JPWO2014162968A1 - Adhesive composition and optical adhesive tape - Google Patents

Abstract

Provided is a pressure-sensitive adhesive composition capable of achieving both a low dielectric constant and a high adhesive strength at a high level and improving impact resistance. The pressure-sensitive adhesive composition according to the present invention includes a nitrogen-containing cyclic compound having a nitrogen atom and a cyclic skeleton, a (meth) acrylate compound having a branched alkyl group having 10 to 20 carbon atoms, and radical polymerizable unsaturated A copolymer obtained by copolymerizing an olefin compound having a double bond is included.

Description

  The present invention relates to a pressure-sensitive adhesive composition having a low dielectric constant and having high adhesive strength and high impact resistance. The present invention also relates to an optical pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition.

  In recent years, the use of electronic devices equipped with touch panels has increased. For example, touch panels are used in electronic devices such as mobile phones, smartphones, car navigation systems, and personal computers. Among touch panels, capacitive touch panels are rapidly spreading due to their excellent functionality. Capacitive touch panels are widely used not only for smartphones but also for tablet personal computers.

  Generally, a capacitive touch panel is configured by laminating a cover panel, an optical pressure-sensitive adhesive layer, a conductive layer, and a base material such as a polyethylene terephthalate (PET) film or glass. The optical pressure-sensitive adhesive layer is required to be excellent in each performance of transparency and adhesion to the substrate. In recent years, the size of capacitive touch panels has been increasing. As the size of the touch panel increases, the optical adhesive layer is required to have a low dielectric constant in addition to the above-described performance.

  Moreover, since transparency becomes high, an acrylic adhesive is often used for the said optical adhesive layer.

  As an example of the acrylic pressure-sensitive adhesive used for obtaining the above optical pressure-sensitive adhesive layer, the following Patent Document 1 includes an alkyl (meth) acrylate having a branched alkyl group having 10 to 24 carbon atoms at the terminal of the ester group. A pressure-sensitive adhesive containing a (meth) acrylic polymer obtained by polymerizing a monomer component containing 19 to 99.5% by weight is disclosed. Patent Document 1 describes that the use of the above-mentioned pressure-sensitive adhesive can realize a pressure-sensitive adhesive layer having a low dielectric constant and satisfy the adhesive performance.

  In the following Patent Document 2, the cyclic structure-containing monomer is 25 to 99.5% by weight, and the branched structure-containing (meth) acrylic monomer having a branched alkyl group having 3 to 18 carbon atoms at the ester terminal is 0.5 to 70% by weight. A pressure-sensitive adhesive composition containing a (meth) acrylic polymer obtained by polymerizing the monomer component using a monomer component containing% is disclosed. Patent Document 2 describes that the use of the above-mentioned pressure-sensitive adhesive composition can realize a pressure-sensitive adhesive layer having an excellent low dielectric constant and satisfying adhesion performance and transparency.

  In Patent Document 3 below, acrylic acid alkyl ester having a linear or branched alkyl group having 6 to 10 carbon atoms, methacrylic acid having a linear or branched alkyl group having 1 to 10 carbon atoms Optical pressure-sensitive adhesive sheet (acrylic pressure-sensitive adhesive) comprising an acrylic polymer composed of one or more monomer components selected from the group consisting of alkyl esters, (meth) acrylic acid esters having alicyclic hydrocarbon groups, and nitrogen-containing monomers Layer). Patent Document 3 describes that the optical adhesive sheet has a low dielectric constant and does not become clouded by humidification.

JP 2012-246477 A WO2013 / 002184A1 JP 2012-173354 A

  In the pressure-sensitive adhesive layer using the pressure-sensitive adhesive described in Patent Document 1, it is described that the 90-degree peel adhesive strength to glass is 0.5 N / 20 mm or more. However, this level of adhesion is insufficient. Therefore, in patent document 1, both performance of low dielectric constant and high adhesive force with respect to a cover glass cannot be made compatible at a high level.

  Even in a pressure-sensitive adhesive layer using the pressure-sensitive adhesive composition described in Patent Document 2, it is difficult to achieve both a low dielectric constant and a high adhesive strength at a high level. For example, in the pressure-sensitive adhesive compositions of the examples described in Patent Document 2, although the dielectric constant can be reduced to some extent, the adhesive strength is not sufficiently increased.

