JP2016084438A - Adhesive film, information display device and portable electronic terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive film achieving both of high relative dielectric constant and excellent step followability even with thin type.SOLUTION: An adhesive film attaching to a face consisting of nonmetallic member constituting a surface of an information display part is obtained by using an acrylic polymer (A) obtained by polymerizing a monomer containing (meth)acrylic acid alkoxyalkyl (a1) and (meth)acrylic acid hydroxyalkyl having a hydroxyalkyl group having 3 or less carbon atoms (a2) and a crosslinking agent (B).SELECTED DRAWING: None

Description

  The present invention relates to an adhesive film that can be used for adhesion between an information display unit of an information display device and a surface protection member.

  Many portable electronic terminals such as smartphones are equipped with a display with a touch panel function. A protective adhesive film is often attached to the surface of the information display portion of the display for the purpose of preventing the surface from being scratched when repeatedly touched with a finger or a touch pen.

  However, even when an operation is attempted by bringing a finger or the like into contact with the surface to which the protective adhesive film has been applied, the sensitivity decreases due to the provision of the protective adhesive film, which may cause a significant decrease in operability. .

  As the protective adhesive film that does not cause deterioration of the operability, for example, for a capacitive touch panel, development of a protective adhesive film that ensures good operability by thinning the adhesive layer is considered. Has been.

  However, simply reducing the thickness of the pressure-sensitive adhesive layer of the protective adhesive film cannot follow the stepped portion derived from the decorative layer provided on the frame portion of the adherend, and is displayed on the portable electronic terminal. In some cases, the visibility of images and the like is reduced.

  Moreover, the protective adhesive film having a thick adhesive layer to improve the step following ability sometimes causes a decrease in operability due to a decrease in relative dielectric constant.

  Thus, it has been difficult to obtain a pressure-sensitive adhesive film that is thin and has both a high relative dielectric constant and excellent step following ability.

  By the way, as an information display device corresponding to the above-mentioned thinning and the like, an information display device including a liquid crystal module having a touch panel function called a so-called on-cell type or in-cell type has been developed.

  However, the outermost surface of the information display unit of the information display device is usually a polarizing plate constituting the liquid crystal module, and when a touch pen, a finger, or the like is brought into contact with the surface of the polarizing plate, The pressure may cause dents or scratches on the polarizing plate.

  As a method for preventing damage to the polarizing plate, for example, a method is known in which a glass substrate is provided on the surface side of the polarizing plate, and a protective adhesive film is provided on the surface of the glass substrate (for example, (See Patent Document 1).

  However, the glass substrate is relatively expensive, and the portable electronic terminal obtained using the glass substrate is thick and heavy, so that it cannot cope with the reduction in thickness and weight required by the industry. was there.

  Examples of the information display device that achieves both weight reduction and thickness reduction include those in which a thin protective adhesive film is directly provided on the surface of a polarizing plate or the like.

  However, the conventional thin protective adhesive film cannot follow the step portion derived from the decorative layer provided on the frame portion of the adherend, causing a decrease in the visibility of the image displayed on the portable electronic terminal, etc. was there.

  Moreover, the protective adhesive film that has been thickened to improve the step following ability sometimes causes a decrease in operability due to a decrease in relative dielectric constant.

  Thus, it has been difficult to obtain a pressure-sensitive adhesive film that is thin and has both a high relative dielectric constant and excellent step following ability.

JP 2008-095064 A

  The problem to be solved by the present invention is to provide a pressure-sensitive adhesive film that has both a high relative dielectric constant and excellent step following ability even if it is thin.

  The present invention is an adhesive film to be attached to a surface made of a non-metallic member constituting the surface of the information display unit, wherein the adhesive film is an alkoxyalkyl (meth) acrylate (a1) and having 3 or less carbon atoms. It is obtained by using an acrylic polymer (A) obtained by polymerizing a monomer containing a hydroxyalkyl group-containing (meth) acrylic acid hydroxyalkyl (a2) and a crosslinking agent (B). The said subject is solved by the adhesive film characterized by the above-mentioned.

