TW202045672A - Reinforcing film method for making device and reinforcing method - Google Patents

Abstract

The reinforcing film (10) of the present invention is provided with a film substrate and an adhesive layer (2) fixedly laminated on a main surface of the film substrate. The adhesive layer contains a photocurable composition. The photocurable composition constituting the adhesive layer includes an acrylic base polymer, an acrylic oligomer, a light curing agent, and a photopolymerization initiator. The acrylic oligomer contains a carboxyl group, and the glass transition temperature is 0°C or higher.

Description

Reinforcement film, device manufacturing method and reinforcement method

The present invention relates to a reinforcing film formed by a film base material and a photocurable adhesive layer fixedly laminated. Furthermore, the present invention relates to a method of manufacturing a device with a reinforcing film attached to the surface, and a reinforcing method of fixing a laminated reinforcing film on the surface of an adherend.

On the surface of an optical device such as a display or an electronic device, an adhesive film may be attached for surface protection or impact resistance. Such an adhesive film is usually fixed with a laminated adhesive layer on the main surface of the film substrate, and is attached to the surface of the device via the adhesive layer.

In the state before the device is assembled, processed, transported, etc., the adhesive film can be temporarily adhered to the surface of the device or its constituent parts to prevent damage or breakage of the adherend. For such an adhesive film temporarily adhered for the purpose of temporary protection of the surface, it is required that it can be easily peeled off from the adherend and does not produce paste residue on the adherend.

Patent Document 1 discloses an adhesive film, which, in addition to the assembly, processing, and transportation of the device, is also used in a state of being attached to the surface of the device during use of the device. Such an adhesive film has the function of reinforcing the device due to surface protection, dispersion of the impact on the device, and rigidity to the flexible device.

When the adhesive film is attached to the adherend, there are cases of poor attachment such as the mixing of air bubbles or the offset of the attachment position. In the case of poor bonding, perform the following operations (secondary processing): peel the adhesive film from the adherend and attach another adhesive film. The adhesive film used as an engineering material is designed on the premise of peeling from the adherend, so it is easy to reprocess. On the other hand, the reinforcing film premised on permanent bonding generally does not assume peeling from the device but firmly adheres to the surface of the device, so it is difficult to perform secondary processing.

Patent Document 2 discloses an adhesive film provided with an adhesive layer designed to have low adhesiveness immediately after being bonded to an adherend, and then the force to increase over time. The adhesive that uses light or heat as the trigger to increase the adhesive force can be arbitrarily set at the time point of the adhesive force rising due to hardening after being attached to the adherend. In addition, since the adhesive force is small immediately after bonding (before the adhesive force increasing process), it is easy to peel off from the adherend, and can be used as a reinforcing film with secondary processability. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2017-132977 [Patent Document 2] International Publication No. 2015/163115

[The problem to be solved by the invention]

There are cases where the surface of an adherend such as a plasma device or the like is subjected to surface activation treatment such as plasma treatment or corona treatment for the purpose of cleaning the surface of the adherend before laminating the reinforcing film. If the reinforcing film is attached to the surface of the adherend after the surface activation treatment, the adhesive strength will increase significantly compared with the case where the adherend without the surface activation treatment is attached to the reinforcing film, and the reinforcement will be peeled off from the adherend. When the film (secondary processing) becomes difficult.

In view of this problem, the object of the present invention is to provide a method that has low initial adhesion to the adherend, excellent secondary processability, and adhesion even when the surface of the adherend is activated by plasma or the like. Reinforcement film that can firmly adhere to the adherend after the ascent treatment. [Technical means to solve the problem]

In view of the above-mentioned problems, the inventors of the present invention conducted research and found that by using a light-curing adhesive with a specific composition, the difference in initial adhesion caused by the presence or absence of surface activation treatment of the adherend is small. It also has excellent secondary processing properties to the adherend after surface activation treatment, and shows a high adhesive force to the adherend after light curing.

The reinforcing film of the present invention is provided with an adhesive layer fixedly laminated on a main surface of the film substrate. The adhesive layer contains a photocurable composition containing a base polymer, an oligomer, a photocuring agent, and a photopolymerization initiator.

As the base polymer of the adhesive layer, an acrylic polymer can be used. The acrylic base polymer may contain substantially no nitrogen atoms. Preferably, a crosslinked structure is introduced into the base polymer. For example, the base polymer contains a hydroxyl group-containing monomer and/or a carboxyl group-containing monomer as a monomer unit, and is cross-linked by bonding a cross-linking agent such as a multifunctional isocyanate compound or a multifunctional epoxy compound to these functional groups. structure.

As the oligomer, an acrylic oligomer having a weight average molecular weight of 1,000 to 30,000 and containing a carboxyl group can be used. By making the adhesive layer contain oligomers, even when the surface of the adherend is activated by plasma treatment, etc., the increase in initial adhesion to the adherend can be suppressed, and After the adhesive layer is light-cured, it tends to show a higher adhesive force to the adherend after the activation treatment.

The gel fraction of the adhesive layer (photocurable composition) may be 50% or more. When the cross-linking structure is introduced, a cross-linking accelerator can be used. As the crosslinking accelerator, for example, an organometallic compound can be used.

The light curing agent of the adhesive layer is, for example, a multifunctional (meth)acrylate. The functional group equivalent of the light hardener is preferably about 100 to 500 g/eq.

After the reinforcing film is temporarily adhered to the surface of the adherend, the adhesive layer is irradiated with active light to light-harden the adhesive layer, so that the adhesive force between the reinforcing film and the adherend increases, and is obtained on the surface of the adherend It is a device made of fixed laminated reinforcement film. When the adherend is a polyimide film, it is preferable that the adhesive force between the adhesive layer and the polyimide film be 1 N/25 mm or less before the adhesive layer is photocured (temporary adhesion state). It is also possible to perform surface activation treatments such as plasma treatment on the adherend before temporarily adhering the reinforcing film to the adherend. [Effects of Invention]

In the reinforcing film of the present invention, the adhesive layer contains a photocurable composition, and after bonding with the adherend, the adhesive layer is photocured to increase the adhesive force with the adherend. Before the adhesive layer is photocured, the adhesive force to the adherend that has been activated by plasma treatment or the like is also small, so it is easy to perform secondary processing, and exhibits a higher adhesive force after photocuring.

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

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

The spacer 5 is peeled off from the surface of the adhesive layer 2, and the exposed surface of the adhesive layer 2 is attached to the surface of the device 20, thereby attaching the reinforcing film 10 to the surface of the device 20. This state is that the adhesive layer 2 is in a state where the reinforcing film 10 (adhesive layer 2) is temporarily adhered to the device 20 before photocuring. By photocuring the adhesive layer 2, the adhesive force at the interface between the device 20 and the adhesive layer 2 is increased, and the device 20 and the reinforcing film 10 are fixed.

The so-called "fixed" refers to the state where the two layers of the laminated layer are firmly connected, and it is impossible or difficult to peel off at the interface between the two layers. The so-called "temporary adhesion" refers to a state in which the adhesive force between the two layers of the laminated layer is small and can be easily peeled off at the interface between the two layers.

In the reinforced film shown in FIG. 2, the film base material 1 and the adhesive layer 2 are fixed, and the spacer 5 is temporarily adhered to the adhesive layer 2. When the film base material 1 and the separator 5 are peeled off, peeling occurs at the interface between the adhesive layer 2 and the separator 5, and the state of the adhesive layer 2 fixed on the film base material 1 is maintained. No adhesive remains on the separator 5 after peeling.

In the pasting device shown in FIG. 3 provided with a reinforcing film 10, before the photo-curing of the adhesive layer 2, the device 20 and the adhesive layer 2 are in a temporarily bonded state. If the film base material 1 and the device 20 are peeled off, peeling occurs at the interface between the adhesive layer 2 and the device 20, and the state of the adhesive layer 2 fixed on the film base material 1 is maintained. Since no adhesive remains on the device 20, secondary processing is easy. After the adhesive layer 2 is photocured, since the adhesive force between the adhesive layer 2 and the device 20 increases, it is difficult to peel the film 1 from the device 20. If the two are peeled off, the adhesive layer 2 may cause aggregation failure .

