Reinforcing film, device with reinforcing film and manufacturing method thereof

Abstract

The invention relates to a reinforcing film, a device with the reinforcing film and a manufacturing method thereof. The reinforcing film (10) is provided with an adhesive layer (2) which is adhesively laminated on one main surface of a film substrate (1). The pressure-sensitive adhesive layer is formed from a photocurable composition containing an acrylic base polymer having a cross-linked structure, a photocuring agent, and a photopolymerization initiator, and containing a polyfunctional (meth) acrylate containing an isocyanuric acid skeleton as the photocuring agent. The reinforcing film of the present invention is easy to peel off 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 is unlikely to peel off from the adherend even when repeatedly bent and stretched.

Description

Technical Field

[0001] This invention relates to a reinforcing film applied to the surface of a device. Furthermore, this invention relates to a device having a reinforcing film and a method for manufacturing the same. Background Technology

[0002] For purposes such as surface protection and impact resistance, adhesive films are sometimes attached to the surfaces of optical and electronic devices, such as displays. Such adhesive films typically have an adhesive layer laminated on the main surface of the film substrate, which is then used to adhere the film to the device surface.

[0003] Before use, such as during assembly, processing, or transportation, an adhesive film can be temporarily bonded to the surface of the device or its constituent parts to prevent damage or breakage. Patent Document 1 discloses a reinforcing film having an adhesive layer formed of a photocurable adhesive composition on a film substrate. This photocurable adhesive composition includes a base polymer and a polyfunctional acrylate as a photocuring agent.

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

[0005] In recent years, organic EL (Electro-Luminescence) panels using flexible substrates such as resin films have been put into practical use, as have foldable devices. In foldable devices, the same location is repeatedly bent. Compressive stress is applied to the inner side of the bent area, while tensile stress is applied to the outer side, thus generating strain at and around the bent area.

[0006] Patent document 2 proposes that by using an adhesive with a low shear storage modulus at low temperatures, the strain at the bending part is relaxed, thereby suppressing the peeling of the adhesive layer at the bending part of the foldable device.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2020-41113

[0010] Patent Document 2: International Publication No. 2022 / 050009

[0011] In Patent Document 2 mentioned above, the low-temperature shear storage modulus of the adhesive after photocuring was reduced by using a base polymer with a low glass transition temperature and reducing the amount of crosslinking agent and photocuring agent used. However, when the amount of crosslinking agent and photocuring agent used is reduced, there is a tendency for the adhesive strength of the adhesive before photocuring to increase. Furthermore, when the amount of photocuring agent used is small, even if photocuring is performed, the adhesive strength cannot be sufficiently increased, and there is a tendency for poor adhesive reliability. Summary of the Invention

[0012] In view of the above, the object of the present invention is to provide a reinforcing film having an adhesive layer that has low adhesive force and is easy to peel off immediately after being bonded to the substrate, can be firmly bonded to the substrate by photocuring the adhesive after being bonded to the substrate, and has a low shear storage modulus at low temperature.

[0013] The reinforcing film of the present invention comprises an adhesive layer bonded to a main surface of a film substrate. The adhesive layer is formed of a photocurable composition comprising an acrylic-based polymer, a photocuring agent, and a photopolymerization initiator. Preferably, the adhesive layer has a shear storage modulus of less than 100 kPa at -20°C after photocuring.

[0014] In the case of acrylic-based basic polymers, the constituent monomers include alkyl (meth)acrylates having chain-like alkyl groups, and include one or more monomers selected from the group consisting of hydroxyl-containing monomers and carboxyl-containing monomers. Crosslinking structures are introduced into the acrylic-based basic polymers.

[0015] Preferably, in the alkyl (meth)acrylate monomers having chain-like alkyl groups, the molar average number of carbon atoms of the alkyl group is 5 or more and less than 10. Alternatively, the most abundant monomer (main monomer) in the monomers constituting the acrylic-based polymer is n-octyl acrylate.

[0016] The photocuring agent is a compound having one or more photopolymerizable functional groups. Preferably, the total content of the photocuring agent in the photocurable composition (adhesive composition) is 1 to 50 parts by weight relative to 100 parts by weight of the acrylic base polymer.

[0017] With regard to the reinforcing film of the present invention, the photocurable composition comprises a polyfunctional (meth)acrylate containing an isocyanuric acid backbone as a photocuring agent. Examples of polyfunctional (meth)acrylates containing an isocyanuric acid backbone include compounds represented by the following general formula (7).

[0018]

[0019] In general formula (7), multiple j and multiple k are independent integers from 0 to 5, and multiple R 7 Each is independently an alkylene group having 2 to 6 carbon atoms, with multiple R... 4 Each is independently an alkylene group having 2 to 4 carbon atoms, with multiple R... 5 Each can be independently a hydrogen atom or a methyl group. R 6 It is a hydrogen atom or -CO-CR 5 =CH2.

[0020] In general formula (7), multiple j can all be 0. A polyfunctional (meth)acrylate containing an isocyanuric acid skeleton, in which multiple j are all 0, is represented by the following general formula (3).

[0021]

[0022] Preferably, the content of the polyfunctional (meth)acrylate containing the isocyanuric acid backbone in the photocurable composition is 0.5 to 20 parts by weight relative to 100 parts by weight of the acrylic base polymer. The photocurable composition may also contain a photocurable compound other than the polyfunctional (meth)acrylate containing the isocyanuric acid backbone as a photocuring agent.

[0023] Preferably, the adhesive layer has an adhesion force of less than 3 N / 25 mm to the polyimide film before photocuring. More preferably, the adhesive layer has an adhesion force of more than 7 N / 25 mm to the polyimide film after photocuring.

[0024] By bonding the aforementioned reinforcing film to the surface of the device and then photocuring the adhesive layer, a device with a reinforcing film can be obtained. The device can also be a flexible, bendable device.

[0025] Invention Effects

[0026] The adhesive layer of the reinforcing film of the present invention is formed from a photocurable composition. By photocuring the adhesive layer after bonding with the substrate, the adhesion to the substrate increases. Since the adhesion to the substrate is low before photocuring, it is easy to peel off from the substrate.

[0027] Regarding the adhesive layer of the reinforcing film, the adhesion strength before photocuring is low, making it easy to peel off from the substrate (rework). After photocuring, the adhesion strength to the substrate is high, and the shear storage modulus at low temperatures is small. Therefore, even if the same area is repeatedly bent and stretched, it is not easy to produce wrinkles or other deformations, nor is it easy to peel off from the substrate. Therefore, the reinforcing film of the present invention can also be applied to foldable devices using resin film substrates. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view showing the laminated structure of the reinforcing membrane.

[0029] Figure 2 This is a cross-sectional view showing the laminated structure of the reinforcing membrane.

[0030] Figure 3 This is a cross-sectional view showing a device with a reinforcing film attached.

[0031] Explanation of reference numerals in the attached figures

[0032] 1: Membrane substrate; 2: Adhesive layer; 10: Reinforcing membrane; 5: Release liner; 20: Adhesive. Detailed Implementation

[0033] Figure 1 This is a cross-sectional view showing one embodiment of the reinforcing membrane. The reinforcing membrane 10 has an adhesive layer 2 on one main surface of the membrane substrate 1. The adhesive layer 2 is bonded to one main surface of the membrane substrate 1. The adhesive layer 2 is a photocurable adhesive formed from a photocurable composition, which is cured by irradiation with active light such as ultraviolet light, thereby increasing the adhesion strength to the adhered object.

[0034] Figure 2 This is a cross-sectional view of a reinforcing film to which a release liner 5 is temporarily bonded on the main surface of adhesive layer 2. Figure 3 This is a cross-sectional view showing the state in which the reinforcing film 10 is attached to the surface of the device 20.

[0035] 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 adhered 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 in a temporary bonded state to the reinforcing film 10 (adhesive layer 2) on the device 20 before photocuring. By photocuring the adhesive layer 2, the adhesive force at the interface between the device 20 and the adhesive layer 2 increases, and the device 20 and the reinforcing film 10 are bonded together.

[0036] "Firm bonding" refers to a state where two layers are firmly bonded together, and the interface between them cannot be separated or is difficult to separate. "Temporary bonding" refers to a state where the adhesive force between two layers is weak, and the layers can be easily separated at the interface.

[0037] exist Figure 2 In the reinforced membrane shown, the membrane substrate 1 is bonded to the adhesive layer 2, and the release liner 5 is temporarily bonded to the adhesive layer 2. When the membrane substrate 1 and the release liner 5 are peeled off, peeling occurs at the interface between the adhesive layer 2 and the release liner 5, maintaining the adhesive layer 2 bonded to the membrane substrate 1. No adhesive residue remains on the release liner 5 after peeling.

