JP6870929B2 - Double-sided adhesive tape for optics - Google Patents

Description

The present invention relates to a double-sided adhesive tape for optical applications having light transmission.

In the technical field of flat panel displays, double-sided adhesive tape for optics is used in the manufacture of display devices. Specifically, a display device such as a liquid crystal display or an input device such as a touch panel has a laminated structure portion including various substrates and films, and in order to join predetermined components adjacent to each other in the laminated structure. Alternatively, a transparent double-sided adhesive tape may be used to fill the gaps between adjacent parts. Such optical double-sided adhesive tapes are described, for example, in Patent Documents 1 to 3 below.

Japanese Unexamined Patent Publication No. 2012-78431 Japanese Unexamined Patent Application Publication No. 2015-200938 Japanese Unexamined Patent Publication No. 2016-26321

As the base material of the above-mentioned double-sided adhesive tape for optics, a polyester-based base material may be adopted because it is excellent in various properties such as heat resistance, transparency, and dimensional stability. For example, PET film, which is a polyester-based base material for optical use for double-sided adhesive tape for optics, is extruded into a film by the T-die method in the manufacturing process, and then the flow direction or mechanical direction of the film. It is known that a biaxial stretching process including stretching in the (MD) direction and stretching in the width direction (TD) is often performed.

Further, the double-sided adhesive tape for optics may be required to have good hand-cutting property from the viewpoint of work efficiency and the like.

The present invention has been conceived under the above circumstances, and is suitable for realizing both good hand-cutting property and high reworkability while having a polyester-based base material. It is an object of the present invention to provide a double-sided adhesive tape for use.

The double-sided adhesive tape for optics provided by the present invention has a laminated structure including a first pressure-sensitive adhesive layer, a second pressure-sensitive adhesive layer, and a transparent base material between the first and second pressure-sensitive adhesive layers. The transparent base material is a uniaxially stretched polyester-based base material in the width direction of the base material and has a thickness of 75 μm or more. The polyester-based base material refers to a base material such as a film or a sheet containing the polyester-based resin in the largest weight ratio in the constituent material. The uniaxially stretched polyester-based base material in the width direction of the base material is a width direction (MD) orthogonal to, for example, the flow direction or the mechanical direction (MD) of the extruded film-like body after extrusion molding of the raw material resin material in the manufacturing process of the polyester base material. It refers to a polyester-based base material that has undergone uniaxial stretching treatment to TD). The first pressure-sensitive adhesive layer and / or the second pressure-sensitive adhesive layer contains, for example, at least one selected from the group consisting of acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, and rubber-based pressure-sensitive adhesives. In the double-sided adhesive tape for optics, the Elmendorf tear strength in the substrate width direction is 0.5 N or less, and the Elmendorf tear strength in the substrate machine direction is 1 N or more. The double-sided adhesive tape for optics having the above configuration may take the form of a sheet with a release liner for covering and protecting the adhesive surface of each adhesive layer, or the double-sided adhesive tape for optics and the release liner. It may take a form of being wound in a roll shape with a release liner so that and are alternately arranged.

As described above, the transparent base material of the double-sided adhesive tape for optics is a polyester-based base material. Such a configuration is suitable for enjoying various properties that are easily exhibited in a polyester-based base material, such as heat resistance, transparency, and dimensional stability, in the double-sided adhesive tape base material and thus in the double-sided adhesive tape for optics. is there.

Further, as described above, the transparent base material of the double-sided adhesive tape for optics is a uniaxially stretched polyester-based base material having a thickness of 75 μm or more in the width direction. The tear strength such as the Elmendorf tear strength in the double-sided adhesive tape is strongly controlled by the mechanical properties of the base material. In this configuration, the Elmendorf tear strength in the width direction of the base material is 0. It is suitable for realizing the above-mentioned configuration in which the Elmendorf tear strength in the direction of the base material machine is 1 N or more and 5 N or less.

In addition, as described above, the double-sided adhesive tape for optics has an Elmendorf tear strength in the substrate width direction of 0.5 N or less and an Elmendorf tear strength in the substrate machine direction of 1 N or more. Such a configuration is suitable for realizing good hand-cutting property in the substrate width direction in which the Ermendorf tear strength is 0.5 N or less, which is relatively significantly low, in the double-sided adhesive tape for optics. At the same time, the configuration in which the Ermendorf tear strength is 1N or more, which is more than twice the base material width direction in the base material mechanical direction, enhances the directivity of the double-sided adhesive tape for optics with respect to tearing in the base material width direction. It is suitable for. Therefore, in this configuration, when the double-sided adhesive tape for optics is attached to the adherend, a peeling force is applied in the direction of the base material machine of the adhesive tape to remove the adhesive tape from the adherend. It is suitable for proper peeling without tearing. Specifically, in the work (rework work) in which the double-sided adhesive tape for optics is attached to the adherend, and then the adhesive tape is once peeled off and reattached, a peeling force is applied in the direction of the base material machine of the adhesive tape. It is suitable for appropriately peeling the adhesive tape from the adherend without tearing it. The optical double-sided adhesive tape, which is easily torn not only in the width direction of the base material but also in the machine direction of the base material, tends to be easily torn at the time of peeling in the rework work, and it tends to be difficult to properly peel off from the adherend. The torn double-sided optical adhesive tape cannot be used for re-bonding. On the other hand, this double-sided adhesive tape for optics has a base material mechanical direction Elmendorf tear strength that is sufficiently larger than the base material width direction Elmendorf tear strength, which is suitable for achieving good hand-cutting property in the base material width direction. Since it has, it is suitable for appropriately peeling from the adherend without tearing in the rework work.

As described above, the double-sided adhesive tape for optics is suitable for achieving both good hand-cutting property and high reworkability while having a polyester-based base material.

Preferably, the thickness of the first pressure-sensitive adhesive layer is 5 μm or more, and the thickness of the second pressure-sensitive adhesive layer is 5 μm or more. Such a configuration is suitable for realizing sufficient adhesive force to the adherend in the double-sided adhesive tape for optics.

Preferably, the haze in the thickness direction of the double-sided adhesive tape for optics is 3% or less. Such a configuration is suitable for an optical adhesive tape that requires transparency.

It is a partial cross-sectional view of the double-sided adhesive tape for optics which concerns on one Embodiment of this invention.

FIG. 1 is a partial cross-sectional view of an adhesive tape X which is an optical double-sided adhesive tape according to an embodiment of the present invention. The pressure-sensitive adhesive tape X has a laminated structure including a base material 10 which is a transparent base material, a pressure-sensitive adhesive layer 11 which is a first pressure-sensitive adhesive layer, and a pressure-sensitive adhesive layer 12 which is a second pressure-sensitive adhesive layer. The adhesive tape X can be used in the manufacture of display devices such as flat panel displays, for example. When a display device such as a liquid crystal display or an input device such as a touch panel has a laminated structure including various substrates and films, it is necessary to join predetermined adjacent parts in the laminated structure or adjacent parts. Adhesive tape X is available to fill the gaps between them.

The base material 10 of the pressure-sensitive adhesive tape X is a portion of the pressure-sensitive adhesive tape X that is located between the pressure-sensitive adhesive layers 11 and 12 and functions as a support, and is a light-transmitting base material uniaxially stretched polyester-based base material in the width direction. is there.

The polyester-based base material refers to a base material such as a film or a sheet containing the polyester-based resin in the largest weight ratio in the constituent material. Examples of the constituent material of such a base material 10 include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and poly-1,4-cyclohexanedimethylene terephthalate.

The uniaxially stretched polyester-based base material in the width direction of the base material is a width direction (MD) orthogonal to, for example, the flow direction or the mechanical direction (MD) of the extruded film-like body after extrusion molding of the raw material resin material in the manufacturing process of the polyester base material. It refers to a polyester-based base material that has undergone uniaxial stretching treatment to TD). The draw ratio in the width direction of the base material 10 which is such a uniaxially stretched polyester-based base material in the width direction is, for example, 2.5 times or more, preferably 3 times or more. The draw ratio is, for example, 6 times or less, preferably 5.5 times or less.

The thickness of the base material 10 is 75 μm or more, preferably 80 μm or more. The thickness of the base material 10 is, for example, 150 μm or less, preferably 125 μm or less.

The in-plane retardation of the base material 10 is preferably 1500 nm or more, more preferably 3000 nm or more, and more preferably 6000 nm or more. In the present embodiment, the in-plane phase difference of the base material 10 is the in-plane phase difference of the base material 10 related to birefringence when light having a wavelength of 590 nm is transmitted to the base material 10 at 23 ° C. in a plane parallel to the main surface of the base material 10. Between the two orthogonal optical spindles (slow-phase axis and phase-advancing axis), the polarizing component (abnormal ray) that oscillates in the direction of the slow-phase axis and the polarization component (normal ray) that oscillates in the direction of the phase-advancing axis The phase difference that occurs. For the in-plane phase difference, the refractive index (relatively large) of the abnormal light beam is nx, the refractive index (relatively small) of the ordinary light ray is ny, and the thickness of the base material 10 is d (nm). In this case, the value is represented by (nx−ny) × d.

The surface of the base material 10 on the pressure-sensitive adhesive layer 11 side and the surface on the pressure-sensitive adhesive layer 12 side may each be subjected to surface treatment for improving the adhesiveness with the pressure-sensitive adhesive layer. Examples of such a surface treatment include a physical treatment such as a corona treatment and a plasma treatment, and a chemical treatment such as an undercoat treatment.

