JP6581694B1 - Reinforcement film - Google Patents

Abstract

[PROBLEMS] To easily rework immediately after bonding to an adherend, to be firmly bonded to the adherend, and after bonding to the adherend, it is possible to arbitrarily set the time until the adhesive force is improved. Provide configurable reinforcing film. A reinforcing film (10) includes an adhesive layer (2) fixedly laminated on one main surface of a film substrate (1). The pressure-sensitive adhesive layer is composed of a photocurable composition containing a base polymer, a photocuring agent, a photoradical initiator, and an antioxidant, and 10 to 50 parts by weight of the photocuring agent with respect to 100 parts by weight of the base polymer. It contains 0.01 to 1 part by weight of a photo radical initiator and 0.01 to 2 parts by weight of an antioxidant. [Selection] Figure 1

Description

  The present invention relates to a reinforcing film to be stuck on a device surface.

  An adhesive film may be attached to the surface of an optical device such as a display or an electronic device for the purpose of surface protection or impact resistance. In such an adhesive film, an adhesive layer is usually fixedly laminated on the main surface of the film substrate, and the adhesive film is bonded to the device surface via the adhesive layer.

  In a state before use such as assembly, processing, and transportation of a device, the adherence film can be temporarily attached to the surface of the device or device component, thereby suppressing damage and damage to the adherend. Thus, the adhesive film temporarily attached for the purpose of temporary protection of the surface is required to be easily peeled off from the adherend and no adhesive residue is generated on the adherend.

  Patent Document 1 discloses a pressure-sensitive adhesive film that is used while being attached to a device surface even when the device is used, in addition to assembling, processing, and transporting the device. Such an adhesive film has a function of reinforcing the device by dispersing the impact to the device and imparting rigidity to the flexible device in addition to the surface protection.

  When the adhesive film is bonded to the adherend, bonding failure such as mixing of bubbles or displacement of the bonding position may occur. When a bonding failure occurs, an adhesive film is peeled from the adherend and another adhesive film is bonded (rework). Since the adhesive film used as the process material is designed on the premise of peeling from the adherend, rework is easy. On the other hand, a reinforcing film premised on permanent adhesion is generally not assumed to be peeled off from the device, and is firmly adhered to the surface of the device, so that rework is difficult.

  Patent Document 2 discloses a pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) designed so as to have low adhesiveness immediately after being bonded to an adherend and to increase the adhesive force over time. The pressure-sensitive adhesive film in which such a pressure-sensitive adhesive layer is fixed and laminated on the film base is easy to peel off from the adherend immediately after being bonded to the adherend, and after a predetermined time has elapsed, Since it adheres firmly, it can be used as a reinforcing film having reworkability.

JP 2017-132777 A WO2015 / 163115 pamphlet

  It is difficult to say that the reinforcing film whose adhesive force with the adherend changes with time has sufficient flexibility with respect to the lead time of the process. For example, a reinforcing film including a pressure-sensitive adhesive layer whose adhesive strength increases with time is subjected to inspection and rework of the bonded state within a predetermined time until the adhesive strength increases after being bonded to an adherend. There is a need. In addition, when a reinforcing film is bonded to the entire surface of a device or device component and then the reinforcing film is removed from a part of the region, it is necessary to perform the processing until the adhesive force increases. is there.

  In view of the above, according to the present invention, rework is easy immediately after bonding with an adherend, and the time until the adhesive force is improved after bonding with the adherend can be arbitrarily set and bonded. An object is to provide a reinforcing film that can be firmly bonded to an adherend by improving the strength.

  The reinforcing film of the present invention includes an adhesive layer fixedly laminated on one main surface of a film substrate. The pressure-sensitive adhesive layer is composed of a photocurable composition containing a base polymer, a photocuring agent, a photoradical initiator, and an antioxidant. The photocurable composition constituting the pressure-sensitive adhesive layer is 10 to 50 parts by weight of the photocuring agent, 0.01 to 1 part by weight of the photoradical initiator, and 0% of the antioxidant with respect to 100 parts by weight of the base polymer. It is preferable to contain 0.01-2 weight part. The content of the antioxidant in the photocurable composition is preferably 0.2 to 5 times the content of the photo radical initiator.

  From the viewpoint of suppressing generation of radicals from a photo radical initiator by light such as a fluorescent lamp, the photo radical initiator has an absorption maximum in a wavelength range of 310 nm to 355 nm and an absorption maximum at a wavelength longer than 360 nm. Those not showing are preferably used.

  As the base polymer of the pressure-sensitive adhesive layer, for example, an acrylic polymer is used. The acrylic polymer preferably contains 5 to 50% by weight of a monomer component having a homopolymer glass transition temperature of 40 ° C. or higher.

  It is preferable that a crosslinked structure is introduced into the base polymer of the pressure-sensitive adhesive layer. For example, the base polymer contains a hydroxy group-containing monomer and / or a carboxy group-containing monomer as a monomer unit, and a crosslinking structure such as a polyfunctional isocyanate compound or a polyfunctional epoxy compound is bonded to these functional groups to form a crosslinked structure. Is introduced.

  The photocuring agent for the pressure-sensitive adhesive layer is, for example, polyfunctional (meth) acrylate. The functional group equivalent of the photocuring agent is preferably about 100 to 500 g / eq.

  The reinforcing film preferably has an adhesive force with the polyimide film of 0.005 to 5 N / 25 mm. After photocuring the pressure-sensitive adhesive layer, the adhesive force between the reinforcing film and the polyimide film is preferably 6 N / 25 mm or more.

  In the reinforcing film of the present invention, the pressure-sensitive adhesive layer is made of a photocurable composition, and the pressure-sensitive adhesive layer is photocured after adhesion to the adherend, thereby increasing the adhesive force with the adherend. Since the adhesive strength with the adherend is small before photocuring, rework is easy, and after photocuring, the adhesive strength is high, which contributes to device reinforcement and improved reliability. The photocurable pressure-sensitive adhesive can arbitrarily set the curing timing after being bonded to the adherend. In addition, the pressure-sensitive adhesive composition contains an antioxidant in addition to the base polymer, photocuring agent and photoradical initiator, thereby suppressing photocuring reactions caused by light from fluorescent lamps in the storage environment. Is done. For this reason, the reinforcing film can be stored for a long period of time before being bonded to the adherend and before being photocured after being bonded to the adherend. Therefore, the reinforcing film of the present invention has an advantage that it can flexibly cope with the lead time of the process.

It is sectional drawing which shows the laminated structure of a reinforcement film. It is sectional drawing which shows the laminated structure of a reinforcement film. It is sectional drawing which shows the device with which the reinforcement film was stuck. It is a graph showing the measurement result of the radical production amount by light irradiation at a cryogenic temperature.

  FIG. 1 is a cross-sectional view illustrating an embodiment of a reinforcing film. The reinforcing film 10 includes an adhesive layer 2 on one main surface of the film substrate 1. The pressure-sensitive adhesive layer 2 is fixedly laminated on one main surface of the base film 1. The pressure-sensitive adhesive layer 2 is a photo-curable pressure-sensitive adhesive made of a photo-curable composition, and is cured by irradiation with actinic rays such as ultraviolet rays, thereby increasing the adhesive force with the adherend.

  FIG. 2 is a cross-sectional view of a reinforcing film in which a separator 5 is temporarily attached on the main surface of the pressure-sensitive adhesive layer 2. FIG. 3 is a cross-sectional view showing a state in which the reinforcing film 10 is stuck on the surface of the device 20.

  The separator 5 is peeled and removed from the surface of the pressure-sensitive adhesive layer 2, and the exposed surface of the pressure-sensitive adhesive layer 2 is bonded to the surface of the device 20, whereby the reinforcing film 10 is bonded to the surface of the device 20. In this state, the pressure-sensitive adhesive layer 2 is before photocuring, and the reinforcing film 10 (pressure-sensitive adhesive layer 2) is temporarily attached on the device 20. By photocuring the pressure-sensitive adhesive layer 2, the adhesive force at the interface between the device 20 and the pressure-sensitive adhesive layer 2 is increased, and the device 20 and the reinforcing film 10 are fixed.

  “Fixed” refers to a state in which two laminated layers are firmly bonded and peeling at the interface between them is impossible or difficult. “Temporary attachment” is a state in which the adhesive force between two laminated layers is small and can be easily peeled off at the interface between the two layers.

  In the reinforcing film shown in FIG. 2, the film base 1 and the pressure-sensitive adhesive layer 2 are fixed, and the separator 5 is temporarily attached to the pressure-sensitive adhesive layer 2. When the film substrate 1 and the separator 5 are peeled off, peeling occurs at the interface between the pressure-sensitive adhesive layer 2 and the separator 5, and the state where the pressure-sensitive adhesive layer 2 is fixed on the film base material 1 is maintained. No adhesive remains on the separator 5 after peeling.

