JP6111789B2 - Double-sided adhesive tape - Google Patents

Description

  The present invention relates to a double-sided pressure-sensitive adhesive tape used for fixing a hard coat film.

  Small electronic terminals such as mobile personal computers, electronic notebooks, and mobile phones are becoming smaller and thinner. In recent years, image display devices such as liquid crystal display devices that are used in such devices are increasingly required to be lighter, thinner, and smaller. ing. In addition, these small electronic terminals are often provided with a transparent film having a hard coat layer in order to prevent the image display device from being damaged or damaged, and in particular, small electronic terminals capable of touch input due to the multi-functionalization of the small electronic terminals. As the number of terminals increases, there is an increasing demand for good damage prevention and damage prevention while being thin.

  As a double-sided pressure-sensitive adhesive tape for fixing a hard coat film and a glass panel used as a display unit of such an image display device, for example, a double-sided pressure-sensitive adhesive tape that realizes high transparency by a specific pressure-sensitive adhesive layer is disclosed. (See Patent Document 1).

  The double-sided pressure-sensitive adhesive tape has a pressure-sensitive adhesive layer on both sides of the base material, and after adjusting the pressure-sensitive adhesive layer having different adhesive strength, the hard coat film and the glass panel need to be reattached and then re-attached. In such a case, re-peeling is possible. However, since it has a base material, there was a problem that transparency was lowered.

JP 2003-238915 A

  The problem to be solved by the present invention is to provide a double-sided pressure-sensitive adhesive tape that can suitably re-peel the hard-coated film and has excellent transparency in a laminate in which a hard-coated film and a glass panel are bonded via an adhesive layer. There is to do.

  Furthermore, it is another object of the present invention to provide a double-sided pressure-sensitive adhesive tape that hardly reduces the surface hardness of the hard coat film even when bonded to the hard coat film.

  In the present invention, the adhesive layer of the double-sided pressure-sensitive adhesive tape consists only of the pressure-sensitive adhesive layer, and the double-sided pressure-sensitive adhesive tape made of two kinds of specific molecular weight acrylic copolymers does not leave a pressure-sensitive adhesive layer on the glass side and is hard-coated. The film can be suitably removed again. Furthermore, it consists of the thickness of a specific adhesive layer, can implement | achieve high hardness and is superior in the high surface hardness of a hard coat film.

  That is, the present invention is a double-sided pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer, for bonding a hard coat layer surface of a hard coat film having a hard coat layer on at least one surface of a transparent resin film substrate and a glass panel surface. An acrylic pressure-sensitive adhesive layer in which the pressure-sensitive adhesive layer contains an acrylic copolymer (A) having a weight average molecular weight of 400,000 or more and an acrylic copolymer (B) having a weight average molecular weight of 100,000 or less. The double-sided adhesive tape which consists of an agent composition is provided.

  The double-sided pressure-sensitive adhesive tape for fixing a hard coat film of the present invention comprises a specific pressure-sensitive adhesive layer, is composed of an acrylic copolymer of a specific molecular weight of a kind, and glass and a hard coat film when bonded under specific conditions By making the adhesive force with respect to the specific range, the adhesive layer is not left on the glass side, and the hard coat film can be suitably peeled off. Furthermore, it consists of the thickness of a specific adhesive layer, can implement | achieve high hardness and is superior in the high surface hardness of a hard coat film.

It is sectional drawing which shows an example of the embodiment of the double-sided adhesive tape of this invention.

  The double-sided pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer, and is bonded to the surface of a hard coat film having a hard coat layer on at least one surface of a transparent resin film substrate and the surface of a glass panel. The acrylic layer is used in combination, and the pressure-sensitive adhesive layer contains an acrylic copolymer (A) having a weight average molecular weight of 400,000 or more and an acrylic copolymer (B) having a weight average molecular weight of 100,000 or less. It is a double-sided adhesive tape which consists of an adhesive composition.

