WO2020066842A1 - Reinforcing film - Google Patents

Abstract

A reinforcing film (10) comprises a film substrate (1) and an adhesive layer (2) fixed/layered thereon. The adhesive layer is a photo-curable composition including a (meth)acrylic based polymer, a (meth)acrylic based oligomer, and a multifunctional compound. It is preferable that, when the adhesive layer is divided into three equal parts in the direction of thickness and the region that is furthest from the substrate side is taken as the surface layer region, the abundance of the multifunctional compound in the surface layer region accounts for at least 50% of the abundance of the multifunctional compound throughout the total thickness direction, and the abundance of the (meth)acrylic based oligomer in the surface layer region accounts for no more than 31% of the abundance of the (meth)acrylic based oligomer throughout the total thickness direction.

Description

Reinforcement film

The present invention relates to a reinforcing film attached to the surface of various devices and the like.

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 Document 1, an adhesive film used as a process material has low tackiness, can be easily peeled from an adherend, and does not cause adhesive residue on the adherend. Desired.

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 2013-185007 A JP-A-2017-132977 WO2015 / 163115 pamphlet

補強 It is hard to say that a reinforcing film whose adhesive strength to an adherend changes with time has sufficient flexibility with respect to the process lead time. 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 makes it easy to rework immediately after lamination with an adherend, and can arbitrarily set the time until the adhesive strength is improved after lamination with the adherend, and It is an object of the present invention to provide a reinforcing film that can be firmly bonded to an adherend by improving the force.

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 made of a photocurable composition containing a (meth) acrylic base polymer and a polyfunctional compound. The weight average molecular weight of the (meth) acrylic base polymer is preferably 100,000 or more. The (meth) acrylic base polymer preferably contains a hydroxy group-containing monomer as a monomer unit. The (meth) acrylic base polymer preferably has a crosslinked structure. The polyfunctional compound is a compound containing two or more polymerizable functional groups, and is preferably a polyfunctional (meth) acrylate.

光 The photocurable composition constituting the pressure-sensitive adhesive layer contains a (meth) acrylic oligomer having a weight average molecular weight of 1,000 to 50,000 in addition to the (meth) acrylic base polymer and the polyfunctional compound. The pressure-sensitive adhesive layer preferably contains 3 to 30 parts by weight of the (meth) acrylic oligomer and 0.5 to 30 parts by weight of the polyfunctional compound, based on 100 parts by weight of the (meth) acrylic base polymer.

When the pressure-sensitive adhesive layer is divided into three equal parts in the thickness direction, and the region farthest from the substrate side is defined as the surface region, the abundance of the polyfunctional compound in the surface region is the abundance of the polyfunctional compound in the entire thickness direction. 50% or more. The abundance of the (meth) acrylic oligomer in the surface region is 31% or less of the abundance of the (meth) acrylic oligomer in the entire thickness direction.

In the reinforcing film of the present invention, the pressure-sensitive adhesive layer is made of a photocurable composition, and the polyfunctional compound is unevenly distributed in the surface layer region. Is easy. Further, after the pressure-sensitive adhesive layer is light-cured, the pressure-sensitive adhesive layer exhibits high adhesive strength to an adherend, which contributes to reinforcement of the device and improvement of reliability.

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.

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 base film 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. 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 adherend, whereby the reinforcing film 10 is attached to the surface of the adherend. In this state, the pressure-sensitive adhesive layer 2 has not been cured yet, and the reinforcing film 10 (pressure-sensitive adhesive layer 2) is temporarily attached to the adherend. By photo-curing the pressure-sensitive adhesive layer 2, the adhesive force at the interface between the adherend and the pressure-sensitive adhesive layer 2 increases, and the adherend 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 separator 5 is peeled, peeling 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.

[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 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, more preferably 200 μm or less.

プ ラ ス チ ッ ク Examples of the plastic material constituting the film substrate 1 include a polyester resin, a polyolefin resin, a polyamide resin, and a polyimide resin. 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 film substrate 1 side to perform photocuring of the pressure-sensitive adhesive layer 2, the film substrate 1 preferably has transparency to actinic light used for curing the pressure-sensitive adhesive layer. . Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are preferably used because they have both mechanical strength and transparency.

[Adhesive layer]
By providing the 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 pressure-sensitive adhesive layer 2 is made of a photocurable composition. 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.

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.

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.

粘着 The pressure-sensitive adhesive composition (photocurable composition) constituting the pressure-sensitive adhesive layer 2 includes a (meth) acrylic base polymer, a (meth) acrylic oligomer, and a polyfunctional compound. From the viewpoint of increasing the efficiency of curing by irradiation with actinic rays, the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer 2 preferably contains a photopolymerization initiator.

The (meth) acrylic base polymer is a main component of the pressure-sensitive adhesive composition, and is a main factor that determines the adhesive strength of the pressure-sensitive adhesive. When peeling the reinforcing film from the adherend before light curing of the pressure-sensitive adhesive layer 2, from the viewpoint of facilitating peeling and preventing adhesive residue on the adherend, the (meth) acrylic base polymer has a crosslinked structure. Preferably, they have been introduced.

The polyfunctional compound has two or more polymerizable functional groups in one molecule. The polyfunctional compound has a function of increasing the cohesiveness of the pressure-sensitive adhesive after photocuring and improving the adhesive force with the adherend. In addition, since the amount of the polyfunctional compound in the surface layer region 2a of the pressure-sensitive adhesive layer 2 before the photocuring is larger than the amount of the polyfunctional compound in the other regions 2b and 2c in the thickness direction, the adhesiveness before the photocuring is increased. The adhesive force between the agent 2 and the adherend tends to be appropriately reduced, and the releasability of the reinforcing sheet from the adherend tends to be improved.

