TW202019700A - Laminate includes a reinforcing film and a surface protective film - Google Patents

Abstract

A laminate (100) of the present invention comprises a reinforcing film (10) which is formed by fixing and laminating a first adhesive layer (12) on a first main surface of a first film substrate (11), and a surface protective film (30) temporarily adhered to a second main surface of the first film substrate. The first adhesive layer (12) is composed of a photocurable composition comprising a base polymer, a photocuring agent, and a photopolymerization initiator. The surface protective film (30) has ultraviolet shielding properties.

Description

Laminate

The present invention relates to a laminate including a reinforcing film.

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 on the main surface of the film substrate with a build-up adhesive layer, and is adhered to the surface of the device through the adhesive layer.

In the state before assembly, processing, transportation, etc. of the device, damage or damage to the adherend can be suppressed by temporarily sticking the adhesive film on the surface of the device or the component parts of the device. The adhesive film temporarily adhered for the purpose of temporary protection of the surface is required to be easily peeled off from the adherend, and no paste remains on the adherend.

Patent Document 1 discloses an adhesive film which, in addition to device assembly, processing, conveyance, etc., is used while the device is attached to the surface of the device without changing. Such an adhesive film has a function of reinforcing the device due to surface protection, dispersion of impact on the device, imparting rigidity to the flexible device, etc.

When attaching the adhesive film to the adherend, there may be a problem of poor adhesion such as mixing of bubbles or deviation of the sticking position. When a poor bonding occurs, the following operation (secondary processing) is carried out: the adhesive film is peeled off from the adherend and another adhesive film is bonded. Adhesive films used as engineering materials are designed on the premise that they are peeled off from the adherend, so they are easy to reprocess. On the other hand, a reinforcing film that is premised on permanent adhesion generally does not assume peeling from the device but is firmly adhered to the surface of the device, so it is difficult to perform secondary processing.

Patent Document 2 discloses an adhesive film provided with a photocurable adhesive layer on the surface of a hard coating film. The light-curing adhesive is easy to peel off from the adhered body due to its low adhesion to the adherend before light-hardening. The film with the light-curing adhesive fixed on it can be used as a reinforcing film with secondary processability. use. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2017-132977 [Patent Document 2] Japanese Patent Laid-Open No. 2015-217530

[Problems to be solved by the invention]

The photocurable adhesive can be arbitrarily set at the time of hardening after being adhered to the adherend. As described above, the secondary workability is also excellent. In addition, after the film is attached to the surface of the adherend via a photocurable adhesive, the film at a specific position can be easily cut and patterned, and the patterned position can be peeled off and removed.

However, if a reinforcing film with a photocurable adhesive is attached to the adherend and the semi-finished product in a state before photocuring of the adhesive is stored for a long period of time, there is a light-curing adhesive that does not irradiate the semi-finished product. As the adhesive force rises, it becomes difficult to peel off the reinforcing film from the adherend. In view of this problem, an object of the present invention is to provide a reinforced film laminate, which does not easily cause a temporal change in the adhesive force of the photocurable adhesive even when the semi-finished product in a state of being bonded to the adherend is stored for a long time. [Technical means to solve the problem]

The present invention relates to a laminate including: a reinforcement film having a first adhesive layer fixedly laminated on a first main surface of a first film; and a surface protective film temporarily adhered to a first film substrate The second main face. The first adhesive layer includes a photocurable composition containing a base polymer, a photohardener, and a photopolymerization initiator, and the surface protective film has ultraviolet shielding properties. The surface protective film having ultraviolet shielding properties preferably has a light transmittance at a specific wavelength of 30% or less.

The adhesion between the surface protective film and the first film substrate is preferably smaller than the adhesion between the first adhesive layer and the adherend. As an example of the adherend, a polyimide film can be mentioned.

In one embodiment, the surface protection film includes a second adhesive layer that is fixedly deposited on the second film substrate. In this form, it is preferable that the second adhesive layer of the surface protective film is temporarily adhered to the second main surface of the first film substrate of the reinforcing film.

The laminate may also include a spacer temporarily adhered to the first adhesive layer. The adhesion between the surface protection film and the first film substrate is preferably greater than the adhesion between the first adhesive layer and the separator. The separator can also have ultraviolet shielding properties. [Effect of invention]

The reinforcing film has a low adhesion force between the adhesive layer and the adherend before photo-hardening, so it is easy to perform secondary processing. If the adhesive layer is photo-hardened, it exhibits a higher adhesive force, which helps to strengthen the device and Increased reliability. The photohardenable adhesive can be arbitrarily set at the time of hardening after being attached to the adherend. In addition, by temporarily bonding the ultraviolet shielding surface protective film to the film base of the reinforcing film in advance, it is possible to suppress the photohardening of the adhesive caused by the light emitted by the fluorescent lamp or the like in the storage environment. By using the laminated body of the present invention, the semi-finished product after being bonded to the adherend can be stored for a long time, and the preparation time of the steps can be flexibly handled.

FIG. 1 is a cross-sectional view showing an embodiment of a reinforcing film laminate of the present invention. The reinforcing film 10 includes a first adhesive layer 12 on the first main surface of the first film substrate 11. The first adhesive layer 12 is fixedly laminated on the main surface of the first film substrate 11. Preferably, a spacer 50 is temporarily adhered to the surface of the first adhesive layer 12.

The first adhesive layer 12 is a photo-curable adhesive containing a photo-curable composition, and contains a base polymer, a photo hardener, and a photopolymerization initiator. When the first adhesive layer 12 is irradiated with active light such as ultraviolet rays, an active species is generated from the photopolymerization initiator, and the polymerization reaction of the photohardener proceeds. As a result, the adhesive layer 12 is hardened, and the adhesive force with the adherend increases.

An ultraviolet shielding surface protective film 30 is temporarily adhered to the second main surface of the first film substrate 11. The surface protection film 30 includes a second adhesive layer 32 fixedly laminated on the surface of the second film substrate 31, and the second adhesive layer 32 is bonded to the second main surface of the first film substrate 11.

The so-called "fixation" refers to a state where the two deposited layers are firmly adhered, impossible or difficult to peel at the interface between the two. The so-called "temporary adhesion" refers to the state where the adhesion between the two layers is small and can be easily peeled off at the interface between the two.

2A to 2C are conceptual diagrams showing examples of use of laminates. First, the separator 50 is peeled from the laminate 100 to expose the adhesive layer 12 (FIG. 2A). The laminated body 102 after peeling off the separator is bonded to the adherend 70 via the adhesive layer 12 (FIG. 2B ). At this stage, since the adhesive layer 12 is not hardened, the adhesive force to the adherend 70 is low, and the reinforcing film 10 is temporarily adhered to the adherend 70. The adhesive layer 12 is in a state where the interface between the adherend 70 and the adhesive layer 12 can be easily peeled off (secondary processing state) before photohardening.

The surface protective film 30 has ultraviolet shielding properties. In a state where the surface protection film 30 is attached (FIG. 2B ), the ultraviolet rays included in the ambient light (such as fluorescent lamps) are shielded by the surface protection film and do not reach the adhesive layer 12. Therefore, the photohardening of the adhesive layer 12 in the storage environment is suppressed, and even when the semi-finished product is stored for a long period of time, the adhesive force is unlikely to increase, and the secondary processability can be maintained.

The film base 11 has ultraviolet transmittance. Therefore, as shown in FIG. 2C, after the surface protective film 30 is peeled off from the reinforcing film 10 and the ultraviolet ray is irradiated from the film base material 11 side, the adhesive layer 12 is cured by the ultraviolet light transmitted through the film base material 11. By light curing, the adhesive force of the adhesive layer 12 rises, so that the reinforcing film 10 is in a state of being firmly adhered to the adherend 70.

As described above, in the present invention, by providing the surface protective film 30 with ultraviolet shielding properties, even when the semi-finished product obtained by bonding the reinforcing film 10 and the adherend 70 is stored for a long time under a fluorescent lamp, It is possible to suppress undesired light hardening of the adhesive layer 12 and maintain secondary processability. By peeling and removing the surface protective film 30 and irradiating light from the film base material 11 side to harden the adhesive layer 12, the adhesive force can be appropriately increased. Therefore, it is possible to flexibly respond to the preparation time of the manufacturing steps of the device.

