Reinforcement film, device with reinforcement film, and method for manufacturing the same

Abstract

The present invention provides a reinforcing film that is easily peeled off immediately after bonding to the substrate, can be firmly bonded to the substrate by photocuring the adhesive after bonding, and is resistant to peeling from the substrate even when repeatedly bent and stretched. [Solution] The reinforcing film (10) comprises an adhesive layer (2) fixedly laminated on one main surface of the film substrate (1). The adhesive layer consists of a photocurable composition comprising an acrylic-based polymer having a crosslinked structure, a photocuring agent, and a photopolymerization initiator, wherein the photocuring agent includes an isocyanurate-containing polyfunctional (meth)acrylate.

Description

[Technical Field]

[0001] The present invention relates to a reinforcing film to be attached to the surface of a device. Furthermore, the present invention relates to a device comprising a reinforcing film and a method for manufacturing the same. [Background technology]

[0002] Adhesive films are sometimes applied to the surfaces of optical devices such as displays and electronic devices for purposes such as surface protection and impact resistance. Typically, such adhesive films have an adhesive layer fixed to the main surface of the film substrate, and are bonded to the device surface via this adhesive layer.

[0003] By temporarily attaching an adhesive film to the surface of a device or device component in a pre-use state such as during assembly, processing, or transportation, damage or breakage of the adherend can be suppressed. Patent Document 1 discloses a reinforcing film comprising an adhesive layer on a film substrate, the adhesive layer being made of a photocurable adhesive composition containing a base polymer and a polyfunctional acrylate as a photocuring agent.

[0004] This reinforcing film has a high gel fraction in its adhesive, resulting in low tackiness immediately after bonding to the substrate, making it easy to peel off. Therefore, rework from the substrate is possible, and the reinforcing film can be selectively peeled off from areas of the substrate where reinforcement is not needed. The adhesive of the reinforcing film adheres firmly to the substrate through photocuring, resulting in a permanent bond of the film substrate to the substrate's surface. This allows it to be used as a reinforcing material for surface protection of devices, etc.

[0005] In recent years, organic EL panels using flexible substrates such as resin films have been put into practical use, and foldable devices have also been commercialized. In foldable devices, bending is repeatedly performed in the same place. At the bending point, compressive stress is applied to the inside and tensile stress to the outside, causing strain to occur at and around the bending point.

[0006] In Patent Document 2, it has been proposed to use an adhesive with a small shear storage modulus at low temperatures to relieve strain at the bending portion and suppress peeling of the adhesive layer at the bending portion of the foldable device.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In the above Patent Document 2, a base polymer with a low glass transition temperature is used, and the amounts of the crosslinking agent and the photocuring agent are reduced, thereby reducing the shear storage modulus of the adhesive at low temperatures after photocuring. However, when the amounts of the crosslinking agent and the photocuring agent are reduced, the adhesive strength of the adhesive before photocuring tends to increase. Also, when the amount of the photocuring agent is small, even if photocuring is performed, the adhesive strength does not become sufficiently large, and there is a tendency for the adhesion reliability to be poor.

[0009] In view of the above, an object of the present invention is to provide a reinforcing film including an adhesive layer that has a small adhesive strength and is easily peeled immediately after being bonded to an adherend, can be firmly bonded to the adherend by photocuring the adhesive after being bonded to the adherend, and has a small shear storage modulus at low temperatures.

Means for Solving the Problems

[0010] The reinforcing film of the present invention comprises an adhesive layer fixedly laminated on one main surface of a film substrate. The adhesive layer consists of a photocurable composition comprising an acrylic-based polymer, a photocuring agent, and a photopolymerization initiator. Preferably, after photocuring, the shear storage modulus of the adhesive layer at -20°C is 100 kPa or less.

[0011] The acrylic-based polymer contains an alkyl (meth)acrylate having a chain-like alkyl group as a constituent monomer, and further contains one or more monomers selected from the group consisting of hydroxyl group-containing monomers and carboxyl group-containing monomers. A cross-linked structure is introduced into the acrylic-based polymer.

[0012] The alkyl (meth)acrylate ester having a chain-like alkyl group as a constituent monomer of the acrylic base polymer is preferably such that the molar average number of carbon atoms of the alkyl group is 5 or more and less than 10. The acrylic base polymer may also have n-octyl acrylate as the monomer with the highest content (main monomer) among the constituent monomers.

[0013] The photocuring agent is a compound having one or more photopolymerizable functional groups. The total content of the photocuring agent in the photocurable composition (adhesive composition) is preferably 1 to 50 parts by weight per 100 parts by weight of the acrylic base polymer.

[0014] The reinforcing film of the present invention comprises a photocurable composition containing an isocyanuryl skeleton-containing polyfunctional (meth)acrylate as a photocuring agent. Examples of isocyanuryl skeleton-containing polyfunctional (meth)acrylates include compounds represented by the following general formula (7).

[0015] [ka]

[0016] In general formula (7), the multiple j and multiple k are each an integer between 0 and 5, and multiple R 7Each of these is an alkylene group having 2 to 6 carbon atoms, and multiple R 4 Each of these is an alkylene group having 2 to 4 carbon atoms, and multiple R 5 Each of these is independently either a hydrogen atom or a methyl group. 6 is a hydrogen atom or -CO-CR 5 =CH2

[0017] In general formula (7), all of the j values ​​may be 0. A polyfunctional (meth)acrylate containing an isocyanurate skeleton in which all of the j values ​​are 0 is represented by the following general formula (3).

[0018] [ka]

[0019] The content of the above-mentioned isocyanurate-containing polyfunctional (meth)acrylate in the photocurable composition is preferably 0.5 to 20 parts by weight per 100 parts by weight of the acrylic base polymer. The photocurable composition may also contain photocurable compounds other than the isocyanurate-containing polyfunctional (meth)acrylate as a photocuring agent.

[0020] Preferably, the adhesive layer has an adhesive strength of 3 N / 25 mm or less to the polyimide film before photocuring. Preferably, the adhesive layer has an adhesive strength of 7 N / 25 mm or more to the polyimide film after photocuring.

[0021] A device with a reinforcing film is obtained by laminating the above-mentioned reinforcing film onto the surface of the device and photocuring the adhesive layer. The device may be a flexible device that can be bent. [Effects of the Invention]

[0022] The reinforcing film of the present invention has an adhesive layer made of a photocurable composition, and the adhesive strength to the adherend is increased by photocuring the adhesive layer after adhesion to the adherend. Before photocuring, the adhesive strength to the adherend is low, so it is easy to peel off from the adherend.

[0023] The adhesive layer of the reinforcing film has low adhesive strength before photocuring, making it easy to peel off (rework) from the substrate. After photocuring, it has high adhesive strength to the substrate and a low shear storage modulus at low temperatures. Therefore, even when repeatedly bent and stretched at the same location, deformation such as wrinkles and peeling from the substrate are less likely to occur. For this reason, the reinforcing film of the present invention can be suitably used in foldable devices using resin film substrates. [Brief explanation of the drawing]

[0024] [Figure 1] This is a cross-sectional view showing the laminated structure of the reinforcing film. [Figure 2] This is a cross-sectional view showing the laminated structure of the reinforcing film. [Figure 3] This is a cross-sectional view showing a device to which a reinforcing film has been attached. [Modes for carrying out the invention]

[0025] Figure 1 is a cross-sectional view showing one embodiment of a reinforcing film. The reinforcing film 10 comprises an adhesive layer 2 on one main surface of a film substrate 1. The adhesive layer 2 is fixedly laminated on one main surface of the film substrate 1. The adhesive layer 2 is a photocurable adhesive made of a photocurable composition, and hardens upon irradiation with active light such as ultraviolet light, increasing the adhesive strength to the adherend.

[0026] Figure 2 is a cross-sectional view of a reinforcing film with a release liner 5 temporarily attached to the main surface of the adhesive layer 2. Figure 3 is a cross-sectional view showing the state in which the reinforcing film 10 is attached to the surface of the device 20.

[0027] The release liner 5 is peeled off from the surface of the adhesive layer 2, and the exposed surface of the adhesive layer 2 is bonded to the surface of the device 20, thereby attaching the reinforcing film 10 to the surface of the device 20. In this state, the adhesive layer 2 is not yet photocured, and the reinforcing film 10 (adhesive layer 2) is temporarily attached to the device 20. By photocuring the adhesive layer 2, the adhesive strength at the interface between the device 20 and the adhesive layer 2 increases, and the device 20 and the reinforcing film 10 are fixed together.

[0028] "Adherence" refers to a state where two laminated layers are firmly bonded together, making separation at their interface impossible or difficult. "Temporary adhesion" refers to a state where the adhesive force between two laminated layers is weak, allowing them to be easily separated at their interface.