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

The thickness of the film substrate is, for example, about 4 to 500 μm. From the viewpoint of reinforcement of the device by rigidity imparting or impact mitigation, the thickness of the film substrate 1 is preferably 12 μm or more, more preferably 30 μm or more, and even more preferably 45 μm or more. From the viewpoint of making the reinforcing film flexible and improving operability, the thickness of the film substrate 1 is preferably 300 μm or less, and more preferably 200 μm or less. 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 .

Examples of the plastic material constituting the film base material 1 include polyester resins, polyolefin resins, cyclic polyolefin resins, polyamide resins, polyimide resins, and the like. In reinforcing films for optical devices such as displays, the film substrate 1 is preferably a transparent film. In addition, when active light rays are irradiated from the side of the film base material 1 to perform photocuring of the adhesive layer 2, the film base material 1 preferably has transparency to the active light rays used for curing the adhesive layer. In terms of having both mechanical strength and transparency, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate can be used favorably. When the active light is irradiated from the side of the adherend to harden the adhesive layer, the adherend only needs to be transparent to the active light, and the film substrate 1 may be opaque to the active light.

Functional coatings such as an easy-to-adhesive layer, easy-slip layer, release layer, antistatic layer, hard coating layer, and anti-reflection layer can also be provided on the surface of the film substrate 1. Furthermore, as described above, in order to fix the film base material 1 and the adhesive layer 2, it is preferable that no release layer is provided on the surface of the film base material 1 where the adhesive layer 2 is attached.

＜Adhesive layer＞ The adhesive layer 2 fixedly laminated on the film substrate 11 includes a photocurable composition containing a base polymer, a photocuring agent, and a photopolymerization initiator. Since the adhesive layer 2 has a small adhesive force with the adhered body such as the device or device parts before photocuring, secondary processing is easy. Since the adhesive force of the adhesive layer 2 with the adherend is improved by light curing, the reinforcing film is not easy to peel off from the surface of the device when the device is used, and the bonding reliability is excellent.

When the reinforcing film is used in an optical device such as a display, the total light transmittance of the adhesive layer 2 is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The haze of the adhesive layer 2 is preferably 2% or less, more preferably 1% or less, still more preferably 0.7% or less, and particularly preferably 0.5% or less.

(Base polymer) The base polymer is the main component of the adhesive composition. From the viewpoint of setting the adhesiveness of the adhesive layer 2 before curing to an appropriate range, it is preferable to introduce a cross-linked structure into the base polymer. The type of base polymer is not particularly limited, and acrylic polymer, silicone polymer, urethane polymer, rubber polymer, etc. may be appropriately selected. Especially 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 a base polymer Preferably, more than 50% by weight of the adhesive composition is acrylic polymer.

As the acrylic polymer, those containing alkyl (meth)acrylate as a main monomer component can be used favorably. In addition, in this specification, "(meth)acrylic acid" means acrylic acid and/or methacrylic acid.

As the alkyl (meth)acrylate, an alkyl (meth)acrylate whose alkyl group has 1 to 20 carbon atoms can be preferably used. The alkyl group of the alkyl (meth)acrylate may be linear or branched. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, (meth) ) Second butyl acrylate, third butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate , Heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, (meth) Isononyl acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isodecyl (meth)acrylate Tridecyl ester, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, Heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, (meth)acrylic acid Aralkyl esters and the like.

The content of the alkyl (meth)acrylate is preferably 40% by weight or more with respect to the total amount of monomer components constituting the base polymer, more preferably 50% by weight or more, and still more preferably 55% by weight or more.

The acrylic base polymer preferably contains a monomer component having a crosslinkable functional group as a copolymer component. Due to the introduction of a cross-linked structure in the base polymer, the cohesive force increases, the adhesive force of the adhesive layer 2 increases, and the paste residue on the adherend during secondary processing tends to decrease.

Examples of the monomer having a crosslinkable functional group include a hydroxyl group-containing monomer or a carboxyl group-containing monomer. The hydroxyl group or carboxyl group of the base polymer becomes the reaction point with the crosslinking agent mentioned later. For example, when an isocyanate-based crosslinking agent is used, it is preferably a copolymerization component containing a hydroxyl-containing monomer as a base polymer. When an epoxy-based crosslinking agent is used, it is preferably a copolymer component containing a carboxyl group-containing monomer as a base polymer.

Examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. Ester, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 4-(hydroxymethyl)cyclohexylmethyl (meth)acrylate Ester etc. Examples of carboxyl group-containing monomers include (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, Butenoic acid and so on.

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 still more preferably 3 relative to the total amount of constituent monomer components. ~20% by weight. It is particularly preferable that the content of the carboxyl group-containing monomer is in the above range.

The acrylic base polymer may also contain N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperidine, vinylpyrrolidone, vinyl Nitrogen-containing monomers such as pyrrole, vinyl imidazole, vinyl azole, vinyl oxoline, N-acryloyl oxoline, N-vinyl carboxamide, N-vinyl caprolactam as constituent monomer components .

The acrylic base polymer may also contain monomer components other than the above. The acrylic base polymer may also include, for example, vinyl ester monomers, aromatic vinyl monomers, epoxy group-containing monomers, vinyl ether monomers, sulfo group-containing monomers, phosphoric acid group-containing monomers, and acid anhydride group-containing monomers. Etc. as monomer components.

The base polymer may be substantially free of 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 0. By using a base polymer that does not substantially contain nitrogen atoms, there is a tendency to suppress the increase in the adhesive force (initial adhesive force) of the adhesive layer before photocuring when the adherend is subjected to surface activation treatment.

By not containing cyano group-containing monomers, internal amide structure monomers, amide group-containing monomers, 𠰌line ring-containing monomers and other nitrogen-containing monomers as the constituent monomer components of the basic polymer, the essential The base polymer does not contain nitrogen atoms. Furthermore, when a cross-linked structure is introduced into the base polymer, it is sufficient that the polymer before the introduction of the cross-linked structure contains substantially no nitrogen atoms, and the cross-linking agent may contain nitrogen atoms. In the case where the base polymer does not substantially contain nitrogen atoms, from the viewpoint of improving the cohesiveness of the adhesive, the base polymer preferably contains a carboxyl group-containing monomer as a monomer component.

The adhesive properties of the adhesive before photocuring are easily affected by the composition and molecular weight of the base polymer. The greater the molecular weight of the base polymer, the harder the adhesive tends to become. The weight average molecular weight of the acrylic base polymer is preferably 100,000 to 5 million, more preferably 300,000 to 3 million, and still more preferably 500,000 to 2 million. Furthermore, when a cross-linked structure is introduced into the base polymer, the molecular weight of the base polymer refers to the molecular weight before the introduction of the cross-linked structure.

From the viewpoint of imparting moderate flexibility to 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. The glass transition temperature of the acrylic base polymer can 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, but may also be -80°C or higher or -70°C or higher.

By including a high Tg monomer as a constituent monomer component in the base polymer, there is a tendency that the cohesive force of the adhesive is improved, the secondary processability before photocuring is excellent, and the adhesion reliability after photocuring is higher. The so-called high Tg monomer means a monomer with a higher glass transition temperature (Tg) of the homopolymer. Monomers with a Tg of 40°C or higher for homopolymers include cyclohexyl methacrylate (Tg: 66°C), tetrahydrofurfuryl methacrylate (Tg: 60°C), and dicyclopentyl methacrylate (Tg: 175°C), dicyclopentyl acrylate (Tg: 120°C), iso-methacrylate (Tg: 173°C), iso-acrylate (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) , Acrylic acid (Tg: 106°C) and other acid monomers.

In the acrylic base polymer, the content of the monomer having a Tg of 40°C or higher in the homopolymer is preferably 1% by weight or more, more preferably 2% by weight or more, and still more preferably 3 relative to the total amount of constituent monomer components. More than weight%. 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 with a homopolymer having a Tg of 80°C or higher, and more preferably includes a homopolymer The Tg of the material is a monomer component above 100°C. In the acrylic base polymer, the content of the monomer having a Tg of 100°C or higher in the homopolymer is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and more preferably 1 % By weight or more, more preferably 2% by weight or more. On the other hand, from the viewpoint of imparting moderate flexibility to the adhesive, the content of the monomer whose Tg of the homopolymer is 40°C or higher is preferably 50% by weight or less relative to the total amount of constituent monomer components, and more preferably It is 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 point of view, the content of the monomer having a Tg of 80°C or higher in the homopolymer is preferably 30% by weight or less, more preferably 25% by weight or less, and even more preferably 20% relative to the total amount of constituent monomer components. The weight% or less may also be 15 weight% or less, 10 weight% or less, or 5 weight% or less.

