JP6995033B2 - Reinforcing film - Google Patents

Description

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

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

By temporarily attaching the adhesive film to the surface of the device or device component in the state before use such as assembly, processing, and transportation of the device, it is possible to suppress damage or breakage of the adherend. Such an adhesive film is a process material and is stripped and removed prior to use of the device. As described in Patent Document 1, the adhesive film used as a process material has low adhesiveness, can be easily peeled off from the adherend, and does not leave adhesive residue on the adherend. Desired.

Patent Document 2 discloses an adhesive film that is used in a state of being attached to the surface of the device even when the device is used, in addition to assembling, processing, and transporting the device. In addition to surface protection, such an adhesive film has a function of reinforcing the device by dispersing the impact on the device, imparting rigidity to the flexible device, and the like.

When the adhesive film is attached to the adherend, improper attachment such as air bubbles or misalignment of the attachment position may occur. When a bonding failure occurs, the adhesive film is peeled off from the adherend and another adhesive film is bonded (rework). Since the adhesive film used as a process material is designed on the premise of peeling from the adherend, it is easy to rework. On the other hand, the reinforcing film is generally not expected to be peeled off from the device, and is firmly adhered to the surface of the device, so that rework is difficult.

Patent Document 3 discloses an adhesive sheet (adhesive layer) designed to have low adhesiveness immediately after being bonded to an adherend and to increase the adhesive force with time. An adhesive film in which such an adhesive layer is fixedly laminated on a film substrate can be easily peeled off from the adherend immediately after being bonded to the adherend, and after a predetermined time has passed, the adhesive film is easily peeled off from the adherend. Since it adheres firmly, it can be used as a reinforcing film having reworkability.

Japanese Unexamined Patent Publication No. 2013-185007 JP-A-2017-132977 WO2015 / 163115 Pamphlet

It cannot be said that the reinforcing film whose adhesive force with the adherend changes with time has sufficient flexibility for the lead time of the process. For example, a reinforcing film provided with an adhesive layer whose adhesive strength increases with time is inspected and reworked in a bonded state within a predetermined time after being bonded to an adherend until the adhesive strength increases. There is a need. In addition, when processing such as removing the reinforcing film from a part of the area after attaching the reinforcing film to the entire surface of the device or device component, it is necessary to perform the processing until the adhesive strength increases. be.

In view of the above, the present invention can be easily reworked immediately after being bonded to the adherend, and the time from bonding to the adherend until the adhesive strength is improved can be arbitrarily set, and adhesion is possible. It is an object of the present invention to provide a reinforcing film that can be firmly adhered to an adherend by improving the force.

The reinforcing film of the present invention includes a pressure-sensitive adhesive layer fixed and laminated on one main surface of a film base material. The pressure-sensitive adhesive layer consists 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. It is preferable that the (meth) acrylic base polymer has a crosslinked structure introduced therein. The polyfunctional compound is a compound containing two or more polymerizable functional groups, and a polyfunctional (meth) acrylate is preferable.

The photocurable composition constituting the pressure-sensitive adhesive layer contains a (meth) acrylic-based oligomer having a weight average molecular weight of 1000 to 50,000 in addition to the (meth) acrylic-based 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 with respect to 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 the surface layer region, the abundance of the polyfunctional compound in the surface layer region is the abundance of the polyfunctional compound in the entire thickness direction. It is 50% or more. The abundance of the (meth) acrylic oligomer in the surface layer 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. In addition, after the pressure-sensitive adhesive layer is photo-cured, it exhibits high adhesive strength to the adherend, which contributes to reinforcement of the device and improvement of reliability.

It is sectional drawing which shows the laminated structure of a reinforcing film. It is sectional drawing which shows the laminated structure of a reinforcing film.

FIG. 1 is a cross-sectional view showing an embodiment of a reinforcing film. The reinforcing film 10 includes an adhesive layer 2 on one main surface of the film base material 1. The pressure-sensitive adhesive layer 2 is fixedly laminated on one main surface of the base film 1. The pressure-sensitive adhesive layer 2 is a photo-curable pressure-sensitive adhesive made of a photo-curable composition, and is cured by irradiation with active light such as ultraviolet rays to increase the adhesive strength with an adherend.

FIG. 2 is a cross-sectional view of a reinforcing film in which a separator 5 is temporarily attached on the main surface of the pressure-sensitive adhesive layer 2. The reinforcing film 10 is attached to the surface of the adherend by peeling off the separator 5 from the surface of the pressure-sensitive adhesive layer 2 and adhering the exposed surface of the adhesive layer 2 to the adherend. In this state, the pressure-sensitive adhesive layer 2 is before photo-curing, and the reinforcing film 10 (adhesive layer 2) is temporarily attached to the adherend. By photocuring the pressure-sensitive adhesive layer 2, the adhesive force at the interface between the adherend and the pressure-sensitive adhesive layer 2 is increased, and the adherend and the reinforcing film 10 are fixed to each other.

"Fixing" is a state in which two laminated layers are firmly adhered to each other, and peeling at the interface between the two is impossible or difficult. "Temporary adhesion" is a state in which the adhesive force between the two laminated layers is small and can be easily peeled off at the interface between the two layers.