[0029] In the reinforcing film shown in Figure 2, the film substrate 1 and the adhesive layer 2 are fixed together, and the release liner 5 is temporarily attached to the adhesive layer 2. When the film substrate 1 and the release liner 5 are peeled apart, peeling occurs at the interface between the adhesive layer 2 and the release liner 5, and the state in which the adhesive layer 2 is fixed to the film substrate 1 is maintained. No adhesive remains on the release liner 5 after peeling.

[0030] In the device with the reinforcing film shown in Figure 3, the device 20 and the adhesive layer 2 are temporarily adhered before the adhesive layer 2 is photocured. When the film substrate 1 and the device 20 are peeled apart, the peeling occurs at the interface between the adhesive layer 2 and the device 20, so the adhesive layer 2 remains fixed to the film substrate 1. Since no adhesive remains on the device 20, peeling operations such as rework and cutting are easy. After the adhesive layer 2 is photocured, the adhesive strength between the adhesive layer 2 and the device 20 increases, and they become fixed, making it difficult to peel the reinforcing film 10 from the device 20.

[0031] [Film substrate] A flexible plastic film is used as the film base material 1 of the reinforcing film 10. In order to fix the film base material 1 and the adhesive layer 2, it is preferable that the surface of the film base material 1 to which the adhesive layer 2 is attached is not treated with a release agent.

[0032] The thickness of the film substrate is, for example, about 4 to 150 μm. From the viewpoint of reinforcing the device by imparting rigidity, shock mitigation, etc., the thickness of the film substrate 1 is preferably 5 μm or more, more preferably 12 μm or more, still more preferably 20 μm or more, and particularly preferably 25 μm or more. From the viewpoint of giving flexibility to the reinforcing film to make it foldable, the thickness of the film substrate 1 is preferably 125 μm or less, more preferably 100 μm or less. From the viewpoint of achieving both mechanical strength and flexibility, the compressive strength of the film substrate 1 is preferably 100 to 3000 kg / cm 2 is preferable, 200 to 2900 kg / cm 2 is more preferable, 300 to 2800 kg / cm 2 is still more preferable, 400 to 2700 kg / cm 2 is particularly preferable.

[0033] Examples of the plastic material constituting the film substrate 1 include polyester resins, polyolefin resins, cyclic polyolefin resins, polyamide resins, polyimide resins, polyether ether ketone, polyether sulfone, polyarylate resins, aramid resins, etc. In the case of a reinforcing film for an optical device such as a display, the film substrate 1 is preferably a transparent film. Further, when irradiating the adhesive layer 2 with active light from the film substrate 1 side to perform photocuring of the adhesive layer, the film substrate 1 preferably has transparency to the active light used for curing the adhesive layer. From the viewpoint of having both mechanical strength and transparency, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, transparent polyimide, and transparent aramid are preferably used. When irradiating the adherend side with active light, it is only necessary that the adherend has transparency to the active light, and the film substrate 1 does not have to be transparent to the active light.

[0034] The surface of the film substrate 1 may be provided with functional coatings such as an easy-adhesion layer, a smooth-slip layer, a release layer, an antistatic layer, a hard coat layer, or an anti-reflective layer. As mentioned above, it is preferable that a release layer is not provided on the surface of the film substrate 1 to which the adhesive layer 2 is attached, in order to fix the film substrate 1 and the adhesive layer 2 together.

[0035] [Adhesive layer] The adhesive layer 2, which is fixedly laminated onto the film substrate 1, is made of a photocurable composition. The photocurable composition constituting the adhesive layer 2 includes an acrylic-based polymer, a photocuring agent, and a photopolymerization initiator.

[0036] Before photocuring, the adhesive layer 2 has low adhesion to the adherend, such as the device or device components, making it easy to peel off. As the adhesive layer 2 is photocured, its adhesion to the adherend improves, making it difficult for the reinforcing film to peel off the device surface even during device use, resulting in excellent adhesive reliability.

[0037] Photocurable adhesives hardly harden under typical storage conditions and harden upon irradiation with active light such as ultraviolet light. Therefore, the reinforcing film of the present invention has the advantage of allowing the timing of the hardening of the adhesive layer 2 to be arbitrarily set, and thus being able to flexibly respond to process lead times and the like.

[0038] The thickness of the adhesive layer 2 is, for example, about 1 to 300 μm. The greater the thickness of the adhesive layer 2, the better the adhesion to the substrate tends to be. On the other hand, if the thickness of the adhesive layer 2 is excessively large, the fluidity before photocuring may be high, making handling difficult. Therefore, the thickness of the adhesive layer 2 is preferably 3 to 100 μm, more preferably 5 to 50 μm, even more preferably 6 to 40 μm, and particularly preferably 8 to 30 μm. From the viewpoint of thinning, the thickness of the adhesive layer 2 may be 25 μm or less, 20 μm or less, or 18 μm or less.

[0039] When the reinforcing film is used in optical devices such as displays, the total light transmittance of the adhesive layer 2 is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The haze of the adhesive layer 2 is preferably 2% or less, more preferably 1% or less, even more preferably 0.7% or less, and particularly preferably 0.5% or less.

[0040] The adhesive layer 2 is preferably one whose adhesive strength to the adherend increases upon photocuring, and which has a low shear storage modulus at low temperatures (hereinafter simply referred to as "storage modulus") even after photocuring. The storage modulus of the adhesive is determined by reading the value at a predetermined temperature when measured at a frequency of 1 Hz and a heating rate of 5°C / min in the range of -70 to 100°C, in accordance with the method described in JIS K7244-1 "Plastics - Test methods for dynamic mechanical properties".

[0041] The storage modulus of the adhesive layer at -20°C after photocuring is preferably 100 kPa or less, more preferably 90 kPa or less, and may be 85 kPa or less or 80 kPa or less. Because the storage modulus of the adhesive layer 2 at low temperatures after photocuring is low, the adhesive layer exhibits strain relaxation properties in low-temperature environments, so peeling of the adhesive layer at the bending point can be suppressed even when the device to which the reinforcing film is bonded is repeatedly bent or when the bent state is maintained for a long time.

[0042] On the other hand, if the storage modulus of the adhesive layer after photocuring is excessively low, the adhesive layer is prone to plastic deformation, and the adhesive layer may peel off from the adherend due to insufficient adhesive strength. Therefore, the storage modulus of the adhesive layer at -20°C after photocuring is preferably 10 kPa or higher, more preferably 20 kPa or higher, even more preferably 30 kPa or higher, and may also be 40 kPa or higher, 50 kPa or higher, 60 kPa or higher, 65 kPa or higher, or 70 kPa or higher.

[0043] <Base polymer> The base polymer is the main component of the adhesive composition and is the key element that determines various properties of the adhesive layer, such as adhesive strength and storage modulus. In this invention, an acrylic polymer is used as the base polymer of the adhesive. Acrylic polymers have excellent optical transparency and adhesion, and their adhesive strength and storage modulus are easily controllable.

[0044] The acrylic-based polymer contains an alkyl (meth)acrylate as a monomer component. In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0045] As the alkyl (meth)acrylate ester, an alkyl (meth)acrylate ester having 1 to 20 carbon atoms in the alkyl group is preferably used. From the viewpoint of suppressing peeling of the adhesive layer when repeatedly bent by lowering the glass transition temperature of the acrylic base polymer and reducing the storage modulus, the alkyl group of the alkyl (meth)acrylate ester is preferably a linear alkyl group. The linear alkyl group may be linear or branched.

[0046] Examples of alkyl (meth)acrylates having a chain-like alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, and (meth) Examples include nonyl acrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate, isotridecyl methacrylate, tetradecyl methacrylate, isotetradecyl methacrylate, pentadecyl methacrylate, cetyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, isooctadyl methacrylate, nonadecyl methacrylate, and eicosyl methacrylate.

[0047] Among the example alkyl (meth)acrylate esters, from the viewpoint of lowering the glass transition temperature of the acrylic-based polymer, (meth)acrylate C 1-9 Alkyl esters are preferred, and those with a homopolymer glass transition temperature of -50°C or lower are preferred. The glass transition temperature of the (meth)acrylate alkyl ester homopolymer is more preferably -55°C or lower, and even more preferably -60°C or lower. (meth)acrylate C with a homopolymer glass transition temperature of -50°C or lower. 1-9Specific examples of alkyl esters include 2-ethylhexyl acrylate (Tg: -70°C), n-hexyl acrylate (Tg: -65°C), n-octyl acrylate (Tg: -65°C), isononyl acrylate (Tg: -60°C), n-nonyl acrylate (Tg: -58°C), isooctyl acrylate (Tg: -58°C), and butyl acrylate (Tg: -55°C). Among these, 2-ethylhexyl acrylate, n-heptyl acrylate, and n-octyl acrylate are preferred, with n-octyl acrylate being particularly preferred, because they can reduce the storage modulus around -20°C.

[0048] The content of (meth)acrylate alkyl ester is preferably 60 parts by weight or more, more preferably 70 parts by weight or more, even more preferably 75 parts by weight or more, and may be 80 parts by weight or more or 85 parts by weight or more, based on 100 parts by weight of the total monomer components constituting the acrylic base polymer. In particular, (meth)acrylate C having a chain alkyl group 1-9 The amount of alkyl ester is preferably within the above range.

