WO2020045067A1

WO2020045067A1 - Reinforcing film

Info

Publication number: WO2020045067A1
Application number: PCT/JP2019/031726
Authority: WO
Inventors: 賢一片岡; 武史仲野
Original assignee: 日東電工株式会社
Priority date: 2018-08-27
Filing date: 2019-08-09
Publication date: 2020-03-05
Also published as: KR102072660B1; CN112601796B; JP2020033401A; TW202009284A; TWI795574B; CN112601796A; JP6581704B1

Abstract

A reinforcing film (10) comprises: an adhesive agent layer (2) that is fixed/laminated on one primary surface of a film substrate (1). The adhesive agent layer is formed from a photo-curable composition comprising a base polymer, a photo-curable agent and a photopolymerization initiator. The reinforcing film has a wetting speed, with respect to a glass sheet, of 0.3 to 4 cm²/second. This reinforcing film can be easily reworked immediately after being affixed to an adherend, firm adhesion with the adherend is possible, and the time until adhesive force increases after affixing to an adherend can be freely set.

Description

Reinforcement film

The present invention relates to a reinforcing film attached to a device surface.

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

(4) In a state before use such as assembling, processing, and transporting the device, by temporarily attaching the adhesive film to the surface of the device or the component of the device, it is possible to suppress damage and breakage of the adherend. Such an adhesive film is a process material and is peeled off before use of the device. As described in Patent Literature 1, an adhesive film used as a process material is easily wetted and spread on an adherend, has low tackiness, and can be easily peeled off from the adherend. It is required that no glue remains.

Patent Document 2 discloses an adhesive film that is used while being attached to a device surface 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 impact on the device and imparting rigidity to the flexible device, in addition to surface protection.

(4) When bonding the adhesive film to the adherend, bonding defects such as mixing of air bubbles and displacement of the bonding position may occur. When bonding failure occurs, an operation (rework) of peeling the adhesive film from the adherend and bonding another adhesive film is performed. The pressure-sensitive adhesive film used as the process material is designed on the assumption that the adhesive film is separated from the adherend, so that rework is easy. On the other hand, the reinforcing film is generally not expected to be peeled from the device, and is strongly adhered to the surface of the device, so that rework is difficult.

Patent Document 3 discloses a pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) that has low tackiness immediately after lamination with an adherend and is designed so that the adhesive force increases with time. The pressure-sensitive adhesive film having such a pressure-sensitive adhesive layer fixedly laminated on a film substrate is easily peeled off from the adherend immediately after lamination with the adherend, and after a predetermined time elapses, the adhesive film Since it adheres firmly, it can be used as a reworkable reinforcing film.

JP 2013-107998 A JP-A-2017-132977 WO2015 / 163115 pamphlet

Adhesive films to be bonded to the device surface must be free of air bubbles during bonding and have excellent workability in bonding, and should be able to be easily peeled off (reworked) if bonding failure occurs. Can be Reinforcement films whose adhesive strength to an adherend changes with time can be easily reworked immediately after lamination, but are not sufficiently flexible with respect to the lead time of the process. For example, a reinforcing film having a pressure-sensitive adhesive layer whose adhesive strength increases with time, after bonding with an adherend, within a predetermined time until the adhesive strength increases, inspects the bonded state and performs rework. There is a need. In addition, when the reinforcing film is attached to the entire surface of the device or device component and then the processing such as removing the reinforcing film from a part of the area is performed, it is necessary to perform the processing until the adhesive strength increases. is there.

In view of the above, the present invention is excellent in the bonding property with the adherend, and after bonding with the adherend, it is possible to arbitrarily set the time until the adhesive strength is improved, and by improving the adhesive strength. An object of the present invention is to provide a reinforcing film capable of firmly adhering to an adherend.

補強 The reinforcing film of the present invention includes a pressure-sensitive 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 and a photopolymerization initiator. As the base polymer of the pressure-sensitive adhesive layer, for example, an acrylic polymer is used.

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

(4) The photocuring agent is a monomer or oligomer having two or more polymerizable functional groups, and a polyfunctional (meth) acrylate or the like is used. The molecular weight of the photocuring agent is preferably 1500 or less. The functional group equivalent of the photocuring agent is preferably about 100 to 500 g / eq. The amount of the photocuring agent in the photocurable composition constituting the pressure-sensitive adhesive layer is preferably from 10 to 50 parts by weight based on 100 parts by weight of the base polymer.

The reinforcing film preferably has a wetting rate for the glass plate of 0.3 cm ² / sec to 4 cm ² / sec. The reinforcing film before the photocuring of the pressure-sensitive adhesive layer preferably has an adhesive force to an adherend such as a glass plate of 0.03 N / 25 mm or more and less than 1 N / 25 mm. It is preferable that the adhesive strength of the reinforcing film after the photocuring of the pressure-sensitive adhesive layer to an adherend such as a glass plate is 1 N / 25 mm or more.

補強 In the reinforcing film of the present invention, the adhesive layer is made of a photocurable composition, and the adhesive strength to the adherend is increased by photocuring the adhesive layer after the adhesion to the adherend. Before light curing, rework is easy because the adhesive force with the adherend is small. In addition, since it has an appropriate wetting rate with respect to an adherend such as glass, it is excellent in bonding workability. Since the pressure-sensitive adhesive after photo-curing shows high adhesive strength, it is expected that the reinforcement of the device and the improvement of reliability can be expected by bonding a reinforcing film. The photocurable pressure-sensitive adhesive can arbitrarily set the timing of curing after lamination with the adherend, and thus the reinforcing film of the present invention can flexibly respond to the lead time of the process.

It is sectional drawing which shows the lamination structure of a reinforcement film. It is sectional drawing which shows the lamination structure of a reinforcement film. It is sectional drawing which shows the device to which the reinforcement film was stuck.

FIG. 1 is a cross-sectional view illustrating one 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 film substrate 1. The pressure-sensitive adhesive layer 2 is a photocurable pressure-sensitive adhesive made of a photocurable composition, and is cured by irradiation with actinic rays such as ultraviolet rays, so that the adhesive strength to an adherend increases.

FIG. 2 is a cross-sectional view of the reinforcing film in which the 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 attached to the surface of the device 20.

The separator 5 is peeled off 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 as an adherend, whereby the reinforcing film 10 is bonded to the surface of the device 20. . In this state, the pressure-sensitive adhesive layer 2 has not been cured yet, and the reinforcing film 10 (pressure-sensitive adhesive layer 2) has been temporarily attached to the device 20. By photo-curing 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 adhered to each other and separation at the interface between them is impossible or difficult. "Temporary adhesion" is a state in which the adhesive strength between the two laminated layers is small and the two layers can be easily peeled off at the interface between them.

