TW201908443A - Adhesive tape - Google Patents

Abstract

Disclosed is an adhesive tape 11 having an adhesive layer on one side or both sides of a base, wherein the base is a foam, the compression deflection upon adhesion is 0 to -10% at a pressure within the range of 0.3 to 5.0 MPa, and preferably it is an extremely narrow width-adhesive tape 11, so that it shows excellent dimension stability in thickness, and for example, gap G is small in a pressing process such as a process pressing a cover panel onto a body so that decline in product appearance by the gap G is hardly occurred and breakage of product at dropping by the gap G is hardly occurred.

Description

   Adhesive tape   

The present invention relates to an adhesive tape excellent in thickness dimension stability under pressurized conditions, and suitable for use in electronic devices such as smartphones, tablet terminals, car display devices, and TVs.

Portable electronic devices such as smart phones and tablet terminals generally adopt a combination structure composed of a touch panel and a frame housing a liquid crystal module. Moreover, for example, in order to fix the touchpad to the frame, an adhesive tape is used. In addition, it is also used to fix a vehicle display, a TV liquid crystal display (LCD) panel, and an organic EL panel to a housing.

In recent years, these electronic devices are evolving toward thinness and miniaturization. With this development, for example, FPC (Flexible Printed Circuits) is bent inside the machine at a sharper acute angle, resulting in an internal structure to which a strong rebound force is often applied. In addition, in order to increase the LCD display area, the width of the frame (frame) surrounding the liquid crystal panel becomes narrower, that is, the frame becomes narrower. Therefore, the adhesive tape that fixes the frame and the front panel must also be narrowed. However, in order to withstand the rebound force from the internal FPC and the impact from the outside, not only the adhesion strength of the adhesive layer but also the strength of the substrate must be required.

When the narrow-width adhesive tape is adhered to the frame, a pressing machine is generally used to perform the pressing step. At this time, the pressure applied to the adhesive tape covers a wide range of 0.1 MPa to 5.0 MPa. Moreover, when the thickness of the adhesive tape varies greatly within this pressure range, as shown in FIG. 4 (A), there is a gap G between the cover 42 and the frame 43 due to the size change of the double-sided adhesive tape 41 , And reduce the sense of unity, greatly damaging the original appearance of the situation. In addition, when the difference in thickness of the double-sided adhesive tape 41 due to pressure fluctuation is large, it is quite difficult to predict the gap G and design the cover 42 and the frame 43 to increase the difficulty of design. In addition, after the pressing step, as time passes, when the size of the double-sided adhesive tape 41 is restored, as shown in FIG. 4 (B), a cover 42 pops out of the frame 43, causing the cover 42 to suffer when dropped The possibility of damage.

However, the base material of such an adhesive tape generally uses, for example, a polyolefin-based foam containing polyethylene as a main component, and acrylic foam to which various fillers are added to acrylic resin. For example, in the double-sided adhesive tape described in Patent Document 1, an acrylic adhesive layer is designed on both sides of the foam base material. Furthermore, specific examples of the foam base material include polyolefin resin foams such as polyethylene foams and polypropylene foams. The thickness of the foam base material is 50 to 150 μm, and the 30% compression load is 5 to 200 kPa.

The waterproof double-sided adhesive tape described in Patent Document 2 is intended to fix components of a mobile electronic device, and is composed of a polyolefin-based foam base material and an adhesive layer. Moreover, the thickness of the polyolefin-based foam substrate is 70 to 300 μm, the 25% compressive strength is 40 to 160 kPa, the tensile strength is 300 to 1500 N / cm ² , the average bubble diameter in the thickness direction is 1 to 100 μm, and the flow direction The average bubble diameter in the width direction is 1.2 to 700 μm.