  Even if the pressure-sensitive adhesive film of the present invention is thin, it can achieve both a high relative dielectric constant and excellent step following ability. Therefore, the pressure-sensitive adhesive film of the present invention is preferably used as a protective pressure-sensitive adhesive film to be attached to the surface of a non-metallic member such as a polarizing plate constituting a liquid crystal module having a touch panel function called a so-called on-cell type or in-cell type. Can do.

  The pressure-sensitive adhesive film of the present invention polymerizes a monomer containing an alkoxyalkyl (meth) acrylate (a1) and a hydroxyalkyl (meth) acrylate (a2) having a hydroxyalkyl group having 3 or less carbon atoms. Obtained by using the acrylic polymer (A) and the cross-linking agent (B), which are used exclusively by sticking to a surface made of a non-metallic member constituting the surface of the information display section. It is characterized by.

  As the acrylic polymer (A), a monomer containing an alkoxyalkyl (meth) acrylate (a1) and a hydroxyalkyl (meth) acrylate (a2) having a hydroxyalkyl group having 3 or less carbon atoms. The one obtained by polymerizing is used.

  Examples of the alkoxyalkyl (meth) acrylate (a1) include 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, and methoxytriethylene glycol acrylate such as light acrylate MTG-A manufactured by Kyoeisha Chemical Co., Ltd. 2-Ethoxydiethylene glycol acrylate (2- (2-ethoxyethoxy) ethyl acrylate) such as light acrylate EC-A manufactured by Kyoeisha Chemical Co., Ltd., 3-methoxypropyl acrylate, 3-ethoxypropyl acrylate, 4-acrylic acid 4- Methoxybutyl, 4-ethoxybutyl acrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-methoxytriethylene glycol methacrylate, 2- (2-ethoxyethoxy) ethyl methacrylate, 3-methyl methacrylate Kishipuropiru, may be used methacrylic acid 3-ethoxypropyl, 4-methoxybutyl methacrylate, methacrylic acid 4-ethoxy butyl. Especially, as said (meth) acrylic-acid alkoxyalkyl (a1), using 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate can provide a still higher dielectric constant, and is high temperature environment. Since the adhesive force of the level which can suppress the float and peeling of the said adhesive film in the level | step difference part below can be expressed, it is preferable.

  The alkoxyalkyl (meth) acrylate (a1) is preferably used in the range of 50% by mass to 90% by mass with respect to the total amount of monomers used for the production of the acrylic polymer (A). It is more preferable to use in the range of mass% to 90% by mass, and use in the range of 70% to 90% by mass can provide a higher relative dielectric constant, and the step in the stepped portion under a high temperature environment. It is particularly preferable for producing a pressure-sensitive adhesive film that can exhibit a level of adhesive strength that can suppress the lifting and peeling of the pressure-sensitive adhesive film, and that does not easily become clouded even in a high-temperature and high-humidity environment.

  Examples of the hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 3 or less carbon atoms used in the production of the acrylic polymer (A) include 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. In addition, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, and the like can be used.

  Especially, it is preferable to use 2-hydroxyethyl acrylate as the hydroxyalkyl (meth) acrylate (a2) having a hydroxyalkyl group having 3 or less carbon atoms.

  The hydroxyalkyl (meth) acrylate (a2) having a hydroxyalkyl group having 3 or less carbon atoms is 0.1% by mass to the total amount of monomers used for the production of the acrylic polymer (A). It is preferably used in the range of 10% by mass, more preferably in the range of 0.3% by mass to 5% by mass, and in the range of 0.5% by mass to 2.5% by mass, It is more preferable because it is excellent in initial step following property and can suppress the peeling and peeling of the pressure-sensitive adhesive film at the step portion in a high temperature environment.

  As a monomer that can be used in the production of the acrylic polymer (A), other monomers can be used as necessary in addition to the above-described monomers.

  As the other monomer, for example, alkyl (meth) acrylate (a3) having an alkyl group having 3 or more carbon atoms can be used.

  Examples of the alkyl (meth) acrylate (a3) having an alkyl group having 3 or more carbon atoms include n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, and t-acrylate. Butyl, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate and the like can be used.