(Meth) acrylic oligomer has the function of adjusting the adhesive strength of the pressure-sensitive adhesive before and after photocuring by giving the composition in the thickness direction of the pressure-sensitive adhesive layer 2 before photocuring. In particular, when the abundance of the (meth) acrylic oligomer in the surface layer region 2a of the pressure-sensitive adhesive layer 2 before photocuring is smaller than the abundance of the (meth) acrylic oligomer in the middle layer region 2b and the base material side region 2c. In addition, the adhesive strength before light curing is small and excellent in releasability, and the adhesive strength is significantly increased by light curing, and the adhesive reliability tends to be improved.

In the following, the pressure-sensitive adhesive layer 2 is divided into three equal parts in the thickness direction, and a 1/3 region on the surface side (a region farthest from the film substrate 1) is a "surface region", and a 1/3 region in the center in the thickness direction. Is referred to as a “middle layer region”, and a region of one third of the film substrate 1 side is referred to as a “substrate side region”.

When the composition distribution of the pressure-sensitive adhesive layer 2 is measured from the surface layer side to the film substrate side by secondary ion mass spectrometry (SIMS), the pressure-sensitive adhesive layer 2 is present in the surface layer region 2a with respect to 100% of the total amount of each component. The ratio, the existence ratio in the middle layer region 2b, and the existence ratio in the base material side region 2c have a distribution. When the pressure-sensitive adhesive layer has no composition distribution in the thickness direction, the abundance ratio of each component is about 33% in each of the surface layer region 2a, the middle layer region 2b, and the base material side region 2c. On the other hand, in the pressure-sensitive adhesive layer 2 of the reinforcing film of the present invention, the abundance ratio of the polyfunctional compound in the surface region 2a is 50% or more, and the abundance ratio of the (meth) acrylic oligomer in the surface region 2a is 31. % Or less. In the present specification, the term "existence ratio of the polyfunctional compound in the surface layer region" means the proportion of the polyfunctional compound present in the surface layer region with respect to 100% of the total amount of the polyfunctional compound contained in the pressure-sensitive adhesive layer. The "abundance ratio of the acrylic oligomer in the surface layer region" means the ratio of the (meth) acrylic oligomer in the surface layer region to 100% of the total amount of the (meth) acrylic oligomer contained in the pressure-sensitive adhesive layer.

The content ratio of the (meth) acrylic oligomer in the surface layer region 2a is preferably 30% or less, more preferably 29% or less, further preferably 28% or less, and particularly preferably 27.5% or less. The abundance ratio of the (meth) acrylic oligomer in the surface region 2a is generally 15% or more, and is preferably 20% or more, more preferably 23% or more, and more preferably 25% or more from the viewpoint of increasing the transparency of the pressure-sensitive adhesive. More preferred.

存在 The abundance ratio of the polyfunctional compound in the surface region 2a is preferably 55% or more, more preferably 60% or more, further preferably 63% or more, and particularly preferably 65% or more. The abundance ratio of the polyfunctional compound in the surface layer region 2a is generally 95% or less, and is preferably 93% or less, more preferably 90% or less from the viewpoint of increasing the adhesive strength of the pressure-sensitive adhesive layer 2 to the adherend after photocuring. It is preferably at most 87%.

As the amount of the (meth) acrylic oligomer in the surface layer region 2a is smaller, the amount of the polyfunctional compound in the surface layer region 2a is larger, and the adhesive strength of the pressure-sensitive adhesive layer 2 to the adherend after photocuring tends to be higher. is there. On the other hand, if the amount of the polyfunctional compound in the surface layer region 2a is excessively large, the adhesive strength after photocuring may not be sufficiently increased.

Hereinafter, preferred embodiments of each component constituting the pressure-sensitive adhesive composition will be sequentially described.

<(Meth) acrylic base polymer>
The (meth) acrylic base polymer is a polymer having a weight average molecular weight of 100,000 or more containing a (meth) acrylic acid alkyl ester as a main monomer component. 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, eicosyl (meth) acrylate, and the like.

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

The (meth) 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. Especially, it is preferable to contain a hydroxy group-containing monomer as a copolymer component of the (meth) acrylic base polymer. The hydroxy group or carboxy group of the (meth) acrylic base polymer becomes a reaction point with a crosslinking agent described later. By introducing a crosslinked structure into the (meth) acrylic base polymer, the cohesive force is improved, the adhesiveness of the pressure-sensitive adhesive layer 2 is improved, and the fluidity of the pressure-sensitive adhesive is reduced. Adhesive residue on the body tends to decrease.

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 addition to the above, the (meth) acrylic base polymer may also use, as a copolymerization monomer component, an acid anhydride group-containing monomer, a caprolactone adduct of acrylic acid, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, or the like. The modifying monomers include vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N -Vinyl monomers such as vinylcarboxylic acid amides, styrene, α-methylstyrene, N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; (meth) acrylamide, N, N-dimethyl (meth) acrylamide (Meth) acrylamide-based monomers such as N, N, N-diethylacrylamide and N-isopropyl (meth) acrylamide; epoxy-containing acrylics such as glycidyl (meth) acrylate Noomers: glycol-based acrylic ester monomers such as polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate; tetrahydrofur (meth) acrylate (Meth) acrylate monomers such as frill, fluorine-containing (meth) acrylate, silicone (meth) acrylate and 2-methoxyethyl acrylate can also be used.