The adhesive tape described in Patent Document 3 is provided with an adhesive layer on at least one surface of the foam base material. Furthermore, specific examples of the foam base material include polyolefin-based foam base materials such as polyethylene and polypropylene. The thickness of the foam substrate is 300 μm or less, the interlayer strength system is 6 to 50 N / cm, the 25% compression strength system is 30 kPa or more, the tensile strength system is 300 N / cm ² or more, and the thickness average bubble diameter system is 10 to 100 μm. The average bubble diameter in the direction and width direction is 10 to 700 μm.

The crosslinked polyolefin resin foam sheet described in Patent Document 4 has high impact absorption and antistatic properties. The expansion ratio of the foamed sheet is 1.1 to 2.8 cm ³ / g, the average bubble diameter of the bubble MD is 150 to 250 μm, the average bubble diameter of the CD is 120 to 300 μm, the thickness is 0.02 to 1.9 mm, and the 25% compression strength system 250 ~ 1500kPa.

The adhesive sheet described in Patent Document 5 has less performance degradation due to narrowing. The relationship between the 100% modulus M [N / mm ² substrate] of the adhesive sheet and the foam density D [g / cm ³ ] is 9.0 ≦ (M / D), and the 100% modulus M is higher than 4.0 [ N / mm ² substrate].

Patent Document 6 describes a fixing member (adhesive tape with a foam base material) for fixing a display part or a display part protective material of a mobile electronic device to a housing. The average width W [mm] of the narrow part of the fixing member, the 100% modulus M [N / mm ² base material] of the fixing member, and the thickness Hs [mm] of the foam base material satisfy 0.4 / (M × Hs) ≦ W type.

However, in Patent Documents 1 to 6, the belt thickness variation due to the pressurization step performed by the laminator and the maintenance ratio of the belt thickness after the lamination step have not been fully reviewed. In addition, according to the findings of the present inventors, the conventional physical property evaluation methods described in Patent Documents 1 to 4 do not fully evaluate whether the substrate is suitable for a narrow adhesive tape. For example, the "compressive strength" or "compressive load" described in Patent Documents 1 to 4 are merely an index of hardness in the thickness direction, not an index of thickness change after compression. The "tensile strength", "tensile strength", or "interlayer strength" described in Patent Documents 2 and 3 are only the strengths at the time of base material failure. The "average bubble diameter" or "expansion ratio" described in Patent Documents 3 and 4 are merely indicators of the degree of expansion. The “100% modulus” described in Patent Document 5 represents only the tensile strength of the belt. The expression “0.4 / (M × Hs) ≦ W” described in Patent Document 6 is only a relational expression of tensile strength, tape thickness and tape width.

That is, the conventional physical property evaluation methods described in Patent Documents 1 to 6 may not be directly applicable particularly to very narrow adhesive tapes. On the other hand, according to the findings of the present inventors, when a very narrow adhesive tape is used and the cover plate and the frame are subjected to a pressurization step using a laminator, the compression deformation rate after pressurization becomes an important factor. In terms of the maintenance rate of the deformation rate over time after pressing, and the glass cover and the frame body are not easy to peel off, the high load and low displacement in the load-displacement curve are also important factors.

    [Prior technical literature]         [Patent Literature]    

Patent Document 1: Japanese Patent No. 5947870

Patent Document 2: Japanese Patent No. 4623198

Patent Document 3: Japanese Patent No. 5517015

Patent Literature 4: International Publication No. 2015/046526

Patent Literature 5: Japanese Patent Laid-Open Publication No. 2017-2292

Patent Literature 6: Japanese Patent Laid-Open Publication No. 2017-2293

The present invention has been completed to solve the aforementioned conventional technical problems. That is, an object of the present invention is to provide an adhesive tape, which is preferably a very narrow adhesive tape, and has excellent thickness stability, such as the gap G generated during the pressing step such as the step of pressing the cover plate and the frame body Small, it is not easy to damage the appearance of the product due to the gap G, and the product is not likely to be damaged due to the gap G when the product falls.

The inventors of the present invention have intensively studied in order to achieve the above object, and as a result, it has been found that the use of a substrate with specific physical properties is very effective, and the present invention has been completed.