[0049] The (meth)acrylate alkyl ester having a chain-like alkyl group as a constituent monomer of the acrylic-based polymer preferably has a molar average number of carbon atoms of the alkyl group of 5 or more and less than 10. The molar average number of carbon atoms is calculated by multiplying the number of moles of each (meth)acrylate alkyl ester by the number of carbon atoms of the alkyl group, summing the results, and dividing the obtained value by the total number of moles of (meth)acrylate alkyl ester.

[0050] The larger the molar average number of carbon atoms in the alkyl group of (meth)acrylate alkyl ester, the more hydrophobic the acrylic-based polymer tends to be. When the molar average number of carbon atoms in the alkyl group of (meth)acrylate alkyl ester is 5 or more, the glass transition temperature of the acrylic-based polymer tends to be low, and the storage modulus at low temperatures tends to be low.

[0051] Furthermore, by having an average molar number of carbon atoms in the alkyl alkyl group of the (meth)acrylate ester being 5 or more and less than 10, the acrylic base polymer and the photocuring agent having an isocyanurate skeleton described later have appropriate compatibility, and the adhesive strength of the adhesive before and after photocuring can be controlled within an appropriate range. From the viewpoint of controlling the adhesive strength of the adhesive before and after photocuring, the average molar number of carbon atoms in the alkyl alkyl group of the (meth)acrylate ester is more preferably 5.5 or more and less than 9, even more preferably 6 or more and less than 8, and may be 7.5 or less or 7.0 or less.

[0052] From the viewpoint of ensuring that the molar average number of carbon atoms of the alkyl group of the alkyl (meth)acrylate is within the above range, the monomer with the highest content (main monomer) among the constituent monomers of the acrylic base polymer is preferably an alkyl (meth)acrylate having a chain-like alkyl group with 6 to 9 carbon atoms, and more preferably an alkyl (meth)acrylate having a chain-like alkyl group with 8 carbon atoms. As alkyl (meth)acrylate having a chain-like alkyl group with 8 carbon atoms, 2-ethylhexyl acrylate and n-octyl acrylate are preferred, and n-octyl acrylate is particularly preferred among them.

[0053] From the viewpoint of ensuring that the molar average number of carbon atoms of the alkyl group of the alkyl (meth)acrylate is within the above range, it is preferable to use in combination an alkyl (meth)acrylate having a chain-like alkyl group with 6 to 9 carbon atoms and an alkyl (meth)acrylate having a chain-like alkyl group with 5 or fewer carbon atoms. Among alkyl (meth)acrylates having a chain-like alkyl group with 5 or fewer carbon atoms, those with 4 carbon atoms in the alkyl group are preferred, and butyl acrylate is particularly preferred.

[0054] The amount of alkyl (meth)acrylate having a chain-like alkyl group with 6 to 9 carbon atoms, relative to 100 parts by weight of the total alkyl (meth)acrylate as a constituent monomer of the acrylic-based polymer, is preferably 40 to 100 parts by weight, more preferably 50 to 95 parts by weight, even more preferably 55 to 90 parts by weight, and may be 60 to 85 parts by weight or 65 to 80 parts by weight. In particular, the amount of alkyl (meth)acrylate having a chain-like alkyl group with 8 carbon atoms is preferably within the above range, and the amount of n-octyl acrylate is particularly preferably within the above range.

[0055] The amount of alkyl (meth)acrylate having a chain alkyl group with 5 or fewer carbon atoms per 100 parts by weight of the total alkyl (meth)acrylate as a constituent monomer of the acrylic base polymer is preferably 0 to 49 parts by weight, and may be 5 to 40 parts by weight, 10 to 35 parts by weight, or 15 to 30 parts by weight. In particular, the amount of alkyl (meth)acrylate having a chain alkyl group with 4 carbon atoms is preferably within the above range, and the amount of butyl acrylate is especially preferably within the above range.

[0056] As constituent monomers of the acrylic-based polymer, in addition to alkyl (meth)acrylates having a chain-like alkyl group with 6 to 9 carbon atoms, alkyl (meth)acrylates having a chain-like alkyl group with 10 or more carbon atoms may also be used. Dodecyl acrylate (lauryl acrylate) is preferred as the alkyl (meth)acrylate having a chain-like alkyl group with 10 or more carbon atoms.

[0057] The amount of alkyl (meth)acrylate having a chain alkyl group with 10 or more carbon atoms relative to 100 parts by weight of the total alkyl (meth)acrylate as a constituent monomer of the acrylic-based polymer is preferably 0 to 49 parts by weight, and may be 5 to 40 parts by weight, 10 to 35 parts by weight, or 15 to 30 parts by weight.

[0058] The acrylic-based polymer contains, as a constituent monomer component, an alkyl (meth)acrylate ester in addition to a monomer having a crosslinkable functional group. Examples of monomers having a crosslinkable functional group include hydroxyl group-containing monomers and carboxyl group-containing monomers. The acrylic-based polymer may have both a hydroxyl group-containing monomer and a carboxyl group-containing monomer as copolymer components, or it may have only one of them. By introducing a crosslinked structure into the acrylic-based polymer, the cohesive force is improved, and the peelability of the adhesive layer 2 from the adherend before photocuring tends to improve.

[0059] Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and 4-(hydroxymethyl)cyclohexylmethyl (meth)acrylate. Among these, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferred because they contribute significantly to improving the adhesive strength of the adhesive after photocuring.

[0060] Examples of carboxyl group-containing monomers include (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, acrylic acid is particularly preferred because it contributes significantly to improving adhesive strength.

[0061] The amount of monomers having crosslinkable functional groups (total amount of hydroxyl group-containing monomers and carboxyl group-containing monomers) relative to 100 parts by weight of the total constituent monomer components of the acrylic base polymer is preferably 0.5 to 20 parts by weight, more preferably 1 to 15 parts by weight, and even more preferably 3 to 12 parts by weight. Since acrylic base polymers containing hydroxyl groups tend to have high shape recovery properties in the adhesive layer, it is preferable for acrylic base polymers to contain hydroxyl group-containing monomers as constituent monomer components, and it is preferable that the content of hydroxyl group-containing monomers is within the above range.

[0062] The acrylic-based polymer may contain nitrogen-containing monomers as constituent monomer components, such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-acryloylmorpholine, N-vinyl carboxylic acid amides, and N-vinylcaprolactam.

[0063] The acrylic-based polymer may contain (meth)acrylic acid esters having alkylene oxide chains as constituent monomer components. The (meth)acrylic acid esters having alkylene oxide chains are represented by the following general formula (1). CH2=CR 1 -COO-(R 2 -O) m -R 3 (1)

[0064] R in general formula (1) 1 R is a hydrogen atom or a methyl group, 1 Compounds of formula (1) in which is a hydrogen atom are acrylates, R 1 Compounds of formula (1) in which the group is a methyl group are methacrylates.

[0065] R in general formula (1) 2 This is an alkylene group having 2 to 4 carbon atoms, and -R 2 -O- is an alkylene oxide chain. -R2 Specific examples of -O- include ethylene oxide (-CH2CH2-O-), propylene oxide (-CH(CH3)CH2-O-), and butylene oxide (-CH2CH2CH2CH2-O-).

[0066] In general formula (1), m is the number of repeating alkylene oxide units and is an integer of 1 or more. m is preferably between 1 and 15. 3 R is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms. From the viewpoint of lowering the Tg of acrylic-based polymers and improving compatibility with photocuring agents, 3 The group is preferably an alkyl group having 1 to 3 carbon atoms, and a methyl group or an ethyl group is particularly preferred.

[0067] The acrylic-based polymer may contain monomer components other than those listed above. For example, the acrylic-based polymer may contain vinyl ester monomers, aromatic vinyl monomers, epoxy group-containing monomers, vinyl ether monomers, sulfo group-containing monomers, phosphate group-containing monomers, acid anhydride group-containing monomers, etc., as monomer components.

[0068] The glass transition temperature of the acrylic-based polymer is preferably -40°C or lower, more preferably -45°C or lower, and may also be -50°C or lower or -55°C or lower. A glass transition temperature sufficiently lower than the ambient temperature of the device results in a low storage modulus of elasticity in the ambient temperature range, which tends to suppress peeling when repeatedly bent. The lower limit of the glass transition temperature of the acrylic-based polymer is not particularly limited, but is generally -80°C or higher, and may also be -75°C or higher or -70°C or higher.