By polymerizing the above-mentioned monomer components by various known methods such as solution polymerization, emulsion polymerization, and bulk polymerization, an acrylic polymer as a base polymer can be obtained. From the viewpoint of the balance of properties such as adhesive force and retention force of the adhesive, or the viewpoint of cost, the solution polymerization method is preferred. As a solvent for solution polymerization, ethyl acetate, toluene, etc. are used. The concentration of the solution is usually about 20 to 80% by weight. As the polymerization initiator used in the solution polymerization, various known ones such as azo-based and peroxide-based can be used. In order to adjust the molecular weight, a chain transfer agent can be used. The reaction temperature is usually about 50 to 80°C, and the reaction time is usually about 1 to 8 hours.

(Oligomer) The adhesive composition may contain an acrylic oligomer in addition to the acrylic base polymer. The acrylic oligomer contains alkyl (meth)acrylate as a main constituent monomer component, and is a component having a weight average molecular weight smaller than the above-mentioned acrylic base polymer. The weight molecular weight of the acrylic oligomer is about 1,000 to 30,000, and may also be 3,000 or more, 5,000 or more, or 7,000 or more, or 25,000 or less, 20,000 or less, or 15,000 or less.

As the acrylic oligomer, those containing alkyl (meth)acrylate as a main monomer component can be preferably used. Examples of monomer components constituting the acrylic oligomer include the monomers exemplified above as the monomer components constituting the acrylic base polymer. The content of the alkyl (meth)acrylate in the monomer components constituting the acrylic oligomer is preferably 40% by weight or more, and more preferably 50% by weight or more, relative to the total amount of monomer components constituting the base polymer , And more preferably 55% by weight or more. From the viewpoint of increasing the glass transition temperature of the oligomer, it is preferable to include a monomer having a Tg of 40°C or higher as a monomer component. The carboxyl group-containing oligomer contains a carboxyl group-containing monomer as a monomer component.

From the viewpoint of improving the adhesive force of the adhesive layer 2 after photocuring, the glass transition temperature of the acrylic oligomer is preferably 0°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. The glass transition temperature of acrylic oligomers may also be 40°C or higher or 50°C or higher. 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 generally 200°C or lower, and may be 160°C or lower, 140°C or lower, or 120°C or lower.

The acrylic oligomer preferably has a carboxyl group. The acid value of the acrylic oligomer is, for example, about 10 to 800 mgKOH/g, and may also be 20 to 500 mgKOH/g, 30 to 300 mgKOH/g, or 40 to 200 mgKOH/g. By making the photocurable adhesive composition contain high Tg oligomers containing carboxyl groups, even when the surface of the adherend is activated by plasma treatment or the like, the initial stage of the adherend can be suppressed Then the tendency of strength to rise. In addition, by making the photocurable adhesive composition contain a high Tg oligomer containing a carboxyl group, there is a tendency for the adhesive after photocuring to exhibit a higher adhesive force to the adherend after the activation treatment.

The acrylic oligomer and the acrylic base polymer may also contain a functional group capable of crosslinking. For example, when an epoxy-based crosslinking agent is used, if the acrylic oligomer has a carboxyl group, there is a cross-linked structure introduced by the reaction between the carboxyl group of the acrylic oligomer and the epoxy group of the crosslinking agent Happening.

The acrylic oligomer may contain substantially no nitrogen atom. The ratio of nitrogen in 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 0.

The acrylic oligomer can be obtained by polymerizing the above-mentioned monomer components by various polymerization methods. In the polymerization of acrylic oligomers, various polymerization initiators can also be used. In addition, a chain transfer agent can also be used to adjust the molecular weight. As an acrylic oligomer having a carboxyl group, commercial products such as the "ARUFON UC-3000" series manufactured by Toagosei can also be used.

The content of the acrylic oligomer in the adhesive composition is not particularly limited. From the viewpoint of adjusting the adhesive force before and after photocuring to an appropriate range, the amount of the oligomer relative to 100 parts by weight of the base polymer is preferably 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight, and further Preferably it is 0.3-5 weight part.

Among acrylic adhesives, acrylic oligomers are sometimes used as adhesion imparting agents. The amount of acrylic oligomer used as an adhesion imparting agent is often 20% by weight or more relative to 100 parts by weight of the base polymer. On the other hand, in the application of the present invention, the amount of acrylic oligomer may be small. By using a small amount of acrylic oligomer, there is a tendency for the adherend that has undergone activation treatment by plasma treatment or the like to suppress the increase in initial adhesion and increase the adhesion after photocuring. The amount of the oligomer relative to 100 parts by weight of the base polymer may be 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, or 1 part by weight or less.

(Crosslinking agent) From the viewpoint of allowing the adhesive to have a moderate cohesive force, it is preferable to introduce a crosslinked structure into the base polymer. For example, a crosslinking 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 3 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, and metal chelate compounds. Department of crosslinking agent and so on. These crosslinking agents react with functional groups such as hydroxyl or carboxyl groups introduced into the base polymer to form a crosslinked structure. In terms of high reactivity with the hydroxyl group or carboxyl group of the base polymer and easy introduction of a crosslinked structure, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred.

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-based crosslinking agent, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; cyclopentyl diisocyanate, cyclohexyl diisocyanate, isophorone diisocyanate, etc. Alicyclic isocyanates; aromatic isocyanates such as 2,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; trimethylolpropane/phenylene diisocyanate Diisocyanate trimer adduct (for example, "Coronate L" manufactured by Tosoh), trimethylolpropane/hexamethylene diisocyanate adduct (for example, "Coronate HL" manufactured by Tosoh), The trimethylolpropane adduct of xylylene diisocyanate (for example, "Takenate D110N" manufactured by Mitsui Chemicals), the isocyanurate body of hexamethylene diisocyanate (for example, "Coronate HX manufactured by Tosoh") ") and other isocyanate adducts.

As the epoxy-based crosslinking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule can be used. The epoxy-based crosslinking agent may have 3 or more or 4 or more epoxy groups in one molecule. The epoxy group of the epoxy-based crosslinking agent may be a glycidyl group. Examples of epoxy-based crosslinking agents include: N,N,N',N'-tetraglycidyl-meta-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-di Glycidyl amino methyl) cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene two Alcohol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, three Hydroxymethyl propane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tris(2-hydroxyethyl) isocyanurate triglycidyl, resorcinol diglycidyl ether , Bisphenol-S-diglycidyl ether, etc. As the epoxy-based crosslinking agent, commercially available products such as "DENACOL" manufactured by Nagase chemteX and "Tetrad X" and "Tetrad C" manufactured by Mitsubishi Gas Chemical can also be used.

Even when the base polymer does not substantially contain nitrogen atoms, the crosslinking agent may contain nitrogen atoms. For example, a cross-linked structure can be introduced into a base polymer that does not substantially contain nitrogen atoms through an isocyanate cross-linking agent. When the base polymer contains substantially no nitrogen atoms, by using a crosslinking agent that does not contain nitrogen atoms, such as an epoxy-based crosslinking agent, it is possible to suppress the increase in initial adhesion caused by surface activation treatment such as plasma treatment The tendency.

The amount of the crosslinking agent used may be appropriately adjusted according to the composition or molecular weight of the base polymer. The amount of the crosslinking agent used is about 0.01 to 10 parts by weight relative to 100 parts by weight of the base polymer, preferably 0.1 to 7 parts by weight, more preferably 0.2 to 6 parts by weight, and still more preferably 0.3 to 5 parts by weight. In addition, the amount (parts by weight) of the crosslinking agent used relative to 100 parts by weight of the base polymer divided by the functional group equivalent (g/eq) of the crosslinking agent is preferably 0.00015 to 0.11, more preferably 0.001 to 0.077 , More preferably 0.003 to 0.055, particularly preferably 0.0045 to 0.044. By making the use amount of crosslinking agent larger than the ordinary acrylic optical transparent adhesive for permanent bonding, the adhesive has moderate hardness, and the paste residue on the adherend during secondary processing is reduced. , The tendency of secondary processing to improve.