In the reinforcing film shown in FIG. 2, the film base material 1 and the pressure-sensitive adhesive layer 2 are fixed to each other, and the separator 5 is temporarily attached to the pressure-sensitive adhesive layer 2. When the separator 5 is peeled off, 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 base material 1, a plastic film is used. In order to fix the film base material 1 and the pressure-sensitive adhesive layer 2, it is preferable that the surface of the film base material 1 to which the pressure-sensitive adhesive layer 2 is attached is not subjected to a mold 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, cushioning the impact, etc., the thickness of the film substrate 1 is preferably 20 μm or more, more preferably 30 μm or more, still more preferably 45 μm or more. From the viewpoint of giving flexibility to the reinforcing film and improving handleability, the thickness of the film base material 1 is preferably 300 μm or less, more preferably 200 μm or less.

Examples of the plastic material constituting the film base material 1 include polyester-based resin, polyolefin-based resin, polyamide-based resin, and polyimide-based resin. In the reinforcing film for an optical device such as a display, the film base material 1 is preferably a transparent film. Further, when the pressure-sensitive adhesive layer 2 is photo-cured by irradiating the film base material 1 with active light rays, it is preferable that the film base material 1 has transparency to the active light rays used for curing the pressure-sensitive adhesive layer. .. Polyester-based 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 base material 1, a reinforcing film can be obtained. The pressure-sensitive adhesive layer 2 may be formed directly on the film base material 1, or the pressure-sensitive adhesive layer formed in a sheet shape on another base material may be transferred onto the film base material 1.

The pressure-sensitive adhesive layer 2 is made of a photocurable composition. The adhesive layer 2 has a small adhesive force with an adherend such as a device or a device component before photo-curing, so that it can be easily reworked. Since the adhesive layer 2 is photocured to improve the adhesive force with the adherend, the reinforcing film is difficult to peel off from the device surface even when the device is used, and the adhesive reliability is excellent.

The thickness of the pressure-sensitive adhesive layer 2 is, for example, about 1 to 300 μm. The larger the thickness of the pressure-sensitive adhesive layer 2, the better the adhesiveness with the adherend tends to be. On the other hand, if 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, further 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, still more 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.

The pressure-sensitive adhesive composition (photocurable composition) constituting the pressure-sensitive adhesive layer 2 contains a (meth) acrylic-based base polymer, a (meth) acrylic-based oligomer, and a polyfunctional compound. From the viewpoint of increasing the efficiency of curing by irradiation with active light, 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 constituent of the pressure-sensitive adhesive composition and is a main factor that determines the adhesive strength of the pressure-sensitive adhesive. When the reinforcing film is peeled off from the adherend before the pressure-sensitive adhesive layer 2 is photohardened, the (meth) acrylic base polymer has a crosslinked structure from the viewpoint of facilitating the peeling and preventing adhesive residue on the adherend. It is preferable that it has been introduced.

The polyfunctional compound has two or more polymerizable functional groups in one molecule. The polyfunctional compound has an action of increasing the cohesiveness of the pressure-sensitive adhesive after photo-curing and improving the adhesive force with the adherend. Further, since the abundance of the polyfunctional compound in the surface layer region 2a of the pressure-sensitive adhesive layer 2 before photo-curing is larger than the abundance of the polyfunctional compound in the other regions 2b and 2c in the thickness direction, the adhesion before photo-curing The adhesive force between the agent 2 and the adherend is moderately reduced, and the peelability of the reinforcing sheet from the adherend tends to be improved.

The (meth) acrylic oligomer has an effect of adjusting the adhesive force of the pressure-sensitive adhesive before and after photo-curing by giving a distribution to the composition of the pressure-sensitive adhesive layer 2 before photo-curing in the thickness direction. In particular, when the abundance of the (meth) acrylic oligomer in the surface layer region 2a of the pressure-sensitive adhesive layer 2 before photo-curing is smaller than the abundance of the (meth) acrylic oligomer in the middle layer region 2b and the substrate side region 2c. The adhesive strength before photo-curing is small and the peelability is excellent, and the adhesive strength is significantly increased by photo-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 the 1/3 region on the surface layer side (the region farthest from the film substrate 1) is the "surface layer region" and the central 1/3 region in the thickness direction. Is referred to as a “middle layer region”, and a region of 1/3 of the film substrate 1 side is referred to as a “base material side region”.

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 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 ratio, the abundance ratio in the middle layer region 2b, and the abundance ratio in the base material side region 2c have a distribution. When the pressure-sensitive adhesive layer does not have a 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 substrate 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 layer region 2a is 50% or more, and the abundance ratio of the (meth) acrylic oligomer in the surface layer region 2a is 31. % Or less. In the present specification, the "presence ratio of the polyfunctional compound in the surface layer region" means the abundance ratio of the polyfunctional compound in the surface layer region to 100% of the total amount of the polyfunctional compound contained in the pressure-sensitive adhesive layer, and "(meth). The "absence ratio of the acrylic oligomer in the surface layer region" means the abundance 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 abundance 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 layer region 2a is generally 15% or more, preferably 20% or more, more preferably 23% or more, and 25% or more from the viewpoint of enhancing the transparency of the pressure-sensitive adhesive. More preferred.