The ratio of the copolymerized monomer component in the (meth) acrylic base polymer is not particularly limited. For example, when a hydroxy group-containing monomer or a carboxy group-containing monomer is used as a copolymerizable monomer component for the purpose of introducing a crosslinking point, The total content of the monomer and the carboxy group-containing monomer is preferably about 1 to 20% by weight, more preferably 2 to 15% by weight, based on the total amount of the monomer components constituting the (meth) acrylic base polymer.

(4) A (meth) acrylic base polymer is obtained by polymerizing the above monomer component by various known methods such as solution polymerization, emulsion polymerization, bulk polymerization and the like. 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, various known ones such as azo type and peroxide type can be used. In order to adjust the molecular weight, a chain transfer agent may be used. The reaction temperature is usually 50 to 80 ° C, and the reaction time is usually 1 to 8 hours.

(4) From the viewpoint of imparting an appropriate holding force to the pressure-sensitive adhesive layer 2, the weight average molecular weight of the (meth) acrylic base polymer is preferably 100,000 or more. From the viewpoints of workability and transparency of the pressure-sensitive adhesive layer 2, the weight average molecular weight of the (meth) acrylic base polymer is preferably 2,000,000 or less. The weight average molecular weight of the (meth) acrylic base polymer is preferably 200,000 to 1.5 million, more preferably 400,000 to 1.2 million. The weight average molecular weight is a molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). When a crosslinked structure is introduced into the base polymer, the molecular weight of the (meth) acrylic base polymer before the introduction of the crosslinked structure is preferably within the above range.

(4) In order to obtain the pressure-sensitive adhesive layer 2 having appropriate adhesiveness to an adherend in a normal temperature environment, the glass transition temperature (Tg) of the (meth) acrylic base polymer in terms of the Fox formula is preferably 0 ° C. or lower. The Tg of the (meth) acrylic base polymer is preferably -80 to -10 ° C, more preferably -75 to -20 ° C, and still more preferably -70 to -20 ° C.

<Crosslinking agent>
From the viewpoint of giving the adhesive an appropriate cohesive force, it is preferable that a crosslinked structure is introduced into the (meth) acrylic base polymer. For example, a crosslinking agent is added to a solution obtained by polymerizing the (meth) acrylic base polymer, and a crosslinking structure is introduced by heating as necessary. 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 a functional group such as a hydroxy group introduced into the (meth) acrylic base polymer to form a crosslinked structure.

ポ リ Since a crosslinked structure can be introduced into the (meth) acrylic base polymer by heating, a polyisocyanate having two or more isocyanate groups in one molecule is preferable as the crosslinking agent. Examples of the polyisocyanate-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; Aromatic isocyanates such as diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate; trimethylolpropane / tolylenediisocyanate trimer adduct (for example, “Coronate L” manufactured by Tosoh Corporation), trimethylolpropane / hexa Methylene diisocyanate trimer adduct (eg, “Coronate HL” manufactured by Tosoh Corporation), xylylene diisocyanate trimethylolpropane adduct (eg, Mitsui Chemicals, Inc.) Ltd. "Takenate D110N", isocyanurate of hexamethylene diisocyanate (e.g., manufactured by Tosoh "Coronate HX", manufactured by Soken Chemical & Engineering Co., "Y-75") isocyanate adducts of the like.

使用 The amount of the crosslinking agent to be used may be appropriately adjusted according to the composition and molecular weight of the (meth) acrylic base polymer. The amount of the crosslinking agent used is 0.1 to 10 parts by weight, preferably 0.2 to 7 parts by weight, more preferably 0.3 to 5 parts by weight, based on 100 parts by weight of the (meth) acrylic base polymer. Parts, more preferably 1 to 4 parts by weight.

架橋 A cross-linking catalyst may be used to promote the formation of a cross-linked structure. Examples of the crosslinking catalyst include tetra-n-butyl titanate, tetraisopropyl titanate, ferric nasem, butyltin oxide, dibutyltin acetate, dibutyltin dilaurate, dioctyltin diacetate, dioctyltin distearate, and dioctyltin dilaurate. Metal-based cross-linking catalysts (particularly tin-based cross-linking catalysts) are exemplified. The use amount of the crosslinking catalyst is generally 0.05 parts by weight or less based on 100 parts by weight of the (meth) acrylic base polymer.

<Polyfunctional compound>
As the polyfunctional compound, a photocurable monomer or a photocurable oligomer is used. As the polyfunctional compound, a compound having two or more ethylenically unsaturated bonds in one molecule is preferable.

Since the affinity with the (meth) acrylic base polymer is high, it is preferable to use a polyfunctional (meth) acrylate as the polyfunctional compound. Polyfunctional (meth) acrylates include polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and glycerin di (meth) acrylate Esters of diol and (meth) acrylic acid, such as tricyclodecane dimethanol di (meth) acrylate; pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditri Methylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol poly (meth) acrylate, dipentaerythritol Esters of (meth) acrylic acid with polyol having three or more hydroxy groups such as oxa (meth) acrylate; urethane (meth) acrylate, epoxy (meth) acrylate, butadiene (meth) acrylate, isoprene (meth) acrylate, etc. And a compound having a polymerizable functional group other than the (meth) acryloyl group and the (meth) acryloyl group.