  In the device on which the reinforcing film 10 shown in FIG. 3 is pasted, the device 20 and the pressure-sensitive adhesive layer 2 are temporarily attached before the pressure-sensitive adhesive layer 2 is photocured. When the film substrate 1 and the device 20 are peeled off, peeling occurs at the interface between the pressure-sensitive adhesive layer 2 and the device 20, and the state where the pressure-sensitive adhesive layer 2 is fixed on the film base material 1 is maintained. Since no adhesive remains on the device 20, rework is easy. Since the adhesive force between the pressure-sensitive adhesive layer 2 and the device 20 is increased after photocuring the pressure-sensitive adhesive layer 2, it is difficult to peel the film 1 from the device 20. Destruction may occur.

[Film substrate]
As the film substrate 1, a plastic film is used. In order to fix the film base material 1 and the pressure-sensitive adhesive layer 2, it is preferable that the surface of the film base material 1 with the pressure-sensitive adhesive layer 2 is not subjected to release treatment.

The thickness of the film substrate is, for example, about 4 to 500 μm. From the viewpoint of reinforcing the device by imparting rigidity or reducing impact, the thickness of the film substrate 1 is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 45 μm or more. From the viewpoint of imparting flexibility to the reinforcing film and improving handling properties, the thickness of the film substrate 1 is preferably 300 μm or less, and more preferably 200 μm or less. From the viewpoint of achieving both flexibility and mechanical strength, compressive strength of the film substrate 1 is preferably 100~3000kg / cm ^2, more preferably ^{200~2900kg / cm 2, 300~2800kg / cm} 2 and more 400 to 2700 kg / cm ² is particularly preferable.

  Examples of the plastic material constituting the film substrate 1 include polyester resins, polyolefin resins, cyclic polyolefin resins, polyamide resins, and polyimide resins. In a reinforcing film for an optical device such as a display, the film substrate 1 is preferably a transparent film. Moreover, when irradiating actinic light from the film base material 1 side and performing photocuring of the adhesive layer 2, it is preferable that the film base material 1 has transparency with respect to the actinic light used for hardening of an adhesive layer. . Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are preferably used because they have both mechanical strength and transparency. When irradiating actinic rays from the adherend side, the adherend need only have transparency to actinic rays, and the film substrate 1 may not be transparent to actinic rays.

  The surface of the film substrate 1 may be provided with a functional coating such as an easy adhesion layer, an easy slip layer, a release layer, an antistatic layer, a hard coat layer, and an antireflection layer. In addition, in order to adhere the film base material 1 and the adhesive layer 2 as mentioned above, it is preferable that the release layer is not provided in the surface with the adhesive layer 2 of the film base material 1 provided.

[Adhesive layer]
The pressure-sensitive adhesive layer 2 fixedly laminated on the film substrate 1 is a photocurable composition containing a base polymer, a photocuring agent and a photoradical initiator. When the reinforcing film is used in an optical device such as a display, the total light transmittance of the pressure-sensitive adhesive layer 2 is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. The haze of the pressure-sensitive adhesive layer 2 is preferably 2% or less, more preferably 1% or less, still more preferably 0.7% or less, and particularly preferably 0.5% or less.

  Since the adhesive layer 2 has a low adhesive force with the adherend before photocuring, rework is easy. When the pressure-sensitive adhesive layer 2 is irradiated with actinic rays such as ultraviolet rays, radicals are generated from the photoradical initiator, and the adhesive force with the adherend is improved by radical polymerization reaction (photocuring) of the photocuring agent. Therefore, at the time of use of the device, the reinforcing film is difficult to peel off from the device surface, and the adhesion reliability is excellent.

  The photocurable adhesive is cured by irradiation with ultraviolet rays or the like. Therefore, the pressure-sensitive adhesive layer 2 made of a photo-curable pressure-sensitive adhesive composition has an advantage that the timing of curing can be arbitrarily set and the lead time of the process can be flexibly dealt with. On the other hand, radicals may be generated from a photoradical initiator by light from a fluorescent lamp or the like in a storage environment before use of the reinforcing film or before photocuring after bonding the reinforcing film to the adherend. is there.

  Since the amount of radicals generated by light from a fluorescent lamp or the like is sufficiently smaller than the amount of radicals generated by ultraviolet irradiation during photocuring, the photocuring reaction hardly proceeds even when left under a fluorescent lamp for a short time. However, if the reinforcing film is stored under a fluorescent lamp for a long period of time, the integrated amount of radicals generated from the photoradical initiator by the light of the fluorescent lamp increases, and the influence may not be negligible. Specifically, polymerization of the photocuring agent proceeds due to radicals generated from the photoradical initiator, and the adhesive force of the pressure-sensitive adhesive is increased, which may make it difficult to peel the reinforcing film from the adherend. Moreover, due to the deactivation of the photo radical initiator due to long-term storage, photocuring does not proceed even when irradiated with ultraviolet rays, and the adhesive force may not increase.

  In the reinforcing film of the present invention, the photocurable composition constituting the pressure-sensitive adhesive layer 2 contains an antioxidant in addition to the base polymer, the photocuring agent and the photoradical initiator. By using a photo radical initiator and an antioxidant together, even when the reinforcing film is stored under a fluorescent lamp for a long period of time, the adhesive force change is small, and the adhesive force can be increased appropriately during light irradiation. It becomes.

<Composition of adhesive>
Hereinafter, preferable modes of the base polymer, the photocuring agent, the photoradical initiator, and the antioxidant constituting the photocurable composition will be described in order.

(Base polymer)
The base polymer is the main component of the pressure-sensitive adhesive composition. The type of the base polymer is not particularly limited, and an acrylic polymer, a silicone polymer, a urethane polymer, a rubber polymer, or the like may be appropriately selected. In particular, the pressure-sensitive adhesive composition preferably contains an acrylic polymer as the base polymer because it is excellent in optical transparency and adhesiveness, and the adhesiveness is easily controlled. % Or more is preferably an acrylic polymer.

  As the acrylic polymer, a polymer containing a (meth) acrylic acid alkyl ester as a main monomer component is preferably used. In the present specification, “(meth) acryl” means acryl and / or methacryl.

  As the (meth) acrylic acid alkyl ester, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is suitably used. The alkyl group of the (meth) acrylic acid alkyl ester may be linear or branched. Examples of (meth) acrylic acid alkyl esters 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- (meth) acrylic acid 2- Ethylhexyl, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate , Dodecyl (meth) acrylate, isotridodecyl (meth) acrylate Tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate, pentadecyl (meth) acrylate, cetyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, iso (meth) acrylate Examples include octadecyl, nonadecyl (meth) acrylate, aralkyl (meth) acrylate, and the like.

  The content of the (meth) acrylic acid alkyl ester is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 55% by weight or more based on the total amount of monomer components constituting the base polymer.

  The acrylic base polymer preferably contains a monomer component having a crosslinkable functional group as a copolymerization component. Examples of the monomer having a crosslinkable functional group include a hydroxy group-containing monomer and a carboxy group-containing monomer. The hydroxy group and carboxy group of the base polymer serve as a reaction point with a crosslinking agent described later. For example, when an isocyanate-based crosslinking agent is used, it is preferable to contain a hydroxy group-containing monomer as a copolymer component of the base polymer. When using an epoxy-based crosslinking agent, it is preferable to contain a carboxy group-containing monomer as a copolymer component of the base polymer. By introducing a crosslinked structure into the base polymer, the cohesive force is improved, the adhesive force of the pressure-sensitive adhesive layer 2 is improved, and the adhesive residue on the adherend during reworking tends to be reduced.

  Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, (meth) Examples include 8-hydroxyoctyl acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 4- (hydroxymethyl) cyclohexyl) methyl (meth) acrylate, and the like. Examples of the carboxy group-containing monomer include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate carboxypentyl, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

  In the acrylic base polymer, the total amount of the hydroxy group-containing monomer and the carboxy group-containing monomer relative to the total amount of the constituent monomer components is preferably 1 to 30% by weight, more preferably 3 to 25% by weight, More preferably, it is 20% by weight. In particular, the content of the (meth) acrylic acid ester containing a hydroxy group is preferably in the above range.

  Acrylic base polymers include N-vinyl pyrrolidone, methyl vinyl pyrrolidone, vinyl pyridine, vinyl piperidone, vinyl pyrimidine, vinyl piperazine, vinyl pyrazine, vinyl pyrrole, vinyl imidazole, vinyl oxazole, vinyl morpholine, N-acryloyl morpholine as constituent monomer components. It is preferable to contain nitrogen-containing monomers such as N-vinylcarboxylic acid amides and N-vinylcaprolactam. The acrylic base polymer containing a nitrogen-containing monomer component exhibits appropriate water absorption in a moist heat environment and suppresses local water absorption of the adhesive, so that local whitening of the adhesive layer, local swelling, Contributes to prevention of peeling and the like.

  In the acrylic base polymer, the content of the nitrogen-containing monomer with respect to the total amount of the constituent monomer components is preferably 1 to 30% by weight, more preferably 3 to 25% by weight, and 5 to 20% by weight. Is more preferable. The acrylic base polymer preferably contains N-vinylpyrrolidone in the above range as a nitrogen-containing monomer.