(Crosslinking accelerator) In addition to the crosslinking agent, the adhesive composition may also include a crosslinking accelerator. By using a cross-linking accelerator, the cross-linking reaction (introduction of the cross-linked structure to the base polymer) can proceed efficiently. In addition, by using a cross-linking accelerator to introduce a cross-linked structure into the base polymer, there is a tendency for the adherend whose surface has been activated by the adhesive layer of the reinforcing film to exhibit lower initial adhesion.

As the crosslinking accelerator, organometallic compounds such as organometallic complexes (chelates), compounds of metals and alkoxy groups, and compounds of metals and alkoxy groups; and tertiary amines. In particular, from the viewpoint of suppressing the progress of the crosslinking reaction in a solution state at room temperature and ensuring the pot life of the adhesive composition, an organometallic compound is preferred. In addition, in terms of easily introducing a uniform crosslinking structure throughout the entire thickness direction of the adhesive layer, the crosslinking accelerator is preferably an organometallic compound that is liquid at room temperature.

Examples of the metal of the organometallic compound include iron, tin, aluminum, zirconium, zinc, titanium, lead, cobalt, zinc, and the like.

Examples of iron-based crosslinking accelerators include tris(acetone) iron, tris(hexane-2,4-diketone) iron, tris(heptane-2,4-diketone) iron, tris(heptane) iron Alkane-3,5-dione)iron, tris(5-methylhexane-2,4-dione)iron, tris(octane-2,4-dione)iron, tris(6-methylheptane) Alkane-2,4-dione)iron, tris(2,6-dimethylheptane-3,5-dione)iron, tris(nonane-2,4-dione)iron, tris(nonane) -4,6-diketone) iron, tris(2,2,6,6-tetramethylheptane-3,5-dione) iron, tris(tridecane-6,8-dione) iron, Tris(1-phenylbutane-1,3-dione) iron, tris(hexafluoroacetone acetone) iron, tris(ethyl acetylacetate) iron, tris(n-propyl acetylacetate) iron, tris (Isopropyl Acetate) Iron, Tris(n-Butyl Acetate) Iron, Tris(Second Butyl Acetate) Iron, Tris(Tterbutyl Acetate) Iron, Tris(Acetyl Acetate) Methyl ester) iron, tris(ethyl acrylate) iron, tris(n-propyl propyl acetate) iron, tris(isopropyl propyl acetate) iron, tris(n-butyl propyl acetate) iron, tris( (2-butyl acrylate) iron, tris(tert-butyl acrylate) iron, tris(benzyl acetylacetate) iron, tris(dimethyl malonate) iron, tris(diethyl malonate) Ester) iron, iron trimethoxide, iron triethanol, iron triisopropoxide, etc.

Examples of tin-based crosslinking accelerators include: dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin maleate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, methoxide Tributyl tin, tributyl tin acetate, triethyl tin ethoxide, tributyl tin ethoxide, dioctyl tin oxide, dioctyl tin dilaurate, tributyl tin chloride, tributyl tin trichloroacetate, 2-ethylhexanoic acid Tin etc.

Examples of aluminum-based crosslinking accelerators include: aluminum diisopropoxide, aluminum diisopropoxide, aluminum dibutoxide, aluminum isopropoxide, aluminum ethoxide, ethyl acetate, aluminum diisopropoxide, and triacetate. Aluminum ethyl acetate, Alkyl Acetate Acetate Aluminum Diisopropoxide, Monoacetone Bis(Acetate Acetate) Aluminum, Triacetone Aluminum, etc.

As the zirconium-based crosslinking accelerator, zirconium tetraacetone acetonate, zirconium monoacetone acetonate, zirconium tributoxide monoacetone, zirconium naphthenate, zirconium propoxide, zirconium butoxide, etc. may be mentioned.

Examples of the zinc-based crosslinking accelerator include zinc naphthenate, zinc 2-ethylhexanoate, and the like.

As the titanium-based crosslinking accelerator, dibutyl titanium dichloride, tetrabutyl titanate, tetraisopropyl titanate, tetraoctyl titanate, titanium butoxide trichloride, titanium acetone, Titanium tetraacetylacetone, titanium ethyl acetate, titanium ammonium lactate, titanium triethanolamine, titanium diisopropanol diacetone, titanium isostearate, titanium diethanolamine, titanium ethylaminoethyl ethoxide Wait.

Examples of lead-based crosslinking accelerators include lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate.

Examples of cobalt-based crosslinking accelerators include cobalt 2-ethylhexanoate and cobalt benzoate.

The use amount of the crosslinking accelerator may be appropriately adjusted according to the type and amount of the crosslinking agent, and the type of crosslinking accelerator. The usage amount of the crosslinking accelerator is generally about 0.001 to 2 parts by weight relative to 100 parts by weight of the base polymer.

When a crosslinking accelerator is used for the epoxy-based crosslinking agent, the amount of the crosslinking accelerator used is preferably 0.01 to 2.0 parts by weight relative to 100 parts by weight of the base polymer. For the epoxy-based crosslinking agent, it is preferable to use a non-tin-based organic metal as the crosslinking accelerator. When a crosslinking accelerator is used for the isocyanate-based crosslinking agent, the amount of the crosslinking accelerator used is preferably 0.001 to 0.1 parts by weight.

The adhesive composition may also include a crosslinking retarder in addition to the crosslinking accelerator. By adding a crosslinking retarder, the progress of the crosslinking reaction in a solution state at room temperature can be inhibited, thereby prolonging the pot life of the adhesive composition. As the crosslinking retarder, β-ketoesters such as methyl acetylacetate, ethyl acetylacetate, octyl acetylacetate, oleyl acetylacetate, lauryl acetylacetate, and stearyl acetylacetate; Β-diketones such as acetone, 2,4-hexanedione, and benzylacetone; alcohols such as tertiary butanol. Among them, β-diketone is preferred, and acetone is particularly preferred. The amount of the crosslinking retarder used is about 0.1-30 parts by weight relative to 100 parts by weight of the total adhesive composition, preferably 25 parts by weight or less, and more preferably 20 parts by weight or less.

(Light Hardener) The adhesive composition constituting the adhesive layer 2 contains a light hardener in addition to the base polymer. If the adhesive layer 2 containing the photocurable adhesive composition is photocured after being bonded to the adherend, the adhesive force with the adherend is improved.

The light curing agent has two or more polymerizable functional groups in one molecule. As the polymerizable functional group, those having polymerizability based on photoradical reaction are preferred, and as the light curing agent, a compound having two or more ethylenically unsaturated bonds in one molecule is preferred. In addition, the light hardener is preferably a compound exhibiting compatibility with the base polymer. In terms of exhibiting moderate compatibility with the base polymer, the light hardener is preferably one that is liquid at room temperature. By dissolving the light hardener and the base polymer and uniformly dispersing in the composition, the contact area with the adherend can be ensured, and the adhesive layer 2 with higher transparency can be formed. In addition, by making the base polymer and the light hardening agent have moderate compatibility, it is easy to uniformly introduce the cross-linked structure obtained by the light hardening agent into the adhesive layer 2 after light hardening, so as to exist and be adhered The tendency of the adhesion of the body to rise appropriately.

The compatibility of the base polymer and the light hardener is mainly affected by the structure of the compound. The structure and compatibility of the compound can be evaluated by, for example, the Hansen solubility parameter. The smaller the difference between the solubility parameter of the base polymer and the light hardener, the higher the compatibility.

In terms of high compatibility with the acrylic base polymer, it is preferable to use a polyfunctional (meth)acrylate as a light hardener. Examples of polyfunctional (meth)acrylates include polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, Bisphenol A ethylene oxide modified di(meth)acrylate, bisphenol A propylene oxide modified di(meth)acrylate, alkanediol di(meth)acrylate, tricyclodecane dimethanol Di(meth)acrylate, ethoxylated isocyanuric acid tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(methyl) ) Acrylate, di-trimethylolpropane tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol poly(meth)acrylate, two Pentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerol di(meth)acrylate, (meth)acrylate urethane, epoxy (meth)acrylate, Butadiene (meth)acrylate, isoprene (meth)acrylate, etc. Among them, in terms of excellent compatibility with acrylic base polymers, polyethylene glycol di(meth)acrylate or polypropylene glycol di(meth)acrylate is preferred, and poly(meth)acrylate is particularly preferred. Ethylene glycol di(meth)acrylate. Two or more types of light hardeners may be used in combination.

