JP2013067737A - Transparent adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent adhesive sheet that can strike a balance between step conformability and reworkability.SOLUTION: An adhesive agent layer is formed on each of both surfaces of a core material film formed of an uncrosslinked or crosslinked material of a chain olefin-cyclic olefin copolymer. The storage elastic modulus at 60°C of the core material film is 1×10to 1×10Pa, and a storage elastic modulus at 25°C to a storage elastic modulus at 60°C of 1 is 50 to 5×10.

Description

  The present invention relates to a transparent pressure-sensitive adhesive sheet (for example, a transparent pressure-sensitive adhesive sheet that can be used for laminating various optical members) excellent in step followability (step difference absorbability) and reworkability (peelability).

  A transparent adhesive sheet is used for laminating various optical members. For example, in a display device equipped with a touch panel, a protective panel such as an acrylic plate or a glass plate is provided with a predetermined gap in order to protect the panel from being subjected to external impacts. Is arranged. However, since this gap is an air layer, the light reflection loss is large due to the refractive index difference between the material constituting the protective panel and the air layer, and good visibility cannot be obtained. Therefore, the gap is filled with the transparent adhesive sheet to improve the visibility, and the strength of the protective panel is increased, thereby preventing the broken pieces from being broken due to the impact.

The transparent adhesive sheet can be classified into a type without a core material and a type with a core material. As an adhesive sheet without a core material, for example, JP 2010-72471 A (Patent Document 1) has a storage elastic modulus of 1.0 × 10 ^{3 to} 1.0 × 10 ⁴ Pa at 1 Hz and 80 ° C. A transparent pressure-sensitive adhesive sheet containing an alicyclic hydrocarbon resin, an amorphous saturated polyolefin resin, a resin having an acrylic group, and an initiator that causes a reaction of the resin in a predetermined ratio is disclosed. In the examples of this document, hydrogenated dicyclopentanediene resin is used as the alicyclic hydrocarbon resin. However, since this pressure-sensitive adhesive sheet does not have a core material, the reworkability is not sufficient, and when the pressure-sensitive adhesive sheet is peeled off, the pressure-sensitive adhesive sheet is broken and adhesive residue is generated. Moreover, it is difficult to fill a large gap, and punching workability is not sufficient.

  As a pressure-sensitive adhesive sheet having a core material, for example, in JP-A-6-346032 (Patent Document 2), a polyurethane film having an elongation of 300 to 600% and a thickness of 30 to 200 μm is used as a base material. A double-sided pressure-sensitive adhesive tape having an adhesive layer on both sides is disclosed. Japanese Patent Application Laid-Open No. 2010-264748 (Patent Document 3) includes a stress relaxation resin layer (A) formed by a casting method and a stress relaxation resin layer (B) provided on both surfaces thereof. A laminated member is disclosed. This document describes that the resin forming the resin layer (A) is preferably a polyester resin (particularly a polyester urethane resin), and the storage elastic modulus at a temperature of 23 ° C. of the resin layer (A) is usually 0.00. It is described as being about 1 to 20 MPa.

  However, these pressure-sensitive adhesive sheets are composed of a polyurethane-based resin or a polyester resin as a core material, so that the step following ability is not sufficient for an adherend having a convex portion on the surface. In particular, recently, the protection panel has been flattened, and a black print layer is provided on the outer peripheral edge of the protection panel, so that it is not possible to sufficiently follow such a step due to the thickness of the print layer. Accordingly, it is very difficult to bond the pressure-sensitive adhesive sheet, and appearance defects are likely to occur. In addition, when the core material is made of a polyester resin (for example, polyethylene terephthalate), the phase difference is large, which may cause display defects of the display device.

JP 2010-72471 A (Claims, Examples) JP-A-6-346032 (Claims) JP 2010-264748 A (Claims, paragraph [0010], Examples)

  Therefore, the objective of this invention is providing the transparent adhesive sheet which can make level | step difference followability and rework property (peelability after sticking) compatible, and its manufacturing method.

  Another object of the present invention is to provide a transparent pressure-sensitive adhesive sheet having an appropriate flexibility during bonding and capable of bonding both adherends without gaps even when the gap between adherends is large, and a method for producing the same. It is in.

  Still another object of the present invention is to provide a transparent pressure-sensitive adhesive sheet having excellent durability and capable of preventing bubbles from being generated at the interface with the adherend even under high temperature and high humidity, and a method for producing the same.

  Another object of the present invention is to provide a transparent adhesive sheet excellent in punching workability and a method for producing the same.

  Still another object of the present invention is to provide a transparent pressure-sensitive adhesive sheet that is excellent in optical isotropy and does not impair visibility even when used for bonding optical members constituting a display device, and a method for producing the same.

  With regard to the core material of the transparent adhesive sheet, if the core material is composed of a resin having a high elastic modulus and a high elongation, it has good reworkability even if a large stress is applied at the time of peeling. Due to its high elastic modulus, it has poor deformability and low step following ability. On the other hand, if the core material is made of a resin having a low elastic modulus, it has increased flexibility and has a certain level of step following ability, but because the tensile stress decreases, the core material is easily broken by the stress at the time of peeling, and reworkability Is low. As described above, the step following property and the rework property are in a trade-off relationship, and it is extremely difficult to achieve both.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventor has increased the elastic modulus at room temperature when the core film is formed of a specific chain olefin-cyclic olefin copolymer uncrosslinked product or crosslinked product, Furthermore, it has been found that the elongation can be increased, the elastic modulus at the bonding processing temperature can be reduced, the step following ability can be secured, and the step followability and reworkability of the transparent adhesive sheet can be achieved at the same time. The present invention has been completed. That is, it has been found that it is important to use a resin that has high elasticity at room temperature and high tensile elongation, but has a low elastic modulus in a high temperature region. And it discovered that such performance could be acquired with the core material film formed with the uncrosslinked body or crosslinked body of the chain olefin-cyclic olefin copolymer, and completed this invention.