The abundance ratio of the polyfunctional compound in the surface layer 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, preferably 93% or less, more preferably 90% or less, from the viewpoint of enhancing the adhesive force of the pressure-sensitive adhesive layer 2 to the adherend after photocuring. It is preferably 87% or less, more preferably 87% or less.

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

Hereinafter, preferred forms of each component constituting the pressure-sensitive adhesive composition will be described in order.

<(Meta) acrylic base polymer>
The (meth) acrylic base polymer is a polymer containing a (meth) acrylic acid alkyl ester as a main monomer component and having a weight average molecular weight of 100,000 or more. In addition, in this specification, "(meth) acrylic" means acrylic and / or methacrylic.

As the (meth) acrylic acid alkyl ester, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferably used. The alkyl group of the (meth) acrylic acid alkyl ester may be linear or may have branches. Examples of (meth) acrylic acid alkyl esters are methyl (meth) acrylic acid, ethyl (meth) acrylic acid, butyl (meth) acrylic acid, isobutyl (meth) acrylic acid, s-butyl (meth) acrylic acid, ( T-butyl acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-> acrylate (meth) acrylate Ethylhexyl, (meth) octyl acrylate, (meth) isooctyl acrylate, (meth) nonyl acrylate, (meth) isononyl acrylate, (meth) decyl acrylate, (meth) isodecyl acrylate, undecyl (meth) acrylate , (Meta) dodecyl acrylate, (meth) isotridecyl acrylate, (meth) tetradecyl acrylate, (meth) isotetradecyl acrylate, (meth) pentadecyl acrylate, (meth) cetyl acrylate, (meth) Examples thereof include heptadecyl acrylate, octadecyl (meth) acrylate, iso-octadecyl (meth) acrylate, nonadecil (meth) acrylate, and aralkyl (meth) acrylate.

The content of the (meth) acrylic acid alkyl ester is preferably 40% by weight or more, more preferably 50% by weight or more, still more preferably 55% by weight or more, 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. Above all, it is preferable to contain a hydroxy group-containing monomer as a copolymerization component of the (meth) acrylic base polymer. The hydroxy group and carboxy group of the (meth) acrylic base polymer serve as reaction points with the cross-linking 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 lowered. There is a tendency to reduce the amount of adhesive residue on the body.

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). Examples thereof include 8-hydroxyoctyl acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 4- (hydroxymethyl) cyclohexylmethyl (meth) acrylate and the like. Examples of the carboxy group-containing monomer include (meth) acrylic acid, 2-carboxyethyl ( meth) acrylic acid, carboxypentyl (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like.

In addition to the above, the (meth) acrylic base polymer may use an acid anhydride group-containing monomer, an acrylic acid caprolactone adduct, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, or the like as a copolymerization monomer component. Further, as the modifying monomer, vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazin, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholin, N. -Vinyl carboxylic acid amides, vinyl-based monomers such as styrene, α-methylstyrene, N-vinylcaprolactam; cyanoacrylate-based monomers such as acrylonitrile and methacrylonitrile; (meth) acrylamide, N, N-dimethyl (meth) acrylamide. , N, N-diethylacrylamide, N-isopropyl (meth) acrylamide and other (meth) acrylamide-based monomers; (meth) glycidyl acrylate and other epoxy group-containing acrylic monomers; (meth) acrylate polyethylene glycol, (meth) Glycol-based acrylic ester monomers such as polypropylene glycol acrylate, methoxyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate; (meth) tetrahydrofurfuryl acrylate, fluorine-containing (meth) acrylate, silicone (meth) (Meta) acrylic acid ester-based monomers such as acrylate and 2-methoxyethyl acrylate can also be used.

The ratio of the copolymerization monomer component in the (meth) acrylic base polymer is not particularly limited, but when a hydroxy group-containing monomer or a carboxy group-containing monomer is used as the copolymerization monomer component for the purpose of introducing a cross-linking point, for example, The total content of the droxy group-containing 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. preferable.

A (meth) acrylic base polymer can be obtained by polymerizing the above-mentioned monomer components by various known methods such as solution polymerization, emulsion polymerization and bulk polymerization. The solution polymerization method is preferable from the viewpoint of the balance of characteristics such as the adhesive force and the holding force of the pressure-sensitive adhesive and the cost. Ethyl acetate, toluene and the like are used as the solvent for solution polymerization. The solution concentration is usually about 20 to 80% by weight. As the polymerization initiator, various known agents such as azo type and peroxide type can be used. Chain transfer agents may be used to adjust the molecular weight. The reaction temperature is usually 50 to 80 ° C., and the reaction time is usually 1 to 8 hours.

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 viewpoint of processability, transparency, and the like of the pressure-sensitive adhesive layer 2, the weight average molecular weight of the (meth) acrylic base polymer is preferably 2 million or less. The weight average molecular weight of the (meth) acrylic base polymer is preferably 200,000 to 1,500,000, more preferably 400,000 to 1,200,000. The weight average molecular weight is a polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC). When the 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 in the above range.