[Acrylic copolymer (A)]
The acrylic copolymer (A) used in the present invention has a weight average molecular weight of 400,000 or more, preferably 600,000 or more. When the weight average molecular weight is in this range, the cohesive force necessary for suppressing the float-off over time can be imparted.

In the present invention, the weight average molecular weight of the acrylic copolymer can be measured by gel permeation chromatography (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 parts 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

  As a monomer component which comprises the acrylic copolymer (A) of this invention, what is generally used for an adhesive use can be used, Especially, a C2-C14 (meth) acrylic acid ester monomer Specifically, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate , Sec-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, isodecyl methacrylate, lauryl methacrylate, etc. It can be used alone or in combination of two or more.

  Among them, a methacrylic acid alkyl ester monomer having an alkyl side chain having 4 to 9 carbon atoms or an acrylic acid alkyl ester monomer having an alkyl side chain having 4 to 9 carbon atoms is preferable, and the carbon number is More preferred are alkyl acrylate monomers having 4 to 9 alkyl side chains. Of these, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferable. By using a (meth) acrylic acid alkyl ester having an alkyl side chain with the carbon number within the above range, high adhesiveness can be imparted to the hard coat film.

  The content of the (meth) acrylic acid ester monomer having 2 to 14 carbon atoms in the acrylic copolymer (A) of the present invention is preferably 80 to 99% by mass, and 85 to 96% by mass. More preferably. By setting the content of the (meth) acrylic acid ester monomer having 2 to 14 carbon atoms in the acrylic copolymer (A) within the above range, high adhesiveness can be imparted to the hard coat film.

  Furthermore, it is preferable to add a vinyl monomer having a functional group such as a hydroxyl group, a carboxyl group, or an amino group in the side chain in a range of 0.01 to 15% by mass in the monomer component constituting the acrylic copolymer. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, crotonic acid, fumaric acid , Carboxypropyl acrylate maleate, dimethylaminoethyl acrylamide, N-vinyl pyrrolidone, acrylonitrile, N-vinyl caprolactam, acrylamide, styrene, vinyl acetate, N-methylol acrylic amide, glycidyl methacrylate, etc. The above can be used in combination.

  Among them, the hydroxyl group-containing vinyl monomer and the carboxyl group-containing vinyl monomer are preferable to use at least one of these vinyl monomers because it is easy to obtain suitable adhesion to the adherend. In particular, a hydroxyl group-containing vinyl monomer can be particularly preferably used when the adherend is easily oxidized or corroded. 2-hydroxyethyl (meth) acrylate can be preferably used as the hydroxyl group-containing vinyl monomer, and acrylic acid can be preferably used as the carboxyl group-containing monomer.

  In the present specification, acrylic acid and methacrylic acid are collectively referred to as (meth) acrylic acid, and these derivatives are also represented in the same manner.

[Acrylic copolymer (B)]
The acrylic copolymer (B) used in the present invention has a weight average molecular weight of 100,000 or less, preferably 50,000 or less. When the weight average molecular weight is in this range, high adhesion can be imparted to the hard coat layer.

  As a monomer component which comprises the acrylic copolymer (B) of this invention, the (meth) acrylic acid ester which has a C1-C4 alkyl group is preferable. Examples of the (meth) acrylic acid ester having an alkyl group having 1 to 4 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl. It is mentioned by (meth) acrylate etc., and can be used individually or in combination of 2 or more types.

  Among these, a methacrylic acid alkyl ester monomer having an alkyl side chain having 1 to 4 carbon atoms is preferable. Of these, methyl methacrylate is particularly preferable. By using a methacrylic acid alkyl ester having an alkyl side chain having a carbon number within the above range, high adhesiveness can be imparted to the hard coat layer.