That is, the transparent pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer (for example, both surfaces) on at least one surface (particularly both surfaces) of a core film formed of an uncrosslinked or crosslinked body of a chain olefin-cyclic olefin copolymer. An acrylic pressure-sensitive adhesive layer) is formed. In this core film, the storage elastic modulus in the vicinity of the processing (sticking) temperature (for example, 60 ° C.) of the transparent adhesive sheet is 1 × 10 ⁴ to 1 × 10 ⁸ Pa (for example, 1 × 10 ^{5 to} 5 × 10 ^7). The storage elastic modulus at room temperature (for example, 25 ° C.) is 50 to ⁵ × 10 ⁵ (for example, 70 to 1000) with respect to the storage elastic modulus 1 in the vicinity of the processing temperature (for example, 60 ° C.). Degree).

  The glass transition temperature of the chain olefin-cyclic olefin copolymer may be about 10 to 50 ° C. (for example, more than 30 ° C. and 50 ° C. or less). In the chain olefin-cyclic olefin copolymer, the ratio of the cyclic olefin is 15 to 50 mol% (for example, more than 15 mol% and 40 mol% or less) with respect to the total of the chain olefin and the cyclic olefin. It may be a degree.

  The core material film may further have at least one of the following characteristics (1) to (4).

(1) Tensile stress at 100% elongation at room temperature is about 15 to 100 MPa (2) In-plane retardation at a wavelength of 590 nm is 10 nm or less in terms of thickness 100 μm (3) Thickness is about 20 to 400 μm (4) The surface tension is about 40 to 70 mN / m.

  The core material film may be formed of a radiation cross-linked body or an electron beam cross-linked body of a chain olefin-cyclic olefin copolymer. Moreover, the surface of the core material film may be subjected to corona treatment or plasma treatment. Furthermore, the core material film may be formed by extruding a chain olefin-cyclic olefin copolymer (uncrosslinked product).

  The transparent adhesive sheet of the present invention is suitable for laminating optical members and may be used for laminating two panels selected from, for example, a touch panel, a liquid crystal display panel, and a protective panel.

  The present invention includes a method for producing a transparent pressure-sensitive adhesive sheet by laminating a pressure-sensitive adhesive layer on at least one surface of a core film formed of a chain olefin-cyclic olefin copolymer (uncrosslinked product). . The present invention also provides a core obtained by crosslinking a film obtained by extruding a chain olefin-cyclic olefin copolymer (uncrosslinked product) by irradiating with an active energy ray (radiation, electron beam, etc.). A method for producing a transparent adhesive sheet by forming a material film and laminating an adhesive layer on at least one surface of the core material film is also included.

  In the present specification, the “chain olefin-cyclic olefin copolymer” means an uncrosslinked product unless otherwise specified. In the present specification, the upper limit and the lower limit of the numerical range can be arbitrarily combined.

  In the present invention, since the elastic modulus at room temperature is high, the ductility is excellent, the reworkability can be improved, and the elastic modulus is lowered under the process conditions at the time of bonding. it can. Moreover, in this invention, it has a moderate softness | flexibility at the time of a bonding process, and is excellent in level | step difference followability even if the thickness of a transparent adhesive sheet is large. Therefore, even if the gap between adherends is large, both adherends can be bonded without gaps. As described above, in the present invention, the adhesion to the adherend is excellent, and the durability is also excellent. For example, it is possible to effectively prevent bubbles from being generated at the interface with the adherend even under harsh conditions (such as under high temperature and high humidity). In this invention, since it has a specific core material, it is excellent also in punching workability. Moreover, in this invention, it is excellent in optical isotropy, and even if it uses it for bonding of the optical member which comprises a display apparatus, the display property of a display apparatus is not inhibited.

  The transparent pressure-sensitive adhesive sheet (or step-following pressure-sensitive adhesive sheet) of the present invention includes a core material film and a pressure-sensitive adhesive layer formed on at least one surface (particularly both surfaces) of the core material film.

(Core film)
The core material film is formed (or configured) from an uncrosslinked or crosslinked body of a chain olefin-cyclic olefin copolymer (cyclic olefin resin or cyclic olefin elastomer).

Examples of the chain olefin include chain C such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene. _2-10 olefins etc. are mentioned. These chain olefins can be used alone or in combination of two or more. Among these chain olefins, α-chain C _2-8 olefins are preferable, and α-chain C _2-4 olefins (particularly ethylene) are more preferable.

The cyclic olefin may be a polymerizable cyclic olefin having an ethylenic double bond in the ring, and may be a monocyclic olefin (for example, cyclic C _4-12 cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, etc. However, polycyclic olefins are preferred.

  Examples of typical polycyclic olefins include norbornene (2-norbornene), norbornene having a substituent, a multimer of cyclopentadiene, a multimer of cyclopentadiene having a substituent, and the like. Examples of the substituent include an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a cyano group, an amide group, and a halogen atom. These substituents may be used alone or in combination of two or more.

  Specifically, examples of the polycyclic olefin include 2-norbornene; 5-methyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl-2-norbornene. Norbornenes having an alkyl group such as: norbornenes having an alkenyl group such as 5-ethylidene-2-norbornene; alkoxycarbonyls such as 5-methoxycarbonyl-2-norbornene and 5-methyl-5-methoxycarbonyl-2-norbornene Norbornenes having a group; norbornenes having a cyano group such as 5-cyano-2-norbornene; norbornenes having an aryl group such as 5-phenyl-2-norbornene and 5-phenyl-5-methyl-2-norbornene; Dicyclopentadiene; 2,3-dihydrodi Derivatives such as clopentadiene, methanooctahydrofluorene, dimethanooctahydronaphthalene, dimethanocyclopentadienonaphthalene, methanooctahydrocyclopentadienonaphthalene; derivatives having substituents such as 6-ethyl-octahydronaphthalene; cyclo Examples thereof include adducts of pentadiene and tetrahydroindene, and 3-tetramers of cyclopentadiene.

  These cyclic olefins can be used alone or in combination of two or more. Of these cyclic olefins, polycyclic olefins such as norbornenes are preferred.