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

デバイス In the device to which the reinforcing film 10 shown in FIG. 3 is attached, the device 20 and the pressure-sensitive adhesive layer 2 are in a temporarily attached state before the light-curing of the pressure-sensitive adhesive layer 2. When the film substrate 1 and the device 20 are separated, separation occurs at the interface between the pressure-sensitive adhesive layer 2 and the device 20, and the state in which the pressure-sensitive adhesive layer 2 is fixed on the film substrate 1 is maintained. Since no adhesive remains on the device 20, rework is easy. After the photo-curing of the pressure-sensitive adhesive layer 2, the adhesive force between the pressure-sensitive adhesive layer 2 and the device 20 increases, so that it is difficult to peel the film substrate 1 from the device 20. May cause cohesive failure.

[Film substrate]
As the film substrate 1, a plastic film is used. In order to fix the film substrate 1 and the pressure-sensitive adhesive layer 2, it is preferable that the surface of the film substrate 1 provided with the pressure-sensitive adhesive layer 2 is not subjected to a 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 12 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, 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 It is particularly preferably 400 to 2700 kg / cm ² .

プラスチック Examples of the plastic material constituting the film substrate 1 include a polyester resin, a polyolefin resin, a cyclic polyolefin resin, a polyamide resin, a polyimide resin, polyetheretherketone, and polyethersulfone. In a reinforcing film for an optical device such as a display, the film substrate 1 is preferably a transparent film. When the actinic light is irradiated from the side of the film substrate 1 to cure the pressure-sensitive adhesive layer 2, the film substrate 1 may have transparency to actinic light used for curing the pressure-sensitive adhesive layer 2. preferable. 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 only needs to have transparency to actinic rays, and the film substrate 1 may not be transparent to actinic rays.

表面 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. As described above, in order to fix the film substrate 1 and the pressure-sensitive adhesive layer 2, it is preferable that a release layer is not provided on the surface of the film substrate 1 where the pressure-sensitive adhesive layer 2 is provided.

[Adhesive layer]
The pressure-sensitive adhesive layer 2 fixed and laminated on the film substrate 1 is made of a photocurable composition containing a base polymer, a photocuring agent and a photopolymerization initiator. Since the pressure-sensitive adhesive layer 2 has a small adhesive force with an adherend such as a device or a device component before light curing, rework is easy. Since the pressure-sensitive adhesive layer 2 improves the adhesive strength to the adherend by light curing, the reinforcing film is hardly peeled off from the device surface even when the device is used, and is excellent in adhesion reliability.

(4) The photocurable pressure-sensitive adhesive hardly hardens in a general storage environment, and is hardened by irradiation with actinic rays such as ultraviolet rays. Therefore, the reinforcing film of the present invention has an advantage that the curing timing of the pressure-sensitive adhesive layer 2 can be arbitrarily set, and the lead time of the process can be flexibly accommodated.

<Wetting speed>
Wetting rate is preferably more than 0.3 cm ² / s for glass reinforcing film, more preferably at least 0.35 cm ² / sec, 0.4 cm more preferably more than ² / s, particularly preferably at least 0.45 cm ² / sec . The wetting speed is from the state in which the pressure-sensitive adhesive layer at one end in the longitudinal direction of the test piece having a width of 25 mm x the length of 150 mm is brought into contact with the glass plate, and the pressure-sensitive adhesive layer of the test piece is brought into contact with the glass plate in the longitudinal direction. It is a value calculated based on the following formula from the wetting and spreading time until the wetting and spreading in a range of 100 mm in length from one end to the other end and the measurement area: 2.5 cm × 10 cm = 25 cm ² .
Wetting speed (cm ² / sec) = measured area (25 cm ² ) / wetting spread time (sec)
The higher the wetting speed, the easier the adhesive spreads when the reinforcing film is bonded to the adherend, and the more the bonding interface can suppress the incorporation of air bubbles and foreign substances, thereby improving the bonding workability. . Considering the workability at the time of bonding to the adherend, the higher the wetting speed, the better. On the other hand, a pressure-sensitive adhesive layer (photocurable composition) having a high wetting rate is likely to have poor appearance due to bleed-out of the photocurable agent. In addition, the pressure-sensitive adhesive layer having a large wetting rate has a surface close to a liquid state and may have poor initial adhesion to an adherend such as glass, and the compatibility of the composition is low. Even if it is performed, the adhesiveness may not be sufficiently increased. Therefore, wetting rate for the glass of the reinforcement film is preferably 4 cm ² / sec or less, 3.5 cm, more preferably less than ² / sec, more preferably 3 cm ² / sec or less, particularly preferably 2.5 cm ² / sec.

<Adhesive strength>
At the time of rework, from the viewpoint of facilitating peeling from the adherend and preventing adhesive residue on the adherend after peeling the reinforcing film, the reinforcing film before the pressure-sensitive adhesive layer 2 is cured with respect to the glass plate. The adhesive strength is preferably less than 1 N / 25 mm, more preferably 0.8 N / 25 mm or less, further preferably 0.7 N / 25 mm or less, and particularly preferably 0.6 N / 25 mm or less. From the viewpoint of preventing peeling of the reinforcing sheet from the adherend during storage and handling, the adhesive strength of the reinforcing film to the glass plate is preferably at least 0.03 N / 25 mm, more preferably at least 0.05 N / 25 mm, 0.1 N / 25 mm or more is more preferable, and 0.2 N / 25 mm or more is particularly preferable.

From the viewpoint of adhesion reliability in practical use of the device, the adhesive strength of the reinforcing film after photocuring the pressure-sensitive adhesive layer 2 to the glass plate is preferably 1 N / 25 mm or more, more preferably 2 N / 25 mm or more, and more preferably 3 N / 25 mm or more. Is more preferred. The adhesive strength after photocuring the pressure-sensitive adhesive layer 2 is preferably twice or more, more preferably three times or more, and even more preferably five times or more the adhesive strength before the photocurable pressure-sensitive adhesive layer 2 is cured.

<Thickness>
The thickness of the pressure-sensitive adhesive layer 2 is, for example, about 1 to 300 μm. As the thickness of the pressure-sensitive adhesive layer 2 increases, the adhesiveness to an adherend tends to improve. On the other hand, when the thickness of the pressure-sensitive adhesive layer 2 is excessively large, the fluidity before photo-curing 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, still more preferably 10 to 40 μm, and particularly preferably 13 to 30 μm.

<Transparency>
When the reinforcing film is used for 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, further preferably 0.7% or less, and particularly preferably 0.5% or less.

<Composition>
The pressure-sensitive adhesive layer 2 is a photocurable composition containing a base polymer, a photocuring agent, and a photopolymerization initiator. From the viewpoint of setting the adhesiveness and the wetting rate of the pressure-sensitive adhesive layer 2 before the photocuring to an appropriate range, it is preferable that a crosslinked structure is introduced into the base polymer.