  The content of the (meth) acrylic acid ester monomer having 1 to 4 carbon atoms in the acrylic copolymer (B) of the present invention is preferably 80 to 99% by mass, and 85 to 96% by mass. More preferably. By making the content of the (meth) acrylic acid ester monomer having 1 to 4 carbon atoms in the acrylic copolymer (B) within the above range, high adhesiveness can be imparted to the hard coat layer.

  Furthermore, it is preferable to add a vinyl monomer having a functional group such as a hydroxyl group, a carboxyl group, or an amino group in the side chain in a range of 0.01 to 15% by mass in the monomer component constituting the acrylic copolymer. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, crotonic acid, fumaric acid , Carboxypropyl acrylate, maleic anhydride, dimethylaminoethylacrylamide, N-vinylpyrrolidone, acrylonitrile, N-vinylcaprolactam, acrylamide, dimethylaminoethyl (meth) acrylate, styrene, vinyl acetate, N-methylol acrylamide, glycidyl methacrylate, etc. Yes, these can be used alone or in combination of two or more.

  Among these, an amino group-containing vinyl monomer is preferable because it is compatible with the acrylic copolymer (A) and can impart excellent optical properties. As the amino group-containing vinyl monomer, dimethylaminoethyl (meth) acrylate can be preferably used.

[Adhesive composition]
The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention has the acrylic copolymer (A) and the acrylic copolymer (B), and the acrylic copolymer in the pressure-sensitive adhesive composition. Content of an acrylic copolymer (B) is 5-30 mass parts with respect to 100 mass parts of polymers (A), 5-20 mass parts is preferable, and 7-15 mass parts is more preferable. By blending the copolymers (A) and (B) within the above range, both high adhesion to the hard coat layer and low adhesion to glass can be achieved, and the copolymers (A) and (B). Are easily compatible with each other and can impart high optical properties.

  In the said adhesive composition, in order to raise the cohesion force of an adhesive layer as components other than the said copolymer (A) and (B), it is preferable to contain a crosslinking agent.

  Examples of the crosslinking agent used include isocyanate crosslinking agents, epoxy crosslinking agents, chelating crosslinking agents, azirine crosslinking agents, and polyfunctional acrylates. Among them, an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent that is highly reactive with the component (A) of the (meth) acrylic copolymer is preferable.

  0.01-2 mass parts is preferable, as for the compounding quantity of the crosslinking agent added to the adhesive layer of the said double-sided adhesive sheet, 0.03-1 mass part is more preferable, and 0.03-0.3 mass part is further. preferable. By setting it as content of the said range, it is easy to adjust the gel fraction of an adhesive layer to a suitable range.

  The glass transition temperature of the pressure-sensitive adhesive composition of the double-sided pressure-sensitive adhesive tape of the present invention is preferably −25 to 10 ° C., more preferably −20 to 0 ° C. By being the glass transition temperature within the above range, a high elastic modulus can be imparted to the pressure-sensitive adhesive layer, and a high scratch resistance can be imparted to the hard coat film.

  In the present invention, the glass transition temperature of the pressure-sensitive adhesive composition is measured using a viscoelasticity tester (manufactured by Rheometrics, trade name: Ares 2KSTD) between parallel disks that are measuring units of the tester. The temperature at which the loss tangent (Tanδ) that can be calculated by measuring the storage elastic modulus (G ′) and loss elastic modulus (G ″) at a frequency of 1 Hz is maximized. The adhesive of 5 to 2.5 mm may be sandwiched between the parallel disks alone, but the laminate of the base material and the adhesive may be stacked in layers and sandwiched between the parallel disks. Is adjusted so that the thickness of the pressure-sensitive adhesive alone is in the above range.

[Double-sided adhesive tape]
The double-sided pressure-sensitive adhesive tape of the present invention comprises a pressure-sensitive adhesive layer comprising the above-mentioned pressure-sensitive adhesive composition, and includes a hard coat layer surface of a hard coat film having a hard coat layer on at least one surface of a transparent resin film substrate, and a glass panel surface. By being used for pasting, it is possible to suitably adhere to the hard coat layer and to achieve both low adhesion to glass and to realize suitable removability.