[Structure of laminate] Hereinafter, preferred forms of the layers constituting the laminate will be described in order.

<First film substrate> As the film substrate 11 of the reinforcing film 10, a plastic film is used. In order to fix the film substrate 11 and the adhesive layer 12, the first main surface of the film substrate 11 (the surface on which the adhesive layer 12 is attached) is preferably not subjected to release treatment.

The thickness of the film substrate 11 is, for example, about 4 to 500 μm. From the viewpoint of reinforcing the device by imparting rigidity or impact relaxation, the thickness of the film substrate 11 is preferably 12 μm or more, more preferably 30 μm or more, and still more preferably 45 μm or more. From the viewpoint of making the reinforcing film flexible and improving operability, the thickness of the film substrate 11 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 11 is preferably 100 to 3000 kg/cm ² , more preferably 200 to 2900 kg/cm ² , and further preferably 300 to 2800 kg /cm ² , particularly preferably 400 to 2700 kg/cm ² .

Examples of the plastic material constituting the film substrate 11 include polyester-based resins, polyolefin-based resins, cyclic polyolefin-based resins, polyamide-based resins, polyimide-based resins, polyether ether ketone, and polyether satin Wait. In the reinforcing film for optical devices such as displays, the film substrate 11 is preferably a transparent film. In terms of both mechanical strength and transparency, as the material of the film substrate 11, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate can be used favorably Department of resin.

In the case of irradiating active light from the film substrate 11 side to photocure the adhesive layer 12, the film substrate 11 preferably has transparency to the active light used for curing the adhesive layer 12. The transmittance of light with a wavelength of 365 nm of the film substrate 11 is preferably 60% or more, more preferably 70% or more, further preferably 75% or more, and particularly preferably 80% or more. The transmittance of light having a wavelength of 405 nm of the film substrate 11 is preferably 60% or more, more preferably 70% or more, further preferably 75% or more, and particularly preferably 80% or more.

Functional coatings such as an easy adhesion layer, an easy slip layer, a release layer, an antistatic layer, a hard coat layer, and an anti-reflection layer may also be provided on the surface of the film substrate 11. In addition, as described above, in order to fix the film substrate 11 and the adhesive layer 12, it is preferable that no release layer is provided on the first main surface of the film substrate 11 (the surface on which the adhesive layer 12 is attached).

<First Adhesive Layer> The adhesive layer 12 fixedly laminated on the film substrate 11 is a photo-curable composition containing a base polymer, a photo-hardening agent, and a photo-polymerization initiator. When the reinforcing film 10 is used in an optical device such as a display, the total light transmittance of the adhesive layer 12 is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. The haze of the adhesive layer 12 is preferably 2% or less, more preferably 1% or less, and further 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. The type of base polymer is not particularly limited, and an acrylic polymer, a polysiloxane polymer, a urethane polymer, a rubber polymer, etc. may be appropriately selected. In particular, in terms of excellent optical transparency and adhesion, and easy control of adhesion, the adhesive composition preferably contains an acrylic polymer as a base polymer, and preferably 50% by weight or more of the adhesive composition It is an acrylic polymer.

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

As the (meth)acrylic acid alkyl ester, an alkyl (meth)acrylate having an alkyl group having 1 to 20 carbon atoms can be preferably used. The alkyl group of the (meth)acrylic acid alkyl ester 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, amyl (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, iso(meth)acrylate Tri (dodecyl) ester, myristyl (meth) acrylate, isotetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate Alkyl, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, nonadecyl (meth)acrylate, (A Group) aralkyl acrylate, etc.

The content of the alkyl (meth)acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 55% by weight or more with respect to 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. Examples of the monomer having a crosslinkable functional group include a hydroxyl group-containing monomer or a carboxyl group-containing monomer. The acrylic base polymer may have both a hydroxyl group-containing monomer and a carboxyl group-containing monomer as monomer components, or may have only one of them. The hydroxyl group or carboxyl group of the base polymer becomes the reaction point with the crosslinking agent described later. 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 an epoxy-based crosslinking agent is used, it is preferably a copolymerization component containing a carboxyl group-containing monomer as a base polymer. Due to the introduction of the cross-linked structure in the base polymer, there is a tendency for the cohesive force to increase, the adhesive force of the adhesive layer 12 to increase, and the paste residue to the adherend during secondary processing tends to decrease.

Examples of the hydroxyl group-containing monomer 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 the carboxyl group-containing monomer include (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, Butenoic 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 3 to 25% by weight, and further preferably 5 ~20% by weight.

The acrylic base polymer may also contain N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperidine, vinylpyrrolidine, vinyl Nitrogen-containing monomers such as pyrrole, vinyl imidazole, vinyl oxazole, vinyl 𠰌olin, N-acrylonitrile, N-vinylcarboxamide, N-vinylcaprolactam as constituent monomer components .

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

The adhesive properties of the adhesive before light curing are easily affected by the composition and molecular weight of the base polymer. The larger the molecular weight of the base polymer, the harder the adhesive becomes. 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. In addition, when a crosslinked structure is introduced into the base polymer, the molecular weight of the base polymer refers to the molecular weight before introduction of the crosslinked structure.

The higher the content of the high Tg monomer component in the constituent components of the base polymer, the harder the adhesive becomes. Furthermore, the so-called high Tg monomer means a monomer having a high glass transition temperature (Tg) of the homopolymer. Examples of monomers having a homopolymer Tg of 40°C or higher include dicyclopentyl methacrylate (Tg: 175°C), dicyclopentyl acrylate (Tg: 120°C), and isomethacrylate (Tg: 173℃), isobutyl acrylate (Tg: 97℃), methyl methacrylate (Tg: 105℃), 1-adamantyl methacrylate (Tg: 250℃), 1-adamantyl acrylate (Tg: 153°C) and other (meth)acrylic monomers; acrylamide (Tg: 145°C), dimethylacrylamide (Tg: 119°C), diethylacrylamide (Tg: 81 ℃), dimethylaminopropyl acrylamide (Tg: 134℃), isopropyl acrylamide (Tg: 134℃), hydroxyethyl acrylamide (Tg: 98℃), etc. Vinyl monomers; acid monomers such as methacrylic acid (Tg: 228°C), acrylic acid (Tg: 106°C); N-vinylpyrrolidone (Tg: 54°C), etc.

In the acrylic base polymer, the content of the monomer whose Tg of the homopolymer is preferably 40° C. or higher relative to the total amount of constituent monomer components is 1 to 50% by weight, more preferably 3 to 40% by weight. In order to form an adhesive layer having a moderate hardness and excellent secondary processability, the monomer component of the base polymer is preferably a monomer component containing a homopolymer with a Tg of 80°C or higher, and more preferably a homopolymer The Tg of the substance is a monomer component above 100°C. In the acrylic base polymer, the content of the monomer whose Tg of the homopolymer is 100° C. or higher relative to the total amount of constituent monomer components is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and still more preferably 1 More than 3% by weight, particularly preferably more than 3% by weight.

The acrylic polymer as a base polymer can be obtained by polymerizing the above monomer components by various well-known methods such as solution polymerization, emulsion polymerization, and bulk polymerization. From the viewpoint of the balance of characteristics such as adhesive force and holding force of the adhesive, or 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.

(Crosslinking agent) From the viewpoint of giving a moderate cohesive force to the adhesive, it is preferable to introduce a cross-linked structure into the base polymer. For example, a cross-linking structure is introduced by adding a cross-linking agent to the solution after the base polymer is polymerized and heating if necessary. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelates. Department of cross-linking agent. 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 cross-linked structure, isocyanate-based cross-linking agents and epoxy-based cross-linking agents are preferred.