(Base polymer)
The base polymer is a 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 a base polymer because of its excellent optical transparency and adhesiveness, and easy control of the adhesiveness, and 50% by weight of the pressure-sensitive adhesive composition. % Or more is preferably an acrylic polymer.

As the acrylic polymer, those containing an alkyl (meth) acrylate as a main monomer component are preferably used. In addition, in this specification, "(meth) acryl" means acryl and / or methacryl.

As the alkyl (meth) acrylate, an alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms is preferably used. The alkyl group of the alkyl (meth) acrylate may be straight-chain or branched. Examples of the alkyl (meth) acrylate 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) acrylate 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, isotridecyl (meth) acrylate, Tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate, pentadecyl (meth) acrylate, cetyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isooctadecyl (meth) acrylate , Nonadecyl (meth) acrylate, aralkyl (meth) acrylate, and the like.

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

(4) The acrylic base polymer preferably contains a monomer component having a crosslinkable functional group as a copolymer component. Examples of the monomer having a crosslinkable functional group include a hydroxy group-containing monomer and a carboxy group-containing monomer. The acrylic base polymer may have both a hydroxy group-containing monomer and a carboxy group-containing monomer as monomer components, or may have only one of them. The hydroxy group or carboxy group of the base polymer becomes a reaction point with a crosslinking agent described later. For example, when using an isocyanate-based cross-linking agent, it is preferable to contain a hydroxy group-containing monomer as a copolymerization component of the base polymer. When an epoxy crosslinking agent is used, 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 adhesive residue on the adherend during rework 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, and (meth) acrylate. Examples thereof include 8-hydroxyoctyl acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and 4- (hydroxymethyl) cyclohexylmethyl (meth) acrylate. Examples of the carboxy group-containing monomer include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like.

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, and more preferably 5 to 25% by weight. More preferably, it is 20% by weight.

The acrylic base polymer has N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-acryloylmorpholine as constituent monomer components. , N-vinylcarboxylic acid amides, N-vinylcaprolactam and the like.

The acrylic base polymer may contain a monomer component other than the above. The acrylic base polymer includes, as monomer components, for example, a cyano group-containing monomer, a vinyl ester monomer, an aromatic vinyl monomer, an epoxy group-containing monomer, a vinyl ether monomer, a sulfo group-containing monomer, a phosphate group-containing monomer, and an acid anhydride group-containing It may contain a monomer or the like.

重量 The weight average molecular weight of the acrylic base polymer is preferably from 100,000 to 5,000,000, more preferably from 300,000 to 3,000,000, and still more preferably from 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 the introduction of the crosslinked structure.

粘着 The adhesive tends to be harder as the content of the high Tg monomer component in the constituent components of the base polymer is larger. The high Tg monomer means a monomer having a high glass transition temperature (Tg) of a 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.); acryloyl morpholine (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; methacrylate (Tg: 228 ℃), acrylic acid (Tg: 106 ℃) acids such monomers; N- vinylpyrrolidone (Tg: 54 ℃), and the like.

In the acrylic base polymer, the content of the monomer having a homopolymer Tg of 40 ° C. or higher is preferably 1 to 50% by weight, more preferably 3 to 40% by weight, based on the total amount of the constituent monomer components. . In order to form a pressure-sensitive adhesive layer having appropriate hardness and excellent reworkability, it is preferable that the homopolymer has a Tg of 80 ° C. or higher as a monomer component of the base polymer. More preferably, it contains a monomer component at 100 ° C. or higher. In the acrylic base polymer, the content of the monomer having a homopolymer Tg of 100 ° C. or more based on the total amount of the constituent monomer components is preferably 0.1% by weight or more, more preferably 0.5% by weight or more. , More preferably 1% by weight or more, particularly preferably 3% by weight or more.

アクリル An acrylic polymer as a base polymer can be obtained by polymerizing the above monomer components by various known methods such as solution polymerization, emulsion polymerization and bulk polymerization. The solution polymerization method is preferred from the viewpoint of the balance of properties such as adhesive strength and holding power of the pressure-sensitive adhesive and cost. Ethyl acetate, toluene and the like are used as a solvent for solution polymerization. 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 agent is added to a solution obtained by polymerizing the base polymer, and if necessary, heating is performed to introduce a cross-linked structure. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a carbodiimide-based crosslinking agent, and a metal chelate-based crosslinking agent. These crosslinking agents react with functional groups such as a hydroxy group and a carboxy group introduced into the base polymer to form a crosslinked structure. Isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred because they have high reactivity with hydroxy groups and carboxy groups of the base polymer and can easily introduce a crosslinked structure.

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

多 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-based crosslinking agent may be a glycidyl group. Examples of the epoxy crosslinking agent include N, N, N ′, N′-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, 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 polyglycidide 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. Commercial 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.

使用 The amount of the crosslinking agent used may be appropriately adjusted according to the composition and molecular weight of the base polymer. The amount of the crosslinking agent to be used is about 0.01 to 10 parts by weight, preferably 0.1 to 7 parts by weight, more preferably 0.2 to 6 parts by weight, and still more preferably 100 parts by weight of the base polymer. 0.3 to 5 parts by weight. The value obtained by dividing the amount (parts by weight) of the crosslinking agent used per 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, more 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. Glue on the adherend during rework by increasing the amount of the cross-linking agent used to make the adhesive moderately harder than general acrylic optical transparent adhesives for permanent adhesion The remainder tends to decrease and the reworkability improves.

架橋 A cross-linking catalyst may be used to promote the formation of a cross-linked 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, and dibutyltin dilaurate And the like. The use amount of the crosslinking catalyst is generally 0.05 parts by weight or less based on 100 parts by weight of the base polymer.

(Light curing 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 photocured after being bonded to the adherend, the adhesive strength to the adherend is improved.

(4) As the photocuring agent, a photocurable monomer or a photocurable oligomer having two or more polymerizable functional groups in one molecule is used. The photocuring agent is preferably a compound having an ethylenically unsaturated bond such as a vinyl group or a (meth) acryloyl group as a polymerizable functional group. Further, the photo-curing agent is preferably a compound showing compatibility with the base polymer. It is preferable that the photocuring agent is liquid at normal temperature because it exhibits appropriate compatibility with the base polymer. When the photocuring agent is appropriately compatible with the base polymer and is uniformly dispersed in the composition, the wetting rate can be adjusted to an appropriate range.

相 The compatibility between the base polymer and the photocuring agent is mainly affected by the structure of the compound. The structure and compatibility of the compound can be evaluated by, for example, a Hansen solubility parameter. The smaller the difference between the solubility parameters of the base polymer and the photocuring agent, the higher the compatibility tends to be.