  Among them, as the alkyl (meth) acrylate (a3), it is possible to use n-butyl acrylate, which has a high relative dielectric constant and suppresses the sticking and peeling of the adhesive film at a step portion in a high temperature environment. It is preferable because it can prevent white turbidity of the adhesive film under high temperature and high humidity conditions.

  The alkyl (meth) acrylate (a3) is preferably used in the range of 5% by mass to 45% by mass with respect to the total amount of monomers used for the production of the acrylic polymer (A). More preferably, the adhesive film is used in the range of 35% by mass to 35% by mass, and is preferably used in the range of 5% by mass to 25% by mass. Is preferable because it can suppress the floating and peeling of the adhesive film, and can prevent white turbidity of the adhesive film under high temperature and high humidity conditions.

  Moreover, as a monomer which can be used for manufacture of the said acrylic polymer (A), the monomer which has an acid group can also be used.

  As the monomer having an acid group, for example, acrylic acid or methacrylic acid can be used.

  The monomer having an acid group is preferably used in a range of 10% by mass or less, based on the total amount of monomers used for the production of the acrylic polymer (A), and in a range of 5% by mass or less. It is more preferable to use it in order to obtain a pressure-sensitive adhesive film having moderate flexibility and good step following ability.

  The acrylic polymer (A) can be produced, for example, by radical polymerization of the monomer.

  The radical polymerization can be performed by, for example, a thermal polymerization method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a polymerization method performed by irradiating active energy rays such as light or radiation. Especially, as said polymerization method, it is preferable to employ | adopt solution polymerization method, when maintaining favorable workability | operativity, quality stability, etc.

  Examples of the solvent that can be used in the solution polymerization method include ethyl acetate, hexane, cyclohexane, methylcyclohexane, isopropyl alcohol, 1-butanol, secondary butanol, tertiary butanol, tertiary butyl methyl ether, methyl ethyl ketone, acetylacetone, 1, 2 -Dichloroethane etc. can be used, It is preferable to use ethyl acetate, hexane, cyclohexane, methylcyclohexane, isopropyl alcohol, etc.

  As the acrylic polymer (A) obtained by the above method, those having a weight average molecular weight of 300,000 to 1,600,000 are preferably used, and those having a weight average molecular weight of 400,000 to 1.3 million are used. It is more preferable that using a material having a weight average molecular weight of 500,000 to 1,000,000 is excellent in initial step followability and can suppress floating and peeling of the pressure-sensitive adhesive film in a step portion under a high temperature environment. Therefore, it is more preferable.

  Moreover, as said acrylic polymer (A), it is preferable to use that whose molecular weight distribution (weight average molecular weight / number average molecular weight) is 10-50, and it is more preferable to use 10-30. It is preferable to use 10 to 20 because it is excellent in the initial step followability and can suppress the lifting and peeling of the pressure-sensitive adhesive film in the step portion under a high temperature environment.

The weight average molecular weight and the number average molecular weight can be measured by gel permeation chromatograph (GPC). More specifically, as a GPC measurement device, “SC8020” manufactured by Tosoh Corporation can be used to measure and obtain the following GPC measurement conditions based on polystyrene conversion values.
(GPC measurement conditions)
Sample concentration: 0.5% by mass (tetrahydrofuran solution)
Sample injection volume: 100 μL
・ Eluent: Tetrahydrofuran (THF)
・ Flow rate: 1.0 mL / min
Column temperature (measurement temperature): 40 ° C
Column: “TSKgel GMHHR-H” manufactured by Tosoh Corporation
Detector: differential refraction Further, the molecular weight distribution can be calculated by dividing the weight average molecular weight obtained by the above measurement by the number average molecular weight.

  As an adhesive composition which can be used for manufacture of the adhesive film of this invention, what contains a crosslinking agent (B) other than the said acrylic polymer (A) is used. By using the said crosslinking agent (B), the outstanding adhesive film which can suppress the float and peeling of the said adhesive film in the level | step-difference part in a high temperature environment can be obtained.