The compatibility of the base polymer and the light hardener is also affected by the molecular weight of the compound. There is a tendency that the lower the molecular weight of the photocurable compound, the higher the compatibility with the base polymer. From the viewpoint of compatibility with the base polymer, the molecular weight of the light hardener is preferably 1500 or less, more preferably 1000 or less, still more preferably 500 or less, and particularly preferably 400 or less.

From the viewpoint of high compatibility with the base polymer and improvement of the adhesive force after light curing, the functional group equivalent (g/eq) of the light curing agent is preferably 500 or less, more preferably 400 or less, and more Preferably it is 300 or less, particularly preferably 200 or less. 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 increase and the adhesiveness may decrease. Therefore, the functional group equivalent of the light hardener is preferably 80 or more, more preferably 100 or more, and still more preferably 130 or more.

In the combination of acrylic base polymer and multifunctional acrylate light hardening agent, when the functional group equivalent of the light hardening agent is small, the interaction between the base polymer and the light hardening agent is stronger, and the initial adhesive force increases , And cause the reduction of secondary processing. From the viewpoint of keeping the adhesive force between the adhesive layer 2 before photocuring and the adherend in an appropriate range, it is also preferable that the functional group equivalent of the photocuring agent is within the above range.

The content of the light hardener in the adhesive composition is preferably 10-50 parts by weight relative to 100 parts by weight of the base polymer. By setting the blending amount of the light curing agent within the above range, the adhesiveness of the adhesive layer after light curing and the adherend can be adjusted to an appropriate range. The content of the light hardener is more preferably 15 to 45 parts by weight, and still more preferably 20 to 40 parts by weight relative to 100 parts by weight of the base polymer.

(Photopolymerization initiator) The photopolymerization initiator is irradiated with active light to generate active species to promote the hardening reaction of the light hardener. As the photopolymerization initiator, a photocation initiator (photoacid generator), a photoradical initiator, a photoanion initiator (photobase generator), etc. can be used according to the kind of the photohardener or the like. When using an ethylenically unsaturated compound such as a polyfunctional acrylate as a light hardening agent, it is preferable to use a photo radical 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 free radical transfer from the photo-radical initiator to the photohardener. As the photo-radical initiator (photo-radical generator), it is preferable to generate free radicals by irradiation of visible light or ultraviolet light with a wavelength shorter than 450 nm, and examples include hydroxy ketones and benzyl dimethyl ketals. Ketones, aminoketones, phosphine oxides, benzophenones, trichloromethyl-containing three 𠯤 derivatives, etc. The photo-radical initiator may be used alone or in combination of two or more kinds.

When transparency is required for the adhesive layer 2, the photopolymerization initiator is preferably less sensitive to light with a wavelength longer than 400 nm (visible light), for example, the absorbance coefficient at a wavelength of 405 nm can be used well 1×10 ² [mLg ^-1 cm ^-1 ] or less photopolymerization initiator.

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 10 parts by weight, more preferably 0.05 to 7 parts by weight, and still more preferably 0.1 to 5 parts by weight relative to 100 parts by weight of the light hardener.

(Other additives) In addition to the components exemplified above, the adhesive layer may also contain silane coupling agents, adhesiveness imparting agents, plasticizers, softeners, antioxidants, anti-deterioration agents, fillers, and coloring within the range that does not impair the characteristics of the present invention. Additives such as agents, ultraviolet absorbers, surfactants, and antistatic agents.

[Production of Reinforcing Film] The photocurable adhesive layer 2 is laminated on the film substrate 1 to obtain a reinforced film. The adhesive layer 2 can be directly formed on the film substrate 1, or an adhesive layer formed in a sheet form on another substrate can be transferred to the film substrate 1.

By applying the above-mentioned adhesive composition using roll coating, touch roll coating, gravure coating, reverse coating, roll brushing, spraying, dipping roll coating, bar coating, blade coating, gas Knife coating, curtain coating, lip coating, die nozzle coating, etc. are coated on the substrate, and the solvent is dried and removed as needed to form an adhesive layer. As the drying method, an appropriate method can be adopted as appropriate. The heating and drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and still 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 still more preferably 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 greater the thickness of the adhesive layer 2 is, the more the adhesion with the adherend will increase. On the other hand, when the thickness of the adhesive layer 2 is too large, the fluidity before photocuring may be high, and handling may become difficult. Therefore, the thickness of the adhesive layer 2 is preferably 5-100 μm, more preferably 8-50 μm, still more preferably 10-40 μm, and particularly preferably 13-30 μm.

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

The introduction of a cross-linked structure into the base polymer increases the gel fraction. The higher the gel fraction, the harder the adhesive, and when the reinforcing film is peeled from the adherend due to secondary processing, etc., the tendency of the paste to remain on the adherend can be suppressed. The gel fraction of the adhesive layer 2 before photocuring is preferably 30% or more, more preferably 50% or more, still more preferably 60% or more, and particularly preferably 65% or more. The gel fraction of the adhesive layer 2 before light hardening can also be 70% or more or 75% or more.

Since the adhesive contains an unreacted light hardening agent, the gel fraction of the adhesive layer 2 before light hardening is generally below 90%. If the gel fraction of the adhesive layer 2 before photocuring is too large, the gripping force to the adherend may decrease, and the initial adhesive force may become insufficient. Therefore, the gel fraction of the adhesive layer 2 before photocuring is preferably 85% or less, and more preferably 80% or less.

The gel fraction can be determined as the insoluble matter in a solvent such as ethyl acetate. Specifically, as the insoluble matter after immersing the adhesive layer in ethyl acetate at 23°C for 7 days compared to the test before immersion The weight fraction of the sample (unit: weight %) is calculated. Generally speaking, the gel fraction of a polymer is equal to the degree of crosslinking. The more crosslinked parts in the polymer, the greater the gel fraction. Therefore, the more the amount of crosslinking agent used (the content of crosslinkable functional groups), the greater the gel fraction tends to be. In addition, by using a crosslinking accelerator, the amount of unreacted functional groups of the crosslinking agent is reduced, so there is a tendency for the gel fraction to increase. In the adhesive layer 2 before photocuring, since the photocuring agent is in an unreacted state, the greater the amount of the photocuring agent, the smaller the gel fraction.

After the crosslinking structure is introduced into the polymer by the crosslinking agent, the light hardener also maintains an unreacted state. Therefore, a photo-curable adhesive layer 2 containing a base polymer and a photo-curing agent is formed. When the adhesive layer 2 is formed on the film substrate 1, it is preferable to attach a spacer 5 to the adhesive layer 2 for the purpose of protecting the adhesive layer 2 or the like. The adhesive layer 2 can also be cross-linked after the spacer 5 is attached.

In the case of forming the adhesive layer 2 on another substrate, a reinforcing film is obtained by transferring the adhesive layer 2 to the film substrate 1 after drying the solvent. The base material used in the formation of the adhesive layer can also be directly used as the spacer 5.

As the separator 5, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films can be suitably used. The thickness of the spacer is usually 3 to 200 μm, preferably about 10 to 100 μm. Preferably, the contact surface between the spacer 5 and the adhesive layer 2 is implemented by a silicone-based, fluorine-based, long-chain alkyl-based, or fatty amide-based mold release agent, or silica powder, etc. The demoulding treatment. By performing a mold release treatment on the surface of the separator 5, when the film base material 1 and the separator 5 are peeled off, it can be maintained at the interface between the adhesive layer 2 and the separator 5 to be peeled and fixed on the film base material 1. The state of the adhesive layer 2.

[Use of Reinforcing Film] The reinforcing film of the present invention is used by sticking to the device or device constituent parts. The adherend to which the reinforcing film is attached is not particularly limited, and various electronic devices, optical devices, and their constituent parts can be cited. The reinforcing film can be attached to the entire surface of the adherend, or can be selectively attached only to the part that needs reinforcement. In addition, after the reinforcing film is attached to the entire surface of the adherend, the reinforcing film at the part that does not need to be reinforced can be cut, and the reinforcing film can be peeled off. As long as it is before the adhesive is photocured, the reinforcing film is temporarily stuck to the surface of the adherend, so the reinforcing film can be easily peeled off from the surface of the adherend.

Since appropriate rigidity is imparted by laminating the reinforcing film, the effect of improving the operability and preventing damage can be expected. In the manufacturing steps of the device, when the reinforcing film is attached to the semi-finished product, the reinforcing film can be attached to the semi-finished product that is larger than the size of the product before being cut. The reinforcing film can also be attached to the mother roll of the device manufactured by the roll to roll process in roll to roll.