と し て As the polyfunctional compound, an ester of a modified product of a polyol with an alkylene oxide such as methylene oxide, ethylene oxide, or propylene oxide and a (meth) acryloyl group may be used. Examples of the ester of the modified alkylene oxide of the polyol and the (meth) acryloyl group include those in which one or more oxyalkylene groups are inserted between the polyol and the (meth) acryloyl group. The insertion of the oxyalkylene group increases the functional group equivalent of the polyfunctional compound (ie, decreases the number of functional groups per unit molecular weight), and changes the polarity of the molecule. In addition, the insertion of the oxyalkylene group changes the compatibility between the polyfunctional compound and the (meth) acrylic base polymer or the (meth) acrylic oligomer, and accordingly, the thickness direction in the pressure-sensitive adhesive layer before photocuring. In some cases, the adhesiveness of the pressure-sensitive adhesive after photocuring, and the like may change.

か ら From the viewpoint of increasing the adhesive strength after photocuring, the functional group equivalent (g / eq) of the polyfunctional compound is preferably 500 or less, more preferably 450 or less. 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 polyfunctional compound is preferably 100 or more, more preferably 130 or more, and even more preferably 150 or more. Further, when the functional group equivalent of the polyfunctional compound is small, the interaction between the (meth) acrylic base polymer and the polyfunctional compound is strong, and the adhesive force of the pressure-sensitive adhesive layer 2 before photocuring increases, and In some cases, it may be difficult to peel off. 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 polyfunctional compound is preferably within the above range. The molecular weight of the polyfunctional compound is preferably from 100 to 1,000.

The content of the polyfunctional compound in the pressure-sensitive adhesive composition is preferably 0.5 to 30 parts by weight, more preferably 1 to 20 parts by weight, and more preferably 2 to 15 parts by weight, based on 100 parts by weight of the (meth) acrylic base polymer. Parts are more preferred. When the polyfunctional compound is contained in an amount of 0.5 part by weight or more, the polyfunctional compound tends to be unevenly distributed in the surface layer portion 2a in the pressure-sensitive adhesive layer 2 before photocuring, and accordingly, the adhesive strength to the adherend is moderate. Tend to decrease. On the other hand, if the content of the polyfunctional compound in the pressure-sensitive adhesive composition is excessively large, a decrease in transparency due to bleed-out of the polyfunctional compound or a decrease in the viscosity of the pressure-sensitive adhesive after photocuring can provide a sufficient adhesive force. May not be. In order to include the polyfunctional compound in an uncured state in the composition, it is preferable to add the polyfunctional compound after polymerizing the (meth) acrylic base polymer.

<(Meth) acrylic oligomer>
The pressure-sensitive adhesive layer 2 contains a (meth) acrylic oligomer. The (meth) acrylic oligomer can act as a tackifier and contribute to improving the adhesive strength of the photocured pressure-sensitive adhesive to an adherend. In addition, in the present invention, the pressure-sensitive adhesive composition contains a (meth) acrylic oligomer in addition to the base polymer and the polyfunctional compound, so that the composition in the thickness direction of the pressure-sensitive adhesive layer 2 has a distribution, and the light-curing is performed. It has the function of adjusting the adhesive strength between the front and rear adhesives.

(Meth) acrylic oligomer is a polymer containing a (meth) acrylic monomer and is a component having a smaller weight average molecular weight than the above (meth) acrylic base polymer. The weight average molecular weight of the (meth) acrylic oligomer is from 1,000 to 50,000. The weight average molecular weight of the (meth) acrylic oligomer is preferably 30,000 or less from the viewpoint of maintaining a suitable affinity for the (meth) acrylic base polymer and the polyfunctional compound and maintaining the transparency of the pressure-sensitive adhesive layer 2. It is preferably 10,000 or less, more preferably 8,000 or less.

(Meth) acrylic oligomer contains (meth) acrylic acid alkyl ester as a main monomer component. The content of the alkyl (meth) acrylate is 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, based on the total amount of the monomer components constituting the (meth) acrylic oligomer. % By weight or more is more preferable. In a preferred embodiment, the (meth) acrylic oligomer contains substantially only a (meth) acrylic acid alkyl ester as a monomer component. The (meth) acrylic oligomer may contain two or more types of monomer components.

モ ノ マ ー The monomer component constituting the (meth) acrylic oligomer preferably does not form a crosslinked structure with the above-mentioned crosslinking agent. That is, the monomer component constituting the (meth) acrylic oligomer preferably does not contain a hydroxy group or a carboxy group.

The monomer component constituting the (meth) acrylic oligomer includes, for example, a linear or branched alkyl group having 1 to 20 carbon atoms exemplified above as the monomer component constituting the (meth) acrylic base polymer (meth) ) Acrylic acid alkyl esters. In addition, (meth) acrylates having an alicyclic group such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate; benzyl (meth) acrylate, 2-naphthyl (meth) acrylate (Meth) acrylates having an aromatic or heterocyclic group-containing group such as pentamethylpiperidine (meth) acrylate and 2-phenoxyethyl (meth) acrylate; methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, Monomer components such as cyclopentenyloxyethyl (meth) acrylate and tetrahydrofurfuryl methacrylate are also suitable as monomer components constituting the (meth) acrylic oligomer.