  The ratio of cyclic olefin is 15-50 mol% with respect to the sum total of a chain olefin and cyclic olefin, for example, Preferably it is 16-45 mol%, More preferably, it is about 17-40 mol%, Usually, 15 About 40 mol%. When the ratio of the cyclic olefin is too small, the crystallinity is increased and the transparency is lowered, and when the ratio of the cyclic olefin is too large, the glass transition point is increased. The above ratio is, for example, more than 15 mol% and not more than 40 mol%, preferably 16 to 30 mol%, more preferably from the point of improving crosslinkability (such as active energy ray crosslinking without heating). About 17-25 mol% (for example, 18-22 mol%) may be sufficient.

  The chain olefin-cyclic olefin copolymer may contain other copolymer units. Examples of copolymeric monomers that form other copolymer units include vinyl ester monomers (eg, vinyl acetate, vinyl propionate, etc.); diene monomers (eg, butadiene, isoprene, etc.) ); (Meth) acrylic monomers [for example, (meth) acrylic acid or derivatives thereof (such as (meth) acrylic acid ester)] and the like. These copolymerizable monomers may be used alone or in combination of two or more. The content of these copolymerizable monomers is, for example, 5 mol% or less, preferably 1 mol% or less, based on the copolymer.

  The chain olefin-cyclic olefin copolymer may be a resin obtained by addition polymerization, or may be a resin obtained by ring-opening polymerization (such as ring-opening metathesis polymerization). The polymer obtained by ring-opening metathesis polymerization may be a hydrogenated hydrogenated resin. The polymerization method of the chain olefin-cyclic olefin copolymer is a conventional method, for example, ring-opening metathesis polymerization using a metathesis polymerization catalyst, addition polymerization using a Ziegler type catalyst, addition polymerization using a metallocene catalyst (usually , Ring-opening metathesis polymerization using a metathesis polymerization catalyst) can be used.

  The degree of crystallinity of the chain olefin-cyclic olefin copolymer can be selected from a range of about 10% or less, for example, 0 to 10%, preferably 0.01 to 5%, more preferably 0.05 to 3%. (For example, about 0.1 to 1%). In the present invention, the chain olefin-cyclic olefin copolymer is amorphous and excellent in transparency (light guiding properties).

  The glass transition temperature (Tg) of the chain olefin-cyclic olefin copolymer can be selected from a range of about 10 to 100 ° C., for example, 15 to 90 ° C., preferably 20 to 80 ° C., more preferably 25 to 75 ° C. Degree. Moreover, said glass transition temperature may be about 15-50 degreeC, for example, Preferably it is 20-40 degreeC, More preferably, about 25-35 degreeC from the point which balances a softness | flexibility and heat resistance highly. . Further, the glass transition temperature may be in a range exceeding 30 ° C. from the viewpoint of transparency, for example, 31 to 50 ° C., preferably 32 to 45 ° C., more preferably about 33 to 40 ° C. May be. The glass transition temperature can be controlled by adjusting the ratio of the monomer, the substituent of the monomer, the molecular weight of the polymer, and the like. The glass transition temperature can be measured by a conventional method such as a differential scanning calorimeter (DSC).

  The refractive index of the chain olefin-cyclic olefin copolymer is 1.48 to 1.58, preferably 1.50 to 1.56, more preferably about 1.51 to 1.55 at 23 ° C. and a wavelength of 589 nm. It is. In the present invention, since the difference in refractive index with an optical member (such as a glass plate) can be reduced compared to a polyester resin or the like, even if it is used for laminating an optical member constituting a display device, at the interface with the optical member. It is possible to effectively prevent the reflection of light and not impair the display performance of the display device.

  The number average molecular weight of the chain olefin-cyclic olefin copolymer is, for example, 1000 to 150,000, preferably 5,000 to 120,000, more preferably 10,000 to 100,000 (particularly 20,000) in terms of polystyrene in gel permeation chromatography (GPC). ~ 90,000).

The chain olefin-cyclic olefin copolymer may be combined with other resin components as long as the effects of the present invention are not impaired. The other resin component is usually a resin or elastomer that is compatible or cross-linked with the chain olefin-cyclic olefin copolymer, and is a chain olefin resin, for example, the chain olefin illustrated above [for example, ethylene, propylene, etc. Α-chain C _2-4 olefin (especially ethylene), etc.] and, if necessary, a copolymerizable monomer [e.g. vinyl ester monomer, diene monomer, (meth) acrylic monomer Polymers having a polymerization component as a polymerization component can be exemplified. Typical chain olefin resins are polyethylene resins, polypropylene resins, and the like. These chain olefin resins can be used alone or in combination of two or more. Of these chain olefin resins, polyethylene resins such as low, medium or high density polyethylene, and linear low density polyethylene are preferred.

  The glass transition temperature of the chain olefin-based resin is not particularly limited and can be selected from a range of about −150 ° C. to 10 ° C., for example, −110 to 0 ° C., preferably −80 to −5 ° C., more preferably − About 50--10 degreeC may be sufficient. In the present invention, the glass transition temperature can be adjusted by combining a chain olefin-cyclic olefin copolymer and a chain olefin resin.

  The number average molecular weight of the chain olefin resin may be, for example, 5,000 to 300,000, preferably 10,000 to 200,000, and more preferably about 15,000 to 150,000 in terms of polystyrene in gel permeation chromatography (GPC).

  The ratio of other resin components (such as a chain olefin resin) can be selected from a range of about 0.01 to 100 parts by weight with respect to 100 parts by weight of the chain olefin-cyclic olefin copolymer. 05 to 50 parts by weight, preferably about 0.1 to 30 parts by weight, and 25 parts by weight or less (for example, 0.01 to 20 parts by weight, preferably about 0.1 to 10 parts by weight). May be. When the other resin component is a chain olefin resin, if the content is too large, the transparency is lowered.

  The chain olefin-cyclic olefin copolymer may be crosslinked by a conventional method. In addition, you may perform a crosslinking process with respect to the molded object of a chain olefin-cyclic olefin copolymer. Examples of the crosslinking method include a method of heat treatment, a method of irradiating active energy rays [for example, ultraviolet rays, radiation (γ rays, X rays, etc.), electron beams, etc.]. Among these crosslinking methods, there is no need for a crosslinking agent or crosslinking accelerator (auxiliary agent), and there is a method of irradiating active energy rays (especially electron beams) from the viewpoint of efficiently producing a highly stable crosslinked product. preferable. In the present invention, since the Tg of the cyclic olefin-based resin is low, the cyclic olefin-based resin can be crosslinked at normal temperature (for example, a temperature of about 10 to 30 ° C.) without heating in irradiation with active energy rays, and the crosslinking density is also high. Can be improved.