[0038] Figure 3Before the photocuring of the adhesive layer 2, the device 20 with the reinforcing film shown is temporarily bonded to the adhesive layer 2. When the film substrate 1 and the device 20 are peeled off, peeling occurs at the interface between the adhesive layer 2 and the device 20, thus maintaining the adhesive layer 2 adhered to the film substrate 1. Since no adhesive residue remains on the device 20, peeling operations such as rework and cutting are easy to perform. After the adhesive layer 2 is photocured, the adhesion between the adhesive layer 2 and the device 20 increases, becoming firmly bonded, making it difficult to peel the reinforcing film 10 from the device 20.

[0039] [Membrane substrate]

[0040] As the membrane substrate 1 of the reinforcing membrane 10, a flexible plastic membrane is used. In order to bond the membrane substrate 1 to the adhesive layer 2, it is preferable that the adhesive layer 2 attachment surface of the membrane substrate 1 is not subjected to release treatment.

[0041] The thickness of the membrane substrate is, for example, about 4 to 150 μm. From the viewpoint of reinforcing the device by imparting rigidity and mitigating impact, the thickness of the membrane substrate 1 is preferably 5 μm or more, more preferably 12 μm or more, further preferably 20 μm or more, and particularly preferably 25 μm or more. From the viewpoint of making the reinforcing membrane flexible and foldable, the thickness of the membrane substrate 1 is preferably 125 μm or less, more preferably 100 μm or less. From the viewpoint of balancing mechanical strength and flexibility, the compressive strength of the membrane substrate 1 is preferably 100 to 3000 kg / cm². 2 More preferably, it is 200–2900 kg / cm². 2 Further preferred values ​​are 300–2800 kg / cm². 2 The preferred strength is 400–2700 kg / cm². 2 .

[0042] Examples of plastic materials constituting the film substrate 1 include: polyester resins, polyolefin resins, cyclic polyolefin resins, polyamide resins, polyimide resins, polyetheretherketone, polyethersulfone, polyarylate resins, and aromatic polyamide resins. In reinforcing films used in optical devices such as displays, the film substrate 1 is preferably a transparent film. Furthermore, when photocuring the adhesive layer 2 by irradiating it with active light from the film substrate 1 side, the film substrate 1 preferably has transparency to the active light used for curing the adhesive layer. Considering both mechanical strength and transparency, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, transparent polyimides, and transparent aromatic polyamides are preferred. When irradiating the adhesive with active light from the adherend side, the film substrate 1 may be opaque to the active light, as long as the adherend is transparent to the active light.

[0043] Functional coatings such as easy-to-adhere layer, easy-to-slip layer, release layer, antistatic layer, hard coating layer, and anti-reflective layer can also be provided on the surface of the membrane substrate 1. It should be noted that, as mentioned above, in order to bond the membrane substrate 1 to the adhesive layer 2, it is preferable not to provide a release layer on the surface where the adhesive layer 2 is attached to the membrane substrate 1.

[0044] [Adhesive layer]

[0045] The adhesive layer 2, which is laminated onto the film substrate 1, is formed of a photocurable composition. The photocurable composition constituting the adhesive layer 2 includes an acrylic-based polymer, a photocuring agent, and a photopolymerization initiator.

[0046] Before photocuring, adhesive layer 2 has low adhesion to the device, device components, and other adhered objects, making it easy to peel off. Adhesive layer 2 utilizes photocuring to improve adhesion to the adhered objects, so even when the device is in use, the reinforcing film is not easily peeled off from the device surface, resulting in excellent bonding reliability.

[0047] Photocurable adhesives hardly cure under normal storage conditions, but rather cure through irradiation with active light such as ultraviolet light. Therefore, the reinforcing film of the present invention allows for arbitrary setting of the curing time of the adhesive layer 2, providing advantages such as flexible adaptation to process lead time.

[0048] The thickness of adhesive layer 2 is, for example, about 1 to 300 μm. There is a tendency that the greater the thickness of adhesive layer 2, the better the adhesion to the substrate. On the other hand, if the thickness of adhesive layer 2 is too large, the flowability before photocuring is high, sometimes making it difficult to process. Therefore, the thickness of 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 thinness, the thickness of adhesive layer 2 can also be 25 μm or less, 20 μm or less, or 18 μm or less.

[0049] 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.

[0050] The adhesive layer 2 preferably utilizes photocuring to increase the adhesion to the adherend, and the shear storage modulus (hereinafter referred to as "storage modulus") remains small even at low temperatures after photocuring. The storage modulus of the adhesive is determined by reading the value at a specified temperature when measured according to the method described in JIS K 7244-1 "Plastics - Test methods for dynamic mechanical properties" at a frequency of 1 Hz and a heating rate of 5 °C / min within the range of -70 to 100 °C.

[0051] The storage modulus of the photocured adhesive layer at -20°C is preferably below 100 kPa, more preferably below 90 kPa, and may also be below 85 kPa or 80 kPa. By making the storage modulus of the photocured adhesive layer 2 small at low temperatures, the adhesive layer exhibits strain relaxation in low-temperature environments. Therefore, even when the device with the reinforcing film is repeatedly bent or kept in a bent state for a long time, peeling of the adhesive layer at the bending location can be suppressed.

[0052] On the other hand, if the storage modulus of the photocured adhesive layer is too small, the adhesive layer is prone to plastic deformation, and sometimes the adhesive layer peels off from the adherend due to insufficient adhesive holding force. Therefore, the storage modulus of the photocured adhesive layer at -20°C is preferably 10 kPa or more, more preferably 20 kPa or more, even more preferably 30 kPa or more, and may also be 40 kPa or more, 50 kPa or more, 60 kPa or more, 65 kPa or more, or 70 kPa or more.

[0053] <Basic Polymers>

[0054] The base polymer is the main component of the adhesive composition and is the primary factor determining the adhesive layer's adhesive strength, storage modulus, and other properties. In this invention, an acrylic polymer is used as the base polymer of the adhesive. Acrylic polymers exhibit excellent optical transparency and adhesion, and their adhesive strength, storage modulus, and other properties are easily controlled.

[0055] Acrylic-based polymers contain alkyl (meth)acrylates as monomer components. It should be noted that in this specification, "(meth)acrylate" refers to acrylic acid and / or methacrylic acid.

[0056] As an alkyl (meth)acrylate, it is preferable to use an alkyl (meth)acrylate with 1 to 20 carbon atoms in the alkyl group. From the viewpoint of suppressing peeling of the adhesive layer during repeated bending by lowering the glass transition temperature and storage modulus of the acrylic-based polymer, the alkyl group of the alkyl (meth)acrylate is preferably a chain alkyl group. The chain alkyl group can be straight-chain or branched.

[0057] Examples of alkyl (meth)acrylates having chain-like alkyl groups include: methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and so on. (Meth) isononyl acrylate, (meth) decyl acrylate, (meth) isodecyl acrylate, (meth) undecyl acrylate, (meth) dodecyl acrylate, (meth) isotridecyl acrylate, (meth) tetradecyl acrylate, (meth) isotetradecyl acrylate, (meth) pentadecyl acrylate, (meth) hexadecyl acrylate, (meth) heptadecanyl acrylate, (meth) octadecyl acrylate, (meth) isooctadecyl acrylate, (meth) nonadecanyl acrylate, (meth) eicosyl acrylate, etc.

[0058] In the alkyl methacrylates exemplified, from the viewpoint of lowering the glass transition temperature of the acrylic-based polymer, C(meth)acrylate is preferred. 1－9 Alkyl esters, preferably alkyl (meth)acrylates whose homopolymers have a glass transition temperature of -50°C or less. More preferably, the glass transition temperature of the homopolymer of the alkyl (meth)acrylate is -55°C or less, and even more preferably -60°C or less. (Meth)acrylate C, as a homopolymer, has a glass transition temperature of -50°C or less. 1－9 Specific examples of alkyl esters include: 2-ethylhexyl acrylate (Tg: -70℃), n-hexyl acrylate (Tg: -65℃), n-octyl acrylate (Tg: -65℃), isononyl acrylate (Tg: -60℃), n-nonyl acrylate (Tg: -58℃), isooctyl acrylate (Tg: -58℃), and butyl acrylate (Tg: -55℃). Among these, considering the reduction of storage modulus near -20℃, 2-ethylhexyl acrylate, n-heptyl acrylate, and n-octyl acrylate are preferred, with n-octyl acrylate being particularly preferred.