から It is preferable to use a polyfunctional (meth) acrylate as the photocuring agent because of its high compatibility with the acrylic base polymer. 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, ditrimethylolpropanetetra (meth) acrylate, ethoxylated pentaerythritol La (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaeristol poly (meth) acrylate, dipentaeristol 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.

相 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 tends to be. From the viewpoint of compatibility with the base polymer, the molecular weight of the photocuring agent is preferably 1500 or less, and more preferably 1000 or less.

種類 The type and content of the photocuring agent affect the adhesive strength 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 adhesive strength after photocuring tends to be larger. In light of enhancing the adhesive strength after photocuring, the functional group equivalent (g / eq) of the photocuring agent is preferably equal to or less than 500, and more preferably equal to or less than 450. On the other hand, if the photocrosslinking density is excessively increased, the viscosity of the pressure-sensitive adhesive may decrease, and the adhesive strength may decrease. Therefore, the functional group equivalent of the photocuring agent is preferably 100 or more, more preferably 130 or more, and even more preferably 150 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 adhesive strength of the adhesive before photocuring. (Initial adhesive strength) tends to increase. In the use of the present invention, an excessive increase in the initial adhesive strength may lead to a decrease in reworkability. From the viewpoint of maintaining the adhesive strength between the pressure-sensitive adhesive layer 2 and the adherend before light curing in an appropriate range, the functional group equivalent of the light curing agent is preferably within the above range.

(4) The content of the photocuring agent in the pressure-sensitive adhesive composition is preferably from 10 to 50 parts by weight, more preferably from 13 to 40 parts by weight, and still more preferably from 15 to 40 parts by weight, based on 100 parts by weight of the base polymer. When the photocurable compound is included in the pressure-sensitive adhesive composition as an uncured monomer or oligomer, the photocurable pressure-sensitive adhesive layer 2 is obtained. In order to include the photocuring agent in an uncured state in the composition, it is preferable to add the photocuring agent to the polymer solution after polymerization of the base polymer.

When the base polymer of the pressure-sensitive adhesive layer and the photo-curing agent are not completely compatible, the liquid photo-curing agent is localized near the surface of the pressure-sensitive adhesive layer (adhesion interface with the adherend), and the weak boundary layer ( Weak Boundary Layer; WBL) is easily formed. When the WBL in which the photocuring agent is localized is formed, the surface of the pressure-sensitive adhesive layer has a strong liquid property, so that the wetting speed increases, and the workability of bonding to the adherend tends to improve. .

粘着 An adhesive having a high gel fraction with a highly crosslinked base polymer generally has a predominant elastic behavior and tends to have low wettability to an adherend. On the other hand, when the WBL is formed, the characteristics of the surface (adhesive interface) change while maintaining the bulk characteristics of the pressure-sensitive adhesive layer. That is, when the WBL is formed, the viscosity of the surface is increased while maintaining the “hardness” of the adhesive as a bulk property, so that the wetting speed at the time of bonding is improved, and There is a tendency that peeling from the adherend becomes easy.

If the compatibility between the base polymer and the photo-curing agent is excessively low, the photo-curing agent easily bleeds out on the surface of the pressure-sensitive adhesive layer, and WBL with a strong liquid property is formed on the surface of the pressure-sensitive adhesive layer, resulting in a large wetting speed. To rise. Therefore, the workability of bonding is improved, but the bleed-out photocuring agent may cause poor appearance and contamination of the adherend in some cases. Further, when the photocuring agent bleeds out to form a liquid WBL, the initial adhesive strength may be insufficient due to the difficulty in holding the step. When the compatibility between the photocuring agent and the base polymer is low, the adhesive properties as a bulk hardly increase even when the pressure-sensitive adhesive is photocured, and the adhesion reliability of the reinforcing film may be poor.

As described above, in a photocurable pressure-sensitive adhesive containing a base polymer and a photocuring agent, the wetting rate is an index of the bonding workability and also an index of the compatibility between the base polymer and the photocuring agent. When the wetting rate is low, the bonding workability is low, and bonding defects such as mixing of air bubbles and entrapment of foreign matter are likely to occur. On the other hand, if the wetting rate is excessively high, bleed out of the photocuring agent and poor adhesion are likely to occur. Therefore, as described above, wetting rate is preferably 0.3 ~ 4 cm ² / sec, more preferably 0.35 ~ 3.5 cm ² / sec, more preferably 0.4 ~ 3 cm ² / sec, 0.45 Particularly preferred is 秒 2.5 cm ² / sec.

(4) The wetting rate can be adjusted to the above range by adjusting the content of the photocuring agent, controlling the compatibility between the base polymer and the photocuring agent, and the like. The wetting rate tends to increase as the content of the photocuring agent in the photocurable pressure-sensitive adhesive composition increases. Also, the lower the compatibility between the base polymer and the photocuring agent, the higher the wetting rate tends to be. As described above, the compatibility between the base polymer and the photocuring agent can be adjusted by the similarity of their chemical structures (solubility parameter), the molecular weight of the photocuring agent, the functional group equivalent, and the like.

When the photocuring agent has a similar chemical structure, the larger the functional group equivalent (the larger the molecular weight of the molecular chain connecting the polymerizable functional groups), the lower the compatibility with the base polymer and the lower the wetting rate. Tend. For example, when the photocuring agent is polyethylene glycol diacrylate, the wetting rate tends to increase as the number of repeating units of ethylene oxide (EO) increases. From the viewpoint of adjusting the wetting rate to the above range, the number of repeating units of EO is preferably about 2 to 8, more preferably about 3 to 7.

(Photopolymerization initiator)
The photopolymerization initiator generates active species upon irradiation with actinic rays, and promotes the curing reaction of the photocuring agent. As the photopolymerization initiator, a photocationic initiator (photoacid generator), a photoradical initiator, a photoanion initiator (photobase generator), or the like is used depending on the type of the photocuring agent. When an ethylenically unsaturated compound such as a polyfunctional acrylate is used as the photo-curing agent, it is preferable to use a photo-radical initiator as the polymerization initiator.

(4) The photo-radical initiator generates radicals upon irradiation with actinic rays, and promotes the radical polymerization reaction of the photo-curing agent by the radical transfer from the photo-radical initiator to the photo-curing 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, and include hydroxyketones, benzyldimethylketals, aminoketones, and acylphosphines. Examples include oxides, benzophenones, and triazine derivatives containing a trichloromethyl group. The photo-radical initiator may be used alone or in combination of two or more.

When transparency is required for the pressure-sensitive adhesive layer 2, the photopolymerization initiator preferably has low sensitivity to light (visible light) having a wavelength longer than 400 nm. For example, the extinction coefficient at a wavelength of 405 nm is 1 × 10 ² [ [mLg ⁻¹ cm ⁻¹ ] or less is preferably used.