The pressure-sensitive adhesive layers 11 and 12 of the pressure-sensitive adhesive tape X each contain a pressure-sensitive adhesive as a main agent and have light transmittance. The main agent is a component that occupies the largest weight ratio among the contained components. The pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 is at least one selected from the group consisting of, for example, an acrylic polymer as an acrylic pressure-sensitive adhesive, a polyurethane as a urethane-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and a rubber-based pressure-sensitive adhesive. including. From the viewpoint of achieving both the adhesive strength required for the adhesive layer of the optical double-sided adhesive tape and high transparency, an acrylic polymer is used as the adhesive in the adhesive layers 11 and 12. Is preferable. Further, the pressure-sensitive adhesive layer 11 has an adhesive surface 11a that can be attached to the adherend, and the pressure-sensitive adhesive layer 12 has an adhesive surface 12a that can be attached to the adherend.

When the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 contains an acrylic polymer that is an acrylic pressure-sensitive adhesive, the acrylic polymer is preferably an acrylic acid alkyl ester having a linear or branched alkyl group. , And / or a monomer unit derived from a methacrylic acid alkyl ester having a linear or branched alkyl group, as the main monomer unit having the largest weight ratio. In the following, "(meth) acrylic" is used to represent "acrylic" and / or "methacryl".

A (meth) acrylic acid alkyl ester having a linear or branched alkyl group for forming a monomer unit of the acrylic polymer, that is, a straight chain contained in a monomer component for forming the acrylic polymer. Examples of the (meth) acrylic acid alkyl ester having a state or branched alkyl group include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, and isopropyl (meth) acrylic acid. N-butyl (meth) acrylate, s-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, (meth) ) Hexyl acrylate, (meth) heptyl acrylate, (meth) octyl acrylate, (meth) 2-ethylhexyl acrylate, (meth) isooctyl acrylate, (meth) nonyl acrylate, (meth) isononyl acrylate, ( Decyl acrylate, Isodecyl (meth) acrylate, Undecyl (meth) acrylate, Dodecyl (meth) acrylate, Tridecyl (meth) acrylate, Tetradecyl (meth) acrylate, Pentadecyl (meth) acrylate, (meth) ) Hexadecyl acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isostearyl (meth) acrylate, nonadecil (meth) acrylate, and eicosyl (meth) acrylate, which have 1 to 20 carbon atoms. Examples thereof include (meth) acrylic acid alkyl esters having linear or branched alkyl groups. As the (meth) acrylic acid alkyl ester for the acrylic polymer, one kind of (meth) acrylic acid alkyl ester may be used, or two or more kinds of (meth) acrylic acid alkyl esters may be used. .. In the present embodiment, the (meth) acrylic acid alkyl ester for the acrylic polymer is preferably at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate, and isostearyl acrylate. Is used.

The proportion of the monomer unit derived from the (meth) acrylic acid alkyl ester having a linear or branched alkyl group in the acrylic polymer is preferably 50% by weight or more, more preferably 60% by weight or more, more preferably. Is 70% by weight or more, more preferably 80% by weight or more, and more preferably 90% by weight or more. That is, the proportion of the (meth) acrylic acid alkyl ester in the monomer component composition of the raw material for forming the acrylic polymer is preferably 50% by weight or more, more preferably 60% by weight or more, and more preferably 70% by weight or more. , More preferably 80% by weight or more, more preferably 90% by weight or more. The acrylic polymer has a monomer unit structure derived from the monomer component composition with such a (meth) acrylic acid alkyl ester ratio. The configuration relating to the proportion of (meth) acrylic acid alkyl ester having a linear or branched alkyl group includes basic properties such as adhesiveness of an acrylic polymer as an acrylic pressure-sensitive adhesive, including the acrylic polymer. It is suitable for proper expression in the formed pressure-sensitive adhesive layer.

The acrylic polymer contained in the pressure-sensitive adhesive layer 11 and the pressure-sensitive adhesive layer 12 may contain a monomer unit derived from an alicyclic monomer. Examples of the alicyclic monomer for forming the monomer unit of the acrylic polymer, that is, the alicyclic monomer contained in the monomer component for forming the acrylic polymer, include (meth) acrylic acid cycloalkyl ester, two. Examples thereof include a (meth) acrylic acid ester having a cyclic hydrocarbon ring and a (meth) acrylic acid ester having three or more hydrocarbon rings. Examples of the (meth) acrylic acid cycloalkyl ester include (meth) acrylic acid cyclopentyl, (meth) acrylic acid cyclohexyl, (meth) acrylic acid cycloheptyl, and (meth) acrylic acid cyclooctyl. Examples of the (meth) acrylic acid ester having a bicyclic hydrocarbon ring include bornyl (meth) acrylate and isobornyl (meth) acrylate. Examples of the (meth) acrylic acid ester having three or more hydrocarbon rings include (meth) dicyclopentanyl acrylate, (meth) dicyclopentanyloxyethyl acrylate, and tricyclopenta (meth) acrylate. Nyl, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, and 2-ethyl-2-adamantyl (meth) acrylate. As the alicyclic monomer for the acrylic polymer, one kind of alicyclic monomer may be used, or two or more kinds of alicyclic monomers may be used. In the present embodiment, as the alicyclic monomer for the acrylic polymer, at least one selected from the group consisting of cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, and isobornyl methacrylate is preferably used.

The proportion of the monomer unit derived from the alicyclic monomer in the acrylic polymer is preferably 5 to 60% by weight from the viewpoint of realizing appropriate flexibility in the pressure-sensitive adhesive layer formed containing the acrylic polymer. , More preferably 10 to 50% by weight.

The acrylic polymer contained in the pressure-sensitive adhesive layer 11 and the pressure-sensitive adhesive layer 12 may contain a monomer unit derived from a hydroxyl group-containing monomer. The hydroxyl group-containing monomer is a monomer having at least one hydroxyl group in the monomer unit. When the acrylic polymer in the pressure-sensitive adhesive layers 11 and 12 contains a hydroxyl group-containing monomer unit, adhesiveness and appropriate cohesive force can be easily obtained in the pressure-sensitive adhesive layers 11 and 12.

Examples of the hydroxyl group-containing monomer for forming the monomer unit of the acrylic polymer, that is, the hydroxyl group-containing monomer contained in the monomer component for forming the acrylic polymer, include a hydroxyl group-containing (meth) acrylic acid ester and vinyl alcohol. , And allyl alcohol. Examples of the hydroxyl group-containing (meth) acrylic acid ester include (meth) acrylic acid 2-hydroxyethyl, (meth) acrylic acid 2-hydroxypropyl, (meth) acrylic acid 3-hydroxypropyl, and (meth) acrylic acid 4-. Hydroxybutyl, 6-hydroxyhexyl (meth) acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) acrylate. Methyl is mentioned. As the hydroxyl group-containing monomer for the acrylic polymer, one kind of hydroxyl group-containing monomer may be used, or two or more kinds of hydroxyl group-containing monomers may be used. In the present embodiment, as the hydroxyl group-containing monomer for the acrylic polymer, preferably 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4 acrylate. At least one selected from the group consisting of -hydroxybutyl and 4-hydroxybutyl methacrylate is used.

The proportion of the monomer unit derived from the hydroxyl group-containing monomer in the acrylic polymer is preferably 1% by weight or more, more preferably 2% by weight or more, more preferably 3% by weight or more, still more preferably 5% by weight or more, more preferably. Is 7% by weight or more, more preferably 10% by weight or more. The proportion of the monomer unit derived from the hydroxyl group-containing monomer in the acrylic polymer is preferably 20% by weight or less, more preferably 18% by weight or less. These configurations regarding the ratio of the hydroxyl group-containing monomer are suitable for realizing adhesiveness and appropriate cohesive force in the pressure-sensitive adhesive layer formed by containing the acrylic polymer.

The acrylic polymer contained in the pressure-sensitive adhesive layer 11 and the pressure-sensitive adhesive layer 12 may contain a monomer unit derived from a nitrogen atom-containing monomer. A nitrogen atom-containing monomer is a monomer that will have at least one nitrogen atom in the monomer unit. When the acrylic polymer in the pressure-sensitive adhesive layers 11 and 12 contains a nitrogen atom-containing monomer unit, hardness and good adhesion reliability can be easily obtained in the pressure-sensitive adhesive layers 11 and 12.

Examples of the nitrogen atom-containing monomer for forming the monomer unit of the acrylic polymer, that is, the nitrogen atom-containing monomer contained in the monomer component for forming the acrylic polymer, include N-vinyl cyclic amide and (meth). Examples include acrylamides. Examples of the N-vinyl cyclic amide which is a nitrogen atom-containing monomer include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, and N-vinyl. -1,3-Oxazine-2-one and N-vinyl-3,5-morpholindione can be mentioned. Examples of (meth) acrylamides as nitrogen atom-containing monomers include (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-butyl (meth) acrylamide, and N-octyl (). Examples include meta) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, and N, N-diisopropyl (meth) acrylamide. As the nitrogen atom-containing monomer for the acrylic polymer, one kind of nitrogen atom-containing monomer may be used, or two or more kinds of nitrogen atom-containing monomers may be used. In this embodiment, N-vinyl-2-pyrrolidone is preferably used as the nitrogen atom-containing monomer for the acrylic polymer.