[0059] The content of alkyl (meth)acrylate relative to 100 parts by weight of the total monomer components constituting the acrylic-based basic polymer 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 also be 80 parts by weight or more or 85 parts by weight or more. Among them, the (meth)acrylate C having chain alkyl groups... 1－9 The amount of alkyl ester is preferably within the above range.

[0060] In alkyl (meth)acrylates having chain-like alkyl groups, which are constituent monomers of acrylic-based basic polymers, the molar average number of carbon atoms of the alkyl groups is preferably 5 or more and less than 10. The molar average number of carbon atoms is calculated by multiplying the number of moles of each alkyl (meth)acrylate by the number of carbon atoms of the alkyl group and summing the results, then dividing the resulting value by the total number of moles of the alkyl (meth)acrylate.

[0061] The higher the molar average carbon number of the alkyl group in (meth)acrylate, the higher the hydrophobicity of the acrylic-based polymer tends to be. By making the molar average carbon number of the alkyl group in (meth)acrylate ester 5 or more, there is a tendency for the acrylic-based polymer to have a lower glass transition temperature and a lower storage modulus at low temperatures.

[0062] Furthermore, by ensuring that the molar average number of alkyl carbon atoms in the (meth)acrylate is 5 or more and less than 10, the acrylic-based polymer exhibits moderate compatibility with the isocyanuric acid backbone-containing photocuring agent described later, allowing the adhesive strength of the adhesive before and after photocuring to be controlled within an appropriate range. From the viewpoint of controlling the adhesive strength before and after photocuring, the molar average number of alkyl carbon atoms in the (meth)acrylate is more preferably 5.5 or more and less than 9, further preferably 6 or more and less than 8, and may also be 7.5 or less or 7.0 or less.

[0063] From the viewpoint of setting the molar average number of carbon atoms of the alkyl group in (meth)acrylates within the above-mentioned range, the monomer (main monomer) with the highest content among the constituent monomers of acrylic-based basic polymers is preferably a (meth)acrylate with a chain alkyl group having 6 to 9 carbon atoms, more preferably a (meth)acrylate with a chain alkyl group having 8 carbon atoms. As a (meth)acrylate with a chain alkyl group having 8 carbon atoms, 2-ethylhexyl acrylate and n-octyl acrylate are preferred, with n-octyl acrylate being particularly preferred.

[0064] From the viewpoint of setting the molar average number of carbon atoms of the alkyl group in the (meth)acrylate within the range described above, it is preferable to use a combination of (meth)acrylates with chain alkyl groups having 6 to 9 carbon atoms and (meth)acrylates with chain alkyl groups having 5 or fewer carbon atoms. Among (meth)acrylates with chain alkyl groups having 5 or fewer carbon atoms, (meth)acrylates with alkyl groups having 4 carbon atoms are preferred, and butyl acrylate is particularly preferred.

[0065] Relative to 100 parts by weight of the total amount of alkyl (meth)acrylates that are constituent monomers of the acrylic-based base polymer, the amount of alkyl (meth)acrylates having 6 to 9 carbon atoms 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 also be 60 to 85 parts by weight or 65 to 80 parts by weight. Preferably, the amount of alkyl (meth)acrylates having 8 carbon atoms is within the above range, and particularly preferably, the amount of n-octyl acrylate is within the above range.

[0066] Relative to 100 parts by weight of the total amount of alkyl (meth)acrylates that are constituent monomers of the acrylic-based base polymer, the amount of alkyl (meth)acrylates having a chain alkyl group having 5 or fewer carbon atoms is preferably 0 to 49 parts by weight, but may also be 5 to 40 parts by weight, 10 to 35 parts by weight, or 15 to 30 parts by weight. Preferably, the amount of alkyl (meth)acrylates having a chain alkyl group having 4 carbon atoms is within the above range, and particularly preferably, the amount of butyl acrylate is within the above range.

[0067] As constituent monomers of acrylic-based basic polymers, in addition to alkyl (meth)acrylates having chain alkyl groups with 6 to 9 carbon atoms, alkyl (meth)acrylates having chain alkyl groups with 10 or more carbon atoms can also be used. As alkyl (meth)acrylates having chain alkyl groups with 10 or more carbon atoms, dodecyl acrylate (laurate acrylate) is preferred.

[0068] The amount of (meth)acrylate alkyl ester having 10 or more carbon atoms is preferably 0 to 49 parts by weight relative to the total 100 parts by weight of (meth)acrylate alkyl ester, which is a constituent monomer of the acrylic base polymer. It can also be 5 to 40 parts by weight, 10 to 35 parts by weight or 15 to 30 parts by weight.

[0069] Acrylic-based base polymers, in addition to containing alkyl (meth)acrylates, also include monomers with crosslinkable functional groups as constituent monomer components. Examples of monomers with crosslinkable functional groups include hydroxyl-containing monomers and carboxyl-containing monomers. Acrylic-based base polymers can contain both hydroxyl-containing and carboxyl-containing monomers as copolymer components, or only one of them. By introducing a crosslinking structure into acrylic-based base polymers, there is a tendency to improve cohesive strength and the peelability of the adhesive layer 2 from the adhered substrate before photocuring.

[0070] Examples of hydroxyl-containing monomers include: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylaurate methacrylate, and 4-(hydroxymethyl)cyclohexyl methacrylate. Among these, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferred due to their significant contribution to improving the adhesive strength of the photocured adhesive.

[0071] Examples of carboxyl-containing monomers include: (meth)acrylic acid, 2-carboxyethyl (meth)acrylic acid, carboxypentyl (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, acrylic acid is particularly preferred due to its significant contribution to improving adhesive strength.

[0072] Relative to 100 parts by weight of the total constituent monomer components of the acrylic base polymer, the amount of monomers having crosslinkable functional groups (the total amount of hydroxyl-containing monomers and carboxyl-containing monomers) 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. When the acrylic base polymer contains hydroxyl groups, considering the tendency for high shape resilience of the adhesive layer, the acrylic base polymer preferably contains hydroxyl-containing monomers as constituent monomer components, and the content of hydroxyl-containing monomers is preferably within the above-mentioned range.

[0073] Acrylic base polymers can also contain nitrogen-containing monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazolium, vinyloxazole, vinylmorpholine, N-acryloylmorpholine, N-vinylcarboxylic acid amides, and N-vinylcaprolactam as constituent monomer components.

[0074] Acrylic-based polymers may also contain (meth)acrylates with alkylene oxide chains as constituent monomers. (meth)acrylates with alkylene oxide chains are represented by the following general formula (1).

[0075] CH2=CR 1 -COO- (R 2 -O) m -R 3 (1)

[0076] R in general formula (1) 1 R is a hydrogen atom or a methyl group. 1 The compound of formula (1) with hydrogen atoms is an acrylate, R 1 The compound of formula (1) with methyl is a methacrylate.

[0077] R in general formula (1) 2 It is an alkylene group with 2 to 4 carbon atoms, -R 2 -O- represents an alkylene oxide chain. As -R 2 Specific examples of -O- include: ethylene oxide (-CH2CH2-O-), propylene oxide (-CH(CH3)CH2-O-), and butylene oxide (-CH2CH2CH2CH2-O-).

[0078] In general formula (1), m is the number of repetitions of the alkylene oxide unit, which is an integer of 1 or more. m is preferably 1 to 15. R 3 It is a hydrogen atom, an alkyl group with 1 to 12 carbon atoms, or an aryl group with 6 to 20 carbon atoms. From the viewpoint of reducing the Tg of acrylic-based polymers and improving compatibility with photocuring agents, R... 3 Preferably, it is an alkyl group having 1 to 3 carbon atoms, and particularly preferably methyl or ethyl.

[0079] Acrylic base polymers may contain monomer components other than those mentioned above. Acrylic base polymers may contain monomer components such as vinyl ester monomers, aromatic vinyl monomers, epoxy-containing monomers, vinyl ether monomers, sulfonate-containing monomers, phosphate-containing monomers, and anhydride-containing monomers.

[0080] The glass transition temperature of acrylic-based polymers is preferably below -40°C, more preferably below -45°C, and can also be below -50°C or -55°C. By making the glass transition temperature sufficiently lower than the operating temperature of the device, there is a tendency for the adhesive layer to have a low storage modulus over the operating temperature range, and for peeling during repeated bending to be suppressed. The lower limit of the glass transition temperature of acrylic-based polymers is not particularly limited, but is typically above -80°C, and can also be above -75°C or -70°C.