  As said crosslinking agent (B), an isocyanate type crosslinking agent, an epoxy-type crosslinking agent, a chelate type crosslinking agent, an azirine type crosslinking agent, a polyfunctional acrylate type crosslinking agent etc. can be used, for example. Especially, it is preferable to use the isocyanate type crosslinking agent rich in the reactivity with the hydroxyl group which the said acrylic polymer (A) has as said crosslinking agent (B).

  The crosslinking agent (B) is preferably used in a range of 0.05 to 2 parts by mass with respect to 100 parts by mass of the acrylic polymer (A), and 0.07 to 1.5 parts by mass. More preferably, it is used in the range of 0.1 parts by weight to 1 part by weight, excellent in initial step followability, and the pressure-sensitive adhesive film floats on the stepped part in a high-temperature environment. It is more preferable because peeling can be suppressed.

  As the pressure-sensitive adhesive composition, in addition to the acrylic polymer (A) and the cross-linking agent (B), it is possible to improve the production efficiency of the pressure-sensitive adhesive film by using one containing a solvent as necessary. Is preferable. As said solvent, the thing similar to the solvent illustrated as what can be used when manufacturing the said acrylic polymer (A) by a radical polymerization method can be used.

  As the pressure-sensitive adhesive composition of the present invention, in addition to the above, an ultraviolet absorber, a light stabilizer, an anti-aging agent, a release modifier, a tackifier, a plasticizer, a softener, a filler, and a colorant, if necessary. (Pigments, dyes, etc.), surfactants and the like can be used.

  As a method for producing the pressure-sensitive adhesive film of the present invention, for example, if it is a pressure-sensitive adhesive film having a base material (core), the pressure-sensitive adhesive composition is coated on one side or both sides of the base material and dried. After forming the pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive composition to the surface of the release liner or drying the method (direct method), the pressure-sensitive adhesive layer is transferred to one or both sides of the substrate. The method (transfer method) of manufacturing by doing is mentioned.

  In addition, a so-called substrate-less pressure-sensitive adhesive film constituted by a pressure-sensitive adhesive layer without having the base material is formed by, for example, applying a pressure-sensitive adhesive composition on the surface of a release liner and drying the pressure-sensitive adhesive layer. It can be manufactured by forming.

  Examples of the substrate include polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polyolefin, polyacrylate, polyvinyl chloride, polyethylene, polypropylene ethylene vinyl alcohol, polyurethane, polyamide, and polyimide. Sheet or film; glass or the like can be used.

  The surface of the substrate may be subjected to release treatment, antistatic treatment, corona treatment, and the like.

  Although the thickness of the said base material is determined according to the use for which an adhesive sheet is used, it is preferable that it is the range of 10 micrometers-100 micrometers, for example.

  As the substrate, a substrate having a hard coat layer on at least one surface may be used in order to prevent scratches and the like from being produced in the production process of the adhesive film.

  As the hard coat layer that the substrate may have, it is preferable to use an acrylic resin-containing layer in order to further improve the adhesion between the pressure-sensitive adhesive layer and the hard coat layer.

  Examples of the method for applying the pressure-sensitive adhesive composition to the substrate or release liner include a method using an applicator, a roll coater, a gravure coater, a reverse coater, a spray coater, an air knife coater, a die coater, and the like. It is done.

  Examples of the method for drying the pressure-sensitive adhesive composition include a method of drying at 50 to 140 ° C. for 30 seconds to 10 minutes. Moreover, after the said drying, in order to accelerate | stimulate reaction with the said acrylic polymer (A) and a crosslinking agent (B), the said dried thing is cured at the temperature of 20 to 40 degreeC for about 1 to 10 days. May be.

  The pressure-sensitive adhesive layer of the pressure-sensitive adhesive film obtained by the above method preferably has a gel fraction represented by the following formula of 30% by mass to 80% by mass when immersed in toluene for 24 hours, and 30% by mass. It is more preferably ~ 70% by mass, and a range of 35% by mass to 55% by mass can maintain an excellent adhesive force on the surface of the nonmetallic member for a long period of time. It is particularly preferable because it has good followability with respect to a certain step portion, and as a result, it is difficult to leave bubbles at the interface between the step portion and the adhesive film.