  The pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape for fixing a hard coat film of the present invention is a pressure-sensitive adhesive tape formed by providing a pressure-sensitive adhesive layer with a thickness of 15 μm on a PET substrate having a thickness of 25 μm, and a relative temperature of 23 ° C. Peeling speed of 300 mm / min after glass plate is pressed in one reciprocation using a 2 kg roller in a 50% humidity RH environment and left in an environment of 85 ° C. and 5 atm for 60 minutes. A pressure-sensitive adhesive tape formed by providing a pressure-sensitive adhesive layer having a thickness of 15 μm on a PET substrate having a thickness of 25 μm, and a pressure-sensitive adhesive layer having a 180 ° peel adhesive strength P0 of 5 to 12 N / 25 mm Is bonded to the hard coat layer of the hard coat film by a single reciprocation using a 2 kg roller in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH. 6 It is preferable that the ratio (P1 / P0) of 180 ° peel adhesive strength P1 and P0 at a peeling speed of 300 mm / min after standing for 0 minutes is 1.3 or more. Due to the adhesive strength within the above range, the adhesive layer of the double-sided pressure-sensitive adhesive tape can be suitably peeled off without remaining on the glass in a poorly bonded product in the manufacturing process, and the glass panel is not washed again. Be available.

In the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention, the gel fraction represented by the following formula when immersed in toluene for 24 hours is preferably 40 to 90%, and preferably 50 to 80%. More preferably, 60 to 80% is most preferable. When the gel fraction of the pressure-sensitive adhesive layer is within the above range, both low adhesion to glass and suppression of peeling over time can be achieved.
Gel fraction (%) = [(mass after dipping toluene in double-sided pressure-sensitive adhesive tape) / (mass before dipping toluene in double-sided pressure-sensitive adhesive tape)] × 100

  The double-sided pressure-sensitive adhesive tape of the present invention preferably has a total light transmittance of 90% or more and a haze of less than 1.0% in the visible light wavelength region so as not to disturb the transparency of the hard coat film. If it is within the above range, the high-definition of the display equipped with the touch panel device using the double-sided pressure-sensitive adhesive tape is easily maintained. In order to make the total light transmittance and haze within the above ranges, it is easy to achieve by setting the amount of the copolymer (B) to 5 to 30% by mass with respect to 100% by mass of the copolymer (A). .

  The water absorption of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape of the present invention is preferably 2.0% or less after standing at 60 ° C. and 90% RH. By controlling the water absorption rate of the double-sided pressure-sensitive adhesive tape within the above range, the double-sided pressure-sensitive adhesive tape can be kept transparent even under high temperature and high humidity conditions.

  After the double-sided pressure-sensitive adhesive tape of the present invention is bonded to the indium tin oxide film in a reciprocating manner one time using a 2 kg roller in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH, and left still for 1 hour. The 180 ° peel adhesive strength at 300 mm / min is preferably 5 to 15 N / 20 mm for the indium tin oxide film. Within the above range, it is easy to suppress peeling from the end face in fixing the transparent conductive film, and the double-sided adhesive tape can be peeled off in a poorly bonded product in the manufacturing process.

  The thickness of the double-sided pressure-sensitive adhesive tape of the present invention may be appropriately selected depending on the mode of use, but is preferably 5 to 25 μm, more preferably 10 to 20 μm. When the thickness is within the above range, both high pencil hardness can be imparted to the glass panel to which the hard coat film is attached and the followability to the printed portion applied to the hard coat film can be achieved.

  The double-sided pressure-sensitive adhesive tape of the present invention can be prepared by a generally used method. For example, it can be produced by forming an adhesive layer on a film substrate or a release sheet. Specifically, the adhesive composition is directly applied to the base film and dried or cured / polymerized, or once applied on the release sheet and dried / cured / polymerized to form an adhesive layer. Similarly, it can be produced by a method of bonding to an adhesive layer or a base film prepared on a release sheet.