[0081] The glass transition temperature is the temperature at which the loss tangent (tanδ) in viscoelasticity measurements reaches its maximum (peak temperature). Alternatively, the theoretical Tg calculated according to the Fox equation can be used instead of the glass transition temperature obtained from viscoelasticity measurements. The theoretical Tg is based on the following Fox equation, representing the glass transition temperature of a homopolymer of acrylic-based basic polymers. i and the weight fraction W of each monomer component i Calculated.

[0082] 1 / Tg=Σ(W i / Tg i )

[0083] Tg is the glass transition temperature of the polymer chain (unit: K), W. iTg represents the weight fraction (weight-based copolymerization ratio) of monomer component i constituting the chain segment. i Let Tg be the glass transition temperature (in K) of the homopolymer of monomer component i. The glass transition temperature of the homopolymer can be the value recorded in the third edition of the Polymer Handbook (John Wiley & Sons, Inc., 1989). For homopolymers of monomers not recorded in the above literature, the Tg can be the peak temperature of tanδ obtained by dynamic viscoelasticity determination.

[0084] The above-mentioned monomer components are polymerized using various known methods such as solution polymerization, emulsion polymerization, and bulk polymerization to obtain acrylic polymers as the base polymer. From the perspective of balancing adhesive properties such as adhesion and holding power, as well as cost, solution polymerization is preferred. Ethyl acetate, toluene, etc., can be used as solvents for solution polymerization. The solution concentration is typically around 20–80% by weight. Various known polymerization initiators, such as azo-based and peroxide-based initiators, can be used as polymerization initiators. Chain transfer agents can be used to adjust the molecular weight. The reaction temperature is typically around 50–80°C, and the reaction time is typically around 1–8 hours.

[0085] The weight-average molecular weight of the acrylic-based base 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. It should be noted that when a cross-linking structure is introduced into the acrylic-based base polymer, the molecular weight of the acrylic-based base polymer refers to the molecular weight before the introduction of the cross-linking structure.

[0086] <Cross-linking agent>

[0087] From the viewpoint of ensuring the adhesive possesses appropriate cohesive strength, exhibits adhesive strength, and guarantees the peelability of the adhesive layer from the adherend before photocuring, it is preferable to introduce a crosslinking structure into the acrylic base polymer. For example, a crosslinking agent is added to the solution after the acrylic base polymer has been polymerized, and heating is applied as needed, thereby introducing the crosslinking structure. The crosslinking agent has two or more crosslinking functional groups in one molecule. The crosslinking agent may also be a crosslinking agent having three or more crosslinking functional groups in one molecule.

[0088] 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 and carboxyl groups introduced into the acrylic-based polymer to form a crosslinked structure. Considering the high reactivity with the hydroxyl and carboxyl groups of the acrylic-based polymer and the ease of introducing crosslinked structures, isocyanate-based and epoxy-based crosslinking agents are preferred. When the acrylic-based polymer has hydroxyl groups as crosslinkable functional groups, isocyanate-based crosslinking agents are preferred; when the acrylic-based polymer has carboxyl groups as crosslinkable functional groups, epoxy-based crosslinking agents are preferred.

[0089] As an isocyanate-based crosslinking agent, a polyisocyanate having two or more isocyanate groups in one molecule is used. An isocyanate-based crosslinking agent can also be an isocyanate-based crosslinking agent having three or more isocyanate groups in one molecule. Examples of isocyanate-based 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-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenylenediamine diisocyanate; trimethylolpropane / toluene diisocyanate trimer adducts (e.g., Mitsui Chemicals' "TAKENATE D101E"), trimethylolpropane / hexamethylene diisocyanate trimer adducts (e.g., Tosoh's "CORONATE HL"), and trimethylolpropane adducts of phenylenediamine diisocyanate (e.g., Mitsui Chemicals' "TAKENATE"). Isocyanate adducts such as D110N”, hexamethylene diisocyanate isocyanurate (e.g., Tosoh's “CORONATE HX”), etc. As isocyanate-based crosslinking agents, isocyanate compounds with biuret groups (e.g., Asahi Kasei's “DURANATE 24A-100”), isocyanate compounds with urethane groups, and various urethane prepolymers can also be used.

[0090] As an epoxy crosslinking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule can be used. An epoxy crosslinking agent can also be an epoxy crosslinking agent having three or more epoxy groups in one molecule. The epoxy groups in an epoxy crosslinking agent can be glycidyl groups. Examples of epoxy-based crosslinking agents include: N,N,N',N'-tetraglycidyl-m-phenylenediamine, diglycidyl-aniline, 1,3-bis(N,N-diglycidyl-aminomethyl)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 anhydride polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, etc. As an epoxy crosslinking agent, commercially available products such as "Denacol" manufactured by Nagase ChemteX and "TETRAD X" and "TETRAD C" manufactured by Mitsubishi Gas Chemical can be used.

[0091] The amount of crosslinking agent used can be adjusted appropriately according to the composition and molecular weight of the acrylic base polymer. The amount of crosslinking agent used is about 0.005 to 5 parts by weight relative to 100 parts by weight of the acrylic base polymer, or it can be 0.01 to 3 parts by weight, 0.015 to 1 part by weight, or 0.02 to 0.5 parts by weight.

[0092] To promote the formation of cross-linked structures, cross-linking catalysts can be used. Examples of cross-linking catalysts include organometallic compounds (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 cross-linking reaction in solution at room temperature to ensure the pot life of the adhesive composition. Examples of metals that can be used as organometallic compounds include iron, tin, aluminum, zirconium, zinc, titanium, lead, and cobalt. The amount of cross-linking catalyst used is typically 0.1 parts by weight or less relative to 100 parts by weight of the acrylic base polymer.

[0093] <Light curing agent>

[0094] In addition to the acrylic-based polymer, the adhesive composition constituting adhesive layer 2 also contains a compound with photopolymerizable functional groups as a photocuring agent. The adhesive composition containing the photocuring agent exhibits photocurability, and when photocured after bonding with the substrate, the adhesion to the substrate is improved. From the viewpoint of suppressing excessive increases in storage modulus after photocuring and controlling adhesive strength, the content of the photocuring agent in the adhesive composition is preferably 1 to 50 parts by weight relative to 100 parts by weight of the acrylic-based polymer.

[0095] (Polyfunctional (meth)acrylates containing an isocyanuric acid backbone)

[0096] One of the features of the reinforcing film of the present invention is that the adhesive composition contains a polyfunctional (meth)acrylate containing an isocyanuric acid backbone as a photocuring agent.

[0097] Polyfunctional (meth)acrylates containing an isocyanuric acid skeleton refer to compounds in which two or more of the three nitrogen atoms of isocyanuric acid are bonded to functional groups having (meth)acryloyl groups. The nitrogen atoms of isocyanuric acid and the (meth)acryloyl groups can be bonded by alkylene groups, ethers, esters, etc. Examples of polyfunctional (meth)acrylates containing an isocyanuric acid skeleton include compounds represented by the following general formula (7).

[0098]

[0099] In general formula (7), multiple j and multiple k are independent integers from 0 to 5. Multiple R 7 Each is independently an alkylene group having 2 to 6 carbon atoms. Multiple R 4 Each is independently an alkylene group having 2 to 4 carbon atoms. Multiple R 5 Each can be independently a hydrogen atom or a methyl group. R 6 It is a hydrogen atom or -CO-CR 5 =CH2((meth)acryloyl).

[0100] As an alkylene group with 2 to 6 carbon atoms, R 4 Specific examples include ethylene, propylene, butylene, pentylene, and hexylene, with pentylene being preferred. Structural unit: -CO-(CH2) p -O- can be introduced through lactone modification (p is an integer from 2 to 6). For example, the -CO-(CH2)5-O- structural unit can be introduced into the chain through ε-caprolactone modification.

[0101] In general formula (7), multiple j can all be 0. A polyfunctional (meth)acrylate containing an isocyanuric acid backbone in general formula (7) where multiple j are 0 is represented by the following general formula (3). In general formula (3), k, R... 4 R5 and R 6 With general formula (7) k, R 4 R 5 and R 6 same.

[0102]

[0103] As an alkylene group with 2 to 4 carbon atoms, R 4 Specific examples include: ethylene, propylene, and butylene, with ethylene being preferred. That is, -R as an alkylene oxide chain. 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.

[0104] That is, the compound represented by general formula (7) is preferably poly(meth)acrylate modified with alkylene oxide of isocyanurate, and particularly preferably poly(meth)acrylate modified with ethylene oxide of isocyanurate. Among these, compounds in general formula (7) where j is 0 are preferred, and poly(meth)acrylate modified with ethylene oxide of isocyanurate as described below is more preferred. In general formula (4), R... 5 and R 6 R in general formula (7) 5 and R 6 same.