＜Characteristics of the adhesive layer before light curing＞ In the reinforcing film 10, the adhesive layer 2 is fixed to the film base material 1, and after being bonded to the adherend and before light curing, the adhesive force to the adherend is small. Therefore, before photocuring, the reinforcing film can be easily peeled from the adherend, and the secondary workability is excellent. In addition, processing such as cutting the reinforcing film and removing the reinforcing film on a part of the surface of the adherend before photocuring can also be easily performed.

(Adhesion) From the standpoint of making it easy to peel from the adherend and preventing the paste remaining on the adherend after peeling off the reinforcing film, the adhesive layer 2 before photocuring and the adherend have a higher adhesive strength (initial adhesion) It is preferably 1 N/25 mm or less, more preferably 0.7 N/25 mm or less, and still more preferably 0.5 N/25 mm or less. The adhesive force between the adhesive layer 2 and the adherend before light hardening can also be 0.4 N/25 mm or less, 0.3 N/25 mm or less, or 0.2 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 , And more preferably 0.03 N/25 mm or more. The initial adhesive force can also be above 0.05 N/25 mm, above 0.07 N/25 mm, or above 0.1 N/25 mm.

The reinforcing film preferably has an adhesive force to the polyimide film in the state before the adhesive layer is photocured within the above range. In flexible display panels, flexible printed wiring boards (FPC), devices that integrate display panels and wiring boards, etc., flexible substrate materials are used. From the viewpoint of heat resistance or dimensional stability, Polyimide films are generally used. The adhesive layer has the above-mentioned adhesive force to the polyimide film as the substrate, and the reinforcing film is easily peeled off before the adhesive is photocured, and the adhesion reliability after photocuring is excellent.

It is also possible to activate the adherends such as the polyimide film on the surface of the device for the purpose of cleaning before attaching the reinforcing film. Examples of surface activation treatment include plasma treatment, corona treatment, glow discharge treatment, and the like. Especially in terms of processing under atmospheric pressure and high activation effect, atmospheric pressure slurry processing is preferable.

If the surface activation treatment is performed on the adherend, the adhesion between the adhesive layer 2 before photocuring and the adherend tends to be higher than when the surface activation treatment is not performed. If the adhesive force between the adhesive layer and the adherend before photocuring is too large, secondary processing may become difficult. Therefore, the adhesive force of the adherend that has undergone surface activation treatment and the adhesive layer before photocuring is preferably less than twice the adhesive force of the adherend that has not undergone surface activation treatment and the adhesive layer before photocuring. , More preferably 1.5 times or less, still more preferably 1.4 times or less, and may also be 1.3 times or less or 1.2 times or less.

In the present invention, by making the adhesive contain a high Tg oligomer containing a carboxyl group in addition to the base polymer, even when the adherend is subjected to surface activation treatment, the adhesive layer before photocuring can be The adhesive force (initial adhesive force) is suppressed low. Therefore, even when surface activation treatment is performed on an adherend such as a polyimide film, secondary processing is easy as in the case where the surface activation treatment is not performed. Furthermore, by making the adhesive contain a high Tg oligomer containing a carboxyl group, the adhesive after photocuring tends to exhibit higher adhesion to the adherend subjected to the surface activation treatment, and the bonding reliability is excellent.

By adding oligomers, the increase in the initial adhesion to the surface-activated adherend and the increase in the adhesion after photocuring is not certain. It is presumed to be related to the following situation: By adding a small amount of oligomers It will not greatly change the overall characteristics of the adhesive, but the characteristics of the interface with the adherend will change.

(Storage modulus) The adhesive layer 2 preferably has a shear storage modulus G′ _i at 25° C. before photocuring of 1×10 ⁴ to 1.2×10 ⁵ Pa. Shear storage modulus (hereinafter, only described as "storage modulus") is based on the method described in JIS K7244-1 "Plastics-Test Methods for Dynamic Mechanical Properties" at a frequency of 1 Hz at- The range of 50 to 150°C is calculated as the value at a specific temperature when the temperature rise rate is 5°C/min.

In a substance that exhibits viscoelasticity like an adhesive, the storage modulus G'is used as an indicator of the degree of hardness. The storage modulus of the adhesive layer has a higher correlation with the cohesive force. The higher the cohesive force of the adhesive, the greater the gripping force of the adherend. As long as the storage modulus of the adhesive layer 2 before light hardening is 1×10 ⁴ Pa or more, the adhesive has sufficient hardness and cohesive power, so it is not easy to produce on the adherend when the reinforcing film is peeled from the adherend Paste remains. In addition, when the storage modulus of the adhesive layer 2 is large, the adhesive can be prevented from overflowing from the end surface of the reinforcing film. As long as the storage modulus of the adhesive layer 2 before light hardening is 1.2×10 ⁵ Pa or less, it will be easy to peel off at the interface between the adhesive layer 2 and the adherend, and it is not easy to produce adhesion during secondary processing. The agglomeration of the agent layer is broken or the paste remains on the surface of the adherend.

Secondary processing to improve the reinforcing of film to suppress the residual paste in view of the adhesion of the body in terms of secondary processing, storage under the adhesive layer of the front light 25 2 deg.] C and cured modulus G _'i better It is 3×10 ⁴ to 1×10 ⁵ Pa, more preferably 4×10 ⁴ to 9.5×10 ⁴ Pa.

＜Light hardening of adhesive layer＞ After bonding the reinforcing film to the adherend, the adhesive layer 2 is irradiated with active light to light-harden the adhesive layer. Examples of active rays include ultraviolet rays, visible rays, infrared rays, X-rays, α rays, β rays, and γ rays. In terms of being able to suppress the hardening of the adhesive layer in the storage state and being easy to harden, the active light is preferably ultraviolet light. The irradiation intensity or irradiation time of the active light can be appropriately set according to the composition or thickness of the adhesive layer. The active light irradiation of the adhesive layer 2 can be carried out from either side of the film substrate 1 side and the adherend side, or active light irradiation can be carried out from both sides.

＜Characteristics of the adhesive layer after light curing＞ (Adhesion) From the viewpoint of the bonding reliability of the device in practical use, the bonding force between the adhesive layer 2 and the adherend after light curing is preferably 2 N/25 mm or more, more preferably 3 N/25 mm or more, and then Preferably it is 5 N/25 mm or more. The adhesive force between the reinforcing film and the adherend after light-curing the adhesive layer can also 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, 15 N /25 mm or more, or 20 N/25 mm or more. The reinforcing film is preferably the adhesive layer after photocuring that has an adhesive force in the above range to the polyimide film. The adhesive force between the adhesive layer 2 and the adherend after light curing is preferably at least 5 times, and more preferably at least 10 times the adhesive force of the adhesive layer 2 and the adherend before light curing. The adhesive force between the adhesive layer and the adherend after light hardening can also be 20 times, 50 times, 80 times, 100 times, 120 times that of the adhesive layer and adherend before light hardening. Or more than 140 times.

As described above, by making the base polymer of the adhesive free of nitrogen atoms, there is a tendency to suppress the increase in the initial adhesive force caused by the surface activation treatment of the adherend. On the other hand, when the surface activation treatment is performed on the adherend, compared with the case where the surface activation treatment of the adherend is not performed, there is an adhesive force between the adhesive layer 2 and the adherend after light curing The tendency to become bigger. In particular, when the adhesive composition contains a high Tg oligomer containing a carboxyl group, there is a tendency that the initial adhesion increase due to the surface activation treatment can be suppressed, and the adhesive force after the photocuring of the adhesive tends to increase. That is, when using a reinforcing film with an adhesive layer with a specific composition, by performing surface activation treatment such as plasma treatment on the adherend, the increase in initial adhesion is suppressed, and the secondary workability is ensured. After light curing, a higher adhesive force will be realized, and a device with excellent adhesive reliability of the reinforcing film can be obtained.