As the isocyanate-based crosslinking agent, a polyisocyanate having two or more isocyanate groups in one molecule is used. Examples of the isocyanate-based crosslinking agent include: lower aliphatic polyisocyanates such as butylated diisocyanate and hexamethylene diisocyanate; cyclopentyl diisocyanate, cyclohexyl diisocyanate, and isophorone diisocyanate. Alicyclic isocyanates; 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate and other aromatic isocyanates; trimethylolpropane/methylidene Diisocyanate terpolymer adducts (for example, "Coronate L" manufactured by Tosoh), trimethylolpropane/hexamethylene diisocyanate terpolymer adducts (for example, "Coronate HL" manufactured by Tosoh), Trimethylolpropane adduct of xylylene diisocyanate (for example, "Takenate D110N" manufactured by Mitsui Chemicals, isocyanurate body of hexamethylene diisocyanate (for example, "Coronate HX" manufactured by Tosoh ) And other isocyanate adducts.

As the epoxy-based crosslinking agent, a multifunctional epoxy compound having two or more epoxy groups in one molecule can be used. The epoxy group of the epoxy-based crosslinking agent may be a glycidyl group. Examples of the epoxy-based crosslinking agent include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, and 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, tri Hydroxymethylpropane polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (2-hydroxyethyl) isocyanuric acid triglycidyl ester, 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.

The amount of the cross-linking 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. Moreover, the value obtained by dividing the amount of use (parts by weight) of the crosslinking agent relative to 100 parts by weight of the base polymer by the functional group equivalent (g/eq) of the crosslinking agent is preferably 0.00015 to 0.11, more preferably 0.001 to 0.077 It is further preferably 0.003 to 0.055, and particularly preferably 0.0045 to 0.044. By making the amount of crosslinking agent larger than the ordinary acrylic optical transparent adhesive for permanent adhesion, the adhesive has a moderate hardness, and the paste residue to the adherend is reduced during the secondary processing, Tendency to improve secondary workability.

In order to promote the formation of cross-linked structures, cross-linked catalysts can also be used. For example, examples of the crosslinking catalyst of the isocyanate-based crosslinking agent include tetra-n-butyl titanate, tetraisopropyl titanate, iron(III) acetone, butyl tin oxide, dioctyl tin dilaurate, and di Metal-based cross-linking catalysts (especially tin-based cross-linking catalysts) such as dibutyltin laurate, etc. The amount of crosslinking catalyst used is generally 0.05 parts by weight or less relative to 100 parts by weight of the base polymer.

(Light hardener) The adhesive composition constituting the adhesive layer 12 contains a light hardener in addition to the base polymer. If the adhesive layer 12 containing the photo-curable adhesive composition is photo-hardened after being attached to the adherend, the adhesive force with the adherend is increased.

As the light hardener, a compound having two or more ethylenically unsaturated bonds in one molecule is preferable. In addition, the light hardener is preferably a compound that exhibits compatibility with the base polymer. In terms of exhibiting a moderate compatibility with the base polymer, the light hardener is preferably a liquid at ordinary temperature. By making the photo hardener compatible with the base polymer and dispersing it uniformly in the composition, the contact area with the adherend can be secured, and the adhesive layer 12 with high transparency can be formed. Moreover, by making the base polymer and the light hardener exhibit moderate compatibility, it is easy to uniformly introduce a cross-linked structure into the adhesive layer 12 after light hardening, and there is a tendency that the adhesive force with the adherend increases 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 parameters 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 multifunctional (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 isocyanurate 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, di Pentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerol di(meth)acrylate, (meth)acrylate carbamate, epoxy (meth)acrylate, Butadiene (meth)acrylate, isoprene (meth)acrylate, etc. Among these, in terms of excellent compatibility with the acrylic base polymer, polyethylene glycol di(meth)acrylate or polypropylene glycol di(meth)acrylate is preferred, and polyglycol is particularly preferred. Ethylene glycol di(meth)acrylate.

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 smaller 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, further preferably 500 or less, and particularly preferably 400 or less.

In the adhesive layer 12 before photo-hardening, the characteristics of the base polymer are the main dominant factors of adhesion. Therefore, as long as the base polymer of the adhesive composition is the same, even if the types of the light hardeners are different, the difference in the adhesive properties of the adhesive layer before the light hardening is small. The type or content of the light hardener mainly affects the adhesion of the adhesive layer after light hardening. The smaller the functional group equivalent (ie, the greater the number of functional groups per unit molecular weight) and the greater the content of the light hardener, the more able to set the difference in adhesion force before and after light hardening.

From the viewpoint of having high compatibility with the base polymer and enhancing the adhesion after light curing, the functional group equivalent (g/eq) of the light hardener is preferably 500 or less, more preferably 400 or less, and further It is preferably 300 or less, and particularly preferably 200 or less. On the other hand, if the functional group equivalent of the light hardener is too small, there may be a case where the density of the crosslinking point of the adhesive layer after photohardening becomes high and the adhesiveness decreases. 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 the acrylic base polymer and the multifunctional acrylate light hardener, when the functional group equivalent of the light hardener is small, there is a strong interaction between the base polymer and the light hardener, and the initial adhesion strength increases The tendency. In the application of the present invention, there is a case where the excessive increase in the initial adhesive force causes a decrease in secondary workability. From the viewpoint of maintaining the adhesive force between the adhesive layer 12 and the adherend before photohardening within an appropriate range, it is also preferable that the functional group equivalent of the photohardener 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 amount of the photo hardener to the above range, the adhesiveness between the adhesive layer and the adherend after photo hardening can be adjusted to an appropriate range. The content of the light hardener is more preferably 15 to 45 parts by weight relative to 100 parts by weight of the base polymer, and further preferably 20 to 40 parts by weight.

(Photopolymerization initiator) The photopolymerization initiator generates active species by the irradiation of active light and promotes the hardening reaction of the photohardener. As the photopolymerization initiator, a photocationic initiator (photoacid generator), a photoradical initiator, a photoanion initiator (photobase generator), etc. can be used depending on the type of photohardener. When an ethylenically unsaturated compound such as a multifunctional acrylate is used as a light hardener, 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 the radical transfer from the photo radical initiator to the photo hardener. As the photo radical initiator (photo radical generator), those that generate radicals by irradiation with visible light or ultraviolet rays having a wavelength shorter than 450 nm are preferred, and examples include hydroxyketones and benzoyl dimethyl condensate. Ketones, aminoketones, acetylphosphine oxides, benzophenones, trichloromethyl-containing derivatives, etc. The photo radical initiator may be used alone, or two or more kinds may be used in combination.

When transparency is required for the adhesive layer 12, the photopolymerization initiator is preferably less sensitive to light (visible light) with a wavelength longer than 400 nm. For example, the absorption coefficient at a wavelength of 405 nm can be used well. ×10 ² [mLg ^-1 cm ^-1 ] or less photopolymerization initiator.

The content of the photopolymerization initiator in the adhesive layer 12 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 12 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. If the content of the photopolymerization initiator in the adhesive layer 12 is too small, there may be a case where the photohardening reaction does not sufficiently proceed even when irradiated with ultraviolet rays. On the other hand, if the content of the photopolymerization initiator is too large, there is a slight ultraviolet ray passing through the UV-shielding surface protective film 30, and the photocuring of the adhesive under the storage environment may occur, and the secondary processing of the reinforcing film becomes difficult Case.

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

(Production of adhesive layer) By applying the above-mentioned adhesive composition by roll coating, contact roll coating, gravure coating, reverse coating, roll brush coating, spray coating, dip roll coating, bar coating, knife coating, air Knife knife coating, curtain coating, lip coating, die coating, etc. are applied to the substrate, and the solvent is dried and removed as necessary to form an adhesive layer. As a drying method, an appropriate method may 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 12 is, for example, about 1 to 300 μm. There is a tendency that the greater the thickness of the adhesive layer 12 is, the more the adhesion with the adherend 12 will be. On the other hand, when the thickness of the adhesive layer 12 is too large, there are cases where the fluidity before photo-curing is high and the operation becomes difficult. Therefore, the thickness of the adhesive layer 12 is preferably 5 to 100 μm, more preferably 8 to 50 μm, still more preferably 10 to 40 μm, and particularly preferably 13 to 30 μm.