  Even with the optical pressure-sensitive adhesive sheet described in Patent Document 3, it is difficult to achieve both a low dielectric constant and a high adhesive strength at a high level. For example, in the optical pressure-sensitive adhesive sheet described in the example of Patent Document 3, although the adhesive force is developed to some extent, the dielectric constant is not sufficiently lowered.

  In recent years, with the widespread use of touch panels, there has been a further demand for higher performance of touch panels. In an optical pressure-sensitive adhesive layer that is a constituent member of a touch panel, it is strongly demanded to achieve both a low dielectric constant and a high adhesive strength to a cover glass at a high level.

  However, in the conventional optical pressure-sensitive adhesive layer, when the composition of the pressure-sensitive adhesive is designed so that the dielectric constant is sufficiently low, it is difficult to sufficiently increase the adhesive force. Conversely, the adhesive force is sufficiently high. When the composition of the pressure-sensitive adhesive is designed to be, there is a problem that the dielectric constant is not sufficiently lowered.

  Further, the laminate using the conventional optical pressure-sensitive adhesive layer has a problem that the impact resistance is low and peeling easily occurs.

  An object of the present invention is to provide a pressure-sensitive adhesive composition capable of achieving both a low dielectric constant and high adhesive strength at a high level and improving impact resistance, and to provide the pressure-sensitive adhesive composition. It is to provide an optical adhesive tape used.

  According to a wide aspect of the present invention, a nitrogen-containing cyclic compound having a nitrogen atom and a cyclic skeleton, a (meth) acrylate compound having a branched alkyl group having 10 to 20 carbon atoms, and a radically polymerizable unsaturated dimer. There is provided a pressure-sensitive adhesive composition containing a copolymer obtained by copolymerizing an olefin compound having a heavy bond.

  In a specific aspect of the pressure-sensitive adhesive composition according to the present invention, the copolymer includes 100 parts by weight of the nitrogen-containing cyclic compound, 1 part by weight or more and 150 parts by weight or less of the (meth) acrylate compound, and the olefin. It is obtained by copolymerizing 16 parts by weight or more and 800 parts by weight or less of the compound.

  In a specific aspect of the pressure-sensitive adhesive composition according to the present invention, the nitrogen-containing cyclic compound is vinylpyrrolidone or acryloylmorpholine.

  The pressure-sensitive adhesive composition according to the present invention is suitably used for obtaining an optical pressure-sensitive adhesive tape.

  According to the wide aspect of this invention, the optical adhesive tape obtained using the adhesive composition mentioned above is provided.

  The pressure-sensitive adhesive composition according to the present invention includes a nitrogen-containing cyclic compound having a nitrogen atom and a cyclic skeleton, a (meth) acrylate compound having a branched alkyl group having 10 to 20 carbon atoms, and radical polymerizable unsaturated Since it contains a copolymer obtained by copolymerizing an olefin compound having a double bond, it is possible to achieve both a low dielectric constant and a high adhesive strength at a high level, and a high impact resistance. Can have.

  Details of the present invention will be described below.

(Adhesive composition)
The pressure-sensitive adhesive composition according to the present invention includes a copolymer obtained by copolymerizing a nitrogen-containing cyclic compound, a (meth) acrylate compound, and an olefin compound. The nitrogen-containing cyclic compound has a nitrogen atom and has a cyclic skeleton. The (meth) acrylate compound has a branched alkyl group (branched alkyl group), and the branched alkyl group has 10 to 20 carbon atoms. The olefin compound has a radical polymerizable unsaturated double bond. In the pressure-sensitive adhesive composition according to the present invention, in order to obtain a copolymer contained in the pressure-sensitive adhesive composition, the nitrogen-containing cyclic compound, the (meth) acrylate compound, and the olefin compound are used as a copolymerization component. Is used.

  Since the pressure-sensitive adhesive composition according to the present invention has the above-described configuration, it is possible to achieve both a low dielectric constant and a high adhesive strength at a high level and to have a high impact resistance. it can. That is, since the pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition according to the present invention exhibits both low dielectric constant and high adhesive strength at a high level, it can be suitably used for optical applications. In particular, the adhesive tape can be suitably used for a touch panel because it can be adhered to a cover panel such as a cover glass with a sufficiently high adhesive force.