The content of the photopolymerization initiator in the pressure-sensitive adhesive layer 2 is preferably 0.01 to 5 parts by weight, more preferably 0.02 to 3 parts by weight, and more preferably 0.03 to 2 parts by weight based on 100 parts by weight of the base polymer. Parts are more preferred. The content of the photopolymerization initiator in the pressure-sensitive adhesive layer 2 is preferably 0.02 to 10 parts by weight, more preferably 0.05 to 7 parts by weight, and more preferably 0.1 to 5 parts by weight based on 100 parts by weight of the photocuring agent. Part by weight is more preferred.

(Other additives)
In addition to the components exemplified above, the adhesive layer contains a silane coupling agent, a tackifier, a plasticizer, a softener, a deterioration inhibitor, a filler, a colorant, an ultraviolet absorber, an antioxidant, and a surfactant. An additive such as an agent or an antistatic agent may be contained within a range that does not impair the characteristics of the present invention.

[Preparation of reinforcing film]
By laminating the photocurable pressure-sensitive adhesive layer 2 on the film substrate 1, a reinforcing film is obtained. The pressure-sensitive adhesive layer 2 may be formed directly 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.

The above-mentioned pressure-sensitive adhesive composition is subjected to roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, die coating, etc. The pressure-sensitive adhesive layer is formed by applying the composition on a base material and, if necessary, drying and removing the solvent. As a drying method, an appropriate method can be adopted as appropriate. The heating and drying temperature is preferably 40 ° C to 200 ° C, more preferably 50 ° C to 180 ° C, and even more preferably 70 ° C to 170 ° C. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, and even more preferably 10 seconds to 10 minutes.

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

ゲル The gel fraction is increased by introducing a crosslinked structure into the base polymer. The higher the gel fraction, the harder the pressure-sensitive adhesive, and there is a tendency that adhesive residue on the adherend is 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 of the pressure-sensitive adhesive layer 2 before the photocuring may be 70% or more or 75% or more. If the gel fraction of the pressure-sensitive adhesive layer 2 before the photocuring is excessively large, the anchoring force on the adherend is reduced, and the initial adhesive strength may be insufficient. Therefore, the gel fraction of the pressure-sensitive adhesive layer 2 before photocuring is preferably 95% or less, more preferably 90% or less, further preferably 85% or less, and particularly preferably 80% or less. The gel fraction can be determined as an insoluble component in a solvent such as ethyl acetate. Specifically, the gel component is immersed in ethyl acetate at 23 ° C. for 7 days, and the insoluble component is determined based on the sample before immersion. It is determined as a weight fraction (unit: weight%). Generally, the gel fraction of a polymer is equal to the degree of crosslinking, and the more crosslinked portions in the polymer, the greater the gel fraction.

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

(4) When forming the pressure-sensitive adhesive layer 2 on another substrate, the solvent is dried, and then the pressure-sensitive adhesive layer 2 is transferred onto the film substrate 1 to obtain a reinforcing film. The substrate used for forming the pressure-sensitive adhesive layer may be used as the separator 5 as it is.

プラスチック As the separator 5, a plastic film such as polyethylene, polypropylene, polyethylene terephthalate, or polyester film is preferably used. The thickness of the separator is usually about 3 to 200 μm, preferably about 10 to 100 μm. The contact surface of the separator 5 with the pressure-sensitive adhesive layer 2 may be subjected to a release treatment with a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based release agent, or a silica powder or the like. preferable. Since the surface of the separator 5 is subjected to the release treatment, when the film substrate 1 and the separator 5 are separated, separation 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 substrate 1. The state where the layer 2 is fixed is maintained.

[Use of reinforcing film]
The reinforcing film is used by being bonded to an adherend such as a device or a device component. By bonding the reinforcing film to the adherend, appropriate rigidity is given to the adherend, so that an improvement in handleability and an effect of preventing breakage are expected. Since the reinforcing film of the present invention has a higher wetting rate than a general adhesive sheet for permanent adhesion, it is possible to suppress the entrapment of air bubbles and foreign substances when bonding the reinforcing film to the adherend, Excellent workability. In addition, since the reinforcing film has an appropriate wetting speed and an initial adhesive force, peeling from the adherend during storage and handling can be suppressed.

(4) In the device manufacturing process, when a reinforcing film is bonded to a work-in-progress, the reinforcing film may be bonded to a large-size work-in-process before being cut into a product size. A reinforcing film may be bonded to a mother roll of a device manufactured by a roll-to-roll process by a roll-to-roll process.

被 The adherend to which the reinforcing film is attached is not particularly limited, and includes various electronic devices, optical devices, and components thereof. As devices become more highly integrated, smaller, lighter, and thinner, the thickness of members constituting the device tends to decrease. As the thickness of the constituent members is reduced, bending and curling due to stress and the like at the lamination interface are likely to occur. In addition, bending due to its own weight is likely to occur due to the reduction in thickness. By attaching the reinforcing film, rigidity can be imparted to the adherend, so that bending, curling, bending, and the like due to stress, own weight, and the like are suppressed, and handling properties are improved. Therefore, by attaching the reinforcing film to the work-in-progress in the device manufacturing process, it is possible to prevent defects and defects during transportation and processing by an automated device.

In automatic transfer, contact between the work in process to be transferred and the transfer arm, pins, etc. is unavoidable. Further, in order to adjust the shape and remove unnecessary parts, there is a case where a work in process is cut. In a highly integrated, small, lightweight, and thin device, breakage due to local concentration of stress is likely to occur at the time of contact or cutting with a transport device or the like. In a device manufacturing process in which a plurality of members are stacked, not only members are sequentially stacked, but also a part of the members, process materials, and the like may be peeled off from a work-in-progress. When the member is thinned, stress is locally concentrated on the peeled portion and the vicinity thereof, which may cause breakage or dimensional change. Since the reinforcing film 10 has a stress dispersibility due to the pressure-sensitive adhesive layer 2, the reinforcing film 10 is attached to the object to be conveyed and the object to be processed, so that appropriate rigidity is imparted and stress is reduced. Dispersion can prevent defects such as cracks, cracks, peeling, and dimensional changes.

(4) The reinforcing film 10 may be bonded to the entire surface of the adherend 20 or may be selectively bonded only to a portion requiring reinforcement. After the reinforcing film is attached to the entire surface of the adherend, the reinforcing film may be cut off at a portion that does not require reinforcement, and may be separated from the surface of the adherend. Before the treatment for increasing the adhesive strength of the pressure-sensitive adhesive layer 2, the reinforcing film is temporarily attached to the surface of the adherend, so that the reinforcing film 10 can be easily peeled off from the surface of the adherend 20.

