CN113423573A - Reinforced film - Google Patents
Reinforced film Download PDFInfo
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- CN113423573A CN113423573A CN202080013960.5A CN202080013960A CN113423573A CN 113423573 A CN113423573 A CN 113423573A CN 202080013960 A CN202080013960 A CN 202080013960A CN 113423573 A CN113423573 A CN 113423573A
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J7/00—Adhesives in the form of films or foils
- C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
- C09J7/38—Pressure-sensitive adhesives [PSA]
- C09J7/381—Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
- C09J7/385—Acrylic polymers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/16—Nitrogen-containing compounds
- C08K5/34—Heterocyclic compounds having nitrogen in the ring
- C08K5/3467—Heterocyclic compounds having nitrogen in the ring having more than two nitrogen atoms in the ring
- C08K5/3477—Six-membered rings
- C08K5/3492—Triazines
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
- C09J11/02—Non-macromolecular additives
- C09J11/06—Non-macromolecular additives organic
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
- C09J133/04—Homopolymers or copolymers of esters
- C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J201/00—Adhesives based on unspecified macromolecular compounds
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J201/00—Adhesives based on unspecified macromolecular compounds
- C09J201/02—Adhesives based on unspecified macromolecular compounds characterised by the presence of specified groups, e.g. terminal or pendant functional groups
- C09J201/06—Adhesives based on unspecified macromolecular compounds characterised by the presence of specified groups, e.g. terminal or pendant functional groups containing oxygen atoms
- C09J201/08—Carboxyl groups
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
- C09J4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J7/00—Adhesives in the form of films or foils
- C09J7/20—Adhesives in the form of films or foils characterised by their carriers
- C09J7/22—Plastics; Metallised plastics
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J7/00—Adhesives in the form of films or foils
- C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
- C09J7/38—Pressure-sensitive adhesives [PSA]
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Adhesive Tapes (AREA)
- Adhesives Or Adhesive Processes (AREA)
- Laminated Bodies (AREA)
Abstract
The invention provides a reinforcing film which is easy to rework immediately after being bonded with an adherend, can be firmly bonded with the adherend, and can set the time from bonding with the adherend to increasing the bonding force at will. The reinforcing film (10) is provided with a pressure-sensitive adhesive layer (2) which is fixedly laminated on one main surface of a film base (1). The adhesive layer is formed from a photocurable composition containing a base polymer, a photocuring agent, a photoradical initiator, and an ultraviolet absorber. The photo radical initiator preferably has an absorption maximum in a wavelength range of 310nm to 370 nm.
Description
Technical Field
The invention relates to a reinforced film attached to the surface of equipment.
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.
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.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2017-132977
Patent document 2: international publication No. 2015/163115
Patent document 3: japanese laid-open patent publication No. 2015-217530
Disclosure of Invention
Problems to be solved by the invention
After a reinforcing film obtained using a pressure-sensitive adhesive whose adhesive strength to an adherend changes with time is bonded to the adherend, inspection, rework, and the like of the bonded state need to be performed for a predetermined time until the adhesive strength increases. In addition, when a reinforcing film is attached to the entire surface of a device or a device member and then the reinforcing film is removed from a partial region, the processing is required to be performed until the adhesion force is increased, and therefore, an adhesive film in which the adhesion force changes with time is not sufficient in flexibility with respect to a lead time (lead time) of a process.
On the other hand, the photocurable adhesive can be cured at an arbitrary timing after being bonded to an adherend, and can flexibly cope with the lead time of the process. However, if a reinforcing film provided with a photocurable pressure-sensitive adhesive is bonded to an adherend and the semi-finished product in a state before photocuring of the pressure-sensitive adhesive is stored for a long period of time, the adhesive strength with the adherend is increased without irradiation of light for curing, and the reinforcing film may be difficult to peel from the adherend. In view of the above problem, an object of the present invention is to provide a reinforcing film which is less likely to cause a change in the adhesive strength of a photocurable adhesive with time even when a semi-finished product in a state of being bonded to an adherend is stored for a long period of time.
Means for solving the problems
The reinforcing film of the present invention includes a pressure-sensitive adhesive layer fixedly laminated on one main surface of a film base. The adhesive layer is formed from a photocurable composition containing a base polymer, a photocuring agent, a photoradical initiator, and an ultraviolet absorber. The photocurable composition constituting the adhesive layer preferably contains 0.1 to 10 parts by weight of an ultraviolet absorber per 100 parts by weight of the base polymer. Examples of the ultraviolet absorber include triazine compounds.
From the viewpoint of suppressing generation of radicals by the photo radical initiator due to light of a fluorescent lamp or the like, it is preferable to use a photo radical initiator having a maximum absorption in a wavelength range of 310nm to 370nm and showing no maximum absorption at a long wavelength of more than 380nm as the photo radical initiator.
The light transmittance of the adhesive layer at a wavelength of 350nm is, for example, about 3 to 70%. The reinforcing film as a laminate of the adhesive layer and the film base material has a light transmittance of, for example, about 3 to 70% at a wavelength of 350 nm. The light transmittance of the adhesive layer at the maximum absorption wavelength of the photo radical initiator is preferably about 3 to 70%. The light transmittance of the reinforced film under the maximum absorption wavelength of the photo-radical initiator is preferably about 3-70%.
As the base polymer of the adhesive layer, for example, an acrylic polymer can be used. The base polymer of the adhesive layer preferably has a crosslinked structure introduced therein. For example, the base polymer contains a hydroxyl group-containing monomer and/or a carboxyl group-containing monomer as a monomer unit, and a crosslinking agent such as a polyfunctional isocyanate compound or a polyfunctional epoxy compound is bonded to these functional groups to introduce a crosslinked structure.
The light curing agent of the adhesive layer is, for example, a polyfunctional (meth) acrylate. The equivalent weight of the functional group of the light curing agent is preferably about 100 to 500 g/eq.
Preferably, the adhesion of the reinforcing film to the polyimide film after photocuring the pressure-sensitive adhesive layer is 5 times or more the adhesion to the polyimide film before photocuring the pressure-sensitive adhesive layer.
ADVANTAGEOUS EFFECTS OF INVENTION
The reinforcing film of the present invention is formed of a photocurable composition via a pressure-sensitive adhesive layer, and after bonding to an adherend, the pressure-sensitive adhesive layer is photocured, thereby increasing the adhesion to the adherend. The adhesive strength between the sheet and an adherend before photocuring is small, so that reworking is easy, and the sheet exhibits high adhesive strength after photocuring. The pressure-sensitive adhesive composition can suppress a photocuring reaction by light from a fluorescent lamp or the like in a storage environment by further containing an ultraviolet absorber in addition to the base polymer, the photocuring agent, and the photoradical initiator. Therefore, the reinforcing film can be stored for a long period of time in a state before being bonded to an adherend and before being photocured after being bonded to the adherend, and the lead time of the process can be flexibly coped with.