(Storage modulus) The adhesive layer 2 preferably has a storage modulus G′ _f at 25° C. after light curing of 1.0×10 ⁵ Pa or more. As long as the storage modulus of the adhesive layer 2 after light curing is 1.0×10 ⁵ Pa or more, the adhesion force with the adherend increases as the cohesive force increases, and higher bonding reliability can be obtained. On the other hand, when the storage modulus is too large, the adhesive is difficult to wet and expand, and the contact area with the adherend becomes smaller. In addition, the stress dispersibility of the adhesive is reduced, so there is a tendency for the peeling force to easily propagate to the bonding interface and the adhesive force with the adherend to decrease. Therefore, the storage modulus G′ _f at 25° C. of the adhesive layer 2 after light curing is preferably 2×10 ⁶ Pa or less. To improve the reinforcing layer after the adhesive was light cured film in terms of the reliability point of view and then, G _'f is more preferably ^{1.1 × 10 5 ~ 1.2 × 10} 6 Pa, and further preferably 1.2 × 10 ⁵ ~ 1 × 10 ⁶ Pa.

The ratio of the storage modulus _G'f /G' _i at 25° C. before and after light curing of the adhesive layer 2 is preferably 2 or more. As long as the G 'is _F G' _i of 2 times or more, by increasing the photohardenable of G 'becomes larger, secondary processability can be both before and after photohardening of the photohardenable Next reliability. _G'f /G' _i is more preferably 4 or more, still more preferably 8 or more, and particularly preferably 10 or more. G _'f / G' of the upper limit of _i is not particularly limited, to G _'f / G' of the case when _i is too large, easily lead to the front of the photo-curing by G 'is small and the initial cause of the failure and then, after the photohardening or because The G'is too large and the reliability of the connection is reduced. Therefore, _G'f /G' _{i is} preferably 100 or less, more preferably 40 or less, still more preferably 30 or less, and particularly preferably 25 or less.

The adherend after the reinforcement film is attached may be subjected to autoclave treatment for the purpose of enhancing the affinity of the laminate interface of a plurality of laminate members, or heat treatment such as thermocompression bonding for bonding circuit members. When performing such heat treatment, it is preferable that the adhesive between the reinforcing film and the adherend does not flow from the end surface.

From the viewpoint of suppressing the overflow of the adhesive during high-temperature heating, the storage modulus at 100°C of the adhesive layer 2 after photohardening is preferably 5×10 ⁴ Pa or more, more preferably 8×10 ⁴ Pa or more , And more preferably 1×10 ⁵ Pa or more. From the viewpoints of preventing the overflow of the adhesive during heating and preventing the decrease of the adhesive force during heating, the storage modulus at 100°C of the adhesive layer 2 after photohardening is preferably that of the storage modulus at 50°C 60% or more, more preferably 65% or more, still more preferably 70% or more, and particularly preferably 75% or more.

By laminating the reinforcing film, moderate rigidity can be given to the semi-finished product as the adherend, and the stress can be relieved and dispersed. Therefore, various defects that may occur in the manufacturing step can be suppressed, production efficiency can be improved, and yield can be improved. In addition, since the reinforcing film is easily peeled from the adherend before the adhesive layer is photocured even when the adherend has been subjected to surface activation treatment, it is also easy to cause build-up or poor bonding. Easy secondary processing. After light-curing the adhesive layer, it exhibits a high adhesive force to the adherend, the reinforcing film is not easy to peel off the surface of the device, and the bonding reliability is excellent. [Example]

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

[Example 1] ＜polymerization of basic polymer＞ Put 95 parts by weight of butyl acrylate (BA) as monomers and 5 parts by weight of acrylic acid (AA) as monomers into a reaction vessel equipped with a thermometer, agitator, reflux condenser and nitrogen introduction tube, and azobis as a thermal polymerization initiator. 0.2 parts by weight of isobutyronitrile (AIBN) and 233 parts by weight of ethyl acetate as a solvent were blown with nitrogen gas, and nitrogen replacement was performed for about 1 hour while stirring. Thereafter, it was heated to 60°C and reacted for 7 hours to obtain a solution of acrylic polymer with a weight average molecular weight of 600,000.

＜Preparation of adhesive composition＞ Add carboxyl-containing acrylic oligomer to the solution of acrylic polymer ("ARUFON UC-3000" manufactured by Toagosei; weight average molecular weight: 10,000, glass transition temperature: 65°C, acid value: 74 mgKOH/g) 1 part by weight of a 4-functional epoxy compound ("Tetrad C" manufactured by Mitsubishi Gas Chemical) as a crosslinking agent and 0.5 part by weight of a multifunctional acrylic monomer "NK Ester A200" manufactured by Shinnakamura Chemical Industry Co., Ltd. ( Polyethylene glycol #200 (n=4) diacrylate; molecular weight 308, functional group equivalent 154 g/eq) 30 parts by weight, and photopolymerization initiator ("Irgacure 651" manufactured by BASF) 0.1 parts by weight, prepared Adhesive composition.

＜Coating and crosslinking of adhesive composition＞ The adhesive composition was coated on a polyethylene terephthalate film with a thickness of 75 μm (“Lumirror S10” manufactured by Toray) without surface treatment so that the thickness after drying became 25 μm using a grooved roller. Dry at 130°C for 1 minute to remove the solvent. After that, paste the separator (25 μm thick polyethylene terephthalate film with silicone release treatment on the surface) on the coated surface of the adhesive. The demoulding surface. Thereafter, an aging treatment was carried out for 4 days in an environment of 25° C., and cross-linking was performed to obtain a reinforcing film with a photocurable adhesive sheet fixed on the film substrate and a separator temporarily adhered thereon.

[Examples 2, 3] In the preparation of the adhesive composition, the addition amount of the acrylic oligomer was changed as shown in Table 1. Except for this, the reinforcing film was produced in the same manner as in Example 1.

[Example 4] In the preparation of the adhesive composition, acrylic oligomer, crosslinking agent, multifunctional acrylic monomer, and photopolymerization initiator are added to the solution of acrylic polymer, and added as a crosslinking accelerator 0.2 parts by weight of tetrazirconium acetone (manufactured by Tokyo Chemical Industry). In addition, 30 parts by weight of "NK ESTER A200" as a multifunctional acrylic monomer was added, and "NK ESTER A600" (polyethylene glycol #600 (n=4) diacrylate made by Shinnakamura Chemical Co., Ltd.; molecular weight 708) was added. , Functional group equivalent 354 g/eq) 5 parts by weight. Except for these changes, a reinforcing film was produced in the same manner as in Example 1.

[Comparative Example 1] In the preparation of the adhesive composition, the acrylic oligomer was not added, and the reinforcing film was produced in the same manner as in Example 1 except that the acrylic oligomer was not added.

[Comparative Examples 2～4] In the preparation of the adhesive composition, the type of acrylic oligomer was changed as shown in Table 1. Except for this, a reinforcing film was produced in the same manner as in Example 4. "UC-3510" used in Comparative Example 2 is a liquid carboxyl group-containing acrylic oligomer ("ARUFON UC-3510" manufactured by Toagosei, weight average molecular weight: 2000, glass transition temperature: -50°C, acid Value: 70 mgKOH/g). "UP-1190" used in Comparative Example 3 is a liquid acrylic oligomer without carboxyl group ("ARUFON UP-1190" manufactured by Toagosei, weight average molecular weight: 3000, glass transition temperature: -77°C) . The "oligomer A" used in Comparative Example 4 is an acrylic oligomer with a weight average molecular weight of 5100 and a glass transition temperature of 144°C obtained by the following production example.

＜Production example of oligomer＞ Mix 60 parts by weight of dicyclopentyl methacrylate (DCPMA), 40 parts by weight of methyl methacrylate (MMA), 3.5 parts by weight of α-thioglycerol as a chain transfer agent, and 100 parts by weight of toluene as a polymerization solvent. , Stir at 70°C for 1 hour under a nitrogen atmosphere. Then, 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added and reacted at 70°C for 2 hours, and then heated to 80°C for 2 hours. After that, the reaction liquid was heated to 130° C., toluene, chain transfer agent, and unreacted monomer were dried and removed, and a solid oligomer A was obtained.

[Measurement of the adhesion of polyimide film] ＜Adhesive force before light hardening＞ A polyimide film with a thickness of 12.5 μm ("Kapton 50EN" manufactured by DU PONT-TORAY) is attached to a glass plate via a double-sided tape ("No.531" manufactured by Nitto Denko) to obtain a polyimide for measurement Film substrate. The separator was peeled off from the surface of the reinforcing film with a width of 25 mm × a length of 100 mm, and was attached to the polyimide film substrate for measurement using a hand roller to prepare a sample for adhesion measurement (no plasma treatment) .

