TW202323040A - Reinforcing film, method for producing and method for reinforcing device - Google Patents

Abstract

The reinforcing film (10) is equipped with a film base material and an adhesive layer (2) fixedly laminated on one principal surface of the film base material. The adhesive layer is composed of a photocurable composition. The photocurable composition that constitutes the adhesive layer includes an acrylic base polymer, a photocuring agent, and a photopolymerization initiator. The photocurable composition may also include an acrylic oligomer having a weight average molecular weight less than that of the acrylic base polymer. At least one of the acrylic base polymer and acrylic oligomer includes a monomer unit having an alicyclic structure.

Description

Reinforcement film, manufacturing method of device, and reinforcement method

The present invention relates to a reinforcing film formed by adhering and laminating a film substrate and a photocurable adhesive layer. Furthermore, the present invention relates to a method of manufacturing a device with a reinforcing film bonded to its surface, and a reinforcing method of adhering a laminated reinforcing film to the surface of an adherend.

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

In the state before the device is assembled, processed, transported, etc., damage or breakage of the adherend can be suppressed by temporarily adhering the adhesive film to the surface of the device or device component parts. Patent Document 1 discloses a reinforcing film provided with an adhesive layer containing a photocurable adhesive composition on a film substrate.

The adhesive of the reinforcing film is easy to peel off from the adherend since it has low adhesiveness immediately after being attached to the adherend. Therefore, secondary processing from the adherend can be performed, and the reinforcing film can also be selectively peeled and removed from the portion of the adherend that does not need reinforcement. The adhesive of the reinforcement film is firmly bonded to the adherend by photohardening, so the film substrate is permanently attached to the surface of the adherend, and can be used as a reinforcing material responsible for surface protection of the device. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2020-41113

[Problem to be solved by the invention]

In recent years, flexible displays using film substrates have been put into practical use, and further impact resistance is required for reinforcing films.

In view of the above, the object of the present invention is to provide a reinforcing film that can be easily peeled off immediately after bonding with the adherend, and can be firmly bonded to the adherend by photohardening the adhesive after bonding with the adherend. ground, and excellent impact resistance. [Technical means to solve the problem]

In view of the above-mentioned problems, the inventors of the present invention conducted research and found that the impact resistance to an adherend was improved by using a photocurable adhesive having a specific composition.

The reinforcing film of the present invention has an adhesive layer fixedly laminated on one main surface of the film substrate. The adhesive layer contains a photocurable composition containing a base polymer as a high molecular weight component (polymer), a photocuring agent, and a photopolymerization initiator. As the base polymer, an acrylic polymer is used. The photocurable composition constituting the adhesive layer may contain an acrylic oligomer having a weight average molecular weight smaller than that of the base polymer as a high molecular weight component.

At least one of the acrylic base polymer and the acrylic oligomer as the high molecular weight component contains a monomer unit having an alicyclic structure. The glass transition temperature of the homopolymer of monomer units having an alicyclic structure may be 150° C. or lower.

After temporarily adhering the reinforcing film to the surface of the adherend, the adhesive layer is irradiated with active light to light-cure the adhesive layer, thereby increasing the adhesive force between the reinforcing film and the adherend, and obtaining the adhesive on the surface of the adherend. Fixed laminated devices with reinforced membranes. When the adherend is a polyimide film, the adhesive force between the adhesive layer and the polyimide film is preferably 1 N/25 mm or less before the adhesive layer is light-hardened (temporary adhesive state). . The adhesive force with the polyimide film after photocuring the adhesive layer is preferably more than 30 times that before photocuring the adhesive layer. [Effect of Invention]

The adhesive layer of the reinforcing film of the present invention contains a photocurable composition, and before the adhesive layer is photocured, the adhesive force with the adherend is small, so it is easy to peel off from the adherend. By photocuring the adhesive layer after bonding with the adherend, the adhesive force with the adherend is increased. By attaching a reinforcing film, excellent impact resistance is imparted to the adherend, so damage to the adherend due to external impact, etc., can be prevented.

Fig. 1 is a cross-sectional view showing an embodiment of a reinforcing film. The reinforcement film 10 has an adhesive layer 2 on one main surface of the film substrate 1 . The adhesive layer 2 is fixedly laminated on one main surface of the film substrate 1 . The adhesive layer 2 is a photocurable adhesive containing a photocurable composition, and is cured by irradiation with active light rays such as ultraviolet rays, thereby increasing the adhesive force with the adherend.

FIG. 2 is a cross-sectional view of a reinforcing film in which a release liner 5 is temporarily adhered to the main surface of the adhesive layer 2 . FIG. 3 is a cross-sectional view showing a state where the reinforcing film 10 is attached to the surface of the device 20 .

By peeling and removing the release liner 5 from the surface of the adhesive layer 2 , the exposed surface of the adhesive layer 2 is attached to the surface of the device 20 , and the reinforcing film 10 is attached to the surface of the device 20 . This state is a state in which the adhesive layer 2 is before photocuring, and the reinforcing film 10 (adhesive layer 2 ) is temporarily adhered to the device 20 . By photocuring the adhesive layer 2 , the adhesive force at the interface between the device 20 and the adhesive layer 2 is increased, whereby the device 20 and the reinforcing film 10 are fixed.

"Adhesion" refers to the state where the two laminated layers are firmly bonded, and the peeling at the interface between the two is impossible or difficult. "Temporary adhesion" refers to the 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.

In the reinforced film shown in FIG. 2 , the film substrate 1 is fixed to the adhesive layer 2 , and the release liner 5 is temporarily adhered to the adhesive layer 2 . When the film substrate 1 and the release liner 5 are peeled off, peeling occurs at the interface between the adhesive layer 2 and the release liner 5 , and the state where the adhesive layer 2 is fixed to the film substrate 1 is maintained. No adhesive remains on the release liner 5 after peeling off.

In the device with the reinforcing film 10 shown in FIG. 3 , the device 20 and the adhesive layer 2 are in a temporary adhesion state before the adhesive layer 2 is hardened by light. When the film substrate 1 is peeled off from the device 20 , peeling occurs at the interface between the adhesive layer 2 and the device 20 , and the adhesive layer 2 is maintained on the film substrate 1 . There is no adhesive remaining on the device 20, so secondary processing is easy. After photocuring the adhesive layer 2, the adhesive force between the adhesive layer 2 and the device 20 increases, so it is difficult to peel the film 1 from the device 20, and if the two are peeled off, there is a possibility that the adhesive layer 2 will be coagulated and destroyed. Condition.

[Composition of Reinforcing Membrane] ＜Film substrate＞ As the film substrate 1, a plastic film is used. In order to fix the film substrate 1 and the adhesive layer 2 , it is preferable that the surface of the film substrate 1 on which the adhesive layer 2 is attached is not subjected to release treatment.

The thickness of the film substrate is, for example, about 4 to 500 μm. From the viewpoint of reinforcing the device by imparting rigidity or impact mitigation, the thickness of the film substrate 1 is preferably at least 12 μm, more preferably at least 30 μm, and still more preferably at least 45 μm. The thickness of the film substrate 1 is preferably 300 μm or less, more preferably 200 μm or less, from the viewpoint of making the reinforcing film flexible and improving handleability. From the viewpoint of both mechanical strength and flexibility, the compressive strength of the film substrate 1 is preferably 100-3000 kg/cm ² , more preferably 200-2900 kg/cm ² , and still more preferably 300-2800 kg /cm ² , preferably 400-2700 kg/cm ² .

The plastic material constituting the film substrate 1 may, for example, be polyester-based resin, polyolefin-based resin, cyclic polyolefin-based resin, polyamide-based resin or polyimide-based resin. In the reinforcing film for optical devices such as displays, the film substrate 1 is preferably a transparent film. Also, when photocuring the adhesive layer 2 by irradiating active light from the film base 1 side, the film base 1 preferably has transparency to the active light used for curing the adhesive layer. Polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are suitably used in terms of both mechanical strength and transparency. When the adhesive layer is cured by irradiating active rays from the adherend side, it is only necessary for the adherend to be transparent to the actinic rays, and the film substrate 1 may be opaque to the actinic rays.

On the surface of the film substrate 1, functional coatings such as an easy-adhesive layer, an easy-slip layer, a release layer, an antistatic layer, a hard coat layer, and an anti-reflection layer can be provided. Furthermore, as mentioned above, in order to fix the film substrate 1 and the adhesive layer 2 , it is preferable not to provide a release layer on the surface of the film substrate 1 where the adhesive layer 2 is attached.

＜Adhesive layer＞ The adhesive layer 2 fixedly laminated on the film substrate 1 contains a photocurable composition containing a base polymer as a high molecular weight component, a photocuring agent, and a photopolymerization initiator. The photocurable composition constituting the adhesive layer may contain an oligomer having a weight average molecular weight smaller than that of the base polymer as a high molecular weight component.