[0105]

[0106] Poly(meth)acrylate can be di(meth)acrylate or tri(meth)acrylate. As a light curing agent, di(meth)acrylate and tri(meth)acrylate can be used together, or a mixture of di(meth)acrylate and tri(meth)acrylate can be used.

[0107] R 6 Preferably, hydrogen atoms are used. That is, in compounds represented by general formula (7), j is preferably 0, k is preferably 1, and R is preferably 0. 5 Polyacrylates modified with alkylene oxides of isocyanurate containing hydrogen atoms, wherein R is particularly preferred. 4 Ethylene isocyanurate modified with ethylene oxide. Specific examples of ethyleneene isocyanurate modified with ethylene oxide include diacrylate of formula (5) and triacrylate of formula (6).

[0108]

[0109] While polyfunctional (meth)acrylates containing an isocyanuric acid backbone exhibit some compatibility with acrylic-based base polymers, they are not completely compatible systems. When the base polymer and the UV-curing agent are not completely compatible, the UV-curing agent tends to remain on the surface of the adhesive layer before UV curing (near the bonding interface with the adherend). This tendency of the UV-curing agent to remain at the bonding interface with the adherend easily leads to the formation of a weak-boundary layer (WBL). When a WBL forms, while maintaining the main properties of the adhesive layer such as storage modulus, the liquid properties of the surface (bonding interface) become stronger, thus tending to weaken the adhesion to the adherend, making the adhesive layer before UV curing easier to peel off from the adherend.

[0110] When a UV-curable layer with a WBL (Warehouse Block Layer) is formed, where the UV-curable is predominantly present near the adhesive interface with the adherend, the curing reaction of the UV-curable is more likely to occur near the adhesive interface where the UV-curable density is high. Therefore, the cohesive force near the adhesive interface tends to increase, and the adhesive strength tends to rise. Furthermore, in the case of a WBL, the increase in storage modulus, a key characteristic, tends to be suppressed in the UV-cured adhesive.

[0111] As described above, the compatibility between the acrylic base polymer and the polyfunctional (meth)acrylate containing an isocyanuric acid backbone can be controlled according to the composition of the acrylic base polymer, specifically the type of (meth)acrylate alkyl ester (molar average number of carbon atoms in the alkyl group). Even with a small amount of UV-curing agent, WBL (Wasteless Blue) formation is easily achieved, reducing the adhesive strength of the adhesive layer before UV curing. Furthermore, polyfunctional (meth)acrylates containing an isocyanuric acid backbone have a rigid structure, so even a small amount can be easily increased through UV curing, resulting in high adhesive strength.

[0112] That is, by using polyfunctional (meth)acrylates containing isocyanuric acid backbone as photocuring agents and controlling the composition of acrylic base polymers, it is possible to achieve both low adhesion before photocuring and high adhesion after photocuring, while reducing the energy storage modulus at low temperatures.

[0113] From the viewpoint of processability in preparing adhesive compositions and compatibility with acrylic-based polymers, a UV-curing agent is preferably a UV-curing agent that is liquid at room temperature. The triacrylate (tris(2-acryloyloxyethyl) isocyanurate) of formula (6) is solid at room temperature, but a mixture of the triacrylate of formula (6) and the diacrylate of formula (5) can be liquid at room temperature. Furthermore, the ε-caprolactone-modified triacrylate (in formula (7) where at least one k is 1 or more, R...) 4 (A compound containing pentylene) can be liquid at room temperature.

[0114] From the viewpoint of controlling the adhesive strength of the adhesive before and after photocuring and suppressing excessive increase in storage modulus, the content of polyfunctional (meth)acrylate containing an isocyanuric acid backbone in the adhesive composition is preferably 0.5 to 20 parts by weight, more preferably 0.7 to 15 parts by weight, and even more preferably 1 to 12 parts by weight, or 1.5 to 10 parts by weight, relative to 100 parts by weight of the acrylic base polymer. When using only polyfunctional (meth)acrylate containing an isocyanuric acid backbone as a photocuring agent, the content of polyfunctional (meth)acrylate containing an isocyanuric acid backbone 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, relative to 100 parts by weight of the acrylic base polymer.

[0115] (Other UV curing agents)

[0116] The adhesive composition may also contain a compound having photopolymerizable functional groups other than the polyfunctional (meth)acrylates containing the isocyanuric acid backbone described above as a photocuring agent. Other photocuring agents include photocurable monomers or photocurable oligomers. As a photopolymerizable functional group, an olefinic unsaturated bond is preferred, with (meth)acryloyl groups being the most preferred. Other photocuring agents may be photocuring agents having one photopolymerizable functional group or photocuring agents having two or more photopolymerizable functional groups.

[0117] As monofunctional photocuring agents with a single photopolymerizable functional group, various oligomers of alkyl (meth)acrylates, urethane (meth)acrylates, etc., can be listed. In addition to polyfunctional (meth)acrylates containing an isocyanuric acid backbone, monofunctional photocuring agents are also used as photocuring agents, which tends to reduce the adhesive strength of the adhesive before photocuring. Furthermore, by using monofunctional photocuring agents in combination, the distance between crosslinking points after photocuring increases, thus tending to reduce the storage modulus at low temperatures.

[0118] From the viewpoint of increasing the distance between crosslinking points and thus reducing the storage modulus of the adhesive layer at low temperatures after photocuring, oligomers with a molecular weight of 1000 or more are preferred as monofunctional photocuring agents. From the viewpoint of compatibility with acrylic-based polymers, the weight-average molecular weight of the oligomers used as monofunctional photocuring agents 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 increasing the adhesive strength of the adhesive layer after photocuring, urethane (meth)acrylates are preferred as oligomers.

[0119] When a monofunctional photocurable agent is used as a photocurable agent in addition to a polyfunctional (meth)acrylate containing an isocyanuric acid backbone, the content of the monofunctional photocurable agent relative to 100 parts by weight of the acrylic base polymer is preferably 1 to 45 parts by weight, more preferably 5 to 40 parts by weight, and may also be 10 to 35 parts by weight or 12 to 32 parts by weight. When a monofunctional photocurable agent is used as a photocurable agent in addition to a polyfunctional (meth)acrylate containing an isocyanuric acid backbone, the total amount of the photocurable agent relative to 100 parts by weight of the acrylic base polymer is preferably 3 to 50 parts by weight, and may also 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.

[0120] From the viewpoint of compatibility with acrylic-based polymers, multifunctional (meth)acrylates are preferred as photocuring agents having two or more photopolymerizable functional groups. In addition to multifunctional (meth)acrylates containing an isocyanuric acid backbone, multifunctional photocuring agents are also used, thereby sometimes allowing the adhesive strength of the adhesive before and after photocuring to be controlled within an appropriate range.

[0121] Polyfunctional (meth)acrylates are typically esters of polyols and (meth)acrylates. Specific examples of polyfunctional (meth)acrylates include: poly(meth)acrylates with alkylene oxide chains such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate; esters of diols and (meth)acrylates such as alkane diol di(meth)acrylate, tricyclodecanediethanol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, bis(trimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol poly(meth)acrylate, dipentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, and glycerol di(meth)acrylate; urethane (meth)acrylates, epoxy (meth)acrylates, butadiene (meth)acrylates, and isoprene (meth)acrylates.

[0122] Polyfunctional (meth)acrylates can be esters of polyols modified with alkylene oxides and (meth)acrylates. Examples of alkylene oxides include ethylene oxide (EO) and propylene oxide (PO). Alkylene oxides can be polyalkylene oxides of polyethylene glycol, polypropylene glycol, etc.

[0123] 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, pentaerythritol propylene oxide-modified tetra(meth)acrylate, etc.

[0124] From the viewpoint of compatibility with acrylic-based polymers, polyfunctional (meth)acrylates having alkylene oxide chains are preferred. 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 also be 110 to 350 or 120 to 300.

[0125] When a multifunctional photocurable agent is used as a photocurable agent in addition to a multifunctional (meth)acrylate containing an isocyanuric acid backbone, the content of the multifunctional photocurable agent other than the multifunctional (meth)acrylate containing an isocyanuric acid backbone is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, or may be 1 to 7 parts by weight or 1.5 to 5 parts by weight relative to 100 parts by weight of the acrylic base polymer. When a multifunctional photocurable agent is used as a photocurable agent in addition to a multifunctional (meth)acrylate containing an isocyanuric acid backbone, the total amount of the multifunctional photocurable agent, including the multifunctional (meth)acrylate containing an isocyanuric acid backbone, is preferably 1 to 20 parts by weight relative to 100 parts by weight of the acrylic base polymer, or 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.

