CN113423575A

CN113423575A - Device with reinforced film, manufacturing method thereof, and reinforcing method

Info

Publication number: CN113423575A
Application number: CN202080013946.5A
Authority: CN
Inventors: 片冈贤一; 仲野武史
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2019-02-12
Filing date: 2020-01-31
Publication date: 2021-09-21
Anticipated expiration: 2040-01-31
Also published as: KR20210126633A; WO2020166400A1; JP2020134540A; JP7257165B2; CN113423575B; TW202043055A

Abstract

The reinforcing film (5) is provided with a photocurable adhesive layer (2) which is fixedly laminated on one main surface of a film substrate (11). An antistatic layer (12) containing a conductive polymer and a binder is provided on the back surface of the film base material. The pressure-sensitive adhesive layer of the reinforcing film is temporarily adhered to the surface of an adherend (9), and then the pressure-sensitive adhesive layer is irradiated with active light from the antistatic layer-formed side of the film base material to photocure the pressure-sensitive adhesive layer. Deterioration of the antistatic layer can be suppressed by not irradiating the antistatic layer with ultraviolet rays having a wavelength of 200 to 280nm when the adhesive layer is photocured.

Description

Device with reinforced film, manufacturing method thereof, and reinforcing method

Technical Field

The present invention relates to a device for bonding and fixing a reinforcing film, which is obtained by laminating a film base material and a photocurable adhesive layer, to a surface thereof, and a method for producing the same. The present invention also relates to a reinforcing method for fixedly laminating a reinforcing film on the surface of an adherend.

Background

An adhesive film may be attached to the surface of an optical device or an electronic device such as a display for the purpose of surface protection, impact resistance, or the like. Such an adhesive film is generally formed by fixedly laminating an adhesive layer on a main surface of a film base and bonding the adhesive layer to a device surface.

In a state before use such as assembly, processing, transportation of equipment, damage or breakage of an adherend can be suppressed by temporarily adhering an adhesive film to the surface of the equipment or an equipment component. The pressure-sensitive adhesive film temporarily attached for temporary surface protection is required to be easily peeled off from an adherend and not to cause adhesive residue on the adherend.

Patent document 1 discloses an adhesive film which is used in a state of being stuck to a surface of a device not only in assembling, processing, transportation, or the like of the device but also in use of the device. Such an adhesive film has a function of enhancing a device by dispersing an impact on the device, imparting rigidity to a flexible device, and the like, in addition to protecting the surface.

When an adhesive film is bonded to an adherend, bonding defects such as mixing of air bubbles and displacement of the bonding position may occur. When a defective bonding occurs, an operation (rework) of peeling the adhesive film from the adherend and bonding another adhesive film is performed. Since the pressure-sensitive adhesive film used as a construction material is designed on the premise of being peeled off from an adherend, it is easy to rework. On the other hand, a reinforcing film based on permanent adhesion is generally not supposed to be peeled off from the device but firmly adhered to the surface of the device, and therefore, rework is difficult.

Patent document 2 discloses an adhesive film having a photocurable adhesive layer on the surface of a hard coat film. The photocurable adhesive is easily peeled off from an adherend because of its low adhesion to the adherend before photocuring, and a film in which the photocurable adhesive is fixedly laminated can be used as a reinforcing film having reworkability.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-132977

Patent document 2: japanese laid-open patent publication No. 2015-217530

Disclosure of Invention

Problems to be solved by the invention

In a reinforcing film in which a photocurable pressure-sensitive adhesive layer is fixedly laminated on a film base, the antistatic layer is provided on the film base, whereby dust adhesion due to electrification (static electricity) and a reduction in workability can be suppressed. Further, by bonding a reinforcing film having an antistatic layer to the surface of an optical device or an electronic device, problems caused by static electricity due to adhesion of dust to the device or the like can be reduced.

However, when a reinforcing film is attached to the surface of an adherend and then the pressure-sensitive adhesive layer of the reinforcing film is irradiated with ultraviolet light to photocure the pressure-sensitive adhesive, the antistatic properties may be degraded. In view of the problem, an object of the present invention is to provide a device which has high antistatic property even after photocuring an adhesive layer and in which a reinforcing film is firmly fixed to the surface of an adherend.

Means for solving the problems

In view of the above problems, the present inventors have found that when ultraviolet light is irradiated to the pressure-sensitive adhesive layer through the film base material having an antistatic layer, the antistatic layer tends to be deteriorated by ultraviolet light having a short wavelength. Based on this knowledge, the method of the present invention performs photocuring of the adhesive layer without irradiating the antistatic layer with ultraviolet light of a short wavelength.

One embodiment of the present invention relates to a reinforcing method for bonding a reinforcing film to a surface of an adherend. The reinforcing film includes a photocurable adhesive layer fixedly laminated on one main surface of a film substrate. An antistatic layer containing a conductive polymer and a binder is provided on the back surface of the film base material. The pressure-sensitive adhesive layer contains a base polymer having a crosslinked structure introduced therein, a photocurable agent having 2 or more polymerizable functional groups, and a photopolymerization initiator.

After the pressure-sensitive adhesive layer of the reinforcing film is temporarily adhered to the surface of an adherend, the pressure-sensitive adhesive layer is irradiated with active light from the second main surface side (the side on which the antistatic layer is formed) of the film base material to photocure the pressure-sensitive adhesive layer. The light curing of the pressure-sensitive adhesive increases the adhesion between the reinforcing film and the adherend.

Deterioration of the antistatic layer can be suppressed by not irradiating the antistatic layer with ultraviolet rays having a wavelength of 200 to 280nm when the adhesive layer is photocured. For example, as a light source for photocuring the pressure-sensitive adhesive layer, a light source such as an LED, a black light lamp, or a chemical lamp, which emits light substantially free of ultraviolet rays (UVC) having a wavelength of 200 to 280nm, may be used.

The adhesion between the reinforcing film and the adherend before photocuring of the pressure-sensitive adhesive layer is preferably 1N/25mm or less, and the adhesion between the reinforcing film and the adherend after photocuring of the pressure-sensitive adhesive layer is preferably 2N/25mm or more. The surface resistance of the second main surface of the film base material after the pressure-sensitive adhesive layer is photocured is preferably 10 times or less the surface resistance of the pressure-sensitive adhesive layer before photocuring (before irradiation with actinic light).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, deterioration of the antistatic layer at the time of photocuring the pressure-sensitive adhesive layer can be suppressed, and therefore, a device having high antistatic property and in which the reinforcing thin film is firmly fixed to the surface of the adherend can be obtained.

Drawings

Fig. 1 is a sectional view showing a laminated structure of a reinforcing film.

Fig. 2 is a sectional view showing a laminated structure of a reinforcing film.

Fig. 3 is a sectional view showing an apparatus to which a reinforcing film is attached.

Fig. 4 is a cross-sectional view showing a state in which a reinforcing film provided with a UVC shielding layer is bonded to a surface of an adherend.

Fig. 5 is a semi-logarithmic graph showing the relationship between the amount of light irradiation and the surface resistance.

Detailed Description

Fig. 1 is a sectional view showing an example of the structure of a reinforcing film. The reinforcing film 5 includes an adhesive layer 2 on one main surface of a film substrate 11. The pressure-sensitive adhesive layer 2 is fixedly laminated on the film base 11. The pressure-sensitive adhesive layer 2 is a photocurable pressure-sensitive adhesive formed of a photocurable composition, and is cured by irradiation of active light such as ultraviolet light, whereby the adhesive strength with an adherend is increased. An antistatic layer 12 is provided on the back surface (surface not provided with the pressure-sensitive adhesive layer 2) of the film base 11.

