (base film) was peeled off from the adhesive protective film-containing sheet on the polyimide film. After that, only a portion of the sheet was bonded onto the polyimide film to prepare the test specimen shown in Figure 5.

[0150] Subsequently, when the laminate of the adhesive protective film and the base film was placed on the polyimide film side, the ratio of the bubble area to the total surface area of ​​the polyimide film was calculated. The bubble area was evaluated using an image analyzer.

[0151] [Table 1]

[0152] In Table 1, PBA: Phenoxybenzyl acrylate (see compound below, homopolymer Tg: 6℃) [ka] PHEA-2: Phenoxypolyethylene glycol acrylate (the following compound, homopolymer Tg: -13℃) [ka] ACMO: Acryloylmorpholine (aromatic group-free; homopolymer Tg: 145℃)

[0153] As shown in Table 1, the adhesive protective film of the present invention exhibited high adhesion to polyimide optical elements containing polyimide ash under high temperature and high humidity conditions, excellent folding properties, and excellent wettability to polyimide optical elements containing polyimide ash.

[0154] Simple modifications or alterations of the present invention can be readily carried out by a person with ordinary skill in the art, and all such modifications or alterations can be considered to fall within the scope of the present invention. [Explanation of symbols]

[0155] 10 glass plates 11. Varnish coating 12 Polyimide resin layer 13. Laser irradiation device 14. Polyimide-based ash 15 Polyimide-based optical elements 20 optical elements 33 Adhesive layer

Claims

1. An adhesive protective film for polyimide optical elements containing polyimide ash, The adhesive protective film comprises a cured product of a composition containing a (meth)acrylic copolymer, a curing agent, a (meth)acrylic oligomer, and a monofunctional or more (meth)acrylic monomer containing an aromatic group. The adhesive protective film has a storage modulus of 0.1 MPa or less at -20°C. The adhesive protective film has a peel strength of 350 gf / inch or more at 60°C and 93% relative humidity against the polyimide-based optical element containing the polyimide-based ash. The adhesive protective film is an adhesive protective film in which the creep at 60°C is 40% or less.

2. The adhesive protective film according to claim 1, wherein the (meth)acrylic copolymer has a glass transition temperature (Tg) of -10°C or lower.

3. The adhesive protective film according to claim 1, wherein the (meth)acrylic copolymer is a copolymer of a monomer mixture containing a (meth)acrylic monomer having a homopolymer glass transition temperature of 60°C or less, and a (meth)acrylic monomer having a crosslinkable functional group.

4. The adhesive protective film according to claim 3, wherein the total amount of the (meth)acrylic monomer having a glass transition temperature of 60°C or less, and the (meth)acrylic monomer having a crosslinkable functional group, is contained in the monomer mixture in an amount of 95% by weight or more.

5. The adhesive protective film according to claim 4, wherein the (meth)acrylic monomer having the crosslinkable functional group is contained in the monomer mixture in an amount of 0.1% to 20% by weight.

6. The adhesive protective film according to claim 4, wherein the (meth)acrylic monomer having a glass transition temperature of 60°C or less is a mixture of a linear (meth)acrylic acid ester having a C1-C20 alkyl group and a branched (meth)acrylic acid ester having a C1-C20 alkyl group.

7. The adhesive protective film according to claim 1, wherein the (meth)acrylic oligomer has a glass transition temperature of 60°C or less and a weight-average molecular weight of 100,000 g / mol or less.

8. The adhesive protective film according to claim 1, wherein the (meth)acrylic monomer containing one or more aromatic groups has a homopolymer glass transition temperature of -20°C or higher.

9. The adhesive protective film according to claim 8, wherein the aromatic monofunctional or more (meth)acrylic monomer comprises one or more of phenoxybenzyl (meth)acrylate and phenoxypolyethylene glycol (meth)acrylate.

10. The aforementioned composition, 100 parts by weight of the (meth)acrylic copolymer, The curing agent is present in an amount of 0.01 to 1 part by weight, The (meth)acrylic oligomer in an amount of 0.1 to 3 parts by weight, The adhesive protective film according to claim 1, comprising more than 0 parts by weight and up to 10 parts by weight of the monofunctional (meth)acrylic monomer containing the aromatic group.

11. A polyimide optical element comprising a polyimide ash on at least one surface, and an adhesive layer bonded to the surface comprising the polyimide ash, The adhesive layer comprises a photocured product of the adhesive protective film described in any one of claims 1 to 10, wherein the optical member is an optical member.

12. An optical display device comprising the optical member described in claim 11.

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