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.
Detailed Description
Fig. 1 is a sectional view showing one embodiment of a reinforcing film. The reinforcing film 10 includes an adhesive layer 2 on one main surface of a film substrate 1. The pressure-sensitive adhesive layer 2 is fixedly laminated on one main surface of the film base 1. 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.
Fig. 2 is a cross-sectional view of the reinforcing film in which the separator 5 is temporarily attached to the main surface of the pressure-sensitive adhesive layer 2. Fig. 3 is a sectional view showing a state where the reinforcing film 10 is attached to the surface of the apparatus 20.
The separator 5 is peeled off from the surface of the adhesive layer 2, and the exposed surface of the adhesive layer 2 is bonded to the surface of the device 20, whereby the reinforcing film 10 is bonded to the surface of the device 20. In this state, the pressure-sensitive adhesive layer 2 is in a state where the reinforcing film 10 (pressure-sensitive adhesive layer 2) is temporarily stuck to the device 20 before photocuring. By photocuring the adhesive layer 2, the adhesion at the interface of the device 20 and the adhesive layer 2 is increased, and the device 20 is fixed to the reinforcing film 10.
"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 1 is fixed to the pressure-sensitive adhesive layer 2, and the separator 5 is temporarily bonded to the pressure-sensitive adhesive layer 2. When the film base 1 and the separator 5 are peeled off, peeling occurs at the interface between the pressure-sensitive adhesive layer 2 and the separator 5, and the state in which the pressure-sensitive adhesive layer 2 is fixed to the film base 1 is maintained. No adhesive remains on the release film 5 after peeling.
In the case of the apparatus shown in fig. 3 to which the reinforcing film 10 is attached, the apparatus 20 is temporarily attached to the adhesive layer 2 before the adhesive layer 2 is photo-cured. If the film base material 1 is peeled from the device 20, peeling occurs at the interface between the pressure-sensitive adhesive layer 2 and the device 20, and the state in which the pressure-sensitive adhesive layer 2 is fixed to the film base material 1 is maintained. Since no adhesive remains on the device 20, rework is easy. After the pressure-sensitive adhesive layer 2 is photocured, the adhesive strength between the pressure-sensitive adhesive layer 2 and the device 20 increases, and therefore, it is difficult to peel the film base material 1 from the device 20, and if both are made of glass, cohesive failure of the pressure-sensitive adhesive layer 2 may occur.
[ film base ]
As the film substrate 1, a plastic film can be used. In order to fix the film base 1 and the pressure-sensitive adhesive layer 2, it is preferable that the surface of the film base 1 to which the pressure-sensitive adhesive layer 2 is attached is not subjected to release treatment.
The film base material has a thickness of, for example, about 4 to 500 μm. The film base 1 preferably has a thickness of 12 μm or more from the viewpoint of reinforcing the apparatus by imparting rigidity, relaxing impact, or the likeMore preferably 30 μm, and still more preferably 45 μm or more. The thickness of the film base 1 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 1 preferably has a compressive strength of 100 to 3000kg/cm2More preferably 200 to 2900kg/cm2More preferably 300 to 2800kg/cm2Particularly preferably 400 to 2700kg/cm2。
Examples of the plastic material constituting the film base 1 include polyester resins, polyolefin resins, cyclic polyolefin resins, polyamide resins, polyimide resins, and the like. In a reinforcing film for optical devices such as displays, the film base 1 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 substrate 1 side, the film substrate 1 preferably has transparency to actinic light used for curing the pressure-sensitive adhesive layer. 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 transparency is required for the reinforcing film (for example, for optical applications such as displays), the total light transmittance of the film base 1 is preferably 80% or more, more preferably 85% or more, and still more preferably 90% or more. The haze of the film base 1 is preferably 2% or less, more preferably 1% or less, further preferably 0.7% or less, and particularly preferably 0.5% or less. When the pressure-sensitive adhesive layer 2 is cured by irradiation with actinic light from the film substrate 1 side, the film substrate 1 preferably has little absorption of actinic light. For example, when the pressure-sensitive adhesive layer 2 is cured by irradiating ultraviolet light from the film substrate 1 side, the light transmittance of the film substrate 1 at a wavelength of 350nm is preferably 20% or more, and more preferably 30% or more. The light transmittance of the film base 1 at a wavelength of 350nm may be 40% or more, 50% or more, 60% or more, or 70% or more. In the case where the pressure-sensitive adhesive layer is cured by irradiation with actinic light from the adherend side, the adherend may be transparent to actinic light, and the film base material 1 may be opaque to actinic light.
The surface of the film base material 1 may be provided with functional coatings such as an easy-adhesion layer, an easy-slip layer, a release layer, an antistatic layer, a hard coat layer, and an antireflection layer. As described above, in order to fix the film base 1 and the pressure-sensitive adhesive layer 2, it is preferable that no release layer be provided on the surface of the film base 1 on which the pressure-sensitive adhesive layer 2 is provided.
[ adhesive layer ]
The pressure-sensitive adhesive layer 2 fixedly laminated on the film base 1 is a photocurable composition containing a base polymer, a photocurable agent and a photoradical initiator. 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.
The pressure-sensitive adhesive layer 2 has a small adhesive force with an adherend before photocuring, and therefore is easy to rework. When the pressure-sensitive adhesive layer 2 is irradiated with active light such as ultraviolet light, radicals are generated from the photo radical initiator, and the radical polymerization reaction (photo-curing) of the photo-curing agent improves the adhesive strength with the adherend. Therefore, the reinforcing film is less likely to peel off from the surface of the device when the device is used, and the adhesion reliability is excellent.
The photocurable adhesive is cured by irradiation with ultraviolet rays or the like. Therefore, the pressure-sensitive adhesive layer 2 formed from the photocurable pressure-sensitive adhesive composition has an advantage that the timing of curing can be set arbitrarily, and the lead time of the process can be flexibly coped with. On the other hand, in a state before the reinforcing film is used or before the reinforcing film is photocured after being bonded to an adherend, radicals may be generated from the photo radical initiator by light from a fluorescent lamp or the like in a storage environment.
Since the amount of radicals generated by light from a fluorescent lamp or the like is sufficiently smaller than the amount of radicals generated by ultraviolet irradiation at the time of photocuring, the photocuring reaction hardly proceeds even when the composition is left for a short time under a fluorescent lamp. However, if the reinforcing film is stored under a fluorescent lamp for a long period of time, the amount of radicals generated from the photo radical initiator is increased by the light of the fluorescent lamp, and the influence thereof may not be ignored. Specifically, the radical generated by the photo radical initiator causes polymerization of the photo curing agent to proceed, and the adhesive strength of the pressure-sensitive adhesive to increase, and the reinforcing film may be difficult to peel off from the adherend.