The proportion of the monomer unit derived from the nitrogen atom-containing monomer in the acrylic polymer is adjusted from the viewpoint of realizing appropriate hardness, adhesiveness, and transparency in the pressure-sensitive adhesive layer formed by containing the acrylic polymer. It is preferably 1% by weight or more, more preferably 3% by weight or more, and more preferably 5% by weight or more. Further, the proportion of the monomer unit derived from the nitrogen atom-containing monomer in the acrylic polymer is too hard from the viewpoint of realizing sufficient transparency in the pressure-sensitive adhesive layer formed containing the acrylic polymer. It is preferably 30% by weight or less, more preferably 25% by weight or less, from the viewpoint of suppressing the above and realizing good adhesive reliability.

The acrylic polymer contained in the pressure-sensitive adhesive layer 11 and the pressure-sensitive adhesive layer 12 may contain a monomer unit derived from a carboxy group-containing monomer. The carboxy group-containing monomer is a monomer having at least one carboxy group in the monomer unit. When the acrylic polymer in the pressure-sensitive adhesive layers 11 and 12 contains a carboxy group-containing monomer unit, good adhesion reliability may be easily obtained in the pressure-sensitive adhesive layers 11 and 12.

Examples of the carboxy group-containing monomer for forming the monomer unit of the acrylic polymer, that is, the carboxy group-containing monomer contained in the monomer component for forming the acrylic polymer include (meth) acrylic acid and itaconic acid. Examples include maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. As the carboxy group-containing monomer for the acrylic polymer, one kind of carboxy group-containing monomer may be used, or two or more kinds of carboxy group-containing monomers may be used. In this embodiment, acrylic acid is preferably used as the carboxy group-containing monomer for the acrylic polymer.

The ratio of the monomer unit derived from the carboxy group-containing monomer in the acrylic polymer is the same as that of the polar group when the polar group is present on the surface of the adherend in the pressure-sensitive adhesive layer formed by containing the acrylic polymer. From the viewpoint of obtaining the contribution of interaction and ensuring good adhesion reliability, it is preferably 0.1% by weight or more, more preferably 0.5% by weight or more. Further, the proportion of the monomer unit derived from the carboxy group-containing monomer in the acrylic polymer suppresses the pressure-sensitive adhesive layer formed containing the acrylic polymer from becoming too hard, and realizes good adhesive reliability. From this point of view, it is preferably 20% by weight or less, more preferably 15% by weight or less.

The acrylic polymer contained in the pressure-sensitive adhesive layer 11 and the pressure-sensitive adhesive layer 12 may have a cross-linked structure derived from a polyfunctional (meth) acrylate which is a copolymerizable cross-linking agent. Examples of the polyfunctional (meth) acrylate include 1,6-hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, and (poly) propylene glycol di (meth) acrylate. ) Acrylate, Neopentyl glycol di (meth) acrylate, Pentaerythritol di (meth) acrylate, Pentaerythritol tri (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, Trimethylol propanthry (meth) acrylate, Tetramethylol methanetri Examples include (meth) acrylates, allyl (meth) acrylates, and vinyl (meth) acrylates. As the polyfunctional (meth) acrylate for the acrylic polymer, one kind of polyfunctional (meth) acrylate may be used, or two or more kinds of polyfunctional (meth) acrylate may be used. In this embodiment, the polyfunctional (meth) acrylate for the acrylic polymer is preferably selected from the group consisting of 1,6-hexanediol diacrylate, dipentaerythritol hexaacrylate, and trimethylolpropane triacrylate. At least one is used.

The proportion of the monomer unit derived from the polyfunctional (meth) acrylate in the acrylic polymer is preferably 0.01% by weight or more, more preferably 0.03% by weight or more, and more preferably 0.05% by weight or more. .. The proportion of the monomer unit derived from polyfunctional (meth) acrylate in the acrylic polymer is preferably 1% by weight or less, more preferably 0.5% by weight or less. These configurations regarding the proportion of the polyfunctional (meth) acrylate are suitable for achieving appropriate hardness and adhesiveness in the pressure-sensitive adhesive layer formed containing the acrylic polymer.

When the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 contains the above acrylic polymer as a pressure-sensitive adhesive, the content of the acrylic polymer in the pressure-sensitive adhesive layer is, for example, 85 to 100% by weight.

Each of the pressure-sensitive adhesive layers 11 and 12 may contain an acrylic oligomer having a raw material monomer composition different from that of the above-mentioned acrylic polymer from the viewpoint of achieving high adhesiveness at room temperature. When the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 contains such an acrylic-based oligomer, the content of the acrylic-based oligomer in the pressure-sensitive adhesive layer is 100 parts by weight of the pressure-sensitive adhesive or the acrylic-based polymer in the pressure-sensitive adhesive layer. For example, it is 0.1 to 20 parts by weight.

The oligomer preferably has a monomer unit derived from a (meth) acrylic acid ester having a cyclic structure (ring-containing (meth) acrylic acid ester) and a (meth) acrylic having a linear or branched alkyl group. It is a polymer containing a monomer unit derived from an acid alkyl ester.

The ring-containing (meth) acrylic acid ester for forming the monomer unit of the oligomer, that is, the ring-containing (meth) acrylic acid ester contained in the monomer component for forming the oligomer is, for example, (meth) acrylic acid. Cycloalkyl esters, (meth) acrylic acid esters with bicyclic hydrocarbon rings, (meth) acrylic acid esters with three or more hydrocarbon rings, and (meth) acrylic acid esters with aromatic rings. Be done. Examples of the (meth) acrylic acid cycloalkyl ester include (meth) acrylic acid cyclopentyl, (meth) acrylic acid cyclohexyl, (meth) acrylic acid cycloheptyl, and (meth) acrylic acid cyclooctyl. Examples of the (meth) acrylic acid ester having a bicyclic hydrocarbon ring include bornyl (meth) acrylate and isobornyl (meth) acrylate. Examples of the (meth) acrylic acid ester having three or more hydrocarbon rings include (meth) dicyclopentanyl acrylate, (meth) dicyclopentanyloxyethyl acrylate, and tricyclopenta (meth) acrylate. Nyl, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, and 2-ethyl-2-adamantyl (meth) acrylate. Examples of the (meth) acrylic acid ester having an aromatic ring include phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, and benzyl (meth) acrylate. As the ring-containing (meth) acrylic acid ester for the oligomer, one kind of ring-containing (meth) acrylic acid ester may be used, or two or more kinds of ring-containing (meth) acrylic acid esters may be used. .. In this embodiment, as the ring-containing (meth) acrylic acid ester for the oligomer, at least one selected from the group consisting of dicyclopentanyl acrylate and dicyclopentanyl methacrylate is preferably used.

The proportion of the monomer unit derived from the ring-containing (meth) acrylic acid ester in the above oligomer is preferably 10 to 90% by weight from the viewpoint of realizing appropriate flexibility in the pressure-sensitive adhesive layer formed containing the oligomer. , More preferably 20 to 80% by weight, more preferably 35 to 80% by weight.

A (meth) acrylic acid alkyl ester having a linear or branched alkyl group for forming a monomer unit of the oligomer, that is, a linear or branched contained in a monomer component for forming the oligomer. Examples of the (meth) acrylic acid alkyl ester having a chain-like alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth). N-butyl acrylate, s-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, (meth) acrylate Hexil, (meth) heptyl acrylate, (meth) octyl acrylate, (meth) 2-ethylhexyl acrylate, (meth) isooctyl acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, (meth) acrylic Decyl Acid, Isodecyl (Meta) Acrylic Acid, Undecyl (Meta) Acrylic Acid, Dodecyl (Meta) Acrylic Acid, Tridecyl (Meta) Acrylic Acid, Tetradecyl (Meta) Acrylic Acid, Pentadecyl (Meta) Acrylic Acid, (Meta) Acrylic Acid Linear with 1 to 20 carbon atoms, such as hexadecyl, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isostearyl (meth) acrylate, nonadecil (meth) acrylate, and eicosyl (meth) acrylate. Alternatively, a (meth) acrylic acid alkyl ester having a branched alkyl group can be mentioned. As the (meth) acrylic acid alkyl ester for the above oligomer, one kind of (meth) acrylic acid alkyl ester may be used, or two or more kinds of (meth) acrylic acid alkyl esters may be used. In this embodiment, methyl methacrylate is preferably used as the (meth) acrylic acid alkyl ester for the oligomer.

The proportion of the monomer unit derived from the (meth) acrylic acid alkyl ester having a linear or branched alkyl group in the above oligomer realizes an appropriate elastic modulus in the pressure-sensitive adhesive layer formed containing the oligomer. From this point of view, it is preferably 10 to 90% by weight, more preferably 15 to 80% by weight, and more preferably 20 to 60% by weight.

The above oligomer is derived from a carboxy group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, a cyano group-containing monomer, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, an isocyanate group-containing monomer, and an imide group-containing monomer. It may contain a monomer unit to be used.

The weight average molecular weight (Mw) of the oligomer is, for example, 1000 to 30,000, preferably 1000 to 20000, and more preferably 1500 to 10000. From the viewpoint of ensuring good adhesive strength in the pressure-sensitive adhesive layer formed containing the oligomer, the weight average molecular weight of the oligomer is preferably 1000 or more. On the other hand, from the viewpoint of ensuring the adhesive strength of the pressure-sensitive adhesive layer formed containing the oligomer, particularly at room temperature, the weight average molecular weight of the oligomer is preferably 30,000 or less.