Fig. 2 is a cross-sectional view of the reinforcing film in which the separator 7 is temporarily attached to the main surface of the pressure-sensitive adhesive layer 2. Fig. 3 is a cross-sectional view showing a state in which a reinforcing film 5 is attached to the surface of a device 9 as an adherend.

The separator 7 is peeled off and removed from the surface of the pressure-sensitive adhesive layer 2, and the exposed surface of the pressure-sensitive adhesive layer 2 is bonded to the surface of the device 9 as an adherend, whereby the reinforcing thin film 5 is bonded to the surface of the device 9. In this state, the pressure-sensitive adhesive layer 2 is in a state in which the reinforcing film 5 (pressure-sensitive adhesive layer 2) is temporarily attached to the device 9 before photocuring. By photocuring the adhesive layer 2, the adhesion at the interface between the device 9 and the adhesive layer 2 is increased, and the device 9 and the reinforcing film 5 are fixed.

"fixed" means that the 2 layers stacked are firmly bonded and cannot or hardly be peeled off from each other at the interface. The term "temporary bonding" means a state in which the 2 layers to be laminated have a low adhesive strength and can be easily peeled off at the interface between the two layers.

In the reinforcing film shown in fig. 2, the film base 11 is fixed to the pressure-sensitive adhesive layer 2, and the separator 7 is temporarily bonded to the pressure-sensitive adhesive layer 2. When the film base material 11 and the separator 7 are peeled off, peeling occurs at the interface between the pressure-sensitive adhesive layer 2 and the separator 7, and the state in which the pressure-sensitive adhesive layer 2 is fixed to the film base material 11 is maintained. No adhesive remains on the release film 7 after peeling.

In the apparatus shown in fig. 3 to which the reinforcing film 5 is attached, the apparatus 9 is temporarily attached to the adhesive layer 2 before the light curing of the adhesive layer 2. If the film base material 11 is peeled from the device 9, peeling occurs at the interface between the pressure-sensitive adhesive layer 2 and the device 9, and the state in which the pressure-sensitive adhesive layer 2 is fixed to the film base material 11 is maintained. Since no adhesive remains on the device 9, rework is easy. After photocuring the pressure-sensitive adhesive layer 2, the adhesive strength between the pressure-sensitive adhesive layer 2 and the device 9 increases, and therefore, it is difficult to peel the film base 11 from the device 9, and if both are peeled, cohesive failure of the pressure-sensitive adhesive layer 2 may occur.

[ constitution of reinforcing film ]

The reinforcing film 5 has the following composition: the adhesive layer 2 is fixedly laminated on the surface of the film base material 11 (base material 1 with antistatic layer) on the back surface of which the antistatic layer 12 is provided, on which the antistatic layer is not formed.

< film substrate >

As the film substrate 11, a plastic film can be used. In order to fix the film base 11 and the pressure-sensitive adhesive layer 2, it is preferable that the surface of the film base 11 on which the pressure-sensitive adhesive layer 2 is provided is not subjected to release treatment.

The film base material has a thickness of, for example, about 4 to 500 μm. The thickness of the film base 11 is preferably 12 μm or more, more preferably 30 μm or more, and further preferably 45 μm or more, from the viewpoint of enhancing the device by imparting rigidity, relaxing impact, and the like. The thickness of the film base 11 is preferably 300 μm or less, more preferably 200 μm or less, from the viewpoint of imparting flexibility to the reinforcing film and improving handling properties. From the viewpoint of compatibility between mechanical strength and flexibility, the film base material 11 preferably has a compressive strength of 100 to 3000kg/cm²More preferably 200 to 2900kg/cm²More preferably, it is300～2800kg/cm²Particularly preferably 400 to 2700kg/cm²。

Examples of the plastic material constituting the film base 11 include polyester resins, polyolefin resins, cyclic polyolefin resins, polyamide resins, polyimide resins, polyether ether ketone, polyether sulfone, and the like. Among the reinforcing films for optical devices such as displays, the film substrate 11 is preferably a transparent film. In the case where the pressure-sensitive adhesive layer 2 is photo-cured by irradiation with actinic light from the film base 11 side, the film base 11 is preferably transparent to actinic light used for curing the pressure-sensitive adhesive layer 2. Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are suitably used from the viewpoint of having both mechanical strength and transparency.

When the pressure-sensitive adhesive layer 2 is photo-cured by irradiation with actinic light from the film base 11 side, the film base 11 preferably has transparency to actinic light used for curing the pressure-sensitive adhesive layer 2. The film base material 11 preferably has a transmittance of 60% or more, more preferably 70% or more, still more preferably 75% or more, and particularly preferably 80% or more, for light having a wavelength of 365 nm. The transmittance of the film base material 11 for light having a wavelength of 405nm is preferably 60% or more, more preferably 70% or more, still more preferably 75% or more, and particularly preferably 80% or more.

An antistatic layer 12 is provided on the back surface (opposite to the surface on which the adhesive layer is provided) of the film base material 11. An antistatic layer may be provided on the surface of the film base 11 to which the pressure-sensitive adhesive layer is attached. The surface of the film base material may be provided with a functional coating such as an easy-adhesion layer, an easy-slip layer, a release layer, a hard coat layer, and an antireflection layer, in addition to the antistatic layer. The antistatic layer 12 can have both of their functions. As described above, in order to fix the film base 11 and the pressure-sensitive adhesive layer 2, it is preferable that no release layer be provided on the surface of the film base 11 on which the pressure-sensitive adhesive layer 2 is provided.

< antistatic layer >

By providing the antistatic layer 12 on the back surface of the film base 11, adhesion of dust to the reinforcing film due to electrification (static electricity) and a reduction in workability can be suppressed. By providing the antistatic layer on the film base material, peeling electrification which may occur when the reinforcing film is peeled from an adherend for rework or patterning can be suppressed. By providing the antistatic layer, it is also possible to suppress electrification that may occur due to friction with a carrying roller, other films, or the like in the manufacturing process of the reinforcing film. In addition, by providing an antistatic layer, the slidability tends to be improved, which contributes to the improvement of the transferability.

By providing the antistatic layer, peeling electrification at the time of peeling the reinforcing film from the adherend for rework or patterning of the reinforcing film can be suppressed. Therefore, it is possible to suppress electrical breakdown of an adherend (for example, an image display panel) and adhesion of dust to the adherend due to static electricity. As described in detail later, by suppressing deterioration of the antistatic layer when the pressure-sensitive adhesive layer is photocured, antistatic properties can be imparted to a device provided with a reinforcing film, and therefore, problems caused by static electricity, such as adhesion of dust to the device, can be reduced.

The antistatic layer contains a binder resin and a conductive polymer as an antistatic component. As the binder resin, various types of resins such as a thermosetting resin, an ultraviolet-curable resin, an electron beam-curable resin, and a two-component hybrid resin can be used. Specific examples of the binder resin include polyester resins, polyurethane resins, acrylic resins, silicone resins, styrene resins, polyamide resins, polyolefin resins, fluorine resins, and alkyd resins. Among these, polyester resins are preferable from the viewpoint of improving the slidability of the reinforcing film.