While conveying the polyimide substrate for measurement at a conveying speed of 3 m/min, the surface of the polyimide film was subjected to plasma treatment using an atmospheric-pressure plasma processor at an electrode voltage of 160 V. The reinforcing film was attached to the polyimide film substrate for measurement after the plasma treatment using a hand roller to prepare a sample for adhesion measurement (with plasma treatment).

Using these test samples, the end of the polyethylene terephthalate film of the reinforced film was held by a chuck, and the 180° peel test of the reinforced film was performed at a tensile speed of 300 mm/min, and the peel strength was measured. Based on the obtained results, the ratio of the adhesive force when plasma treatment is applied to the adhesive force when there is no plasma treatment (the increase rate of adhesive force caused by plasma treatment) is calculated.

<Adhesive force after light curing> A reinforcing film is attached to the polyimide film substrate (with plasma treatment and without plasma treatment), and then a 365 nm LED (Light Emitting Diode) is used ) The light source irradiates ultraviolet rays with a cumulative light intensity of 4000 mJ/cm ² from the side of the reinforcing film (the side of the PET film) to light-cur the adhesive layer. Using this test sample, the adhesive force was measured by a 180° peel test in the same manner as described above.

The composition of the adhesive of each reinforcing film (the type and amount of acrylic oligomer, the type and amount of light hardener, the amount of crosslinking accelerator (zirconium tetraacetone)), before and after light curing Adhesion to the polyimide film and the increase rate of the adhesive force before and after photocuring, and the increase rate of the initial adhesive force caused by the plasma treatment (the adhesive force before the photocuring of "plasma treatment" is relative to " The ratio of the adhesive force before light hardening without plasma treatment is shown in Table 1. The addition amount in the composition of Table 1 is the addition amount (parts by weight) relative to 100 parts by weight of the base polymer.

[Table 1] composition Follow force Oligomer Light hardener Crosslinking accelerator No plasma treatment With plasma treatment Initial increase rate of adhesive force (times) Adhesion (N/25 mm) Adhesion force rise rate (times) Adhesion (N/25 mm) Adhesion force rise rate (times) species Tg (℃) COOH the amount species the amount the amount Before light hardening After light hardening Before light hardening After light hardening Example 1 UC-3000 65 Have 1 A200 30 - 0.14 12.2 85.3 0.17 26.0 156.3 1.17 Example 2 UC-3000 65 Have 0.5 A200 30 - 0.14 12.1 85.2 0.16 26.1 168.3 1.10 Example 3 UC-3000 65 Have 5 A200 30 - 0.21 13.9 66.1 0.23 28.3 121.9 1.11 Example 4 UC-3000 65 Have 0.5 A200/A600 30/5 0.2 0.06 4.3 71.8 0.08 12.0 150.0 1.33 Comparative example 1 - A200 30 - 0.15 7.4 50.3 0.21 18.2 88.6 1.40 Comparative example 2 UC-3510 -50 Have 0.5 A200/A600 30/5 0.2 0.06 4.1 68.0 0.21 15.9 75.7 3.50 Comparative example 3 UP-1190 -77 no 0.5 A200/A600 30/5 0.2 0.06 5.7 94.2 0.15 13.4 89.3 2.50 Comparative example 4 Oligomer A 144 no 0.5 A200/A600 30/5 0.2 0.06 4.3 71.7 0.14 9.4 66.9 2.33

In any of the Examples and Comparative Examples, when a reinforcing film was attached to a polyimide film substrate that had not been subjected to plasma treatment, the increase in adhesive force before and after photocuring was 100 times or less. When using a plasma-treated polyimide film substrate as the adherend, in Examples 1 to 4, the adhesive force increased to 120 times or more due to photocuring. In Examples 1, 2, and 4, The rate of increase of subsequent force exceeds 150 times. On the other hand, in Comparative Example 1 in which the adhesive composition does not contain oligomers, even when the plasma-treated polyimide film substrate is used as the adherend, the increase rate of the adhesive force remains at Less than 90 times. In Comparative Examples 2 and 3 with the addition of low Tg oligomers and Comparative Example 4 with the addition of high Tg oligomers without carboxyl groups, in the case of using a plasma-treated polyimide film as the adherend The increase rate of the adhesive force before and after the time light hardens is also less than 90 times.

Focusing on the initial adhesive force (adhesive force before photocuring), the increase in the initial adhesive force caused by plasma treatment in Examples 1 to 4 is small. In contrast, in Comparative Examples 1 to 4, The increase in the initial adhesive force caused by the plasma treatment is relatively large, especially in Comparative Examples 2 to 4, the increase in the initial adhesive force caused by the plasma treatment is more obvious.

According to these results, it can be seen that the reinforcing film with a photocurable adhesive layer containing a high Tg oligomer containing a carboxyl group has low initial adhesion to the adherend subjected to activation treatment such as plasma treatment, and secondary processing Excellent performance, showing high adhesion to the adherend after light curing, and excellent adhesion reliability.

1: Film substrate 2: Adhesive layer 5: spacer 10: Reinforcing film 20: adherend

Fig. 1 is a cross-sectional view showing the laminated structure of the reinforcing film. Fig. 2 is a cross-sectional view showing the laminated structure of the reinforcing film. Fig. 3 is a cross-sectional view showing a device for sticking and installing a reinforcing film.

1: Film substrate

2: Adhesive layer

10: Reinforcing film

Claims (15)

A reinforcing film comprising a film substrate and an adhesive layer fixedly laminated on one of the main surfaces of the film substrate; The adhesive layer includes a photocurable composition containing an acrylic base polymer, an acrylic oligomer with a weight average molecular weight of 1,000 to 30,000, a photocuring agent, and a photopolymerization initiator; and The said acrylic oligomer contains a carboxyl group, and the glass transition temperature is 0 degreeC or more. The reinforced film of claim 1, wherein the acrylic base polymer contains one or more selected from the group consisting of a hydroxyl group-containing monomer and a carboxyl group-containing monomer as a monomer unit, and is bonded to a hydroxyl group or a carboxyl The crosslinking agent is introduced with a crosslinking structure. The reinforced film according to claim 1, wherein the acrylic base polymer contains a carboxyl group-containing monomer as a monomer unit, and a crosslinking structure is introduced by a crosslinking agent bonded to the carboxyl group. The reinforced film of claim 2 or 3, wherein the crosslinking agent is an epoxy-based crosslinking agent. The reinforcing film according to any one of claims 2 to 4, wherein the gel fraction of the photocurable composition is 50% or more. The reinforcing film according to any one of claims 1 to 5, wherein the acrylic base polymer does not substantially contain nitrogen atoms. The reinforcing film according to any one of claims 1 to 6, wherein the photocurable composition contains 0.1 to 20 parts by weight of the acrylic oligomer with respect to 100 parts by weight of the acrylic base polymer. The reinforcing film according to any one of claims 1 to 7, wherein the photocurable composition contains 10 to 50 parts by weight of the light hardener with respect to 100 parts by weight of the base polymer. The reinforcing film according to any one of claims 1 to 8, wherein the light hardener is a multifunctional (meth)acrylate. The reinforcing film according to any one of claims 1 to 9, wherein the functional group equivalent of the light hardener is 100 to 500 g/eq. The reinforcing film according to any one of claims 1 to 10, wherein the adhesive force with the polyimide film before photocuring the adhesive layer is 1 N/25 mm or less. A method of manufacturing a device, the device is attached with a reinforcing film on the surface, The method is to temporarily stick the above-mentioned adhesive layer of the reinforcing film of any one of claims 1 to 11 on the surface of the adherend, and then, By irradiating the adhesive layer with active light, the adhesive layer is photocured, and the adhesive force between the reinforcing film and the adherend is increased. The method for manufacturing a device according to claim 12, wherein the surface activation treatment of the adherend is performed before the reinforcing film is temporarily adhered. The method for manufacturing a device of claim 13, wherein the surface activation treatment is plasma treatment. A reinforcing method, which is a reinforcing method of attaching a reinforcing film to the surface of the adherend, The method is to temporarily stick the above-mentioned adhesive layer of the reinforcing film of any one of claims 1 to 11 on the surface of the adherend after the activation treatment after the surface activation treatment of the adherend, and By irradiating the adhesive layer with active light, the adhesive layer is photocured, and the adhesive force between the reinforcing film and the adherend is increased.

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