The photocurable composition constituting the pressure-sensitive adhesive layer 2 of the reinforced film of the present invention further contains an ultraviolet absorber in addition to the base polymer, the photocurable agent and the photoradical initiator. By adding an ultraviolet absorber that absorbs light (ultraviolet rays) in a wavelength region overlapping with a light absorption band (excitation wavelength) of the photo radical initiator, the change in adhesion is small even when the reinforcing film is stored under a fluorescent lamp for a long period of time, and the adhesion can be appropriately increased upon light irradiation.
< composition of adhesive >
Preferred embodiments will be described below in order for the base polymer, the photo-curing agent, the photo-radical initiator, and the ultraviolet absorber constituting the photocurable composition.
(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, a polymer containing an alkyl (meth) acrylate as a main monomer component is preferably 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 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 and a carboxyl group-containing monomer. 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) cyclohexylmethyl (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 acrylic base polymer. The content of the hydroxyl group-containing (meth) acrylate is particularly preferably in the above range.
The acrylic 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, and the like.
The acrylic base polymer may contain other monomer components than those described above. The acrylic base polymer may contain, as a monomer component, for example, 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 adhesive properties of the adhesive before photocuring are easily affected by the constituent components and molecular weight of the base polymer. There is a tendency that the larger the molecular weight of the base polymer, the harder the adhesive. The weight average molecular weight of the acrylic 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 acrylic base polymer preferably contains 1 to 50% by weight, more preferably 3 to 40% by weight 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 acrylic 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 acrylic polymer as a base polymer can be obtained by polymerizing the above 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 used 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 include organic metals such as tetra-n-butyl titanate, tetra-isopropyl titanate, iron acetylacetonate, butyltin oxide, dioctyltin dilaurate and dibutyltin dilaurate. In general, the crosslinking catalyst is used in an amount of 1 part 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 light curing agent, a compound having 2 or more ethylenically unsaturated bonds in 1 molecule is preferable. 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. By making the light curing agent compatible with the base polymer and uniformly dispersed in the composition, the pressure-sensitive adhesive layer 2 having high transparency can be formed while securing a contact area with an adherend. Further, by making the base polymer and the light curing agent exhibit appropriate compatibility, the crosslinked structure by the light curing agent can be easily introduced uniformly into the pressure-sensitive adhesive layer 2 after the light curing, and the adhesive strength with the adherend tends to be increased appropriately.
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. Among these, polyethylene glycol di (meth) acrylate or polypropylene glycol di (meth) acrylate is preferable, and polyethylene glycol di (meth) acrylate is particularly preferable, from the viewpoint of excellent compatibility with the acrylic base polymer.
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. From the viewpoint of compatibility with the base polymer, the molecular weight of the light-curing agent 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 2 before photocuring, the characteristics of the base polymer are a main determinant of adhesiveness. Therefore, if the base polymers of the adhesive composition are the same, the difference in the adhesive properties of the adhesive layer before photocuring is small even if the kind of the photocuring agent is different. The type and content of the light curing agent mainly affect the adhesion of the light-cured adhesive layer. 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 more the difference in the adhesive strength between before and after photo-curing can be obtained.
The photocurable agent has a functional group equivalent (g/eq) of preferably 500 or less, more preferably 400 or less, still more preferably 300 or less, and particularly preferably 200 or less, from the viewpoint of high compatibility with the base polymer and improvement in adhesion after photocuring. On the other hand, if the functional group equivalent of the photocurable agent is too small, the crosslinking point density of the pressure-sensitive adhesive layer after photocuring may increase, and the adhesiveness may decrease. Therefore, the functional group equivalent of the photocurable agent 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 photocuring agent, when the functional group equivalent of the photocuring agent is small, the interaction between the base polymer and the photocuring agent is strong, and the initial adhesion tends to increase. In the application of the present invention, the reworkability may be lowered due to an excessive increase in the initial adhesion. 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 with respect to 100 parts by weight of the base polymer. When the amount of the light curing agent is in the above range, the adhesiveness of the pressure-sensitive adhesive layer after light curing to an adherend can be adjusted to an appropriate range. The content of the light curing agent is more preferably 15 to 45 parts by weight, and still more preferably 20 to 40 parts by weight, based on 100 parts by weight of the base polymer.
(photo radical 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 transparency is required for the pressure-sensitive adhesive layer 2, the photo radical initiator preferably has low sensitivity to light (visible light) having a wavelength of more than 400nm, and for example, an absorption coefficient of 1 × 10 at a wavelength of 405nm is preferably used2[mLg-1cm-1]The following photo radical initiator. Further, if a photo radical initiator having low sensitivity to visible light is used, the amount of photo radicals generated by external light in a storage environment is small, and therefore, the storage stability of the reinforcing film can be improved.
From the viewpoint of improving the storage stability of the reinforcing film, it is preferable to use a photo radical initiator which does not exhibit maximum absorption at a wavelength of more than 380 nm. Photo radical initiators that exhibit absorption maxima at wavelengths greater than 380nm readily absorb light from fluorescent lamps (mostly bright lines of mercury at 405 nm) to generate photo radicals. When the maximum wavelength of light absorption of the photo radical initiator is 370nm or less, the amount of radicals generated by light in a storage environment such as a fluorescent lamp is small. Therefore, even when the reinforcing film is exposed to a fluorescent lamp for a long period of time, a high effective concentration of the photo radical initiator can be maintained. In addition, from the viewpoint of suppressing the generation of photo radicals by ultraviolet rays (mainly, bright mercury rays having a wavelength of 365 nm) from fluorescent lamps and improving the storage stability of the reinforcing film, the photo radical initiator preferably does not exhibit the maximum absorption at a wavelength longer than 360 nm.
The photoradical initiator contained in the pressure-sensitive adhesive layer preferably has a maximum wavelength of light absorption of 370nm or less, more preferably 355nm or less, in order to increase storage stability and improve adhesion to an adherend by light irradiation even after long-term storage. On the other hand, in order to improve the photocuring efficiency by ultraviolet irradiation, the photo radical initiator preferably has a light maximum absorption at a wavelength of more than 310 nm. In order to improve the storage stability of the reinforcing film, the photo radical initiator contained in the pressure-sensitive adhesive layer 2 is preferably a substance having no maximum absorption at a wavelength longer than 380nm and having a maximum absorption at a wavelength in the range of 310 to 370nm, and more preferably a substance having no maximum absorption at a wavelength longer than 360nm and having a maximum absorption at a wavelength in the range of 310 to 355 nm. The maximum absorption wavelength of the photo-radical initiator is more preferably 315 to 350nm, and particularly preferably 320 to 345 nm.