<Characteristics of pressure-sensitive adhesive layer before light curing>
(Adhesive strength)
As described above, from the viewpoint of exhibiting appropriate adhesiveness to the adherend, and easy to peel off from the adherend during rework and preventing the adhesive film from remaining on the adherend after peeling off the reinforcing film. The adhesive strength of the pressure-sensitive adhesive layer 2 to the glass plate before light curing is preferably 0.03 N / 25 mm or more and less than 1 N / 25 mm, more preferably 0.05 to 0.8 N / 25 mm, and 0.1 to 0.7 N. / 25 mm is more preferable, and 0.2 to 0.6 N / 25 mm is particularly preferable. It is preferable that the adhesive strength of the reinforcing film to the polyimide film be in the above range before the pressure-sensitive adhesive layer 2 is cured by light. 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 used, and from the viewpoint of heat resistance and dimensional stability, generally, And a polyimide film. The reinforcing film in which the pressure-sensitive adhesive layer 2 has the above-mentioned adhesive strength to the polyimide film as a substrate is easy to peel off from the polyimide adherend before the light-curing of the pressure-sensitive adhesive layer 2 and adheres after the light-curing. Excellent reliability.

(Storage modulus)
The pressure-sensitive adhesive layer 2 preferably has a shear storage modulus G ′ _i at 25 ° C. before light curing of 1 × 10 ⁴ to 1.2 × 10 ⁵ Pa. The shear storage elastic modulus (hereinafter simply referred to as “storage elastic modulus”) is determined under the conditions of a frequency of 1 Hz according to the method described in JIS K7244-1 “Plastics—Testing method for dynamic mechanical properties”. It can be obtained by reading a value at a predetermined temperature when measured at a heating rate of 5 ° C./min in the range of 50 to 150 ° C.

In a substance exhibiting viscoelasticity such as an adhesive, the storage elastic modulus G ′ is used as an index indicating the degree of hardness. The storage elastic modulus of the pressure-sensitive adhesive layer has a high correlation with the cohesive force, and the higher the cohesive force of the pressure-sensitive adhesive, the greater the anchoring force to the adherend. If the storage elastic modulus of the pressure-sensitive adhesive layer 2 before light curing is 1 × 10 ⁴ Pa or more, the pressure-sensitive adhesive has sufficient hardness and cohesive force, has an appropriate wetting speed, and is reinforced from the adherend. When the film is peeled, adhesive residue on the adherend is hardly generated. When the storage elastic modulus of the pressure-sensitive adhesive layer 2 is large, it is possible to suppress the pressure-sensitive adhesive from protruding from the end face of the reinforcing film. If the storage elastic modulus of the pressure-sensitive adhesive layer 2 before light curing 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. In addition, cohesive failure of the pressure-sensitive adhesive layer and adhesive residue on the surface of the adherend hardly occur. From the viewpoint of enhancing the reworkability of the reinforcing sheet and suppressing adhesive residue on the adherend during rework, the storage elastic modulus G ′ _i of the pressure-sensitive adhesive layer 2 at 25 ° C. before light curing is 3 × 10 ⁴ to 1 × 10 ⁵ Pa is more preferred, and 4 × 10 ⁴ to 9.5 × 10 ⁴ Pa is even more preferred.

<Light curing of the pressure-sensitive adhesive layer>
By bonding the reinforcing film 10 to the adherend 20 and irradiating the pressure-sensitive adhesive layer 2 with actinic rays, the pressure-sensitive adhesive layer 2 is light-cured. Actinic rays include ultraviolet light, visible light, infrared light, X-rays, α-rays, β-rays, and γ-rays. Ultraviolet rays are preferable as the actinic rays, since curing of the pressure-sensitive adhesive layer in the storage state can be suppressed and curing is easy. The irradiation intensity and irradiation time of the actinic ray may be appropriately set according to the composition and thickness of the pressure-sensitive adhesive layer. Irradiation of the actinic ray to the pressure-sensitive adhesive layer 2 may be performed from any of the film substrate 1 side and the adherend 20 side, or may be performed from both sides.

<Characteristics of pressure-sensitive adhesive layer after light curing>
(Adhesive strength)
As described above, from the viewpoint of adhesion reliability in practical use of the device, the adhesive force of the pressure-sensitive adhesive layer 2 to the glass plate before light curing is preferably 1 N / 25 mm or more, more preferably 2 N / 25 mm or more, and more preferably 3 N / 25 mm or more. 25 mm or more is more preferable. The reinforcing film preferably has an adhesive strength to the polyimide film in the above range after the pressure-sensitive adhesive layer 2 is cured. The adhesive strength between the pressure-sensitive adhesive layer 2 and the adherend after light curing is preferably twice or more, more preferably three times or more, and more preferably five times the adhesive strength between the pressure-sensitive adhesive layer 2 and the adherend before light curing. The above is more preferred.

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 adhesive reliability is obtained. . On the other hand, when the storage elastic modulus is excessively large, the pressure-sensitive adhesive does not easily spread and spread, and the contact area with the adherend decreases. Further, since the stress dispersibility of the pressure-sensitive adhesive decreases, the peeling force tends to propagate to the bonding interface, and the bonding force with the adherend tends to decrease. Therefore, the storage modulus G _'f at 25 ° C. after light curing of the adhesive layer 2 is preferably 2 × ¹⁰ 6 Pa or less. From the viewpoint of enhancing the adhesion reliability of the reinforcing sheet after the photocuring of 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. ⁶ Pa is more preferred.

The ratio G ′ _f / G ′ _i of the storage modulus at 25 ° C. before and after photocuring of the pressure-sensitive adhesive layer 2 is preferably 2 or more. If G ′ _f is at least twice as large as G ′ _i , the increase in G ′ due to photocuring is large, and it is possible to achieve both reworkability before photocuring and adhesion reliability after photocuring. G ′ _f / G ′ _i is more preferably 4 or more, still more preferably 8 or more, 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' Is excessively large, which tends to lead to a decrease in bonding reliability. Therefore, G ' _f / G' _i is preferably 100 or less, more preferably 40 or less, still more preferably 30 or less, and particularly preferably 25 or less.

The adherend 20 to which the reinforcing film 10 has been attached may be subjected to an autoclave treatment for the purpose of improving the affinity of the lamination interface of the plurality of laminated members or the like, or a heat treatment such as thermocompression bonding for joining circuit members. is there. When such a heat treatment is performed, it is preferable that the pressure-sensitive 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, The pressure is more preferably 1 × 10 ⁵ Pa or more. In order to prevent the adhesive from protruding during heating and to prevent a decrease in adhesive strength during heating, the storage elastic modulus at 100 ° C. of the adhesive layer 2 after photocuring is 60% of the storage elastic modulus at 50 ° C. Or more, more preferably 65% or more, still more preferably 70% or more, and particularly preferably 75% or more.