  When the acrylic base polymer contains both a hydroxy group-containing monomer and a nitrogen-containing monomer as monomer components, the cohesive force and transparency of the pressure-sensitive adhesive tend to be improved. In the acrylic base polymer, the total amount of the hydroxy group-containing monomer and the nitrogen-containing monomer with respect to the total amount of the constituent monomer components is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, and 15 to 35% by weight. % Is more preferable.

  The acrylic base polymer may contain monomer components other than those described above. Acrylic base polymer contains, for example, cyano group-containing monomer, vinyl ester monomer, aromatic vinyl monomer, epoxy group-containing monomer, vinyl ether monomer, sulfo group-containing monomer, phosphate group-containing monomer, acid anhydride group-containing monomer component A monomer or the like may be contained.

  The adhesive properties of the pressure-sensitive adhesive before photocuring are likely to depend on the constituent components and molecular weight of the base polymer. The higher the molecular weight of the base polymer, the harder the adhesive. The weight average molecular weight of the acrylic base polymer is preferably 100,000 to 5,000,000, more preferably 300,000 to 3,000,000, and further preferably 500,000 to 2,000,000. When a crosslinked structure is introduced into the base polymer, the molecular weight of the base polymer refers to the molecular weight before introducing the crosslinked structure.

  There exists a tendency for an adhesive to become hard, so that there is much content of the high Tg monomer component in the structural component of a base polymer. The high Tg monomer means a monomer having a high glass transition temperature (Tg) of the homopolymer. Monomers having a homopolymer Tg of 40 ° C. or higher include dicyclopentanyl methacrylate (Tg: 175 ° C.), dicyclopentanyl acrylate (Tg: 120 ° C.), isobornyl methacrylate (Tg: 173 ° C.), (Meth) acrylic monomers such as nyl acrylate (Tg: 97 ° C), methyl methacrylate (Tg: 105 ° C), 1-adamantyl methacrylate (Tg: 250 ° C), 1-adamantyl acrylate (Tg: 153 ° C); acryloylmorpholine (Tg: 145 ° C), dimethylacrylamide (Tg: 119 ° C), diethylacrylamide (Tg: 81 ° C), dimethylaminopropylacrylamide (Tg: 134 ° C), isopropylacrylamide (Tg: 134 ° C), hydroxyethylacrylamide ( g: 98 ° C.) amide group-containing vinyl monomers such as; N- vinylpyrrolidone (Tg: 54 ℃), and the like.

  In the acrylic base polymer, the content of the monomer having a Tg of 40 ° C. or higher is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, based on the total amount of the constituent monomer components. . In order to form an adhesive layer having an appropriate hardness and excellent reworkability, it is preferable that the monomer component of the base polymer includes a monomer component having a Tg of 80 ° C. or higher as the homopolymer Tg. More preferably, it contains a monomer component at 100 ° C. or higher. In the acrylic base polymer, the content of the monomer having a Tg of 100 ° C. or more with respect to the total amount of the constituent monomer components is preferably 0.1% by weight or more, and more preferably 0.5% by weight or more. It is more preferably 1% by weight or more, and particularly preferably 3% by weight or more. In particular, the content of methyl methacrylate is preferably in the above range.

  An acrylic polymer as a base polymer is obtained by polymerizing the monomer component by various known methods such as solution polymerization, emulsion polymerization, bulk polymerization and the like. The solution polymerization method is preferable from the viewpoint of balance of properties such as adhesive strength and holding strength of the pressure-sensitive adhesive and cost. As a solvent for solution polymerization, ethyl acetate, toluene or the like is used. The solution concentration is usually about 20 to 80% by weight. As the polymerization initiator used for the solution polymerization, various known ones such as an azo type and a peroxide type can be used. In order to adjust the molecular weight, a chain transfer agent may be used. The reaction temperature is usually about 50 to 80 ° C., and the reaction time is usually about 1 to 8 hours.

(Crosslinking agent)
From the viewpoint of giving the adhesive an appropriate cohesive force, it is preferable that a crosslinked structure is introduced into the base polymer. For example, a cross-linking structure is introduced by adding a cross-linking agent to the solution after polymerizing the base polymer and heating as necessary. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a carbodiimide crosslinking agent, and a metal chelate crosslinking agent. These crosslinking agents react with functional groups such as hydroxy groups and carboxy groups introduced into the base polymer to form a crosslinked structure. An isocyanate-based crosslinking agent and an epoxy-based crosslinking agent are preferred because they are highly reactive with the hydroxy group and carboxy group of the base polymer and can easily introduce a crosslinked structure.

  As the isocyanate-based crosslinking agent, polyisocyanate having two or more isocyanate groups in one molecule is used. Examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; 2,4-tolylene diene. Aromatic isocyanates such as isocyanate, 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate; trimethylolpropane / tolylene diisocyanate trimer adduct (for example, “Coronate L” manufactured by Tosoh), trimethylolpropane / hexamethylene Diisocyanate trimer adduct (for example, “Coronate HL” manufactured by Tosoh), trimethylolpropane adduct of xylylene diisocyanate (for example, manufactured by Mitsui Chemicals) Takenate D110N ", isocyanurate of hexamethylene diisocyanate (e.g., manufactured by Tosoh" Coronate HX ") isocyanate adducts of the like.

  As the epoxy-based crosslinking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule is used. The epoxy group of the epoxy crosslinking agent may be a glycidyl group. Examples of the epoxy-based crosslinking agent 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, penta Erythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl Ether, adipic acid diglycidyl ester, o- phthalic acid diglycidyl ester, triglycidyl - tris (2-hydroxyethyl) isocyanurate, resorcin diglycidyl ether, bisphenol -S- diglycidyl ether, and the like. Commercially available products such as “Denacol” manufactured by Nagase ChemteX and “Tetrad X” and “Tetrad C” manufactured by Mitsubishi Gas Chemical may be used as the epoxy crosslinking agent.

  What is necessary is just to adjust the usage-amount of a crosslinking agent suitably according to a composition, molecular weight, etc. of a base polymer. The amount of the crosslinking agent used is about 0.1 to 10 parts by weight, preferably 0.3 to 7 parts by weight, more preferably 0.5 to 5 parts by weight, and still more preferably 100 parts by weight of the base polymer. Is 1 to 4 parts by weight. Further, the value obtained by dividing the amount (parts by weight) of the crosslinking agent used relative to 100 parts by weight of the base polymer by the functional group equivalent (g / eq) of the crosslinking agent is preferably 0.00015 to 0.11, preferably 0.001 to 0 0.077 is more preferable, 0.003 to 0.055 is more preferable, and 0.0045 to 0.044 is particularly preferable. The amount of cross-linking agent used is larger than that of general acrylic optical transparent adhesives, and the adhesive has an appropriate hardness, reducing the amount of adhesive residue on the adherend during rework and reworking. Tend to improve.

  A crosslinking catalyst may be used to promote the formation of a crosslinked structure. For example, as a crosslinking catalyst for an isocyanate-based crosslinking agent, a metal-based crosslinking catalyst (particularly a tin-based crosslinking catalyst) such as tetra-n-butyl titanate, tetraisopropyl titanate, ferric nasem, butyltin oxide, dioctyltin dilaurate, etc. may be mentioned. It is done. The amount of the crosslinking catalyst used is generally 0.05 parts by weight or less with respect to 100 parts by weight of the base polymer.

(Photocuring agent)
The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer 2 contains a photocuring agent in addition to the base polymer. When the pressure-sensitive adhesive layer 2 made of the photocurable pressure-sensitive adhesive composition is subjected to photocuring after being bonded to the adherend, the adhesive force with the adherend is improved.

  As the photocuring agent, a compound having two or more ethylenically unsaturated bonds in one molecule is preferable. Moreover, the photocuring agent is preferably a compound showing compatibility with the base polymer. In view of moderate compatibility with the base polymer, the photocuring agent is preferably liquid at room temperature. When the photocuring agent is compatible with the base polymer and is uniformly dispersed in the composition, the contact area with the adherend can be secured, and the highly adhesive layer 2 can be formed. In addition, when the base polymer and the photocuring agent have appropriate compatibility, a cross-linked structure is easily introduced into the pressure-sensitive adhesive layer 2 after photocuring, and the adhesive force with the adherend is appropriately increased. Tend.

  The compatibility between the base polymer and the photocuring agent is mainly influenced by the structure of the compound. The structure and compatibility of the compound can be evaluated by, for example, the Hansen solubility parameter, and the compatibility tends to increase as the difference in the solubility parameter between the base polymer and the photocuring agent decreases.