The weight average molecular weight of the oligomer can be measured by a gel permeation chromatography (GPC) method. For example, using a GPC measuring device (trade name “HLC-8120GPC”, manufactured by Tosoh Corporation), the weight average molecular weight (Mw) can be obtained as a standard polystyrene conversion value under the following measurement conditions.
-Column: TSKgel SuperAWM-H (upstream side, manufactured by Tosoh Corporation), TSKgel SuperAW4000 (manufactured by Tosoh Co., Ltd.) and TSKgel SuperAW2500 (downstream side, manufactured by Tosoh Corporation) are connected in series.-Column size: 6 for each column .0mmφ x 150mm
-Column temperature (measurement temperature): 40 ° C
-Eluent: tetrahydrofuran (THF)
・ Flow rate: 0.4 mL / min ・ Sample injection volume: 20 μL
-Sample concentration: Approximately 2.0 g / L (tetrahydrofuran solution)
・ Standard sample: Polystyrene ・ Detector: Differential refractometer (RI)

The pressure-sensitive adhesive layers 11 and 12 may each contain a silane coupling agent. Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-phenyl-aminopropyltrimethoxysilane. .. Examples of the silane coupling agent include commercially available products such as the trade name "KBM-403" (manufactured by Shin-Etsu Chemical Co., Ltd.). As the silane coupling agent, γ-glycidoxypropyltrimethoxysilane is preferable.

When the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 contains a silane coupling agent, the content of the silane coupling agent in the pressure-sensitive adhesive layer is 100 parts by weight of the pressure-sensitive adhesive or acrylic polymer in the pressure-sensitive adhesive layer. On the other hand, it is preferably 0.01 part by weight or more, and more preferably 0.02 part by weight or more. The content of the silane coupling agent in the pressure-sensitive adhesive layer is preferably 1 part by weight or less, more preferably 0.5 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The configuration regarding the content of the silane coupling agent is suitable for achieving high adhesiveness under humidifying conditions, particularly high adhesiveness to glass, in the pressure-sensitive adhesive layer formed containing the silane coupling agent. Is.

The pressure-sensitive adhesive layers 11 and 12 may each contain an ultraviolet absorber. An ultraviolet absorber is a chemical species that can efficiently absorb ultraviolet rays and can convert the absorbed energy into heat, infrared rays, or the like and emit it. Examples of such UV absorbers include benzotriazole-based UV absorbers, hydroxyphenyltriazine-based UV absorbers, salicylate ester-based UV absorbers, benzophenone-based UV absorbers, oxybenzophenone-based UV absorbers, and cyanoacrylate-based UV absorbers. Examples include UV absorbers. The pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 may contain one kind of ultraviolet absorber, or may contain two or more kinds of ultraviolet absorbers.

Examples of the benzotriazole-based ultraviolet absorber include 2- (2-hydroxy-5-tert-butylphenyl) -2-H-benzotriazole (trade name "TINUVIN PS", manufactured by BASF), benzenepropanoic acid 3- (2H). -Benzotriazole-2-yl) -5- (1,1-dimethylethyl) -4-hydroxy alkyl ester having 7 to 9 carbon atoms (trade name "TINUVIN 384-2", manufactured by BASF), octyl 3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-Chloro-2H-benzotriazole-2-yl) phenyl] Propionate mixture (trade name "TINUVIN 109", manufactured by BASF), 2- (2H-benzotriazole-2-yl) -4,6-bis ( 1-Methyl-1-phenylethyl) phenol (trade name "TINUVIN 900", manufactured by BASF), 2- (2H-benzotriazole-2-yl) -6- (1-methyl-1-phenylethyl) -4 -(1,1,3,3-Tetramethylbutyl) phenol (trade name "TINUVIN 928", manufactured by BASF), methyl 3- (3- (2H-benzotriazole-2-yl) -5-tert-butyl- Reaction product of 4-hydroxyphenyl) propionate and polyethylene glycol 300 (trade name "TINUVIN 1130", manufactured by BASF), 2- (2H-benzotriazole-2-yl) -p-cresol (trade name "TINUVIN P") , 2 (2H-benzotriazole-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (trade name "TINUVIN 234", manufactured by BASF), 2- [5-Chloro-2H-benzotriazole-2-yl] -4-methyl-6- (tert-butyl) phenol (trade name "TINUVIN 326", manufactured by BASF), 2- (2H-benzotriazole-2-) Il) -4,6-di-tert-pentylphenol (trade name "TINUVIN 328", manufactured by BASF), 2- (2H-benzotriazole-2-yl) -4- (1,1,3,3-) Tetramethylbutyl) phenol (trade name "TINUVIN 329", manufactured by BASF), 2,2'-methylenebis [6- (2H-benzotriazole) Riazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (trade name "TINUVIN 360", manufactured by BASF), 2- (2H-benzotriazole-2-yl)- 6-Dodecyl-4-methylphenol (trade name "TINUVIN 571", manufactured by BASF), 2- [2-hydroxy-3- (3,4,5,6-tetrahydrophthalimide-methyl) -5-methylphenyl] Benzotriazole (trade name "Sumisorb 250", manufactured by Sumitomo Chemical Co., Ltd.) and 2,2'-methylenebis [6- (2H-benzotriazole-2-yl) -4-tert-octylphenol] (trade name "Adecastab LA" -31 ”, manufactured by ADEKA Co., Ltd.).

Examples of the hydroxyphenyltriazine-based ultraviolet absorber include 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine-2-yl) -5-hydroxyphenyl and [(carbon). Reaction product with number 10 to 16 alkyloxy) methyl] oxylane (trade name "TINUVIN 400", manufactured by BASF), 2- [4,6-bis (2,4-dimethylphenyl) -1,3, 5-Triazine-2-yl] -5- [3- (dodecyloxy) -2-hydroxypropoxy] phenol), 2- (2,4-dihydroxyphenyl) -4,6-bis- (2,4-dimethyl) Reaction product of phenyl) -1,3,5-triazine and (2-ethylhexyl) -glycidate (trade name "TINUVIN 405", manufactured by BASF), 2,4-bis (2-hydroxy-4--) Butoxyphenyl) -6- (2,4-dibutoxyphenyl) -1,3,5-triazine (trade name "TINUVIN 460", manufactured by BASF), 2- (4,6-diphenyl-1,3,5 -Triazine-2-yl) -5-[(hexyl) oxy] -phenol (trade name "TINUVIN 1577", manufactured by BASF), 2- (4,6-diphenyl-1,3,5-triazine-2- Il) -5- [2- (2-ethylhexanoyloxy) ethoxy] -phenol (trade name "Adecastab LA-46", manufactured by ADEKA Co., Ltd.), and 2- (2-hydroxy-4- [1-octyl). Oxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine (trade name "TINUVIN 479", manufactured by BASF) can be mentioned.

Examples of the salicylate ester-based ultraviolet absorber include phenyl2-acryloyloxybenzoate, phenyl2-acryloyloxy-3-methylbenzoate, phenyl2-acryloyloxy-4-methylbenzoate, and phenyl2-acryloyloxy-5-methylbenzoate. , Phenyl2-acryloyloxy-3-methoxybenzoate, phenyl2-hydroxybenzoate, phenyl2-hydroxy-3-methylbenzoate, phenyl2-hydroxy-4-methylbenzoate, phenyl2-hydroxy-5-methylbenzoate, phenyl2 -Hydroxy-3-methoxybenzoate and 2,4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate (trade name "TINUVIN 120", manufactured by BASF) can be mentioned.

Examples of benzophenone-based ultraviolet absorbers and oxybenzophenone-based ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, and 2-hydroxy. -4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone (trade name "KEMISORB 111", Chemipro Kasei Co., Ltd.) , 2,2', 4,4'-tetrahydroxybenzophenone (trade name "SEESORB 106", manufactured by Cipro Kasei Co., Ltd.), and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone.

Examples of the cyanoacrylate-based ultraviolet absorber include alkyl2-cyanoacrylate, cycloalkyl2-cyanoacrylate, alkoxyalkyl2-cyanoacrylate, alkenyl2-cyanoacrylate, and alkynyl2-cyanoacrylate.

The ultraviolet absorber contained in the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 has high UV absorption and high photostability, and from the viewpoint that a highly transparent pressure-sensitive adhesive layer can be easily obtained. , Preferably at least one selected from the group consisting of benzotriazole-based UV absorbers, hydroxyphenyltriazine-based UV absorbers, and benzophenone-based UV absorbers. The ultraviolet absorber contained in the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 is more preferably a nitrogen atom in which a hydrocarbon group having 6 or more carbon atoms and a phenyl group having a hydroxyl group as a substituent constitute a benzotriazole ring. It is a benzotriazole-based ultraviolet absorber that is bound to.

When the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 contains an ultraviolet absorber, the content of the ultraviolet absorber in the pressure-sensitive adhesive layer controls the transmittance of light having a wavelength of 350 nm in the pressure-sensitive adhesive layer to obtain high ultraviolet rays. From the viewpoint of achieving absorbability, the pressure-sensitive adhesive or acrylic polymer in the pressure-sensitive adhesive layer is preferably 0.01 parts by weight or more, more preferably 0.05 parts by weight or more, and more preferably 0.05 parts by weight or more with respect to 100 parts by weight of the pressure-sensitive adhesive or acrylic polymer. It is 1 part by weight or more. In addition, the content of the ultraviolet absorber in the pressure-sensitive adhesive layer suppresses the occurrence of yellowing of the pressure-sensitive adhesive due to the addition of the UV-absorbing agent in the pressure-sensitive adhesive layer, and realizes excellent optical characteristics and high transparency. From the viewpoint, it is preferably 10 parts by weight or less, more preferably 9 parts by weight or less, and more preferably 8 parts by weight or less with respect to 100 parts by weight of the pressure-sensitive adhesive or acrylic polymer in the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layers 11 and 12 may each contain a light stabilizer. When the pressure-sensitive adhesive layers 11 and 12 each contain a light stabilizer, they preferably also contain an ultraviolet absorber. A light stabilizer is a chemical species capable of capturing radicals that can be generated by irradiation with light such as ultraviolet rays. Examples of the light stabilizer include a phenol-based light stabilizer, a phosphorus-based light stabilizer, a thioether-based light stabilizer, and an amine-based light stabilizer such as a hindered amine-based stabilizer. The pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 may contain one kind of light stabilizer, or may contain two or more kinds of light stabilizers.