The adhesive layer 2 is easy to perform secondary processing because the adhesive force between the adhesive layer 2 and the adherend such as devices or device parts is small before photohardening. Since the adhesion of the adhesive layer 2 to the adherend is improved by photocuring, even when the device is used, the reinforcing film is not easily peeled off from the device surface, and the bonding reliability is excellent.

When the reinforcing film is used in optical devices such as displays, the total light transmittance of the adhesive layer 2 is preferably at least 80%, more preferably at least 85%, and still more preferably at least 90%. The haze of the adhesive layer 2 is preferably 2% or less, more preferably 1% or less, further preferably 0.7% or less, especially preferably 0.5% or less.

(high molecular weight component) The adhesive layer contains a base polymer as a high molecular weight component. The base polymer is the main constituent of the adhesive composition. As the high molecular weight component, in addition to the base polymer, a polymer having a molecular weight lower than that of the base polymer, that is, an oligomer may be contained.

In terms of excellent optical transparency and adhesiveness, easy control of adhesiveness, and excellent compatibility with oligomers or light hardeners, the adhesive composition preferably contains an acrylic polymer as the base polymer, Preferably, more than 50% by weight of the adhesive composition is an acrylic polymer.

As an acrylic polymer, what contains an alkyl (meth)acrylate as a main monomer component is used suitably. In addition, in this specification, "(meth)acryl" means acryl and/or methacryl.

As the alkyl (meth)acrylate, an alkyl (meth)acrylate having 1 to 20 carbon atoms in the alkyl group is suitably used. The alkyl group of the alkyl (meth)acrylate may have a branch or may have a cyclic alkyl group (alicyclic alkyl group).

Specific examples of alkyl (meth)acrylates having a chain alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylate ) isobutyl acrylate, second butyl (meth)acrylate, third butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate ester, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylate ) nonyl acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate base ester, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, ( Cetyl methacrylate, Heptadecyl (meth)acrylate, Octadecyl (meth)acrylate, Isostearyl (meth)acrylate, Decadecyl (meth)acrylate Nonalkyl ester, eicosyl (meth)acrylate, etc.

Specific examples of alkyl (meth)acrylates having an alicyclic alkyl group include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and cycloheptyl (meth)acrylate. Cycloalkyl (meth)acrylates such as cyclooctyl (meth)acrylate; (meth)acrylates with bicyclic aliphatic hydrocarbon rings such as iso-(meth)acrylate; Dicyclopentyl acrylate, Dicyclopentyloxyethyl (meth)acrylate, Tricyclopentyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl (meth)acrylate (meth)acrylates having aliphatic hydrocarbon rings having three or more rings, such as 2-adamantyl ester and 2-ethyl-2-adamantyl (meth)acrylate. The alkyl (meth)acrylate having an alicyclic alkyl group may have a substituent on a ring such as 3,3,5-trimethylcyclohexyl (meth)acrylate. Also, the alkyl (meth)acrylate having an alicyclic alkyl group may be (meth)acrylic acid containing a condensed ring of an alicyclic structure and a ring structure having an unsaturated bond, such as dicyclopentenyl (meth)acrylate. )Acrylate.

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

The acrylic base polymer preferably contains a monomer component having a crosslinkable functional group as a copolymerization component. By introducing a cross-linked structure into the base polymer, the cohesive force is improved, the adhesive force of the adhesive layer 2 is improved, and there is a tendency for the paste residue on the adherend to be reduced during secondary processing.

As a monomer which has a crosslinkable functional group, the monomer containing a hydroxyl group, or the monomer containing a carboxyl group is mentioned. The hydroxyl group or carboxyl group of the base polymer becomes a reaction point with the crosslinking agent described below. For example, when an isocyanate-based crosslinking agent is used, it is preferable to contain a hydroxyl group-containing monomer as a copolymerization component of the base polymer. When using an epoxy-type crosslinking agent, it is preferable to contain a carboxyl group-containing monomer as a copolymerization component of a base polymer.

Examples of hydroxyl-containing monomers include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxy (meth)acrylate -Hydroxyhexyl, 8-Hydroxyoctyl (meth)acrylate, 10-Hydroxydecyl (meth)acrylate, 12-Hydroxylauryl (meth)acrylate, 4-(Hydroxymethyl)acrylate ) cyclohexyl methyl ester, etc. Examples of carboxyl-containing monomers include (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, butyric acid, Acrylic acid, etc.

In the acrylic base polymer, the total amount of the hydroxyl group-containing monomer and the carboxyl group-containing monomer is preferably 1 to 30% by weight, more preferably 2 to 25% by weight, and even more preferably Preferably, it is 3 to 20% by weight. It is particularly preferable that the content of the carboxyl group-containing monomer is within the above-mentioned range.

The acrylic base polymer may also contain the following monomers as constituent monomers: N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinyl Piperidine, Vinylpyrroline, Vinylpyrrole, Vinylimidazole, Vinyloxazole, Vinylpyrroline, N-Acrylamide, N-Vinylcarboxamides, N-Vinylcaprolactam and other nitrogen-containing monomers.

The acrylic base polymer may also contain monomer components other than the above. The acrylic base polymer can also contain the following monomers as monomer components: such as vinyl ester monomers, aromatic vinyl monomers, epoxy group-containing monomers, vinyl ether monomers, sulfo group-containing monomers, Monomers containing phosphoric acid groups, monomers containing acid anhydride groups, etc.

The base polymer may contain substantially no nitrogen atoms. The ratio of nitrogen in the constituent elements of the base polymer may be 0.1 mol % or less, 0.05 mol % or less, 0.01 mol % or less, 0.005 mol % or less, 0.001 mol % or less, or zero. By using a base polymer that does not substantially contain nitrogen atoms, the increase in the adhesive force (initial adhesive force) of the adhesive layer before photohardening when there is a surface activation treatment such as plasma treatment on the adherend is suppressed Propensity.

The monomers that do not contain nitrogen atoms such as monomers containing cyano groups, monomers containing lactamide structures, monomers containing amide groups, monomers containing phospholine rings, etc., are used as the constituent monomers of the basic polymer components to obtain a base polymer substantially free of nitrogen atoms. Furthermore, when a crosslinked structure is introduced into the base polymer, it is sufficient that the polymer before the introduction of the crosslinked structure does not substantially contain nitrogen atoms, and the crosslinking agent may also contain nitrogen atoms. When the base polymer does not substantially contain nitrogen atoms, the base polymer preferably contains a carboxyl group-containing monomer as a monomer component from the viewpoint of improving the cohesiveness of the adhesive.

The glass transition temperature of the acrylic base polymer is preferably -10°C or lower, more preferably -15°C or lower, and still more preferably -20°C or lower, from the viewpoint of imparting excellent adhesiveness to the adhesive. The glass transition temperature of the acrylic base polymer may also be -25°C or lower or -30°C or lower. The glass transition temperature of the acrylic base polymer is usually -100°C or higher, and may be -80°C or higher or -70°C or higher.

The glass transition temperature is the temperature at which the loss tangent tanδ in viscoelasticity measurement reaches its maximum value (peak temperature). The theoretical Tg can also be used instead of the glass transition temperature obtained by viscoelasticity measurements. The theoretical Tg is calculated by the following Fox formula from the glass transition temperature Tg _i of the homopolymer of the monomer components constituting the acrylic base polymer and the weight fraction W _i of each monomer component. 1/Tg＝Σ(W _i /Tg _i )

Tg is the glass transition temperature of the polymer (unit: K), W _i is the weight fraction of the monomer component i constituting the chain segment (copolymerization ratio on a weight basis), and Tg _i is the glass of the homopolymer of the monomer component i Transition temperature (unit: K). As the glass transition temperature of a homopolymer, the value described in Polymer Handbook 3rd edition (John Wiley & Sons, Inc., 1989) can be used. The Tg of homopolymers of monomers not described in the above documents may be the peak top temperature of tan δ obtained by dynamic viscoelasticity measurement.

By including a high Tg monomer in the base polymer as a constituent monomer component, the cohesive force of the adhesive is improved, the secondary processability before photocuring is excellent, and there is a tendency to show high adhesion reliability after photocuring. A high Tg monomer means a monomer having a high glass transition temperature (Tg) of the homopolymer. Examples of monomers whose homopolymer Tg is 40°C or higher include cyclohexyl methacrylate (Tg: 83°C), tetrahydrofurfuryl methacrylate (Tg: 60°C), dicyclopentanyl methacrylate Esters (Tg: 175°C), Dicyclopentyl Acrylate (Tg: 120°C), Isomethacrylate (Tg: 155°C), Isomethacrylate (Tg: 97°C), Methyl Methacrylate (Tg: 105°C), 1-adamantyl methacrylate (Tg: 250°C), 1-adamantyl acrylate (Tg: 153°C) and other (meth)acrylates; methacrylic acid (Tg: 228°C), acid monomers such as acrylic acid (Tg: 106°C), etc.