  The gel fraction was applied to the surface of a polyethylene terephthalate (PET) film having a thickness of 38 μm, and the pressure-sensitive adhesive composition was applied so that the film thickness after drying was 20 μm. 2 hours at 120 ° C., 2 minutes at 120 ° C., 1 minute at 140 ° C., and then cured at 40 ° C. for 3 days before the adhesive film consisting of the adhesive layer is immersed in toluene for 24 hours; It is the value calculated based on the following formula by measuring the mass after immersion.

  Gel fraction (mass%) = [(mass of adhesive film before immersing in toluene) / (mass of material remaining after immersing adhesive film in toluene)] × 100

As the pressure-sensitive adhesive layer, one having a storage elastic modulus at 70 ° C. of a dynamic viscoelasticity spectrum measured at a frequency of 1 Hz is included in a range of 4.0 × 10 ^{4 to} 9.0 × 10 ⁵ Pa. is preferably included in 4.0 is more preferable to use intended to be included within the scope of ^{× 10 4 ~8.0 × 10 4 Pa} , 4.0 range × ¹⁰ 4 ~7.0 × ¹⁰ 4 Pa It is more preferable to use a material that has a further excellent step following property and prevents the pressure-sensitive adhesive film from floating and peeling over time.

  The dynamic viscoelasticity of the pressure-sensitive adhesive layer is determined by inserting a test piece between parallel disks, which are measuring units of the test machine, using a viscoelasticity tester (trade name: Ares 2KSTD, manufactured by Rheometrics Co., Ltd.). It is obtained by measuring storage elastic modulus (G ′) and loss elastic modulus (G ″) at 1 Hz. The test piece can be obtained by sandwiching an adhesive having a thickness of 0.5 to 2.5 mm between parallel disks alone. However, the laminate of the base material and the pressure-sensitive adhesive may be overlapped and sandwiched between parallel disks, and in the latter case, the thickness of the pressure-sensitive adhesive alone is adjusted to be in the above range.

  The pressure-sensitive adhesive film of the present invention obtained by the above method can be used by being laminated on the surface of a non-metallic member constituting the surface of the information display unit, and is equipped with a touch panel function called a so-called on-cell type or in-cell type. It can be used by being laminated on the surface of the information display unit.

  As the non-metallic member, for example, a polarizing plate, a retardation film, an antireflection film and the like can be used.

  The pressure-sensitive adhesive film of the present invention may be appropriately selected depending on the mode to be used. However, in order to achieve both reduction in thickness of the touch panel device and further improvement in operability (touch panel response) by increasing the capacitance. It is preferable to use a material having a thickness of 5 μm to 500 μm, more preferably a material having a thickness of 10 μm to 250 μm. Furthermore, in order to improve the step following property, the thickness is 20 μm or more. It is preferable to use one having a thickness of 25 μm to 150 μm.

  As the pressure-sensitive adhesive film of the present invention, for example, a transparent base material having the pressure-sensitive adhesive layer on one side or both sides thereof may be used. A less adhesive film can also be used. The pressure-sensitive adhesive layer may be a single layer or a plurality of layers may be laminated.

  Moreover, as an adhesive film of this invention, the hard-coat layer may be provided in the single side | surface or both surfaces of the said base material, and the said adhesive layer may be provided in the surface of the said hard-coat layer. An adhesive film in which a hard coat layer is provided on one surface of the substrate and an adhesive layer is provided on the other surface can be suitably used as a so-called anti-scattering adhesive film.

  As the pressure-sensitive adhesive film of the present invention, it is preferable to use a film having a relative dielectric constant of 4 or more measured by an automatic equilibrium bridge method, preferably a film having a dielectric constant of 5 to 11, and preferably 6 to 10. The low dielectric constant of the protective adhesive film in which the adhesive film and the surface protective member are laminated, even if a low dielectric constant member such as a plastic member is used as the surface protective member to be described later It is more preferable because it is possible to suppress the increase in the size and as a result, it is possible to achieve both high operability (touch panel response) and prevention of malfunction.