[0069] The glass transition temperature is the temperature at which the loss tangent tanδ in viscoelastic measurements is maximized (peak top temperature). Instead of the glass transition temperature obtained by viscoelastic measurements, the theoretical Tg calculated by Fox's equation may be applied. The theoretical Tg is the glass transition temperature Tg of the homopolymer of the constituent monomer components of an acrylic-based polymer. iAnd the weight fraction W of each monomer component i Therefore, it is calculated using the following Fox formula. 1 / Tg = Σ(W i / Tg i )

[0070] Tg is the glass transition temperature of the polymer chain (unit: K), W i This is the weight fraction (weight-based copolymerization ratio) of monomer component i that constitutes the segment, Tg i is the glass transition temperature (in K) of the homopolymer of monomer component i. The values ​​listed in the Polymer Handbook, 3rd edition (John Wiley & Sons, Inc., 1989) can be used as the glass transition temperature of homopolymers. For homopolymers of monomers not listed in the above literature, the peak top temperature of tanδ obtained by dynamic viscoelasticity measurement can be used.

[0071] Acrylic polymers as base polymers are obtained by polymerizing the above monomer components using various known methods such as solution polymerization, emulsion polymerization, and bulk polymerization. Solution polymerization is preferred from the viewpoint of balancing properties such as adhesive strength and holding power of the adhesive, as well as cost. Ethyl acetate, toluene, etc. are used as solvents for solution polymerization. The solution concentration is usually about 20 to 80% by weight. Various known polymerization initiators such as azo-based and peroxide-based ones can be used. Chain transfer agents may be used to adjust the molecular weight. The reaction temperature is usually about 50 to 80°C, and the reaction time is usually about 1 to 8 hours.

[0072] The weight-average molecular weight of the acrylic-based polymer is preferably 100,000 to 2,000,000, more preferably 200,000 to 1,500,000, and even more preferably 300,000 to 1,000,000. Note that when a cross-linked structure is introduced into the acrylic-based polymer, the molecular weight of the acrylic-based polymer refers to the molecular weight before the introduction of the cross-linked structure.

[0073] <Crosslinking agent> From the viewpoint of providing the adhesive with appropriate cohesive force to exhibit adhesive strength and ensuring the peelability of the adhesive layer from the adherend before photocuring, it is preferable to introduce a crosslinked structure into the acrylic base polymer. For example, a crosslinked structure can be introduced by adding a crosslinking agent to the solution after polymerization of the acrylic base polymer and heating as necessary. The crosslinking agent has two or more crosslinkable functional groups per molecule. The crosslinking agent may also have three or more crosslinkable functional groups per molecule.

[0074] Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelate-based crosslinking agents. These crosslinking agents react with functional groups such as hydroxyl groups and carboxyl groups introduced into the acrylic base polymer to form a crosslinked structure. Isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred because they have high reactivity with the hydroxyl groups and carboxyl groups of the acrylic base polymer and facilitate the introduction of crosslinked structures. Isocyanate-based crosslinking agents are preferred when the acrylic base polymer has hydroxyl groups as crosslinkable functional groups, and epoxy-based crosslinking agents are preferred when the acrylic base polymer has carboxyl groups as crosslinkable functional groups.

[0075] As isocyanate crosslinking agents, polyisocyanates having two or more isocyanate groups in one molecule are used. Isocyanate crosslinking agents may also have three or more isocyanate groups in one molecule. Examples of isocyanate crosslinking agents include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate (e.g., Asahi Kasei's "Duranate D101"); alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate; trimethyl Examples of isocyanate adducts include rollpropane / tolylene diisocyanate trimer adducts (e.g., Mitsui Chemicals' "Takenate D101E"), trimethylolpropane / hexamethylene diisocyanate trimer adducts (e.g., Tosoh's "Coronate HL"), trimethylolpropane adducts of xylylene diisocyanate (e.g., Mitsui Chemicals' "Takenate D110N"), and isocyanurates of hexamethylene diisocyanate (e.g., Tosoh's "Coronate HX"). As isocyanate crosslinking agents, isocyanate compounds having biuret groups (e.g., Asahi Kasei's "Duranate 24A-100") or isocyanate compounds having allophanate groups may be used, and various urethane prepolymers can also be used.

[0076] As the epoxy crosslinking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule is used. The epoxy crosslinking agent may also have three or more or four or more epoxy groups in one molecule. The epoxy groups of the epoxy crosslinking agent may be glycidyl groups. Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate ester, diglycidyl o-phthalate ester, triglycidyl-tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, and bisphenol-S-diglycidyl ether. As epoxy crosslinking agents, commercially available products such as "Denacol" from Nagase ChemteX and "Tetrad X" and "Tetrad C" from Mitsubishi Gas Chemical may be used.

[0077] The amount of crosslinking agent used can be appropriately adjusted depending on the composition and molecular weight of the acrylic base polymer. The amount of crosslinking agent used is approximately 0.005 to 5 parts by weight per 100 parts by weight of the acrylic base polymer, but may also be 0.01 to 3 parts by weight, 0.015 to 1 part by weight, or 0.02 to 0.5 parts by weight.

[0078] A crosslinking catalyst may be used to promote the formation of crosslinked structures. Examples of crosslinking catalysts include organometallic compounds such as organometallic complexes (chelates), compounds of metals and alkoxy groups, and compounds of metals and acyloxy groups; as well as tertiary amines. In particular, organometallic compounds are preferred from the viewpoint of suppressing the progress of the crosslinking reaction in a solution state at room temperature and ensuring the pot life of the adhesive composition. Examples of metals in organometallic compounds include iron, tin, aluminum, zirconium, zinc, titanium, lead, and cobalt. The amount of crosslinking catalyst used is generally 0.1 parts by weight or less per 100 parts by weight of the acrylic base polymer.

[0079] <Photocuring agent> The adhesive composition constituting the adhesive layer 2 contains, in addition to an acrylic base polymer, a compound having a photopolymerizable functional group as a photocuring agent. The adhesive composition containing the photocuring agent is photocurable, and when photocuring is performed after bonding to the adherend, the adhesion strength to the adherend is improved. From the viewpoint of suppressing an excessive increase in storage modulus after photocuring and controlling the adhesion strength, the content of the photocuring agent in the adhesive composition is preferably 1 to 50 parts by weight per 100 parts by weight of the acrylic base polymer.

[0080] (Isocyanuryl skeleton-containing polyfunctional (meth)acrylate) One feature of the reinforcing film of the present invention is that the adhesive composition contains an isocyanurate-containing polyfunctional (meth)acrylate as a photocuring agent.

[0081] An isocyanuric skeleton-containing polyfunctional (meth)acrylate is a compound in which a functional group having a (meth)acryloyl group is bonded to two or more of the three nitrogen atoms of isocyanuric acid. The nitrogen atoms of isocyanuric acid and the (meth)acryloyl group may be bonded via alkylenes, ethers, esters, etc. An example of an isocyanuric skeleton-containing polyfunctional (meth)acrylate is the compound represented by the following general formula (7).

[0082] [ka]

[0083] In general formula (7), the multiple j and multiple k are each an integer between 0 and 5, independently of each other. 7 Each of these is an alkylene group having 2 to 6 carbon atoms. 4 Each of these is an alkylene group having 2 to 4 carbon atoms. 5 Each of these is independently either a hydrogen atom or a methyl group. 6 is a hydrogen atom or -CO-CR 5 =CH2 ((meth)acryloyl group).

[0084] Alkylene group R with 2 to 6 carbon atoms 4 Specific examples include ethylene, propylene, butylene, pentene, and hexene, with pentene being preferred. Structural unit: -CO-(CH2) p The -O- group can be introduced by lactone modification (where p is an integer between 2 and 6). For example, the -CO-(CH2)5-O- structural unit is introduced into the chain by ε-caprolactone modification.

[0085] In general formula (7), all of the j values ​​may be 0. A polyfunctional (meth)acrylate containing an isocyanuric skeleton in which all of the j values ​​in general formula (7) are 0 is represented by the following general formula (3). k, R in general formula (3) 4 , R 5 and R 6 k and R in general formula (7) 4 , R 5 and R 6 It is similar to that.

[0086] [ka]

[0087] Alkylene group R with 2 to 4 carbon atoms 4 Specific examples include ethylene, propylene, and butylene, with ethylene being preferred. That is, the alkylene oxide chain -R 4-O- is preferably ethylene oxide. From the viewpoint of compatibility with acrylic-based polymers, k is preferably 1 to 5, and particularly preferably 1.

[0088] In other words, the compound represented by general formula (7) is preferably an alkylene oxide-modified poly(meth)acrylate of isocyanurate, and is particularly preferably an ethylene oxide-modified poly(meth)acrylate of isocyanurate. Among these, the one in general formula (7) where j is 0 is preferred, and the ethylene oxide-modified poly(meth)acrylate of isocyanurate represented by the following general formula (4) is preferred. 5 and R 6 R in general formula (7) 5 and R 6 It is similar to that.

[0089] [ka]

[0090] Poly(meth)acrylate is either di(meth)acrylate or tri(meth)acrylate. Di(meth)acrylate and tri(meth)acrylate may be used in combination as a photocuring agent, or a mixture of di(meth)acrylate and tri(meth)acrylate may be used.