  The irradiation amount (dose) of the active energy ray can be selected from a range of, for example, about 100 to 500 kGy (gray) (for example, 150 to 400 kGy), and 200 kGy from the viewpoint of improving the heat resistance and durability by increasing the crosslinking density. For example, it may be about 200 to 500 kGy, preferably about 220 to 450 kGy, and more preferably about 230 to 430 kGy (particularly about 250 to 400 kGy).

  The acceleration voltage of the active energy ray can be selected from a range of, for example, about 100 to 5000 kV (for example, 150 to 400 kV), and may be 150 kV or more from the viewpoint of improving heat resistance and durability. It may be about 3500 kV, preferably 170 to 3000 kV, more preferably about 180 to 1000 kV.

  The irradiation with active energy rays may be performed in the air, and if necessary, may be performed in an inert gas (for example, nitrogen gas, argon gas, helium gas) atmosphere.

  Thus, the core material film may be formed of an uncrosslinked product or a crosslinked product of a chain olefin-cyclic olefin copolymer. The point of improving the affinity with the pressure-sensitive adhesive layer described later, the point of controlling expansion and contraction due to heat, the interface with the adherend even under high temperature and high humidity (particularly in the case of an adherend having a convex portion, a step The core film is a cross-linked body of a chain olefin-cyclic olefin copolymer (for example, a radiation cross-linked body or an electron beam cross-linked body, particularly a cross-linked body such as a radiation cross-linked body or an electron beam cross-linked body). It is preferably formed of an electron beam cross-linked product.

  The glass transition temperature of the crosslinked product can be selected from the same range as that of the chain olefin-cyclic olefin copolymer (uncrosslinked product). Thus, the glass transition temperature does not increase even after crosslinking, and the temperature difference from the glass transition temperature before crosslinking may be 50 ° C. or less, for example, 0 to 40 ° C., preferably 0 to 30 ° C. Preferably it is about 0-20 degreeC (especially 0-10 degreeC), and the high softness | flexibility is hold | maintained after bridge | crosslinking.

  The degree of crosslinking in the crosslinked product can be indicated by a gel fraction measured by a method of refluxing with toluene for 3 hours. The gel fraction of the crosslinked product may be, for example, 5% by weight or more, for example, 10 to 99% by weight (for example, 30 to 98% by weight), preferably 50 to 97% by weight, and more preferably 80 to 80%. It may be about 95% by weight (particularly 85 to 93% by weight). In detail, a gel fraction can be measured with the measuring method as described in an Example. The crosslinking density can be controlled by the active energy ray irradiation conditions, etc., but the gel fraction can be adjusted to 80% by weight or more (especially 85% by weight or more) by adjusting the ratio of the cyclic olefin to a specific range. it can. As a result, the crosslinked density of the crosslinked body is increased, and the heat resistance and durability can be improved.

  The core material film can be manufactured by forming a film of a cyclic olefin resin by a conventional film forming method, for example, a casting method, an extrusion molding method, a blow molding method, or the like. In the present invention, since a chain olefin-cyclic olefin copolymer is contained, high optical isotropy can be obtained even if a film is formed by an extrusion molding method. Moreover, in order to improve adhesiveness with the below-mentioned adhesive layer, the core material film may be subjected to surface treatment such as corona treatment or plasma treatment. If necessary, the core material film may be stretched at a predetermined magnification using a uniaxial or biaxial stretching machine.

The storage elastic modulus of the core film at room temperature (for example, 25 ° C.) is, for example, 5 × 10 ^{8 to} 5 × 10 ⁹ Pa, preferably 8 × 10 ⁸ to 4 × 10 ⁹ Pa, and more preferably 1 × 10. It is about ^{9 to} 3 × 10 ⁹ Pa. In this invention, since the elasticity modulus at room temperature is comparatively large, it is excellent in rework property.

The storage elastic modulus in the vicinity of the processing (sticking) temperature (for example, 60 ° C.) of the core film is, for example, 1 × 10 ⁴ to 1 × 10 ⁸ Pa, preferably 1 × 10 ^{5 to} 5 × 10 ⁷ Pa, Preferably, it is about 1 × 10 ⁶ to 1 × 10 ⁷ Pa. Thus, since the core material film has a low elastic modulus at the processing temperature of the transparent adhesive sheet, the core film is excellent in step following ability. In addition, processing temperature means the temperature at the time of bonding a transparent adhesive sheet to a to-be-adhered body. The vicinity of the processing temperature means, for example, T ° C. to (T + 20) ° C., preferably (T + 5) ° C. to (T + 15) ° C. when the processing temperature is T.

The present invention is characterized in that the ratio of the storage elastic modulus at room temperature to the storage elastic modulus in the vicinity of the processing temperature of the core material film is adjusted to a specific range in order to achieve both step following ability and reworkability. That is, the storage elastic modulus at room temperature (for example, 25 ° C.) is 50 to ⁵ × 10 ⁵ (for example, 60 to 1 × 10 ⁴ ) with respect to the storage elastic modulus of 1 near the processing temperature (for example, 60 ° C.). ), Preferably 70 to 1000 (for example, 80 to 500), more preferably about 90 to 300 (for example, 100 to 280). If the above storage elastic modulus ratio is too small, the step following property and the reworkability are deteriorated.

  The tensile stress at 100% elongation of the core material film at room temperature may be, for example, 15 to 100 MPa, preferably 17 to 80 MPa, and more preferably about 20 to 60 MPa. If the tensile stress is too small, the reworkability is lowered.

  The core film is excellent in optical isotropy, and the in-plane retardation at a wavelength of 590 nm is, for example, 10 nm or less (for example, 0.1 to 5 nm), preferably 0.5 to 3.5 nm in terms of a thickness of 100 μm. (For example, 1 to 3 nm), more preferably about 1.5 to 2.5 nm.