  Since the compatibility with the acrylic base polymer is high, it is preferable to use a polyfunctional (meth) acrylate as a photocuring agent. Polyfunctional (meth) acrylates include polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, bisphenol A ethylene oxide modified di (meth) acrylate, bisphenol A propylene oxide Modified di (meth) acrylate, alkanediol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, ethoxylated isocyanuric acid tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol di ( (Meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaerythritol La (meth) acrylate, pentaerythrole tetra (meth) acrylate, dipentaerystol poly (meth) acrylate, dipentaerythrole hexa (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate , Urethane (meth) acrylate, epoxy (meth) acrylate, butadiene (meth) acrylate, isoprene (meth) acrylate, and the like. Among these, polyethylene glycol di (meth) acrylate or polypropylene glycol di (meth) acrylate is preferable, and polyethylene glycol di (meth) acrylate is particularly preferable because of excellent compatibility with the acrylic base polymer.

  The compatibility between the base polymer and the photocuring agent also depends on the molecular weight of the compound. The smaller the molecular weight of the photocurable compound, the higher the compatibility with the base polymer. In light of compatibility with the base polymer, the molecular weight of the photocuring agent is preferably 1500 or less, more preferably 1000 or less, still more preferably 500 or less, and particularly preferably 400 or less.

  In the pressure-sensitive adhesive layer 2 before photocuring, the characteristics of the base polymer are the main controlling factors of adhesiveness. Therefore, if the base polymer of the pressure-sensitive adhesive composition is the same, the difference in adhesive properties of the pressure-sensitive adhesive layer before photocuring is small even if the type of photocuring agent is different. The kind and content of the photocuring agent mainly affect the adhesive force of the pressure-sensitive adhesive layer after photocuring. As the functional group equivalent is smaller (that is, the number of functional groups per unit molecular weight is larger) and the content of the photocuring agent is larger, the difference in adhesive strength can be provided before and after photocuring.

  From the viewpoint of high compatibility with the base polymer and improving the adhesive strength after photocuring, the functional group equivalent (g / eq) of the photocuring agent is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less. 200 or less is particularly preferable. On the other hand, if the functional group equivalent of the photocuring agent is too small, the crosslink point density of the pressure-sensitive adhesive layer after photocuring is increased, and the adhesiveness may be lowered. Therefore, the functional group equivalent of the photocuring agent is preferably 80 or more, more preferably 100 or more, and further preferably 130 or more.

  In the combination of an acrylic base polymer and a polyfunctional acrylate photocuring agent, when the functional group equivalent of the photocuring agent is small, the interaction between the base polymer and the photocuring agent is strong and the initial adhesive force tends to increase. . In the application of the present invention, an excessive increase in the initial adhesive force may lead to a decrease in reworkability. Also from the viewpoint of maintaining the adhesive force between the pressure-sensitive adhesive layer 2 before photocuring and the adherend within an appropriate range, the functional group equivalent of the photocuring agent is preferably within the above range.

  As for content of the photocuring agent in an adhesive composition, 10-50 weight part is preferable with respect to 100 weight part of base polymers. By making the compounding quantity of a photocuring agent into the said range, the adhesiveness of the adhesive layer after photocuring and a to-be-adhered body can be adjusted to a suitable range. The content of the photocuring agent is more preferably 15 to 45 parts by weight, and still more preferably 20 to 40 parts by weight with respect to 100 parts by weight of the base polymer.

(Photo radical initiator)
The photoradical initiator generates radicals upon irradiation with actinic rays, and promotes radical polymerization reaction of the photocuring agent by radical transfer from the photoradical initiator to the photocuring agent. As the photo radical initiator (photo radical generator), those that generate radicals by irradiation with visible light or ultraviolet light having a wavelength shorter than 450 nm are preferable. Hydroxy ketones, benzyl dimethyl ketals, amino ketones, acylphosphine Examples thereof include oxides, benzophenones, and trichloromethyl group-containing triazine derivatives. A radical photoinitiator may be used independently and may be used in mixture of 2 or more types.

When transparency is required for the pressure-sensitive adhesive layer 2, the photo radical initiator preferably has a low sensitivity to light having a wavelength longer than 400 nm (visible light). For example, the extinction coefficient at a wavelength of 405 nm is 1 × 10 ² [ mLg ^-1 cm ^-1] photoradical initiator or less is preferably used. In addition, when a photoradical initiator having low sensitivity to visible light is used, the storage stability of the reinforcing film can be improved because the amount of photoradical generated due to external light in the storage environment is small.

  From the viewpoint of enhancing the storage stability of the reinforcing film, it is preferable to use a photo radical initiator that does not exhibit an absorption maximum at a wavelength longer than 360 nm. A photo radical initiator exhibiting an absorption maximum at a wavelength longer than 360 nm easily absorbs ultraviolet rays (mainly mercury emission lines of 365 nm and 405 nm) from a fluorescent lamp to generate photo radicals. When the maximum wavelength of light absorption of the photoradical initiator is 360 nm or less, the amount of radicals generated due to light in a storage environment such as a fluorescent lamp is small. Therefore, even when the reinforcing film is exposed to a fluorescent lamp for a long time, the effective concentration of the photo radical initiator can be maintained high. Moreover, since a small amount of radicals generated due to light in a storage environment such as a fluorescent lamp are trapped by the antioxidant, photopolymerization in the storage environment is suppressed.

  In order to have high storage stability and to improve the adhesive force with the adherend by light irradiation even after long-term storage, the photoradical initiator contained in the pressure-sensitive adhesive layer has a maximum light absorption wavelength of 355 nm or less. Preferably there is. On the other hand, in order to increase the photocuring efficiency by ultraviolet irradiation, the photoradical initiator preferably has a light absorption maximum at a wavelength longer than 310 nm. From the above, in order to improve the storage stability of the reinforcing film, the photoradical initiator contained in the pressure-sensitive adhesive layer 2 does not have an absorption maximum at a wavelength longer than the wavelength of 360 nm and has a wavelength range of 310 to 355 nm. Those having an absorption maximum in the range are preferred. The absorption maximum wavelength of the photo radical initiator is more preferably 315 to 350 nm, and further preferably 320 to 340 nm.

  The content of the photo radical initiator in the pressure-sensitive adhesive layer 2 is preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.7 part by weight, with respect to 100 parts by weight of the base polymer. 0.5 parts by weight is more preferable. The content of the photo radical initiator in the pressure-sensitive adhesive layer 2 is preferably 0.005 to 0.5 parts by weight, more preferably 0.01 to 0.4 parts by weight, with respect to 100 parts by weight of the photocuring agent. 0.02 to 0.3 parts by weight is more preferable. If the content of the photoradical initiator in the pressure-sensitive adhesive layer is excessively small, the photocuring reaction may not proceed sufficiently even when irradiated with ultraviolet rays. If the content of the photo radical initiator is excessively large, even when an antioxidant is used in combination, the photo-curing reaction proceeds in the storage environment, increasing the adhesive strength with the adherend, making it difficult to rework the reinforcing film. It may become.

(Antioxidant)
Antioxidant has the effect | action which suppresses the photocuring reaction in the storage environment of a reinforcement film. In a composition containing an antioxidant in addition to a photoradical initiator, even when a small amount of photoradical is generated from the photoradical initiator by light from a fluorescent lamp or the like, the antioxidant traps the radical and a stable radical is generated. Since it produces | generates, the radical transfer to a photocuring agent is suppressed. Therefore, photocuring (radical polymerization reaction of photocuring agent) by light from a fluorescent lamp or the like is suppressed.

  Examples of the antioxidant include amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and phenol-based antioxidants.

  Examples of the sulfur-based antioxidant include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, and the like. Examples of phosphorus antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, and phenyl diisodecyl phosphite.

  Examples of amine-based antioxidants include monoalkyldiphenylamines such as monooctyldiphenylamine and monononyldiphenylamine; 4,4′-dibutyldiphenylamine, 4,4′-dipentyldiphenylamine, 4,4′-dihexyldiphenylamine, and 4,4 ′. -Dialkyldiphenylamines such as diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-dinonyldiphenylamine; polyalkyldiphenylamines such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, tetranonyldiphenylamine; -Naphtylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylfu Cycloalkenyl -α- naphthylamine, heptylphenyl -α- naphthylamine, octylphenyl -α- naphthylamine, naphthylamine such as nonylphenyl -α- naphthylamine, and the like.

  Examples of phenolic antioxidants include 2,6-di-t-butyl-p-cresol (dibutylhydroxytoluene; BHT), butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearin Monophenol antioxidants such as β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2 '-Methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol) 3,9-bis [1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] Bisphenol antioxidants such as ethyl] 2,4,8,10-tetraoxaspiro [5,5] undecane; 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) Butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ′, 5′-di) -T-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis- (4'-hydroxy-3'-t-butylphenyl) butyric acid] glycol ester, 1,3,5 -Polymeric phenolic systems such as tris (3 ', 5'-di-t-butyl-4'-hydroxybenzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione, tocophenol Antioxidant and the like.

  Among antioxidants, those that act as radical chain inhibitors such as amine-based antioxidants and phenol-based antioxidants from the viewpoint of suppressing photocuring by radicals generated from light radical initiators by light from fluorescent lamps, etc. Are preferred, and phenolic antioxidants having a hindered phenol structure are particularly preferred.