In order to obtain the pressure-sensitive adhesive layer 2 having appropriate adhesiveness to the adherend in a normal temperature environment, the glass transition temperature (Tg) of the (meth) acrylic base polymer in terms of 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 even more preferably −70 to −20 ° C.

<Crosslinking agent>
From the viewpoint of giving the pressure-sensitive adhesive an appropriate cohesive force, it is preferable to introduce a crosslinked structure into the (meth) acrylic base polymer. For example, a cross-linked structure is introduced by adding a cross-linking agent to the solution after polymerizing the (meth) acrylic base polymer and heating as necessary. Examples of the cross-linking agent include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, carbodiimide-based cross-linking agents, metal chelate-based cross-linking agents and the like. These cross-linking agents react with functional groups such as hydroxy groups introduced into the (meth) acrylic base polymer to form a cross-linked structure.

Since a crosslinked structure can be introduced into the (meth) acrylic base polymer by heating, polyisocyanate having two or more isocyanate groups in one molecule is preferable as the crosslinked agent. Examples of the polyisocyanate-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; 2,4-triisocyanate. Aromatic isocyanates such as range isocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; trimethylol propane / tolylene diisocyanate trimer adduct (eg, "Coronate L" manufactured by Toso), trimethylol propane / hexa Methylene diisocyanate trimeric adduct (eg, "Coronate HL" manufactured by Tosoh), trimethylol propane adduct of xylylene diisocyanate (eg, "Takenate D110N" manufactured by Mitsui Chemicals, isocyanurate of hexamethylene diisocyanate (eg, manufactured by Tosoh). Examples thereof include isocyanate additives such as "Coronate HX" and "Y-75" manufactured by Soken Kagaku.

The amount of the cross-linking agent used may be appropriately adjusted according to the composition, molecular weight, etc. of the (meth) acrylic base polymer. The amount of the cross-linking agent used is 0.1 to 10 parts by weight, preferably 0.2 to 7 parts by weight, and more preferably 0.3 to 5 parts by weight with respect to 100 parts by weight of the (meth) acrylic base polymer. Parts, more preferably 1 to 4 parts by weight.

A cross-linking catalyst may be used to promote the formation of the cross-linked structure. Examples of the cross-linking catalyst include tetra-n-butyl titanate, tetraisopropyl titanate, ferric nasem, butyl tin oxide, dibutyl tin acetate, dibutyl tin dilaurylate, dioctyl tin diacetate, dioctyl tin distearate, and dioctyl tin dilaurate. Examples thereof include metal-based cross-linking catalysts (particularly tin-based cross-linking catalysts). The amount of the cross-linking catalyst used is generally 0.05 parts by weight or less with respect to 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 it has a high affinity with the (meth) acrylic base polymer, it is preferable to use a polyfunctional (meth) acrylate as the polyfunctional compound. Examples of the polyfunctional (meth) acrylate 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. , Tricyclodecane dimethanol di (meth) acrylate and other diols and (meth) acrylic acid esters; pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropanthry (meth) acrylate, ditri Polycarbonate propanetetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol poly (meth) acrylate, dipentaerythritol hexa (meth) acrylate and other polyols having three or more hydroxy groups and (meth) acrylic acid Esters; Compounds having a (meth) acryloyl group such as urethane (meth) acrylate, epoxy (meth) acrylate, butadiene (meth) acrylate, isoprene (meth) acrylate and a polymerizable functional group other than the (meth) acryloyl group, etc. Can be mentioned.

As the polyfunctional compound, an ester of a modified polyol of a polyol with an alkylene oxide such as methylene oxide, ethylene oxide, or propylene oxide and an (meth) acryloyl group may be used. Examples of the ester of the alkylene oxide-modified form 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 (that is, the number of functional groups per unit molecular weight is small) and changes the polarity of the molecule. Further, 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, in the thickness direction of the pressure-sensitive adhesive layer before photo-curing. The composition distribution of the polymer and the adhesiveness of the pressure-sensitive adhesive after photo-curing may change.

From the viewpoint of enhancing the adhesive force after photo-curing, 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, still more preferably 150 or more. 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 strength of the pressure-sensitive adhesive layer 2 before photocuring is increased, so that the adherend can be removed from the adherend. 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 photo-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 100 to 1000.

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 2 to 15 parts by weight with respect to 100 parts by weight of the (meth) acrylic base polymer. The portion is more preferable. By containing 0.5 part by weight or more of the polyfunctional compound, the polyfunctional compound is likely to be unevenly distributed on the surface layer portion 2a in the pressure-sensitive adhesive layer 2 before photo-curing, and accordingly, the adhesive force with the adherend is appropriate. Tends to decrease. On the other hand, when the content of the polyfunctional compound in the pressure-sensitive adhesive composition becomes excessively large, sufficient adhesive strength can be obtained due to a decrease in transparency due to bleed-out of the polyfunctional compound and a decrease in viscosity of the pressure-sensitive adhesive after photo-curing. May not be. In order to include the polyfunctional compound in the composition in an uncured state, it is preferable to add the polyfunctional compound after polymerizing the (meth) acrylic base polymer.