  It is preferable that the pressure-sensitive adhesive layer does not adhere to the end face of the release film after the punching process of the double-sided pressure-sensitive adhesive tape of the present invention. If the pressure-sensitive adhesive layer does not adhere to the end face of the release film, the yield during processing tends to be improved.

  In order to prevent adhesion of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape to the end face of the release film, it is easy to achieve by adjusting the cohesive force, adhesiveness, etc. of the pressure-sensitive adhesive layer to the optimum range. Specific examples of the method include use of a carboxyl group-containing monomer in the pressure-sensitive adhesive layer, adjustment of the gel fraction of the pressure-sensitive adhesive layer to the above range, and the like. Especially, it is preferable to use a carboxyl group-containing monomer for the pressure-sensitive adhesive layer that can easily provide cohesive force necessary for punching and adhesion necessary for fixing the transparent conductive film.

[Specification form]
The double-sided pressure-sensitive adhesive tape of the present invention can be suitably used when the hard coat layer surface of a hard coat film having a hard coat layer on at least one of the transparent resin base materials is fixed to the entire glass panel. For example, as shown in FIG. 1, using the double-sided pressure-sensitive adhesive tape 1 of the present invention, a hard coat layer having hard coat layers 3 and 4 on both sides of a polyethylene terephthalate base 2 and printing 5 on one side thereof. It can use suitably for the aspect etc. which fix a film and the glass panel 6.

  The transparent resin substrate preferably has a hard coat on at least one of the substrates and a hard coat layer on both sides. By having a hard coat layer, it is possible to impart high hardness and scratch resistance to the substrate.

  Although the thickness of the said hard-coat layer is not specifically limited, 3-50 micrometers is preferable, 5-30 micrometers is more preferable, 7-15 micrometers is further more preferable. When the thickness is within the above range, it is possible to impart high scratch resistance, a thin image display device, and high punchability.

  Although it does not specifically limit as resin which forms the said hard-coat layer, Active energy curable resin which has a urethane bond is mentioned.

  The contact angle of pure water on the surface of the hard coat layer is preferably 60 to 90 °, more preferably 65 to 85 °. When the contact angle is within the above range, the printing ink and the double-sided pressure-sensitive adhesive tape are easily adhered to the hard coat layer surface.

  The transparent resin substrate is not particularly limited. For example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride. Film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyetheretherketone film, polyethersulfone film, polyetherimide film, Polyimide film, fluorine resin film, nylon film, acrylic tree Mention may be made of the film, and the like. Among these, polyethylene terephthalate having excellent durability and transparency is preferable.

  Although the thickness of the said transparent resin base material is not specifically limited, 50-250 micrometers is preferable, 75-188 micrometers is more preferable, 75-125 micrometers is especially preferable. When the thickness is within the above range, the image display device can be both thinned and highly scratch resistant.

  The glass panel is preferably a transparent panel made of tempered glass. Examples of the tempered glass include tempered glass manufactured by HOYA, Gorilla glass manufactured by Corning, and IG3 manufactured by Ishizuka Glass. Examples of a method for strengthening the glass panel include a physical strengthening method and a chemical strengthening method. In particular, chemical strengthening methods include an ion exchange method and an air cooling strengthening method. Examples of the material of the glass panel include float glass, alkali glass, and alkali-free glass.

  The glass panel may be a glass panel for a touch panel having a conductive layer on at least one side.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.
<Acrylic copolymer (1)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 94 parts by mass of n-butyl acrylate, 6 parts by mass of acrylic acid and 2,2 as a polymerization initiator '-Azobisisobutylnitrile (0.2 part) was dissolved in 100 parts by mass of ethyl acetate, purged with nitrogen, and then polymerized at 80 ° C for 8 hours to obtain an acrylic copolymer (1) having a weight average molecular weight of 750,000.