[0091] R 6 is preferably a hydrogen atom. That is, in the compound represented by general formula (7), j is 0, k is 1, and R 5 It is preferable that the isocyanuric acid alkylene oxide-modified polyacrylate is a hydrogen atom, and among them, R 4 It is particularly preferable that the isocyanurate is ethylene oxide-modified polyacrylate, where isocyanurate is ethylene. Specific examples of isocyanurate ethylene oxide-modified polyacrylate include the diacrylate of formula (5) and the triacrylate of formula (6) below.

[0092] [ka]

[0093] Isocyanurate-containing polyfunctional (meth)acrylates exhibit some degree of compatibility with acrylic-based polymers, but they are not perfectly compatible. When the base polymer and photocuring agent are not perfectly compatible, the photocuring agent tends to concentrate on the surface of the adhesive layer before photocuring (near the adhesive interface with the adherend), and this concentration of photocuring agent at the adhesive interface with the adherend easily forms a weak boundary layer (WBL). When a WBL is formed, the liquid properties of the surface (adhesive interface) become stronger while the bulk properties of the adhesive layer, such as storage modulus, are maintained, so the adhesive strength with the adherend tends to decrease, and the adhesive layer before photocuring is easily peeled off from the adherend.

[0094] When an adhesive layer in which a WBL (Wet Block Line) is formed, with the photocuring agent unevenly distributed near the adhesive interface with the adherend, is photocured, the curing reaction of the photocuring agent proceeds more easily near the adhesive interface where the density of the photocuring agent is high. This tends to increase the cohesive force near the adhesive interface and thus increase the adhesive strength. Furthermore, when a WBL is formed, the increase in the storage modulus, a bulk property of the adhesive, tends to be suppressed after photocuring.

[0095] As mentioned above, the compatibility between the acrylic-based polymer and the isocyanurate-containing polyfunctional (meth)acrylate can be controlled depending on the composition of the acrylic-based polymer, specifically the type of alkyl (meth)acrylate (molar average number of carbon atoms in the alkyl group). This allows for easy WBL formation even with a small amount of photocuring agent, and reduces the adhesive strength of the adhesive layer before photocuring. Furthermore, because the isocyanurate-containing polyfunctional (meth)acrylate has a rigid structure, even a small amount can easily improve its cohesive strength through photocuring, achieving high adhesive strength.

[0096] In other words, by using an isocyanurate-containing polyfunctional (meth)acrylate as a photocuring agent and controlling the composition of the acrylic-based polymer, it is possible to reduce the storage modulus at low temperatures while simultaneously achieving both low adhesion before photocuring and high adhesion after photocuring.

[0097] From the viewpoint of handling ease during the preparation of the adhesive composition and compatibility with acrylic-based polymers, it is preferable that the photocuring agent is liquid at room temperature. The triacrylate of formula (6) above (tris(2-acryloyloxyethyl) isocyanurate) is solid at room temperature, but a mixture of the triacrylate of formula (6) and the diacrylate of formula (5) may be liquid at room temperature. In addition, ε-caprolactone modified triacrylate (in formula (7), at least one k is 1 or greater, and R 4 Compounds in which pentene is present can be liquid at room temperature.

[0098] From the viewpoint of controlling the adhesive strength of the adhesive before and after photocuring while suppressing an excessive increase in the storage modulus, the content of isocyanuryl skeleton-containing polyfunctional (meth)acrylate in the adhesive composition is preferably 0.5 to 20 parts by weight, more preferably 0.7 to 15 parts by weight, even more preferably 1 to 12 parts by weight, and may also be 1.5 to 10 parts by weight, per 100 parts by weight of the acrylic base polymer. When using only isocyanuryl skeleton-containing polyfunctional (meth)acrylate as the photocuring agent, the content of isocyanuryl skeleton-containing polyfunctional (meth)acrylate in the adhesive composition is preferably 1 to 10 parts by weight, more preferably 1.5 to 7 parts by weight, and even more preferably 2 to 5 parts by weight, per 100 parts by weight of the acrylic base polymer.

[0099] (Other photocuring agents) The adhesive composition may contain, as a photocuring agent, compounds having photopolymerizable functional groups other than the isocyanurate skeleton-containing polyfunctional (meth)acrylates described above. Other photocuring agents include photocurable monomers or photocurable oligomers. Ethylene unsaturated bonds are preferred as the photopolymerizable functional groups, and (meth)acryloyl groups are particularly preferred. Other photocuring agents may have one photopolymerizable functional group or two or more photopolymerizable functional groups.

[0100] Examples of monofunctional photocuring agents having a single photopolymerizable functional group include various alkyl (meth)acrylates and oligomers such as urethane (meth)acrylates. Using a monofunctional photocuring agent in addition to a polyfunctional (meth)acrylate containing an isocyanurate skeleton tends to reduce the adhesive strength of the adhesive before photocuring. Furthermore, the combined use of a monofunctional photocuring agent tends to increase the distance between crosslinking points after photocuring, thus reducing the storage modulus at low temperatures.

[0101] From the viewpoint of increasing the distance between crosslinking points and reducing the storage modulus of the adhesive layer at low temperatures after photocuring, a monofunctional photocuring agent is preferably an oligomer with a molecular weight of 1000 or more. From the viewpoint of compatibility with acrylic-based polymers, the weight-average molecular weight of the oligomer as a monofunctional photocuring agent is preferably 1000 to 30000, more preferably 1500 to 20000, and may also be 2000 to 15000. From the viewpoint of reducing the adhesive strength of the adhesive before photocuring and improving the adhesive strength of the adhesive layer after photocuring, urethane (meth)acrylate is preferred as the oligomer.

[0102] When a monofunctional photocuring agent is used in combination with an isocyanurate-containing polyfunctional (meth)acrylate as a photocuring agent, the content of the monofunctional photocuring agent is preferably 1 to 45 parts by weight, more preferably 5 to 40 parts by weight, and may be 10 to 35 parts by weight or 12 to 32 parts by weight per 100 parts by weight of the acrylic base polymer. When a monofunctional photocuring agent is used in combination with an isocyanurate-containing polyfunctional (meth)acrylate as a photocuring agent, the total amount of the photocuring agent is preferably 3 to 50 parts by weight, and may be 5 to 47 parts by weight, 10 to 45 parts by weight, 15 to 42 parts by weight or 20 to 40 parts by weight per 100 parts by weight of the acrylic base polymer.

[0103] As a monofunctional photocuring agent having two or more photopolymerizable functional groups, polyfunctional (meth)acrylate is preferred from the viewpoint of compatibility with acrylic-based polymers. By using a polyfunctional photocuring agent in addition to isocyanur backbone-containing polyfunctional (meth)acrylate as a photocuring agent, it may be possible to control the adhesive strength of the adhesive before and after photocuring within a suitable range.

[0104] Polyfunctional (meth)acrylates are typically esters of polyols and (meth)acrylic acid. Specific examples of polyfunctional (meth)acrylates include: polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and other polyfunctional (meth)acrylates having alkylene oxide chains; alkanediol di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. Examples include glycol esters of (meth)acrylic acid, such as rilate, ditrimethylolpropanetetra(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritol poly(meth)acrylate, dipentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, and glycerin di(meth)acrylate; urethane(meth)acrylate, epoxy(meth)acrylate, butadiene(meth)acrylate, and isoprene(meth)acrylate.

[0105] The polyfunctional (meth)acrylate may be an ester of an alkylene oxide-modified polyol and (meth)acrylic acid. Examples of alkylene oxides include ethylene oxide (EO) and propylene oxide (PO). The alkylene oxide may also be a polyalkylene oxide such as polyethylene glycol or polypropylene glycol.

[0106] Specific examples of alkylene oxide-modified polyfunctional (meth)acrylates include bisphenol A ethylene oxide-modified di(meth)acrylate, bisphenol A propylene oxide-modified di(meth)acrylate, trimethylolpropane ethylene oxide-modified tri(meth)acrylate, trimethylolpropane propylene oxide-modified tri(meth)acrylate, pentaerythritol ethylene oxide-modified tetra(meth)acrylate, and pentaerythritol propylene oxide-modified tetra(meth)acrylate.

[0107] From the viewpoint of compatibility with acrylic-based polymers, polyfunctional (meth)acrylates are preferred, specifically polyfunctional (meth)acrylates having alkylene oxide chains. The functional group equivalent (g / eq) of the polyfunctional (meth)acrylate is preferably 80 to 500, more preferably 90 to 450, even more preferably 100 to 400, and may be 110 to 350 or 120 to 300.

[0108] When a polyfunctional photocuring agent is used in combination with an isocyanurate-containing polyfunctional (meth)acrylate as a photocuring agent, the content of the polyfunctional photocuring agent other than the isocyanurate-containing polyfunctional (meth)acrylate is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, and may be 1 to 7 parts by weight or 1.5 to 5 parts by weight per 100 parts by weight of the acrylic base polymer. When a polyfunctional photocuring agent is used in combination with an isocyanurate-containing polyfunctional (meth)acrylate as a photocuring agent, the total amount of the polyfunctional photocuring agent, including the isocyanurate-containing polyfunctional (meth)acrylate, is preferably 1 to 20 parts by weight, and may be 1.5 to 15 parts by weight, 2 to 10 parts by weight, 2.5 to 8 parts by weight or 3 to 7 parts by weight per 100 parts by weight of the acrylic base polymer.