In the acrylic base polymer, the content of the monomer whose Tg of the homopolymer is 40°C or higher is preferably at least 1% by weight, more preferably at least 2% by weight, and still more preferably 3% by weight or more. In order to form an adhesive layer with moderate hardness and excellent secondary processability, the monomer component of the base polymer preferably includes a monomer component whose homopolymer Tg is 80°C or higher, and more preferably includes a homopolymer The Tg of the product is a monomer component above 100°C. In the acrylic base polymer, the content of the monomer having a homopolymer Tg of 100°C or higher is preferably at least 0.1% by weight, more preferably at least 0.5% by weight, and still more preferably 1% by weight or more, preferably 2% by weight or more. On the other hand, from the viewpoint of imparting moderate flexibility to the adhesive, the content of monomers having a Tg of 40° C. or higher in the homopolymer is preferably 50% by weight or less, more preferably It is preferably 40% by weight or less, more preferably 30% by weight or less, and may be 20% by weight or less or 10% by weight or less. From the same viewpoint, the content of the monomer whose Tg of the homopolymer is 80°C or higher is preferably 30% by weight or less, more preferably 25% by weight or less, and still more preferably 20% by weight or less, may be 15% by weight or less, 10% by weight or less, or 5% by weight or less.

The acrylic polymer as the base polymer is obtained by polymerizing the above-mentioned monomer components by various known methods such as solution polymerization, emulsion polymerization, block polymerization, and the like. The solution polymerization method is preferable from the standpoint of the balance of properties such as adhesive force and holding power of the adhesive, or cost. As a solvent for solution polymerization, ethyl acetate, toluene and the like are used. The solution concentration is usually about 20 to 80% by weight. As a polymerization initiator used for solution polymerization, various well-known ones, such as an azo system and a peroxide system, can be used. To adjust the molecular weight, chain transfer agents can be used. The reaction temperature is usually about 50 to 80°C, and the reaction time is usually about 1 to 8 hours.

The weight average molecular weight of the acrylic base polymer is preferably from 100,000 to 2 million, more preferably from 200,000 to 1.5 million, and still more preferably from 300,000 to 1 million. Furthermore, when a crosslinked structure is introduced into the base polymer, the molecular weight of the base polymer means the molecular weight before the introduction of the crosslinked structure.

As described above, the adhesive composition may contain an oligomer as a high molecular weight component in addition to the base polymer. The oligomer is preferably an acrylic oligomer from the point of being excellent in compatibility with the acrylic base polymer.

The acrylic oligomer contains an alkyl (meth)acrylate as a main constituent monomer component, and is a component having a weight average molecular weight smaller than that of the above-mentioned acrylic base polymer. The weight molecular weight of the acrylic oligomer is about 1,000 to 30,000, may be 2,000 or more, 2,500 or more, or 3,000 or more, or may be 20,000 or less, 15,000 or less, or 10,000 or less.

As an acrylic oligomer, what contains an alkyl (meth)acrylate as a main monomer component is used suitably. As the monomer component constituting the acrylic oligomer, the monomers exemplified above as the monomer component constituting the acrylic base polymer may, for example, be mentioned. The content of the alkyl (meth)acrylate in the monomer components constituting the acrylic oligomer is preferably at least 40% by weight, more preferably at least 50% by weight, based on the total amount of monomer components constituting the base polymer , and more preferably 55% by weight or more. From the viewpoint of raising the glass transition temperature of the oligomer, it is preferable to include a monomer whose Tg of the homopolymer is 40° C. or higher as the monomer component.

The glass transition temperature of the acrylic oligomer is preferably at least 40°C, more preferably at least 50°C, and still more preferably at least 60°C, from the viewpoint of improving the impact resistance of the reinforcing film after photocuring the adhesive layer. above. The glass transition temperature of the acrylic oligomer is preferably higher than the glass transition temperature of the acrylic base polymer. The glass transition temperature of the acrylic oligomer is usually 200°C or lower, and may be 160°C or lower, 140°C or lower, or 120°C or lower.

Like the acrylic base polymer, the acrylic oligomer may also contain crosslinkable functional groups. For example, when using an epoxy-based crosslinking agent, as long as the acrylic oligomer has a carboxyl group, a crosslinked structure may be introduced by the reaction between the carboxyl group of the acrylic oligomer and the epoxy group of the crosslinking agent. .

The acrylic oligomer may not contain nitrogen atoms substantially. The ratio of nitrogen among the constituent elements of the oligomer may be 0.1 mol % or less, 0.05 mol % or less, 0.01 mol % or less, 0.005 mol % or less, 0.001 mol % or less, or zero.

Acrylic oligomers are obtained by polymerizing the above monomer components by various polymerization methods. Various polymerization initiators can be used for the polymerization of the acrylic oligomer. In addition, a chain transfer agent may be used for the purpose of adjusting the molecular weight.

The content of the acrylic oligomer in the adhesive composition is not particularly limited. From the viewpoint of adjusting the adhesion of the adhesive layer to an appropriate range and improving impact resistance, the amount of the oligomer is preferably 0.1 to 20 parts by weight relative to 100 parts by weight of the base polymer, more preferably 0.1 to 20 parts by weight. 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight, and may be 2 to 8 parts by weight or 3 to 7 parts by weight.

The adhesive composition preferably contains at least one monomer having an alicyclic structure as a monomer unit of a high molecular weight component. When the adhesive composition contains an acrylic base polymer and an acrylic oligomer as a high molecular weight component, it is preferable that either or both of the base polymer and the oligomer contain one or more of them having an alicyclic structure. The monomer as a monomer unit. When the pressure-sensitive adhesive composition does not contain an acrylic oligomer, it is preferable that the acrylic base polymer contains at least one monomer having an alicyclic structure as a monomer unit. When the high molecular weight component contains a monomer unit having an alicyclic structure, the impact resistance of the reinforced film tends to be improved.

As a specific example of the monomer which has an alicyclic structure, the alkyl (meth)acrylate which has the said alicyclic alkyl group is mentioned. Among them, from the viewpoint of suppressing an excessive increase in the glass transition temperature of the adhesive, the glass transition temperature of the homopolymer is preferably 150° C. or lower, and the number of rings in the alicyclic structure is preferably 3 or lower, more preferably 2 or lower. Most preferably, the alicyclic ring is a monocyclic ring. The glass transition temperature of the homopolymer of the monomer having an alicyclic structure is preferably 40-120°C, more preferably 50-105°C, and may be 55-100°C.

As mentioned above, the monomer unit having an alicyclic structure can be included in either the base polymer or the oligomer, but the glass transition temperature of the adhesive is kept relatively low, and both adhesiveness and impact resistance are considered. From a viewpoint, it is preferable that an acrylic oligomer contains the monomer unit which has an alicyclic structure. In the acrylic oligomer, the content of the monomer having an alicyclic structure (alkyl (meth)acrylate having an alicyclic alkyl group) is preferably 40% by weight or more based on the total amount of monomer components. More preferably, it is 50 weight% or more, and may be 60 weight% or more, 70 weight% or more, 80 weight% or more, or 90 weight% or more.

When the acrylic base polymer contains a monomer unit having an alicyclic structure, it is preferably 30% by weight or less, more preferably 20% by weight or less, and still more preferably 10% by weight, based on the total amount of monomer components. % or less, or 5% by weight or less. The amount of the monomer having an alicyclic structure may be 1% by weight or more or 3% by weight or more with respect to the total amount of monomer components constituting the acrylic base polymer.

The amount of monomer units having an alicyclic structure is preferably 0.3 to 25% by weight, more preferably 0.5 to 20% by weight, and still more preferably 1 to 15% by weight relative to the total amount of monomer components constituting the high molecular weight component as a whole. % by weight may be 2 to 10% by weight or 2.5 to 8% by weight. When the ratio of the monomer unit which has an alicyclic structure with respect to the whole high molecular weight component is the said range, there exists a tendency for the impact resistance of a reinforced film to become especially favorable.

(crosslinking agent) From the viewpoint of imparting moderate cohesive force to the adhesive, it is preferable to introduce a crosslinked structure into the base polymer. For example, a crosslinked structure is introduced by adding a crosslinking agent to the solution after polymerizing the base polymer, and heating as necessary. The crosslinking agent has two or more crosslinkable functional groups in one molecule. The crosslinking agent may have three or more crosslinkable functional groups in one molecule.

Examples of the crosslinking agent include: isocyanate-based crosslinking agents, epoxy-based crosslinking agents, azoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, metal chelate Compound cross-linking agent, etc. These crosslinking agents react with functional groups such as hydroxyl or carboxyl introduced into the base polymer to form a crosslinking structure. Isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred because they have high reactivity with the hydroxyl group or carboxyl group of the base polymer and are easy to introduce a crosslinked structure.