The polyester-based resin is typically a polycondensate of 1 or more compounds (polycarboxylic acid component) selected from 1 polycarboxylic acid (typically dicarboxylic acid) having 2 or more carboxyl groups in its molecule and its derivatives (such as anhydride, esterified product, and halide of the polycarboxylic acid) and 1 or more compounds (polyol component) selected from 1 polyol (typically diol) having 2 or more hydroxyl groups in its molecule.

Examples of the conductive polymer include polyaniline, polyaniline sulfonic acid, polypyrrole, polythiophene, polyethyleneimine, polysulfone, and allylamine polymers. Among them, a composite of poly (3, 4-ethylenedioxythiophene) and polystyrene sulfonic acid (PEDOT/PSS) is particularly preferable from the viewpoint of high conductivity and excellent dispersibility in the binder.

The thickness of the antistatic layer is, for example, about 5 to 200nm, preferably 10 to 150nm, more preferably 15 to 100nm, and still more preferably 20 to 70 nm. The surface resistance of the antistatic layer-formed surface is, for example, 1X 10⁸Omega is less, preferably 1.0X 10⁷Omega is less, more preferably 1.0X 10⁶Omega is less than or equal to. The surface resistance is generally 1.0X 10³Omega or more or 1.0X 10⁴Omega or more.

To form the antistatic layer 12 on the film base 11, a known coating method such as roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, dip coating, and curtain coating may be used. After coating, heating is preferably performed for the purpose of removing a solvent, curing a resin component, and the like. As a heating method, heating by hot air can be cited. The heating conditions may be appropriately set depending on the composition of the coating layer, the heat resistance of the substrate, and the like, and are usually about 80 to 150 ℃ and about 10 seconds to 10 minutes. If necessary, heat treatment and irradiation with active energy rays such as ultraviolet irradiation may be used in combination for the purpose of promoting the curing reaction of the resin.

The antistatic layer may be formed in the manufacturing process of the film base material. For example, a film having an antistatic layer on the surface of a film base material can be formed by multilayer coextrusion. In addition, the antistatic layer can be formed by heating in the step of forming the film base material. For example, when the film base is a stretched film, the antistatic layer-forming composition may be applied to the surface of the film before stretching or the film after longitudinal stretching, and the solvent may be dried and the resin may be cured by heating in the transverse stretching or simultaneous biaxial stretching by a tenter.

The antistatic layer may contain additives such as a lubricant, a crosslinking agent, an antioxidant, a colorant (pigment, dye, etc.), a fluidity modifier (thixotropic agent, thickener, etc.), a film-forming aid, a surfactant (defoaming agent, dispersant, etc.), and a preservative, as required.

< adhesive layer >

The pressure-sensitive adhesive layer 2 fixedly laminated on the film base 11 is formed of a photocurable composition containing a base polymer, a photocurable agent and a photopolymerization initiator. The pressure-sensitive adhesive layer 2 is easy to rework because of its low adhesion to an adherend such as a device or a device member before photocuring. Since the pressure-sensitive adhesive layer 2 improves the adhesion to an adherend by photocuring, the reinforcing film is less likely to peel off from the surface of the device even when the device is used, and the adhesion reliability is excellent.

The photocurable adhesive is hardly cured in a normal storage environment and is cured by irradiation of active light such as ultraviolet light. Therefore, the reinforcing film having a photocurable adhesive layer has an advantage that the timing of curing of the adhesive layer 2 can be set arbitrarily, and the lead time of the process can be flexibly coped with.

(adhesive Strength)

The adhesion strength of the reinforcing film before photocuring of the pressure-sensitive adhesive layer 2 to the glass plate is preferably less than 1N/25mm, more preferably 0.8N/25mm or less, further preferably 0.7N/25mm or less, and particularly preferably 0.6N/25mm or less, from the viewpoint of facilitating the peeling from the adherend during the rework and preventing the adhesive residue on the adherend after the peeling of the reinforcing film. The adhesion strength of the reinforcing film to the glass plate is preferably 0.03N/25mm or more, more preferably 0.05N/25mm or more, further preferably 0.1N/25mm or more, and particularly preferably 0.2N/25mm or more, from the viewpoint of preventing the reinforcing sheet from peeling from the adherend during storage and handling.

The adhesion of the reinforcing film 5 to the polyimide film is preferably within the above range in a state before the pressure-sensitive adhesive layer 2 is photocured. In a flexible display panel, a flexible printed circuit board (FPC), a device in which a display panel and a circuit board are integrated, a flexible substrate material is used, and a polyimide film is generally used in terms of heat resistance and dimensional stability. The reinforcing film having the adhesive strength of the pressure-sensitive adhesive layer 2 to the polyimide film as the substrate is easily peeled off before the photocuring of the pressure-sensitive adhesive layer 2, and has excellent adhesion reliability after the photocuring.

(thickness)

The thickness of the adhesive layer 2 is, for example, about 1 to 300 μm. The adhesive layer 2 tends to have a higher adhesiveness to an adherend as the thickness thereof is larger. On the other hand, when the thickness of the pressure-sensitive adhesive layer 2 is too large, the fluidity before photocuring is high, and handling may be difficult. Therefore, the thickness of the adhesive layer 2 is preferably 5 to 100 μm, more preferably 8 to 50 μm, still more preferably 10 to 40 μm, and particularly preferably 13 to 30 μm.

(transparency)

In the case where the reinforcing film is used for 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 further preferably 90% or more. The haze of the pressure-sensitive adhesive layer 2 is preferably 2% or less, more preferably 1% or less, further preferably 0.7% or less, and particularly preferably 0.5% or less.

(storage modulus)

Adhesive layer 2 shear storage modulus G 'at 25 ℃ before photocuring'_iPreferably 1X 10⁴～1.2×10⁵Pa. The shear storage modulus (hereinafter abbreviated as "storage modulus") can be determined by: the temperature was measured at a frequency of 1Hz at a temperature rise rate of 5 ℃/min within the range of-50 to 150 ℃ according to the method described in JIS K7244-1, "method for testing dynamic mechanical properties of plastics", and the value at the predetermined temperature was read.

In a substance such as an adhesive exhibiting viscoelasticity, the storage modulus G' is used as an index indicating the degree of hardness. The storage modulus of the adhesive layer has a high correlation with the cohesive force, and there is a tendency that the higher the cohesive force of the adhesive, the greater the anchoring force to the adherend. The storage modulus of the pressure-sensitive adhesive layer 2 before photocuring was 1X 10⁴Pa or more, the pressure-sensitive adhesive has sufficient hardness and cohesive force, and therefore, when the reinforcing film is peeled off from the adherend, adhesive residue is not easily generated on the adherend. In addition, when the storage modulus of the pressure-sensitive adhesive layer 2 is large, the pressure-sensitive adhesive can be inhibited from bleeding out from the end face of the reinforcing film. Of the adhesive layer 2 before photocuringStorage modulus of 1.2X 10⁵When Pa or less, peeling at the interface between the pressure-sensitive adhesive layer 2 and the adherend is easy, and cohesive failure of the pressure-sensitive adhesive layer and adhesive residue on the surface of the adherend are not easily caused even when rework is performed. The pressure-sensitive adhesive layer 2 has a storage modulus G 'at 25 ℃ before photocuring from the viewpoint of improving the reworkability of the reinforcing sheet and suppressing adhesive residue on an adherend at the time of reworking'_iMore preferably 3X 10⁴～1×10⁵Pa, more preferably 4X 10⁴～9.5×10⁴Pa。

(composition)

The adhesive layer 2 is a photocurable composition containing a base polymer, a photocurable agent, and a photopolymerization initiator. From the viewpoint of setting the adhesiveness of the pressure-sensitive adhesive layer 2 before photocuring within an appropriate range, it is preferable that a crosslinked structure be introduced into the base polymer.