補強 In the reinforcing film of the present invention, the pressure-sensitive adhesive layer 2 is photocurable, and the curing timing 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 attached to the adherend and before the adhesive is photo-cured. It is possible to respond flexibly.

(4) The photo-curing of the pressure-sensitive adhesive layer 2 causes the reinforcing film 10 to be firmly adhered to the adherend 20. Even if external force is suddenly applied by dropping the device, placing a heavy object on the device, or hitting a flying object on the device, the reinforcing film is attached to prevent damage to the device it can. Further, since the pressure-sensitive adhesive layer is firmly adhered, the reinforcing film is hardly peeled off even during long-term use, and is excellent in reliability.

(4) The present invention is further described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Polymerization of base polymer]
<Polymer A>
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas introduction tube, as a monomer, 63 parts by weight of 2-ethylhexyl acrylate (2EHA), 15 parts by weight of N-vinylpyrrolidone (NVP), and methyl methacrylate (MMA) 9 parts by weight, 13 parts by weight of hydroxyethyl acrylate (HEA), 0.2 parts by weight of azobisisobutyronitrile as a polymerization initiator, and 233 parts by weight of ethyl acetate as a solvent were charged, and nitrogen gas was flown thereinto, followed by stirring. For about 1 hour, the atmosphere was replaced with nitrogen. Thereafter, the mixture was heated to 60 ° C. and reacted for 7 hours to obtain a solution of acrylic polymer A.

<Polymer B>
The charged amounts of the monomers were changed to 95 parts by weight of butyl acrylate (BA) and 5 parts by weight of acrylic acid (AA). Otherwise, polymerization was carried out in the same manner as in Polymer A to obtain a solution of acrylic polymer B.

<Polymer C>
As the polyol, 85 parts by weight of a polyether polyol having three hydroxyl groups and having a number average molecular weight of 10,000 (“S3011” manufactured by Asahi Glass) and 13 parts by weight of a polyether polyol having three hydroxyl groups (“SANNIX GP3000” manufactured by Sanyo Chemical) And 2 parts by weight of a polyether polyol having three hydroxyl groups and having a number average molecular weight of 1000 ("SANIX GP1000" manufactured by Sanyo Chemical Industries, Ltd.). As a polyisocyanate compound, isocyanurate of hexamethylene diisocyanate ("Coronate HX" manufactured by Tosoh Corporation) 18 parts by weight, 0.04 parts by weight of iron (III) acetylacetonate as a catalyst, and 210 parts by weight of ethyl acetate as a diluting solvent were mixed and stirred at room temperature to obtain a urethane polymer C solution.

[Example 1]
(Preparation of adhesive composition)
3.3 parts by weight of a solution of acrylic polymer A (300 parts by weight of solid content) in a 75% ethyl acetate solution of trimethylolpropane adduct of xylylene diisocyanate as an isocyanate-based cross-linking agent (“Takenate D110N” manufactured by Mitsui Chemicals) 3.3 Parts by weight (solid content: 2.5 parts by weight), 0.005 parts by weight of iron (III) acetylacetonate as a crosslinking catalyst, and 20 parts by weight of "Aronix M-321" manufactured by Toagosei Co., Ltd. as a photocuring agent (polyfunctional acrylic monomer). And 0.1 part by weight of 1-hydroxycyclohexylphenyl ketone (“IRGACURE 184” manufactured by BASF) as a photopolymerization initiator was added thereto, followed by stirring to prepare a photocurable acrylic pressure-sensitive adhesive solution.

(Preparation of reinforcing film)
The above-mentioned pressure-sensitive adhesive composition was applied using a fountain roll onto a 75 μm-thick polyethylene terephthalate film (“Lumirror S10” manufactured by Toray Co., Ltd.) that had not been subjected to surface treatment so that the thickness after drying was 25 μm. After drying at 130 ° C. for 1 minute to remove the solvent, a release-treated surface of a separator (a 25 μm-thick polyethylene terephthalate film whose surface was subjected to silicone release treatment) was adhered to the pressure-sensitive adhesive applied surface. Thereafter, an aging treatment is carried out for 4 days in an atmosphere of 25 ° C., crosslinking is advanced, a photocurable pressure-sensitive adhesive sheet having a thickness of 25 μm is fixedly laminated on the film substrate, and a reinforcing film on which a separator is temporarily attached is placed on the film. Obtained.

[Examples 2 to 7 and Comparative Examples 1 to 4]
In the preparation of the pressure-sensitive adhesive composition, a reinforcing film was produced in the same manner as in Example 1, except that the type of the photocuring agent was changed as shown in Table 1. In Comparative Example 4, the amount of the isocyanate-based crosslinking agent was changed, and the photo-curing agent was not added.

Example 8
0.5 parts by weight of a tetrafunctional epoxy crosslinking agent (“Tetrad C” manufactured by Mitsubishi Gas Chemical) in 300 parts by weight of a solution of the acrylic polymer B (100 parts by weight of solid content), and Shin-Nakamura Chemical Industry as a polyfunctional acrylic monomer 20 parts by weight of “NK Ester A-200” manufactured by BASF and 0.1 part by weight of “IRGACURE 184” manufactured by BASF were added as a photopolymerization initiator to prepare a photocurable acrylic pressure-sensitive adhesive solution. Using this adhesive solution, a reinforcing film was obtained in the same manner as in Example 1.

[Comparative Example 5]
Using a fountain roll, apply a solution of urethane-based polymer C on a 75 μm-thick polyethylene terephthalate film not subjected to surface treatment so that the thickness after drying becomes 25 μm, and then dry at 130 ° C. for 1 minute to remove the solvent. After the removal, the release-treated surface of the separator was bonded to obtain a reinforcing film.

[Evaluation]
The wetting speed and the adhesive strength to the glass plate of the reinforcing films of Examples and Comparative Examples were evaluated by the following methods. Each of the following evaluations was performed in an environment of a class 10000 clean room (temperature 23 ° C., humidity 50% RH).