<Photo initiator>
The pressure-sensitive adhesive layer 2 preferably contains a photoinitiator. The photoinitiator generates an active species upon irradiation with actinic light and promotes a curing reaction of the polyfunctional compound. As the photoinitiator, a photocationic initiator (photoacid generator), a photoradical initiator, a photoanion initiator (photobase generator), or the like is used depending on the type of the polyfunctional compound. When a polyfunctional acrylate is used as the polyfunctional compound, it is preferable to use a photo radical initiator. Examples of the photoradical initiator include hydroxy ketones, benzyl dimethyl ketals, amino ketones, acyl phosphine oxides, benzophenones, and trichloromethyl group-containing triazine derivatives. The photoradical generator may be used alone or in combination of two or more. The content of the photopolymerization initiator in the pressure-sensitive adhesive layer 2 is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the total pressure-sensitive adhesive layer 2.

<Other additives>
In addition to the components exemplified above, the pressure-sensitive adhesive composition includes 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. Further, additives such as an antistatic agent may be contained within a range that does not impair the characteristics of the present invention.

<Formation of adhesive layer>
Roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating of the above pressure-sensitive adhesive composition containing a (meth) acrylic base polymer, a polyfunctional compound and a (meth) acrylic oligomer. A pressure-sensitive adhesive layer is formed by applying the composition on a substrate by bar coating, knife coating, air knife coating, curtain coating, lip coating, die coating, or the like, and optionally removing the solvent by drying. 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.

(4) The introduction of the crosslinked structure into the (meth) acrylic base polymer tends to increase the gel fraction of the pressure-sensitive adhesive layer 2. The higher the gel fraction of the pressure-sensitive adhesive layer 2, the harder the pressure-sensitive adhesive, and the more the adhesive film is peeled off from the adherend by rework or the like, the more the adhesive residue on the adherend tends to be suppressed. The gel fraction of the pressure-sensitive adhesive layer 2 before photocuring is preferably 20% or more, more preferably 30% or more, and even more preferably 40% 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 decreases, and the adhesive force may become 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.

(4) Even after the crosslinked structure is introduced into the (meth) acrylic base polymer by the crosslinker, the polyfunctional compound remains unreacted. When a (meth) acrylic oligomer having no reactive functional group with a cross-linking agent is used, the (meth) acrylic oligomer is formed without forming a chemical bond with the (meth) acrylic base polymer. , In the pressure-sensitive adhesive layer 2.

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. When the pressure-sensitive adhesive layer 2 is formed on another substrate, a reinforced film is obtained by transferring the pressure-sensitive adhesive layer 2 onto the film substrate 1 after drying the solvent. 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 3 to 200 μm, preferably 10 to 100 μm. The surface of the separator 5 that is in contact with the pressure-sensitive adhesive layer 2 is subjected to a release treatment using a release agent such as a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based release agent, or silica powder. Is preferred. 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.

As described above, the pressure-sensitive adhesive layer 2 before photocuring has a composition distribution in the thickness direction, and the abundance ratio of the polyfunctional compound in the surface layer region 2a is 50% or more, and the (meth) acrylic oligomer surface layer region The existence ratio in 2a is 31% or less. That is, the abundance of the polyfunctional compound and the abundance of the (meth) acrylic oligomer are smaller in the surface layer region (the bonding interface with the adherend) than in the middle layer region and the substrate side region.

When the low-molecular-weight polyfunctional compound is unevenly distributed in the surface layer region 2a, an adhesion inhibition layer (Weak \ Boundary \ Layer; @WBL) is formed at the bonding interface with the adherend, and the pressure-sensitive adhesive layer 2 before photocuring becomes a bulk. It is considered that the adhesive property to the adherend is small because the liquid property is strong at the bonding interface while maintaining the hardness. Furthermore, since the polyfunctional compound is unevenly distributed in the surface layer region 2a which is the adhesive interface with the adherend, it is considered that the cohesive force at the interface of the adherend is significantly increased due to the photocuring. By increasing the cohesive force of the pressure-sensitive adhesive layer at the interface of the adherend after photocuring, the adhesive force with the adherend is greatly increased, and the adhesion reliability of the reinforcing film is enhanced.

組成 It is considered that such a composition distribution in the thickness direction depends on the compatibility of the three components of the (meth) acrylic base polymer, the polyfunctional compound, and the (meth) acrylic oligomer. The compatibility between the (meth) acrylic base polymer and the polyfunctional compound is mainly affected by the structure of the compound. The structure and compatibility of the compounds can be assessed, for example, by Hansen solubility parameters.

The Hansen solubility parameter (HSP) is obtained by dividing a Hildebrand solubility parameter δ into three components of a dispersion term δ _d , a polarity term δ _p , and a hydrogen bond term δ _h , and is expressed in a three-dimensional space. Yes, the relationship of δ ² = δ _d ² + δ _p ² + δ _h ² holds. The dispersion term δ _d indicates the effect due to the dispersion force, the polarity term δ _p indicates the effect due to the dipole force, and the hydrogen bond term δ _h indicates the effect due to the hydrogen bond force. Distance Ra of the HSP of two materials, the difference .DELTA..delta _d of variance terms between the two materials, the difference .DELTA..delta _p polarity section and the difference .DELTA..delta _h of hydrogen ^{_{bond, Ra = {4Δδ d 2 +}} Δδ p 2 + Δδ h It is expressed by ² ｝ ^{1/2. The} smaller the Ra, the higher the compatibility, and the larger the Ra, the lower the compatibility.

Details of the Hansen solubility parameters are described in Charles M. Hansen, Hansen Solubility Parameters: A Users Handbook (CRC Press, 2007) .For substances whose literature values and the like are unknown, computer software Hansen Solubility Parameters It can be calculated using Practice II (HSPiP).