[0126] <Photopolymerization Initiator>

[0127] Photopolymerization initiators generate active species upon irradiation with active light, promoting the curing reaction of the photocurable agent. Photopolymerization initiators include photocationic initiators (photoacid generators), photoradical initiators, and photoanionic initiators (photoalkali generators), depending on the type of photocurable agent. When using polyfunctional acrylates as photocurable agents, photoradical initiators are preferred. Photoradical initiators that generate free radicals through cleavage by visible light or ultraviolet light with wavelengths shorter than 450 nm are preferred; examples include hydroxyketones, benzoyldimethyl ketals, aminoketones, acylphosphine oxides, benzophenones, and triazine derivatives containing trichloromethyl. Photoradical initiators can be used alone or in combination of two or more.

[0128] 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, relative to 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, relative to 100 parts by weight of the total photocuring agent.

[0129] <Other Ingredients>

[0130] As described above, the photocurable adhesive composition constituting 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, within a range that does not impair the properties of the present invention.

[0131] [Fabrication of the reinforcing membrane]

[0132] A reinforced film can be obtained by laminating a photocurable adhesive layer 2 onto a membrane substrate 1. The adhesive layer 2 can be formed directly on the membrane substrate 1, or an adhesive layer formed as a sheet on another substrate can be transferred onto the membrane substrate 1.

[0133] The above-mentioned adhesive composition is applied to a substrate by means of roller coating, roller licking coating, gravure coating, reverse coating, roller brushing, spraying, dip roller coating, bar coating, doctor blade coating, air knife coating, curtain coating, die lip coating, and die coating, and the solvent is removed by drying as needed, thereby forming an adhesive layer. As a drying method, appropriate methods can be used. 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.

[0134] When the adhesive composition contains a crosslinking agent, crosslinking is preferably carried out by heating or aging during or after solvent drying. The heating temperature and time are appropriately set according to the type of crosslinking agent used, and crosslinking is typically carried out by heating for about 1 minute to 7 days in the range of 20°C to 160°C. The heating used for drying to remove the solvent can also be used for crosslinking.

[0135] After a cross-linking structure is introduced into the polymer using a cross-linking agent, the photocuring agent also remains in an unreacted state. Therefore, the adhesive layer 2 comprises an acrylic-based polymer with an introduced cross-linking structure, a photocuring agent, and a photopolymerization initiator. When the adhesive layer 2 is formed on the 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. Cross-linking can also be performed after attaching the release liner 5 to the adhesive layer 2.

[0136] When the adhesive layer 2 is formed on other substrates, after the solvent is dried, the adhesive layer 2 is transferred onto the film substrate 1, thereby obtaining a reinforced film. The substrate used in the formation of the adhesive layer can be left as is as a release liner 5.

[0137] As the release liner 5, a plastic film such as polyethylene, polypropylene, polyethylene terephthalate, or polyester film is preferably used. The thickness of the release liner is typically 3–200 μm, preferably around 10–100 μm. It is preferable to perform a release treatment on the contact surface between the release liner 5 and the adhesive layer 2 using a release agent such as a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based agent, or silica powder. By performing a release treatment on the surface of the release liner 5, when the membrane substrate 1 is peeled from the release liner 5, peeling occurs at the interface between the adhesive layer 2 and the release liner 5, maintaining the adhesive layer 2 adhered to the membrane substrate 1. Regarding the release liner 5, either the treated surface or the untreated surface, or both, can be treated with antistatic agents. By performing antistatic treatment on the release liner 5, the static charge generated when peeling the release liner from the adhesive layer can be suppressed.

[0138] [Physical properties of the adhesive layer]

[0139] From the viewpoint of easy peeling from the adhered object and preventing adhesive residue on the adhered object after peeling off the reinforcing film, the adhesion strength between the adhesive layer and the adhered object before light curing is preferably 3 N / 25 mm or less, more preferably 2.5 N / 25 mm or less, and may also be 2 N / 25 mm or less, 1.5 N / 25 mm or less, or 1 N / 25 mm or less. From the viewpoint of preventing peeling of the reinforcing film during storage and handling, the adhesion strength between the adhesive layer and the adhered object before light curing is preferably 0.01 N / 25 mm or more, more preferably 0.02 N / 25 mm or more, and may also be 0.03 N / 25 mm or more, 0.04 N / 25 mm or more, or 0.05 N / 25 mm or more.

[0140] When adhesive layer 2 is photocured, the photocuring agent undergoes a curing reaction, increasing the adhesion strength to the adherend. As described above, it is preferable that adhesive layer 2 has a low shear storage modulus at low temperatures after photocuring. From the viewpoint of adhesive reliability in practical use, the adhesion strength between the photocured adhesive layer and the adherend is preferably 7 N / 25 mm or more, more preferably 8 N / 25 mm or more, and may also be 9 N / 25 mm or more or 10 N / 25 mm or more.

[0141] The adhesion strength between the light-cured adhesive layer and the substrate is preferably more than twice the adhesion strength between the light-cured adhesive layer and the substrate, more preferably more than three times, and may also be more than 3.5 times, more than 4 times, more than 4.5 times, or more than 5 times.

[0142] The adhesive strength is determined by a peel test using a polyimide film as the substrate, a tensile speed of 300 mm / min, and a peel angle of 180°. Unless otherwise specified, the adhesive strength is the value measured at 25°C.

[0143] The photocured adhesive layer 2 exhibits low storage modulus and high adhesive strength at low temperatures. Therefore, even when the device with the reinforcing film is repeatedly bent or held in a bent state for extended periods, peeling of the adhesive layer at the bending points can be suppressed. As described above, by using a polyfunctional (meth)acrylate containing an isocyanuric acid backbone as a photocuring agent and adjusting the composition of the acrylic-based polymer, the adhesive composition can maintain the adhesive strength of the adhesive layer before and after photocuring within an appropriate range and reduce the storage modulus of the photocured adhesive layer at low temperatures.

[0144] [Use of reinforced membrane]

[0145] The reinforcing film of the present invention is used to bond to a device or a component of a device. In the reinforcing film 10, the adhesive layer 2 is bonded to the film substrate 1, and the adhesive force to the adherend is small after bonding to the adherend and before photocuring. Therefore, the adherend is easily peeled off from the reinforcing film before photocuring.

[0146] The substrate to which the reinforcing film is adhered is not particularly limited, and various electronic devices, optical devices, and their components can be listed. In one embodiment, the reinforcing film is adhered to the surface of a flexible device that can be bent, such as a foldable device or a rollable device. The foldable device has a hinge portion, which allows it to be bent around the hinge portion. When the device is a display device, the reinforcing film can be adhered to the surface on the screen side or the back side (housing). In flexible devices where the hinge portion and other predetermined parts are configured to be bent, the device is repeatedly bent and stretched at the same location during its use.

[0147] The reinforcing film can be applied to the entire surface of the substrate or selectively applied only to the areas requiring reinforcement (the areas to be reinforced). Alternatively, the reinforcing film can be applied to both the areas requiring reinforcement and the areas not requiring reinforcement (the non-reinforced areas), and then the reinforcing film applied to the non-reinforced areas can be cut and removed. If the adhesive is not light-cured, the reinforcing film is temporarily bonded to the surface of the substrate, making it easy to peel off. Alternatively, the reinforcing film can be applied to both the areas requiring reinforcement and the non-reinforced areas, and the adhesive can be light-cured selectively by irradiating the areas requiring reinforcement. Then, the reinforcing film on the uncured non-reinforced areas can be selectively peeled off.

[0148] By applying a reinforcing film, appropriate rigidity is imparted, thus improving handleability and preventing breakage for thin components such as flexible devices. In the device manufacturing process, the reinforcing film can be applied to semi-finished products, or to large-sized semi-finished products before being cut to product size. The reinforcing film can be applied roll-to-roll to the mother roll of a device manufactured using a roll-to-roll process.

[0149] After the reinforcing film is bonded to the adherend, the adhesive layer 2 is irradiated with active light, thereby photocuring the adhesive layer. Examples of active light include ultraviolet light, visible light, infrared light, X-rays, alpha rays, beta rays, and gamma rays. Considering both the ability to suppress curing of the adhesive layer in its storage state and its ease of curing, ultraviolet light is preferred. 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 can be performed from either the film substrate 1 side or the adherend side, or from both sides.