When the adhesive composition contains a crosslinking agent, it is preferable to perform crosslinking by heating or aging at the same time as the drying of the solvent or after the drying of the solvent. The heating temperature or heating time is appropriately set according to the type of crosslinking agent used, and is usually crosslinked by heating in the range of 20°C to 160°C for about 1 minute to 7 days. The heating used for drying and removing 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. When the reinforcing film is peeled from the adherend due to secondary processing, the tendency to remain in the paste of the adherend is suppressed. The gel fraction of the adhesive layer 12 before photohardening is preferably 30% or more, more preferably 50% or more, and further preferably 60% or more, particularly preferably 65% or more. The gel fraction of the adhesive layer 12 before light curing can also be more than 70% or more than 75%.

Since the adhesive contains an unreacted photo hardener, the gel fraction of the adhesive layer 12 before photo hardening is generally 90% or less. If the gel fraction of the adhesive layer 12 before photohardening is too large, there may be a case where the holding power to the adherend decreases and the initial adhesive force becomes insufficient. Therefore, the gel fraction of the adhesive layer 12 before photohardening is preferably 85% or less, and more preferably 80% or less.

The gel fraction can be obtained as an insoluble matter in a solvent such as ethyl acetate, specifically as an insoluble component after immersing the adhesive layer in ethyl acetate at 23°C for 7 days relative to the test before immersion The weight fraction of the sample (unit:% by weight) is obtained. Generally speaking, the gel fraction of the polymer is equal to the degree of crosslinking. The more crosslinked parts in the polymer, the greater the gel fraction. In addition, the greater the amount of photohardener, the smaller the gel fraction. After the cross-linking structure is introduced into the polymer by the cross-linking agent, the light hardener also remains unreacted. Thus, a photo-curable adhesive layer 12 containing a base polymer and a photo-hardener is formed.

<surface protective film> The surface protective film 30 attached to the first film substrate 11 of the reinforcing film 10 has ultraviolet shielding properties. The surface protective film 30 having ultraviolet shielding property means that the light of the absorption wavelength of the photopolymerization initiator contained in the first adhesive layer 12 is shielded. Specifically, it is preferable that the surface protection film has a transmittance of light with a maximum absorption wavelength in a region below 450 nm of the photopolymerization initiator. When the photopolymerization initiator has a plurality of absorption maxima in the wavelength region below 450 nm, the absorption maximum wavelength with the longest wavelength in the region below 450 nm is taken as the absorption maximum wavelength of the photopolymerization initiator. The surface protective film 30 is preferably a light transmittance of the absorption maximum wavelength of the photopolymerization initiator of 30% or less, more preferably 20% or less, and further preferably 10% or less, particularly preferably 5% or less.

In one aspect, the surface protective film 30 preferably has a light transmittance of 405 nm at a wavelength of 30% or less, more preferably 20% or less, and further preferably 10% or less, particularly preferably 5% or less. In another aspect, the surface protective film 30 preferably has a light transmittance of 365 nm at a wavelength of 30% or less, more preferably 20% or less, and further preferably 10% or less, and particularly preferably 5% or less.

The light of ordinary fluorescent lamps includes mercury bright lines of 365 nm and 405 nm as ultraviolet rays. That is, when it is convenient to store the semi-finished product formed by bonding the reinforcing film 10 to the adherend 70 under fluorescent lamps for a long time, as long as the surface of the film substrate 11 has a surface with a low light transmittance of these wavelengths attached The protective film 30 can also suppress the light curing of the adhesive layer 12 due to the light emitted by the fluorescent lamp.

The surface protective film 30 can be attached to the first film substrate 11, and as long as it has ultraviolet shielding properties, its structure or material is not particularly limited. After the reinforcing film 10 is attached to the adherend 70, in order to easily peel the surface protective film 30 from the first film substrate 11 before the light curing of the first adhesive layer 12, the surface protective film 30 is preferably as shown in FIG. As shown in FIG. 1, a second adhesive layer 32 with a low adhesiveness that is fixedly laminated on the surface of the second film substrate 31 is provided.

The surface protective film 30 preferably has ultraviolet shielding properties on either or both of the film substrate 31 and the adhesive layer 32. Examples of a method for making the film substrate 31 have ultraviolet shielding properties include a method of using a film containing a resin material having ultraviolet absorption such as polyimide; and a coloring material (pigment, dye) having ultraviolet absorption such as carbon black , Pigments, etc.), titanium oxide and other coloring materials with ultraviolet reflectivity, ultraviolet absorbers, etc. are mixed with resin materials; a method of coating a layer containing a coloring material or an ultraviolet absorber on the surface of the film; setting on the surface of the film The method of reflecting ultraviolet rays by multi-layer film; and the method of forming fine irregularities on the film surface to scatter and reflect ultraviolet rays, etc. In order to make the adhesive layer 32 have ultraviolet shielding properties, for example, an ultraviolet absorber or a coloring agent having ultraviolet absorbance may be added to the adhesive composition.

<Second film substrate> The material or thickness of the second film substrate 31 of the surface protection film 30 is not particularly limited. In addition to the function of suppressing the photohardening of the adhesive layer 12 by ultraviolet shielding, the surface protective film 30 also has the function of suppressing damage or deformation of the first film substrate 11 of the reinforcing film 10. From the viewpoint of both surface protection and flexibility of the reinforcing film, the thickness of the second film substrate 31 is preferably about 5 to 200 μm, more preferably 10 to 100 μm, and still more preferably 15 to 80 μm. From the viewpoint of material cost reduction, the thickness of the second film substrate 31 is preferably smaller than the thickness of the first film substrate 11.

Examples of the material of the second film substrate 31 include polyester-based resins, polyolefin-based resins, cyclic polyolefin-based resins, polyamide-based resins, and polyimide-based resins. The material of the second film substrate 31 may be the same as or different from the material of the first film substrate 11. On the surface of the film substrate 31, functional coatings such as an easy-adhesion layer, an easy-slip layer, a release layer, an antistatic layer, a hard coat layer, and an anti-reflection layer can also be provided. In order to fix with the adhesive layer 32 of the film substrate 31, it is preferable that no release layer is provided on the surface of the film substrate 31 where the adhesive layer 32 is attached.

In the case where the film base 31 has ultraviolet shielding properties, it is preferably polyimide or the like. As described above, the ultraviolet-absorbing coloring material or ultraviolet absorber may be mixed with the resin material of the film base material to have ultraviolet shielding properties. In addition, an ultraviolet absorbing layer may be formed on the surface of the film substrate, or fine irregularities may be formed on the surface of the film substrate to scatter and reflect the ultraviolet rays.

<Second adhesive layer> From the viewpoint of taking into consideration both the adhesive stability of the first film substrate 11 and the ease of peeling, the second adhesive layer 32 of the surface protective film 30 is preferably not photocurable. From the viewpoint of selectively peeling the laminate 102 bonded to the adherend 70 at the interface between the first film substrate 11 and the second adhesive layer 32, the adhesion of the second adhesive layer 32 is better It is less than the adhesive force of the first adhesive layer 12 before photohardening. The adhesion of the surface protective film 30 (second adhesive layer 32) to the first film substrate 11 is preferably 1 N/25 mm or less, more preferably 0.5 N/25 mm or less, and further preferably 0.3 N/25 mm or less, particularly preferably 0.2 N/25 mm or less. On the other hand, from the viewpoint of ensuring the adhesion stability with the first film substrate 11, the adhesion of the surface protective film 30 to the first film substrate is preferably 0.01 N/25 mm or more, more preferably 0.02 N /25 mm or more, and more preferably 0.03 N/25 mm or more. Then the force is the measured value obtained by the 180° peel test with a tensile speed of 0.3 m/min.

The composition of the adhesive constituting the second adhesive layer 32 is not particularly limited, and acrylic polymers, polysiloxane polymers, polyesters, polyurethanes, polyamides, poly Rubber-based polymers such as vinyl ether, vinyl acetate/vinyl chloride copolymer, modified polyolefin, epoxy-based, fluorine-based, natural rubber, and synthetic rubber are used as the base polymer. In particular, in terms of easily forming an easily peelable (weak adhesive) adhesive, acrylic adhesives, urethane adhesives, and polysiloxane adhesives can be preferably used.