(base Polymer)

The base polymer is the main constituent of the adhesive composition. The kind of the base polymer is not particularly limited, and an acrylic polymer, a silicone polymer, a urethane polymer, a rubber polymer, and the like may be appropriately selected. In particular, the pressure-sensitive adhesive composition preferably contains an acrylic polymer as a base polymer, and preferably 50% by weight or more of the pressure-sensitive adhesive composition is an acrylic polymer, from the viewpoint of excellent optical transparency and adhesiveness and easy control of adhesiveness.

As the acrylic polymer, one containing an alkyl (meth) acrylate as a main monomer component can be suitably used. In the present specification, "(meth) acrylic acid" means acrylic acid and/or methacrylic acid.

As the alkyl (meth) acrylate, an alkyl (meth) acrylate in which the number of carbon atoms in the alkyl group is 1 to 20 can be suitably used. The alkyl group of the alkyl (meth) acrylate may be linear or branched. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, dodecyl (meth) acrylate, and the like, Isotetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isostearyl (meth) acrylate, nonadecyl (meth) acrylate, aralkyl (meth) acrylate, and the like.

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, based on the total amount of the monomer components constituting the base polymer.

The 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 and a carboxyl group-containing monomer. The base polymer may have both of a hydroxyl group-containing monomer and a carboxyl group-containing monomer as a monomer component, or may have only one of them. The hydroxyl group and the carboxyl group of the base polymer serve as reactive sites with a 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 preferable to contain a carboxyl group-containing monomer as a copolymerization component of the base polymer. By introducing a crosslinked structure into the base polymer, the cohesive force is improved, the adhesive force of the pressure-sensitive adhesive layer 2 is improved, and the residual adhesive on the adherend during the return tends to be reduced.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and 4- (hydroxymethyl) cyclohexyl) methyl (meth) acrylate. Examples of the carboxyl group-containing monomer include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

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 still more preferably 5 to 20% by weight, based on the total amount of the constituent monomer components, of the base polymer.

The base polymer may contain, as a constituent monomer component, a nitrogen-containing monomer such as N-vinylpyrrolidone, methyl-vinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-acryloylmorpholine, N-vinylcarboxylic acid amides, N-vinylcaprolactam, or the like.

The base polymer may contain monomer components other than those described above. For example, the acrylic base polymer may contain, as a monomer component, a cyano group-containing monomer, a vinyl ester monomer, an aromatic vinyl monomer, an epoxy group-containing monomer, a vinyl ether monomer, a sulfonic group-containing monomer, a phosphoric group-containing monomer, an acid anhydride group-containing monomer, and the like.

The weight average molecular weight of the base polymer is preferably 10 to 500 ten thousand, more preferably 30 to 300 ten thousand, and further preferably 50 to 200 ten thousand. When a crosslinked structure is introduced into the base polymer, the molecular weight of the base polymer is the molecular weight before the crosslinked structure is introduced.

The higher the content of the high Tg monomer component in the base polymer component, the harder the adhesive tends to be. The high Tg monomer is a monomer having a high glass transition temperature (Tg) of a homopolymer. Examples of the monomer having a homopolymer Tg of 40 ℃ or higher include: (meth) acrylic monomers such as dicyclopentanyl methacrylate (Tg: 175 ℃ C.), dicyclopentanyl acrylate (Tg: 120 ℃ C.), isobornyl methacrylate (Tg: 173 ℃ C.), isobornyl acrylate (Tg: 97 ℃ C.), methyl methacrylate (Tg: 105 ℃ C.), 1-adamantyl methacrylate (Tg: 250 ℃ C.), and 1-adamantyl acrylate (Tg: 153 ℃ C.); amide group-containing vinyl monomers such as acryloylmorpholine (Tg: 145 ℃), dimethylacrylamide (Tg: 119 ℃), diethylacrylamide (Tg: 81 ℃), dimethylaminopropylacrylamide (Tg: 134 ℃), isopropylacrylamide (Tg: 134 ℃), hydroxyethylacrylamide (Tg: 98 ℃); acid monomers such as methacrylic acid (Tg: 228 ℃ C.), acrylic acid (Tg: 106 ℃ C.) and the like; n-vinylpyrrolidone (Tg: 54 ℃ C.), etc.

The base polymer preferably contains 1 to 50 wt%, more preferably 3 to 40 wt%, of a monomer having a homopolymer Tg of 40 ℃ or higher, based on the total amount of the constituent monomer components. In order to form an adhesive layer having an appropriate hardness and excellent reworkability, the monomer component of the base polymer preferably contains a monomer component having a homopolymer Tg of 80 ℃ or higher, and more preferably contains a monomer component having a homopolymer Tg of 100 ℃ or higher. The base polymer preferably contains the monomer having a homopolymer Tg of 100 ℃ or higher in an amount of 0.1 wt% or more, more preferably 0.5 wt% or more, still more preferably 1 wt% or more, and particularly preferably 3 wt% or more, based on the total amount of the constituent monomer components.

The base polymer can be obtained by polymerizing the monomer components by various known methods such as solution polymerization, emulsion polymerization, and bulk polymerization. The solution polymerization method is preferable from the viewpoint of balance of properties such as adhesive strength and holding power of the adhesive, cost, and the like. As a solvent for the solution polymerization, ethyl acetate, toluene, or the like can be used. The concentration of the solution is usually about 20 to 80 wt%. As the polymerization initiator used for the solution polymerization, various known ones such as azo-based ones and peroxide-based ones can be used. Chain transfer agents may also be used in order to adjust the molecular weight. The reaction temperature is usually about 50 to 80 ℃ and the reaction time is usually about 1 to 8 hours.

(crosslinking agent)

From the viewpoint of imparting a moderate cohesive force to the adhesive, it is preferable that a crosslinked structure be introduced into the base polymer. For example, a crosslinking agent is added to a solution after polymerization of a base polymer, and the solution is heated as necessary to introduce a crosslinked structure. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents. These crosslinking agents react with functional groups such as hydroxyl groups and carboxyl groups introduced into the base polymer to form a crosslinked structure. From the viewpoint of high reactivity with hydroxyl groups and carboxyl groups of the base polymer and easy introduction of a crosslinked structure, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferable.

As the isocyanate-based crosslinking agent, a polyisocyanate having 2 or more isocyanate groups in 1 molecule can be used. Examples of the isocyanate-based crosslinking agent include: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; aromatic isocyanates such as 2, 4-tolylene diisocyanate, 4' -diphenylmethane diisocyanate, and xylylene diisocyanate; examples of the isocyanate adduct include trimethylolpropane/tolylene diisocyanate trimer adduct (for example, "Coronate L" available from Tosoh corporation), trimethylolpropane/hexamethylene diisocyanate trimer adduct (for example, "Coronate HL" available from Tosoh corporation), and trimethylolpropane adduct of xylylenediisocyanate (for example, "Takenate D110N" available from Mitsui chemical corporation and isocyanurate compound of hexamethylene diisocyanate (for example, "Coronate HX" available from Tosoh corporation).