  As the information display device of the present invention, the pressure-sensitive adhesive film has a structure in which a surface made of a nonmetallic member constituting the surface of the information display unit and a surface protection member are bonded.

  Examples of the surface protective member include a glass member, a plastic member, a glass member provided with a hard coat layer, a plastic member provided with a hard coat layer, and an organic-inorganic hybrid resin member. As the surface protection member, a plate, film or sheet can be used.

Examples of the material constituting the plastic member include acrylic resin, polyester, polycarbonate, polyolefin, polyamide, and cellulose.

  As the non-metallic member, for example, a polarizing plate, a retardation film, an antireflection film and the like can be used. As the polarizing plate, a general one in which a polarizer protective layer is laminated on both sides of a polarizer can be used.

  A polarizer obtained by using a polyvinyl alcohol-based resin can be used. The polyvinyl alcohol resin can be produced by saponifying a polyvinyl acetate resin.

  The polarizer can be produced, for example, by adsorbing and orienting a dichroic dye on the formed polyvinyl alcohol resin film.

  Moreover, a polarizing plate can be manufactured by laminating | stacking polarizer protective layers, such as a triacetyl cellulose film, on both surfaces of the polarizer obtained above through an adhesive layer.

  As the dichroic dye, iodine or a dichroic organic dye can be used. In order to dye the polyvinyl alcohol-based resin film with a dichroic dye, the polyvinyl alcohol-based resin film can be immersed in an aqueous solution containing these dyes. When iodine is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed.

  Although it does not specifically limit as said polarizer protective layer, On the assumption that it uses as a display material, it is preferable to use what is obtained using resin which is excellent in transparency.

  Examples of the polarizer protective layer include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, poly Vinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, cycloolefin resin film, polymethylpentene film, polysulfone film, polyether ether ketone film, polyether sulfone film, polyether Imide film, polyimide film, fluorine resin film, nylon Irumu, acrylic resin film or the like.

  Moreover, when forming a polarizer protective layer on both surfaces of the said polarizer layer, it is possible to form the polarizer protective layer comprised from different resin on each surface. For example, a polarizer protective layer made of a triacetyl cellulose film can be formed on one side of the polarizer layer, and a polarizer protective layer made of a cycloolefin-based resin film can be formed on the other side.

  As the polarizing plate, it is preferable to use a polarizing plate having a thickness of 50 μm to 200 μm because it can contribute to weight reduction and thickness reduction of the information display device and the portable electronic terminal.

  As the information display device of the present invention, the non-display of the information display unit having a configuration in which a touch panel member is laminated on one side of a liquid crystal display panel and a non-metallic member including a polarizing plate is laminated on the surface of the touch panel member. What has the structure where the surface of the metal member and the said surface protection member were laminated | stacked through the adhesive film of this invention is mentioned. The information display device can be mounted on various electronic devices such as a portable electronic terminal.

  The present invention will be specifically described below with reference to examples and comparative examples.

<Preparation Example 1>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 75 parts by mass of 2-methoxyethyl acrylate, 24 parts by mass of n-butyl acrylate, and 2-hydroxyethyl acrylate 1 part by mass and 0.2 part by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate, and the inside of the reaction vessel was purged with nitrogen. An acrylic polymer (A1) solution having a weight average molecular weight of 700,000 was obtained by polymerizing for a time.

  Next, the acrylic polymer (A1) solution and ethyl acetate are mixed to adjust the nonvolatile content thereof, whereby the pressure-sensitive adhesive composition (a) having a nonvolatile content of 30% by mass of the acrylic polymer (A1). Got.

<Preparation Example 2>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 75 parts by mass of 2-methoxyethyl acrylate, 16 parts by mass of n-butyl acrylate, and 8 parts by mass of methyl methacrylate And 1 part by mass of 2-hydroxyethyl acrylate and 0.2 part by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator in 100 parts by mass of ethyl acetate, and the inside of the reaction vessel was purged with nitrogen They were polymerized at 80 ° C. for 8 hours to obtain an acrylic polymer (A2) solution having a weight average molecular weight of 700,000.