偏 The uneven distribution of the polyfunctional compound in the surface layer region is considered to depend on the compatibility between the (meth) acrylic base polymer, which is the main component of the pressure-sensitive adhesive composition, and the polyfunctional compound. That is, it is considered that the uneven distribution of the polyfunctional compound in the surface layer region is promoted by using the polyfunctional compound having an appropriately large HSP distance from the (meth) acrylic base polymer.

When the compatibility between the (meth) acrylic oligomer and the polyfunctional compound is low, the compatibility with the polyfunctional compound is low in the surface region of the (meth) acrylic oligomer due to the uneven distribution of the polyfunctional compound to the surface region. The existence ratio decreases. Therefore, by using a (meth) acrylic oligomer having a moderately large distance of the HSP from the polyfunctional compound, the (meth) acrylic oligomer has a relatively small (eg, 31% or less) adhesion ratio in the surface layer region. It is considered that the agent layer 2 can be formed. The compatibility with the (meth) acrylic base polymer, which is the main component of the pressure-sensitive adhesive composition, is also considered to be a factor that affects the amount of the (meth) acrylic oligomer in the surface layer region.

Considering these, by selecting the combination of the (meth) acrylic base polymer, the polyfunctional compound and the (meth) acrylic oligomer constituting the pressure-sensitive adhesive composition, the presence of the (meth) acrylic oligomer in the surface layer region The pressure-sensitive adhesive layer having a small amount and exhibiting high adhesiveness by light curing can be formed.

[Lamination and light curing of reinforcing sheet to adherend]
The reinforcing film of the present invention is used by being bonded to constituent members (work in process) of various devices and devices after completion. When a reinforcing film is bonded to a work-in-progress in a device manufacturing process, the reinforcement 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. The reinforcing film may be bonded to the entire surface of the adherend, or may be selectively bonded only to a portion requiring reinforcement. Further, after attaching the reinforcing film to the entire surface of the adherend, the reinforcing film may be cut off at a portion not requiring reinforcement, and the reinforcing film may be peeled off.

Before the photocuring of the pressure-sensitive adhesive, the adhesion between the pressure-sensitive adhesive layer and the adherend is small, and the reinforcing film is temporarily attached to the surface of the adherend, so that the reinforcing film can be easily removed from the surface of the adherend. It can be peeled off and has excellent reworkability. As described above, due to the uneven distribution of the polyfunctional compound in the surface layer region of the pressure-sensitive adhesive layer 2, the adhesiveness before photocuring tends to decrease.

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 and the adherend before light curing is 1 N / 25 mm. Is preferably 0.8 N / 25 mm or less, and more preferably 0.6 N / 25 mm or less. On the other hand, from the viewpoint of preventing peeling of the reinforcing sheet from the adherend during storage and handling, the adhesive strength between the pressure-sensitive adhesive layer 2 and the adherend before light curing is preferably 0.01 N / 25 mm or more, 0.05 N / 25 mm or more is more preferable, 0.15 N / 25 mm or more is more preferable, and 0.1 N / 25 mm or more is particularly preferable. The adhesive strength can be evaluated by a 180 ° peel test using a SUS304 plate as an adherend and a tensile speed of 300 mm / min.

(4) After bonding the reinforcing film to the adherend, the pressure-sensitive adhesive layer 2 is irradiated with actinic rays to light-cur the pressure-sensitive adhesive layer. 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.

From the viewpoint of adhesion reliability in practical use of the device, the adhesive force between the pressure-sensitive adhesive layer and the adherend after photocuring is preferably 5 N / 25 mm or more, more preferably 8 N / 25 mm or more, and further preferably 10 N / 25 mm or more. preferable. The adhesive force between the pressure-sensitive adhesive layer and the adherend after photocuring is preferably 10 times or more, more preferably 15 times or more, and more preferably 20 times or more the adhesive force between the pressure-sensitive adhesive layer 2 and the adherend before light curing. Is more preferred.

(4) As described above, in the pressure-sensitive adhesive layer 2 before the photo-curing, when the abundance ratio of the (meth) acrylic oligomer in the surface layer region is small, the adhesive strength tends to greatly increase due to the photo-curing. In addition, even when the pressure-sensitive adhesive layer 2 before light curing has a composition distribution in the thickness direction, in the pressure-sensitive adhesive layer after light curing, the abundance ratio of the (meth) acrylic oligomer is substantially uniform in the thickness direction. Often become. From this fact, the fact that the (meth) acrylic oligomer existing in the substrate side region and the middle layer region before the photocuring moves to the surface layer region with the photocuring is related to the improvement of the adhesive strength. It is estimated that

As the polymerization of the polyfunctional compound progresses by photocuring, the liquid properties of the polyfunctional compound unevenly distributed in the surface layer region become weaker, the WBL disappears, and the phase of the (meth) acrylic base polymer and the polyfunctional compound is reduced. The solubility increases. Accordingly, the compatibility between the (meth) acrylic oligomer and other components in the surface layer region becomes substantially equal to the compatibility between the (meth) acrylic oligomer and other components in the middle layer region and the substrate-side region. . As described above, with the progress of photocuring, the factor that caused the distribution of the abundance ratio of the (meth) acrylic oligomer in the thickness direction is eliminated, and the concentration of the (meth) acrylic oligomer in the surface region increases. . As described above, when the pressure-sensitive adhesive layer is photo-cured, the cohesive force accompanying polymerization of the polyfunctional compound unevenly distributed before the photo-curing increases in the surface layer region. In addition, an increase in the concentration of the (meth) acrylic oligomer acting as a tackifier in the surface layer region is also considered to contribute to the improvement of the adhesive strength of the photocured pressure-sensitive adhesive layer to the adherend.