The content of the photo radical initiator in the adhesive layer 2 is preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.7 part by weight, and further preferably 0.03 to 0.5 part by weight, based on 100 parts by weight of the base polymer. The content of the photo radical initiator in the adhesive layer 2 is preferably 0.005 to 0.5 part by weight, more preferably 0.01 to 0.4 part by weight, and still more preferably 0.02 to 0.3 part by weight, based on 100 parts by weight of the photo curing agent. If the content of the photo radical initiator in the pressure-sensitive adhesive layer is too small, the photo-curing reaction may not sufficiently proceed even if ultraviolet rays are irradiated. If the content of the photo radical initiator is too large, the adhesion tends to increase due to the photo curing reaction in the storage environment even when the ultraviolet absorber is added, and it may be difficult to rework the reinforced film.
(ultraviolet absorber)
The ultraviolet absorber has an effect of suppressing a photocuring reaction in a storage environment of the reinforcing film. In the composition containing the ultraviolet ray preventive agent in addition to the photo radical initiator, even when light having a wavelength sensitive to the photo radical initiator is irradiated from a fluorescent lamp or the like, the amount of light absorbed by the photo radical initiator is relatively small because the amount of light absorbed by the ultraviolet ray absorbent is large. Therefore, the generation of photoradicals can be suppressed, and photocuring (radical polymerization reaction of a photocuring agent) by light from a fluorescent lamp or the like can be suppressed.
Examples of the ultraviolet absorber include benzotriazole ultraviolet absorbers, benzophenone ultraviolet absorbers, triazine ultraviolet absorbers, salicylate ultraviolet absorbers, and cyanoacrylate ultraviolet absorbers. The triazine-based ultraviolet absorber is preferred in view of high absorptivity of ultraviolet light having a long wavelength of 320 to 400nm and excellent compatibility with the base polymer and the photocuring agent. Among triazine ultraviolet absorbers, hydroxyl group-containing triazine ultraviolet absorbers are preferred, and hydroxyphenyl triazine ultraviolet absorbers are particularly preferred.
As the ultraviolet absorber, commercially available ones can be used. Examples of commercially available triazine ultraviolet absorbers include: the reaction product of 2- (4, 6-bis (2, 4-dimethylphenyl) -1,3, 5-triazin-2-yl) -5-hydroxyphenyl with [ (alkoxy) methyl ] oxetane (manufactured by BASF as "TINUVIN 400"), the reaction product of 2- (2, 4-dihydroxyphenyl) -4, 6-bis- (2, 4-dimethylphenyl) -1,3, 5-triazine with (2-ethylhexyl) -glycidic acid ester (manufactured by BASF as "TINUVIN 405"), (2, 4-bis [ 2-hydroxy-4-butoxyphenyl ] -6- (2, 4-dibutoxyphenyl) -1,3, 5-triazine (manufactured by BASF as "TINUVIN 460"), 2- (4, 6-Diphenyl-1, 3, 5-triazin-2-yl) -5- [ (hexyl) oxy ] -phenol (manufactured by BASF as "TINUVIN 577"), 2- (2-hydroxy-4- [ 1-octyloxycarbonylethoxy ] phenyl) -4, 6-bis (4-phenylphenyl) -1,3, 5-triazine (manufactured by BASF as "TINUVIN 479"), and the like.
The content of the ultraviolet absorber in the adhesive layer 2 is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the base polymer. The content of the ultraviolet absorber may be 0.3 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, 2 parts by weight or more, 2.5 parts by weight or more, or 3 parts by weight or more, relative to 100 parts by weight of the base polymer. The content of the ultraviolet absorber may be 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, or 5 parts by weight or less with respect to 100 parts by weight of the base polymer. The content of the ultraviolet absorber may be 5 times or more, 10 times or more, 30 times or more, or 50 times or more relative to the content of the photo radical initiator. The content of the ultraviolet absorber may be 5000 times or less, 3000 times or less, 1000 times or less, 500 times or less, 300 times or less, or 100 times or less with respect to the content of the photo radical initiator.
From the viewpoint of suppressing the polymerization reaction of the reinforcing film in the tubular state, it is preferable that the content of the ultraviolet absorber is large. On the other hand, if the content of the ultraviolet absorber is too large, most of the excitation light is absorbed by the ultraviolet absorber even when ultraviolet irradiation is performed for photocuring, and the amount of light absorbed by the photo radical initiator decreases, so that the generation of photo radicals may be inhibited, and curing may be insufficient even when ultraviolet irradiation is performed. Therefore, in order to suppress an increase in adhesion due to a reaction in a storage environment and to increase the adhesion by appropriately performing a photocuring reaction upon light irradiation, the content of the ultraviolet absorber is preferably in the above range.
In order to suppress photocuring (radical polymerization reaction of the photo-curing agent) by light from a fluorescent lamp or the like, it is preferable that the absorption wavelength of the ultraviolet absorber overlaps with the light absorption band (excitation wavelength) of the photo-radical initiator. The light transmittance of the pressure-sensitive adhesive layer containing an ultraviolet absorber at the maximum absorption wavelength of the photo radical initiator is preferably 70% or less, more preferably 65% or less, and still more preferably 60% or less. As the amount of the ultraviolet absorber added increases, the light transmittance of the adhesive layer at the maximum absorption wavelength of the photo radical initiator becomes smaller. The light transmittance of the adhesive layer at the maximum absorption wavelength of the photo radical initiator is more preferably 50% or less, and still more preferably 40% or less. The light transmittance of the adhesive layer at the maximum absorption wavelength of the photo radical initiator may be 35% or less, 30% or less, 25% or less, or 20% or less.
On the other hand, when the light transmittance of the pressure-sensitive adhesive layer at the maximum absorption wavelength of the photo radical initiator is too small, the amount of light absorbed by the ultraviolet absorber is large, and the amount of light absorbed by the photo radical initiator is small even when ultraviolet light is irradiated for photocuring, so that the amount of photo radicals generated is small, and therefore, there are cases where photocuring of the pressure-sensitive adhesive is not sufficiently performed, or the time required for photocuring becomes long, and the curing efficiency is lowered. Therefore, the light transmittance of the adhesive layer at the maximum absorption wavelength of the photo radical initiator is preferably 3% or more, more preferably 4% or more, and further preferably 5% or more. The light transmittance of the adhesive layer at the maximum absorption wavelength of the photo radical initiator may be 7% or more, 10% or more, 13% or more, or 15% or more.
By adjusting the kind and/or the addition amount of the ultraviolet absorber according to the kind (maximum absorption wavelength) of the photo radical initiator, the light transmittance of the adhesive layer at the maximum absorption wavelength of the photo radical initiator can be adjusted to be within the above range. When the photo radical initiator has a plurality of absorption maxima, the light transmittance of the adhesive layer at the absorption maximum wavelength closest to 365nm (bright mercury line of a fluorescent lamp) is preferably set to the above range.