<Wetting speed>
A state in which a pressure-sensitive adhesive layer at one end in the length direction of a test piece obtained by peeling and removing a separator from the surface of a reinforcing film cut into a width of 25 mm and a length of 150 mm is in contact with a glass plate ("Micro slide glass S" manufactured by Matsunami Glass Industry Co., Ltd.) The other end of the test piece was held by a hand so that the angle between the glass plate and the test piece was 20 to 30 °, and the hand was released from the test piece, and the adhesive layer of the test piece came into contact with the glass plate. The state of wetting and spreading from one end to the other in the length direction is recorded with a video camera, and the time required for the test piece to spread in a range of 100 mm (area 25 cm ² ) in the length direction is obtained. Was calculated.
Wetting speed (cm ² / sec) = measured area (25 cm ² ) / wetting spread time (sec)

<Adhesive strength>
A test piece obtained by peeling and removing the separator from the surface of the reinforcing film cut into a width of 25 mm and a length of 100 mm was bonded to a glass plate using a hand roller to obtain a test sample before light curing. The test sample obtained by irradiating ultraviolet light from the PET film side of the test sample and photocuring the pressure-sensitive adhesive layer was used as the test sample after photocuring. Using these test samples, the test piece was held by a chuck, and a 180 ° peel of the reinforcing film was performed at a tensile speed of 300 mm / min, and the peel strength was measured.

Table 1 shows the composition of the pressure-sensitive adhesive of each reinforcing sheet and the evaluation results. The amounts of the crosslinking agent and the photocuring agent in Table 1 are the amounts (parts by weight) based on 100 parts by weight of the base polymer. Details of the photocuring agent in Table 1 are as follows.

APG700: "NK ester APG-700" manufactured by Shin-Nakamura Chemical Co., Ltd., polypropylene glycol # 700 (n = 12) diacrylate; functional group equivalent 404 g / eq
A200: "NK ester A-200" manufactured by Shin-Nakamura Chemical Co., Ltd., polyethylene glycol # 200 (n = 4) diacrylate; functional group equivalent: 154 g / eq
A400: "NK ester A-400" manufactured by Shin-Nakamura Chemical Co., Ltd., polyethylene glycol # 400 (n = 9) diacrylate; functional group equivalent 254 g / eq
A600: "NK ester A-600" manufactured by Shin-Nakamura Chemical Co., Ltd., polyethylene glycol # 600 (n = 14) diacrylate; functional group equivalent 354 g / eq
AM130G: "NK ester AM-130G" manufactured by Shin-Nakamura Chemical Industry, methoxypolyethylene glycol # 550 (n = 13) monoacrylate M321: "Aronix M-321" manufactured by Toagosei, modified with trimethylolpropane propylene oxide (n = 2) Triacrylate; functional group equivalent 187 g / eq
M350: “Aronix M-350” manufactured by Toagosei Co., Ltd., trimethylolpropane ethylene oxide (n = 1) modified triacrylate; functional group equivalent 129 g / eq
M360: "Aronix M-360" manufactured by Toagosei Co., Ltd., trimethylolpropane ethylene oxide (n = 2) modified triacrylate; functional group equivalent: 159 g / eq
PTG9A: "Fancryl FA-PTG9A" manufactured by Hitachi Chemical, polytetramethylene glycol (n = 9) diacrylate; functional group equivalent 387 g / eq
321A: "Fancryl FA-321A" manufactured by Hitachi Chemical, ethylene oxide (n = 10) -modified bisphenol A diacrylate; functional group equivalent 388 g / eq

The reinforcing films of Comparative Examples 1 to 3 exhibited high wettability to the glass plate and high wettability to the adherend, but the surface of the pressure-sensitive adhesive layer was clouded, and bleed out of the photocuring agent was observed. . In these comparative examples, the adhesive strength before light curing was insufficient, and the adhesive strength after light curing was also insufficient. The reinforcing film of Comparative Example 5 using a urethane-based pressure-sensitive adhesive showed a higher wetting rate than Comparative Examples 1 to 3, but had insufficient adhesion to a glass plate as in Comparative Examples 1 to 3. It could not be used as a reinforcing film for permanent adhesion to an adherend.

The reinforcing film of Comparative Example 4 using an adhesive containing no photocuring agent showed high adhesive strength when pressed against a glass plate using a hand roller, but was only placed on the glass plate without applying pressure. In this case, the pressure-sensitive adhesive did not spread on the surface of the glass plate, and the wetting speed could not be measured.

補強 The reinforcing films of Examples 1 to 8 exhibited an appropriate wetting rate with respect to the glass plate, had an adhesive strength before light curing within an appropriate range, and had both adhesiveness and reworkability. Further, after the photocuring, it exhibited a high adhesive strength and was suitable as a reinforcing film having excellent adhesion reliability to the device.

In Example 4, Comparative Example 2 and Comparative Example 3, polyethylene glycol diacrylate was used as the photocuring agent. In Example 4, however, good characteristics were exhibited, whereas Comparative Example 2 and Comparative Example In No. 3, the wetting rate was excessively high, and the adhesion to the glass plate was insufficient. In Comparative Examples 2 and 3, the photocuring agent bleeds out to the surface due to the decrease in compatibility between the acrylic base polymer and the photocuring agent with the increase in the number of repeating units of ethylene oxide. It is considered that the property has decreased.

DESCRIPTION OF SYMBOLS 1 Film base material 2 Adhesive layer 5 Separator 10 Reinforcement film 20 Device (adherend)

Claims

Film base, comprising an adhesive layer fixedly laminated on one main surface of the film base,
The pressure-sensitive adhesive layer is a photocurable composition containing a base polymer, a photocuring agent having at least two polymerizable functional groups, and a photopolymerization initiator,
A reinforcing film having a wetting rate on a glass plate of 0.3 cm 2 / sec to 4 cm 2 / sec:
Here, the wetting speed is determined by changing the pressure-sensitive adhesive layer of the test piece from the state in which the pressure-sensitive adhesive layer at one end in the longitudinal direction of the test piece having a width of 25 mm x the length of 150 mm is in contact with the glass plate. It is a value calculated based on the following formula from the wetting and spreading time until wetting and spreading in a range of 100 mm in length from one end to the other end in the length direction, and a measurement area of 25 cm 2 .
Wetting speed (cm 2 / sec) = measured area (25 cm 2 ) / wetting spread time (sec)
The reinforcing film according to claim 1, wherein the adhesive strength to the glass plate before the pressure-sensitive adhesive layer is light-cured is 0.03 N / 25 mm or more and less than 1 N / 25 mm.
The reinforcing film according to claim 1 or 2, wherein the adhesive strength of the pressure-sensitive adhesive layer to the glass plate after photocuring is 1 N / 25 mm or more.
(4) The reinforcing film according to any one of (1) to (3), wherein a crosslinked structure is introduced into the base polymer.
(5) The reinforcing film according to any one of (1) to (4), wherein the photocurable composition contains an acrylic polymer as the base polymer.
The reinforcing film according to any one of claims 1 to 5, wherein the photocurable composition contains 10 to 50 parts by weight of the photocuring agent based on 100 parts by weight of the base polymer.
The reinforcing film according to any one of claims 1 to 6, wherein the photocuring agent is a polyfunctional (meth) acrylate.