[0109] <Photopolymerization initiator> Photopolymerization initiators generate active species upon irradiation with active light, thereby accelerating the curing reaction of photocuring agents. Depending on the type of photocuring agent, photocationic initiators (photoacid generators), photoradical initiators, photoanionic initiators (photobase generators), etc., are used as photopolymerization initiators. When a polyfunctional acrylate is used as the photocuring agent, it is preferable to use a photoradical initiator. As photoradical initiators, photoradical generators that cleave and generate radicals upon irradiation with visible light or ultraviolet light with a wavelength shorter than 450 nm are preferred, and examples include hydroxyketones, benzyldimethylketals, aminoketones, acylphosphine oxides, benzophenones, and trichloromethyl group-containing triazine derivatives. Photoradical generators may be used alone or in mixtures of two or more types.

[0110] The content of the photopolymerization initiator in the adhesive composition is preferably 0.001 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, and even more preferably 0.03 to 1 part by weight, per 100 parts by weight of the acrylic base polymer. The content of the photopolymerization initiator in the adhesive composition is preferably 0.02 to 20 parts by weight, more preferably 0.05 to 10 parts by weight, and even more preferably 0.1 to 7 parts by weight, per 100 parts by weight of the total photocuring agent.

[0111] <Other ingredients> As described above, the photocurable adhesive composition constituting the adhesive layer 2 includes an acrylic-based polymer, a photocuring agent, and a photopolymerization initiator. In addition to these components, the adhesive composition may also contain additives such as silane coupling agents, tackifiers, plasticizers, softeners, degradation inhibitors, fillers, colorants, UV absorbers, antioxidants, surfactants, and antistatic agents, to the extent that they do not impair the properties of the present invention.

[0112] [Fabrication of reinforcing film] A reinforcing film is obtained by laminating a photocurable adhesive layer 2 onto a film substrate 1. The adhesive layer 2 may be formed directly on the film substrate 1, or an adhesive layer formed in sheet form on another substrate may be transferred onto the film substrate 1.

[0113] The above adhesive composition is applied to a substrate by methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, die coating, etc., and the solvent is dried and removed as necessary to form an adhesive layer. A suitable drying method can be used as appropriate. The heating and drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and even more preferably 70°C to 170°C. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, and even more preferably 10 seconds to 10 minutes.

[0114] If the adhesive composition contains a crosslinking agent, it is preferable to promote crosslinking by heating or aging simultaneously with or after the drying of the solvent. The heating temperature and heating time are set appropriately depending on the type of crosslinking agent used, and crosslinking is usually carried out by heating for about 1 minute to 7 days in the range of 20°C to 160°C. Heating to dry and remove the solvent may also serve as heating for crosslinking.

[0115] Even after a crosslinked structure is introduced into the polymer by a crosslinking agent, the photocuring agent remains unreacted. Therefore, the adhesive layer 2 contains an acrylic-based polymer with a crosslinked structure, a photocuring agent, and a photopolymerization initiator. When forming the adhesive layer 2 on a film substrate 1, it is preferable to attach a release liner 5 to the adhesive layer 2 for purposes such as protecting the adhesive layer 2. Crosslinking may also be performed after attaching the release liner 5 to the adhesive layer 2.

[0116] When forming the adhesive layer 2 on another substrate, a reinforcing film is obtained by transferring the adhesive layer 2 onto the film substrate 1 after the solvent has dried. The substrate used to form the adhesive layer may also be used as the release liner 5.

[0117] As the release liner 5, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film are preferably used. The thickness of the release liner is usually 3 to 200 μm, preferably about 10 to 100 μm. The contact surface of the release liner 5 with the adhesive layer 2 is preferably treated with a release agent such as silicone, fluorine, long-chain alkyl, or fatty acid amide, or silica powder. Because the surface of the release liner 5 is treated with a release agent, when the release liner 5 is peeled off from the film substrate 1, peeling occurs at the interface between the adhesive layer 2 and the release liner 5, and the state in which the adhesive layer 2 is fixed on the film substrate 1 is maintained. The release liner 5 may have an antistatic treatment applied to either the release-treated surface or the untreated surface, or both. By applying an antistatic treatment to the release liner 5, static charge can be suppressed when the release liner is peeled off from the adhesive layer.

[0118] [Physical properties of the adhesive layer] From the viewpoint of facilitating peeling from the adherend and preventing adhesive residue from remaining on the adherend after peeling off the reinforcing film, the adhesive strength between the adhesive layer and the adherend before photocuring is preferably 3N / 25mm or less, more preferably 2.5N / 25mm or less, and may also be 2N / 25mm or less, 1.5N / 25mm or less, or 1N / 25mm or less. From the viewpoint of preventing peeling of the reinforcing film during storage and handling, the adhesive strength between the adhesive layer and the adherend before photocuring is preferably 0.01N / 25mm or more, more preferably 0.02N / 25mm or more, and may also be 0.03N / 25mm or more, 0.04N / 25mm or more, or 0.05N / 25mm or more.

[0119] When the adhesive layer 2 is photocured, the photocuring agent undergoes a curing reaction, increasing the adhesive strength to the adherend. As mentioned above, it is preferable that the adhesive layer 2 has a low storage modulus at low temperatures after photocuring. From the viewpoint of adhesive reliability during practical use of the device, the adhesive strength between the photocured adhesive layer and the adherend is preferably 7N / 25mm or higher, more preferably 8N / 25mm or higher, and may also be 9N / 25mm or higher or 10N / 25mm or higher.

[0120] The adhesive strength between the adhesive layer after photocuring and the adherend is preferably at least twice, more preferably at least three times, and may be 3.5 times, 4 times, 4.5 times, or 5 times or more than the adhesive strength between the adhesive layer and the adherend before photocuring.

[0121] Adhesion strength is determined by a peel test using polyimide film as the substrate, at a tensile speed of 300 mm / min and a peel angle of 180°. Unless otherwise specified, adhesion strength is measured at 25°C.

[0122] Because the adhesive layer 2 after photocuring has a low storage modulus at low temperatures and high adhesive strength, peeling of the adhesive layer at the bending point can be suppressed even when the device to which the reinforcing film is bonded is repeatedly bent or when the bent state is maintained for a long period of time. As described above, by using an isocyanurate skeleton-containing polyfunctional (meth)acrylate as the photocuring agent and adjusting the composition of the acrylic base polymer, it is possible to keep the adhesive strength of the adhesive layer before and after photocuring within a suitable range while reducing the storage modulus at low temperatures of the adhesive layer after photocuring.

[0123] [Use of reinforcing film] The reinforcing film of the present invention is used by laminating it to a device or device component. The reinforcing film 10 has an adhesive layer 2 fixed to the film substrate 1, and before photocuring after lamination to the adherend, the adhesive strength to the adherend is low. Therefore, before photocuring, the reinforcing film can be easily peeled off the adherend.

[0124] The substrate to which the reinforcing film is bonded is not particularly limited and can include various electronic devices, optical devices and their components. In one embodiment, the reinforcing film is bonded to the surface of a bendable flexible device such as a foldable device or a rollable device. A foldable device has a hinge and can be folded around this hinge. If the device is a display device, the reinforcing film may be bonded to the screen side surface or to the back side (housing). In a flexible device that is configured to bend at a predetermined location such as a hinge, bending and stretching are repeatedly performed at the same location during use.

[0125] The reinforcing film may be bonded to the entire surface of the substrate, or it may be selectively bonded only to the areas requiring reinforcement (reinforcement target areas). Alternatively, the reinforcing film may be bonded to both the areas requiring reinforcement (reinforcement target areas) and the areas not requiring reinforcement (non-reinforcement target areas), and then the reinforcing film bonded to the non-reinforcement target areas may be cut and removed. If the adhesive has not yet been photocured, the reinforcing film is only temporarily attached to the surface of the substrate, and can therefore be easily peeled off and removed from the surface of the substrate. Alternatively, the reinforcing film may be bonded to the reinforcement target areas and the non-reinforcement target areas, and then the adhesive in the reinforcement target areas may be selectively irradiated with light to photocur the adhesive, after which the reinforcing film in the non-reinforcement target areas, where the adhesive has not yet cured, may be selectively peeled off and removed.

[0126] By laminating a reinforcing film, appropriate rigidity is imparted, which is expected to improve handling and prevent damage to thin components such as flexible devices. In the device manufacturing process, if a reinforcing film is laminated to work-in-progress, the reinforcing film may be laminated to the large work-in-progress before it is cut to product size. In devices manufactured by a roll-to-roll process, the reinforcing film may also be laminated to the mother roll using a roll-to-roll method.