  Furthermore, since the pressure-sensitive adhesive composition according to the present invention has the above-described configuration, it can also improve impact resistance, and a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition according to the present invention is bonded to an object to be bonded. Sometimes peeling is less likely to occur.

Nitrogen-containing cyclic compounds:
The nitrogen-containing cyclic compound can be copolymerized with the (meth) acrylate compound, and further can be copolymerized with the olefin compound. The nitrogen-containing cyclic compound is preferably a monomer. As for the said nitrogen-containing cyclic compound, only 1 type may be used and 2 or more types may be used together.

  From the viewpoint of achieving both a low dielectric constant and high adhesive strength at a higher level, the nitrogen-containing cyclic compound preferably has a heterocyclic skeleton containing a nitrogen atom, and the heterocyclic ring containing nitrogen in the cyclic skeleton. A formula compound is preferred.

  Examples of the nitrogen-containing cyclic compound include acryloylmorpholine, pentamethylpiperidinyl methacrylate, tetramethylpiperidinyl methacrylate, and vinylpyrrolidone. From the viewpoint of achieving both a low dielectric constant and high adhesive strength at an even higher level, the nitrogen-containing cyclic compound is preferably vinyl pyrrolidone or acryloyl morpholine, and more preferably vinyl pyrrolidone.

(Meth) acrylate compounds:
The (meth) acrylate compound can be copolymerized with the nitrogen-containing cyclic compound, and further can be copolymerized with the olefin compound. The (meth) acrylate compound is preferably a monomer. The “(meth) acrylate” means acrylate and methacrylate. As for the said (meth) acrylate compound, only 1 type may be used and 2 or more types may be used together.

  Examples of the (meth) acrylate include isodecyl (meth) acrylate, isomistyryl (meth) acrylate, isododecyl (meth) acrylate, isostearyl (meth) acrylate, and isopentadecyl (meth) acrylate.

  In order to obtain the copolymer, the amount of the (meth) acrylate compound used exceeds 0 part by weight, more preferably 1 part by weight or more, preferably 150 parts by weight with respect to 100 parts by weight of the nitrogen-containing cyclic compound. Or less. When the content of the (meth) acrylate compound is not less than the above lower limit and not more than the above upper limit, it is possible to achieve both a low dielectric constant and high adhesive strength at a higher level, and the impact resistance is further enhanced. Furthermore, the compatibility between the nitrogen-containing cyclic compound and the olefin compound is increased. When the amount of the (meth) acrylate compound used is less than or equal to the above upper limit, the effect of increasing the adhesive strength is further exhibited.

Olefin compounds:
The olefin compound can be copolymerized with the nitrogen-containing cyclic compound, and further can be copolymerized with the (meth) acrylate compound. In the present specification, the olefin compound having a radical polymerizable unsaturated double bond does not include a (meth) acrylate compound having a branched alkyl group having 10 to 20 carbon atoms. As for the said olefin compound, only 1 type may be used and 2 or more types may be used together.

  Examples of the radical polymerizable unsaturated double bond include a vinyl group, a (meth) acryloyl group, and an allyl group. The radical polymerizable unsaturated double bond is preferably a vinyl group, a (meth) acryloyl group or an allyl group. The olefin compound may have a radical polymerizable unsaturated double bond (radical polymerizable unsaturated double bond-containing group) that is not a (meth) acryloyl group.

  The olefin compound may be a compound having a repeating structural unit of the radical polymerizable unsaturated double bond and the olefin skeleton, or may be a polymer.

  Examples of the olefin skeleton in the repeating structural unit of the radical polymerizable unsaturated double bond and the olefin skeleton include hydrogenated polybutadiene having one end of methacryl.

  Examples of commercially available olefin compounds include Claprene UC-203 (manufactured by Kuraray Co., Ltd.), Claprene L-1253 (manufactured by Kuraray Co., Ltd.), NISSO-PB B-3000 (manufactured by Nippon Soda Co., Ltd.), and the like.

  In order to obtain the copolymer, the amount of the olefin compound used is preferably 16 parts by weight or more, and preferably 800 parts by weight or less with respect to 100 parts by weight of the nitrogen-containing cyclic compound. When the usage-amount of the said olefin compound is more than the said minimum and below the said upper limit, a low dielectric constant and high adhesive force can be made compatible at a still higher level, and also impact resistance can be improved further.