As the isocyanate-based crosslinking agent, a polyisocyanate having two or more isocyanate groups in one molecule is used. The isocyanate-based crosslinking agent may have three or more isocyanate groups in one molecule. As the isocyanate crosslinking agent, for example, lower aliphatic polyisocyanates such as butyl diisocyanate and hexamethylene diisocyanate; cyclopentyl diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, etc. Alicyclic isocyanate such as isocyanate; Aromatic isocyanate such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; Trimethylolpropane/toluene diisocyanate trimethylolpropane/toluene diisocyanate Polymer adducts (such as "Coronate L" manufactured by Tosoh), trimethylolpropane/hexamethylene diisocyanate trimer adducts (such as "Coronate HL" manufactured by Tosoh), xylylene diisocyanate Trimethylolpropane adducts of isocyanates (such as "Takenate D110N" manufactured by Mitsui Chemicals), isocyanurates of hexamethylene diisocyanate (such as "Coronate HX" manufactured by Tosoh) and other isocyanate adducts wait.

As an epoxy-type crosslinking agent, the polyfunctional epoxy compound which has 2 or more epoxy groups in 1 molecule is used. The epoxy-based crosslinking agent may have three or more or four or more epoxy groups in one molecule. The epoxy group of the epoxy-based crosslinking agent may also be a glycidyl group. Examples of epoxy-based crosslinking agents include: N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-di Glycidylaminomethyl) cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol Alcohol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylol Diglycidyl adipate, diglycidyl adipate, diglycidyl phthalate, tris(2-hydroxyethyl) isocyanurate triglycidyl ether, resorcinol diglycidyl ether, bis Phenol-S-diglycidyl ether, etc. As the epoxy-based crosslinking agent, commercial items such as "Denacol" manufactured by Nagase ChemteX, "Tetrad X" and "Tetrad C" manufactured by Mitsubishi Gas Chemical can be used.

Even in cases where the base polymer does not substantially contain nitrogen atoms, the crosslinking agent may contain nitrogen atoms. For example, an isocyanate crosslinking agent can also be used to introduce a crosslinked structure into a base polymer that does not substantially contain nitrogen atoms. In the case where the base polymer does not substantially contain nitrogen atoms, by using a cross-linking agent that does not contain nitrogen atoms such as an epoxy-based cross-linking agent, there is a difference in initial adhesion due to surface activation such as plasma treatment. Tendency to rise is suppressed.

The amount of the crosslinking agent can be appropriately adjusted according to the composition or molecular weight of the base polymer. The amount of crosslinking agent used is about 0.01-10 parts by weight, preferably 0.1-5 parts by weight, more preferably 0.2-3 parts by weight, and still more preferably 0.3-2 parts by weight, relative to 100 parts by weight of the base polymer. , or 0.4 to 1.5 parts by weight or 0.5 to 1 parts by weight. By using a cross-linking agent to introduce a cross-linked structure into the base polymer and make the adhesive have a moderate hardness, the adhesive force of the adhesive before photohardening to the adherend becomes smaller, and the paste to the adherend when peeling off The tendency of the agent residue to be suppressed.

(light hardener) The adhesive composition constituting the adhesive layer 2 contains a photocuring agent in addition to the base polymer. When the adhesive layer 2 including the photocurable adhesive composition is photocured after being bonded to an adherend, the adhesive force with the adherend is improved.

The photocuring agent has two or more polymerizable functional groups in one molecule. As a polymerizable functional group, it is preferable that it has polymerizability by photoradical reaction, and as a photocuring agent, it is preferable that it is a compound which has 2 or more ethylenic unsaturated bonds in 1 molecule. In addition, the photocuring agent is preferably a compound showing compatibility with the base polymer. The photocuring agent is preferably liquid at normal temperature from the point of showing moderate compatibility with the base polymer. Since the light hardener is compatible with the base polymer and uniformly dispersed in the composition, the contact area with the adherend can be ensured, and an adhesive layer 2 with high transparency can be formed. In addition, since the base polymer and the light hardener exhibit moderate compatibility, the cross-linked structure obtained by using the light hardener can be uniformly introduced into the adhesive layer 2 after light hardening, and the adhesion with the adherend can be achieved. The tendency for the force to rise appropriately.

It is preferable to use polyfunctional (meth)acrylate as a photocuring agent at the point which has high compatibility with an acrylic base polymer. Examples of polyfunctional (meth)acrylates include polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate. , Bisphenol A ethylene oxide modified di(meth)acrylate, bisphenol A propylene oxide modified di(meth)acrylate, alkanediol di(meth)acrylate, tricyclodecane di Methanol di(meth)acrylate, Ethoxylated isocyanuric acid tri(meth)acrylate, Pentaerythritol tri(meth)acrylate, Pentaerythritol di(meth)acrylate, Trimethylolpropane tri(meth)acrylate base) acrylate, di-trimethylolpropane tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol poly(meth)acrylate, Dipentaerythritol hexa(meth)acrylate, Neopentyl glycol di(meth)acrylate, Glycerin di(meth)acrylate, Urethane(meth)acrylate, Epoxy(meth)acrylate ester, butadiene (meth)acrylate, isoprene (meth)acrylate, etc.

From the point of view of reducing the resistance of the adhesive, the light hardener is preferably a compound having a polyether chain such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, especially Polyethylene glycol di(meth)acrylate. Two or more types of photocuring agents may be used in combination.

From the viewpoint of compatibility with the base polymer, the molecular weight of the photocuring agent is preferably 1500 or less, more preferably 1000 or less, further preferably 500 or less, especially preferably 400 or less. From the perspective of compatibility with the base polymer and the improvement of adhesion after photocuring, the functional group equivalent (g/eq) of the photocuring agent is preferably 500 or less, more preferably 400 or less, and even more preferably It is less than 300, preferably less than 200. On the other hand, if the functional group equivalent of the photocuring agent is too small, the crosslinking point density of the adhesive layer after photocuring may become high and the adhesiveness may decrease. Therefore, the functional group equivalent weight of the photocuring agent is preferably 80 or more, more preferably 100 or more, and still more preferably 130 or more.

The content of the light hardener in the adhesive composition is preferably 3 to 100 parts by weight relative to 100 parts by weight of the base polymer. By making the compounding quantity of a photocuring agent into the said range, the adhesiveness of the adhesive layer after photocuring and an adherend can be adjusted to an appropriate range. The content of the light hardener is more preferably 10-80 parts by weight, more preferably 20-70 parts by weight, particularly preferably 30-65 parts by weight, or 35-60 parts by weight relative to 100 parts by weight of the base polymer. Or 40 to 55 parts by weight.

The larger the amount of the photocuring agent, the higher the ratio of the highly elastic component (hard segment) in the photocured adhesive layer, and the tendency to improve the impact resistance. Moreover, when using the compound which has a polyether chain as a photocuring agent, there exists a tendency for the electric resistance of an adhesive agent to become small as the quantity of photocuring agent increases. On the other hand, when the amount of the photocuring agent is too large, the loss of viscosity of the adhesive after photocuring may cause a decrease in adhesiveness or a decrease in impact resistance.

(photopolymerization initiator) The photopolymerization initiator generates active species through the irradiation of active light, and promotes the hardening reaction of the photohardener. As the photopolymerization initiator, photocation initiators (photoacid generators), photoradical initiators, photoanion initiators (photobase generators) and the like are used depending on the type of photocuring agent and the like. When using an ethylenically unsaturated compound such as polyfunctional acrylate as a photocuring agent, it is preferable to use a photoradical initiator as a polymerization initiator.

The photo-radical initiator generates free radicals by the irradiation of active light, and promotes the radical polymerization reaction of the photo-hardener by moving the free radicals from the photo-radical initiator to the photo-hardener. As photo-radical initiators (photo-radical generators), those that generate free radicals are preferably irradiated with short-wavelength visible light or ultraviolet light with a wavelength less than 450 nm, such as: hydroxy ketones, benzoyl Dimethyl ketals, amino ketones, acyl phosphine oxides, benzophenones, trichloromethyl derivatives, etc. The photoradical initiator may be used alone or in combination of two or more.

The content of the photopolymerization initiator in the adhesive layer 2 is preferably 0.01 to 5 parts by weight, more preferably 0.02 to 3 parts by weight, and still more preferably 0.03 to 2 parts by weight relative to 100 parts by weight of the base polymer. The content of the photopolymerization initiator in the adhesive layer 2 is preferably 0.02 to 20 parts by weight, more preferably 0.05 to 10 parts by weight, and still more preferably 0.1 to 7 parts by weight relative to 100 parts by weight of the photohardener.