(Acrylic adhesive) Examples of the base polymer of the acrylic adhesive include the same acrylic polymer as the base polymer constituting the first adhesive layer. A cross-linked structure obtained by a multifunctional isocyanate compound, a multifunctional epoxy compound, or the like is preferably introduced into the acrylic base polymer.

(Urethane adhesive) As the urethane-based base polymer of the urethane-based adhesive, a reactant of a polyol and a polyisocyanate compound can be used. Examples of the polyol include a polyol (diol) having 2 hydroxyl groups in 1 molecule, a polyol (triol) having 3 hydroxyl groups in 1 molecule, and a polyol (tetraol) having 4 hydroxyl groups in 1 molecule. 1. Polyol (pentaol) with 5 hydroxyl groups in one molecule, Polyol (hexanol) with 6 hydroxyl groups in one molecule, etc. As the polyol component, polymer polyols such as polyester polyol, polyether polyol, polycarbonate polyol, and caprolactone polyol can also be used. In terms of improving the cohesive force of the adhesive, exhibiting a moderate adhesion to the adherend, and having excellent re-peelability from the adherend, it is preferable to include a triol as the urethane-based base polymer The polyol component. As the high molecular weight triol, a polyether polyol obtained by ring-opening addition polymerization of triol such as glycerin and trimethylolpropane can be used favorably.

The polyisocyanate used for formation of the urethane-based base polymer may be any of aliphatic polyisocyanate, alicyclic polyisocyanate, and aromatic polyisocyanate. As the polyisocyanate, a urethane prepolymer having an isocyanate group at the terminal may also be used. By reacting the polyol with the polyisocyanate in such a way that the polyisocyanate becomes excessive, an urethane prepolymer having an isocyanate group at the terminal can be obtained.

(Polysilicone adhesive) Examples of the polysiloxane-based base polymer of the polysiloxane-based adhesive include peroxide cross-linked polysiloxane and addition reaction-type polysiloxane. Among them, addition reaction type polysiloxane is preferred, and organic polysiloxane containing phenyl group is particularly preferred. Examples of the phenyl group-containing organic polysiloxane include polyalkylphenylsiloxanes such as polymethylphenylsiloxane and polyethylphenylsiloxane. The addition reaction type silicone adhesive composition preferably contains silicone rubber and silicone resin.

The polysiloxane is preferably an organic polysiloxane containing phenyl groups, and among them, a polysiloxane containing organic polysiloxane containing methylphenylsiloxane as a main structural unit is preferred. The organic polysiloxane in the polysiloxane rubber can also have vinyl and other functional groups as needed. The weight average molecular weight of the organic polysiloxane is preferably 150,000 to 1.5 million, more preferably 280,000 to 1 million, and still more preferably 500,000 to 900,000.

Examples of polysiloxane resins include those containing organic polysiloxanes containing (co)polymers having M units selected from the group consisting of structural units “R ₃ -Si _1/2 ”, comprising structural units "SiO _2" Q units, the structural unit comprising "R-SiO _3/2" units of T, and comprises a structural unit, "R ₂ -SiO" D units of at least one of the units. Furthermore, R in the above structural unit is a hydrocarbon group or a hydroxyl group. Examples of the hydrocarbon group include alkyl groups, cycloalkyl groups, and aryl groups. The ratio of the "M unit" in the polysiloxane resin is preferably 0.3 to 1.5 times that of "at least one unit selected from Q unit, T unit and D unit", and more preferably 0.5 to 1.3 times.

In the silicone adhesive, the silicone rubber and the silicone resin may be in a mixed state, or the silicone rubber and the silicone resin may react to form a condensate or a partial condensate. The silicone rubbers, the silicone resins, or the silicone rubber and the silicone resins can also be bonded via a cross-linking agent. As the cross-linking agent, a silicone-based cross-linking agent, a peroxide-based cross-linking agent and the like are preferred.

(Production of adhesive layer) The adhesive composition is prepared by adding a crosslinking agent and various additives as needed in the base polymer. As described above, the adhesive force of the second adhesive layer is preferably smaller than the adhesive force of the first adhesive layer. For example, by increasing the amount of cross-linking agent added to reduce the viscosity, there is a tendency for the adhesion of the adhesive to become smaller. In addition, by adding additives such as polysiloxane-modified polysiloxane and other silicone oils, and fluorine-based surfactants, the adhesion of the adhesive can also be reduced. Various additives can also be included in the adhesive composition.

In order for the second adhesive layer to have ultraviolet absorbency, it is preferable that the adhesive composition contains an ultraviolet absorber. Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, tri-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. . In terms of high ultraviolet absorbance and excellent compatibility with acrylic polymers, etc., the three-type ultraviolet absorber is preferred, and among them, the three-group-based ultraviolet absorber containing a hydroxyl group is preferred. It is a hydroxyphenyl tri 𠯤 series ultraviolet absorber. 3. The number of hydroxyl groups of the ultraviolet absorber is preferably 2 or less. As a commercially available product of the three 𠯤 series ultraviolet absorber, 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-tris 𠯤-2-yl)-5 -The reaction product of hydroxyphenyl and [(alkoxy)methyl]ethylene oxide ("TINUVIN 400" manufactured by BASF), 2-(2,4-dihydroxyphenyl)-4,6-bis- Reaction product of (2,4-dimethylphenyl)-1,3,5-triglyceride (2-ethylhexyl) glycidate ("TINUVIN 405" manufactured by BASF), (2,4- Bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-tris ("TINUVIN 460" manufactured by BASF), 2- (4,6-diphenyl-1,3,5-tris-2-yl)-5-[(hexyl)oxy]-phenol ("TINUVIN 577" manufactured by BASF), 2-(2-hydroxyl -4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-tris ("TINUVIN 479" manufactured by BASF), etc. .

The second adhesive layer is formed by coating the adhesive composition on the substrate and drying and removing the solvent and aging for crosslinking as necessary. As the coating method or heating conditions, the conditions for forming the first adhesive layer may be appropriately used as described above. From the viewpoint of adjusting the adhesion of the second adhesive layer 32 to the first film substrate 11 to the above range, the thickness of the second adhesive layer 32 is preferably 2 to 100 μm, more preferably 3 to 50 μm It is further preferably 5 to 30 μm.

<spacer> As shown in FIG. 1, a spacer 50 is preferably temporarily adhered to the surface of the first adhesive layer 12. As the separator 50, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films can be used favorably. The thickness of the separator is usually 3 to 200 μm, preferably 10 to 100 μm, and more preferably 15 to 60 μm. The contact surface of the separator 50 with the adhesive layer 12 is preferably implemented by a silicone-based, fluorine-based, long-chain alkyl-based, or fatty amide-based release agent, or silica powder, etc. Release processing.

By releasing the surface of the separator 50, the separator 50 can be easily peeled off from the laminate 100. Therefore, it is possible to suppress peeling at other interfaces of the laminate 100 when the separator 50 is peeled off.

To prevent the peeling of the separator 50 from the laminate 100 at the interface between the first film substrate 11 and the surface protective film 30 (the second adhesive layer 32), and to select at the interface between the first adhesive layer 12 and the separator 50 From the viewpoint of performing peeling, the adhesive force between the first adhesive layer 12 and the separator 50 is preferably smaller than the adhesive force between the interface of the second adhesive layer 32 and the first film substrate 11. The adhesive force between the first adhesive layer 12 and the spacer 50 is preferably 0.2 N/25 mm or less, more preferably 0.1 N/25 mm or less, and further preferably 0.05 N/25 mm or less. On the other hand, from the viewpoint of suppressing the mixing of air bubbles during bonding or the separation of the separator during storage or transportation of the laminate, the adhesion force between the first adhesive layer 12 and the separator 50 is preferably 0.001 N/25 mm or more It is more preferably 0.005 N/25 mm or more, and still more preferably 0.01 N/25 mm or more.