  The core film is excellent in transparency, and the total light transmittance is, for example, 80% or more, preferably 85% or more, and more preferably 90% or more (for example, 90%) by a method (thickness 100 μm) based on JIS K7105. ~ 99%). Further, the haze (cloudiness value) of the core material film may be 50% or less, for example, in accordance with JIS K7105 (thickness: 100 μm), preferably 0 to 10%, more preferably 0 to 3%. (Especially 0 to 1%).

  The surface energy (or surface tension) of the core film is, for example, 30 to 80 mN / m, preferably 35 to 75 mN / m, more preferably 40 to 70 mN / m (for example, 45 to 65 mN) in accordance with JIS K6768. / M). When the surface energy of the core film is too small, the adhesiveness with the pressure-sensitive adhesive layer is lowered.

  The thickness of the core film may be, for example, 20 to 400 μm, preferably 30 to 350 μm, more preferably about 40 to 300 μm, 100 μm or more (for example, 100 to 400 μm), preferably 150 μm or more (for example, 200). About 350 μm). In the present invention, even if the thickness of the core material film is large, since it has appropriate flexibility at the bonding processing temperature, it can sufficiently follow the step.

  In addition, in the transparent adhesive sheet (double-sided adhesive sheet) used for bonding an optical member, a core material film is corresponded to an OCA (Optical Clear Adhesive) tape base material, for example.

(Adhesive layer)
The pressure-sensitive adhesive layer is not particularly limited as long as it has adhesiveness to an adherend (such as an optical member) and is transparent. The pressure-sensitive adhesive layer is composed of a conventional pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, and a rubber-based pressure-sensitive adhesive. These pressure-sensitive adhesives may be used alone or in combination of two or more. Of these pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are widely used.

The acrylic pressure-sensitive adhesive usually contains a (meth) acrylic copolymer (uncrosslinked or crosslinked). The (meth) acrylic monomer [(meth) acrylic monomer having no crosslinkable group] forming the (meth) acrylic copolymer is, for example, methyl (meth) acrylate or ethyl (meth) acrylate. , Propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) ) Linear or branched C _1-20 alkyl (meth) acrylate such as acrylate, isononyl (meth) acrylate; C _5-10 cycloalkyl (meth) acrylate such as cyclohexyl (meth) acrylate; isobornyl (meth) acrylate Bridge ring type (Meta Acrylate; and _{C 6-10} aryl (meth) acrylates such as phenyl (meth) acrylate can be exemplified.

  The (meth) acrylic monomer may have a functional group (crosslinkable group) capable of crosslinking the (meth) acrylic copolymer. Examples of the crosslinkable group include a hydroxyl group, a carboxyl group, an epoxy group, and an amide group. The (meth) acrylic monomer may have the above crosslinkable group alone or in combination of two or more.

Examples of the (meth) acrylic monomer having a hydroxyl group include hydroxy C _2-4 alkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate; (poly) ethylene glycol mono (meth) acrylate (poly ) C _2-4 alkylene glycol mono (meth) acrylate; glycerin di (meth) acrylate, trimethylolethane di (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol di or tri (meth) acrylate, dipenta Examples include erythritol di to penta (meth) acrylate.

As the (meth) acrylic monomer having a carboxyl group, (meth) acrylic acid; carboxy C _2-6 alkyl (meth) acrylate such as β-carboxyethyl (meth) acrylate; dicarboxylic acid and hydroxyl group ( Examples thereof include monoesters with (meth) acrylic monomers.

Examples of the (meth) acrylic monomer having an epoxy group include glycidyl (meth) acrylate, and the (meth) acrylic monomer having an amide group includes (meth) acrylamide; N, N-di Examples thereof include N-substituted (meth) acrylamides such as C _1-4 alkyl (meth) acrylamide.

These (meth) acrylic monomers may be used alone or in combination of two or more. Among these (meth) acrylic monomers, at least C _1-10 alkyl acrylate (for example, C _2-8 alkyl acrylate such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate) is preferable. In addition, a (meth) acrylic monomer having a C _1-10 alkyl acrylate and a crosslinkable group [for example, an acrylic monomer having a hydroxyl group and / or an acrylic monomer having a carboxyl group, particularly a hydroxyl group Combinations with [C _2-6 alkyl acrylate] are also preferred.

  The pressure-sensitive adhesive may contain conventional additives such as a crosslinking agent, a stabilizer, a flame retardant, a tackifier (tackifier), and the like. These additives can be used alone or in combination of two or more.

  Among the above additives, the crosslinking agent can be appropriately selected depending on the crosslinking group, and examples thereof include an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. These crosslinking agents can be used alone or in combination of two or more. Among these crosslinking agents, isocyanate crosslinking agents are widely used for crosslinking groups such as hydroxyl groups.

  The isocyanate-based crosslinking agent is not particularly limited as long as it has a plurality of isocyanate groups. Triisocyanates such as 1,3,6-hexamethylene triisocyanate], alicyclic polyisocyanates [eg, cyclohexane 1,4-diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated bis (isocyanatophenyl) methane Diisocyanates such as: triisocyanates such as bicycloheptane triisocyanate], aromatic polyisocyanates [eg phenylene diiso Diisocyanates such as anate, tolylene diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate, naphthalene diisocyanate, bis (isocyanatophenyl) methane, toluidine diisocyanate, 1,3-bis (isocyanatophenyl) propane; triphenylmethane triisocyanate And the like, and dimers, trimers, adducts, biurets and the like of these polyisocyanates.

  These isocyanate crosslinking agents can be used alone or in combination of two or more. Among these isocyanate crosslinking agents, aromatic polyisocyanate crosslinking agents [for example, xylylene diisocyanate crosslinking agents (eg, xylylene diisocyanate modified with an alkane polyol such as xylylene diisocyanate, trimethylol propane, etc.)] Is preferred.

  The ratio of the crosslinking agent can be appropriately selected according to the ratio of the crosslinkable group of the crosslinking component in the pressure-sensitive adhesive. For example, 0.001 per 100 parts by weight of the crosslinking component [(meth) acrylic copolymer, etc.]. -10 parts by weight, preferably 0.005 to 5 parts by weight, more preferably about 0.01 to 1 part by weight.