Other details of the adhesive composition:
The copolymer comprises 100 parts by weight of the nitrogen-containing cyclic compound, 1 part by weight or more and 150 parts by weight or less of the (meth) acrylate compound, and 16 parts by weight or more and 800 parts by weight or less of the olefin compound. Is preferably obtained. When each component is used in such a preferable relationship, a portion derived from the nitrogen-containing cyclic compound having a relatively high polarity and a portion derived from the olefin compound having a relatively low polarity are finely phase-separated. For this reason, in the pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition, the transparency can be further increased, and the pressure-sensitive adhesive tape can be suitably used for optical applications, and the pressure-sensitive adhesive tape can be used as an optical pressure-sensitive adhesive tape. Can be suitably used. Moreover, a low dielectric constant and a high adhesive force can be achieved at an even higher level. Furthermore, when the optical adhesive tape is used for an optical laminate such as a touch panel, it is possible to absorb an impact when dropped due to a phase separation effect, and to exhibit high impact resistance.

  Whether the phase is finely separated or not is whether the pressure-sensitive adhesive tape (pressure-sensitive adhesive layer or pressure-sensitive adhesive layer portion) is osmium-stained and observed with a transmission electron microscope, and is phase-separated at a size of 1 nm to 1 μm. It can be determined by whether or not. With such a size, it is preferable that the part derived from the nitrogen-containing cyclic compound and the part derived from the olefin compound are phase-separated in the pressure-sensitive adhesive tape.

  In order to obtain the copolymer, as a copolymer component, a (meth) acrylate compound having a C 1-10 alkyl group, a carboxyl group-containing monomer, a hydroxyl group-containing monomer, a monomer having a cyclic ether group, or the like is used. Also good. As for these components, only 1 type may be used and 2 or more types may be used together.

  Examples of the (meth) acrylate compound having an alkyl group having 1 to 10 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobornyl (meth) acrylate, and cyclohexyl (meth) acrylate. Etc.

  Examples of the carboxyl group-containing monomer include (meth) acrylic acid, carboxyethyl (meth) acrylic acid, itaconic acid, maleic acid, and fumaric acid.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, allyl alcohol, and diethylene glycol. (Meth) acrylate etc. which have group are mentioned.

  When the carboxyl group-containing monomer and the hydroxyl group-containing monomer are used, the dielectric constant tends to increase. Accordingly, in 100% by weight of the copolymer component for obtaining the copolymer, the amount of the carboxyl group-containing monomer used is preferably 10% by weight or less, and the amount of the hydroxyl group-containing monomer used is 10% by weight or less. It is preferable that

  In 100% by weight of copolymerization component for obtaining the copolymer (total 100% by weight of copolymerizable components), the total of the nitrogen-containing cyclic compound, the (meth) acrylate compound, and the olefin compound. The amount used (content) is preferably 30% by weight or more, more preferably 35% by weight or more and 100% by weight (total amount) or less. In 100% by weight of the copolymer component, the total amount of the nitrogen-containing cyclic compound, the (meth) acrylate compound, and the olefin compound may be 85% by weight or less, and 75% by weight or less. May be.

  As a manufacturing method of the said adhesive composition, well-known manufacturing methods, such as solution polymerization, UV polymerization, block polymerization, and emulsion polymerization, can be selected suitably. Among these, the solution polymerization or the UV polymerization is preferable because the phase separation size can be easily controlled well.

  Examples of the solvent that can be used in the solution polymerization include ethyl acetate, toluene, tetrahydrofuran, and methyl ethyl ketone. As for the said solvent, only 1 type may be used and 2 or more types may be used together.

  In order to obtain the copolymer, a polymerization initiator can be used. The polymerization initiator is not particularly limited, and can be appropriately selected and used. The polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator. As for the said polymerization initiator, only 1 type may be used and 2 or more types may be used together.

  Examples of the thermal polymerization initiator that can be used in the above solution polymerization include an azo compound (azo polymerization initiator), a peroxide (peroxide polymerization initiator), and a redox in which a peroxide and a reducing agent are combined. And system initiators.