The spacer 50 may also have ultraviolet shielding properties. By making the separator 50 have ultraviolet shielding properties, even when the laminate 100 before being bonded to the adherend 70 is stored under a fluorescent lamp, the undesired light of the first adhesive layer 12 can be suppressed hardening. In the case where the separator 50 has ultraviolet shielding properties, as described above as a method for making the second film substrate 31 have ultraviolet shielding properties, examples include using a film including a resin material having ultraviolet absorbing properties. Method, a method of mixing a coloring material or a UV absorber with a UV absorber and a resin material, a method of coating a layer containing a coloring material or a UV absorber on the surface of the film, a method of providing a multilayer film on the surface of the film to reflect the UV 1. A method of forming fine irregularities on the film surface to scatter and reflect ultraviolet rays.

As described above as the ultraviolet shielding property of the surface protective film 30, the spacer 50 having ultraviolet shielding property means shielding the light of the absorption wavelength of the photopolymerization initiator contained in the first adhesive layer 12. Specifically, the spacer 50 is preferably a transmittance of light of the maximum absorption wavelength in a region of 450 nm or less of the photopolymerization initiator, and the light transmittance of the absorption maximum wavelength of the photopolymerization initiator is preferably 30% or less, more preferably 20% or less, and further preferably 10% or less, particularly preferably 5% or less. In one aspect, the spacer 50 preferably has a light transmittance of 30% or less at a wavelength of 405 nm, more preferably 20% or less, and further preferably 10% or less, particularly preferably 5% or less. In another aspect, the spacer 50 preferably has a light transmittance of 30% or less at a wavelength of 365 nm, more preferably 20% or less, and further preferably 10% or less, particularly preferably 5% or less.

Furthermore, the spacer 50 does not necessarily have ultraviolet shielding properties. Even when the separator 50 does not have ultraviolet shielding properties, by storing the laminate 100 in a light-shielding container, it is also possible to suppress the photohardening of the first adhesive layer 12 caused by fluorescent lamps or the like.

[Use of Reinforcement Membrane] The reinforcing film is used by being attached to the device or the component parts of the device. Since appropriate rigidity is imparted by bonding the reinforcing film, an improvement in operability or an effect of preventing damage can be expected. In the manufacturing process of the device, when the reinforcement film is bonded to the semi-finished product, the reinforcement film may be bonded to the large semi-finished product before cutting to the size of the product. It is also possible to apply the reinforcing film on a roll-to-roll basis to the mother roll of a device manufactured by a roll-to-roll process.

The adherend to which the reinforcing film is bonded is not particularly limited, and various electronic devices, optical devices and their constituent parts can be cited. As the device is highly integrated, compact, lightweight, and thin, the thickness of the components constituting the device tends to become smaller. Due to the thinning of the constituent members, bending or curling due to stress at the interface of the laminate is likely to occur. In addition, due to the reduction in thickness, it is easy to cause deflection due to its own weight. Since the rigidity can be imparted to the adherend by bonding the reinforcing film, bending, curling, deflection, etc. caused by stress, dead weight, etc. can be suppressed, and the operability is improved. Therefore, it is possible to prevent defects or defects when conveying or processing by an automated device by attaching a reinforcement film to the semi-finished product in the manufacturing step of the device.

In automatic conveyance, contact between the semi-finished product to be conveyed and the conveying arm or pin is inevitable. In addition, there is a case where a semi-finished product is cut for adjusting the shape or removing unnecessary parts. High-integration, small-sized, light-weighted, and thinned devices are prone to breakage caused by localized stress concentration when they come in contact with or cut off from conveying devices. In the manufacturing process of a device in which a plurality of components are stacked, not only are the components stacked in sequence, but also a part of the components or engineering materials are peeled off from the semi-finished product. In the case where the member is too thin, stress may be locally concentrated at the peeling position and its vicinity to cause damage or dimensional change. Since the reinforcing film 10 has stress dispersibility obtained by the adhesive layer 12, the reinforcing film 10 can be attached to the object to be transported and the object to be processed to give moderate rigidity, and the stress can be relaxed and dispersed. Restrain defects such as cracks, cracks, flaking, and dimensional changes.

The reinforcing film 10 may be attached to the entire surface of the adherend 70, or may be selectively attached only to the portion requiring reinforcement. In addition, after the reinforcement film laminate is attached to the entire surface of the adherend, the reinforcement film laminate at a position where no reinforcement is required can be cut off and removed from the surface of the adherend. As long as the adhesive layer 12 is light-hardened, the reinforcing film is temporarily adhered to the surface of the adherend, so the reinforcing film 10 can be easily peeled off from the surface of the adherend 70.

After the reinforcing film laminate 102 is attached to the adherend 70, the surface protective film 30 of the portion to be reinforced may be peeled off and the adhesive layer 12 may be hardened by light irradiation. In this embodiment, in the area where the surface protective film 30 has been peeled off, the adhesive layer 12 will be hardened, and in the area where the surface protective film 30 remains, ultraviolet light will be blocked, so that the hardening of the adhesive layer 12 is suppressed. Therefore, the adhesive layer 12 in the region where the surface protection film is peeled off can be photocured in a position-selective manner. In the area where the surface protection film 30 remains, the adhesive layer 12 is not hardened, so the laminate 102 can be easily peeled off from the surface of the adherend 70.

<Characteristics of the adhesive layer before light curing> (Adhesion) From the viewpoint of easy peeling from the adherend and preventing the residue of the adherend after peeling off the reinforcing film, the adhesion between the adhesive layer 12 and the adherend 70 before photohardening is preferably 5 N/25 mm or less, more preferably 2 N/25 mm or less, and further preferably 1.3 N/25 mm or less. From the viewpoint of preventing peeling of the reinforcing film during storage or operation, the adhesive force between the adhesive layer 12 and the adherend before photocuring is preferably 0.005 N/25 mm or more, more preferably 0.01 N/25 mm or more, and It is preferably 0.1 N/25 mm or more, and particularly preferably 0.3 N/25 mm or more.

The reinforcing film 10 is preferably in a state before photocuring the adhesive layer 12, and the adhesion force to the polyimide film is within the above range. In flexible display panels, flexible printed wiring boards (FPCs), devices in which display panels are integrated with wiring boards, etc., flexible substrate materials are used. From the viewpoint of heat resistance or dimensional stability, poly Acetate film. The adhesive layer 12 has the above-mentioned adhesive strength to the polyimide film as the substrate, and the reinforcing film is easily peeled off before the photocuring of the adhesive layer 12 and is excellent in reliability after photocuring.

(Storage Modulus) The adhesive layer 12 preferably has a shear storage modulus G′ _i at 25° C. before light curing of 1×10 ⁴ to 1.2×10 ⁵ Pa. The shear storage modulus (hereinafter, only referred to as "storage modulus") is obtained by reading the method described in JIS K7244-1 "Plastics-Dynamic Mechanical Properties Test Method" at a frequency of 1 Hz under- The range of 50 to 150° C. is obtained as a 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 high correlation with the cohesive force. There is a tendency that the higher the cohesive force of the adhesive, the greater the holding power of the adherend. If the storage modulus of the adhesive layer 12 before photohardening is 1×10 ⁴ Pa or more, the adhesive has sufficient hardness and cohesive force, so when the reinforcement film is peeled from the adherend, it is less likely to cause damage to the adherend. Paste remains. In addition, when the storage modulus of the adhesive layer 12 is large, the adhesive can be prevented from overflowing from the end surface of the reinforcing film. If the storage modulus of the adhesive layer 12 before photo-hardening is 1.2×10 ⁵ Pa or less, it is easy to peel off at the interface between the adhesive layer 12 and the adherend, and it is not easy to produce adhesive when performing secondary processing The agglomeration of the layer is destroyed or remains on the surface of the adherend. To improve secondary workability of the reinforcing film, suppress secondary machining is adhered to the body of the viewpoint in terms of residual paste, storage at 12 before the light curing adhesive agent layer 25 ℃ modulus G _'i is more preferably 3×10 ⁴ to 1×10 ⁵ Pa, further preferably 4×10 ⁴ to 9.5×10 ⁴ Pa.