  The thickness of the pressure-sensitive adhesive layer (when forming a pressure-sensitive adhesive layer on both sides, the thickness of each layer) is, for example, about 5 to 100 μm, preferably 10 to 90 μm, and more preferably 20 to 80 μm (for example, 30 to 70 μm). May be.

  The thickness ratio between the core material film and the pressure-sensitive adhesive layer (the thickness of each layer when forming pressure-sensitive adhesive layers on both sides) is that the core material film / pressure-sensitive adhesive layer = 1 / It may be about 10 to 10/1, preferably 1/2 to 8/1, more preferably about 1/1 to 5/1.

  The pressure-sensitive adhesive layer may be a commercially available product [for example, OCA (Optical Clear Adhesive) tape or the like], or may be prepared by a conventional method. For example, the pressure-sensitive adhesive layer can be formed by applying a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive and, if necessary, a solvent to the peelable substrate or the core material film. Examples of the coating method include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, and part coating. In addition, after application | coating, it dries as needed, and when an adhesive contains a crosslinking agent, it is bridge | crosslinked by a usual method.

  The transparent adhesive sheet should just be equipped with the core material film and the adhesive layer, and may laminate | stack other arbitrary layers (functional layer). For example, the transparent pressure-sensitive adhesive sheet is a release sheet [for example, paper or paper that may be surface-treated with a release agent (such as a silicone resin) on the pressure-sensitive adhesive layer in order to prevent adhesion to members other than the adherend. Plastic sheets etc.] may be laminated.

  In addition, the transparent adhesive sheet has a protective layer [for example, a glass plate, a transparent plastic film (such as an acrylic resin film)], an optical functional layer [for example, a hard coat film, an anti-glare film] on the adhesive layer. (AG film), antireflection film (AR film), polarizing film, retardation film, optical isotropic film, transparent conductive film (ITO film), electromagnetic prevention film (EMI film), viewing angle control film, etc.] May be laminated. Furthermore, the transparent adhesive sheet may have a plurality of laminated units (repeating units) composed of an adhesive layer and a protective layer or an optical functional layer.

  The total light transmittance and haze of the transparent pressure-sensitive adhesive sheet of the present invention can be selected from the same range as the core film, and are excellent in transparency. Moreover, since the transparent adhesive sheet of this invention is excellent in adhesiveness and reworkability in addition to transparency, it can be utilized suitably for bonding of an optical member, for example. For example, in the case of a display device including a touch panel, it can be suitably used for bonding two panels selected from a touch panel, a display panel, and a protection panel.

  Moreover, since the adhesive sheet of this invention is excellent also in level | step difference followable | trackability, it can be utilized suitably also for bonding of the member which has a convex part (The convex part which has a side surface which stands | starts up at a substantially right angle from a flat surface) on the surface. Examples of such a member include an optical member (such as a protective panel) on which a printed layer (such as a black printed layer) is formed. In the member having a convex portion on the surface, the planar shape (cross-sectional shape in the thickness direction) of the convex portion is not particularly limited, and may be, for example, a semicircle (mountain shape), a polygon (triangle, quadrangle, etc.). . The height of the convex portion may be about 1 to 20 μm (for example, 3 to 18 μm), preferably 5 to 15 μm (for example, 6 to 14 μm), and more preferably about 7 to 13 μm (for example, 8 to 12 μm). . In this invention, even if the height of a convex part is high, it can track and can improve adhesiveness with a to-be-adhered body.

The transparent pressure-sensitive adhesive sheet of the present invention comprises a conventional method, for example, a step of forming a core material film (or a precursor thereof) by forming a cyclic olefin-based resin into a film and, if necessary, a core material film by cross-linking the core material film precursor. Forming a material film;
If necessary, the core film can be manufactured through a surface treatment (corona treatment, plasma treatment, etc.) and a step of laminating an adhesive layer on at least one surface of the core film.

  The core film and the pressure-sensitive adhesive layer may be formed by a conventional method, for example, a method of forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive composition to at least one surface of the core film (wet laminating method). Examples thereof include a method (a dry laminating method) for pasting and an adhesive sheet.

  The present invention also includes an electronic device in which an optical member is bonded with a transparent adhesive sheet (double-sided adhesive sheet), for example, a display device provided with a touch panel (resistance film type, capacitance type, etc.).

  A display device having a resistive film type touch panel usually has a laminated unit in which a hard coat layer is laminated on one surface of a transparent adhesive sheet and a hard coat layer or a transparent resin layer is laminated on the other surface. Yes. As a typical form, a first laminated unit in which a hard coat layer / transparent adhesive sheet / hard coat layer / transparent conductive layer is laminated in order, and a transparent conductive layer / hard coat layer / transparent adhesive sheet / transparent resin layer / transparent Examples include a laminate in which a second laminate unit in which an adhesive sheet / display layer [liquid crystal display element (LCD) module] is sequentially laminated is laminated with each transparent conductive layer facing each other.

  In a display device having a capacitive touch panel, a glass plate is usually laminated on one surface of a transparent adhesive sheet, and a transparent conductive layer (a glass plate on which a transparent conductive layer is formed) is laminated on the other surface. Have stacked units. As a typical form, a laminate in which a glass plate / transparent adhesive sheet / transparent conductive layer / glass plate / transparent adhesive sheet / transparent conductive layer / glass plate / transparent adhesive sheet / display layer (LCD module) are laminated in this order. Etc. can be exemplified.

  In addition, in the bonding with the adherend, the bonding temperature is not particularly limited as long as the pressure-sensitive adhesive layer can express the adhesive force, and is, for example, about 40 to 60 ° C., preferably about 45 to 55 ° C. . Further, the bonding may be performed under normal pressure or under pressure (for example, 1.5 to 5 MPa, preferably about 2 to 4 MPa).

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the evaluation method in each physical property of an Example and a comparative example is as follows.

[Viscoelasticity measurement]
About the core material of an Example and a comparative example, using a dynamic viscoelasticity measuring apparatus (the TS instrument Japan Co., Ltd. product, RSA-III), the temperature increase rate of 5 degree-C / min and the angular frequency of 1 Hz Under the conditions, storage elastic modulus (E ′) and loss elastic modulus (E ″) were measured.