  Next, the pressure-sensitive adhesive composition (b) having a nonvolatile content of 30% by mass by mixing the acrylic polymer (A2) solution and ethyl acetate and adjusting the nonvolatile content of the acrylic polymer (A2). Got.

<Preparation Example 3>
Preparation Example 1 except that the amount of n-butyl acrylate used is changed from 24 parts by weight to 22 parts by weight and the amount of 2-hydroxyethyl acrylate used is changed from 1 part by weight to 3 parts by weight. In the same manner, an acrylic polymer (A3) solution having a weight average molecular weight of 700,000 was obtained.

  Next, the pressure-sensitive adhesive composition (c) in which the nonvolatile content of the acrylic polymer (A3) is 30% by mass by mixing the acrylic polymer (A3) solution and ethyl acetate and adjusting the nonvolatile content thereof. Got.

Example 1
What mixed 100 mass parts of said adhesive compositions (a) and 0.08 mass part of isocyanate type crosslinking agent (Nippon Polyurethane Industry Co., Ltd. coronate HX, solid content 75 mass%), and stirred for 15 minutes, It is coated on the surface of a 50 μm-thick polyester film (hereinafter “# 50 release film”) whose one side is peeled off with a silicone compound so that the thickness after drying is 50 μm, and is dried at 75 ° C. for 5 minutes. Thus, an adhesive film was obtained.

  A 38 μm thick polyester film (hereinafter referred to as “# 38 release film”), one side of which was peeled off with a silicone compound, was bonded to the surface of the adhesive film and aged at 23 ° C. for 7 days. A substrateless adhesive film having a fraction of 40% by mass was obtained.

(Example 2)
In the same manner as in Example 1 except that the amount of isocyanate-based crosslinking agent (Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd., solid content: 75% by mass) was changed from 0.08 parts by mass to 0.1 parts by mass. An adhesive film having a thickness of 50 μm and a gel fraction of 50% by mass was obtained.

(Example 3)
An adhesive film having a thickness of 100 μm and a gel fraction of 50% by mass was obtained in the same manner as in Example 2 except that the thickness of the adhesive film was changed from 50 μm to 100 μm.

Example 4
In the same manner as in Example 2, except that 100 parts by mass of the adhesive composition (b) is used instead of 100 parts by mass of the adhesive composition (a), the thickness is 50 μm and the gel fraction is 50% by mass. An adhesive film was obtained.

(Example 5)
In the same manner as in Example 2, except that 100 parts by mass of the pressure-sensitive adhesive composition (c) is used instead of 100 parts by mass of the pressure-sensitive adhesive composition (a), the thickness is 50 μm and the gel fraction is 55% by mass. An adhesive film was obtained.

(Comparative Example 1)
In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet, 81 parts by mass of n-butyl acrylate, 15 parts by mass of methyl methacrylate, 4 parts by mass of acrylic acid, and a polymerization initiator After 0.2 parts by mass of 2,2′-azobisisobutylnitrile was dissolved in 100 parts by mass in ethyl acetate and the inside of the reaction vessel was purged with nitrogen, they were polymerized at 80 ° C. for 8 hours to obtain a weight average molecular weight of 80. Ten thousand acrylic polymer (A4) solutions were obtained.

  Next, the pressure-sensitive adhesive composition (d) in which the acrylic polymer (A4) has a nonvolatile content of 18% by mass by mixing the acrylic polymer (A4) solution and ethyl acetate and adjusting the nonvolatile content thereof. Got.

  Instead of 100 parts by mass of the pressure-sensitive adhesive composition (a), 100 parts by mass of the pressure-sensitive adhesive composition (d) was used, and an epoxy-based crosslinking agent (E-5XM manufactured by Soken Chemical Co., Ltd., solid content: 5 mass) as a crosslinking agent. %), And Example 2 except that 0.33 parts by weight of 0.25 parts by weight of an isocyanate-based crosslinking agent (Coronate L-45 manufactured by Nippon Polyurethane Industry Co., Ltd., solid content: 45% by weight) is used. In the same manner, an adhesive film having a thickness of 50 μm and a gel fraction of 80% by mass was obtained.