That is, the adhesive tape of the present invention is an adhesive tape provided with an adhesive layer on one side or both sides of the base material, and is characterized in that the base material-based foam is compressed within the range of 0.3 to 5.0 MPa The compression deformation rate at the time of follow-up is 0 ~ -10%.

In the aforementioned applications, a polyethylene-based foamed substrate containing independent bubbles is generally used. If the high-compressive-strength foamed base material is compared with the low-compressive-strength foamed base material, the deformation of the low-compressive-strength foamed base material due to pressure is large. In addition, even if it is a high-compressive-strength foamed base material, if it is pressurized at a very high pressure of 0.1 to 5.0 MPa, the original thickness still changes greatly due to plastic deformation. On the other hand, the adhesive tape of the present invention is excellent in thickness dimension stability. For example, the gap G generated during the pressing step such as the step of pressing the cover plate and the frame is small, and it is not easy to damage the appearance of the product due to the gap G. Moreover, when the product falls, it is not easy to be damaged due to the gap G. Therefore, it can be effectively used for various applications in fields where such characteristics are required.

11‧‧‧ Base material (or double-sided adhesive tape)

12‧‧‧terminal

31‧‧‧ Double-sided adhesive tape

32‧‧‧SUS304 T-shaped fixture

33‧‧‧glass plate

41‧‧‧ Double-sided adhesive tape

42‧‧‧Cover

43‧‧‧Frame

G‧‧‧Gap

FIG. 1 is a schematic cross-sectional view for explaining the bending moment measuring method of the embodiment.

FIG. 2 is a diagram for explaining the main curve obtained by dynamic viscoelasticity measurement of the embodiment.

FIG. 3 is a schematic cross-sectional view for explaining the load-displacement curve measurement method of the embodiment.

4 (A) and (B) are schematic cross-sectional views for explaining the problem of the gap between the cover and the frame in the conventional technology.

    <Substrate>    

The substrate used in the present invention may be any substrate as long as it has an adhesive tape of the substrate and is compressed within the range of 0.3 to 5.0 MPa, and the compression deformation rate becomes 0 to -10% in the following, and the type is not limited. . For example, a substrate containing an ethylene-vinyl acetate copolymer of 30% by mass or more and having a tensile modulus of elasticity of 30 N / mm ² or more is preferable.

The base material is preferably composed of a polyolefin-based resin composition containing an ethylene-vinyl acetate copolymer and other polyolefin-based resins. Examples of other polyolefin resins include polyethylene resins, polypropylene resins, and mixtures thereof. Extra-fine linear low-density polyethylene (LLDPE) and ethylene propylene rubber (EPDM).

The resin composition system constituting the base material can be produced by a known method. For example, a resin composition containing 30% by mass or more of an ethylene-vinyl acetate copolymer and other polyolefin-based resin is irradiated with an electron beam and crosslinked, and a resin composition constituting a base material can be obtained. Foaming can be performed at the same time or at different times during the crosslinking.

The resin composition constituting the base material may be within the range that does not damage the effects of the present invention, and may contain other additives. Specific examples include, for example, extenders, crosslinking agents, antioxidants, stabilizers, elastomers, and coupling agents. Furthermore, it may contain a light-shielding filler and a pigment. Specific examples of the light-shielding filler include carbon black, nano carbon tube, and black inorganic filler. Specific examples of the pigment include carbon black, aniline black, acetylene black, and graphitized carbon black.

The width of the substrate is preferably 0.4 to 2.0 mm, more preferably 0.45 to 1.5 mm, and particularly preferably 0.6 to 1.2 mm. The thickness of the substrate is preferably 0.05 mm to 1.0 mm, and more preferably 0.05 to 0.4 mm.