[Tensile test]
About the core material of an Example and a comparative example, the JIS No. 2 dumbbell piece (width 6mm) was punched in the flow (MD) direction, and the tensile test was done at 23 degreeC, 50% RH, and the tensile speed of 500 mm / min.

[Glass transition temperature and melting point]
About the core material of an Example and a comparative example, it measured by the temperature increase rate of 10 degree-C / min in nitrogen stream using the differential scanning calorimeter (Seiko Electronics Co., Ltd. product "DSC6200").

[Gel fraction]
500 mg of the core material of the example and the comparative example was weighed and put into a 100 ml eggplant type flask equipped with a cooling tube, 50 ml of toluene was further added, and the mixture was stirred at a reflux temperature for 3 hours. Thereafter, the mixture was filtered, and the filtration residue was dried under reduced pressure and weighed to obtain the gel fraction.

[Wet tension test]
About the core material of an Example and a comparative example, wetting tension (surface energy) was evaluated based on JISK6768.

[In-plane retardation]
The in-plane retardation of the core material of an Example and a comparative example was measured in wavelength 590nm using the phase difference measuring apparatus (the Oji Scientific Instruments company make, KOBRA-WPR).

[Step absorbency]
Linear black printing with a length of 50 mm, a width of 5 mm, and a thickness of 10 μm was performed on a flat glass plate to form steps. The laminated adhesive sheets obtained in the examples and comparative examples are pressed once with a 2 kg roller on the entire surface of the stepped glass plate, and autoclaved (50 ° C., 3 Mpa, 30 minutes). The presence or absence of air accumulation in the black printing part was visually observed. In the evaluation, if there was no air at all and bonding was possible, it was determined to be acceptable (O), and even an air layer could be confirmed even a little, and if floating was observed, it was determined to be unacceptable (x).

[Foaming resistance]
The laminated adhesive sheets obtained in the examples and comparative examples are pressed back and forth with a 2 kg roller between a flat glass plate having a length of 50 mm and a width of 50 mm and a flat PET film having a length of 50 mm and a width of 50 mm so that air does not enter. Then, autoclaving (50 ° C., 3 Mpa, 30 minutes) was performed, and it was confirmed that bubbles were removed. The integrated sample was allowed to stand for 150 hours in a constant temperature and humidity environment of 85 ° C. and 85% humidity, and the sample was visually observed. Evaluation is good when a sample is visually observed from the PET film side (◯), when there is no bubble of 1 mmφ or more (◯), when there is a bubble (less than 4) of 1 mmφ or more (Δ), 1 mmφ or more In the case of the presence of bubbles (4 or more), it was determined as impossible (×).

[Machinability]
Five laminated adhesive sheets of Examples and Comparative Examples are stacked and cut into A4 size with an NT cutter. At that time, there was no paste oozing out from the end portion by visual inspection, and it was judged as acceptable (◯) if there was no end portion deformation, and rejected (×) if there was paste oozing out and end portion deformation.

[Reworkability]
The laminated adhesive sheets obtained in Examples and Comparative Examples were pressed once on a flat glass plate with a length of 50 mm and a width of 50 mm with a 2 kg roller so as not to enter air, and then autoclaved (50 ° C., 3 Mpa, 30 minutes). A sample was prepared. When the laminated adhesive sheet is peeled from the glass plate in the direction of 150 ° at a speed of 500 mm / min, there is no adhesive residue and the core material is not broken (O), there is adhesive residue, and the core material is broken. Failed (x).

[Total light transmittance]
About the laminated adhesive sheet of an Example and a comparative example, the total light transmittance was measured based on JISK7105.

[Haze]
About the laminated adhesive sheet of an Example and a comparative example, haze was measured using the haze meter (Nippon Denshoku Industries Co., Ltd. product, NDH-500) based on JISK7136.

Preparation Example 1 Preparation of Adhesive Layer (A) Acrylate ester copolymer (molecular weight: 100) obtained by copolymerizing 79 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, and 1 part by weight of hydroxyethyl acrylate 10) To 100 parts by weight, 0.1 part by weight of toluene and xylylene diisocyanate trifunctional adduct (manufactured by Soken Chemical Co., Ltd., product name “TD-75” concentration 75% by weight) is added, mixed, and solid A coating solution for forming an adhesive layer (A) having a weight of 25% by weight was prepared. The said coating liquid was apply | coated to the peeling film so that the film thickness after drying might be set to 50 micrometers using a die coater, and after drying at 120 degreeC for 1 minute, the peeling film was bonded and the adhesion layer (A) was obtained. .

Example 1
Cyclic olefin-based resin (Topas Advanced Polymers GmbH, trade name “TOPAS 9903”, number average molecular weight 69000, glass transition temperature 33 ° C., norbornene content 20 mol%) is used as a small extruder (Plastics Engineering Laboratory Co., Ltd., 20 mmφ) L / D = 25), a T-die having a width of 150 mm was attached, the take-up speed was adjusted, and a film-like test piece having a thickness of 100 μm was produced. Using the obtained film as a core material, a pressure-sensitive adhesive layer (A) from which one release film was peeled was bonded to both surfaces thereof to produce a laminated pressure-sensitive adhesive sheet. Table 1 shows the results of evaluating the characteristics of the obtained test pieces.

Example 2
The core material obtained in Example 1 is an electron beam at an acceleration voltage of 200 kV and a dose of 350 kGy using an EB irradiation apparatus (“TYPE; CB250 / 15 / 180L” manufactured by Iwasaki Electric Co., Ltd.) in a nitrogen atmosphere at room temperature. Were cross-linked by irradiation. A laminated pressure-sensitive adhesive sheet was prepared by laminating the pressure-sensitive adhesive layer (A) from which one release film was peeled off on both surfaces of the obtained film as a core material. Table 1 shows the results of evaluating the characteristics of the obtained test pieces.