As the epoxy-based crosslinking agent, a polyfunctional epoxy compound having 2 or more epoxy groups in 1 molecule can be used. The epoxy group of the epoxy crosslinking agent may be a glycidyl group. Examples of the epoxy-based crosslinking agent include N, N, N ', N' -tetraglycidyl m-xylylenediamine, diglycidylaniline, 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, 1, 6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, triglycidyl-tris (2-hydroxyethyl) isocyanurate, and mixtures thereof, Resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and the like. As the epoxy crosslinking agent, commercially available products such as "Denacol" manufactured by Nagase ChemteX Corporation and "Tetrad X" and "Tetrad C" manufactured by Mitsubishi gas chemical company can be used.

The amount of the crosslinking agent to be used may be appropriately adjusted depending on the composition, molecular weight, etc. of the base polymer. The amount of the crosslinking agent is about 0.01 to 10 parts by weight, 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, based on 100 parts by weight of the base polymer. The value obtained by dividing the amount (parts by weight) of the crosslinking agent per 100 parts by weight of the base polymer by the equivalent weight (g/eq) of the functional group of the crosslinking agent is preferably 0.00015 to 0.11, more preferably 0.001 to 0.077, still more preferably 0.003 to 0.055, and particularly preferably 0.0045 to 0.044. When the amount of the crosslinking agent to be used is larger than that of a conventional acrylic transparent pressure-sensitive adhesive for optical use for permanent adhesion, the pressure-sensitive adhesive has moderate hardness, and therefore, the adhesive remains on an adherend during reworking tend to be reduced and reworkability tends to be improved.

To promote the formation of a crosslinked structure, a crosslinking catalyst may be used. Examples of the crosslinking catalyst of the isocyanate crosslinking agent include metal crosslinking catalysts (particularly tin crosslinking catalysts) such as tetra-n-butyl titanate, tetra-isopropyl titanate, iron acetylacetonate, butyltin oxide, dioctyltin dilaurate and dibutyltin dilaurate. Generally, the crosslinking catalyst is used in an amount of 0.05 parts by weight or less relative to 100 parts by weight of the base polymer.

(light curing agent)

The adhesive composition constituting the adhesive layer 2 further contains a light curing agent in addition to the base polymer. The pressure-sensitive adhesive layer 2 formed from the photocurable pressure-sensitive adhesive composition has improved adhesion to an adherend when photocured after being bonded to the adherend.

As the photo-curing agent, a photo-curable monomer or a photo-curable oligomer having 2 or more polymerizable functional groups in 1 molecule can be used. The light-curing agent is preferably a compound having an ethylenically unsaturated bond such as a vinyl group or a (meth) acryloyl group as a polymerizable functional group. In addition, the light curing agent is preferably a compound showing compatibility with the base polymer. From the viewpoint of exhibiting a moderate compatibility with the base polymer, the light curing agent is preferably a substance that is liquid at ordinary temperature.

The compatibility of the base polymer with the photocuring agent is largely influenced by the structure of the compound. The structure and compatibility of the compound can be evaluated by, for example, hansen solubility parameters, and there is a tendency that the smaller the difference in solubility parameters between the base polymer and the light curing agent, the higher the compatibility.

From the viewpoint of high compatibility with the acrylic base polymer, it is preferable to use a polyfunctional (meth) acrylate as the light-curing agent. Examples of the polyfunctional (meth) acrylate 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 di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol poly (meth) acrylate, and mixtures thereof, Dipentaerythritol hexa (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerol di (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, butadiene (meth) acrylate, isoprene (meth) acrylate, and the like.

The compatibility of the base polymer with the photocuring agent is also affected by the molecular weight of the compound. The smaller the molecular weight of the photocurable compound, the higher the compatibility with the base polymer tends to be. The molecular weight of the light-curing agent is preferably 1500 or less, more preferably 1000 or less, from the viewpoint of compatibility with the base polymer.

The type and content of the light curing agent affect the adhesion after light curing. There is a tendency as follows: the smaller the equivalent weight of the functional group (i.e., the larger the number of functional groups per unit molecular weight) and the larger the content of the photo-curing agent, the larger the adhesion after photo-curing. The functional group equivalent (g/eq) of the photocurable agent is preferably 500 or less, and more preferably 450 or less, from the viewpoint of improving the adhesion after photocuring. On the other hand, if the photo-crosslinking density is excessively increased, the viscosity of the adhesive may be decreased, and the adhesive strength may be decreased. Therefore, the functional group equivalent of the photocurable agent is preferably 100 or more, more preferably 130 or more, and further preferably 150 or more.

In the combination of the acrylic base polymer and the polyfunctional acrylate photocurable agent, when the functional group equivalent of the photocurable agent is small, the interaction between the base polymer and the photocurable agent is strong, and the adhesive strength (initial adhesive strength) of the adhesive before photocuring may increase. An excessive increase in initial adhesion may sometimes lead to a decrease in reworkability. From the viewpoint of maintaining the adhesive strength between the pressure-sensitive adhesive layer 2 before photocuring and the adherend within 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 curing agent in the adhesive composition is preferably 10 to 50 parts by weight, more preferably 13 to 45 parts by weight, and still more preferably 15 to 40 parts by weight, based on 100 parts by weight of the base polymer. The photocurable compound is contained in the adhesive composition in the form of an uncured monomer or oligomer, whereby the photocurable adhesive layer 2 can be obtained. In order to allow the light curing agent to be included in the composition in an uncured state, it is preferable to add the light curing agent to a polymer solution obtained by polymerizing a base polymer.

(photopolymerization initiator)

The photopolymerization initiator generates active species by irradiation of active light, and accelerates the curing reaction of the photocuring agent. As the photopolymerization initiator, a photo cation initiator (photoacid generator), a photo radical initiator, a photo anion initiator (photobase generator), or the like can be used depending on the kind of the photo curing agent or the like. When an ethylenically unsaturated compound such as a polyfunctional acrylate is used as the photo-curing agent, a photo radical initiator is preferably used as the polymerization initiator.

The photo radical initiator generates radicals by irradiation of active light, and the radical polymerization reaction of the photo curing agent is promoted by the movement of radicals from the photo radical initiator to the photo curing agent. The photoradical initiator (photoradical generator) is preferably a substance that generates radicals by irradiation with visible light or ultraviolet light having a wavelength of less than 450nm, and examples thereof include hydroxyketones, benzyldimethylketals, aminoketones, acylphosphine oxides, benzophenones, trichloromethyl-containing triazine derivatives, and the like. The photo radical initiator may be used alone or in combination of 2 or more.

When the pressure-sensitive adhesive layer 2 is required to have transparency, the photopolymerization initiator preferably has low sensitivity to light (visible light) having a wavelength of more than 400nm, and for example, an absorption coefficient of 1X 10 at a wavelength of 405nm is preferably used²[mLg^-1cm^-1]The following 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, based on 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, based on 100 parts by weight of the photocurable agent.

(other additives)

The pressure-sensitive adhesive layer 2 may contain additives such as a silane coupling agent, an adhesion promoter, a plasticizer, a softening agent, an anti-deterioration agent, a filler, a colorant, an ultraviolet absorber, an antioxidant, a surfactant, and an antistatic agent, in addition to the above-exemplified components.