<Acrylic copolymer (2)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 89.5 parts by mass of n-butyl acrylate, 10 parts by mass of acrylic acid, 0. 5 parts by mass and 0.2 part of 2,2′-azobisisobutylnitrile as a polymerization initiator are dissolved in 100 parts by mass of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain a weight average molecular weight of 750,000. An acrylic copolymer (2) was obtained.

<Acrylic copolymer (3)>
An acrylic copolymer (C) having a weight average molecular weight of 750,000 was obtained in the same manner as the acrylic copolymer (2) except that 84.5 parts by mass of n-butyl acrylate and 15 parts by mass of acrylic acid were used. .

<Acrylic copolymer (4)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 95.0 parts by weight of methyl methacrylate, 5.0 parts by weight of dimethylaminoethyl methacrylate and a polymerization initiator As follows, 1.0 part by mass of 2,2′-azobisisobutylnitrile is dissolved in 100 parts by mass of ethyl acetate, substituted with nitrogen, polymerized at 80 ° C. for 8 hours, and a methacrylic copolymer having a weight average molecular weight of 20,000 (4 )

<Acrylic copolymer (5)>
An acrylic copolymer (F) having a weight average molecular weight of 6,000 was obtained in the same manner as the acrylic copolymer (4) except that the amount of 2,2′-azobisisobutylnitrile was changed to 3.0 parts by mass.

<Adhesive A>
10 parts by mass of the acrylic copolymer (4) was added to 100 parts by mass of the acrylic copolymer (1), and diluted with ethyl acetate to obtain a pressure-sensitive adhesive A having a resin solid content of 30%.

<Adhesive B>
20 parts by mass of the acrylic copolymer (4) was added to 100 parts by mass of the acrylic copolymer (1), and diluted with ethyl acetate to obtain an adhesive B having a resin solid content of 30%.

<Adhesive C>
10 parts by mass of the acrylic copolymer (5) was added to 100 parts by mass of the acrylic copolymer (1), and diluted with ethyl acetate to obtain an adhesive C having a resin solid content of 30%.

<Adhesive D>
20 parts by mass of the acrylic copolymer (5) was added to 100 parts by mass of the acrylic copolymer (1), and diluted with ethyl acetate to obtain an adhesive D having a resin solid content of 30%.

<Adhesive E>
10 parts by mass of the acrylic copolymer (4) was added to 100 parts by mass of the acrylic copolymer (2), and diluted with ethyl acetate to obtain an adhesive E having a resin solid content of 30%.

<Adhesive F>
10 parts by mass of the acrylic copolymer (4) was added to 100 parts by mass of the acrylic copolymer (4), and diluted with ethyl acetate to obtain an adhesive E having a resin solid content of 30%.

<Adhesive G>
100 parts by mass of the acrylic copolymer (1) was diluted with ethyl acetate to obtain an adhesive H having a resin solid content of 30%.

<Adhesive H>
100 parts by mass of the acrylic copolymer (3) was diluted with ethyl acetate to obtain an adhesive H having a resin solid content of 30%.

The compounds abbreviated in Table 1 are as follows.
BA: n-butyl acrylate AA: Acrylic acid HEA: Hydroxyethyl acrylate MMA: Methyl methacrylate DM: Dimethylaminoethyl methacrylate

Example 1
0.75 parts by mass of an epoxy-based cross-linking agent (E-AX manufactured by Soken Chemical Co., Ltd., 5% solid content) was added to 100 parts by mass of the pressure-sensitive adhesive A, and the mixture was stirred for 15 minutes. It was coated on a polyester film (hereinafter referred to as # 75 release film) so that the thickness after drying was 15 μm, and dried at 85 ° C. for 4 minutes. The obtained pressure-sensitive adhesive sheet and a 38 μm-thick polyester film (hereinafter referred to as # 38 release film) having one surface peel-treated with a silicone compound were bonded together. Thereafter, it was aged at 23 ° C. for 7 days to obtain a base-less pressure-sensitive adhesive tape having a gel fraction of 70% and a thickness of 15 μm.