Example 3
Using a corona treatment device (manufactured by Kasuga Denki Co., Ltd.) with electrodes covered with ceramics on both sides of the core film obtained in Example 2, discharge treatment was performed twice under conditions of an output of 300 W and a conveyance speed of 5 m / min. Carried out. Furthermore, the adhesive film (A) which peeled one peeling film on both surfaces was used as a core material, and the lamination adhesive sheet was produced. Table 1 shows the results of evaluating the characteristics of the obtained test pieces.

Example 4
A laminated adhesive sheet was prepared in the same procedure as in Example 3 except that the thickness of the film was 200 μm.

Comparative Example 1
Using a PET film (Toyobo Co., Ltd., Cosmo Shine A4300, thickness of 100 μm) as a core material, an adhesive layer (A) from which one release film was peeled off was bonded to both surfaces to prepare a laminated adhesive sheet. Table 1 shows the results of evaluating the characteristics of the obtained test pieces.

Comparative Example 2
A non-yellowing polyurethane film (manufactured by ATT Co., Ltd., RP95UN-XP, thickness 100 μm) was used as a core material, and an adhesive layer (A) from which one release film was peeled off was bonded to both surfaces to prepare a laminated adhesive sheet. Table 1 shows the results of evaluating the characteristics of the obtained test pieces.

Comparative Example 3
Without using a core material, two adhesive layers (A) were bonded together to produce a laminated adhesive sheet. Table 1 shows the results of evaluating the characteristics of the obtained test pieces.

  As apparent from Table 1, the storage modulus ratio is larger in the example than in the comparative example, and both the step absorbability and the reworkability can be achieved. In particular, in Examples 3 and 4, floating and peeling can be prevented even under high temperature and high humidity, and the generation of bubbles is remarkably suppressed. Moreover, in an Example, it has moderate stress, an in-plane retardation is small, and it is excellent in optical isotropy. Furthermore, in an Example, it has moderate surface energy and is excellent also in adhesiveness with an adhesive layer.

  Since the transparent pressure-sensitive adhesive sheet of the present invention is excellent in step followability and reworkability, it is suitable for bonding various members (particularly, members having convex portions on the surface). Moreover, since a transparent adhesive sheet is excellent also in an optical characteristic, it can be utilized for bonding of various optical members. Examples of the optical member include optical glass, optical lens, optical film (for example, hard coat film, antiglare film, antireflection film, polarizing film, retardation film, optical isotropic film, transparent conductive film, electromagnetic Prevention film, viewing angle control film, etc.). The transparent adhesive sheet of this invention can be utilized in order to adhere | attach the same kind or different kind of optical member among the said optical members. The transparent adhesive sheet of the present invention is an electronic device provided with the above optical member, for example, a display device [for example, a display device having a flat panel display (for example, liquid crystal display, plasma display, organic EL), touch panel (optical method). , Ultrasonic display, capacitive method, resistive film method, etc.], electronic devices equipped with these display devices [for example, mobile phones (smartphones, etc.), electronic paper, PDA (Portable Device) Assistance) and the like].

Claims (14)

A transparent pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on at least one surface of a core material film formed of an uncrosslinked body or a crosslinked body of a chain olefin-cyclic olefin copolymer,
The core film has a storage elastic modulus at 60 ° C. of 1 × 10 ⁴ to 1 × 10 ⁸ Pa, and a storage elastic modulus at 25 ° C. of 50 to 5 × with respect to a storage elastic modulus of 1 at 60 ° C. 10 ⁵ a is transparent adhesive sheet.   The transparent adhesive sheet according to claim 1, wherein the core material film is formed of a radiation cross-linked body or an electron beam cross-linked body of a chain olefin-cyclic olefin copolymer.   The transparent pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the chain olefin-cyclic olefin copolymer has a glass transition temperature of 10 to 50 ° C.   The transparent adhesive sheet according to any one of claims 1 to 3, wherein in the chain olefin-cyclic olefin copolymer, the ratio of the cyclic olefin is 15 to 50 mol% with respect to the total of the chain olefin and the cyclic olefin. . A transparent adhesive sheet comprising a core material film formed of an electron beam cross-linked body of a chain olefin-cyclic olefin copolymer, and an acrylic adhesive layer on at least one surface of the core material film,
The glass transition temperature of the chain olefin-cyclic olefin copolymer is more than 30 ° C and not more than 50 ° C,
In the chain olefin-cyclic olefin copolymer, the ratio of the cyclic olefin is more than 15 mol% and not more than 40 mol% with respect to the total of the chain olefin and the cyclic olefin,
The storage elastic modulus at 60 ° C. of the core film is 1 × 10 ^{5 to} 5 × 10 ⁷ Pa, and the storage elastic modulus at 25 ° C. is 70 to 1000 with respect to the storage elastic modulus 1 at 60 ° C. A transparent adhesive sheet.   The transparent adhesive sheet according to any one of claims 1 to 5, wherein a tensile stress at 100% elongation at room temperature of the core material film is 15 to 100 MPa.   The transparent adhesive sheet according to any one of claims 1 to 6, wherein an in-plane retardation of the core material film at a wavelength of 590 nm is 10 nm or less in terms of a thickness of 100 µm.   The transparent adhesive sheet according to claim 1, wherein the core film has a thickness of 20 to 400 μm.   The transparent adhesive sheet according to any one of claims 1 to 8, wherein the core film has a surface tension of 40 to 70 mN / m.   The transparent adhesive sheet according to any one of claims 1 to 9, wherein the surface of the core film is subjected to corona treatment or plasma treatment.   The transparent adhesive sheet according to any one of claims 1 to 10, wherein the core material film is formed by extruding a chain olefin-cyclic olefin copolymer.   The transparent adhesive sheet according to any one of claims 1 to 11, which is used for bonding two panels selected from a touch panel, a liquid crystal display panel and a protective panel.   The method of manufacturing the transparent adhesive sheet of Claim 1 by laminating | stacking an adhesive layer on the at least one surface of the core film formed with the chain olefin-cyclic olefin copolymer.   A film formed of a chain olefin-cyclic olefin copolymer is irradiated with a radiation or an electron beam to be crosslinked to form a core film, and an adhesive layer is laminated on at least one surface of the core film. The method of manufacturing the transparent adhesive sheet in any one of Claims 2-12 by doing.