[0127] After the reinforcing film is bonded to the substrate, the adhesive layer 2 is photocured by irradiating it with active light. Examples of active light include ultraviolet light, visible light, infrared light, X-rays, alpha rays, beta rays, and gamma rays. Ultraviolet light is preferred as the active light because it can suppress hardening of the adhesive layer during storage and is easy to cure. The irradiation intensity and duration of the active light can be appropriately set according to the composition and thickness of the adhesive layer. Irradiation of the adhesive layer 2 with active light may be performed from either the film substrate 1 side or the substrate side, or from both sides.

[0128] As described above, by laminating the reinforcing film of the present invention, appropriate rigidity is imparted to the adherend, and stress is relieved and dispersed, thereby suppressing various defects that may occur in the manufacturing process, improving production efficiency, and improving yield. The reinforcing film is easily peeled off from the adherend before the adhesive layer is photocured, so rework is easy even if lamination or bonding defects occur. Furthermore, processing such as selectively removing the reinforcing film from areas other than the reinforcement target area is also easy.

[0129] During use of the completed device, even if the device is unexpectedly subjected to external forces such as being dropped, having heavy objects placed on it, or being struck by flying objects, the reinforcement film prevents damage to the device. Furthermore, because the reinforcement film adheres firmly to the device after the adhesive has been photocured, it is less likely to peel off even after long-term use, resulting in superior reliability.

[0130] In a device with a reinforced film, where the reinforcing film of the present invention is laminated to a flexible device using a resin substrate, deformation such as wrinkles in the reinforcing film at the bending point and peeling of the reinforcing film from the device are unlikely to occur even when repeated bending and stretching are performed, or when the bent state is maintained for a long period of time, demonstrating excellent adhesive reliability. [Examples]

[0131] The present invention will be further explained below with reference to examples and comparative examples, but it is not limited to these examples.

[0132] [Preparation of adhesive layer and reinforcing film] <Polymerization of acrylic polymers> In a reaction vessel equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas inlet tube, 100 parts by weight of monomers in the weight ratios shown in Table 1, 0.065 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator, and 150 parts by weight of ethyl acetate as a solvent were added. Nitrogen gas was then introduced, and the mixture was purged with nitrogen while stirring for approximately 1 hour. Subsequently, the mixture was heated to 57°C and reacted for 6 hours to obtain solutions of acrylic polymers A to D.

[0133] <Preparation of adhesive composition> To a solution of an acrylic polymer (100 parts by weight as polymer solids), 0.3 parts by weight of IGM Resins' "Omnirad 651" as a photocuring agent, crosslinking agent, crosslinking catalyst, and photopolymerization initiator of the types and amounts shown in Table 1, and 0.3 parts by weight of 1-ethyl-3-methylimidazolium bisfluorosulfonylimide (Daiichi Kogyo Seiyaku's "Elexel AS-110") as an antistatic agent were added and uniformly mixed to prepare an adhesive composition.

[0134] In Examples 1-10 and Comparative Examples 1-4, 0.025 parts by weight of a bifunctional isocyanate crosslinking agent ("Duranate D101" manufactured by Asahi Kasei) was used as the crosslinking agent, and 0.05 parts by weight of iron acetylacetonate ("Nasem Ferric" manufactured by Nippon Chemical Industrial Co., Ltd.) was used as the crosslinking catalyst. In Example 11, 0.025 parts by weight of a tetrafunctional epoxy crosslinking agent ("Tetrad C" manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used as the crosslinking agent, and 0.05 parts by weight of zirconium tetraacetylacetonate ("ZC-150" manufactured by Matsumoto Fine Chemical Co., Ltd.) was used as the crosslinking catalyst.

[0135] <Preparation of reinforcing film> The above adhesive composition was applied to a 50 μm thick polyethylene terephthalate film using an applicator to a dry thickness of 18 μm. After drying at 130°C for 3 minutes to remove the solvent, the release-treated side of a release liner (a 38 μm thick polyethylene terephthalate film with both sides treated with antistatic agents and one side with a silicone release agent) was bonded to the adhesive-coated surface. Subsequently, an aging treatment was performed in a 50°C atmosphere for 3 days to promote crosslinking, resulting in a reinforced film in which a photocurable adhesive sheet was fixedly laminated on the polyethylene terephthalate film substrate, with the release liner temporarily attached on top.

[0136] [evaluation] The following evaluations were performed on the reinforcing films obtained in the above examples and comparative examples.

[0137] <Storage modulus of the adhesive layer> Adhesive compositions were applied and crosslinked onto a release liner in the same manner as in each of the above examples and comparative examples to prepare an adhesive sheet (before photocuring). A release liner was attached to the surface of the adhesive layer of the adhesive sheet before photocuring to block oxygen, and 1000 mJ / cm² was exposed to light using a 365 nm LED lamp. 2 The adhesive sheets were photocured by irradiation with ultraviolet light. After photocuring, the adhesive sheets were stacked to prepare a sample with a thickness of approximately 0.8 mm for measurement. Dynamic viscoelasticity measurements were performed using a dynamic viscoelasticity analyzer (TA Instruments "ARES-G2") under the following conditions, and the value of the shear storage modulus G' at -20°C was read. Transformation mode: Twist Measurement frequency: 1Hz Heating rate: 5°C / min Measurement temperature: -70~100℃ Shape: Parallel plate 8.0mmφ

[0138] <Adhesive strength> A 25 μm thick polyimide film (UBE "UPIREX 25S") was attached to a SUS plate via double-sided adhesive tape (Nitto Denko "No. 531") to obtain a polyimide film substrate for measurement. The release liner was peeled off from the surface of a reinforcing film cut to a width of 25 mm x length of 100 mm, and it was bonded to the polyimide film substrate for measurement using a hand roller to obtain a test sample before photocuring. The adhesive layer of the test sample before photocuring was photocured by irradiating it with ultraviolet light from the reinforcing film side (PET film substrate side) to obtain a test sample after photocuring. Using a Shimadzu "Autograph AGX-V2", the end of the film substrate of the reinforcing film in the test sample was held with a chuck, and the reinforcing film was peeled 180° at a tensile speed of 300 mm / min to measure the peel strength.

[0139] [Evaluation Results] Table 1 shows the composition of the adhesives of the reinforcing films in the examples and comparative examples (composition of the acrylic polymer, as well as the type of photocuring agent and the amount blended per 100 parts by weight of the solids of the acrylic polymer), and the evaluation results. In Table 1, monomers and photocuring agents are indicated by the following abbreviations. Of the photocuring agents listed below, A9300 was solid at room temperature, while the other photocuring agents were liquid at room temperature.

[0140] <Monomer> BA: Butyl acrylate 2EHA: 2-Ethylhexyl acrylate NOAA: n-octyl acrylate LA: Lauryl acrylate 4HBA: 4-hydroxybutyl acrylate AA: Acrylic acid

[0141] <Photocuring agent> M923: Isocyanuric acid EO-modified polyacrylate, bifunctional to trifunctional (Toagosei's "Aronics M-923", with a diacrylate ratio of 50% or more) M935: Isocyanuric acid EO-modified polyacrylate, bifunctional to trifunctional (Toagosei's "Aronics M-923", triacrylate ratio of 50% or more) M313: Isocyanuric acid EO-modified polyacrylate, bifunctional to trifunctional (Toagosei's "Aronics M-313", diacrylate ratio 30-40%) A9300: Isocyanuric acid EO-modified triacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd. as "NK Ester A9300") A9300-1CL: Tris(2-acryloyloxyethyl) isocyanurate modified from ε-caprolactone (manufactured by Shin-Nakamura Chemical Industry Co., Ltd. as "NK Ester A9300-1CL") A400: Polyethylene glycol #400 (n=9) diacrylate (Shin Nakamura Chemical Industry Co., Ltd. "NK Ester A-400", functional group equivalent 263g / eq) A600: Polyethylene glycol #600 (n=14) diacrylate (Shin Nakamura Chemical Industry Co., Ltd. "NK Ester A600", functional group equivalent 371 g / eq) LD301: Monofunctional urethane acrylate with a weight-average molecular weight of 10,000 (AGC's "U-Fine LD-301")

[0142] [Table 1]

[0143] The reinforcing film of Example 1, which used an adhesive compound comprising polymer A with NOAA as the main monomer and 3 parts by weight of isocyanuryl skeleton-containing acrylate as a photocuring agent, exhibited an adhesive strength of 3 N / 25 mm or less before photocuring and an adhesive strength of 7 N / 25 mm or more after photocuring, as well as a low storage modulus G' of the adhesive layer at low temperatures (-20°C) after photocuring, demonstrating excellent properties for foldable device applications.