  The following evaluation was performed about the adhesive film obtained by the Example and the comparative example.

(Measurement of relative permittivity)
An adhesive film was prepared by removing the # 50 release film and the # 38 release film.

  Next, a tin foil is placed on the surface of the main electrode (circular, diameter φ28 mm), the adhesive film is placed on the surface of the tin foil, an aluminum foil is placed on the surface of the adhesive film, and an anti-electrode is placed on the surface of the aluminum foil To obtain a laminate.

  The laminate was placed on a Precision LCR meter manufactured by Agilent Technologies, and the capacitance of the adhesive film was measured under the conditions of a frequency of 100 kHz by the automatic equilibrium bridge method under the conditions of 23 ° C. and 50% RH. The capacitance was a value of the capacitance of the capacitor when the bridge circuit mounted on the precision LCR meter reached equilibrium and no current passed through the circuit.

Based on the capacitance and the following equation, the relative dielectric constant of the adhesive film was calculated.
ε ′ = Cp · t / ε ₀ · A
ε ′: relative dielectric constant [−]
Cp: Capacitance [pF]
ε ₀ : Dielectric constant of vacuum = 8.854 × 10 ⁻¹² [F / m]
A: Area of main electrode [m ² ]
t: thickness of adhesive film [m]

(Evaluation of step following ability)
A polyethylene terephthalate film having a thickness of 100 μm, a length of 50 mm, and a width of 40 mm, in which a printing layer having a thickness of 15 μm and a width of 5 mm was decorated in a frame shape, was prepared.

  What peeled off the # 38 peeling film of the said adhesive film was bonded together to the surface of the side which has the said printing layer of the said polyethylene terephthalate film.

  Next, the # 50 release film of the pressure-sensitive adhesive film is removed, and a surface made of a polarizing plate constituting a liquid crystal display panel is pasted on the surface, which is left to stand for 20 minutes in an environment of 5 atm and 70 ° C. They were heated and pressurized.

  Next, after being left in a 23 ° C. environment for one day, it was observed using a microscope (magnification 300 times) whether there was any air bubbles at the interface between the polyethylene terephthalate film and the adhesive film. It was evaluated by.

A: There were no bubbles having a diameter of 3 μm or more.
A: There were no bubbles having a diameter of 5 μm or more.
Δ: No bubbles having a diameter of 30 μm or more.
X: There were bubbles having a diameter of 30 μm or more.

Claims (9)

An adhesive film to be attached to a surface made of a non-metallic member constituting the surface of the information display unit, wherein the adhesive film comprises an alkoxyalkyl (meth) acrylate (a1) and a hydroxyalkyl group having 3 or less carbon atoms. It is characterized by being obtained using an acrylic polymer (A) obtained by polymerizing a monomer containing a hydroxyalkyl (a2) having (meth) acrylate and a crosslinking agent (B). Adhesive film. The pressure-sensitive adhesive film according to claim 1, wherein the gel fraction is in the range of 30% by mass to 80% by mass. The pressure-sensitive adhesive film according to claim 1, wherein the nonmetallic member is at least one selected from the group consisting of a polarizing plate, a retardation film, and an antireflection film. The pressure-sensitive adhesive film according to any one of claims 1 to 3, wherein the thickness is in the range of 5 µm to 500 µm. The adhesive film according to any one of claims 1 to 4, having a relative dielectric constant of 4 or more. The information which has the structure which the surface which consists of a nonmetallic member which comprises the surface of an information display part, and the surface protection member were adhere | attached by the adhesive film of any one of Claims 1-5 Display device. The information display device according to claim 6, wherein the non-metallic member includes at least one selected from the group consisting of a polarizing plate, a retardation film, and an antireflection film. The surface of the non-metallic member of the information display unit having a configuration in which a touch panel member is laminated on one side of the liquid crystal display panel, and a non-metallic member including a polarizing plate is laminated on the surface of the touch panel member, and the surface protection An information display device, wherein the member has a structure in which the members are laminated via the adhesive film according to claim 1. The portable electronic terminal carrying the information display apparatus of any one of Claims 6-8.