＜Light curing of adhesive layer＞ After the laminate 102 is attached to the adherend 70 and the surface protective film 30 is peeled off, the adhesive layer 12 is irradiated with active light such as ultraviolet rays, thereby photocuring the adhesive layer 12. The irradiation intensity or irradiation time of the active light may be appropriately set according to the composition or thickness of the adhesive layer 12.

<Characteristics of adhesive layer after light curing> (Adhesion) From the viewpoint of the practical reliability of the device, the adhesive force between the adhesive layer 12 and the adherend 70 after photohardening is preferably 6 N/25 mm or more, more preferably 10 N/25 mm or more, Furthermore, it is preferably 12 N/25 mm or more, and particularly preferably 14 N/25 mm or more. The reinforcing film is preferably an adhesive layer after photo-curing which has an adhesion to the polyimide film in the above range. The adhesive force between the adhesive layer 12 and the adherend after photohardening is preferably more than 4 times the adhesive force between the adhesive layer 12 and the adherend before photohardening, more preferably 8 times and more preferably 10 More than times.

The adhesive layer 12 preferably has a storage modulus G′ _f at 25° C. after photo-curing of 1.5×10 ⁵ Pa or more. If the storage modulus of the adhesive layer 12 after photohardening is 1.5×10 ⁵ Pa or more, as the cohesive force increases, the adhesive force with the adherend increases, and a higher adhesive 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 decreases, so the peeling force tends to propagate to the adhesive interface, and the adhesive force with the adherend tends to decrease. Therefore, the storage modulus G′ _f at 25° C. after photocuring of the adhesive layer 12 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 ^{1.8 × 10 5 ~ 1.2 × 10} 6 Pa, and further preferably 2 × 10 ⁵ ~ 1 × 10 ⁶ Pa.

The storage modulus ratio G′ _f /G′ _i at 25° C. before and after light curing of the adhesive layer 12 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, further 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 subsequent reliability decreases. Therefore, _G'f /G' _{i is} preferably 100 or less, more preferably 40 or less, and further preferably 30 or less, and particularly preferably 25 or less.

The adherend 70 after the reinforcement film 10 is attached may be subjected to autoclave treatment for the purpose of improving the affinity of the lamination interface of the plurality of lamination members, or heat treatment such as thermocompression bonding to join 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 of the adhesive layer 12 after photocuring at 100° C. is preferably 5×10 ⁴ Pa or more, more preferably 8×10 ⁴ Pa or more It is more preferably 1×10 ⁵ Pa or more. From the viewpoint of preventing the overflow of the adhesive during heating and preventing the reduction of the adhesive force during heating, the storage modulus at 100°C of the adhesive layer 12 after photohardening is preferably the storage modulus at 50°C 60% or more, more preferably 65% or more, further preferably 70% or more, particularly preferably 75% or more.

The photohardenable adhesive layer 12 can be arbitrarily set at the time of hardening. Since the secondary processing or the processing of the reinforcement film can be performed at any timing between after the laminate 102 is attached to the adherend 70 and before the adhesive layer 12 is light-hardened, it can respond flexibly to the manufacturing steps of the device Preparation time. As described above, since the ultraviolet shielding surface protective film 30 is bonded, the amount of ultraviolet rays included in the fluorescent lamp and the like to reach the adhesive layer 12 is small, so that photocuring of the adhesive layer can be suppressed. Therefore, even when stored for a long time in the semi-finished product in a state where the laminated body 102 is attached to the adherend, the change in the adhesive force of the adhesive layer 12 is small, and it is easy to peel from the adherend 70.

After the surface protective film 30 is peeled off, active light is irradiated from the first film substrate 11 side to harden the first adhesive layer 12, and the reinforcing film 10 is in a state of being firmly adhered to the adherend 70. That is, when it is convenient to accidentally bear external force due to the falling of the device, the placement of heavy objects on the device, the collision of flying objects on the device, etc., the device can also be prevented from being damaged by attaching a reinforcing membrane. In addition, since the adhesive layer is firmly adhered, the reinforcing film is not likely to peel off during long-term use, and has excellent reliability. [Example]

The following examples will be further described, but the present invention is not limited to the following examples.

[Production of Reinforcement Membrane] <Preparation of adhesive composition> Put 95 parts by weight of butyl acrylate as monomer and 5 parts by weight of acrylic acid, and azobisisobutyronitrile (AIBN) as a thermal polymerization initiator in a reaction vessel equipped with a thermometer, stirrer, reflux condenser, and nitrogen introduction tube 0.2 parts by weight and 233 parts by weight of ethyl acetate as a solvent were introduced with nitrogen, and nitrogen substitution was performed for about 1 hour while stirring. Thereafter, it was heated to 60°C and allowed to react for 7 hours to obtain a solution of acrylic polymer.

To a solution of an acrylic polymer, 0.5 parts by weight of a 4-functional epoxy compound ("Tetrad C" manufactured by Mitsubishi Gas Chemical) as a cross-linking agent, and a polyfunctional acrylic monomer manufactured by Shin Nakamura Chemical Industry Co., Ltd. are added. A-200" (polyethylene glycol #200 (n=4) diacrylate; molecular weight 308, functional group equivalent 154 g/eq) 30 parts by weight, and 1-hydroxycyclohexylbenzene as a photo radical initiator Base ketone ("Irgacure 184" manufactured by BASF; absorption maximum wavelength: 246 nm, 280 nm, 333 nm) 1 part by weight and uniformly mixed to prepare an adhesive composition.

<Formation of adhesive layer> On a 75 μm thick polyethylene terephthalate film ("Lumirror S10-75" manufactured by Toray) without surface treatment, the above adhesive composition was applied using a grooved roller so that the thickness after drying became 25 μm Thing. Dry at 130°C for 1 minute to remove the solvent. Then, attach the separator to the coated surface of the adhesive (polyethylene terephthalate film with a thickness of 25 μm subjected to polysiloxane release treatment) The release surface. After that, aging treatment was carried out in an environment of 25° C. for 4 days to perform cross-linking, and a reinforced film with a light-curing adhesive sheet laminated on the film substrate and a separator temporarily adhered thereto was obtained.

[Example 1] <Production of adhesive layer> Add 96.2 parts by weight of 2-ethylhexyl acrylate as a monomer, 3.8 parts by weight of hydroxyethyl acrylate (HEA), and 0.2 parts by weight of AIBN as a polymerization initiator together with 150 parts by weight of ethyl acetate A reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen introduction tube, and at a temperature of 23° C., slowly stir while introducing nitrogen to perform nitrogen replacement. Thereafter, the liquid temperature was maintained at around 60° C. to conduct polymerization reaction for 6 hours and cooled to room temperature, and then diluted with ethyl acetate to prepare a solution (concentration of 25% by weight) of a base polymer having a weight average molecular weight of 540,000.

An isocyanate-based crosslinking agent (isocyanurate body of hexamethylene diisocyanate; "Coronate HX" manufactured by Tosoh) is added to 400 parts by weight of the solution of the base polymer (100 parts by weight of the solid content) as a solid 4 parts by weight of the ingredients, and an ethyl acetate solution of dioctyltin dilaurate ("Embilizer OL-1" manufactured by Tokyo Fine Chemical) as a crosslinking catalyst are stirred at 0.02 parts by weight based on the solid content, Prepare acrylic adhesive solution. The acrylic adhesive solution was applied to a polyimide film (“Kapton 200H” manufactured by Du Pont-Toray) with a thickness of 50 μm, and heated at 130° C. for 20 seconds to form a thickness on the polyimide film. Adhesive layer A of 10 μm.

<Manufacture of surface protection film and bonding to reinforcement film> A spacer with a thickness of 38 μm (“DIAFOIL MRF” manufactured by Mitsubishi Chemical) was temporarily adhered to the adhesive layer, and an adhesive layer A with a thickness of 10 μm was deposited on the polyimide film and temporarily adhered thereon. There is a surface protection film for the separator. The separator was peeled off from the surface protective film, and bonded to the PET film of the reinforcing film to obtain a laminate.