  In the antioxidant having a hindered phenol structure, a sterically hindered group such as a tert-butyl group is bonded to at least one of the adjacent carbon atoms to the carbon atom on the aromatic ring to which the OH group of phenol is bonded. Is. As an antioxidant having a hindered phenol structure, dibutylhydroxytoluene (BHT), pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (“Irganox 1010” manufactured by BASF) ), Octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate ("Irganox 1076" manufactured by BASF), 3,3 ', 3 ", 5,5', 5" -hexa- tert-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-cresol (“Irganox 1330” manufactured by BASF), 1,3,5-tris -Tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3 , 5H) -trione ("Irganox 3114" manufactured by BASF), tris [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxyethyl] isocyanurate ("Irganox 3125" manufactured by BASF), penta Erythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (“ADEKA STAB AO-60” manufactured by ADEKA), 3,9-bis {2- [3- (3-t- (Butyl-4-hydroxy-5-methylphenyl) propionyloxyoxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5.5] undecane (“ADEKA STAB AO-80” manufactured by ADEKA) ), 2- [1- (2-hydroxy-3,5-di-tert-pentylpheny] acrylic acid E) Ethyl] -4,6-di-tert-pentylphenyl (“Sumilyzer GS” manufactured by Sumitomo Chemical), 2-tert-butyl-4-methyl-6- (2-hydroxy-3-tert-butyl-acrylate) 5-Methylbenzyl) phenyl (“Sumilyzer GM” manufactured by Sumitomo Chemical), 2,2′-dimethyl-2,2 ′-(2,4,8,10-tetraoxaspiro [5.5] undecane-3,9 -Diyl) dipropane-1,1'-diyl = bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propanoate] (Sumitomo Chemical "Sumilyzer GA-80"), 1,3 5-tris (3-hydroxy-4-tert-butyl-2,6-dimethylbenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione "Cyanox 1790") manufactured by Kuwait.

  The content of the antioxidant in the pressure-sensitive adhesive layer 2 is preferably 0.01 to 2 parts by weight, more preferably 0.03 to 1 part by weight, with respect to 100 parts by weight of the base polymer, and 0.04 to 0.7. Part by weight is more preferable, and 0.05 to 0.5 part by weight is particularly preferable. The content of the antioxidant is preferably 0.2 to 5 times the content of the photo radical initiator, more preferably 0.3 to 3 times, and even more preferably 0.5 to 2 times.

(Combination effect of photo radical initiator and antioxidant)
In a composition containing an antioxidant in addition to a photoradical initiator, even when a small amount of photoradical is generated from the photoradical initiator by light from a fluorescent lamp or the like, the antioxidant traps the radical and a stable radical is generated. Generate. Therefore, radical polymerization reaction by light from a fluorescent lamp or the like is suppressed. From the viewpoint of suppressing the polymerization reaction in the storage state of the reinforcing film, it is preferable that the content of the antioxidant is large. On the other hand, if the content of the antioxidant is excessively large, even if UV irradiation is performed for photocuring, the antioxidant traps most of the photogenerated radicals, so that from the photoradical initiator to the photocuring agent. In some cases, the radical transfer of the light is hindered and photocuring may be insufficient. Therefore, the content of the antioxidant is within the above range in order to suppress the photopolymerization in the storage environment to prevent an increase in the adhesive force and to appropriately promote the photocuring reaction during the light irradiation to increase the adhesive force. Preferably there is.

  By using a photoradical initiator and an antioxidant together, the antioxidant traps radicals generated by light from fluorescent lamps, etc., so it is possible to suppress an increase in adhesion due to a photocuring reaction in a storage environment. . Therefore, regardless of the type of the photo radical initiator, the photocuring of the pressure-sensitive adhesive layer in the storage environment can be suppressed by the action of the antioxidant.

  On the other hand, when a reinforcing film having a pressure-sensitive adhesive layer containing a photoradical initiator and an antioxidant is exposed to a fluorescent lamp for a long time, the effective concentration of the photoradical initiator (light The concentration of the photo radical initiator capable of generating radicals is reduced. Therefore, even if ultraviolet irradiation is performed for photocuring, the amount of photoradicals generated is small, and the photocuring reaction may not proceed sufficiently.

  Even after long-term storage, the reinforcing film is less likely to cause photocuring of the adhesive by light such as a fluorescent lamp in the storage environment, and generates a sufficient amount of radicals upon irradiation with light. It is preferable that the adhesive strength with the body is increased. In order to sufficiently advance the photocuring reaction even after long-term storage, it is preferable to use a photoradical initiator that generates a small amount of radicals in the storage environment. Specifically, as described above, it is preferable to use a photoradical initiator having an absorption maximum wavelength of 360 nm or less and a small amount of photoradical generated by a mercury emission line (particularly wavelength 365 nm) of a fluorescent lamp.

  The amount of radicals generated from the photoradical initiator by the light from the fluorescent lamp is determined, for example, by irradiating light with a wavelength of 365 nm at an extremely low temperature and electron spin resonance (ESR) as shown in the examples described later. Can be evaluated. Since radicals derived from photo radical initiators have an extremely short lifetime at room temperature, cryogenic temperatures are suitable for evaluation of radical production.

(Other additives)
In addition to the components exemplified above, the pressure-sensitive adhesive layer contains a silane coupling agent, a tackifier, a plasticizer, a softener, a deterioration inhibitor, a filler, a colorant, an ultraviolet absorber, a surfactant, and an antistatic agent. You may contain additives, such as an agent, in the range which does not impair the characteristic of this invention.

[Production of reinforcing film]
A laminated film is obtained by laminating the photocurable pressure-sensitive adhesive layer 2 on the film substrate 1. The pressure-sensitive adhesive layer 2 may be directly formed on the film substrate 1, or a pressure-sensitive adhesive layer formed in a sheet shape on another substrate may be transferred onto the film substrate 1.

  Apply the above adhesive composition by roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coat, etc. The pressure-sensitive adhesive layer is formed by coating on a substrate and removing the solvent by drying as necessary. As a drying method, an appropriate method can be adopted as appropriate. The heat drying temperature is preferably 40 ° C to 200 ° C, more preferably 50 ° C to 180 ° C, and further 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.

  The thickness of the pressure-sensitive adhesive layer 2 is, for example, about 1 to 300 μm. There exists a tendency for adhesiveness with a to-be-adhered body to improve, so that the thickness of the adhesive layer 2 is large. On the other hand, when the thickness of the pressure-sensitive adhesive layer 2 is excessively large, the fluidity before photocuring is high and handling may be difficult. Therefore, the thickness of the pressure-sensitive adhesive layer 2 is preferably 5 to 100 μm, more preferably 8 to 50 μm, further preferably 10 to 40 μm, and particularly preferably 13 to 30 μm.

  When the pressure-sensitive adhesive composition contains a cross-linking agent, it is preferable to advance the cross-linking by heating or aging simultaneously with the drying of the solvent or after the drying of the solvent. The heating temperature and heating time are appropriately set depending on the type of the crosslinking agent to be used, and are usually crosslinked by heating in the range of 20 ° C. to 160 ° C. for about 1 minute to 7 days. The heating for removing the solvent by drying may also serve as the heating for crosslinking.

  By introducing a cross-linked structure into the base polymer, the gel fraction increases. The higher the gel fraction, the harder the pressure-sensitive adhesive, and the adhesive residue on the adherend tends to be suppressed when the reinforcing film is peeled off from the adherend by rework or the like. The gel fraction of the pressure-sensitive adhesive layer 2 before photocuring is preferably 30% or more, more preferably 50% or more, still more preferably 60% or more, and particularly preferably 65% or more. The gel fraction before photocuring of the pressure-sensitive adhesive layer 2 may be 70% or more or 75% or more.

  Since the adhesive contains an unreacted photocuring agent, the gel fraction of the adhesive layer 2 before photocuring is generally 90% or less. If the gel fraction of the pressure-sensitive adhesive layer 2 before photocuring is excessively large, the anchoring force on the adherend may be reduced, and the initial adhesive force may be insufficient. Therefore, the gel fraction of the pressure-sensitive adhesive layer 2 before photocuring is preferably 85% or less, and more preferably 80% or less.

  The gel fraction can be determined as an insoluble content in a solvent such as ethyl acetate. Specifically, the insoluble component after the pressure-sensitive adhesive layer is immersed in ethyl acetate at 23 ° C. for 7 days is measured with respect to the sample before the immersion. It is calculated | required as a weight fraction (unit: weight%). In general, the gel fraction of the polymer is equal to the degree of cross-linking, and the more cross-linked portions in the polymer, the greater the gel fraction. Also, the greater the amount of photocuring agent, the smaller the gel fraction.

  Even after the crosslinking structure is introduced into the polymer by the crosslinking agent, the photocuring agent remains in an unreacted state. Therefore, the photocurable pressure-sensitive adhesive layer 2 including the base polymer and the photocuring agent is formed. When the pressure-sensitive adhesive layer 2 is formed on the film substrate 1, it is preferable to attach a separator 5 on the pressure-sensitive adhesive layer 2 for the purpose of protecting the pressure-sensitive adhesive layer 2 or the like. Crosslinking may be performed after the separator 5 is provided on the pressure-sensitive adhesive layer 2.