As described above, the photo radical initiator is preferably a substance having the maximum absorption in the wavelength range of 310 to 370 nm. When the photo radical initiator has a maximum absorption in a wavelength range of 310 to 370nm, the light transmittance of the adhesive layer at the maximum absorption wavelength in the wavelength range is preferably in the above range.
In addition, the light transmittance of the pressure-sensitive adhesive layer at a wavelength of 350nm is preferably 3 to 70%, more preferably 4 to 65%, and further preferably 5 to 60%, from the viewpoint of suppressing photocuring of the pressure-sensitive adhesive by light in a storage environment such as a fluorescent lamp regardless of the maximum absorption wavelength of the photo radical initiator and ensuring curing efficiency at the time of light irradiation. The light transmittance of the adhesive layer at a wavelength of 350nm may be 50% or less, 40% or less, 35% or less, 30% or less, 25% or less, or 20% or less. The light transmittance of the adhesive layer at a wavelength of 350nm may be 7% or more, 10% or more, 13% or more, or 15% or more.
(other additives)
The pressure-sensitive adhesive layer may contain additives such as a silane coupling agent, an adhesion promoter, a plasticizer, a softening agent, an antioxidant, an anti-deterioration agent, a filler, a colorant, a surfactant, and an antistatic agent in addition to the above-exemplified components within a range not to impair the characteristics of the present invention.
[ production of reinforcing film ]
A reinforcing film can be obtained by laminating a photocurable adhesive layer 2 on a film substrate 1. The pressure-sensitive adhesive layer 2 may be formed directly on the film base 1, or a pressure-sensitive adhesive layer formed in a sheet form on another base may be transferred onto the film base 1.
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.
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.
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 is preferably 30% or more, more preferably 50% or more, still more preferably 60% or more, and particularly preferably 65% or more. The gel fraction of the pressure-sensitive adhesive layer 2 before photocuring may be 70% or more or 75% or more.
Since the adhesive contains an unreacted photo-curing agent, the gel fraction of the adhesive layer 2 before photo-curing is generally 90% or less. If 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 85% or less, and more 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. Further, the larger the amount of the light curing agent, the smaller 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 1, the separator 5 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 5 may be attached to the adhesive layer 2 and then crosslinked.
In the case where the adhesive layer 2 is formed on another substrate, after the solvent is dried, the adhesive layer 2 is transferred onto the film substrate 1, whereby a reinforced film can be obtained. The substrate for forming the adhesive layer may also be used directly as the separator 5.
As the separator 5, a plastic film such as polyethylene, polypropylene, polyethylene terephthalate, or polyester film can be preferably used. The thickness of the separator is usually 3 to 200 μm, preferably about 10 to 100 μm. The contact surface between the separator 5 and the pressure-sensitive adhesive layer 2 is preferably subjected to a release treatment with a release agent such as silicone, fluorine, long-chain alkyl, or fatty acid amide, or silica powder. When the surface of the separator 5 is subjected to the release treatment, peeling occurs at the interface between the pressure-sensitive adhesive layer 2 and the separator 5 when the film base 1 and the separator 5 are peeled off, and the state in which the pressure-sensitive adhesive layer 2 is fixed to the film base 1 is maintained.
The reinforcing film used for optical applications such as displays is preferably high in visible light transparency, and the total light transmittance of the reinforcing film 10 is preferably 80% or more, more preferably 85% or more, and still more preferably 90% or more. The haze of the film substrate 1 of the reinforcing film 10 is preferably 2% or less, more preferably 1% or less, further preferably 0.7% or less, and particularly preferably 0.5% or less.
The light transmittance of the reinforcing film 10 having the pressure-sensitive adhesive layer 2 fixedly laminated on the film base 1 at a wavelength of 350nm is preferably 3 to 70%. The light transmittance of the reinforcing film 10 at a wavelength of 350nm is more preferably 4 to 65%, and still more preferably 5 to 60%. The light transmittance of the enhancement film 10 at a wavelength of 350nm may be 50% or less, 40% or less, 35% or less, 30% or less, 25% or less, or 20% or less. The light transmittance of the reinforcing film 10 at a wavelength of 350nm may be 7% or more, 10% or more, 13% or more, or 15% or more.
When the photo radical initiator contained in the adhesive layer 2 has a maximum absorption at a wavelength of 310 to 370nm, the light transmittance of the reinforcing film 10 at the maximum absorption wavelength is preferably 3 to 70%, more preferably 4 to 65%, and further preferably 5 to 60%. The light transmittance of the enhancement film 10 at the maximum absorption wavelength of the photo radical initiator may be 50% or less, 40% or less, 35% or less, 30% or less, 25% or less, or 20% or less. The light transmittance of the reinforcing film 10 at the maximum absorption wavelength of the photo radical initiator may be 7% or more, 10% or more, 13% or more, or 15% or more.
As described above, by setting the light transmittances of the film base 1 and the pressure-sensitive adhesive layer 2 to predetermined ranges, the reinforcing film 10 having the light transmittance in the above-described range can be obtained. Specifically, the film base 1 is preferably a material having a permeability to near ultraviolet rays from the viewpoint of improving the photocuring efficiency of the pressure-sensitive adhesive layer 2. On the other hand, from the viewpoint of suppressing photocuring of the pressure-sensitive adhesive layer 2 in a storage state, it is preferable to add an ultraviolet absorber to the pressure-sensitive adhesive layer 2 so as to have ultraviolet absorbability.
[ use of reinforcing film ]
The reinforcing film of the present invention is used in a state of being attached to a device or a device constituting member. The pressure-sensitive adhesive layer 2 of the reinforcing film 10 is fixed to the film base material 1, and the adhesive strength to an adherend is small after the lamination to the adherend and before the photocuring. Therefore, the reinforcing film can be easily peeled off from the adherend before photocuring, and the reworkability is excellent. Further, before the photocuring, processing such as cutting the reinforcing film and removing the reinforcing film from a part of the surface of the adherend can be easily performed.
The adherend to which the reinforcing film is bonded is not particularly limited, and various electronic devices, optical devices, and components thereof are exemplified. The reinforcing film may be attached to the entire surface of the adherend, or may be selectively attached only to a portion to be reinforced. Further, after the reinforcing film is bonded to the entire surface of the adherend, the reinforcing film may be cut and peeled off from the portion where the reinforcing film is not required to be reinforced. Since the reinforcing film is temporarily attached to the surface of the adherend before photocuring, the reinforcing film can be easily peeled and removed from the surface of the adherend.