(other additives) In addition to the components exemplified above, the adhesive layer may also contain a silane coupling agent, an adhesion imparting agent, a crosslinking accelerator, a crosslinking retarder, a plasticizer, a softener, an anti-corrosion agent, etc. within the range that does not impair the characteristics of the present invention. Additives such as oxidizing agents, anti-deterioration agents, fillers, colorants, ultraviolet absorbers, surfactants, antistatic agents, etc.

As a crosslinking accelerator, organometallic compounds, such as an organometallic complex (chelate compound), the compound of a metal and an alkoxy group, and the compound of a metal and an acyloxy group; and a tertiary amine etc. are mentioned. From the viewpoint of suppressing the progress of the crosslinking reaction in a solution state at normal temperature and securing the pot life of the adhesive composition, an organometallic compound is preferable. Furthermore, the crosslinking accelerator is preferably an organometallic compound that is liquid at normal temperature in terms of easily introducing a uniform crosslinked structure over the entire thickness direction of the adhesive layer. The metal of the organometallic compound may, for example, be iron, tin, aluminum, zirconium, zinc, titanium, lead, cobalt or zinc.

Examples of the crosslinking retarder include β-ketones such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate. Esters; β-diketones such as acetylacetone, 2,4-hexanedione, and benzoylacetone; alcohols such as tertiary butanol.

[Production of reinforcement film] A reinforced film is obtained by laminating a photocurable adhesive layer 2 on a film substrate 1 . The adhesive layer 2 can be directly formed on the film substrate 1 , or a sheet-shaped adhesive layer formed on other substrates can be transferred onto the film substrate 1 .

By roll coating, contact roll coating, gravure coating, reverse coating, roll brush coating, spray coating, dip roll coating, rod coating, blade coating, air knife coating, curtain coating , lip coating, die coating, etc. The above-mentioned adhesive composition is applied on a substrate, and the solvent is dried and removed as necessary to form an adhesive layer. As a drying method, an appropriate method can be suitably adopted. The heating and drying temperature is preferably from 40°C to 200°C, more preferably from 50°C to 180°C, further preferably from 70°C to 170°C. The drying time is preferably from 5 seconds to 20 minutes, more preferably from 5 seconds to 15 minutes, and still more preferably from 10 seconds to 10 minutes.

The thickness of the adhesive layer 2 is, for example, about 1 to 300 μm. There is a tendency that the adhesiveness with an adherend improves so much that the thickness of the adhesive layer 2 is large. On the other hand, when the thickness of the pressure-sensitive adhesive layer 2 is too large, the fluidity before photocuring is high, and handling may become difficult. Therefore, the thickness of the adhesive layer 2 is preferably 5-100 μm, more preferably 8-50 μm, and still more preferably 10-40 μm.

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

After the cross-linking structure is introduced into the polymer by the cross-linking agent, the light hardener remains unreacted. Therefore, the photocurable adhesive layer 2 containing a high molecular weight component and a photocurer is formed. When forming the adhesive layer 2 on the film substrate 1 , it is preferable to attach a release liner 5 to the adhesive layer 2 for the purpose of protecting the adhesive layer 2 . Crosslinking may also be performed after attaching the release liner 5 on the adhesive layer 2 .

In the case of forming the adhesive layer 2 on another base material, after drying the solvent, the adhesive layer 2 is transferred onto the film base material 1 to obtain a reinforced film. The base material used to form the adhesive layer can also be directly used as the release liner 5 .

As the release liner 5, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films are preferably used. The thickness of the release liner is usually 3 to 200 μm, preferably about 10 to 100 μm. On the contact surface of the release liner 5 and the adhesive layer 2, it is preferable to implement a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, or silicon oxide powder. The release treatment. After the surface of the release liner 5 is released, peeling occurs at the interface between the adhesive layer 2 and the release liner 5 , maintaining the state that the adhesive layer 2 is fixed on the film substrate 1 . Antistatic treatment may also be performed on either or both of the release liner 5's release-treated surface and the non-treated surface. By subjecting the release liner 5 to antistatic treatment, it is possible to suppress electrification when the release liner is peeled from the adhesive layer.

[Characteristics of Reinforced Film and Use of Reinforced Film] The reinforcing film of the present invention is used by being attached to a device or a device component. The adhesive layer 2 of the reinforcing film 10 is fixed to the film base material 1, and the adhesive force with the adherend is small after bonding with the adherend and before photohardening. Therefore, the reinforcing film is easily peeled off from the adherend before photocuring.

The adherend to which the reinforcing film is bonded is not particularly limited, and examples thereof include various electronic devices, optical devices, and their constituent parts. The reinforcement film can be attached to the entire surface of the adherend, or selectively attached only to the part that needs reinforcement (reinforcement target area). In addition, after affixing the reinforcing film to the entire portion requiring reinforcement (reinforcement target area) and non-reinforcement target area (non-reinforcement target area), the reinforcing film bonded to the non-reinforcement target area can be cut and removed. If the adhesive is not photohardened, the reinforcing film is temporarily adhered to the surface of the adherend, so the reinforcing film can be easily peeled off from the surface of the adherend. It is also possible to attach the reinforcement film to the reinforcement target area and the non-reinforcement target area, selectively irradiate the reinforcement target area with light to harden the adhesive, and then selectively peel off the non-reinforcement target area where the adhesive has not hardened. membrane.

Appropriate rigidity is imparted by attaching a reinforcing film, so operability improvement and breakage prevention effects are expected. In the manufacturing process of the device, when attaching the reinforcing film to the product in progress, the reinforcing film can be attached to the large-sized product in process before being cut into the size of the product. It is also possible to attach the reinforcement film to the parent roll of the device manufactured by the roll-to-roll process in a roll-to-roll manner.

In terms of easy peeling from the adherend and prevention of paste residue on the adherend after peeling off the reinforcing film, the adhesive force (initial adhesive force) between the adhesive layer 2 and the adherend before photohardening is preferably 1 N/25 mm or less, more preferably 0.5 N/25 mm or less, further preferably 0.3 N/25 mm or less, may be 0.1 N/25 mm or less or 0.05 N/25 mm or less. From the viewpoint of preventing peeling of the reinforcing film during storage or handling, the adhesive force between the adhesive layer 2 and the adherend before photocuring is preferably 0.005 N/25 mm or more, more preferably 0.01 N/25 mm or more . Next, the force was obtained by using a polyimide film as an adherend, and obtained it by a peeling test at a tensile speed of 300 mm/min and a peeling angle of 180°. Unless otherwise specified, the adhesive force is measured at 25°C. The adhesive strength between the adhesive layer and the adherend before photohardening was measured using a sample obtained by standing at 25°C for 30 minutes after bonding.

It is also possible to activate the adherend such as the polyimide film on the surface of the device for the purpose of cleaning before attaching the reinforcing film. The adherend whose surface has been activated contains more active groups such as hydroxyl, carbonyl, and carboxyl, and the adhesive force is easy to increase through the intermolecular interaction with the polar functional groups of the base polymer of the adhesive. Especially when the adherend is polyimide, the interaction with the polar functional group of the base polymer is activated by activating the amide acid, the terminal amino group or carboxyl group (or carboxylic acid anhydride group), etc. Strong, so there are cases where the initial adhesive force is greatly increased by activation treatment.

When the initial adhesive force becomes too large, peeling operations such as secondary processing may become difficult. As described above, since the base polymer does not substantially contain nitrogen atoms, it is possible to suppress an excessive increase in initial adhesive force to an adherend whose surface has been activated. The adhesion between the surface-activated adherend and the adhesive layer before photohardening is preferably less than 2.5 times the adhesion between the surface-activated adherend and the adhesive layer before photohardening, more preferably 2 times or less, and more preferably 1.5 times or less.

The surface resistance of the adhesive layer 2 before photocuring is preferably not more than 1×10 ¹² Ω, more preferably not more than 5×10 ¹¹ Ω. Since the adhesive layer before photohardening has low resistance, electrical damage to the adherend due to static electricity or the like when the reinforcing film is peeled off from the adherend can be suppressed. The surface resistance of the adhesive layer 2 is preferably 1×10 ¹² Ω or less, more preferably 5×10 ¹¹ Ω or less even after photocuring. Usually, the surface resistance of the adhesive layer hardly changes before and after photohardening. As mentioned above, by using the compound which has a polyether chain as a light hardening agent, there exists a tendency for the adhesive agent layer to reduce resistance.

After bonding the reinforcing film to the adherend, the adhesive layer 2 is irradiated with active light to photocure the adhesive layer. Actinic rays may, for example, be ultraviolet rays, visible light, infrared rays, X-rays, α-rays, β-rays, or γ-rays. The active light rays are preferably ultraviolet rays in terms of suppressing hardening of the adhesive layer in a stored state and being easy to harden. The irradiation intensity or irradiation time of the active light may be appropriately set according to the composition or thickness of the adhesive layer. Irradiation of the active light to the adhesive layer 2 may be performed from either the film substrate 1 side or the adherend side, or may be irradiated from both sides.