  When the pressure-sensitive adhesive layer 2 is formed on another substrate, the reinforcing film is obtained by transferring the pressure-sensitive adhesive layer 2 onto the film substrate 1 after drying the solvent. The base material used for forming the pressure-sensitive adhesive layer may be used as the separator 5 as it is.

  As the separator 5, a plastic film such as polyethylene, polypropylene, polyethylene terephthalate, or a polyester film is preferably used. The thickness of the separator is usually 3 to 200 μm, preferably about 10 to 100 μm. The contact surface of the separator 5 with the pressure-sensitive adhesive layer 2 is subjected to a release treatment such as a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based release agent, or silica powder. preferable. When the surface of the separator 5 is subjected to the mold release treatment, when the film base 1 and the separator 5 are peeled off, peeling occurs at the interface between the pressure-sensitive adhesive layer 2 and the separator 5, and the pressure-sensitive adhesive is formed on the film base 1. The state in which the layer 2 is fixed is maintained.

[Use of reinforcing film]
The reinforcing film of the present invention is used by being bonded to a device or a device component. In the reinforcing film 10, the pressure-sensitive adhesive layer 2 is fixed to the film substrate 1, and the adhesive force to the adherend is small after photobonding with the adherend and before photocuring. Therefore, it is easy to peel the reinforcing film from the adherend before photocuring, and the reworkability is excellent. In addition, it is possible to easily perform processing such as cutting the reinforcing film before photocuring and removing the reinforcing film in a part of the surface of the adherend.

  The adherend to which the reinforcing film is bonded is not particularly limited, and examples thereof include various electronic devices, optical devices, and component parts thereof. The reinforcing film may be bonded to the entire surface of the adherend, or may be selectively bonded only to a portion requiring reinforcement. Moreover, after bonding a reinforcement film to the whole surface of a to-be-adhered body, you may cut | disconnect the reinforcement film of the location which does not require reinforcement, and peel and remove a reinforcement film. If it is before photocuring, since the reinforcing film is temporarily attached to the surface of the adherend, the reinforcing film can be easily removed from the surface of the adherend.

<Characteristics of pressure-sensitive adhesive layer before photocuring>
(Adhesive strength)
From the viewpoint of facilitating peeling from the adherend and preventing adhesive residue on the adherend after peeling the reinforcing film, the adhesive force between the pressure-sensitive adhesive layer 2 before photocuring and the adherend is 5 N / 25 mm. The following is preferable, 2N / 25mm or less is more preferable, and 1.3N / 25mm or less is further more preferable. From the viewpoint of preventing peeling of the reinforcing sheet during storage and handling, the adhesive force between the pressure-sensitive adhesive layer 2 and the adherend before photocuring is preferably 0.005 N / 25 mm or more, and 0.01 N / 25 mm or more. More preferably, 0.1 N / 25 mm or more is further preferable, and 0.3 N / 25 mm or more is particularly preferable.

  The reinforcing film preferably has an adhesive force with respect to the polyimide film within the above range in a state before the pressure-sensitive adhesive layer is photocured. In a flexible display panel, a flexible printed wiring board (FPC), a device in which a display panel and a wiring board are integrated, a flexible substrate material is generally used from the viewpoint of heat resistance and dimensional stability. A polyimide film is used. The reinforcing film in which the pressure-sensitive adhesive layer has the above adhesive force to the polyimide film as the substrate is easy to peel before photocuring of the pressure-sensitive adhesive, and is excellent in adhesion reliability after photocuring.

(Storage modulus)
The pressure-sensitive adhesive layer 2 preferably has a shear storage modulus G ′ _i at 25 ° C. before photocuring of 1 × 10 ^{4 to} 1.2 × 10 ⁵ Pa. The shear storage elastic modulus (hereinafter simply referred to as “storage elastic modulus”) is based on the method described in JIS K7244-1 “Plastics—Testing Method for Dynamic Mechanical Properties” under the condition of a frequency of 1 Hz. It is obtained by reading a value at a predetermined temperature when measured at a temperature rising rate of 5 ° C./min in the range of 50 to 150 ° C.

In a material exhibiting viscoelasticity such as an adhesive, the storage elastic modulus G ′ is used as an index representing the degree of hardness. The storage elastic modulus of the pressure-sensitive adhesive layer has a high correlation with the cohesive force. The higher the cohesive force of the pressure-sensitive adhesive, the greater the anchoring force on the adherend. If the storage elastic modulus of the pressure-sensitive adhesive layer 2 before photocuring is 1 × 10 ⁴ Pa or more, the pressure-sensitive adhesive has sufficient hardness and cohesion, so that the adherend is peeled off when the reinforcing film is peeled from the adherend. It is difficult for adhesive residue to occur. Moreover, when the storage elastic modulus of the adhesive layer 2 is large, the protrusion of the adhesive from the end face of the reinforcing film can be suppressed. If the storage elastic modulus of the pressure-sensitive adhesive layer 2 before photocuring is 1.2 × 10 ⁵ Pa or less, peeling at the interface between the pressure-sensitive adhesive layer 2 and the adherend is easy, and even when rework is performed. Further, cohesive failure of the pressure-sensitive adhesive layer and adhesive residue on the adherend surface hardly occur.

From the viewpoint of enhancing the reworkability of the reinforcing sheet and suppressing the adhesive residue on the adherend during rework, the storage elastic modulus G ′ _i at 25 ° C. before photocuring of the pressure-sensitive adhesive layer 2 is 3 × 10 ⁴ to 1 × 10 ⁵ Pa is more preferable, and 4 × 10 ^{4 to} 9.5 × 10 ⁴ Pa is more preferable.

<Photocuring of adhesive layer>
After the reinforcing film is bonded to the adherend, the pressure-sensitive adhesive layer is photocured by irradiating the pressure-sensitive adhesive layer 2 with actinic rays. Examples of the actinic rays include ultraviolet rays, visible light, infrared rays, X-rays, α rays, β rays, and γ rays. Since the curing of the pressure-sensitive adhesive layer in the storage state can be suppressed and the curing is easy, ultraviolet rays are preferable as the actinic rays. What is necessary is just to set the irradiation intensity | strength and irradiation time of actinic light suitably according to a composition, thickness, etc. of an adhesive layer. Irradiation of the actinic ray to the pressure-sensitive adhesive layer 2 may be performed from any surface on the film base 1 side or the adherend side, or actinic light may be irradiated from both surfaces.

<Characteristics of pressure-sensitive adhesive layer after photocuring>
(Adhesive strength)
From the viewpoint of reliability of the device in practical use, the adhesive force between the pressure-sensitive adhesive layer 2 and the adherend is preferably 6 N / 25 mm or more, more preferably 10 N / 25 mm or more, and 12 N / 25 mm or more. More preferably, 14 N / 25 mm or more is particularly preferable. It is preferable that the pressure-sensitive adhesive layer of the reinforcing film has an adhesive force in the above range with respect to the polyimide film. The adhesive force between the pressure-sensitive adhesive layer 2 and the adherend after photocuring is preferably 4 times or more, more preferably 8 times or more, and more preferably 10 times that of the adhesive layer 2 before photocuring and the adherend. The above is more preferable.

The pressure-sensitive adhesive layer 2 preferably has a storage elastic modulus G ′ _f at 25 ° C. after photocuring of 1.5 × 10 ⁵ Pa or more. When the storage elastic modulus of the pressure-sensitive adhesive layer 2 after photocuring is 1.5 × 10 ⁵ Pa or more, the adhesive force with the adherend is improved with an increase in cohesive force, and high adhesion reliability is obtained. . On the other hand, when the storage elastic modulus is excessively large, the pressure-sensitive adhesive hardly spreads and the contact area with the adherend becomes small. Further, since the stress dispersibility of the pressure-sensitive adhesive is reduced, the peeling force tends to propagate to the adhesive interface, and the adhesive force with the adherend tends to be reduced. Therefore, the storage elastic modulus G ′ _f at 25 ° C. after photocuring of the pressure-sensitive adhesive layer 2 is preferably 2 × 10 ⁶ Pa or less. From the viewpoint of enhancing the adhesion reliability of the reinforcing sheet after photocuring the pressure-sensitive adhesive layer, G ′ _f is more preferably 1.8 × 10 ^{5 to} 1.2 × 10 ⁶ Pa, and 2 × 10 ⁵ to 1 × 10. ⁶ Pa is more preferable.

The ratio G ′ _f / G ′ _i of the storage elastic modulus at 25 ° C. before and after photocuring of the pressure-sensitive adhesive layer 2 is preferably 2 or more. If G _'f is G' _i 2 times or more, a large increase in G 'by photocuring may both rework of previous photocuring and adhesion reliability after photocuring. G ′ _f / G ′ _i is more preferably 4 or more, further preferably 8 or more, and particularly preferably 10 or more. The upper limit of G _{'f /} G' _i is not particularly limited, G if _{'f /} G' _i is excessively large, the pre photocurable G 'initial adhesion failure due to small, or G after photocuring' It is easy to lead to the fall of adhesion reliability by being too large. Therefore, G ′ _f / G ′ _i is preferably 100 or less, more preferably 40 or less, further preferably 30 or less, and particularly preferably 25 or less.