< Properties of adhesive layer before photocuring >
(adhesion)
The adhesive strength between the pressure-sensitive adhesive layer 2 before photocuring and the adherend is preferably 5N/25mm or less, more preferably 3N/25mm or less, and still more preferably 2N/25mm or less, from the viewpoint of facilitating peeling from the adherend and preventing adhesive residue on the adherend after peeling of the reinforcing film. The adhesive strength between the pressure-sensitive adhesive layer 2 before photocuring and an adherend may be 1.5N/25mm or less or 1N/25mm or less. From the viewpoint of preventing peeling of the reinforcing sheet during storage and handling, the adhesive strength between the pressure-sensitive adhesive layer 2 before photocuring and an adherend is preferably 0.005N/25mm or more, more preferably 0.01N/25mm or more, further preferably 0.02N/25mm or more, and particularly preferably 0.03N/25mm or more.
The reinforcing film preferably has an adhesive strength to the polyimide film in a state before photocuring the pressure-sensitive adhesive layer within the above range. 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 polyimide film is generally used in terms of the use of a flexible substrate material, heat resistance, and dimensional stability. The reinforcing film having the adhesive strength of the pressure-sensitive adhesive layer to the polyimide film as the substrate is easily peeled off before photocuring of the pressure-sensitive adhesive layer, and has excellent adhesion reliability after photocuring.
(storage modulus)
In a substance exhibiting viscoelasticity such as an adhesive, 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. The storage modulus of the pressure-sensitive adhesive layer 2 before photocuring was 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 during reworking'iMore preferably 3X 104～1×105Pa, more preferably 4X 104～9.5×104Pa。
< photocuring of adhesive layer >
After the reinforcing film is attached to the adherend, the pressure-sensitive adhesive layer 2 is irradiated with active light to photocure the pressure-sensitive adhesive layer. Examples of the active rays include ultraviolet rays, visible light, infrared rays, X-rays, α -rays, β -rays, and γ -rays. From the viewpoint of suppressing curing of the pressure-sensitive adhesive layer in a storage state and facilitating curing, ultraviolet rays are preferred as the active light rays. The irradiation intensity and the irradiation time of the active light may be appropriately set according to the composition, the thickness, and the like of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer 2 may be irradiated with the actinic rays from either one of the film base 1 side and the adherend side, or from both sides.
< Properties of pressure-sensitive adhesive layer after photocuring >
(adhesion)
From the viewpoint of adhesion reliability in actual use of the device, the adhesion between the pressure-sensitive adhesive layer 2 and the adherend after photocuring is preferably 2N/25mm or more, more preferably 3N/25mm or more, and still more preferably 5N/25mm or more. The adhesive strength between the reinforcing film and the adherend after photocuring the pressure-sensitive adhesive layer can be 6N/25mm or more, 8N/25mm or more, 10N/25mm or more, 12N/25mm or more, or 13N/25mm or more. The reinforcing film preferably has a bonding strength of the pressure-sensitive adhesive layer after photocuring in the above range with respect to the polyimide film. The adhesion between the pressure-sensitive adhesive layer 2 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 2 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.
Storage modulus G 'at 25 ℃ after photocuring of adhesive layer 2'fPreferably 1.5X 105Pa or above. The storage modulus of the photo-cured adhesive layer 2 was 1.5X 105When Pa or more is used, the adhesion to the adherend increases with an increase in the cohesive force, and high adhesion reliability can be obtained. On the other hand, when the storage modulus is too large, the adhesive is difficult to wet and spread, and the contact area with the adherend becomes small. Further, since the stress dispersibility of the pressure-sensitive adhesive is lowered, the peeling force tends to be easily propagated at the bonding interface, and the adhesive strength with the adherend tends to be lowered. Thus, adhesive layer 2 has a storage modulus G 'at 25 ℃ after photocuring'fPreferably 2X 106Pa or less. G 'from the viewpoint of improving the adhesion reliability of the reinforcing sheet after photocuring the pressure-sensitive adhesive layer'fMore preferably 1.1X 105～1.2×106Pa, more preferably 1.2X 105～1×106Pa。
Storage modulus of adhesive layer 2 at 25 ℃ before and after photocuringOf G'f/G’iPreferably 2 or more. G'fIs G'iAt least 2 times, the increase of G' by photocuring is large, and both reworkability before photocuring and bonding reliability after photocuring can be achieved. G'f/G’iMore preferably 4 or more, still more preferably 8 or more, and particularly preferably 10 or more. G'f/G’iThe upper limit of (C) is not particularly limited, but G'f/G’iIf the amount is too large, initial adhesion failure due to small G 'before photocuring or adhesion reliability due to too large G' after photocuring is likely to be caused. Therefore, G'f/G’iPreferably 100 or less, more preferably 40 or less, further preferably 30 or less, and particularly preferably 25 or less.
An adherend with a reinforcing film attached thereto may be subjected to heat treatment such as autoclave treatment for the purpose of improving affinity at the lamination interface of a plurality of laminate members, thermocompression bonding for bonding circuit members, or the like. Preferably, when such heat treatment is performed, the adhesive between the reinforcing film and the adherend does not flow from the end face.
The storage modulus of the pressure-sensitive adhesive layer 2 after photocuring at 100 ℃ is preferably 5 × 10 from the viewpoint of suppressing bleeding of the pressure-sensitive adhesive during heating at high temperature4Pa or more, more preferably 8X 104Pa or more, more preferably 1X 105Pa or above. From the viewpoint of preventing the bleeding of the adhesive during heating and also preventing the decrease in adhesive strength during heating, the storage modulus at 100 ℃ of the pressure-sensitive adhesive layer 2 after photocuring is preferably 60% or more, more preferably 65% or more, further preferably 70% or more, and particularly preferably 75% or more of the storage modulus at 50 ℃.
[ use form of reinforcing film ]
The reinforcing film of the present invention is used by being bonded to constituent members (semi-finished products) of various devices and completed devices. 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 equipment that is manufactured based on a roll-to-roll process.
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.
In the automatic conveyance, the semifinished product of the conveyance object inevitably comes into contact with the conveyance arm, the pin, and the like. Further, in order to adjust the shape and remove unnecessary portions, a cutting process of a half product may be performed. In a highly integrated, small, lightweight, and thin apparatus, when the apparatus is brought into contact with a conveyor or the like and cut, damage due to local stress concentration is likely to occur. In a manufacturing process of a device in which a plurality of members are laminated, not only the members are laminated in order, but also a part of the members, process materials, and the like are peeled and removed from a semi-finished product in some cases. When the member is thinned, stress is locally concentrated at the peeled portion and its vicinity, and breakage or dimensional change may occur. Since the reinforcing film has stress dispersibility due to the pressure-sensitive adhesive layer, when the reinforcing film is bonded to the object to be conveyed and the object to be processed, appropriate rigidity can be imparted, and stress can be relaxed and dispersed, whereby troubles such as cracks, peeling, dimensional changes, and the like can be suppressed.
In this manner, by bonding the reinforcing film of the present invention, a suitable rigidity can be imparted to a semi-finished product as an adherend, and stress can be relaxed and dispersed, so that various disadvantages that may occur in the production process can be suppressed, production efficiency can be improved, and yield can be improved. Further, since the reinforcing film is easily peeled from the adherend before photocuring the pressure-sensitive adhesive layer, it is easily reworked even when a lamination or adhesion failure occurs.