<(Meta) acrylic oligomer>
The pressure-sensitive adhesive layer 2 contains a (meth) acrylic oligomer. The (meth) acrylic oligomer acts as a tackifier and can contribute to the improvement of the adhesive force of the pressure-sensitive adhesive to the adherend after photo-curing. Further, 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 of the pressure-sensitive adhesive layer 2 has a distribution in the thickness direction and is photo-cured. It has the effect of adjusting the adhesive strength of the front and rear adhesives.

The (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-mentioned (meth) acrylic base polymer. The weight average molecular weight of the (meth) acrylic oligomer is 1000 to 50,000. The weight average molecular weight of the (meth) acrylic oligomer is 30,000 or less from the viewpoint of maintaining the transparency of the pressure-sensitive adhesive layer 2 by having an appropriate affinity with the above (meth) acrylic base polymer and the polyfunctional compound. It is preferable, 10,000 or less is more preferable, and 8000 or less is further preferable.

The (meth) acrylic oligomer contains a (meth) acrylic acid alkyl ester as a main monomer component. The content of the (meth) acrylic acid alkyl ester is 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and more preferably 80% by weight, based on the total amount of the monomer components constituting the (meth) acrylic oligomer. More preferably by weight% or more. In a preferred embodiment, the (meth) acrylic oligomer contains substantially only the (meth) acrylic acid alkyl ester as the monomer component. The (meth) acrylic oligomer may contain two or more kinds of monomer components.

The monomer component constituting the (meth) acrylic oligomer preferably does not form a cross-linking structure with the above-mentioned cross-linking 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 has, 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 ester can be mentioned. In addition, (meth) acrylic acid esters having an alicyclic group such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate; benzyl (meth) acrylate, 2-naphthyl (meth) acrylate. (Meta) acrylic acid ester having an aromatic ring or heterocyclic ring-containing group such as pentamethylpiperidin (meth) crylate, 2-phenoxyethyl (meth) acrylate; methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, di. Monomer components such as cyclopentenyloxyethyl (meth) acrylate and tetrahydrofurfuryl methacrylate are also suitable as monomer components constituting (meth) acrylic oligomers.

<Light initiator>
The pressure-sensitive adhesive layer 2 preferably contains a photoinitiator. The photoinitiator generates active species by irradiation with active light rays and promotes the curing reaction of the polyfunctional compound. As the photoinitiator, a photocation initiator (photoacid generator), a photoradical initiator, a photoanion initiator (photobase generator) and the like are used depending on the type of the polyfunctional compound and the like. When a polyfunctional acrylate is used as the polyfunctional compound, it is preferable to use a photoradical initiator. Examples of the photoradical initiator include hydroxyketones, benzyldimethylketals, aminoketones, acylphosphine oxides, benzophenones, trichloromethyl group-containing triazine derivatives and the like. 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 amount of the pressure-sensitive adhesive layer 2.

<Other additives>
In addition to the above-exemplified components, the pressure-sensitive adhesive composition includes a silane coupling agent, a tackifier, a plasticizer, a softening agent, a deterioration inhibitor, a filler, a colorant, an ultraviolet absorber, an antioxidant, and a surfactant. , Antistatic agents and other additives may be contained within a range that does not impair the characteristics of the present invention.

<Formation of adhesive layer>
The above pressure-sensitive adhesive composition containing a (meth) acrylic base polymer, a polyfunctional compound and a (meth) acrylic oligomer can be applied to a roll coat, a kiss roll coat, a gravure coat, a reverse coat, a roll brush, a spray coat, and a dip roll coat. , Bar coat, knife coat, air knife coat, curtain coat, lip coat, die coat, etc. are applied on the substrate, and if necessary, the solvent is dried and removed to form an adhesive layer. As a drying method, an appropriate method can be appropriately adopted. 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.

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

By introducing a crosslinked structure into the (meth) acrylic base polymer, the gel fraction of the pressure-sensitive adhesive layer 2 tends to increase. The higher the gel fraction of the pressure-sensitive adhesive layer 2, the harder the pressure-sensitive adhesive, and the more the adhesive remains on the adherend 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 photo-curing is preferably 20% or more, more preferably 30% or more, still more preferably 40% or more. If the gel fraction of the pressure-sensitive adhesive layer 2 before photo-curing is excessively large, the anchoring force with respect to the adherend may decrease, and the adhesive force may be insufficient. Therefore, the gel fraction of the pressure-sensitive adhesive layer 2 before photo-curing 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 insoluble component after the pressure-sensitive adhesive layer is immersed in ethyl acetate at 23 ° C. for 7 days with respect to the sample before immersion. Obtained as a weight fraction (unit: weight%). In general, the gel fraction of a polymer is equal to the degree of cross-linking, and the more cross-linked portions in the polymer, the higher the gel fraction.