[0150] As described above, by applying the reinforcing film of the present invention, the adherend is given appropriate rigidity, and stress is relaxed and dispersed. Therefore, various defects that may occur during the manufacturing process can be suppressed, production efficiency can be improved, and yield can be increased. The reinforcing film is easily peeled off from the adherend before the adhesive layer is photocured, thus rework is easy even in cases of lamination or poor adhesion. Furthermore, selective removal of the reinforcing film from areas outside the area to be reinforced is also easy.

[0151] Even when the completed device is subjected to unexpected external forces such as being dropped, having heavy objects placed on it, or being struck by flying objects, damage can be prevented by the application of the reinforcing film. Furthermore, the reinforcing film, after being cured with adhesive, is firmly bonded to the device, making it resistant to peeling even after prolonged use, thus ensuring excellent reliability.

[0152] In devices with a reinforcing film that are bonded to a flexible device using a resin substrate, even when repeatedly bent and stretched or kept in a bent state for a long time, the reinforcing film is not prone to deformation such as wrinkles at the bending points or peeling off from the device, exhibiting excellent adhesion reliability.

[0153] [Example]

[0154] The following examples and comparative examples are provided for further illustration, but the present invention is not limited to these examples.

[0155] [Fabrication of adhesive layer and reinforcing film]

[0156] <Polymerization of Acrylic Polymers>

[0157] In a reaction vessel equipped with a thermometer, stirrer, reflux condenser, and nitrogen inlet, 100 parts by weight of the monomers shown in Table 1 (by weight), 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 introduced, and nitrogen replacement was carried out for about 1 hour with stirring. Then, the mixture was heated to 57°C and reacted for 6 hours to obtain a solution of acrylic polymers A to D.

[0158] <Preparation of Adhesive Compositions>

[0159] In a solution of an acrylic polymer (100 parts by weight in the form of the polymer solids), the types and amounts of photocuring agent, crosslinking agent, crosslinking catalyst, 0.3 parts by weight of IGMResins "Omnirad 651" as a photopolymerization initiator, and 0.3 parts by weight of 1-ethyl-3-methylimidazolium bisfluorosulfonylimide (Daiichi Kogyo Pharmaceutical Co., Ltd. "ELEXCEL AS-110") as an antistatic agent were added and mixed uniformly to prepare an adhesive composition.

[0160] In Examples 1-10 and Comparative Examples 1-4, 0.025 parts by weight of a difunctional isocyanate-based crosslinking agent (Asahi Kasei Corporation "DURANATE D101") was used as a crosslinking agent, and 0.05 parts by weight of iron acetylacetone (NACEM Iron (Ⅲ)) was used as a crosslinking catalyst. In Example 11, 0.025 parts by weight of a tetrafunctional epoxy-based crosslinking agent (Mitsubishi Gas Chemical Corporation "TETRAD C") was used as a crosslinking agent, and 0.05 parts by weight of zirconium tetraacetylacetone (Matsumoto Fine Chemical Corporation "ZC-150") was used as a crosslinking catalyst.

[0161] <Fabrication of Reinforcing Membrane>

[0162] The adhesive composition described above was applied to a 50 μm thick polyethylene terephthalate (PET) film using an applicator, resulting in a dried thickness of 18 μm. After drying at 130°C for 3 minutes to remove the solvent, the release liner (a 38 μm thick PET film with antistatic treatment on both sides and silicone release treatment on one side) was then bonded to the adhesive-coated side. The film was then subjected to an aging treatment at 50°C for 3 days to crosslink, resulting in a reinforcing film on which a photocurable adhesive sheet was laminated and a release liner was temporarily bonded.

[0163] [evaluate]

[0164] The following evaluation was performed on the reinforcing films obtained in the above embodiments and comparative examples.

[0165] <Storage modulus of the adhesive layer>

[0166] On the release liner, the adhesive composition was coated and crosslinked in the same manner as in the above-described embodiments / comparative examples to produce an adhesive sheet (before photocuring). A release liner was attached to the surface of the adhesive layer of the adhesive sheet before photocuring, isolating it from oxygen, and irradiated with a 365nm LED lamp at 1000mJ / cm². 2 The UV light was used to cure the adhesive. The cured adhesive sheets were stacked to make a test sample with a thickness of about 0.8 mm. The dynamic viscoelasticity was measured using a dynamic viscoelasticity measuring device (TA Instruments "ARES-G2") under the following conditions, and the value of the shear storage modulus G' at -20°C was read.

[0167] Deformation mode: Torsion.

[0168] Measurement frequency: 1Hz.

[0169] Heating rate: 5℃ / minute.

[0170] Measurement temperature: -70 to 100℃.

[0171] Shape: parallel plate 8.0mmφ.

[0172] <Adhesive strength>

[0173] A 25μm thick polyimide film (UBE "UPILEX25S") was attached to an SUS plate using double-sided adhesive tape (Nitto Denko "No. 531") to obtain a polyimide film substrate for testing. The release liner was removed from the surface of the reinforcing film, which was cut into 25mm wide x 100mm long sections. A hand roller was used to adhere the film to the polyimide film substrate for testing, creating a test sample before photocuring. Ultraviolet light was irradiated onto the reinforcing film side (PET film substrate side) of the pre-cured test sample to cure the adhesive layer, resulting in a sample used as the post-cured test sample. Using a Shimadzu "Autograph AGX-V2" chuck, the end of the reinforcing film substrate in the test sample was held, and the reinforcing film was peeled 180° at a stretching speed of 300mm / min. The peel strength was measured.

[0174] [Evaluation Results]

[0175] The composition of the adhesives for the reinforcing films of the Examples and Comparative Examples (composition of the acrylic polymer, and the type and amount of the UV-curing agent relative to 100 parts by weight of the solid component of the acrylic polymer), and the evaluation results are shown in Table 1. In Table 1, monomers and UV-curing agents are referred to by abbreviation. It should be noted that, among the UV-curing agents described below, A9300 is a solid at room temperature, while the other UV-curing agents are liquids at room temperature.

[0176] <Single>

[0177] BA: Butyl acrylate.

[0178] 2EHA: 2-Ethylhexyl acrylate.

[0179] NOAA: n-Octyl acrylate.

[0180] LA: Lauryl acrylate.

[0181] 4HBA: 4-hydroxybutyl acrylate.

[0182] AA: Acrylic acid.

[0183] <Light curing agent>

[0184] M923: Isocyanuric acid EO modified polyacrylate, difunctional to trifunctional (Dong-A Synthetic "Aronix M-923", with a diacrylate ratio of over 50%).

[0185] M935: Isocyanuric acid EO modified polyacrylate, difunctional to trifunctional (Dong-A Synthetic "Aronix M-935", triacrylate ratio is more than 50%).

[0186] M313: Isocyanuric acid EO modified polyacrylate, difunctional to trifunctional (Dong-A Synthetic "Aronix M-313", with a diacrylate ratio of 30% to 40%).

[0187] A9300: Isocyanuric acid EO modified triacrylate (New Nakamura Chemical Industry "NK ester A9300").

[0188] A9300-1CL: ε-caprolactone modified tris(2-acryloyloxyethyl) isocyanurate ("NK ester A9300-1CL" manufactured by Shin-Nakamura Chemical Industry).

[0189] A400: Polyethylene glycol #400 (n=9) diacrylate (New Nakamura Chemical Industry “NK ester A-400”, functional group equivalent 263g / eq).

[0190] A600: Polyethylene glycol #600 (n=14) diacrylate (New Nakamura Chemical Industry Co., Ltd. "NK ester A600", functional group equivalent 371g / eq).

[0191] LD301: Monofunctional urethane acrylate with a weight average molecular weight of 10,000 (AGC manufactures "U-FINE LD-301").

[0192]

[0193] The reinforcing film of Example 1, which uses an adhesive in which 3 parts by weight of an acrylate containing an isocyanuric acid backbone is incorporated into polymer A, which is based on NOAA as the main monomer, as a photocuring agent, has an adhesion strength of less than 3 N / 25 mm before photocuring and more than 7 N / 25 mm after photocuring. Furthermore, the photocured adhesive layer has a small storage modulus G' at low temperature (-20°C), exhibiting excellent properties for use in foldable devices.