[ production of reinforcing film ]

A reinforcing film can be obtained by laminating a photocurable adhesive layer 2 on a film substrate 11. From the viewpoint of productivity, it is preferable to laminate the pressure-sensitive adhesive layer 2 on the surface of the film base material 11 (antistatic layer-attached base material 1) on which the antistatic layer 12 is previously provided, on which no antistatic layer is formed. The pressure-sensitive adhesive layer 2 may be formed directly on the film base 11, or a pressure-sensitive adhesive layer formed in a sheet form on another base may be transferred onto the film base 11.

The adhesive composition is applied to a substrate by roll coating, lick coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, blade coating, air knife coating, curtain coating, lip coating, die coating, or the like, and the solvent is dried and removed as necessary, thereby forming an adhesive layer. As the drying method, an appropriate method can be suitably employed. The heating and drying temperature is preferably 40 to 200 ℃, more preferably 50 to 180 ℃, and still more preferably 70 to 170 ℃. 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.

When the adhesive composition contains a crosslinking agent, it is preferable to carry out crosslinking by heating or aging simultaneously with or after drying of the solvent. The heating temperature and heating time may be appropriately set according to the kind of the crosslinking agent used, and usually, the crosslinking is performed by heating at 20 to 160 ℃ for about 1 minute to 7 days. The heating for drying to remove the solvent may also double as the heating for crosslinking.

By introducing a crosslinked structure into the base polymer, the gel fraction can be increased. There is a tendency as follows: the higher the gel fraction is, the harder the pressure-sensitive adhesive is, and when the reinforcing film is peeled from the adherend by rework or the like, the adhesive residue on the adherend is suppressed. The gel fraction of the pressure-sensitive adhesive layer 2 before photocuring may be 30% or more or 50% or more. The gel fraction before photocuring is preferably 60% or more, more preferably 65% or more, and still more preferably 70% or more. The gel fraction may be 75% or more. When the gel fraction of the pressure-sensitive adhesive layer 2 before photocuring is too large, the anchoring force to an adherend may be reduced, and the initial adhesion may be insufficient. Therefore, the gel fraction of the pressure-sensitive adhesive layer 2 before photocuring is preferably 95% or less, more preferably 90% or less, still more preferably 85% or less, and particularly preferably 80% or less. The gel fraction can be determined as an insoluble component with respect to a solvent such as ethyl acetate, and specifically, can be determined as a weight fraction (unit: weight%) of an insoluble component after the pressure-sensitive adhesive layer is immersed in ethyl acetate at 23 ℃ for 7 days with respect to a sample before immersion. Generally, the gel fraction of a polymer is equal to the degree of crosslinking, and the more crosslinked portions of the polymer, the greater the gel fraction.

The photocurable agent also remains unreacted after the crosslinked structure is introduced into the polymer by the crosslinking agent. Thus, a photocurable adhesive layer 2 including a base polymer and a photocuring agent is formed. When the pressure-sensitive adhesive layer 2 is formed on the film base 11, the separator 7 is preferably provided on the pressure-sensitive adhesive layer 2 for the purpose of protecting the pressure-sensitive adhesive layer 2 and the like. The release film 7 may be attached to the adhesive layer 2 and then crosslinked.

In forming the adhesive layer 2 on another substrate, after drying the solvent, the adhesive layer 2 is transferred onto the film substrate 11, whereby a reinforced film can be obtained. The substrate for forming the adhesive layer may also be used directly as the separator 7.

[ use of reinforcing film ]

< attachment of reinforcing film to adherend >

The reinforcing film is used in close contact with the device or the device component. Since a suitable rigidity can be provided by attaching the reinforcing film, the effects of improving the workability and preventing breakage can be expected. In the manufacturing process of the device, when the reinforcing film is bonded to the semi-finished product, the reinforcing film may be bonded to a large-sized semi-finished product before being cut into a product size. The reinforcing film may also be applied in a roll-to-roll manner on a parent roll of a device manufactured based on a roll-to-roll process.

Since the antistatic layer 12 is provided on the back surface of the film base material 11, dust adhesion due to electrification during roller conveyance can be suppressed. In addition, by providing the antistatic layer 12, there is a tendency that the slidability is improved. Therefore, the film is improved in transferability and windability, and blocking at the time of winding into a roll can be suppressed.

The adherend to which the reinforcing film is bonded is not particularly limited, and various electronic devices, optical devices, and their constituent members are exemplified. With the high integration, reduction in size and weight, and thinning of devices, the thickness of members constituting the devices tends to be reduced. Due to the thinning of the constituent members, bending and curling due to stress and the like at the lamination interface are likely to occur. Further, since the thickness is reduced, the deflection due to its own weight is likely to occur. Since the reinforcing film can be bonded to an adherend with rigidity, bending, curling, bending, and the like due to stress, weight, and the like can be suppressed, and workability can be improved. Therefore, by bonding the reinforcing film to the semi-finished product in the device manufacturing process, defects and disadvantages in the conveyance and processing by the automatic apparatus can be prevented.

The reinforcing film 5 may be attached to the entire surface of the adherend 9, or may be selectively attached only to a portion to be reinforced. In addition, after the reinforcing film is bonded to the entire surface of the adherend, the reinforcing film in the portion where the reinforcing film is not required to be reinforced may be cut, and the reinforcing film may be peeled and removed from the surface of the adherend. Alternatively, the reinforcing thin film may be peeled and removed from the adherend in a portion where light is not irradiated after the pressure-sensitive adhesive is cured by selectively irradiating the portion where reinforcement is required with light. Since the reinforcing film is temporarily attached to the surface of the adherend before the light curing of the pressure-sensitive adhesive layer 2, the reinforcing film 5 can be easily peeled and removed from the surface of the adherend 9.

< photocuring of adhesive layer >

After the reinforcing film 5 is bonded to the adherend 9, the pressure-sensitive adhesive layer 2 is irradiated with active light such as ultraviolet light from a light source (not shown) disposed on the antistatic layer-attached substrate 1 side (upper side in fig. 3), thereby photo-curing the pressure-sensitive adhesive layer 2. By photocuring the pressure-sensitive adhesive layer 2, the reinforcing film 5 is firmly adhered to the adherend 9. Even when an external force is accidentally applied by dropping the equipment, placing a heavy object on the equipment, colliding the equipment with a flying object, or the like, the reinforcing film is bonded to prevent the equipment from being damaged. Further, since the antistatic layer-attached substrate 1 is firmly adhered to the surface of the adherend 9 with the pressure-sensitive adhesive layer 2 formed of a photo-cured product of the photocurable pressure-sensitive adhesive composition interposed therebetween, the reinforcing film is less likely to peel off even in long-term use, and is excellent in reliability.

When the pressure-sensitive adhesive layer 2 is photocured, if the pressure-sensitive adhesive layer 2 is irradiated with active light from a light source located on the antistatic layer-attached substrate 1 side, the active light is also irradiated to the antistatic layer 12. When ultraviolet light having a short wavelength such as UVC (wavelength of 200 to 280nm) is irradiated to an antistatic layer containing a conductive polymer, antistatic performance tends to be lowered. Therefore, it is preferable that the adhesive layer is photo-cured so that the antistatic layer is not irradiated with ultraviolet rays having a wavelength of 200 to 280 nm.