[0144] Examples 5, 7, and 8, which varied the type of isocyanuryl skeleton-containing acrylate (the ratio of diacrylate to triacrylate), also showed excellent properties similar to those of Example 1. Example 9, which used an isocyanuryl skeleton-containing acrylate with a chain-like ester structure introduced by ε-caprolactone modification, showed similar results. A comparison of Examples 1, 5, 7, and 8 reveals that the lower the ratio of triacrylate and the higher the ratio of diacrylate in the isocyanuryl skeleton-containing acrylate, the lower the storage modulus of the adhesive layer at low temperatures after photocuring tends to be.

[0145] In Comparative Example 4, where the amount of isocyanurate-containing acrylate as the photocuring agent was 0.5 parts by weight, the storage modulus at low temperature after photocuring was smaller than that of Example 1. However, in Comparative Example 4, the adhesive strength of the adhesive layer before photocuring was high, and even after photocuring, the adhesive strength did not increase, but rather decreased. Comparative Examples 2 and 3, which did not use isocyanurate-containing acrylate as the photocuring agent but used polyethylene glycol diacrylate, showed insufficient increase in adhesive strength due to photocuring compared to Example 1, etc.

[0146] These results indicate that isocyanurate-containing acrylates, when used as photocuring agents, are excellent at reducing adhesive strength before photocuring and enhancing adhesive strength after photocuring.

[0147] Example 11, which used polymer D instead of polymer A and an epoxy crosslinking agent instead of an isocyanate crosslinking agent, showed higher adhesive strength compared to Example 1, but the low-temperature storage modulus after photocuring was large. It is thought that the acrylic acid constituting polymer D has a higher glass transition temperature than the hydroxyl group-containing monomer (4HBA) and therefore has a higher cohesive force as an adhesive, which affects physical properties such as adhesive strength and storage modulus.

[0148] Example 10, which used polymer B with a larger molar average number of carbon atoms in the alkyl group of the alkyl acrylate instead of polymer A, showed a lower low-temperature storage modulus after photocuring compared to Example 1, but also a lower adhesive strength. Comparative Example 1, which used polymer C with a smaller molar average number of carbon atoms in the alkyl group of the alkyl acrylate, showed a significantly increased adhesive strength before photocuring compared to Example 1. These results suggest that the compatibility between the acrylic-based polymer and the isocyanurate-containing acrylate used as the photocuring agent affects the adhesive strength of the adhesive layer before and after photocuring.

[0149] Example 2, which used polyethylene glycol diacrylate in addition to isocyanurate-containing acrylate as a photocuring agent, showed superior adhesive properties, with lower adhesive strength before photocuring and higher adhesive strength after photocuring compared to Example 1. A similar trend was observed when comparing Examples 5 and 6. Example 3, in which the ratio of isocyanurate-containing acrylate to polyethylene glycol diacrylate was changed, showed superior adhesive properties, with higher adhesive strength after photocuring compared to Example 1. Furthermore, Examples 2 and 3 showed lower storage modulus at low temperatures for the adhesive layer after photocuring compared to Example 1. Example 6 showed a lower storage modulus at low temperatures for the adhesive layer after photocuring compared to Example 5.

[0150] In Example 4, which used a monofunctional urethane acrylate oligomer in addition to an isocyanurate skeleton-containing acrylate as a photocuring agent, the adhesive strength before photocuring was significantly reduced compared to Example 1, while the adhesive strength after photocuring was high. Furthermore, in Example 4, the storage modulus of the adhesive layer at low temperatures after photocuring was lower compared to Example 1.

[0151] These results indicate that by using other photocurable compounds in addition to isocyanuryl skeleton-containing acrylate as a photocuring agent, and by adjusting the type and amount of these compounds, it is possible to achieve improved adhesive properties and a reduction in low-temperature storage modulus (improved flexibility) compared to using isocyanuryl skeleton-containing acrylate alone as the photocuring agent. [Explanation of Symbols]

[0152] 1. Film substrate 2. Adhesive layer 10 Reinforcement film 5. Release Liner 20 Adherent

Claims

1. The film substrate comprises an adhesive layer fixedly laminated on one main surface of the film substrate. The adhesive layer comprises a photocurable composition containing an acrylic-based polymer, a photocuring agent which is a compound having one or more photopolymerizable functional groups, and a photopolymerization initiator. The photocurable composition contains a total of 1 to 50 parts by weight of the photocuring agent per 100 parts by weight of the acrylic base polymer. The acrylic-based polymer comprises, as constituent monomers, one or more selected from the group consisting of (meth)acrylate alkyl esters having a chain alkyl group, and hydroxyl group-containing monomers and carboxyl group-containing monomers, and the acrylic-based polymer has a crosslinked structure introduced into it. The aforementioned photocuring agent includes an isocyanurate-containing polyfunctional (meth)acrylate, The adhesive layer, after photocuring, has a shear storage modulus of 100 kPa or less at -20°C. Reinforcement film.

2. The reinforcing film according to claim 1, wherein the photocurable composition contains 0.5 to 20 parts by weight of the isocyanurate-containing polyfunctional (meth)acrylate per 100 parts by weight of the acrylic-based polymer.

3. The reinforcing film according to claim 1, wherein the alkyl (meth)acrylate ester having a chain alkyl group as a constituent monomer of the acrylic base polymer has a molar average number of carbon atoms of 5 or more and less than 10.

4. The reinforcing film according to claim 1, wherein the acrylic-based polymer has n-octyl acrylic acid as the most abundant monomer among its constituent monomers.

5. The reinforcing film according to claim 1, wherein the isocyanurate-containing polyfunctional (meth)acrylate is a compound represented by the following general formula (7): 【Chemistry 1】 In general formula (7), Multiple j and multiple k are each an integer between 0 and 5, independently of each other. Multiple R ７ These are, independently, alkylene groups having 2 to 6 carbon atoms. Multiple R ４ These are, independently, alkylene groups having 2 to 4 carbon atoms. Multiple R ５ Each of these is independently either a hydrogen atom or a methyl group. R ６ is a hydrogen atom or -CO-CR ５ =CH ２ That is the case.

6. The reinforcing film according to claim 1, wherein the isocyanurate-containing polyfunctional (meth)acrylate is a compound represented by the following general formula (3): 【Chemistry 2】 In general formula (3), Each of the multiple k values ​​is an integer between 0 and 5, independently of the others. Multiple R ４ These are, independently, alkylene groups having 2 to 4 carbon atoms. Multiple R ５ Each of these is independently either a hydrogen atom or a methyl group. R ６ is a hydrogen atom or -CO-CR ５ =CH ２ is.

7. The reinforcing film according to claim 1, wherein the adhesive layer has an adhesive strength of 3 N / 25 mm or less to the polyimide film before photocuring.

8. The reinforcing film according to claim 1, wherein the adhesive layer has an adhesive strength of 7 N / 25 mm or more to the polyimide film after photocuring.

9. A device with a reinforcing film, wherein a reinforcing film is attached to the surface of a foldable device, The reinforcing film comprises a film substrate and an adhesive layer fixedly laminated on one main surface of the film substrate. The adhesive layer is bonded to the surface of the device. The adhesive layer is made of a photocured product obtained by photocuring a photocurable adhesive composition containing an acrylic-based polymer, a photocuring agent which is a compound having one or more photopolymerizable functional groups, and a photopolymerization initiator. The acrylic-based polymer comprises, as constituent monomers, one or more selected from the group consisting of (meth)acrylate alkyl esters having a chain alkyl group, and hydroxyl group-containing monomers and carboxyl group-containing monomers, and the acrylic-based polymer has a crosslinked structure introduced into it. The aforementioned photocuring agent includes an isocyanurate-containing polyfunctional (meth)acrylate, The adhesive layer has a shear storage modulus of 100 kPa or less at -20°C. Device with reinforcing film.

10. The device with a reinforcing film according to claim 9, wherein the isocyanurate-containing polyfunctional (meth)acrylate is a compound represented by the following general formula (7): 【Transformation 3】 In general formula (7), Multiple j and multiple k are each an integer between 0 and 5, independently of each other. Multiple R ７ These are, independently, alkylene groups having 2 to 6 carbon atoms. Multiple R ４ These are, independently, alkylene groups having 2 to 4 carbon atoms. Multiple R ５ Each of these is independently either a hydrogen atom or a methyl group. R ６ is a hydrogen atom or -CO-CR ５ =CH ２ That is the case.

11. The device with a reinforcing film according to claim 9, wherein the isocyanurate-containing polyfunctional (meth)acrylate is a compound represented by the following general formula (3): 【Chemistry 4】 In general formula (3), Each of the multiple k values ​​is an integer between 0 and 5, independently of the others. Multiple R ４ These are, independently, alkylene groups having 2 to 4 carbon atoms. Multiple R ５ Each of these is independently either a hydrogen atom or a methyl group. R ６ is a hydrogen atom or -CO-CR ５ =CH ２ That is the case.

12. A method for manufacturing a device with a reinforcing film, wherein a reinforcing film is attached to the surface of a foldable device, The adhesive layer of the reinforcing film according to any one of claims 1 to 8 is bonded to the surface of a foldable device. The adhesive layer is photocured. A method for manufacturing a device with a reinforcing film.

Images