[0194] Examples 5, 7, and 8, which varied the type of acrylate containing the isocyanuric acid backbone (the ratio of diacrylate to triacrylate), also exhibited the same excellent properties as Example 1. Example 9, which used an acrylate containing an isocyanuric acid backbone and had a chain ester structure introduced through ε-caprolactone modification, also showed the same excellent properties. A comparison of Examples 1, 5, 7, and 8 reveals a tendency for the storage modulus of the photocured adhesive layer to decrease at low temperatures as the ratio of triacrylate to diacrylate in the isocyanuric acid backbone decreases.

[0195] In Comparative Example 4, where the amount of acrylate containing an isocyanuric acid backbone as the UV curing agent was 0.5 parts by weight, the storage modulus at low temperature after UV curing was smaller than that of Example 1. However, in Comparative Example 4, the adhesive strength of the adhesive layer before UV curing was high, and even after UV curing, the adhesive strength did not increase; in fact, it decreased. Regarding Comparative Examples 2 and 3, which used polyethylene glycol diacrylate as the UV curing agent instead of acrylate containing an isocyanuric acid backbone, the increase in adhesive strength obtained by UV curing was insufficient compared to Examples 1, etc.

[0196] These results show that, as for acrylates containing an isocyanuric acid backbone used as photocuring agents, they have an excellent effect in reducing adhesion before photocuring and improving adhesion through photocuring.

[0197] In Example 11, which uses polymer D instead of polymer A and an epoxy-based crosslinker instead of an isocyanate-based crosslinker, although it exhibits higher adhesive strength compared to Example 1, it also shows a large low-temperature storage modulus after photocuring. The acrylic acid constituting polymer D has a higher glass transition temperature than the hydroxyl-containing monomer (4HBA), and the adhesive has higher cohesive strength; therefore, it can be considered that this affects the adhesive strength, storage modulus, and other physical properties.

[0198] In Example 10, where polymer B, with a higher molar average carbon number of the alkyl group of the alkyl acrylate, was used instead of polymer A, the low-temperature storage modulus decreased after photocuring compared to Example 1, but the adhesive strength was also lower. In Comparative Example 1, where polymer C, with a lower molar average carbon number of the alkyl group of the alkyl acrylate, was used, the adhesive strength before photocuring increased significantly compared to Example 1. These results suggest that the compatibility between the acrylic base polymer and the acrylate containing the isocyanuric acid backbone as the photocuring agent influences the adhesive strength of the adhesive layer before and after photocuring.

[0199] In Example 2, which used polyethylene glycol diacrylate as a UV curing agent in addition to the acrylate containing the isocyanuric acid backbone, compared with Example 1, the adhesion before UV curing was low, and the adhesion after UV curing was high, exhibiting excellent adhesive properties. The same trend was observed in the comparison between Examples 5 and 6. In Example 3, which changed the ratio of the acrylate containing the isocyanuric acid backbone to the polyethylene glycol diacrylate, compared with Example 1, the adhesion after UV curing was high, exhibiting excellent adhesive properties. Furthermore, compared with Example 1, Examples 2 and 3 showed smaller storage modulus values ​​for the UV-cured adhesive layer at low temperatures. Compared with Example 5, Example 6 showed a smaller storage modulus value for the UV-cured adhesive layer at low temperatures.

[0200] In Example 4, which used a monofunctional urethane acrylate oligomer in addition to an acrylate containing an isocyanuric acid backbone 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 photocured adhesive layer at low temperatures was lower than that in Example 1.

[0201] These results show that by using other photocurable compounds as photocuring agents in addition to acrylates containing isocyanuric acid backbones and adjusting their types and proportions, compared with the case of using only acrylates containing isocyanuric acid backbones as photocuring agents, it is possible to achieve improved adhesive properties and reduced low-temperature storage modulus (improved flexibility).

Claims

1. A reinforcing membrane comprising a membrane substrate and an adhesive layer laminated on a main surface of the membrane substrate, The adhesive layer is formed from a photocurable composition comprising an acrylic-based polymer, a photocuring agent as 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 relative to 100 parts by weight of the acrylic base polymer. The acrylic-based polymer comprises alkyl (meth)acrylates having chain-like alkyl groups, and one or more monomers selected from the group consisting of hydroxyl-containing monomers and carboxyl-containing monomers, wherein a cross-linking structure is introduced into the acrylic-based polymer. The photocuring agent comprises a polyfunctional (meth)acrylate containing an isocyanuric acid backbone. The adhesive layer, after photocuring, has a shear storage modulus of less than 100 kPa at -20°C.

2. The reinforcing membrane according to claim 1, wherein, The photocurable composition contains 0.5 to 20 parts by weight of the polyfunctional (meth)acrylate containing an isocyanuric acid backbone relative to 100 parts by weight of the acrylic base polymer.

3. The reinforcing membrane according to claim 1 or 2, wherein, In the alkyl (meth)acrylate monomers having chain-like alkyl groups that form the constituent monomers of the acrylic-based basic polymer, the molar average number of carbon atoms of the alkyl group is 5 or more and less than 10.

4. The reinforcing membrane according to claim 1 or 2, wherein, The most abundant monomer in the constituent monomers of the acrylic-based polymer is n-octyl acrylate.

5. The reinforcing membrane according to claim 1 or 2, wherein, The polyfunctional (meth)acrylate containing the isocyanuric acid skeleton is a compound represented by the following general formula (7). In general formula (7), Multiple j and multiple k are each an independent integer from 0 to 5. Multiple R 7 Each is independently an alkylene group having 2 to 6 carbon atoms. Multiple R 4 Each is independently an alkylene group having 2 to 4 carbon atoms. Multiple R 5 Each can be independently a hydrogen atom or a methyl group. R 6 It is a hydrogen atom or -CO-CR 5 =CH2.

6. The reinforcing membrane according to claim 1 or 2, wherein, The polyfunctional (meth)acrylate containing the isocyanuric acid skeleton is a compound represented by the following general formula (3). In general formula (3), Multiple k are independent integers from 0 to 5. Multiple R 4 Each is independently an alkylene group having 2 to 4 carbon atoms. Multiple R 5 Each can be independently a hydrogen atom or a methyl group. R 6 It is a hydrogen atom or -CO-CR 5 =CH2.

7. The reinforcing membrane according to claim 1 or 2, wherein, The adhesive layer has an adhesion force of less than 3N / 25mm to the polyimide film before photocuring.

8. The reinforcing membrane according to claim 1 or 2, wherein, The adhesive layer has an adhesion force of 7N / 25mm or more to the polyimide film after photocuring.

9. A device with a reinforcing film, wherein the reinforcing film is attached to the surface of a bendable device, wherein... The reinforcing membrane comprises a membrane substrate and an adhesive layer laminated on one main surface of the membrane substrate. The adhesive layer is bonded to the surface of the device. The adhesive layer is formed from a photocurable product obtained by photocuring a photocurable adhesive composition, the photocurable adhesive composition comprising an acrylic-based polymer, a photocuring agent as a compound having one or more photopolymerizable functional groups, and a photopolymerization initiator. The acrylic-based polymer comprises alkyl (meth)acrylates having chain-like alkyl groups, and one or more monomers selected from the group consisting of hydroxyl-containing monomers and carboxyl-containing monomers, wherein a cross-linking structure is introduced into the acrylic-based polymer. The photocuring agent comprises a polyfunctional (meth)acrylate containing an isocyanuric acid backbone. The shear storage modulus of the adhesive layer at -20°C is below 100 kPa.

10. The device with a reinforcing film according to claim 9, wherein, The polyfunctional (meth)acrylate containing the isocyanuric acid skeleton is a compound represented by the following general formula (7). In general formula (7), Multiple j and multiple k are each an independent integer from 0 to 5. Multiple R 7 Each is independently an alkylene group having 2 to 6 carbon atoms. Multiple R 4 Each is independently an alkylene group having 2 to 4 carbon atoms. Multiple R 5 Each can be independently a hydrogen atom or a methyl group. R 6 It is a hydrogen atom or -CO-CR 5 =CH2.

11. The device with a reinforcing film according to claim 9, wherein, The polyfunctional (meth)acrylate containing the isocyanuric acid skeleton is a compound represented by the following general formula (3). In general formula (3), Multiple k are independent integers from 0 to 5. Multiple R 4 Each is independently an alkylene group having 2 to 4 carbon atoms. Multiple R 5 Each can be independently a hydrogen atom or a methyl group. R 6 It is a hydrogen atom or -CO-CR 5 =CH2.

12. A method for manufacturing a device with a reinforcing film, comprising a method for manufacturing a device with a reinforcing film by attaching a reinforcing film to the surface of a bendable device, wherein, The adhesive layer of the reinforcing film as described in any one of claims 1 to 8 is bonded to the surface of the bendable device. The adhesive layer is photocured.

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