  The adherend after the reinforcement film is attached may be subjected to heat treatment such as autoclave treatment or thermocompression bonding for circuit member joining for the purpose of improving the affinity of the laminated interfaces of a plurality of laminated members. When such heat treatment is performed, it is preferable that the adhesive between the reinforcing film and the adherend does not flow from the end face.

From the viewpoint of suppressing the protrusion of the pressure-sensitive adhesive during high-temperature heating, the storage elastic modulus at 100 ° C. of the pressure-sensitive adhesive layer 2 after photocuring is preferably 5 × 10 ⁴ Pa or more, more preferably 8 × 10 ⁴ Pa or more. 1 × 10 ⁵ Pa or more is more preferable. In addition to preventing the adhesive from sticking out during heating, the storage elastic modulus at 100 ° C. of the pressure-sensitive adhesive layer 2 after photocuring is 60% of the storage elastic modulus at 50 ° C. The above is preferable, 65% or more is more preferable, 70% or more is further preferable, and 75% or more is particularly preferable.

[Usage of reinforcing film]
The reinforcing film of the present invention is used by being bonded to a component (work-in-process) of various devices or a completed device. By attaching the reinforcing film, moderate rigidity is imparted, and therefore, an improvement in handling properties and an effect of preventing breakage are expected. In the device manufacturing process, when the reinforcing film is bonded to the work-in-process, the reinforcing film may be bonded to the large work-in-process before being cut into the product size. A reinforcing film may be bonded to a mother roll of a device manufactured by a roll-to-roll process using a roll-to-roll.

  As devices are highly integrated, reduced in size and weight, and reduced in thickness, the thickness of members constituting the device tends to decrease. The thinning of the constituent members tends to cause bending and curling due to stress and the like at the lamination interface. Further, the thinning tends to cause bending due to its own weight. By bonding the reinforcing film, rigidity can be imparted to the adherend, so that bending, curling, bending, and the like due to stress, dead weight, and the like are suppressed, and handling properties are improved. Therefore, by sticking the reinforcing film to the work-in-process in the device manufacturing process, it is possible to prevent defects and defects during conveyance and processing by an automated apparatus.

  In automatic conveyance, it is inevitable that the work in process to be conveyed contacts the conveyance arm or pin. In addition, the work in process may be cut to adjust the shape or remove unnecessary portions. Highly integrated, small, light, and thin devices are likely to be damaged due to local stress concentration during contact with a conveying device or cutting. In the manufacturing process of a device in which a plurality of members are stacked, not only the members are sequentially stacked, but some of the members, process materials, and the like may be peeled off from the work in process. In the case where the member is thinned, stress may be locally concentrated at the peeling site and the vicinity thereof, resulting in breakage or dimensional change. Since the reinforcing film has stress dispersibility due to the pressure-sensitive adhesive layer, by attaching the reinforcing film to the object to be transported and the object to be processed, moderate rigidity is given and stress is relaxed and dispersed. Problems such as cracks, cracks, peeling, and dimensional changes can be suppressed.

  As described above, by laminating the reinforcing film of the present invention, the work in progress, which is an adherend, is imparted with an appropriate rigidity, and stress is relaxed and dispersed. Control, improve production efficiency, and improve yield. In addition, since the reinforcing film can be easily peeled off from the adherend before the pressure-sensitive adhesive layer is photocured, reworking is easy even when lamination or poor bonding occurs.

  In the reinforcing film of the present invention, the pressure-sensitive adhesive layer 2 is photocurable, and the timing of curing can be arbitrarily set. Processing such as rework and processing of the reinforcing film can be performed at any timing after the reinforcing film is pasted on the adherend and before the adhesive is photocured. It can respond flexibly. As described above, since the pressure-sensitive adhesive layer contains an antioxidant in addition to the photocuring agent and the photoradical initiator, photocuring with light from a fluorescent lamp or the like hardly proceeds. Therefore, even when stored for a long time with the reinforcing film attached to the adherend, the reinforcing film can be easily peeled off from the adherend before photocuring.

  In use of the device after completion, the reinforcing film is stuck even when external force is unexpectedly applied due to falling of the device, placement of heavy objects on the device, collision of flying objects on the device, etc. Therefore, damage to the device can be prevented. In addition, since the reinforcing film after photocuring the adhesive is firmly bonded to the device, the reinforcing film is difficult to peel off even in long-term use, and is excellent in reliability.

  The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[Production of reinforcing film]
<Polymerization of base polymer>
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas introduction tube, as monomers, 63 parts by weight of 2-ethylhexyl acrylate (2EHA), 15 parts by weight of N-vinylpyrrolidone (NVP), methyl methacrylate (MMA) 9 parts by weight, 13 parts by weight of hydroxyethyl acrylate (HEA), 0.2 parts by weight of azobisisobutyronitrile as a thermal polymerization initiator, and 233 parts by weight of ethyl acetate as a solvent were added, and nitrogen gas was passed and stirred. Then, nitrogen substitution was performed for about 1 hour. Then, it heated at 60 degreeC and made it react for 7 hours, and obtained the solution of the acrylic polymer whose weight average molecular weight (Mw) is 1.2 million.

<Preparation of pressure-sensitive adhesive composition>
In the acrylic polymer solution, “Takenate D110N” (75% ethyl acetate solution of trimethylolpropane adduct of xylylene diisocyanate) made by Mitsui Chemicals as a crosslinking agent, and “A-200” made by Shin-Nakamura Chemical Co., Ltd. as a polyfunctional acrylic monomer ( Polyethylene glycol # 200 (n = 4) diacrylate; molecular weight 308, functional group equivalent 154 g / eq), photoradical initiator, and antioxidant were added and mixed uniformly to prepare an adhesive composition. . The blending amount (solid content) of the crosslinking agent was 2.5 parts by weight with respect to 100 parts by weight of the base polymer, and the blending amount of the polyfunctional acrylic monomer was 30 parts by weight with respect to 100 parts by weight of the base polymer. As an antioxidant, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (“Irganox 1010” manufactured by BASF) was blended in the amounts shown in Table 1. As the photoradical initiator, those shown below were blended in the amounts shown in Table 1.

(Photo radical initiator)
IRG184: 1-hydroxycyclohexyl phenyl ketone ("Irgacure 184" manufactured by BASF, absorption maximum wavelength: 246 nm, 280 nm, 333 nm)
IRG651: 2,2-dimethoxy-1,2-diphenylethane-1-one (BASF "Irgacure 651", absorption maximum wavelength: 250 nm, 340 nm)
IRG819: Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (“Irgacure 819” manufactured by BASF, absorption maximum wavelength: 295 nm, 370 nm)

<Coating and crosslinking of adhesive solution>
On the 75-micrometer-thick polyethylene terephthalate film ("Lumirror S10" by Toray) which is not surface-treated, said adhesive composition was apply | coated using the fountain roll so that the thickness after drying might be set to 25 micrometers. After removing the solvent by drying at 130 ° C. for 1 minute, a release treatment surface of a separator (a polyethylene terephthalate film having a thickness of 25 μm whose surface was subjected to silicone release treatment) was bonded to the pressure-sensitive adhesive application surface. Thereafter, an aging treatment for 4 days was performed in an atmosphere at 25 ° C. to advance the crosslinking, and a reinforcing film having a photocurable pressure-sensitive adhesive sheet fixedly laminated on the film base material and a separator temporarily attached thereon was obtained.

[Measurement of adhesive strength]
A polyimide film having a thickness of 12.5 μm (“Kapton 50EN” manufactured by Toray DuPont) was attached to a glass plate via a double-sided adhesive tape (“No. 531” manufactured by Nitto Denko) to obtain a polyimide film substrate for measurement. The separator was peeled and removed from the surface of the reinforcing film cut out to a width of 25 mm and a length of 100 mm, and bonded to the measurement polyimide film substrate using a hand roller to obtain a test sample before photocuring. From the reinforcing film side (PET film side) of the test sample before photocuring, the pressure-sensitive adhesive layer was photocured by irradiating UV light with an integrated light amount of 400 mJ / cm ² using an LED light source with a wavelength of 365 nm. A test sample was obtained. Using these test samples, the end portion of the polyethylene terephthalate film of the reinforcing film was held with a chuck, the reinforcing film was peeled at 180 ° at a tensile speed of 300 mm / min, and the peel strength was measured.

<Evaluation of adhesive strength of reinforcing film after storage for a certain period>
The reinforcing sheet is allowed to stand in a bright room at room temperature, and after 1 week and 4 weeks, it is bonded to the polyimide film substrate for measurement, and the test sample before and after photocuring is 180 ° peel strength as described above. Was measured.

  Table 1 shows the composition of the pressure-sensitive adhesive for each reinforcing film and the measurement results of the adhesive strength before and after photocuring.