(Example 2)
An adhesive tape having a gel fraction of 68% was obtained in the same manner as in Example 1 except that the adhesive A was changed to the adhesive B.

(Example 3)
An adhesive tape having a gel fraction of 70% was obtained in the same manner as in Example 1 except that the adhesive A was changed to the adhesive C.

Example 4
An adhesive tape with a gel fraction of 68% was obtained in the same manner as in Example 1 except that the adhesive A was changed to the adhesive D.

(Example 5)
An adhesive tape having a gel fraction of 70% was obtained in the same manner as in Example 1 except that the adhesive A was changed to the adhesive E.

(Example 6)
An adhesive tape with a gel fraction of 68% was obtained in the same manner as in Example 1 except that the adhesive A was changed to the adhesive F.

(Example 7)
An adhesive tape having a gel fraction of 70% was obtained in the same manner as in Example 1 except that the thickness was changed from 15 μm to 25 μm.

(Comparative Example 1)
An adhesive tape having a gel fraction of 72% was obtained in the same manner as in Example 1 except that the adhesive A was changed to the adhesive G.

(Comparative Example 2)
An adhesive tape having a gel fraction of 72% was obtained in the same manner as in Example 1 except that the adhesive A was changed to the adhesive H.

  The following evaluation was performed about the adhesive tape obtained in the said Example and comparative example. The results obtained are shown in the table below.

(Adhesive strength)
One side of the double-sided adhesive tape is bonded to a PET substrate with a thickness of 25 μm, and a test sample cut to a width of 25 mm is applied to a hard coat film substrate or a glass panel, and a round trip is performed once using a 2 kg roller. The adhesive force was measured after peeling off in the 180 ° direction at a peeling speed of 300 mm / min after leaving at 60 ° C. for 5 minutes in an environment of 85 ° C. and 5 atm.

(Removability)
A test sample obtained by bonding a double-sided adhesive tape to one side of a base material having a hard coat layer having a thickness of 10 μm and a pure water contact angle of 75 ° on both sides of PET having a thickness of 100 μm and cutting to a width of 25 mm. Affixed to glass and crimped once with a 2 kg roller, and allowed to stand in an environment of 85 ° C. and 5 atm for 60 minutes, then left at 23 ° C. for 1 hour. The film was peeled in the direction of ° and the removability was evaluated.
○: The pressure-sensitive adhesive layer does not remain on the glass side, and the substrate can be peeled off without breaking.
(Triangle | delta): Although an adhesive layer does not remain on the glass side, a base material is cut off.
X: The pressure-sensitive adhesive layer remains on the glass side.

(transparency)
A test sample was prepared by laminating a PET substrate having a 10 μm thick hard coat layer on both sides with a double-sided adhesive tape and glass. Using the “HR-100 type” manufactured by Murakami Color Research Laboratory Co., Ltd., the total light transmittance and haze (%) of the adjusted sample were measured, and the transparency was evaluated.
○: Total light transmittance 90% or more, haze less than 1% ×: Total light transmittance less than 90%, haze 1% or more

(Pencil hardness)
The surface pencil hardness of a test sample prepared by laminating a double-sided pressure-sensitive adhesive tape on both sides of a PET base material having a 10 μm thick hard coat layer and glass in this order is based on the provisions of JIS K 5600-5-4 (1999 edition). The pencil hardness was evaluated using a pencil scratch tester (manual type) for coating film manufactured by Imoto Seisakusho Co., Ltd.
(Double-circle): There is no fall by the same hardness as a PET base material which has a hard-coat layer on both surfaces.
○: One rank lower than the PET base material having the hard coat layer on both sides.
(Triangle | delta): Two ranks lower than PET base material which has a hard-coat layer on both surfaces.
X: 3 rank lower than PET base material which has a hard-coat layer on both surfaces.