[Example 2] Use a black PET film ("Lumirror X30" manufactured by Toray) with a thickness of 50 μm mixed with black materials instead of a polyimide film as the substrate of the surface protection film to make the surface protection film. Except for this, the laminate was obtained in the same manner as in Example 1. [Example 3] Using a white PET film ("Crisper K1212" manufactured by TOYOBO) with a thickness of 50 μm on the surface instead of the polyimide film as the substrate of the surface protective film, a surface protective film was produced. Except for this, the laminate was obtained in the same manner as in Example 1.

[Example 4] In the preparation of the adhesive composition, in addition to the isocyanate-based crosslinking agent and the crosslinking catalyst, an ultraviolet absorber (2,4-bis-[{4-(4-ethyl Hexoxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-tris; "Tinosorb S" manufactured by BASF) 10 parts by weight. In addition, a transparent PET film (“DIAFOIL T100C50” manufactured by Mitsubishi Chemical) with a thickness of 50 μm was used as the substrate of the surface protection film instead of the polyimide film. Except for these changes, a transparent PET film substrate obtained in the same manner as in Example 1 was fixed with a 10 μm-thick adhesive layer B containing a UV absorber and a surface protection with a spacer temporarily adhered thereon membrane. The separator was peeled off from the surface protective film, and bonded to the PET film of the reinforcing film to obtain a laminate.

[Comparative Example 1] Use a reinforcing film that is not attached to the surface protection film.

[Comparative Example 2] A transparent PET film (“DIAFOIL T100C50” manufactured by Mitsubishi Chemical) with a thickness of 50 μm was used as the base material of the surface protective film instead of the polyimide film to prepare the surface protective film. Except for this, the laminate was obtained in the same manner as in Example 1.

[Evaluation] <Transmittance> The transmission spectrum of the surface protective film was measured using a spectrophotometer ("U-4100" manufactured by Hitachi High-Technologies), and the transmittance at a wavelength of 365 nm and a wavelength of 405 nm was read.

＜Adhesion of separator and surface protective film＞ Cut the laminated body into a sample with a width of 25 mm × a length of 100 mm, hold the end of the separator with a chuck, and peel the separator at 180° at a stretching speed of 0.3 m/min. Intensity). Using the same sample, the end of the surface protective film is held by the chuck, and the adhesion of the surface protective film is measured.

<Adhesion of reinforcing film and polyimide film> A polyimide film (“Kapton 50EN” manufactured by Du Pont-Toray) with a thickness of 12.5 μm is applied via double-sided tape (“No.531” manufactured by Nitto Denko) It was attached to a glass plate to obtain a polyimide film substrate for measurement. The laminated body was cut into a width of 25 mm × a length of 100 mm, and the separator was peeled off from the surface of the reinforcing film, and was attached to the polyimide film substrate for measurement using a hand roller. Place the sample (sample immediately after bonding) on a horizontal table with the polyimide film substrate side as the lower surface and the reinforcement film side as the upper surface, and place it under a fluorescent lamp. week. After that, the surface protective film was peeled off and removed from the laminate, and an LED (Light Emitting Diode) light source with a wavelength of 365 nm was used to irradiate ultraviolet light with a cumulative light amount of 4000 mJ/cm ² from the PET film side of the reinforcing film to make the adhesion The agent layer is light hardened.

For the sample immediately after bonding, the sample that has been left under a fluorescent lamp for 1 week after bonding, and the sample after photocuring the adhesive layer, the ends of the PET film of the reinforcing film are held by the chuck. A 180° peel test was conducted to measure the adhesion of the reinforced film/PI (polyimide) film interface.

Table 1 shows the composition of the surface protection film in the laminates of Examples and Comparative Examples, the light transmittance of the surface protection film, and the adhesion of the reinforcement film/PI film interface, surface protection film, and separator. .

[Table 1]

In any of the examples and comparative examples, immediately after the reinforcement film was attached to the polyimide film as the adherend, the adhesive force was 0.24 N/25 mm, and the reinforcement film was easily peeled from the adherend. In Comparative Example 1 using a reinforcing film that does not have a surface protective film attached, if the reinforcing film is attached to the adherend and stored under a fluorescent lamp for 1 week, the adhesive force increases significantly, making it difficult to peel the reinforced film from the adherend . In Comparative Example 2 in which the surface protective film with the adhesive layer A laminated on the transparent PET film was attached to the reinforcing film, the adhesive force after storage under a fluorescent lamp was observed to increase in the same manner as in Comparative Example 1. .

In Examples 1 to 3 using surface protective films provided with a film substrate having ultraviolet shielding properties, no increase in adhesion was observed even after storage under fluorescent lamps for 1 week. In Example 4 using the surface protective film provided with the adhesive layer B containing the ultraviolet absorber, as in Examples 1 to 3, no increase in adhesion after storage under a fluorescent lamp was observed. In addition, in Examples 1 to 4, after the surface protective film was peeled off and irradiated with ultraviolet rays, it exhibited high adhesion to the adherend.

From these results, it can be seen that by bonding a surface protective film having ultraviolet shielding properties to the film substrate of the reinforcing film, the photohardening of the adhesive due to ultraviolet rays from the fluorescent lamp is suppressed, and the reinforcing film can be stored for a long time A semi-finished product formed by being attached to an adherend. In this way, the layered body with the ultraviolet shielding surface protective film attached to the surface of the reinforcing film can be arbitrarily set from the time after bonding with the adherend to the time before the adhesion force is increased, and the preparation time of the device manufacturing step can be flexibly responded to Wait.

10: Reinforcement membrane 11: membrane substrate 12: Adhesive layer 30: Surface protective film 31: Membrane substrate 32: Adhesive layer 50: spacer 70: adherent 100: Reinforced membrane laminate 102: Reinforced membrane laminate

FIG. 1 is a cross-sectional view showing a laminated structure of a reinforced film laminate. FIG. 2A is a cross-sectional view showing the laminated structure of the laminate after the release film is peeled off. 2B is a cross-sectional view of a semi-finished product formed by bonding an adherend and a laminate. FIG. 2C is a cross-sectional view showing the bonding state of the reinforcing film after peeling the surface protective film.

10: Reinforcement membrane

11: membrane substrate

12: Adhesive layer

30: Surface protective film

31: Membrane substrate

32: Adhesive layer

50: spacer

100: Reinforced membrane laminate

Claims (9)

A laminated body comprising: a reinforcing film provided with a first film substrate and a first adhesive layer fixedly laminated on the first main surface of the first film substrate; and a surface protective film, which is temporarily adhered On the second main surface of the first film substrate; The first adhesive layer includes a photo-curable composition containing a base polymer, a photo hardener, and a photopolymerization initiator; and The surface protective film has ultraviolet shielding properties. The laminated body according to claim 1, wherein the transmittance of light at the absorption maximum wavelength in a region of the surface protection film of the photopolymerization initiator at a wavelength of 450 nm or less is 30% or less. The laminated body according to claim 1 or 2, wherein the light transmittance of the above-mentioned surface protective film at a wavelength of 365 nm is 30% or less. The laminated body according to claim 1 or 2, wherein the light transmittance of the above-mentioned surface protective film at a wavelength of 405 nm is 30% or less. The laminate according to claim 1 or 2, wherein the surface protection film includes a second film base material, and a second adhesive layer fixedly laminated on the second film base material; and The second adhesive layer is temporarily adhered to the second main surface of the first film substrate. The laminate according to claim 1 or 2, wherein the adhesion between the surface protective film and the first film substrate is less than the adhesion between the first adhesive layer and the polyimide film. The laminated body according to claim 1 or 2, further includes a spacer temporarily adhered to the first adhesive layer. The laminate according to claim 7, wherein the adhesion between the surface protective film and the first film substrate is greater than the adhesion between the first adhesive layer and the separator. The laminate according to claim 7, wherein the above-mentioned separator has ultraviolet shielding properties.

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