As light hardens, the adhesion of the adhesive layer to the adherend increases. From the point of view of adhesive reliability when the device is practical, the adhesive force between the adhesive layer 2 and the adherend after photocuring is preferably 2 N/25 mm or more, more preferably 3 N/25 mm or more, and furthermore The best is 5 N/25 mm or more. The adhesive strength between the reinforcing film and the adherend after the adhesive layer is photohardened can be 6 N/25 mm or more, 8 N/25 mm or more, 10 N/25 mm or more, 13 N/25 mm or more, or 15 N /25 mm or more. In the reinforcing film, it is preferable that the adhesive layer after photocuring has an adhesive force within the above-mentioned range for the polyimide film. The adhesive force between the adhesive layer 2 and the adherend after light hardening is preferably more than 30 times, more preferably more than 60 times, and more preferably 100 times the adhesive force between the adhesive layer 2 and the adherend before light hardening. more than 150 times, preferably more than 150 times, and also more than 180 times or more than 200 times.

In the use of the completed device, even when an external force is accidentally loaded due to the drop of the device, the loading of heavy goods on the device, the collision of flying objects on the device, etc., it can be reinforced by bonding membrane to prevent damage to the device. As described above, when the high molecular weight component of the adhesive composition contains a monomer unit having an alicyclic structure, impact resistance tends to be improved.

The impact resistance of the reinforced film can be evaluated by the indentation energy. When the indenter is pressed from the film substrate 1 side of the reinforcing film 10, the energy required until a specific load is applied to the adherend 20 bonded to the adhesive layer 2 is the indentation energy. The greater the indentation energy, the greater the resistance. The more excellent the impact resistance is. The indentation energy when the adherend is loaded with a load of 20 N is preferably at least 280 μJ, more preferably at least 300 μJ, further preferably at least 320 μJ, and most preferably at least 330 μJ.

As mentioned above, by attaching the reinforcing film, moderate rigidity is imparted to the adherend, and stress is relaxed and dispersed, so various abnormalities that may occur in the manufacturing process can be suppressed, production efficiency can be improved, and yield can be improved. Since the reinforcing film is easy to peel off from the adherend before the adhesive layer is light-hardened, it is easy to perform secondary processing even if lamination or poor bonding occurs. In addition, processing such as selectively removing the reinforcement film from other than the reinforcement target area is also easy. After the adhesive layer is light-cured, it shows high adhesion to the adherend, the reinforcement film is difficult to peel off from the device surface, excellent adhesion reliability, and high impact resistance, so it can prevent damage to the device due to external impact . [Example]

Examples are given below for further description, but the present invention is not limited to these examples.

[Preparation of basic polymers and oligomers] ＜Base Polymer A＞ In a reaction vessel equipped with a thermometer, a stirrer, a reflux cooling pipe, and a nitrogen gas introduction pipe, 94 parts by weight of butyl acrylate (BA) and 6 parts by weight of acrylic acid (AA) as a monomer, and azo as a thermal polymerization initiator 0.2 parts by weight of diisobutyronitrile (AIBN) and 233 parts by weight of ethyl acetate as a solvent were flowed into nitrogen gas, and nitrogen replacement was performed for about 1 hour while stirring. Then, it heated to 60 degreeC, it was made to react for 7 hours, and the solution of the acryl-type polymer A was obtained.

＜Base Polymer B＞ As monomers, 65 parts by weight of 2-ethylhexyl acrylate (2EHA), 15 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 12 parts by weight of 2-hydroxyethyl acrylate (HEA) were used The solution of the acrylic polymer B was obtained by superposing|polymerizing in the same manner as the preparation of the said base polymer A except having added 8 weight part of methyl methacrylate (MMA).

＜Basic Polymers C～F＞ As a monomer, cyclohexyl methacrylate (CHMA) was used in addition to butyl acrylate (BA) and acrylic acid (AA) at the ratio shown in Table 1, and the amount of solvent (ethyl acetate) was changed to 256 wt. parts, except that, polymerization was carried out in the same manner as the preparation of the above-mentioned base polymer A, and solutions of acrylic polymers C to F were obtained.

＜Oligomer P＞ In a reaction vessel equipped with a thermometer, a stirrer, a reflux cooling pipe, and a nitrogen introduction pipe, 96 parts by weight of cyclohexyl methacrylate (CHMA) and 4 parts by weight of acrylic acid (AA) as monomers, and 2 parts by weight as a chain transfer agent - 3 parts by weight of mercaptoethanol, 0.2 parts by weight of AIBN as a thermal polymerization initiator, and 103 parts by weight of toluene as a solvent were flowed into nitrogen, and nitrogen replacement was performed for about 1 hour while stirring. Then, it heated at 70 degreeC, it was made to react for 3 hours, and it was made to react at 75 degreeC for 2 hours further, and the solution of the acrylic oligomer P was obtained.

＜Oligomer Q＞ In a reaction vessel equipped with a thermometer, a stirrer, a reflux cooling pipe, and a nitrogen gas introduction pipe, 62 parts by weight of dicyclopentanyl methacrylate (DCPMA) and 38 parts by weight of methyl methacrylate (MMA) as monomers were added as 3.5 parts by weight of methyl thioglycolate as a chain transfer agent, 0.2 parts by weight of AIBN as a thermal polymerization initiator, and 100 parts by weight of toluene as a solvent were flowed into nitrogen, and nitrogen replacement was performed for about 1 hour while stirring. Then, it heated to 70 degreeC, and it was made to react for 2 hours, and also it was made to react at 80 degreeC for 4 hours, and it was made to react at 90 degreeC for 1 hour, and the solution of acrylic oligomer Q was obtained.

＜Oligomer R＞ As monomers, 25 parts by weight of 2-ethylhexyl acrylate (2EHA), 70 parts by weight of methyl methacrylate (MMA) and 5 parts by weight of methacrylic acid (MAA) were used. Preparation of Polymer Q Polymerization was carried out in the same manner to obtain a solution of acrylic oligomer R.

The glass transition temperatures of base polymers and oligomers are calculated based on the Fox formula based on the monomer composition. The weight average molecular weight (in terms of polystyrene) 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 (Tetrahydrofuran, tetrahydrofuran) Flow rate: 0.6ml/min Measuring temperature: 40°C Sample column: TSKguardcolumn SuperHZ-H (1) + TSKgel SuperHZM-H (2) Reference column: TSKgel SuperH-RC (1 piece)

The monomer ratios, weight average molecular weight (Mw), and glass transition temperature (Tg) of acrylic polymers A, B, C, D, E, F and acrylic oligomers P, Q, R are shown in a list in in FIG. 1.

[Table 1] Monomer ratio (parts by weight) mw Tg (℃) BA 2EHA MMA CHMA DCPMA NVP HEA AAA MAA Polymer A 94 - - - - - - 6 - 600,000 -49 Polymer B - 65 8 - - 15 12 - - 800,000 -42 Polymer C 89.5 - - 4.8 - - - 5.7 - 600,000 -45 Polymer D 85.5 - - 9.1 - - - 5.5 - 600,000 -41 Polymer E 78.3 - - 16.7 - - - 5.0 - 600,000 -34 Polymer F 72.3 - - 23.1 - - - 4.6 - 600,000 -28 oligomer P - - - 96 - - - 4 - 4,000 84 oligomer Q - - 38 - 62 - - - - 4,000 146 oligomer R - 25 70 - - - - - 5 4,000 39

[Production of reinforcement film] ＜Preparation of Adhesive Composition＞ Add oligomer, crosslinking agent, light hardener (multifunctional acrylate) and photopolymerization initiator to the acrylic polymer solution, and mix them uniformly to prepare Sample 1 shown in Table 2 and Table 3 ~51 adhesive composition. As a photopolymerization initiator, "Omnirad 651" manufactured by IGM Resins was added in an amount of 0.1 part by weight with respect to 100 parts by weight of solid content of the acrylic polymer. The oligomer, the crosslinking agent, and the photocuring agent were added so as to have the compositions shown in Table 2 and Table 3. The addition amount in Table 2 and Table 3 is the addition amount (weight part of solid content) with respect to 100 weight part of base polymers. The details of the crosslinking agent and photohardening agent are as follows.