た め Since the rigidity can be imparted to the adherend by bonding the reinforcing film, bending, curling, bending, and the like due to stress, own weight, and the like are suppressed, and handling properties are improved. For this reason, by attaching a reinforcing film to a work-in-progress in the device manufacturing process, it is possible to prevent defects and defects during transportation and processing. In addition, in the use of the device after completion, even if external force is suddenly applied due to dropping of the device, placing a heavy object on the device, collision of flying objects on the device, etc., the reinforcing film is bonded. By doing so, damage to the device can be prevented. Since the reinforcing film after the photocuring of the pressure-sensitive adhesive is firmly adhered to the device, the reinforcing film is hardly peeled off even during long-term use, and is excellent in reliability.

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. Is also flexible.

Hereinafter, the present invention is not limited to the following specific examples, which will be further described with reference to production examples of a reinforcing film including the pressure-sensitive adhesive composition of various formulations.

[Production of (meth) acrylic base polymer]
<Base polymer A>
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas introduction tube, 95.9 parts by weight of 2-ethylhexyl acrylate (2EHA), 4 parts by weight of 2-hydroxyethyl acrylate (2HEA), and acrylic 0.1 parts by weight of an acid (AA), 0.2 parts by weight of azobisisobutyronitrile as a polymerization initiator, and 200 parts by weight of ethyl acetate as a solvent are charged. A substitution was made. Thereafter, the mixture was heated to 70 ° C. and reacted for 6 hours to obtain a solution of the base polymer A. The weight average molecular weight of the base polymer A was 49.4 thousand.

<Base polymers B to H>
Solutions of base polymers B to H were obtained in the same manner as in the polymerization of base polymer A, except that the amount of charged monomers was changed as shown in Table 1.

Table 1 lists the charged monomer ratios of the base polymers A to H, the glass transition temperature (Tg), the weight average molecular weight (Mw), and the molecular weight distribution (Mw / Mn) of the polymers. In Table 1, the monomer components are described by the following abbreviations.
2EHA: 2-ethylhexyl acrylate (Tg of homopolymer: -70 ° C)
2HEA: 2-hydroxyethyl acrylate (Tg of homopolymer: -15 ° C)
BA: butyl acrylate (Tg of homopolymer: -55 ° C)
AM: acrylamide (Tg of homopolymer: 165 ° C)
AA: acrylic acid (Tg of homopolymer: 106 ° C.)

The Tg of the (meth) acrylic base polymer was calculated by the Fox equation from the Tg of the homopolymer of each monomer component and the mixing ratio of the monomers. The Mw (in terms of polystyrene) of the (meth) acrylic base polymer was measured using GPC (“HLC-8220GPC” manufactured by Tosoh Corporation) under the following conditions.
Sample concentration: 0.2% by weight (tetrahydrofuran solution)
Sample injection volume: 10 μL
Eluent: THF
Flow rate: 0.6 ml / min Measurement temperature: 40 ° C
Sample column: TSKguardcolumn SuperHZ-H (1) + TSKgel SuperHZM-H (2)
Reference column: TSKgel SuperH-RC (1)
Detector: RI

[Preparation of reinforcing film]
<Preparation of adhesive composition>
In the base polymer solution obtained by the production of the (meth) acrylic base polymer, 5 parts by weight of the (meth) acrylic oligomer and 100 parts by weight of the solid content of the (meth) acrylic base polymer, 10 parts by weight, 2 parts by weight of a cross-linking agent, and 0.1 part by weight of a photopolymerization initiator were added in a solid content ratio, respectively, and uniformly mixed to obtain a pressure-sensitive adhesive composition having a composition of 1 to 39 shown in Table 2. Was prepared. As a thermal crosslinking agent, a trimethylolpropane adduct of xylylene diisocyanate (75% ethyl acetate solution, “Takenate D110N” manufactured by Mitsui Chemicals, Inc.) was used. As a photopolymerization initiator, 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF) "Irgacure 184") was used.

As the (meth) acrylic oligomer, a polymer of tetrahydrofurfuryl methacrylate (THFMA), a polymer of n-butyl methacrylate (nBMA), or a polymer of isobornyl methacrylate (IBXMA) was used. In each case, the weight average molecular weight was about 3000.

As the polyfunctional compound, trimethylpropane triacrylate (TMPTA), trimethylpropane (EO) ₃ triacrylate (TMP (EO) ₃ TA), or trimethylpropane (EO) ₆ triacrylate (TMP (EO) ₆ TA) is used. Was. TMP (EO) ₃ TA is obtained by inserting an average of one ethylene oxide (an average of three in one molecule) between methylol and acryloyl, and TMP (EO) ₆ TA has an average between methylol and acryloyl. Two (an average of six in one molecule) ethylene oxide is inserted.

In Formulas 40 and 41, the pressure-sensitive adhesive composition was prepared without using a (meth) acrylic oligomer. In Formulations 42 to 44, a pressure-sensitive adhesive composition was prepared without using a polyfunctional compound and a photopolymerization initiator.

<Application and cross-linking of adhesive solution>
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 was performed for 4 days in an atmosphere of 25 ° C. to promote crosslinking, and a photocurable pressure-sensitive adhesive sheet was fixed and laminated on a substrate, and a reinforcing film was temporarily attached with a separator to obtain a reinforcing film.