Examples of the phenolic light stabilizer include 2,6-di-tert-butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-tert-butylphenol, 2,6-di-tert-butyl-. 4-Ethylphenol, butylated hydroxyanisol, n-octadecyl 3- (4-hydroxy-3,5-di-tert-butylphenyl) propionate, distearyl (4-hydroxy-3-methyl-5-tert-butyl) Benzylmalonate, tocopherol, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-methylenebis (2) , 6-Di-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol), 4,4'-thiobis (6-tert-butyl-m-cresol), styrenated phenol, N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxyhydrocinnamide, bis (3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid ethyl ester) calcium, 1 , 1,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-butyl- 4-Hydroxybenzyl) benzene, tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxymethyl] methane, 1,6-hexanediol-bis [3- (3,5-di) -tert-Butyl-4-hydroxyphenyl) propionate], 2,2'-methylenebis (4-methyl-6-cyclohexylphenol), 2,2'-methylenebis [6- (1-methylcyclohexyl) -p-cresol] 1,3,5-Tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxy) Benzyl) isocyanuric acid, triethylene glycol-bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate], 2,2'-oxamidbis [ethyl 3- (3,5-di-tert) -Butyl-4-hydroxyphenyl) propionate], 6- (4-hydroxy-3,5-di-tert-butylanilino) -2, 4-Dioctylthio-1,3,5-triazine, bis [2-tert-butyl-4-methyl-6- (2-hydroxy-3-tert-butyl-5-methylbenzyl) phenyl] terephthalate, 3,9 -Bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5. 5] Undecane, and 3,9-bis {2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8, 10-Tetraoxaspiro [5.5] undecane can be mentioned.

Examples of phosphorus-based photostabilizers include trisnonylphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, and tris [2-tert-butyl-4- (3-tert-butyl-4). -Hydroxy-5-methylphenylthio) -5-methylphenyl] phosphite, tridecylphosphite, octyldiphenylphosphite, di (decyl) monophenylphosphite, di (tridecyl) pentaerythritol diphosphite, distearylpenta Ellisritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis (2,6-di-tert-butyl-4-methyl) Phenyl) pentaerythritol diphosphite, bis (2,4,6-tri-tert-butylphenyl) pentaerythritol diphosphite, tetra (tridecyl) isopropyridene diphenol diphosphite, tetra (tridecyl) -4,4' -n-butylidenebis (2-tert-butyl-5-methylphenol) diphosphite, hexa (tridecyl) -1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butanetriphosphite, Tetrakiss (2,4-di-tert-butylphenyl) biphenylenediphosphonite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and tris (2-[(2,4,4) , 8,10-Tetrakiss-tert-butyldibenzo [d, f] [1,3,2] dioxaphosfepine-6-yl) oxy] ethyl) amine.

Examples of the thioether-based light stabilizer include dialkylthiodipropionate compounds such as dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiodipropionate, and tetrakis [methylene (3-dodecylthio) propionate]. Examples thereof include β-alkyl mercaptopropionic acid ester compounds of polyols such as methane.

Examples of the amine-based light stabilizer include a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (trade name "TINUVIN 622", manufactured by BASF). The polymer and N, N', N'', N'''-tetrax- (4,6-bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidine-4-yl)) ) Amino) -triazine-2-yl) -4,7-diazadecan-1,10-diamine and one-to-one reaction product (trade name "TINUVIN 119", manufactured by BASF), poly [{6- (1) , 1,3,3-Tetramethylbutyl) Amino-1,3,5-triazine-2-4-diyl} {2,2,6,6-tetramethyl-4-piperidyl} imino] Hexamethylene {(2) , 2,6,6-tetramethyl-4-piperidyl) imino}) (trade name "TINUVIN 944", manufactured by BASF), bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (commodity) Name "TINUVIN 770", manufactured by BASF), bis (2,2,6,6-tetramethyl-1- (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethylhydroperoxide and octane Reaction product with (trade name "TINUVIN 123", manufactured by BASF), bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) ) -4-Hydroxyphenyl] methyl] butylmalonate (trade name "TINUVIN 144", manufactured by BASF), cyclohexane and N-butyl peroxide 2,2,6,6-tetramethyl-4-piperidinamine-2, Reaction product of 4,6-trichloro-1,3,5-triazine and 2-aminoethanol (trade name "TINUVIN 152", manufactured by BASF), Bis (1,2,2,6, A mixture of 6-pentamethyl-4-piperidyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate (trade name "TINUVIN 292", manufactured by BASF), and 1,2,3. , 4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10- Tetraoxaspiro [5.5] Mixed esterified product with undecane (trade name "Adecastab LA-63P", AD Co., Ltd. (Made by EKA). As the amine-based stabilizer, a hindered amine-based stabilizer is particularly preferable.

When the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 contains a light stabilizer, the content of the light stabilizer in the pressure-sensitive adhesive layer is a pressure-sensitive adhesive from the viewpoint of realizing sufficient light resistance in the pressure-sensitive adhesive layer. It is preferably 0.1 parts by weight or more, and more preferably 0.2 parts by weight or more with respect to 100 parts by weight of the pressure-sensitive adhesive or acrylic polymer in the layer. Further, the content of the light stabilizer in the pressure-sensitive adhesive layer is the pressure-sensitive adhesive or acrylic type in the pressure-sensitive adhesive layer from the viewpoint of suppressing coloring due to the light stabilizer in the pressure-sensitive adhesive layer and realizing high transparency. It is preferably 5 parts by weight or less, more preferably 3 parts by weight or less with respect to 100 parts by weight of the polymer.

The pressure-sensitive adhesive or acrylic polymer contained in the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 may be cross-linked with a cross-linking agent other than the above-mentioned copolymerizable cross-linking agent. It is possible to adjust the gel fraction of the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 by utilizing the cross-linking of the pressure-sensitive adhesive or the acrylic polymer with the cross-linking agent. Examples of such cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, melamine-based cross-linking agents, peroxide-based cross-linking agents, urea-based cross-linking agents, metal alkoxide-based cross-linking agents, metal chelate-based cross-linking agents, and metals. Examples thereof include salt-based cross-linking agents, carbodiimide-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, and amine-based cross-linking agents. The pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 may contain one kind of the cross-linking agent, or may contain two or more kinds of the cross-linking agent. In this embodiment, an isocyanate-based cross-linking agent and / or an epoxy-based cross-linking agent is preferably used.

Examples of the isocyanate-based cross-linking agent include lower aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. Examples of the lower aliphatic polyisocyanates include 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate. Examples of alicyclic polyisocyanates include cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylene diisocyanate. Examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate. Examples of the isocyanate-based cross-linking agent include trimethylolpropane / tolylene diisocyanate adduct (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd.) and trimethylolpropane / hexamethylene diisocyanate adduct (trade name "Coronate HL"). , Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane / xylylene diisocyanate adduct (trade name "Takenate D-110N", manufactured by Mitsui Chemicals Co., Ltd.) and the like.

Examples of the epoxy-based cross-linking agent (polyfunctional epoxy compound) include N, N, N', N'-tetraglycidyl-m-xylene diamine, diglycidyl aniline, and 1,3-bis (N, N-diglycidyl amino). Methyl) 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, Gglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylpropan polyglycidyl ether, adipate diglycidyl ester, o-phthalate diglycidyl ester, triglycidyl-tris (2- Hydroxyethyl) isocyanurate, resorcin diglycidyl ether, and bisphenol-S-diglycidyl ether. Further, as the epoxy-based cross-linking agent, an epoxy-based resin having two or more epoxy groups can also be mentioned. In addition, examples of the epoxy-based cross-linking agent include commercially available products such as the trade name "Tetrad C" (manufactured by Mitsubishi Gas Chemical Company, Inc.).

When the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 contains the above-mentioned cross-linking agent for cross-linking between acrylic polymers, the content of the cross-linking agent in the pressure-sensitive adhesive layer is adjusted in the pressure-sensitive adhesive layer. From the viewpoint of achieving sufficient adhesive reliability with respect to the body, preferably 0.001 part by weight or more, more preferably 0.01 part by weight or more with respect to 100 parts by weight of the pressure-sensitive adhesive or acrylic polymer in the pressure-sensitive adhesive layer. Is. Further, the content of the cross-linking agent in the pressure-sensitive adhesive layer is the pressure-sensitive adhesive or acrylic polymer 100 in the pressure-sensitive adhesive layer from the viewpoint of exhibiting appropriate flexibility in the pressure-sensitive adhesive layer and realizing good pressure-sensitive adhesive strength. It is preferably 10 parts by weight or less, more preferably 5 parts by weight or less with respect to parts by weight.

The pressure-sensitive adhesive layers 11 and 12, respectively, are a cross-linking accelerator, an antistatic resin, an anti-aging agent, a filler, a colorant such as a pigment or a dye, an antioxidant, a chain transfer agent, a plasticizer, and a softening agent, respectively. Additives such as agents, surfactants, and antistatic agents may be further included. Examples of the tackifier resin include rosin derivatives, polyterpene resins, petroleum resins, and oil-soluble phenols.