  Examples of the azo compound include azobisisobutyronitrile, azobismethylbutyronitrile, azobis (2-methylpropionic acid) dimethyl, and the like. Examples of the peroxide include organic peroxides, specifically, dibenzoyl peroxide, diisobutyl peroxide, hexyl peroxypivalate, di (3,5,5-trimethylhexanoyl) peroxide, dilauroyl. Examples include peroxide, tetramethylbutyl peroxyethyl hexanoate, hexyl peroxyethyl hexanoate, and the like.

  Examples of the photopolymerization initiator that can be used in the UV polymerization include benzoin ether initiators, acetophenone initiators, benzoin initiators, benzophenone initiators, ketal initiators, and sulfonyl chloride initiators. It is done.

  The weight average molecular weight of the copolymer is preferably 400,000 or more, more preferably 600,000 or more, preferably 2.5 million or less, more preferably 2 million or less. When the weight average molecular weight is not lower than the lower limit and not higher than the upper limit, the adhesive force of the pressure-sensitive adhesive tape is further increased.

  The said weight average molecular weight shows the weight average molecular weight in polystyrene conversion measured by gel permeation chromatography.

  It is preferable that the said adhesive composition contains a crosslinking agent. By using the cross-linking agent, the copolymer can be further cross-linked at the time of adhesion, and an even higher adhesive force can be expressed. In addition, when the said adhesive composition does not contain a crosslinking agent, the said adhesive composition may be used by adding a crosslinking agent. As for the said crosslinking agent, only 1 type may be used and 2 or more types may be used together.

  Examples of the crosslinking agent include epoxy crosslinking agents, isocyanate crosslinking agents, and hydrazide crosslinking agents. The crosslinking agent is preferably an epoxy-based crosslinking agent or an isocyanate-based crosslinking agent because higher adhesive strength is exhibited.

  The epoxy-based crosslinking agent is, for example, a compound having two or more epoxy groups. Examples of the epoxy crosslinking agent include bisphenol A, diglycidyl aniline, diamine glycidyl amine, ethylene glycol diglycidyl ether, adipic acid diglycidyl ester, and tetrad X (manufactured by Mitsubishi Gas Chemical Company). As for the said epoxy type crosslinking agent, only 1 type may be used and 2 or more types may be used together.

  The said isocyanate type crosslinking agent is a compound which has two or more blocked isocyanate which protected the isocyanate group or the isocyanate group primarily, for example. Examples of the isocyanate-based crosslinking agent include cyclohexylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate. Examples of commercially available isocyanate crosslinking agents include Coronate L (manufactured by Nippon Polyurethane), Coronate HL (manufactured by Nippon Polyurethane), Coronate HX (manufactured by Nippon Polyurethane), and Mytec NY260A (manufactured by Mitsubishi Chemical). It is done. As for the said isocyanate type crosslinking agent, only 1 type may be used and 2 or more types may be used together.

  The usage-amount of the said crosslinking agent can be adjusted suitably, and is not specifically limited. The amount (content) of the crosslinking agent used is preferably 1 part by weight or more and preferably 5 parts by weight or less with respect to 100 parts by weight of the copolymer. When the amount of the crosslinking agent used is not less than the above lower limit and not more than the above upper limit, the cohesive force and the adhesive force are more favorably expressed.

  The pressure-sensitive adhesive composition may contain other known additives. The pressure-sensitive adhesive composition may appropriately contain, for example, a silane coupling agent, a tackifier, a leveling agent, an antioxidant, a light stabilizer, an ultraviolet absorber, and a polymerization inhibitor as necessary. .

  A pressure-sensitive adhesive layer can be formed using the pressure-sensitive adhesive composition. This pressure-sensitive adhesive layer can be used as a pressure-sensitive adhesive tape alone or in a state of being laminated on a support. The gel fraction of the pressure-sensitive adhesive layer is preferably 40% by weight or more, more preferably 50% by weight or more, preferably 99% by weight or less, more preferably 98% by weight or less. When the gel fraction is not less than the above lower limit and not more than the above upper limit, the cohesive force and the adhesive force are more favorably expressed.

  A pressure-sensitive adhesive layer and a pressure-sensitive adhesive tape can be formed by coating the pressure-sensitive adhesive composition on a support and drying it. A conventionally well-known method can be used as a coating method of the said adhesive composition. Examples of the coating method include a method using a roll coater, a gravure coater, a reverse coater, a lip coater, a curtain coater, and a slit die coater. When the solution polymerization is performed, the solvent can be removed by drying during coating. In the case of performing the UV polymerization, the polymerization can be performed at the time of UV irradiation.