Even after the cross-linked structure is introduced into the (meth) acrylic base polymer by the cross-linking agent, the polyfunctional compound remains in an unreacted state. When a (meth) acrylic oligomer having no reactive functional group with a cross-linking agent is used, the (meth) acrylic oligomer does not form a chemical bond with the (meth) acrylic base polymer. , Present 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 attach the separator 5 on the pressure-sensitive adhesive layer 2 for the purpose of protecting the pressure-sensitive adhesive layer 2. Crosslinking may be performed after attaching the separator 5 on the pressure-sensitive adhesive layer 2. When the pressure-sensitive adhesive layer 2 is formed on another base material, a reinforcing film can be obtained by transferring the pressure-sensitive adhesive layer 2 onto the film base material 1 after drying the solvent. The base material used for forming the pressure-sensitive adhesive layer may be used as it is as the separator 5.

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

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

Since 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 adhesion interface with the adherend, and the pressure-sensitive adhesive layer 2 before photocuring is used as a bulk. It is considered that the adhesive force to the adherend is small because the liquid property is strong at the adhesive interface while maintaining the hardness of. Further, since the polyfunctional compound is unevenly distributed in the surface layer region 2a, which is the adhesion interface with the adherend, it is considered that the increase in the cohesive force of the adherend interface with photocuring becomes remarkable. By increasing the cohesive force at the interface of the adherend of the pressure-sensitive adhesive layer after photocuring, the adhesive force with the adherend is significantly increased, and the adhesive reliability of the reinforcing film is enhanced.

It is considered that the 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 influenced by the structure of the compound. The structure and compatibility of the compound can be evaluated, for example, by the Hansen solubility parameter.

The Hansen solubility parameter (HSP) is a three-dimensional space obtained by dividing the solubility parameter δ of Hildebrand into three components, the dispersion term δ _d , the polarity term δ _p , and the hydrogen bond term δ _h . There is a relationship of δ ² = δ _d ² + δ _p ² + δ _h ² . The dispersion term δ _d indicates the effect due to the dispersion force, the polar term δ _p indicates the effect due to the dipole interpole force, and the hydrogen bond term δ _h indicates the effect due to the hydrogen bond force. The distance Ra of the HSPs of the two substances is Ra = {4Δδ _d ² + Δδ _p ² + Δδ _h from the difference Δδ _d of the dispersion term between the two substances, the difference Δδ _p of the polar term, and the difference Δδ _h of the hydrogen bond term. ² } It is represented by ^1/2 , and the smaller Ra, the higher the compatibility, and the larger Ra, the lower the compatibility.

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

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 layer region of the (meth) acrylic oligomer due to the uneven distribution of the polyfunctional compound in the surface layer region. The abundance ratio becomes smaller. Therefore, by using a (meth) acrylic oligomer having an appropriately large distance of HSP from the polyfunctional compound, the abundance ratio of the (meth) acrylic oligomer in the surface layer region is relatively small (for example, 31% or less). It is considered that the agent layer 2 can be formed. Further, 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 which influences the abundance of the (meth) acrylic oligomer in the surface layer region.

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

[Attachment of reinforcing sheet to adherend and photo-curing]
The reinforcing film of the present invention is used by being bonded to a constituent member (work in process) of various devices or a device after completion. When the reinforcing film is attached to the work-in-process in the manufacturing process of the device, the reinforcing film may be attached to the large-sized work-in-process before being cut to the product size. The reinforcing film may be attached to the mother roll of the device manufactured by the roll-to-roll process by roll-to-roll. The reinforcing film may be attached to the entire surface of the adherend, or may be selectively attached only to the portion requiring reinforcement. Further, after the reinforcing film is attached to the entire surface of the adherend, the reinforcing film at a portion that does not require reinforcement may be cut and the reinforcing film may be peeled off and removed.

Before the adhesive is photo-cured, the adhesive force between the 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 applied from the surface of the adherend. It can be peeled off and has excellent reworkability. As described above, the polyfunctional compound is unevenly distributed in the surface layer region of the pressure-sensitive adhesive layer 2, so that the adhesiveness before photo-curing tends to be reduced.

From the viewpoint of facilitating peeling from the adherend and preventing adhesive residue on the adherend after peeling the reinforcing film, the adhesive strength between the adhesive layer 2 before photo-curing and the adherend is 1 N / 25 mm. The following is preferable, 0.8 N / 25 mm or less is more preferable, and 0.6 N / 25 mm or less is further preferable. On the other hand, from the viewpoint of preventing the reinforcing sheet from peeling off from the adherend during storage and handling, the adhesive strength between the pressure-sensitive adhesive layer 2 and the adherend before photo-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 further preferable, and 0.1 N / 25 mm or more is particularly preferable. The adhesive strength can be evaluated by a 180 ° peel test with a tensile speed of 300 mm / min using a SUS304 plate as an adherend.

After the reinforcing film is attached to the adherend, the pressure-sensitive adhesive layer 2 is photo-cured by irradiating the pressure-sensitive adhesive layer 2 with active light rays. Examples of the active light beam include ultraviolet rays, visible light, infrared rays, X-rays, α-rays, β-rays, and γ-rays. Ultraviolet rays are preferable as the active light rays because the curing of the pressure-sensitive adhesive layer in the stored state can be suppressed and the curing is easy. The irradiation intensity and irradiation time of the active light may be appropriately set according to the composition and thickness of the pressure-sensitive adhesive layer.