The pressure-sensitive adhesive layer 2 of the reinforcing film of the present invention is photocurable, and the timing of curing can be set arbitrarily. Since the treatment such as the rework and the processing of the reinforcing film can be performed at any timing during a period from when the reinforcing film is attached to the adherend to when the pressure-sensitive adhesive is photocured, the lead time of the device manufacturing process can be flexibly coped with. As described above, since the pressure-sensitive adhesive layer contains the ultraviolet absorber in addition to the photo-curing agent and the photo radical initiator, it is difficult to perform photo-curing by light of a fluorescent lamp or the like. Therefore, even when the reinforcing film is stored for a long period of time in a state in which the reinforcing film is attached to an adherend, the reinforcing film can be easily peeled off from the adherend before photocuring, and the time required for the step to be performed can be flexibly adjusted.
Examples
The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples.
Examples 1 to 4 and comparative example 1
< preparation of adhesive composition >
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 (BA) and 5 parts by weight of Acrylic Acid (AA) 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 the acrylic polymer solution were added 0.5 part by weight of a 4-functional epoxy compound ("tetra C" manufactured by Mitsubishi gas chemical Co., Ltd.) as a crosslinking agent, 30 parts by weight of "NK Ester A200" (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; maximum absorption wavelength: 250nm, 340 nm). Further, in examples 1 to 4, a triazine-based ultraviolet absorber (TINUVIN 405, manufactured by BASF) was added in an amount shown in Table 1 and mixed uniformly to obtain adhesive compositions.
< coating and crosslinking of adhesive composition >
The adhesive composition was applied to a polyethylene terephthalate film (LUMIRROR S10, manufactured by Toray corporation) having a thickness of 75 μm and not subjected to surface treatment, using a supply 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, the cured film was cured at 25 ℃ for 4 days and crosslinked to obtain a reinforced film in which a photocurable adhesive sheet was fixedly laminated on a film base and a separator was temporarily attached thereon.
Examples 5 to 8 and comparative example 2
< preparation of adhesive composition >
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet tube, 63 parts by weight of 2-ethylhexyl acrylate (2EHA), 9 parts by weight of Methyl Methacrylate (MMA), 13 parts by weight of hydroxyethyl acrylate (HEA), and 15 parts by weight of N-vinyl pyrrolidone (NVP) as monomers, 0.2 parts by weight of AIBN as a thermal polymerization initiator, and 233 parts by weight of ethyl acetate as a solvent were charged, and nitrogen gas was purged 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 120 ten thousand.
< preparation of adhesive composition >
To the acrylic polymer solution were added 2.5 parts by weight of a 75% ethyl acetate solution of trimethylolpropane adduct of xylylenediisocyanate as a crosslinking agent (manufactured by mitsui chemical corporation, trademark D110N) as a solid component, 30 parts by weight of NK Ester APG700 (polypropylene glycol #700(n ═ 12) diacrylate; molecular weight 808, functional group equivalent 404g/eq) as a polyfunctional acrylic monomer, and 1 part by weight of a photopolymerization initiator (manufactured by BASF, Irgacure 184; maximum absorption wavelength: 246nm, 280nm, 333 nm). In examples 5 to 8, triazine-based ultraviolet absorbers (TINUVIN 405, BASF) were added in the amounts shown in Table 1 and mixed uniformly to obtain adhesive compositions.
< coating and crosslinking of adhesive composition >
In the same manner as in examples 1 to 4 and comparative example 1, a reinforcing film was prepared in which a photocurable adhesive sheet was fixedly laminated on a film base and a separator was temporarily adhered thereon by applying an adhesive composition, drying by heating, and crosslinking.
[ measurement of adhesive Strength ]
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 polyimide film substrate for measurement. 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 a polyimide film substrate for measurement by a hand pressure roller to prepare a test sample before photocuring. From the reinforcing film side (PET film side) of the test sample before photocuring, a cumulative light amount of 4000mJ/cm was irradiated with an LED light source having a wavelength of 365nm2The adhesive layer was photocured, and the obtained sample was used as a test sample after photocuring. Using these test samples, the end of the polyethylene terephthalate film of the reinforcing film was held by a jig, and a 180 ℃ peel test of the reinforcing film was carried out at a tensile rate of 300 mm/min to measure the peel strength.
< evaluation of adhesive Strength of reinforcing film after 4 weeks from bonding >
The reinforcing sheet was bonded to a polyimide film substrate for measurement, and after standing for 4 weeks in a bright environment at a temperature of 23 ℃ and an illuminance of 620 lux of light from a fluorescent lamp, the peel strength was measured.
Table 1 shows the composition of the adhesive of each reinforcing film, and the results of measuring the adhesion before and after photocuring and the adhesion after 4 weeks (before photocuring).
[ Table 1]
In both examples and comparative examples, the adhesive force was 0.4N/25mm or less immediately after the lamination with the polyimide film substrate, and the polyimide film could be easily peeled off. Further, when photocuring is performed immediately after bonding, the adhesive strength increases, and the polyimide film substrate is firmly bonded.
In both examples and comparative examples, the adhesive strength was increased after 4 weeks from the time of bonding with the polyimide film substrate. In comparative examples 1 and 2 in which no ultraviolet absorber was added, the adhesion strength after 4 weeks increased to 30 times or more the adhesion strength immediately after bonding, and it became difficult to peel off from the polyimide film substrate.
Examples 1 to 4 in which the ultraviolet absorber was added showed a smaller increase rate of the adhesive strength after 4 weeks than comparative example 1, and the increase in the adhesive strength was suppressed as the amount of the ultraviolet absorber added was increased. The same tendency was observed in the comparison of comparative example 2 with examples 5 to 8. From these results, it was found that addition of an ultraviolet absorber can suppress photocuring of the adhesive in a bright room environment.
Examples 1 and 2 showed a decrease in adhesion after photocuring as compared with examples 3 and 4 and comparative example 1, and example 5 showed a decrease in adhesion after photocuring as compared with examples 6 to 8 and comparative example 1. From these results, it is considered that when the amount of the ultraviolet absorber added is increased, the amount of the ultraviolet absorber absorbed by the photopolymerization initiator (radical initiator) decreases as the amount of the ultraviolet absorber absorbed increases, and therefore, the photocuring of the adhesive can be suppressed.
Claims (17)
1. A reinforcing film comprising a film base and an adhesive layer fixedly laminated on one main surface of the film base,
the adhesive layer is formed from a photocurable composition containing a base polymer, a photocuring agent, a photoradical initiator, and an ultraviolet absorber.
2. The reinforced film of claim 1, wherein the photo radical initiator has an absorption maximum in a wavelength range of 310nm to 370 nm.