  Examples of the support include plastic films such as polyethylene film, polypropylene film, polyethylene terephthalate film and polyester film, paper, foamed sheet, metal foil, metal oxide film, and laminates thereof. The surface of the support may be subjected to a release treatment in order to improve the peelability.

  The pressure-sensitive adhesive composition is suitably used for obtaining an optical pressure-sensitive adhesive tape. The optical pressure-sensitive adhesive tape can be obtained using the pressure-sensitive adhesive composition.

  Applications of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive tape are not particularly limited. The pressure-sensitive adhesive layer and the pressure-sensitive adhesive tape can be suitably used for optical applications, and can be more suitably used to obtain an optical laminate. The adhesive tape is preferably an optical adhesive tape.

  The said adhesive layer and the said adhesive tape can be used suitably for the use adhere | attached on a cover glass, and can be used especially suitably for a touchscreen. The pressure-sensitive adhesive layer and the pressure-sensitive adhesive tape are a cover panel (a glass plate, a glass plate, a surface plate) for manufacturing an image display device such as a mobile phone, a smartphone, a personal computer, electronic paper, a tablet personal computer, and a game machine. Or a polymethyl methacrylate plate) and a touch panel module, a cover panel and a display panel module, or a touch panel module and a display panel module.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

Example 1
(1) Production of copolymer A reactor equipped with a thermometer, a stirrer and a cooling tube was prepared. In this reactor, 10 parts by weight of vinylpyrrolidone, 15 parts by weight of isostearyl acrylate, 20 parts by weight of Claprene L-1253 (manufactured by Kuraray Co., Ltd.), 39.5 parts by weight of 2-ethylhexyl acrylate, 14 parts by weight of isobornyl acrylate, 90 parts by weight of toluene was added to 1 part by weight of n-butyl acrylate and 0.5 parts by weight of acrylic acid, and 100 parts by weight of these monomers (copolymerization components), and nitrogen was substituted for 30 minutes by blowing nitrogen gas. . Thereafter, the inside of the reactor was heated to 70 ° C. After heating for 30 minutes, a polymerization initiator solution prepared by diluting 0.12 parts by weight of t-hexylperoxypivalate as a polymerization initiator with 10 parts by weight of toluene was added dropwise to the reactor over 5 hours ( The amount of the polymerization initiator used is 0.12 parts by weight based on 100 parts by weight of the monomer). It was made to react at 70 degreeC for 8 hours from the start of addition of a polymerization initiator, and obtained the copolymer solution whose copolymer solid content is 50 weight%.

(2) Production of optical pressure-sensitive adhesive tape To the obtained copolymer solution, tetrad X (manufactured by Mitsubishi Gas Chemical Co., Ltd.), which is a cross-linking agent, is converted to a solid content of 0. 2 parts by weight, Mytec NY260A (Mitsubishi Chemical Co., Ltd.) is 2 parts by weight in terms of solids, and silane coupling agent KBM-403 (Shin-Etsu Chemical Co., Ltd.) is 0.5 parts by weight in terms of solids. Were added as described above and stirred to prepare an adhesive composition.

  The obtained pressure-sensitive adhesive composition was coated on a release-treated surface of a release polyethylene terephthalate (PET) film, and dried at 100 ° C. for 10 minutes to remove toluene, thereby forming a pressure-sensitive adhesive layer having a thickness of 100 μm. Formed.

  Furthermore, on the obtained pressure-sensitive adhesive layer, a newly prepared release PET film was superposed so that the pressure-sensitive adhesive layer was in contact with the release treatment surface to obtain a laminate. By pressing the obtained laminate with a rubber roller, an optical pressure-sensitive adhesive tape (pressure-sensitive adhesive layer thickness of 100 μm) in which a release PET film was adhered to both surfaces of the pressure-sensitive adhesive layer was obtained.

(Examples 2-5 and Comparative Examples 1-5)
A copolymer solution was obtained in the same manner as in Example 1 except that the types and amounts of monomers constituting the copolymer were changed as shown in Table 1 below. Except having used the obtained copolymer solution, it carried out similarly to Example 1, and obtained the adhesive composition and the adhesive tape for optics.