The intensity (irradiation intensity) of ultraviolet rays having a wavelength of 200 to 280nm irradiated to the antistatic layer is preferably 20 μ W/cm²Hereinafter, more preferably 10. mu.W/cm²Hereinafter, it is more preferably 5. mu.W/cm²The concentration is preferably 1. mu.W/cm²The following. The irradiation intensity of ultraviolet rays of 200 to 280nm to the antistatic layer is preferably 0.

For example, if a light source substantially not containing ultraviolet rays having a wavelength of 200 to 280nm is used as a light source when the adhesive layer is photocured, deterioration of the antistatic layer can be suppressed. Examples of the light source that radiates light substantially free of ultraviolet rays having a wavelength of 200 to 280nm include an LED, a black light lamp, and a chemical lamp. In the case of using an LED, the emission peak wavelength is preferably in the range of 300 to 450nm in order to efficiently photocure the adhesive layer while suppressing deterioration of the antistatic layer. The emission peak wavelength of the LED may be appropriately selected depending on the absorption wavelength of the photopolymerization initiator contained in the pressure-sensitive adhesive layer, or a plurality of LEDs having different emission peak wavelengths may be used in combination.

The irradiation intensity of light having a wavelength of 300 to 450nm is preferably 10mW/cm when the adhesive layer is photocured from the viewpoint of improving the photocuring efficiency²More preferably 20mW/cm²More preferably 30mW/cm²The above. The cumulative irradiation amount may be selected so that photocuring of the adhesive is sufficiently performed, and for example, the cumulative irradiation amount may be100mJ/cm²The above. The cumulative dose of light having a wavelength of 300 to 450nm may be 300mJ/cm²Above 500mJ/cm²Above 700mJ/cm²Above 1000mJ/cm²Above or 1500mJ/cm²The above.

The adhesion between the reinforcing film and the adherend after photocuring the pressure-sensitive adhesive layer is preferably 2N/25mm or more, more preferably 3N/25mm or more, and still more preferably 5N/25mm or more. The adhesion between the reinforcing film and the adherend after photocuring the pressure-sensitive adhesive layer may be 6N/25mm or more, 8N/25mm or more, 10N/25mm or more, 12N/25mm or more, or 13N/25mm or more. The adhesion between the pressure-sensitive adhesive layer and the adherend after photocuring is preferably 5 times or more, more preferably 8 times or more, and still more preferably 10 times or more the adhesion between the pressure-sensitive adhesive layer and the adherend before photocuring. The adhesive strength between the pressure-sensitive adhesive layer and the adherend after photocuring may be 20 times or more, 30 times or more, 40 times or more, or 50 times or more the adhesive strength between the pressure-sensitive adhesive layer and the adherend before photocuring.

The surface resistance of the surface of the base material 1 on which the antistatic layer 12 is formed after photocuring the pressure-sensitive adhesive layer is preferably 1 × 10⁸Omega is less, more preferably 1.0X 10⁷Omega is less than or equal to. The surface resistance of the antistatic layer 12-formed surface of the substrate 1 after photocuring the adhesive layer may be 1.0 × 10⁶Omega is less than or equal to. The surface resistance of the antistatic layer-forming surface after photocuring the pressure-sensitive adhesive layer is preferably 10 times or less, more preferably 5 times or less, further preferably 3 times or less, and particularly preferably 2 times or less, the surface resistance of the pressure-sensitive adhesive layer before photocuring (before irradiation of the pressure-sensitive adhesive layer with actinic light through the film base). As described above, by suppressing the irradiation of ultraviolet rays having short wavelengths such as UVC to the antistatic layer, the deterioration of the antistatic layer can be suppressed, and the increase in surface resistance can be suppressed.

As a method for preventing the antistatic layer from being irradiated with ultraviolet rays having a wavelength of 200 to 280nm, a method of shielding ultraviolet rays having a wavelength of 200 to 280nm radiated from a light source so as not to reach the antistatic layer is exemplified, in addition to a method of selecting a light source. For example, even when a light source in which radiation light includes UVC such as a low-pressure mercury lamp, a high-pressure mercury lamp, or a metal halide lamp is used, deterioration due to irradiation of UVC to the antistatic layer can be suppressed by disposing a UVC shielding material that absorbs and/or reflects UVC between the light source and the reinforcing film.

For example, as shown in fig. 4, the pressure-sensitive adhesive layer 2 may be photo-cured by irradiating the surface of the antistatic layer 12 with active light while disposing a UVC shielding layer 17 that absorbs and/or reflects ultraviolet rays having a wavelength of 200 to 280 nm. Examples of the UVC shielding layer include a resin material that absorbs UVC, glass, a band pass filter, a cut filter (long pass filter), and the like. The UVC blocking layer 17 may be removed after the adhesive layer is photocured.

The UVC shielding material is not required to be in contact with the antistatic layer, and is arranged between the light source and the antistatic layer. Further, UVC shielding material may be used as the material constituting the light source. For example, quartz is generally used for an ultraviolet source such as a high-pressure mercury lamp, and UVC can be shielded by replacing it with soda-lime glass, borosilicate glass, or the like.

Examples

The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples below.

[ production of reinforcing film ]

< preparation of film base Material with antistatic layer >

The following components (a) to (D) were added to a mixed solvent of water and ethanol, and stirred and mixed for about 20 minutes to obtain an antistatic treatment liquid having a solid content of about 0.3%.

(A) An aqueous solution (called "Clevios P" by Heraeus) containing 0.5% of poly (3, 4-ethylenedioxythiophene) as a conductive polymer and 0.8% of polystyrene sulfonate (number average molecular weight: 15 ten thousand) was prepared: 50 parts by weight of a solid content

(B) A25% aqueous dispersion of a saturated copolymerized polyester resin ("Vylonal MD-1480" manufactured by Toyo Boseki Co., Ltd.): based on 100 parts by weight of solid components

(C) Aqueous dispersion of carnauba wax: 40 parts by weight (as a slip agent) based on solid content

(D) Melamine crosslinking agent: 10 parts by weight

The above treatment liquid was applied to one side of a polyethylene terephthalate film (manufactured by Toray corporation, "LUMIRROR S10-75") having a thickness of 75 μm without surface treatment by a bar coater, and dried by heating at 130 ℃ for 30 seconds to form an antistatic layer having a thickness of 40 nm.

< formation of adhesive layer >

In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet tube, 95 parts by weight of butyl acrylate and 5 parts by weight of acrylic acid as monomers, 0.2 part by weight of Azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and 233 parts by weight of ethyl acetate as a solvent were charged, and nitrogen gas was introduced and replaced with nitrogen gas for about 1 hour while stirring. Then, the mixture was heated to 60 ℃ and reacted for 7 hours to obtain a solution of an acrylic polymer having a weight average molecular weight of 60 ten thousand.

To a solution of an acrylic polymer, 0.5 part by weight of a 4-functional epoxy compound ("tetra C" manufactured by mitsubishi gas chemical corporation) as a crosslinking agent, 30 parts by weight of "a-200" (polyethylene glycol #200 (n-4) diacrylate; molecular weight 308, functional group equivalent 154g/eq) as a polyfunctional acrylic monomer, and 1 part by weight of a photopolymerization initiator ("Irgacure 651" manufactured by BASF) as a polyfunctional acrylic monomer were added and mixed uniformly to prepare an adhesive composition.