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

As described above, in the pressure-sensitive adhesive layer 2 before photo-curing, when the abundance ratio of the (meth) acrylic oligomer in the surface layer region is small, the adhesive strength tends to be significantly increased by photo-curing. Even when the pressure-sensitive adhesive layer 2 before photo-curing has a composition distribution in the thickness direction, the abundance ratio of the (meth) acrylic oligomer in the pressure-sensitive adhesive layer after photo-curing is almost uniform in the thickness direction. Often becomes. From these facts, the movement of the (meth) acrylic oligomer that was present in the substrate side region and the middle layer region before photo-curing to the surface layer region with photo-curing is related to the improvement of adhesive strength. It is presumed that it is.

As the polymerization of the polyfunctional compound progresses due to photocuring, the liquid properties of the polyfunctional compound unevenly distributed in the surface layer region weaken, WBL disappears, and the phase between the (meth) acrylic base polymer and the polyfunctional compound. Highly soluble. Along with this, 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. .. In this way, as the photocuring progresses, 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 layer region increases. .. As described above, when the pressure-sensitive adhesive layer is photo-cured, the cohesive force associated with the polymerization of the polyfunctional compound which was unevenly distributed before the photo-curing increases in the surface layer region. In addition to this, it is considered that a high concentration of the (meth) acrylic oligomer acting as a tackifier in the surface layer region also contributes to the improvement of the adhesive strength of the pressure-sensitive adhesive layer after photo-curing to the adherend.

By laminating the reinforcing film, rigidity can be imparted to the adherend, so that bending, curling, bending, etc. due to stress, its own weight, etc. are suppressed, and handleability is improved. Therefore, by attaching a reinforcing film to the work-in-process in the device manufacturing process, it is possible to prevent defects and defects during transportation and processing. In addition, when using the device after completion, even if an external force is unexpectedly applied due to the device falling, placing a heavy object on the device, collision of a flying object with the device, etc., the reinforcing film is attached. By doing so, it is possible to prevent damage to the device. Since the reinforcing film after photo-curing the adhesive is firmly adhered to the device, the reinforcing film does not easily come off even after long-term use, and the reliability is excellent.

In the reinforcing film of the present invention, the pressure-sensitive adhesive layer 2 is photocurable, and the timing of curing can be arbitrarily set. Processing such as reworking and processing of the reinforcing film can be performed at any time between the time when the reinforcing film is attached to the adherend and the time when the adhesive is photo-cured, so that it can be used as a lead time in the device manufacturing process. Can be flexibly handled.

The present invention will be further described below with reference to examples of producing a reinforcing film provided with various formulations of the pressure-sensitive adhesive composition, but the present invention is not limited to the following specific examples.

[Manufacturing of (meth) acrylic base polymer]
<Base Polymer A>
In a reaction vessel equipped with a thermometer, agitator, a reflux cooling tube 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 as monomers. 0.1 part by weight of acid (AA), 0.2 part by weight of azobisisobutyronitrile as a polymerization initiator, and 200 parts by weight of ethyl acetate as a solvent were added, nitrogen gas was flowed, and nitrogen was stirred for about 1 hour with stirring. Substitution was performed. Then, it heated to 70 degreeC and reacted for 6 hours, and obtained the solution of the base polymer A. The weight average molecular weight of the base polymer A was 494,000.

<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 monomer charged 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) of the polymer, the weight average molecular weight (Mw), and the molecular weight distribution (Mw / Mn). 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 (Homopolymer Tg: -55 ° C)
AM: Acrylamide (homopolymer Tg: 165 ° C)
AA: Acrylic acid (Tg of homopolymer: 106 ° C)

The Tg of the (meth) acrylic base polymer was calculated by the Fox formula from the Tg of the homopolymer of each monomer component and the compounding ratio of the monomer. The Mw (polystyrene equivalent) of the (meth) acrylic base polymer was measured using GPC (“HLC-8220GPC” manufactured by Tosoh) under the following conditions.
Sample concentration: 0.2% by weight (tetrahydrofuran solution)
Sample injection volume: 10 μL
Eluent: THF
Flow velocity: 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

[Making a 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 a polyfunctional compound are added to 100 parts by weight of the solid content of the (meth) acrylic base polymer. 10 parts by weight, 2 parts by weight of the cross-linking agent, and 0.1 part by weight of the photopolymerization initiator were added in a solid content ratio, mixed uniformly, and the pressure-sensitive adhesive compositions of Formulations 1 to 39 shown in Table 2 were added. Was prepared. A trimethylolpropane adduct of xylylene diisocyanate (75% ethyl acetate solution, "Takenate D110N" manufactured by Mitsui Chemicals, Inc.) was used as the thermal cross-linking agent, and 1-hydroxycyclohexylphenylketone (manufactured by BASF) was used as the photopolymerization initiator. "Irgacure 184") was used.