The thickness of the pressure-sensitive adhesive layer 11 is preferably 5 μm or more, more preferably 10 μm or more, and more preferably 15 μm from the viewpoint of realizing sufficient adhesive force on the adherend on the pressure-sensitive adhesive layer 11 side in the pressure-sensitive adhesive tape X. That is all. From the viewpoint of ease of formation, the thickness of the pressure-sensitive adhesive layer 11 is preferably 1000 μm or less, more preferably 900 μm or less, and more preferably 800 μm or less.

The thickness of the pressure-sensitive adhesive layer 12 is preferably 5 μm or more, more preferably 10 μm or more, and more preferably 15 μm from the viewpoint of realizing sufficient adhesive force on the adherend on the pressure-sensitive adhesive layer 12 side in the pressure-sensitive adhesive tape X. That is all. From the viewpoint of ease of formation, the thickness of the pressure-sensitive adhesive layer 11 is preferably 1000 μm or less, more preferably 900 μm or less, and more preferably 800 μm or less.

In the adhesive tape X having a laminated structure including the base material 10 and the pressure-sensitive adhesive layers 11 and 12 as described above, the Elmendorf tear strength in the base material width direction is 0.5 N or less, and the Elmendorf tear in the base material machine direction. The strength is 1N or more. The Elmendorf tear strength of the adhesive tape X in the width direction of the base material is preferably 0.45 N or less, more preferably 0.4 N or less, and more preferably 0.3 N or less. The Elmendorf tear strength of the adhesive tape X in the mechanical direction of the base material is preferably 1.1 N or more, more preferably 1.3 N or more, and more preferably 1.5 N or more. The Elmendorf tear strength shall be a value measured in accordance with JIS K 7128-2.

The thickness direction of the optical adhesive tape X is preferably 3% or less, more preferably 2.5% or less, more preferably 2% or less, more preferably 1.5% or less, and more preferably. It is 1% or less. The haze shall be a value measured in accordance with JIS K 7136. For the adhesive tape X, the total light transmittance in the visible light wavelength region is, for example, 85% or more. The total light transmittance shall be a value measured in accordance with JIS K 7361-1.

The adhesive tape X may be provided with a release liner (separator) so as to cover the adhesive surface 11a of the adhesive layer 11. The adhesive tape X may be provided with a release liner (separator) so as to cover the adhesive surface 12a of the adhesive layer 12. The release liner is an element for protecting the adhesive layers 11 and 12 of the adhesive tape X from being exposed, and is peeled off from the adhesive tape X when the adhesive tape X is attached to the adherend. Examples of the peeling liner include a base material having a peeling treatment layer, a low adhesive base material made of a fluoropolymer, and a low adhesive base material made of a non-polar polymer. The surface of the release liner may be subjected to a mold release treatment, an antifouling treatment, or an antistatic treatment. The thickness of the release liner is, for example, 5 to 200 μm. Specifically, the adhesive tape X may take the form of a sheet with a release liner covering the adhesive surfaces 11a and 12a of the adhesive layers 11 and 12, and the adhesive tape X and the release liner are alternately arranged. As described above, it may be wound in a roll shape with a release liner.

The pressure-sensitive adhesive tape X having the above structure can be produced, for example, by forming the pressure-sensitive adhesive layers 11 and 12, respectively, and then bonding the pressure-sensitive adhesive layers 11 and 12 to the base material 10, respectively. For the pressure-sensitive adhesive layer 11, for example, a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer 11 is applied onto a predetermined release liner to form a pressure-sensitive adhesive composition layer, and a further release liner is further applied on the pressure-sensitive adhesive composition layer. Can be formed by laminating and curing the pressure-sensitive adhesive composition between the release liners. On the other hand, the pressure-sensitive adhesive layer 12 is formed by, for example, applying a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer 12 on a predetermined release liner to form a pressure-sensitive adhesive composition layer, and further on the pressure-sensitive adhesive composition layer. It can be formed by laminating release liners and curing the pressure-sensitive adhesive composition between the release liners.

As the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer 12, for example, a pressure-sensitive adhesive composition in which the polymerization reaction proceeds by irradiation with active energy rays and can be cured. Used. That is, the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive layer 12 is, for example, a cured product of an active energy ray-curable pressure-sensitive adhesive composition. The active energy ray-curable pressure-sensitive adhesive composition for forming an acrylic pressure-sensitive pressure-sensitive adhesive layer contains at least a monomer, an oligomer, and a photopolymerization initiator for forming an acrylic-based polymer. The monomers and oligomers in the composition can be provided as so-called partial polymers of a monomer mixture having a predetermined composition for forming an acrylic polymer. In addition, the pressure-sensitive adhesive composition may contain other components that are adopted as necessary as components of the pressure-sensitive adhesive layer to be formed. Examples of the active energy rays irradiated to the active energy ray-curable pressure-sensitive adhesive composition for curing the pressure-sensitive adhesive layer include ultraviolet rays, α rays, β rays, γ rays, neutron rays, and electron rays. Ultraviolet rays are preferably adopted. In the active energy ray-curable pressure-sensitive adhesive composition for forming an acrylic pressure-sensitive adhesive layer, which has been irradiated with active energy rays, an initiation reaction occurs after activation of a photopolymerization initiator, and the acrylic polymer is formed. The polymerization reaction proceeds. When active energy ray irradiation such as ultraviolet irradiation is adopted as a curing method of the curable pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition is appropriately cured even when the coating film is relatively thick. It is easy to obtain the adhesive layer. Therefore, the configuration in which the pressure-sensitive adhesive layer 11 is a cured product of the active energy ray-curable pressure-sensitive adhesive composition is suitable for realizing a pressure-sensitive adhesive layer 11 that is sufficiently cured even if it is relatively thick. The configuration in which the pressure-sensitive adhesive layer 12 is a cured product of the active energy ray-curable pressure-sensitive adhesive composition is suitable for realizing a pressure-sensitive adhesive layer 12 that is sufficiently cured even if it is relatively thick.

Examples of the above-mentioned photopolymerization initiator include a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, and a photoactive oxime-based photoinitiator. Examples thereof include a polymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. Examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-diphenylethane-1-one. Can be mentioned. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone (α-hydroxycyclohexylphenylketone), and 4-phenoxydichloroacetophenone. , And 4- (t-butyl) dichloroacetophenone. Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one. .. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalene sulfonyl chloride. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime. Examples of the benzoin-based photopolymerization initiator include benzoin. Examples of the benzyl-based photopolymerization initiator include benzyl. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of the ketal-based photopolymerization initiator include benzyldimethyl ketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. The content of the photopolymerization initiator in the active energy ray-curable pressure-sensitive adhesive composition is, for example, 0.01 to 3% by weight.

The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer 11 and / or the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer 12 is a solvent-type pressure-sensitive adhesive that already contains an acrylic polymer as a pressure-sensitive adhesive and can be cured by, for example, heat-drying. A composition or an emulsion type pressure-sensitive adhesive composition may be used. The composition may contain other components that are optionally adopted as components of the pressure-sensitive adhesive layer to be formed. The acrylic polymer in the pressure-sensitive adhesive composition can be obtained by polymerizing a raw material monomer component for forming an acrylic polymer. Examples of the polymerization method include solution polymerization, emulsion polymerization, and bulk polymerization. When performing solution polymerization, for example, aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, esters, and ketones can be used as the solvent. Examples of the solvent for aromatic hydrocarbons include toluene and benzene. Solvents for aliphatic hydrocarbons include, for example, n-hexane and n-heptane. Examples of the solvent for alicyclic hydrocarbons include cyclohexane and methylcyclohexane. Examples of the solvent for the esters include ethyl acetate and n-butyl acetate. Examples of the solvent for the ketones include methyl ethyl ketone and methyl isobutyl ketone. In solution polymerization, one kind of solvent may be used, or two or more kinds of solvents may be used.

When polymerizing the raw material monomer component to obtain an acrylic polymer, a polymerization initiator can be used. Depending on the type of polymerization reaction, for example, a photopolymerization initiator or a thermal polymerization initiator can be used. At the time of polymerization, one kind of polymerization initiator may be used, or two or more kinds of polymerization initiators may be used.

Examples of the photopolymerization initiator include the above-mentioned benzoin ether-based photopolymerization initiator, acetphenone-based photopolymerization initiator, α-ketol-based photopolymerization initiator, aromatic sulfonyl chloride-based photopolymerization initiator, and photoactive oxime-based photoinitiator. Examples thereof include a polymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. The amount of the photopolymerization initiator used is, for example, 0.01 to 3 parts by weight with respect to the total amount of the monomer components (100 parts by weight).

Examples of the thermal polymerization initiator include an azo-based polymerization initiator, a peroxide-based polymerization initiator, and a redox-based polymerization initiator. Examples of the azo-based polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, and 2,2'-azobis (2-methylpropionate) dimethyl. , And 4,4'-azobis-4-cyanovaleric acid. Examples of the peroxide-based polymerization initiator include benzoyl peroxide and tert-butyl permalate. The amount of the thermal polymerization initiator used is, for example, 0.05 to 0.3 parts by weight with respect to the total amount of the monomer components (100 parts by weight).