(Evaluation)
The obtained optical adhesive tape was evaluated for the following evaluation items. The results are shown in Table 1 below.

(1) Evaluation of relative dielectric constant The obtained optical pressure-sensitive adhesive tape (thickness of the pressure-sensitive adhesive layer 100 μm) was cut so as to have a planar shape of 30 mm × 30 mm. Next, one release PET film of the adhesive tape was peeled off and bonded to a copper foil (thickness 50 μm). Furthermore, the other release PET film of the adhesive tape was peeled off and bonded to a copper foil (thickness 50 μm). Thus, the lamination sample which affixed copper foil on both surfaces of the adhesive layer was obtained. The obtained laminated sample was sandwiched between circular electrodes using an impedance analyzer (SI1260 type, manufactured by Toyo Corporation). In this state, the relative dielectric constant at a frequency of 1 MHz was measured according to JIS K6911. The relative dielectric constant was determined according to the following criteria.

[Criteria for relative permittivity]
○: Relative permittivity is less than 3.0 Δ: Relative permittivity is 3.0 or more, less than 3.5 ×: Relative permittivity is 3.5 or more

(2) Evaluation of adhesive strength The obtained optical pressure-sensitive adhesive tape (pressure-sensitive adhesive layer thickness 100 μm) was cut into a width of 25 mm and a length of 100 mm. Next, one release PET film of the adhesive tape was peeled off and attached to a polyethylene terephthalate (PET) film (thickness 25 μm). Furthermore, in a temperature-controlled room with a room temperature of 23 ° C. and a humidity of 50%, the other release PET film of the adhesive tape is peeled off, and a cover glass (reinforced alkali glass, Corning gorilla glass) is covered with a 2 kg rubber roller. The sample was reciprocated once and bonded, and left for 30 minutes to obtain an evaluation sample. Next, about the obtained evaluation sample, the peeling adhesive force (adhesive force) with respect to the cover glass of the adhesive layer in an optical adhesive tape was measured on conditions with a peeling angle of 180 degree | times and a peeling speed of 300 mm / min. The adhesive strength was determined according to the following criteria.

[Adhesion criteria]
○: Adhesive strength is 10 N / 25 mm or more ×: Adhesive strength is less than 10 N / 25 mm

(3) Impact resistance An optical adhesive tape cut into a frame shape with a width of 2 mm and an outer circumference of 45 mm × 60 mm on a polycarbonate plate (thickness 2 mm) with a center of 35 mm × 50 mm cut out. It bonded together with the 2kg roller. Next, a cover glass (strengthened alkali glass, Corning gorilla glass) was applied from above and bonded together. Then, the autoclave was processed at 0.4 Mpa and room temperature for 1 hour to obtain an evaluation sample. Next, the obtained evaluation sample was placed so that the cover glass was on the lower side, a weight having a weight of 200 g was dropped on the hole portion from above, and the height when the cover glass was peeled off from the polycarbonate plate was measured. . Impact resistance was determined according to the following criteria.

[Evaluation criteria for impact resistance]
○: Falling ball height until peeling is 10 cm or more ×: Falling ball height until peeling is less than 10 cm

Claims (6)

  A nitrogen-containing cyclic compound having a nitrogen atom and a cyclic skeleton, a (meth) acrylate compound having a branched alkyl group having 10 to 20 carbon atoms, and an olefin compound having a radical polymerizable unsaturated double bond A pressure-sensitive adhesive composition comprising a copolymer obtained by polymerization.   The copolymer copolymerizes 100 parts by weight of the nitrogen-containing cyclic compound, 1 part by weight or more and 150 parts by weight or less of the (meth) acrylate compound, and 16 parts by weight or more and 800 parts by weight or less of the olefin compound. The pressure-sensitive adhesive composition according to claim 1, obtained by   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the nitrogen-containing cyclic compound is vinylpyrrolidone or acryloylmorpholine.   The pressure-sensitive adhesive composition according to claim 1 or 2, which is used for obtaining an optical pressure-sensitive adhesive tape.   The pressure-sensitive adhesive composition according to claim 3, which is used for obtaining an optical pressure-sensitive adhesive tape.   The optical adhesive tape obtained using the adhesive composition of any one of Claims 1-5.