[Evaluation]
<Composition thickness distribution>
Using a TOF-SIMS "TRIFT V nano TOF" equipped with an Arbac-GCIB gun manufactured by ULVAC-PHI, secondary ion mass spectrometry is performed while the adhesive layer is sputtered from the surface side, and the composition in the depth direction of the adhesive layer is determined. analyzed. The measurement conditions and sputtering conditions are as follows.
(Measurement condition)
Primary ion: Bi ₃ ⁺⁺
Acceleration voltage: 30 kV
Ion current: about 2 nA (as DC)
Analysis area: 100 μm × 100 μm
Analysis time: about 15 seconds / cycle Detected ions: Positive / negative ions Neutralization: Using electron gun (sputtering conditions)
Sputter ion: Ar2500 ⁺
Acceleration voltage: 20 kV
Ion current: about 8 nA
Sputter area: 400 μm × 400 μm
Sputtering time: 30 seconds / cycle

For each of the (meth) acrylic base polymer, the (meth) acrylic oligomer, and the polyfunctional compound, a depth profile was created, and the surface layer region (integral value of the secondary ion amount) of the surface layer region (1 of the total thickness from the surface) was calculated with respect to the total area (integrated value of secondary ion amount). / 3 region) was defined as the abundance ratio of the component in the surface layer region.

<Adhesive strength>
The separator was peeled off from the surface of the reinforcing film cut into a width of 25 mm and a length of 100 mm, and was bonded to the surface of a SUS304 plate using a hand roller to obtain a test sample before light curing. A test sample after photocuring was obtained by irradiating ultraviolet rays from the reinforcing film side (polyethylene terephthalate film side) of the test sample before photocuring and photocuring the adhesive layer. Using these test samples, the end portion of the polyethylene terephthalate film as the reinforcing film was held by a chuck, and the 180 ° peeling of the reinforcing film was performed at a tensile speed of 300 mm / min to measure the peel strength.

Formulation of the pressure-sensitive adhesive composition of each reinforcing sheet (type of (meth) acrylic base polymer, polyfunctional compound and (meth) acrylic oligomer), abundance ratio of polyfunctional compound and (meth) acrylic oligomer in surface layer region, Table 2 shows the measurement results of the adhesive strength before and after the light curing.

As shown in Table 2, the photocurable pressure-sensitive adhesive layers of Formulations 1 to 39 containing the (meth) acrylic base polymer, the polyfunctional compound, and the (meth) acrylic oligomer were present in the surface layer region of the polyfunctional compound. Before light curing, the adhesive strength to the adherend (SUS304 plate) was small, and good reworkability was exhibited. In addition, even if the type of the (meth) acrylic base polymer and the polyfunctional compound are the same, if the type of the (meth) acrylic oligomer is different, the amount of the (meth) acrylic oligomer in the surface layer region changes, It can be seen that the abundance of the polyfunctional compound in the surface layer also changes accordingly.

For example, in Formulations 7 to 9, the (meth) acrylic base polymer and the polyfunctional compound are the same, but the presence ratio of the (meth) acrylic oligomer in the surface layer region is 33.7% even though Formulation 7 is 33.7%. On the other hand, in the composition 8, the content was 27.2%. In Formula 8, as the abundance ratio of the (meth) acrylic oligomer in the surface region is small, the abundance ratio of the polyfunctional compound in the surface region is large, and the adhesive strength of the adhesive to the adherend after photocuring is large. Was rising.

Also in the other examples of Table 2, the smaller the abundance ratio of the (meth) acrylic oligomer in the surface layer region, the higher the abundance ratio of the polyfunctional compound in the surface layer region, and the adhesive strength tends to be significantly increased by photocuring. Was done. From these results, in the case of the photocurable pressure-sensitive adhesive composition containing the (meth) acrylic oligomer in addition to the (meth) acrylic base polymer and the polyfunctional compound, the surface layer depends on the compatibility of these three components. It can be seen that the polyfunctional compound is unevenly distributed in the vicinity, the adhesive strength after photocuring is greatly increased, and the adhesive reliability can be improved.

Claims (4)

Film base, comprising an adhesive layer fixedly laminated on one main surface of the film base,
The pressure-sensitive adhesive layer,
Photocurable composition containing a (meth) acrylic base polymer having a weight average molecular weight of 100,000 or more, a (meth) acrylic oligomer having a weight average molecular weight of 1,000 to 50,000, and a polyfunctional compound having at least two polymerizable functional groups Made of things,
Based on 100 parts by weight of the (meth) acrylic base polymer, 3 to 30 parts by weight of the (meth) acrylic oligomer and 0.5 to 30 parts by weight of the polyfunctional compound;
When the pressure-sensitive adhesive layer is divided into three equal parts in the thickness direction, and a region farthest from the substrate side is defined as a surface region,
The abundance of the polyfunctional compound in the surface region is 50% or more of the abundance of the polyfunctional compound in the entire thickness direction, and the abundance of the (meth) acrylic oligomer in the surface region is The content of the (meth) acrylic oligomer is 31% or less,
Reinforcement film. The reinforcing film according to claim 1, wherein a crosslinked structure is introduced into the (meth) acrylic base polymer. The reinforcing film according to claim 1 or 2, wherein the (meth) acrylic base polymer contains a hydroxy group-containing monomer as a monomer unit. 4. The reinforcing film according to claim 1, wherein the polyfunctional compound is a polyfunctional (meth) acrylate.

Images