3. The reinforced film of claim 2, wherein the photo radical initiator does not exhibit an absorption maximum at wavelengths greater than 380 nm.
4. A reinforced film according to claim 2 or 3, wherein the photo radical initiator has an absorption coefficient of 1 x 10 at a wavelength of 405nm2[mLg-1cm-1]The following.
5. The reinforcing film according to any one of claims 2 to 4, wherein the adhesive layer has a light transmittance of 3 to 70% at a maximum absorption wavelength in a range of a wavelength of 310 to 370nm of the photo radical initiator.
6. A reinforced film according to any one of claims 2 to 5, wherein the photo radical initiator has a light transmittance of 3 to 70% at a maximum absorption wavelength in the range of 310 to 370 nm.
7. The reinforced film according to any one of claims 1 to 6, wherein the adhesive layer has a light transmittance of 3 to 70% at a wavelength of 350 nm.
8. The reinforced film according to any one of claims 1 to 7, which has a light transmittance of 3 to 70% at a wavelength of 350 nm.
9. The reinforced film according to any one of claims 1 to 8, wherein the photocurable composition contains 10 to 50 parts by weight of the photocurable agent per 100 parts by weight of the base polymer.
10. The reinforcing film according to any one of claims 1 to 9, wherein the photocurable composition contains 0.01 to 1 part by weight of the photoradical initiator and 0.1 to 10 parts by weight of the ultraviolet absorber, relative to 100 parts by weight of the base polymer.
11. A reinforced film according to any one of claims 1 to 10 wherein the ultraviolet absorber is a triazine compound.
12. The reinforcing film according to any one of claims 1 to 11, wherein the gel fraction of the photocurable composition is 60% or more.
13. The reinforced film according to any one of claims 1 to 12, wherein the base polymer contains 1 or more selected from the group consisting of a hydroxyl group-containing monomer and a carboxyl group-containing monomer as a monomer unit, and a crosslinking structure is introduced by a crosslinking agent bonded to a hydroxyl group or a carboxyl group.
14. The reinforced film according to any one of claims 1 to 13, wherein an acrylic polymer is contained as the base polymer.
15. The reinforced film of any of claims 1-14, wherein the photocuring agent is a multifunctional (meth) acrylate.
16. The reinforced film according to any one of claims 1 to 15, wherein the photocuring agent has a functional group equivalent of 100 to 500 g/eq.
17. The reinforcing film according to any one of claims 1 to 16, wherein the adhesion force with the polyimide film after the pressure-sensitive adhesive layer is photocured is 5 times or more the adhesion force with the polyimide film before the pressure-sensitive adhesive layer is photocured.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2019-023020 | 2019-02-12 | ||
| JP2019023020A JP7348727B2 (en) | 2019-02-12 | 2019-02-12 | reinforcing film |
| PCT/JP2020/003829 WO2020166399A1 (en) | 2019-02-12 | 2020-01-31 | Reinforcement film |
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| CN113423573A true CN113423573A (en) | 2021-09-21 |
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|---|---|---|---|
| CN202080013960.5A Pending CN113423573A (en) | 2019-02-12 | 2020-01-31 | Reinforced film |
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| Country | Link |
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| JP (1) | JP7348727B2 (en) |
| KR (1) | KR20210126632A (en) |
| CN (1) | CN113423573A (en) |
| WO (1) | WO2020166399A1 (en) |
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| JP6981514B1 (en) * | 2020-10-13 | 2021-12-15 | 王子ホールディングス株式会社 | Adhesive sheet |
| KR20220132450A (en) * | 2021-03-23 | 2022-09-30 | 삼성에스디아이 주식회사 | Adhesive film, optical member comprising the same and optical display apparatus comprising the same |
| KR102615472B1 (en) * | 2021-03-23 | 2023-12-19 | 삼성에스디아이 주식회사 | Adhesive film, optical member comprising the same and optical display apparatus comprising the same |
| KR102635253B1 (en) * | 2021-03-23 | 2024-02-07 | 삼성에스디아이 주식회사 | Adhesive film, optical member comprising the same and optical display apparatus comprising the same |
| KR20240049313A (en) * | 2021-08-20 | 2024-04-16 | 닛토덴코 가부시키가이샤 | adhesive sheet |
| WO2023042726A1 (en) * | 2021-09-16 | 2023-03-23 | 日東電工株式会社 | Reinforcing film, method for producing and method for reinforcing device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017014379A (en) * | 2015-06-30 | 2017-01-19 | リンテック株式会社 | Adhesive composition, adhesive sheet and display body |
| JP2017066322A (en) * | 2015-10-01 | 2017-04-06 | 東亞合成株式会社 | Active energy ray curable adhesive composition excellent in insulation property |
| JP2017097974A (en) * | 2015-11-18 | 2017-06-01 | デクセリアルズ株式会社 | Anisotropically conductive film, method for connecting electronic component, and method for manufacturing connection structure |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR102086212B1 (en) | 2014-04-22 | 2020-03-06 | 닛토덴코 가부시키가이샤 | Adhesive sheet |
| JP2015217530A (en) | 2014-05-14 | 2015-12-07 | 株式会社巴川製紙所 | Adhesive high hardness transparent film |
| SG11201800572XA (en) | 2016-01-27 | 2018-02-27 | Nitto Denko Corp | Stress distributing film, optical member, and electronic member |
| WO2017138544A1 (en) * | 2016-02-08 | 2017-08-17 | 三菱ケミカル株式会社 | Transparent double-sided pressure-sensitive adhesive sheet and laminate of pressure-sensitive adhesive sheet |
| JP7111558B2 (en) * | 2018-08-27 | 2022-08-02 | 日東電工株式会社 | laminate |
-
2019
- 2019-02-12 JP JP2019023020A patent/JP7348727B2/en active Active
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2020
- 2020-01-31 CN CN202080013960.5A patent/CN113423573A/en active Pending
- 2020-01-31 WO PCT/JP2020/003829 patent/WO2020166399A1/en active Application Filing
- 2020-01-31 KR KR1020217027968A patent/KR20210126632A/en not_active Application Discontinuation
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017014379A (en) * | 2015-06-30 | 2017-01-19 | リンテック株式会社 | Adhesive composition, adhesive sheet and display body |
| JP2017066322A (en) * | 2015-10-01 | 2017-04-06 | 東亞合成株式会社 | Active energy ray curable adhesive composition excellent in insulation property |
| JP2017097974A (en) * | 2015-11-18 | 2017-06-01 | デクセリアルズ株式会社 | Anisotropically conductive film, method for connecting electronic component, and method for manufacturing connection structure |
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| JP7348727B2 (en) | 2023-09-21 |
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| KR20210126632A (en) | 2021-10-20 |
| JP2020132658A (en) | 2020-08-31 |
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