(crosslinking agent) T-C: "Tetrad C" (quaternary functional epoxy compound) manufactured by Mitsubishi Gas Chemical D110N: "Takenate D-110N" (trifunctional isocyanate compound) manufactured by Mitsui Chemicals

(light hardener) A200: "NK Ester A200" manufactured by Shin-Nakamura Chemical Industry (polyethylene glycol #200 (n=4) diacrylate; molecular weight 308, functional group equivalent weight 154 g/eq) A600: "NK Ester A600" (polyethylene glycol #600 (n=14) diacrylate; molecular weight 708, functional group equivalent weight 354 g/eq) manufactured by Shin-Nakamura Chemical Industry

＜Coating and crosslinking of adhesive solution＞ On a non-surface-treated polyethylene terephthalate film substrate ("Lumirror S10" manufactured by Toray) with a thickness of 75 μm, it is coated with a grooved roll so that the thickness after drying becomes 15 μm The above-mentioned adhesive composition. After drying at 130°C for 1 minute to remove the solvent, attach the release liner (polyethylene terephthalate film with a thickness of 25 μm and silicone release treatment on the surface) to the release surface of the adhesive Coated side. Thereafter, an aging treatment was carried out for 4 days in an atmosphere of 25° C. to progress crosslinking, and the laminated adhesive sheet was fixed on the film substrate A to obtain a reinforcing film with a release liner temporarily adhered thereon.

[Evaluate] ＜Surface Resistance of Adhesive Layer＞ The release liner was peeled off from the reinforcing film to expose the adhesive layer (before light hardening), and the surface of the adhesive layer was brought into contact with a probe ("Model 152P- 2P"), using a resistivity meter ("Model 152-1" manufactured by TREK), the surface resistance was measured under the conditions of an applied voltage of 10V and a voltage application time of 10 seconds.

＜Pressing energy＞ Using a surface-interface physical property analysis device (SAICAS DN-20 type) manufactured by Daipla Wintes, a temperature indentation test was performed in the following order (1) (2) (measurement temperature: 25°C, indentation speed: 5 μm/min ), and measure the indentation energy when the adherend is loaded with a load of 20 N.

(1) Determination of the indentation depth Use an LED (Light Emitting Diode) light source with a wavelength of 365 nm to irradiate an ultraviolet light with a cumulative light intensity of 4000 mJ/cm ² from the film substrate side of the reinforcement film to seal the adhesive layer. Light hardening. Peel and remove the release liner from the surface of the adhesive layer after light hardening, and attach it to the flat pressing head made of stainless steel. Press a spherical indenter (radius 0.5 mm) into the surface of the film substrate side of the reinforced membrane, and obtain the indentation depth H when a load of 20 N is detected by the flat indenter.

(2) Measurement of indentation energy. Peel and remove the release liner from the surface of the adhesive layer of the reinforced film, attach the adhesive layer to a glass slide, and irradiate with a cumulative light intensity of 4000 mJ/ ^cm2 from the film substrate side. The adhesive layer is photohardened by ultraviolet rays. Press the spherical indenter into the surface of the film substrate side of the reinforcement film to the depth H obtained in the above (1), and calculate the indentation energy W based on the load F(x) of the indenter in the test based on the following formula .

[number 1]

The load F(x) is the load under the pressing depth x (x is 0~H). The pressing energy W is the energy until the adhesive layer side of the reinforcing film is applied to the adherend with the reinforcing film bonded to a load of 20 N. The larger the W, the better the impact resistance.

[Determination of Adhesion of Polyimide Film] ＜Adhesion before photocuring＞ (adhesion to polyimide film without plasma treatment) A polyimide film with a thickness of 25 μm (“Upilex S” manufactured by Ube Industries) was attached to a glass plate via double-sided tape (“No. 531” manufactured by Nitto Denko) to obtain polyimide for measurement film substrate. Peel off the release liner from the surface of the reinforced film cut into a width of 25 mm x length of 100 mm, and use a hand roller to stick it to the polyimide film substrate for measurement.

After the sample was left to stand at 25°C for 30 minutes, the end of the film base material of the reinforced film was held by a chuck, and a 180° peel test was performed at a tensile speed of 300 mm/min to measure the peel strength (strength of the reinforced film) Following force).

(adhesion to plasma-treated polyimide film) While transporting the polyimide film substrate for measurement at a transport speed of 3 m/min, the plasma is applied to the surface of the polyimide film at an electrode voltage of 160 V using an atmospheric pressure plasma processor. deal with. The reinforcing film was bonded to the polyimide film after the plasma treatment using a hand roller, and the adhesive force was measured by a 180° peel test in the same manner as above.

From the obtained results, the ratio (increase rate of adhesive force caused by plasma treatment) of the adhesive force in the case of plasma treatment to the adhesive force in the case of no plasma treatment was calculated.

<Adhesion after photocuring> After bonding the reinforcing film to the polyimide film substrate for measurement (without plasma treatment), irradiate from the reinforcing film side (film substrate side) with an LED light source with a wavelength of 365 nm The adhesive layer is photohardened by accumulating ultraviolet rays with a light intensity of 4000 mJ/cm ² . Using this test sample, the adhesive force was measured by the 180° peel test in the same manner as above.

Based on the obtained results, the ratio of the adhesive force after photocuring to that before photocuring (increase rate of adhesive force with photocuring) was calculated.

The composition of the adhesive of each reinforced film (type of base polymer, type and amount of oligomer, type and amount of crosslinking agent, type and amount of light hardener) and evaluation results are shown in the table 2 and Table 3. In addition, for the sample 43 whose adhesive agent does not have photocurability, the measurement of the adhesive force after photocuring was not performed, and the measurement of the indentation energy was performed using the sample which was not photocured.

[Table 2] Sample No. Adhesive Composition evaluation result polymer Oligomer crosslinking agent light hardener Pressing energy (μJ) Surface resistance ( × 10 ¹⁰ Ω) Adhesion force (N/25 mm) Before photohardening After photohardening Adhesion rate of increase (times) type type quantity type quantity type quantity Not treated with plasma plasma treated Adhesion rate of increase (times) 1 A P 5 TC 0.5 A200 10 321 62 0.46 0.41 0.9 6.6 14.4 2 A P 5 TC 0.5 A200 20 331 59 0.23 0.29 1.2 9.9 42.5 3 A P 5 TC 0.1 A200 30 351 37 0.25 0.44 1.7 19.3 76.7 4 A P 5 TC 0.5 A200 30 341 10 0.18 0.19 1.1 17.7 101 5 A P 5 TC 0.8 A200 30 317 9 0.11 0.13 1.2 10.4 93.9 6 A P 5 TC 1.0 A200 30 315 12 0.11 0.12 1.1 8.2 74.1 7 A P 5 TC 0.5 A200 40 349 30 0.10 0.09 0.9 18.8 191 8 A P 5 TC 0.8 A200 40 325 12 0.09 0.10 1.1 15.4 170 9 A P 5 TC 1.0 A200 40 323 10 0.08 0.09 1.2 13.5 173 10 A P 1 TC 0.5 A200 50 319 5 0.08 0.09 1.2 16.7 213 11 A P 3 TC 0.5 A200 50 331 7 0.09 0.09 1.1 17.4 204 12 A P 5 TC 0.5 A200 50 354 11 0.09 0.12 1.3 19.5 219 13 A P 6 TC 0.5 A200 50 366 12 0.07 0.09 1.3 15.9 219 14 A P 8 TC 0.5 A200 50 340 13 0.09 0.13 1.4 8.1 90.3 15 A P 10 TC 0.5 A200 50 322 16 0.10 0.21 2.2 6.6 69.0 16 A P 15 TC 0.5 A200 50 305 34 0.11 0.26 2.3 2.7 23.7 17 A P 5 TC 0.8 A200 50 330 12 0.07 0.06 0.9 17.9 271 18 A P 5 TC 1.0 A200 50 328 11 0.06 0.05 0.8 13.1 214 19 A P 5 TC 1.0 A200 80 341 11 0.05 0.11 2.0 16.3 310 20 A P 5 TC 0.5 A200 A600 30 5 347 44 0.10 0.11 1.1 12.5 123 twenty one A P 5 TC 0.8 A200 A600 30 5 323 twenty four 0.09 0.08 0.9 7.0 81.3 twenty two A P 5 TC 1.0 A200 A600 30 5 321 12 0.08 0.10 1.2 5.4 66.8 twenty three A Q 1 TC 1.0 A200 30 296 29 0.12 0.12 1.0 2.9 24.6 twenty four A Q 5 TC 0.5 A200 30 317 46 0.19 0.20 1.1 9.6 51.7 25 A Q 5 TC 1.0 A200 30 310 38 0.14 0.11 0.8 4.0 29.2 26 A Q 1 TC 0.5 A200 50 314 13 0.07 0.09 1.3 3.7 51.6 27 A Q 1 TC 1.0 A200 50 309 13 0.04 0.06 1.5 2.3 53.4 28 A Q 5 TC 0.5 A200 50 330 13 0.13 0.14 1.0 6.8 51.4 29 A Q 5 TC 1.0 A200 50 323 27 0.09 0.10 1.0 4.8 51.9 30 B P 1 D110N 2.0 A200 30 281 14 0.09 0.24 2.8 10.5 122 31 B P 5 D110N 1.5 A200 30 293 39 0.13 0.41 3.2 16.7 129 32 B P 5 D110N 2.5 A200 30 283 twenty three 0.10 0.26 2.6 13.9 138 33 B P 10 D110N 2.0 A200 30 285 37 0.17 0.59 3.5 15.0 90.3 34 B P 5 D110N 2.0 A200 50 304 twenty one 0.05 0.16 3.1 12.9 259