  As shown in Table 3, the double-sided pressure-sensitive adhesive tapes of Examples 1 to 7 have an adhesive strength to the hard coat layer of 1.3 times or more of the adhesive strength to glass and an adhesive strength to glass of 12 N / 25 mm or less. It was confirmed that the pressure-sensitive adhesive layer did not remain on the glass side or that the substrate could be re-peeled without breaking. On the other hand, in Comparative Example 1 or 2 that does not contain the acrylic copolymer (2) having a weight average molecular weight of 100,000 or less, the adhesive force to the base material having the hard coat layer is low, and the pressure-sensitive adhesive layer is placed on the glass side during re-peeling. Was confirmed to remain. In Comparative Example 3 in which 30 parts by mass of the acrylic copolymer (5) having a weight average molecular weight of 20,000 is blended, the adhesive strength to the glass side is high, and the substrate having the hard coat layer is peeled off at the time of re-peeling, or It was confirmed that transparency was also lowered.

1 Double-sided adhesive tape 2 Polyethylene terephthalate base material 3, 4 Hard coat layer 5 Printing layer 6 Glass panel

Claims (8)

A double-sided adhesive tape comprising an adhesive layer,
Used to bond the hard coat layer surface of the hard coat film having a hard coat layer on at least one surface of the transparent resin film substrate, and the glass panel surface,
An acrylic pressure-sensitive adhesive composition in which the pressure-sensitive adhesive layer contains an acrylic copolymer (A) having a weight average molecular weight of 400,000 or more and an acrylic copolymer (B) having a weight average molecular weight of 100,000 or less. Tona is, is said acrylic copolymer of the acrylic pressure-sensitive adhesive composition (a) above with pairs 100 parts by mass of the acrylic copolymer content of (B) is 5 to 30 parts by weight, the double-sided adhesive tape monomer components constituting the acrylic copolymer polymer (B) is characterized by an amino group-containing vinyl monomer der Rukoto. The pressure-sensitive adhesive layer is a 25-μm-thick PET substrate formed by providing a pressure-sensitive adhesive layer with a thickness of 15 μm and a 2 kg roller against a glass panel in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH. The 180 ° peel adhesive strength P0 at a peeling speed of 300 mm / min after leaving for 60 minutes in an environment of 85 ° C. and 5 atm is 5 to 12 N / 25 mm. ,
In addition, an adhesive tape formed by providing an adhesive layer with a thickness of 15 μm on a PET substrate with a thickness of 25 μm is a hard coat layer of the hard coat film in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH. Using a 2 kg roller, the pressure is bonded in one reciprocation, and the 180 ° peel adhesive force P1 at a peeling speed of 300 mm / min after standing for 60 minutes in an environment of a temperature of 85 ° C. and 5 atm, and the above P0 The pressure-sensitive adhesive tape according to claim 1, wherein the ratio (P1 / P0) is 1.3 or more.   The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein the monomer component constituting the acrylic copolymer (B) is a (meth) acrylic acid ester having an alkyl group having 1 to 4 carbon atoms.   The content of the (meth) acrylic acid ester having an alkyl group having 1 to 4 carbon atoms in the monomer component constituting the acrylic copolymer (B) is 80 to 99% by mass. Double-sided adhesive tape.   The double-sided pressure-sensitive adhesive tape according to claim 3 or 4, wherein the (meth) acrylic acid ester monomer having 1 to 4 carbon atoms is methyl methacrylate.   The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 5, having a thickness of 5 to 25 µm.   The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 6, wherein a total light transmittance in a visible light wavelength region is 90% or more and a haze is less than 1.0%. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 7, wherein the hard coat film has hard coat layers on both sides of a transparent resin film substrate.

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