In the polymerization for obtaining the acrylic polymer, a chain transfer agent can be used to adjust the molecular weight of the acrylic polymer. Examples of the chain transfer agent include α-thioglycerol, 2-mercaptoethanol, 2,3-dimercapto-1-propanol, octyl mercaptan, t-nonyl mercaptan, dodecyl mercaptan (lauryl mercaptan), t-dodecyl mercaptan, and glycidyl mercaptan. , Thioglycolic acid, methyl thioglycolate, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, thio Examples include decyl glycolate and dodecyl thioglycolate. As the chain transfer agent, one type of chain transfer agent may be used, or two or more types of chain transfer agents may be used. In this embodiment, α-thioglycerol is preferably used as the chain transfer agent. The amount of the chain transfer agent used is, for example, 0.01 to 0.5 parts by weight with respect to the total amount of the monomer components (100 parts by weight) for obtaining the acrylic polymer.

When the pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer, such as an active energy ray-curable pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, and an emulsion-type pressure-sensitive adhesive composition, contains the above-mentioned acrylic oligomer, the oligomer is concerned. Can be obtained by polymerizing a raw material monomer component having a predetermined composition. Examples of the polymerization method include solution polymerization, emulsion polymerization, and bulk polymerization. Examples of the solvent for solution polymerization include those described above as a solvent that can be used for solution polymerization for obtaining an acrylic polymer. In the solution polymerization, one kind of solvent may be used, or two or more kinds of solvents may be used. Further, when polymerizing the raw material monomer component in order to obtain the above-mentioned oligomer, a polymerization initiator can be used. Examples of the polymerization initiator include the above-mentioned photopolymerization initiator and thermal polymerization initiator as the polymerization initiator that can be used for polymerization for obtaining an acrylic polymer. At the time of polymerization, one kind of polymerization initiator may be used, or two or more kinds of polymerization initiators may be used.

For example, the base material 10 of the adhesive tape X produced as described above is a polyester-based base material as described above. Such a configuration is suitable for enjoying various properties that are easily exhibited in the polyester-based base material, such as heat resistance, transparency, and dimensional stability, in the double-sided adhesive tape base material and thus in the adhesive tape X.

Further, the base material 10 of the adhesive tape X is a uniaxially stretched polyester-based base material in the width direction as described above. As described above, the thickness of the base material 10 is 75 μm or more, preferably 80 μm or more. As described above, the thickness of the base material 10 is, for example, 150 μm or less, preferably 125 μm or less. The tear strength such as the Elmendorf tear strength in the double-sided adhesive tape is strongly controlled by the mechanical properties of the base material. In these configurations, the Elmendorf tear strength in the width direction of the base material is 0.5 N or less in the adhesive tape X. It is suitable for realizing the above-mentioned configuration in which the Ermendorf tear strength in the direction of the base material machine is 1 N or more.

In addition, the Elmendorf tear strength of the adhesive tape X in the width direction of the base material is 0.5 N or less, preferably 0.45 N or less, more preferably 0.4 N or less, and more preferably 0.3 N, as described above. It is as follows. At the same time, the Elmendorf tear strength of the adhesive tape X in the mechanical direction of the base material is 1N or more, preferably 1.1N or more, more preferably 1.3N or more, and more preferably 1.5N or more, as described above. is there. These configurations are suitable for realizing good hand-cutting property in the substrate width direction in which the Elmendorf tear strength is 0.5 N or less, which is relatively significantly low, in the adhesive tape X. The configuration in which the Elmendorf tear strength is twice or more in the base material machine direction in the base material width direction is suitable for enhancing the directivity of the adhesive tape X with respect to tearing in the base material width direction. Therefore, in this configuration, when the adhesive tape X is attached to the adherend, the adhesive tape X is not torn from the adherend by applying a peeling force in the direction of the base material machine of the adhesive tape X. It is suitable for proper peeling. Specifically, in the work of attaching the adhesive tape X to the adherend, then peeling it off and then reattaching it (rework work), the adhesive tape X is adhered by applying a peeling force in the direction of the base material machine. It is suitable for appropriately peeling the adhesive tape X from the body without tearing it. The optical double-sided adhesive tape, which is easily torn not only in the width direction of the base material but also in the machine direction of the base material, tends to be easily torn at the time of peeling in the rework work, and it tends to be difficult to properly peel off. The torn double-sided optical adhesive tape cannot be used for re-bonding. On the other hand, the adhesive tape X has a base material mechanical direction Elmendorf tear strength that is sufficiently larger than the base material width direction Elmendorf tear strength suitable for realizing good hand-cutting property in the base material width direction. It is suitable for appropriately peeling without tearing by applying a peeling force in the direction of the base material machine during the rework work.

As described above, the adhesive tape X is suitable for achieving both good hand-cutting property and high reworkability while having a polyester-based base material.

As described above, the in-plane phase difference of the base material 10 of the adhesive tape X is preferably 1500 nm or more, more preferably 3000 nm or more, and more preferably 6000 nm or more. In such a configuration, when the adhesive tape X is provided so as to fill the space between the transparent cover forming the front surface of the display screen and the liquid crystal panel in the liquid crystal display device, for example, polarized light such as polarized sunglasses is provided. It is suitable for suppressing the occurrence of the so-called blackout phenomenon when the display screen is visually recognized through the functional lens. Further, when the in-plane phase difference of the base material 10 is larger, the adhesive tape X is provided so as to fill the space between the transparent cover and the liquid crystal panel in the liquid crystal display device, for example, with a polarizing function such as polarized sunglasses. The so-called rainbow unevenness phenomenon tends to be suppressed when the display screen is visually recognized through the lens.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples.

[Production example of acrylic oligomer]
In the reaction vessel, 60 parts by weight of dicyclopentanyl methacrylate (DCPMA), 40 parts by weight of methyl methacrylate (MMA), 3.5 parts by weight of α-thioglycerol as a chain transfer agent, and as a polymerization solvent. The mixture containing 100 parts by weight of toluene was stirred at 70 ° C. for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was added to the mixture in the reaction vessel to prepare a reaction solution, and the reaction was carried out at 70 ° C. for 2 hours. Subsequently, the reaction was carried out at 80 ° C. for 2 hours. Then, the reaction solution in the reaction vessel was placed in a temperature atmosphere of 130 ° C., and toluene, the chain transfer agent, and the unreacted monomer were dried and removed from the reaction solution. As a result, a solid acrylic oligomer was obtained. The weight average molecular weight of the acrylic oligomer (Mw) of, was 5.1 × 10 ^3.

[Preparation Example of Acrylic Adhesive Composition C1]
The first in a monomer mixture containing 78 parts by weight of 2-ethylhexyl acrylate (2EHA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 4 parts by weight of 2-hydroxyethyl acrylate (HEA). 0.035 parts by weight of the photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF) and 0.035 parts by weight of the second photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF) were added. After that, the mixture was irradiated with ultraviolet rays using an ultraviolet irradiation device until the viscosity of the mixture became about 20 Pa · s while measuring the viscosity using a viscosity measuring device. In the viscosity measurement, the rotor rotation speed of the apparatus was 10 rpm, and the measurement temperature was 30 ° C. As a result, a prepolymer composition (containing a monomer component that has not undergone a polymerization reaction), which is a partial polymer in which a part of the monomer components in the mixture is polymerized, was obtained. Then, 100 parts by weight of this prepolymer composition, 11.8 parts by weight of the above-mentioned acrylic oligomer, 17.6 parts by weight of 2-hydroxyethyl acrylate (HEA), and 1,6-hexanediol diacrylate (HDDA). ) 0.294 parts by weight and 0.353 parts by weight of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Industry Co., Ltd.) are mixed to form an acrylic pressure-sensitive adhesive composition (acrylic pressure-sensitive adhesive composition). The thing C1) was obtained.

[Preparation Example of Acrylic Adhesive Composition C2]
In a flask (reaction vessel) equipped with a recirculation cooler, a nitrogen gas introduction tube, a stirrer, and a thermometer, 100 parts by weight of n-butyl acrylate (BA), 5 parts by weight of acrylic acid (AA), and acrylic acid. 0.075 parts by weight of 2-hydroxyethyl (HEA), 0.2 parts by weight of benzoyl peroxide (trade name "Niper BW", manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator, and ethyl acetate 205 as a polymerization solvent. The mixture containing parts by weight was reacted at 63 ° C. for 4 hours with gentle stirring in a nitrogen atmosphere. As a result, a solution containing an acrylic polymer (acrylic polymer solution) at a concentration of about 35% by weight was obtained. Then, after diluting the acrylic polymer solution with ethyl acetate so that the acrylic polymer concentration becomes 29% by weight, 0.6 parts by weight of trimethylol is added to the acrylic polymer solution with respect to 100 parts by weight of the acrylic polymer. With propane / tolylene diisocyanate adduct (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd.) and 0.075 parts by weight of silane coupling agent (trade name "KBM-403", manufactured by Shinetsu Chemical Industry Co., Ltd.) Was mixed at 25 ° C. for about 1 minute to obtain a solvent-type acrylic pressure-sensitive adhesive composition (acrylic pressure-sensitive adhesive composition C2).

[Example 1]
<Formation of the first adhesive layer>
The above acrylic pressure-sensitive adhesive composition C1 was applied onto a polyethylene terephthalate (PET) -based release liner (thickness 125 μm, manufactured by Nitto Denko KK) to form a pressure-sensitive adhesive composition layer. Next, a PET-based release liner (thickness 125 μm, manufactured by Nitto Denko KK) was further laminated on the pressure-sensitive adhesive composition layer, and the pressure-sensitive adhesive composition layer was coated to block oxygen. In this way, a laminated body (laminated body L1') having a laminated structure of [release liner / adhesive composition layer / release liner] was obtained. Next, the laminated body L1'was irradiated with ultraviolet rays having ^{an illuminance of 3 mW / cm 2} for 300 seconds from the side of one of the release liners using a black light (manufactured by Toshiba Corporation). As a result, the pressure-sensitive adhesive composition layer of the laminate L1'is cured to form a pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer), and the laminated structure of [release liner / pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) / release liner] is formed. A laminated body (laminated body L1) having a structure was obtained. The thickness of the first pressure-sensitive adhesive layer in the laminated body L1 is 100 μm.