[table 3] Sample No. Adhesive Composition evaluation result polymer Oligomer crosslinking agent light hardener Pressing energy (μJ) Surface resistance (×10 ¹⁰ Ω) Adhesion force (N/25 mm) Before photohardening After photohardening Adhesion rate of increase (times) type type quantity type quantity type quantity Not treated with plasma plasma treated Adhesion rate of increase (times) 35 C - TC 0.5 A200 30 310 39 0.08 0.20 2.6 6.8 86.9 36 C - TC 0.5 A200 50 321 29 0.03 0.14 4.4 5.6 172.1 37 D. - TC 0.5 A200 30 305 38 0.09 0.23 2.7 7.5 84.8 38 D. - TC 0.5 A200 50 309 30 0.03 0.12 3.7 5.0 155.9 39 E. - TC 0.5 A200 30 300 38 0.09 0.24 2.7 6.7 75.8 40 E. - TC 0.5 A200 50 307 28 0.02 0.13 5.2 4.5 184.1 41 f - TC 0.5 A200 30 291 36 0.08 0.23 3.0 6.5 82.1 42 f - TC 0.5 A200 50 301 29 0.02 0.11 7.1 2.9 179.2 43 A - TC 0.1 - 261 240 2.26 1.87 0.8 44 A - TC 0.5 A200 30 271 9 0.13 0.17 1.3 5.6 43.8 45 A - TC 0.5 A200 50 272 6 0.05 0.08 1.6 5.8 111.4 46 A - TC 0.8 A200 50 271 17 0.06 0.07 1.2 5.6 98.0 47 A - TC 1.0 A200 50 270 73 0.04 0.06 1 . 4 2.6 61.0 48 B - D110N 2.0 A200 30 271 56 0.07 0.23 3.2 8.9 126 49 A R 1 TC 0.5 A200 30 276 11 0.15 0.20 1.3 13.5 88.4 50 A R 5 TC 0.5 A200 30 275 13 0.20 0.25 1.2 10.9 54.5 51 A R 10 TC 0.5 A200 30 274 27 0.29 0.49 1.7 12.4 42.4

Regarding the example of using the base polymer A or B that does not contain a monomer unit having an alicyclic structure (alicyclic monomer unit), samples 43 to 48 that do not contain an oligomer in the adhesive, and samples that do not contain an aliphatic In samples 49 to 51 of the oligomer R of the cyclic monomer unit, the indentation energy was less than 280 μJ. The indentation energy of samples 1 to 34 using oligomers P and Q containing alicyclic monomer units were all 280 μJ or more, and they were excellent in impact resistance.

According to the comparison of samples 1, 2, 4, 7, and 12, it can be known that the larger the amount of light hardener present, the smaller the surface resistance of the adhesive layer and the larger the indentation energy (excellent impact resistance ) tendency. The same tendency was also observed in Samples 35 to 42 described below.

According to the comparison of samples 10 to 16, it can be known that when the amount of oligomer is not more than 6 parts by weight relative to the base polymer, there is a tendency for the indentation energy to increase as the amount of oligomer increases. However, if the amount of the oligomer is further increased, the indentation energy tends to decrease.

In Samples 23 to 29 using oligomer Q with a high glass transition temperature, it was also observed that the indentation energy tended to increase as the amounts of the photocuring agent and oligomer used increased. On the other hand, in these samples, compared with the case where oligomer P was used, the increase rate of the adhesive force by photocuring became low.

Samples 30 to 34 using polymer B and oligomer P also had large indentation energy and exhibited excellent impact resistance. On the other hand, in these samples, the initial adhesive force to the plasma-treated polyimide film became large.

Samples 35 to 42 using base polymers C, D, E, or F containing alicyclic monomer units did not contain oligomers, but similar to samples 1 to 34, the indentation energy was 280 μJ or more, Excellent impact resistance.

From these results, it can be seen that the impact resistance can be improved by including the alicyclic monomer unit in the high molecular weight component, and a reinforced film having desired adhesive properties or surface resistance can be obtained by adjusting the composition of the adhesive.

According to the comparison of samples 35, 37, 39, and 41 and the comparison of samples 36, 38, 40, and 42, it can be seen that when the amount of alicyclic monomer units in the base polymer increases, the indentation energy becomes smaller. tendency. Based on these results and the comparative results of the above-mentioned samples 10-16, it can be said that the high molecular weight component (base polymer and/or oligomer) contains alicyclic monomer units, which increases the indentation energy and impact resistance However, when the amount of alicyclic monomer units relative to the entire high molecular weight component is too large, the effect of improving impact resistance tends to be small.

The ratio of the alicyclic monomer unit (CHMA) of sample 4 and sample 35 to the total amount of monomer components constituting the whole high molecular weight component (base polymer and oligomer) is approximately the same (sample 4 is 4.6 % by weight, sample 35 is 4.8% by weight), the type and amount of crosslinking agent and light curing agent are the same, but the indentation energy of sample 4 containing acrylic oligomers containing alicyclic monomer units is large , Excellent impact resistance. The same tendency was also observed in the comparison between sample 12 and sample 36. From these results, it can be seen that the impact resistance of the reinforced film is particularly good when the adhesive composition contains an acrylic base polymer and an acrylic oligomer, and the acrylic oligomer contains an alicyclic monomer unit.

1: Membrane substrate 2: Adhesive layer 5: Peel off the liner 10: Reinforcing film 20: Adhered body

Fig. 1 is a cross-sectional view showing a laminated structure of a reinforcing film. Fig. 2 is a cross-sectional view showing a laminated structure of a reinforcing film. Fig. 3 is a cross-sectional view showing a device with a reinforcing film attached thereto.

1: Membrane substrate

2: Adhesive layer

10: Reinforcing film

Claims (13)

A reinforcing film comprising a film substrate and an adhesive layer fixedly laminated on one of the principal surfaces of the film substrate, and The adhesive layer includes a photocurable composition containing an acrylic base polymer, a photocurer, and a photopolymerization initiator, The photocurable composition includes an acrylic oligomer having a weight average molecular weight smaller than that of the acrylic base polymer, the acrylic oligomer includes monomer units having an alicyclic structure, or the acrylic base polymer includes Monomer unit of alicyclic structure. The reinforcing film according to claim 1, wherein the photocurable composition contains 0.1 to 20 parts by weight of the acrylic oligomer containing monomer units having an alicyclic structure relative to 100 parts by weight of the acrylic base polymer . The reinforced film according to claim 1 or 2, wherein the glass transition temperature of the homopolymer of the above-mentioned monomer units having an alicyclic structure is 150° C. or lower. The reinforced film according to claim 1 or 2, wherein the photocurable composition contains 3 to 100 parts by weight of the photocuring agent relative to 100 parts by weight of the base polymer. The reinforced film according to claim 1 or 2, wherein the light hardener is a multifunctional (meth)acrylate. The reinforced film according to claim 1 or 2, wherein the light hardener is a compound having a polyether chain. The reinforced film according to claim 1 or 2, wherein the surface resistance of the adhesive layer is 1×10 ¹² Ω or less. The reinforced film according to claim 1 or 2, wherein the ratio of nitrogen in the constituent elements of the acrylic base polymer is 0.1 mol% or less. The reinforcing film according to claim 1 or 2, wherein the adhesive force with the polyimide film before the above-mentioned adhesive layer is photohardened is 1 N/25 mm or less. The reinforcing film according to claim 1 or 2, the adhesive force of the plasma-treated polyimide film before the above-mentioned adhesive layer is photohardened is the adhesion of the non-plasma-treated polyimide film less than 2.5 times the force. As the reinforcement film of claim 1 or 2, the adhesive force between the above-mentioned adhesive layer and the polyimide film after light-curing the above-mentioned adhesive layer is the same as that between the above-mentioned adhesive layer and the polyimide film before light-hardening. More than 30 times the bonding force. A method of manufacturing a device, which is a method of manufacturing a device with a reinforcing film attached to its surface, and After temporarily adhering the above-mentioned adhesive layer of the reinforcing film according to any one of claims 1 to 11 to the surface of the adherend, By irradiating the adhesive layer with active light to photocure the adhesive layer, the adhesive force between the reinforcing film and the adherend is increased. A reinforcement method, which is to attach a reinforcement film to the surface of the adherend, and Temporarily sticking the above-mentioned adhesive layer of the reinforcing film according to any one of claims 1 to 11 on the surface of the adherend, By irradiating the adhesive layer with active light to photocure the adhesive layer, the adhesive force between the reinforcing film and the adherend is increased.

Images