  In any sample, immediately after fabrication, the adhesive force before photocuring is easily peeled off from the adherend in the range of 0.2 to 0.4 N / 25 mm, and after photocuring, the adhesive strength is 15 N / It rose to 25 mm or more and was firmly adhered to the adherend.

Sample 10 was used viscosity Chakuzai containing no antioxidant, adhesive force before photocuring in the samples after storage for four weeks has risen significantly, it has been difficult separation from the adherend. On the other hand, in sample 11 to which 0.1 part by weight of antioxidant was added, the adhesive strength before photocuring was slightly increased in the sample after storage for 4 weeks, but peeling from the adherend was sufficiently possible. Met. In Sample 11, the adhesive strength after photocuring of the sample after storage for 4 weeks was equivalent to that of the sample immediately after production.

Sample 20 and sample 30 with viscous Chakuzai containing no antioxidant, as Sample 10, a significant increase in the adhesive force before photocuring was observed in the samples after storage for 4 weeks. In Sample 20 and Sample 30, the adhesive strength before photocuring was increased to 10 N / 25 mm or more even in the sample after storage for 1 week. Samples 21 and 31 to which 0.1 part by weight of antioxidant was added also exhibited low adhesive strength before photocuring and high adhesive strength after photocuring even in samples after storage for 1 week.

  From the comparison of the above results, by using a photoradical initiator and an antioxidant together, even when stored for a long time under a fluorescent lamp, it is excellent in reworkability from the adherend before photocuring and is photocured. Thus, it can be seen that a reinforcing film showing a high adhesive force to the adherend can be obtained.

  In sample 12 to which 0.5 parts by weight of antioxidant was added, the rate of increase in adhesive strength by photocuring decreased after storage for 1 week, and the adhesion increased almost even after irradiation for 4 weeks. I did not. In the sample 13 to which 1 part by weight of the antioxidant was added, the increase in adhesive force due to ultraviolet irradiation was insufficient even after storage for 1 week. Also in the comparison of Samples 21 to 23 and the comparison of Samples 31 to 33, there was a tendency that the adhesive force did not increase even when ultraviolet irradiation was performed with an increase in the amount of addition of the antioxidant.

  From these results, it can be said that when the addition amount of the antioxidant is large, the photocuring tends to be difficult to proceed as the storage period from the sample preparation becomes longer. This is presumably because the photoradical initiator is deactivated as the storage period under the fluorescent lamp from the sample preparation becomes longer, and the amount of radicals generated is small even when ultraviolet irradiation is performed.

  If the storage period under a fluorescent lamp becomes longer and the effective concentration of the photoradical initiator decreases, the amount of radicals generated during ultraviolet irradiation decreases. Antioxidants have the action of trapping radicals generated from photoradical initiators by light from fluorescent lamps in the storage environment and inhibiting undesired photoradical polymerization, but ultraviolet rays are used for photocuring. Even when irradiated, it acts to trap radicals. Therefore, when the storage period under a fluorescent lamp is long and the effective concentration of the photoradical initiator is low, the ratio of radicals trapped in the antioxidant among the photoradicals generated from the photoradical initiator increases, and the light The ratio of radicals contributing to radical polymerization is lowered. The higher the antioxidant content, the greater the polymerization inhibition effect (polymerization inhibition). Therefore, it is considered that the photoradical reaction of the photocuring agent does not proceed easily even when irradiated with ultraviolet rays, and the adhesive force is not sufficiently increased. .

  From the above results, by appropriately adjusting the amount of the antioxidant used in combination with the photo radical initiator, it is excellent in reworkability from the adherend before photocuring even when the storage period under a fluorescent lamp is long. And it turns out that photocuring advances suitably by ultraviolet irradiation, and the reinforcement film which can implement | achieve high adhesive force is obtained.

[Measurement and consideration of radical concentration by electron spin resonance]
In order to verify the radical generation amount of the photo radical initiator used in the above examples and the effect of the antioxidant, light was irradiated at an extremely low temperature, and the radical generation amount was evaluated by ESR.

A concentration of 0.2 mol for each of the radical photoinitiator (IRG184, IRG651 or IRG819) alone, the antioxidant (Irganox 1010) alone, and the combined system of the radical photoinitiator (Irg651 or Irg819) and the antioxidant. / L ethyl acetate solution was prepared (in the combined system, each concentration was 0.2 mol / L). 0.1 mL of the sample solution was loaded into an ESR sample tube (about 3.5 mmφ quartz tube), set in the cavity of the ESR, and light irradiation ESR measurement was performed at a temperature of 40K. An ultra-high pressure mercury lamp (manufactured by Ushio Inc.) was used as the light irradiation lamp, short-wavelength light having a wavelength of 290 nm or less was cut with a glass filter, and heat rays were cut with a water filter. The illuminance (wavelength 365 nm) measured on the front surface of the cavity was 18 mW / cm ² . The apparatus and main measurement conditions are shown below.

Device: ESP350E (BRUKER)
Attached device: HP5351B microwave frequency counter (made by HEWLETT PACKARD)
ER035M Gauss meter (BRUKER)
ESR910 Cryostat (BRUKER)
Cavity: TM110, cylindrical Measurement temperature: 40 K
Central magnetic field: 3385 G
Magnetic field sweep width: 400 G
Modulation: 100 kHz, 10 G
Microwave: 9.49 GHz, 0.16 mW
Sweep time: 83.89 seconds x 2 Time constant: 327.68 milliseconds Number of data points: 1024

  From the ESR spectra at 5 minutes, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes and 60 seconds after the start of light irradiation, the amount of radicals was quantified by a calibration curve method. FIG. 4 shows a graph plotting light irradiation time and radical concentration for each sample.

  Looking at the three types of photo radical initiators, Irgacure 819 (IRG819) showed the highest radical production. This is considered to be due to the fact that IRG 819 has an absorption maximum at a wavelength of 370 nm and is highly sensitive to irradiation light (wavelength 365 nm). In Irgacure 184 (IRG184) and Irgacure 651 (IRG651), Irgacure 651 showed a larger radical generation amount.

  There is a correlation between these radical generation amounts and changes in adhesive strength before photocuring during storage of Sample 10, Sample 20 and Sample 30 under a fluorescent lamp. That is, Irgacure 184 has a small amount of radicals generated by light from a fluorescent lamp, so that the sample 10 showed no increase in adhesive strength before photocuring after storage for 1 week, whereas Irgacure 651 was used. In the sample 20 and the sample 30 using Irgacure 819, the amount of photo radicals generated by the light from the fluorescent lamp is relatively large, and thus it is considered that the adhesive force before photocuring increased in the sample after one week storage.

  The antioxidant (Irganox 1010) showed a higher radical concentration than the three photoradical initiators. This is because the radicals generated from antioxidants are highly stable and the amount of radical disappearance is smaller than that of photo radical initiators. it seems to do.

  In the combined system of the photo radical initiator (IRG651 or IRG819) and the antioxidant, the radical concentration was lower than that in the case of the antioxidant alone. Since the radical concentration of the combined system is smaller than the sum of the case of the photoradical initiator alone and the case of the antioxidant alone, it is considered that the radicals generated from the photoradical initiator are trapped by the antioxidant.

Claims (8)

A film base material, and an adhesive layer fixedly laminated on one main surface of the film base material,
The pressure-sensitive adhesive layer is composed of a photocurable composition containing a base polymer, a photocuring agent, a photoradical initiator, and an antioxidant, and the photocuring agent is used in an amount of 10 to 50 with respect to 100 parts by weight of the base polymer. parts, the photo-radical initiator 0.01 to 1 part by weight, 0.01 to 2 parts by weight of viewing including the antioxidant,
The reinforcing film in which the content of the antioxidant is 0.2 to 3 times the content of the photoradical initiator . The reinforcing film according to claim 1, wherein the photo radical initiator has an absorption maximum in a wavelength range of 310 nm to 355 nm and does not exhibit an absorption maximum at a wavelength longer than 360 nm. The base polymer contains at least one selected from the group consisting of a hydroxy group-containing monomer and a carboxy group-containing monomer as a monomer unit, and a crosslinked structure is introduced by a crosslinking agent bonded to the hydroxy group or the carboxy group. It is, reinforcing film according to claim 1 or 2. The reinforcing film according to any one of claims 1 to 3 , comprising an acrylic polymer as the base polymer. The said acrylic polymer is a reinforcement film of Claim 4 containing 5 to 50weight% of monomer components whose glass transition temperature of a homopolymer is 40 degreeC or more. The light hardener is a polyfunctional (meth) acrylate, reinforced film according to any one of claims 1-5. The reinforcing film according to any one of claims 1 to 6 , wherein a functional group equivalent of the photocuring agent is 100 to 500 g / eq. The adhesive force between the adhesive layer and the polyimide film is a 0.005~5N / 25mm, and the adhesive strength between the polyimide film after photocuring the viscosity adhesive layer is 6N / 25 mm or more, according to claim 1 The reinforcing film according to any one of to 7 .

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