<Formation of second adhesive layer>
The above acrylic pressure-sensitive adhesive composition C2 was applied onto a PET-based release liner (thickness 125 μm, manufactured by Nitto Denko KK) to form a pressure-sensitive adhesive composition layer. Next, a PET-based release liner (thickness 125 μm, manufactured by Nitto Denko KK) was further laminated on the pressure-sensitive adhesive composition layer, and the pressure-sensitive adhesive composition layer was coated to block oxygen. In this way, a laminated body (laminated body L2') having a laminated structure of [release liner / adhesive composition layer / release liner] was obtained. Next, the laminated body L2'was irradiated with ultraviolet rays having ^{an illuminance of 3 mW / cm 2} for 300 seconds from the side of one of the release liners using a black light (manufactured by Toshiba Corporation). As a result, the pressure-sensitive adhesive composition layer of the laminated body L2'is cured to form a pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer), and the laminated structure of [peeling liner / pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer) / peeling liner] is formed. A laminated body (laminated body L2) having a structure was obtained. The thickness of the second pressure-sensitive adhesive layer in the laminated body L2 is 500 μm.

<Making double-sided adhesive tape for optics>
_{A film (film F 1} ) obtained by applying corona treatment to both sides of an 80 μm-thick polyethylene terephthalate film (trade name “Cosmo Shine SRF”, in-plane phase difference 8400, manufactured by Toyobo Co., Ltd.) was prepared and laminated as described above. After peeling one of the peeling liners from the body L1 (peeling liner / first pressure-sensitive adhesive layer / peeling liner), the first pressure-sensitive adhesive layer with one-sided peeling liner is formed through the surface of the first pressure-sensitive adhesive layer exposed by this peeling. bonded to one surface of the film F _1. As a result, a laminated body having a laminated structure of [release liner / first pressure-sensitive adhesive layer / film F _{1] was obtained.} Next, after peeling one peeling liner from the above-mentioned laminate L2 (peeling liner / second pressure-sensitive adhesive layer / peeling liner), a one-sided peeling liner is attached via the surface of the second pressure-sensitive adhesive layer exposed by this peeling. The second pressure-sensitive adhesive layer was bonded to the other surface of the _{film F 1.} As described above, the laminated structure of [release liner / first adhesive layer (thickness 100 μm) / base film F ₁ (thickness 80 μm) / second adhesive layer (thickness 500 μm) / release liner] A double-sided adhesive tape for optics was produced. The thickness of the optical double-sided adhesive tape of Example 1 excluding the thickness of the release liner is 680 μm.

[Example 2]
80 μm thick polyethylene terephthalate film (“Cosmo Shine SRF” easy-adhesion-treated layer replaced with hard-coating easy-adhesion-treated film, in-plane phase difference 8400, Toyo Boseki Co., Ltd. The optical double-sided adhesive tape of Example 2 was applied in the same manner as in Example 1 except that _{a film (film F 2} ) obtained by corona-treating both sides of (manufactured by the company) was used instead of film F _1. Made. The thickness of the optical double-sided adhesive tape of Example 2 excluding the thickness of the release liner is 680 μm.

[Example 3]
The optical double-sided adhesive tape of Example 3 was produced in the same manner as in Example 1 except that the thickness of the second pressure-sensitive adhesive layer was set to 100 μm instead of 500 μm. The thickness of the optical double-sided adhesive tape of Example 3 excluding the thickness of the release liner is 280 μm.

[Example 4]
The acrylic pressure-sensitive adhesive composition C2 is _{applied to one side of the film F 1} and then heated at 130 ° C. for 60 seconds to dry and cure, and a pressure-sensitive adhesive layer (first pressure-sensitive adhesive) having a thickness of 12 μm is placed on _{the film F 1.} Layer) was formed. Next, a PET-based release liner (thickness 125 μm, manufactured by Nitto Denko KK) was attached to the surface of the pressure-sensitive adhesive layer. As a result, a laminated body (laminated body L3) having a laminated structure of [release liner / pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) / release liner] was obtained. On the other hand, the above acrylic pressure-sensitive adhesive composition C2 is applied to one side of a PET-based release liner (thickness 125 μm, manufactured by Nitto Denko KK) and then heated at 130 ° C. for 60 seconds to dry and cure, and the release liner is dried and cured. A pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer) having a thickness of 12 μm was formed on the top. Then, the above-mentioned laminate L3 was _{bonded to the surface of the pressure-sensitive adhesive layer via the film F 1} side surface. As described above, the laminated structure of [release liner / first adhesive layer (thickness 12 μm) / base film F ₁ (thickness 80 μm) / second adhesive layer (thickness 12 μm) / release liner] The optical double-sided adhesive tape of Example 4 having the above was prepared. The thickness of the optical double-sided adhesive tape of Example 4 excluding the thickness of the release liner is 104 μm.

[Comparative Example 1]
_{A film (film F 3} ) obtained by applying corona treatment to both sides of a polyethylene terephthalate film (trade name "XD500P", in-plane phase difference 3000, manufactured by Toray Co., Ltd.) having a thickness of 75 μm as a base material for an optical double-sided adhesive tape. ) Was used instead of the film F ₁ , and the thickness of the second pressure-sensitive adhesive layer was changed to 100 μm instead of 500 μm. A tape was made. The thickness of the optical double-sided adhesive tape of Comparative Example 1 excluding the thickness of the release liner is 275 μm.

[Comparative Example 2]
The optical double-sided adhesive tape of Comparative Example 2 was produced in the same manner as in Example 4 except that the film F _{3 was used instead of the film F 1 as the base material of the optical double-sided adhesive tape.} The thickness of the optical double-sided adhesive tape of Comparative Example 2 excluding the thickness of the release liner is 104 μm.

<Elmendorf tear strength>
For each sample piece (60 mm × 75 mm) cut out from the optical double-sided adhesive tapes of Examples and Comparative Examples, an Elmendorf tear strength measuring device (trade name “Elmendorf tear degree tester”, manufactured by Tester Sangyo Co., Ltd.) was used. The Elmendorf tear strength (N) in the width direction (TD) of the tape base material and the Elmendorf tear strength (N) in the mechanical direction (MD) of the tape base material were measured. This measurement was performed in accordance with JIS K 7128-2. The sample piece attached to the measurement is provided with a notch having a length of 20 mm extending from the end thereof in the measurement direction (TD or MD) in advance. In this measurement, the resistance to the tear load applied to the sample piece by the device so that the notch is further extended is measured. The maximum measurement value of the above device used for this measurement is 1N. The results of this measurement are listed in Table 1.

<Hand cutting>
For each of the optical double-sided adhesive tapes of Examples and Comparative Examples, the hand-cutting property in the width direction of the base material was examined. Specifically, an attempt was made to manually tear the optical double-sided adhesive tape from which both release liners were peeled off in the width direction of the base material. In the manual inspection, the case where the tear was easily torn was evaluated as good (○), and the case where the tear was not possible was evaluated as poor (×). The results are listed in Table 1.

<Haze>
For each optical double-sided adhesive tape of Examples and Comparative Examples, a haze meter HM-150 type (manufactured by Murakami Color Technology Research Institute Co., Ltd.) was used, and haze (%) was performed in accordance with the method specified in JIS K 7136. Was measured. In this measurement, both sides for optics are in a state where both release liners are peeled off and attached to a slide glass (trade name "Slide glass S1112", thickness 1.0 to 1.2 mm, manufactured by Matsunami Glass Industry Co., Ltd.). I went with the adhesive tape. The results are listed in Table 1.

[Evaluation]
In all of the optical double-sided adhesive tapes of Examples 1 to 4 having the configuration of the present invention, good hand-cutting property was realized. On the other hand, in the optical double-sided adhesive tapes of Comparative Examples 1 and 2, none of them could be torn by hand in the width direction of the base material, and good hand-cutting property could not be realized.

X Adhesive tape (double-sided adhesive tape for optics)
10 Base material 11 Adhesive layer (first adhesive layer)
12 Adhesive layer (second adhesive layer)

Claims (3)

It has a laminated structure including a first pressure-sensitive adhesive layer, a second pressure-sensitive adhesive layer, and a transparent base material between the first and second pressure-sensitive adhesive layers.
The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are provided on the surface of the transparent base material.
The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer contain an acrylic pressure-sensitive adhesive.
The acrylic pressure-sensitive adhesive contains an acrylic polymer and contains
The acrylic polymer contains a monomer unit derived from a hydroxyl group-containing (meth) acrylic acid ester, and contains a monomer unit.
The transparent base material is a uniaxially stretched polyester-based base material in the width direction of the base material and has a thickness of 75 μm or more.
An optical double-sided adhesive tape having an Elmendorf tear strength of 0.5 N or less in the substrate width direction and an Ermendorf tear strength of 1 N or more in the substrate machine direction. The double-sided optical adhesive tape according to claim 1, wherein the thickness of the first pressure-sensitive adhesive layer is 5 μm or more, and the thickness of the second pressure-sensitive adhesive layer is 5 μm or more. The double-sided adhesive tape for optics according to claim 1 or 2, wherein the haze is 3% or less.

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