As the (meth) acrylic oligomer, a polymer of tetrahydrofurfuryl methacrylate (THMMA), 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. board. TMP (EO) ₃ TA has an average of 1 ethylene oxide inserted between methylol and acryloyl (average of 3 in one molecule), and TMP (EO) ₆ TA has an average of 1 between methylol and acryloyl. Two ethylene oxides (6 on average in one molecule) are inserted.

In Formulations 40 and 41, a pressure-sensitive adhesive composition was prepared without using a (meth) acrylic oligomer. In Formulations 42-44, pressure-sensitive adhesive compositions were prepared without the use of polyfunctional compounds and photopolymerization initiators.

<Applying and cross-linking adhesive solution>
The above pressure-sensitive adhesive composition was applied onto a polyethylene terephthalate film (“Lumilar S10” manufactured by Toray Industries, Inc.) having a thickness of 75 μm without surface treatment using a fountain roll 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 polyethylene terephthalate film having a thickness of 25 μm with a silicone release-treated surface) was attached to the coated surface of the adhesive. Then, an aging treatment was carried out in an atmosphere of 25 ° C. for 4 days to allow cross-linking to proceed, a photocurable pressure-sensitive adhesive sheet was fixedly laminated on the substrate, and a separator was temporarily adhered onto the reinforcing film to obtain a reinforcing film.

[evaluation]
<Thickness distribution of composition>
Using the TOF-SIMS "TRIFT V nano TOF" equipped with ULVAC-PHI's Ar-GCIB gun, secondary ion mass spectrometry was performed while sputtering the pressure-sensitive adhesive layer from the surface side to determine the composition of the pressure-sensitive adhesive layer in the depth direction. analyzed. The measurement conditions and spatter conditions are as follows.
(Measurement condition)
Primary ion: Bi ₃ ⁺⁺
Acceleration voltage: 30kV
Ion current: Approximately 2nA (as DC)
Analytical area: 100 μm × 100 μm
Analysis time: Approximately 15 seconds / cycle Detection ion: Positive / negative ion Neutralization: Use electron gun (spatter condition)
Spatter ion: Ar2500 ⁺
Acceleration voltage: 20kV
Ion current: Approximately 8nA
Spatter area: 400 μm × 400 μm
Spatter time: 30 seconds / cycle

Depth profiles were created for each of the (meth) acrylic base polymer, (meth) acrylic oligomer, and polyfunctional compound, and the surface area (1 of the total thickness from the surface) with respect to the total area (integral value of the amount of secondary ions). The area ratio of (3/3 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 out to a width of 25 mm and a length of 100 mm, and bonded to the surface of the SUS304 plate using a hand roller to prepare a test sample before photo-curing. A test sample after photo-curing was obtained by irradiating ultraviolet rays from the reinforcing film side (polyethylene terephthalate film side) of the test sample before photo-curing to photo-curing the adhesive layer. Using these test samples, the end of the polyethylene terephthalate film of the reinforcing film was held by a chuck, the reinforcing film was peeled 180 ° at a tensile speed of 300 mm / min, and the peel strength was measured.

Formulation of the pressure-sensitive adhesive composition of each reinforcing sheet (types of (meth) acrylic base polymer, polyfunctional compound and (meth) acrylic oligomer), abundance ratio of polyfunctional compound and (meth) acrylic oligomer in the surface layer region, Table 2 shows the measurement results of the adhesive strength before and after photo-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 have the abundance ratio of the polyfunctional compound in the surface layer region. The adhesive strength with the adherend (SUS304 plate) was small before photo-curing, and good reworkability was shown. Further, even if the types of the (meth) acrylic base polymer and the polyfunctional compound are the same, if the types of the (meth) acrylic oligomers are different, the abundance of the (meth) acrylic oligomers in the surface layer region changes. It can be seen that the abundance of the polyfunctional compound in the surface layer region also changes accordingly.

For example, in formulations 7 to 9, the (meth) acrylic base polymer and the polyfunctional compound are the same, but the abundance ratio of the (meth) acrylic oligomer in the surface layer region is 33.7% in formulation 7. On the other hand, it was 27.2% in the formulation 8. In Formulation 8, the abundance ratio of the (meth) acrylic oligomer in the surface layer region is small, so that the abundance ratio of the polyfunctional compound in the surface layer region is large, and the adhesive force to the adherend after photo-curing the adhesive is large. Was rising to.

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 a photocurable pressure-sensitive adhesive composition containing a (meth) acrylic base polymer and a polyfunctional compound in addition to a (meth) acrylic oligomer, 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 photo-curing is significantly increased, and the adhesive reliability can be improved.

Claims (4)

A film base material and an adhesive layer fixed and laminated on one main surface of the film base material are provided.
The pressure-sensitive adhesive layer is
Photocurable 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 1000 to 50,000, and a polyfunctional compound having two or more photopolymerizable functional groups. Consists of the composition
With respect to 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 were contained.
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 used as the surface layer region,
The abundance of the polyfunctional compound in the surface layer 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 layer region is the entire thickness direction. 31% or less of the abundance of the (meth) acrylic oligomer.
Reinforcing 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. The reinforcing film according to any one of claims 1 to 3, wherein the polyfunctional compound is a polyfunctional (meth) acrylate.

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