The adhesive composition was applied to the surface of the film base material on which the antistatic layer was not formed, using a fountain roll (fountain roll) so that the thickness after drying became 25 μm. After drying at 130 ℃ for 1 minute to remove the solvent, the release-treated surface of a separator (a polyethylene terephthalate film having a thickness of 25 μm and a surface subjected to silicone release treatment) was bonded to the coated surface of the adhesive. Then, curing treatment was performed at 25 ℃ for 4 days to effect crosslinking, thereby obtaining a reinforced film in which a photocurable adhesive layer was fixedly laminated on a film base and a separator was temporarily attached thereon.

[ bonding to an adherend and photocuring of adhesive ]

A polyimide film (DU PONT-TORAY Co., Ltd., "Kapton 50 EN" manufactured by Ltd.) having a thickness of 12.5 μm was attached to a glass plate via a double-sided adhesive tape (No. 531 manufactured by Nitto electric Co., Ltd.) to obtain a substrate for testing. The separator was peeled off from the surface of the reinforcing film cut to a width of 25mm × length of 100mm, and the resultant was bonded to the polyimide film of the test substrate by a hand-press roll, and then irradiated with ultraviolet light from the reinforcing film side (the antistatic layer-formed surface of the film base) to photocure the adhesive layer.

As an ultraviolet source, an LED light source having a wavelength of 365nm was used in example 1, a black light lamp was used in example 2, and a high-pressure mercury lamp was used in comparative example 1. In each case, the cumulative quantity of light of the active light with a wavelength of 290-430 nm reaches 2000J/cm²、4000mJ/cm²Or 8000mJ/cm²The irradiation time is adjusted to carry out photocuring of the adhesive layer.

[ evaluation ]

< surface resistance >

The surface resistance of the sample immediately after the test substrate was bonded (before the irradiation with ultraviolet light) and the sample after the adhesive layer was photocured by the irradiation with ultraviolet light was measured under conditions of a temperature of 23 ℃ and a relative humidity of 50% by bringing a probe (Model 152P-2P, manufactured by TREK) into contact with the surface of the film base (antistatic layer) using a resistivity meter (Model 152-1, manufactured by TREK), and applying a voltage of 10V for 10 seconds.

< adhesion >

The cumulative light amount of the sample immediately after bonding to the test substrate (before ultraviolet irradiation) and the cumulative light amount passed through the test substrate was 8000mJ/cm²The sample in which the pressure-sensitive adhesive layer was photo-cured was subjected to a 180 ° peel test of the reinforcing film at a tensile rate of 300 mm/min while holding the end of the reinforcing film with a jig, and the test force of the peel test was used as the adhesion.

< evaluation results >

Fig. 5 shows a semilogarithmic graph obtained by plotting the relationship between the light irradiation amount (accumulated light amount) and the surface resistance in the examples and comparative examples. In addition, 8000mJ/cm of radiation will be irradiated²The surface resistance and adhesive strength of the antistatic layer after ultraviolet irradiation, and the increase rate before and after irradiation are shown in table 1. In addition, the irradiation with ultraviolet light is performedThe surface resistance before the wire was 1.5X 10⁵Omega, the adhesive force is 0.16N/25 mm.

[ Table 1]

It was found that 8000mJ/cm of light was irradiated with either light source²The adhesive strength after the irradiation of the active light is increased by 80 times or more before the irradiation of the ultraviolet ray, and the reinforcing film is firmly adhered to the polyimide film by photocuring the adhesive.

It is found that in comparative example 1 in which the adhesive layer was photo-cured using a high-pressure mercury lamp, the surface resistance increased greatly with an increase in the amount of light irradiated, and the antistatic layer was deteriorated by ultraviolet irradiation. On the other hand, it is found that in examples 1 and 2 using a light source not containing ultraviolet rays having a short wavelength, the antistatic performance is maintained since the change in surface resistance is small even after the adhesive is photocured.

From the above results, it was found that by irradiating the pressure-sensitive adhesive layer with light through the antistatic layer-attached base material using a light source substantially not containing ultraviolet rays having a short wavelength, the pressure-sensitive adhesive can be photocured while suppressing deterioration of the antistatic layer, and a device having excellent antistatic properties and a reinforced film firmly adhered to an adherend can be obtained.

Description of the reference numerals

1 base material with antistatic layer

11 film base material

12 antistatic layer

2 adhesive layer

5 reinforced film

7 isolating film

9 adherend

17 UVC shielding layer

Claims

1. A method for manufacturing a device having a reinforcing thin film bonded to a surface thereof, comprising the steps of:

preparing a reinforcing film having a film base having a first main surface and a second main surface and a photocurable adhesive layer fixedly laminated on one main surface of the film base,

after temporarily adhering the adhesive layer of the reinforcing film to the surface of an adherend,

irradiating the pressure-sensitive adhesive layer with actinic light from a light source located on the second principal surface side of the film base to photocure the pressure-sensitive adhesive layer, thereby increasing the adhesive strength between the reinforcing film and the adherend,

an antistatic layer containing a conductive polymer and a binder is provided on the second main surface of the film base,

the pressure-sensitive adhesive layer contains a base polymer having a crosslinked structure introduced therein, a photo-curing agent having 2 or more polymerizable functional groups, and a photo-polymerization initiator,

when the adhesive layer is photocured, the antistatic layer is not irradiated with ultraviolet rays having a wavelength of 200 to 280 nm.

2. The method for manufacturing a device according to claim 1, wherein, when the adhesive layer is photocured, the irradiation light from the light source is substantially free of ultraviolet rays having a wavelength of 200 to 280 nm.

3. The method of manufacturing a device according to claim 1 or 2, wherein the surface resistance of the second main surface of the film base material after the irradiation of the active light to the adhesive layer is 10 times or less the surface resistance before the irradiation of the active light.

4. The method for manufacturing a device according to any one of claims 1 to 3, wherein the adhesion between the reinforcing film and the adherend before irradiation of the pressure-sensitive adhesive layer with active light is 1N/25mm or less.

5. The method of manufacturing a device according to any one of claims 1 to 4, wherein the adhesion force between the reinforcing film and the adherend after irradiation of the pressure-sensitive adhesive layer with active light is 2N/25mm or more.

6. The method for manufacturing a device according to any one of claims 1 to 5, wherein a gel fraction of the adhesive layer before photocuring is 60% or more.

7. The method for manufacturing a device according to any one of claims 1 to 6, wherein the adhesive layer before photocuring contains 10 to 50 parts by weight of the photocuring agent per 100 parts by weight of the base polymer.

8. A device with a reinforced film attached to the surface,

the reinforcing film comprises a film base having a first main surface and a second main surface, and an adhesive layer fixedly laminated on one main surface of the film base,

the adhesive layer of the reinforced film is adhered to a surface of a device,

the pressure-sensitive adhesive layer is a photocurable reactant of a composition containing a base polymer having a crosslinked structure introduced thereinto, a photocurable agent having 2 or more polymerizable functional groups, and a photopolymerization initiator,

the adhesive strength between the reinforcing film and an adherend is 2N/25mm or more,

the surface resistance of the second main surface of the film substrate was 1.0X 10⁷Omega is less than or equal to.

9. A reinforcing method for bonding a reinforcing film to a surface of an adherend, comprising the steps of:

10. The reinforcing method according to claim 9, wherein the irradiation light from the light source is substantially free of ultraviolet rays having a wavelength of 200 to 280nm when the adhesive layer is photocured.