The base material is a foam, and the foaming ratio is preferably 1.1 to 3.5 times and more preferably 1.5 to 3.0 times. The bubble shape of the foam is preferably spherical. In addition, from the viewpoint of characteristics such as water resistance, the base material preferably contains independent bubbles. In the present invention, it is preferable that the substrate is managed in such a manner that the pore diameter contained in the substrate is excluded from the size of 0.3 mm to 2.0 mm, and it is more preferred that the substrate is managed in the manner of excluding 0.4 mm to 1.4 mm. In addition, it is preferably a substrate that does not contain pores (bad bubbles) having a size significantly different from the bubble diameter being managed.

    <Adhesive layer>    

The adhesive layer used in the present invention is not particularly limited. As the adhesive composition system that constitutes the adhesive layer, various known adhesive compositions such as acrylic system, rubber system, polysiloxane system, and urethane system can be used. Among them, from the viewpoint of heat resistance, impact resistance, adhesion, and water resistance, an acrylic adhesive composition is preferable, and the adhesive layer preferably contains a (meth) acrylate copolymer.

The constituent components of the acrylic adhesive composition are not particularly limited. The acrylic adhesive composition generally contains an acrylic polymer obtained by using a (meth) acrylic acid alkyl ester having a linear or branched alkyl group as a main component of a monomer. Specific examples of alkyl (meth) acrylates include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, (meth) Group) butyl acrylate, isobutyl (meth) acrylate, second butyl (meth) acrylate, third butyl (meth) acrylate, amyl (meth) acrylate, isoamyl (meth) acrylate Ester, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, (A (Yl) nonyl acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate Alkyl esters, tridecyl (meth) acrylate, myristyl (meth) acrylate, pentadecyl (meth) acrylate, cetyl (meth) acrylate, (meth) (C) Hexadecyl acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, etc.基 ester. Among them, preferred is C2-14 alkyl (meth) acrylate, and more preferred is C2-10 alkyl (meth) acrylate.

The monomer constituting the acrylic polymer preferably uses C1-3 alkyl (meth) acrylate such as methyl acrylate in an appropriate amount. The C1-3 alkyl (meth) acrylate can improve the adhesiveness of the narrow frame, load resistance, processability, and humidity and heat load resistance of the narrow frame. The amount of C1-3 alkyl (meth) acrylate in 100% by mass of the acrylic polymer is preferably 2% by mass or more, and more preferably 3 to 15% by mass. The lower limit value of this range is meaningful from the viewpoints of narrow frame adhesion, load resistance, workability, and narrow frame heat and moisture load resistance. In addition, the upper limit value is meaningful in terms of the initial adhesiveness of the adhesive tape when various evaluations are performed.

For the monomer constituting the acrylic polymer, in order to improve adhesion or cohesion, various copolymerizable monomers such as a polar group-containing monomer, a multifunctional monomer, and the like can also be used. Two or more types of copolymerizable monomers may be used in combination. In addition, a crosslinking agent obtained by reacting with a polar group-containing monomer or a multifunctional group-containing monomer may be blended to form a crosslinked structure. In addition, additives such as silane coupling agent and antioxidant can also be blended.

Specific examples of polar group-containing monomers include, for example, (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and other carboxyl-containing monomers or their anhydrides ( Maleic anhydride, etc.); hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc. hydroxyl-containing monomers such as hydroxyalkyl (meth) acrylate; (Meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide , N-butoxymethyl (meth) acrylamide and other amide group-containing monomers; (meth) acrylic acid aminoethyl, (meth) acrylic acid dimethylaminoethyl, (meth) acrylic acid Amino group-containing monomers such as third butylamino ethyl ester; glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate and other glycidyl monomers; (meth) acrylonitrile Cyanide-containing monomers; N-vinyl-2-pyrrolidone, (meth) acryloyl Porphyrin, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpyridine , N-vinylpyrrole, N-vinylimidazole, N-ethylene Heterocycle-containing vinyl monomers such as azole; alkoxyalkyl (meth) acrylate monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; ethylene sulfonic acid Sulfonic acid group-containing monomers such as sodium; phosphoric acid group-containing monomers such as 2-hydroxyethyl propenyl acetyl phosphate; cyclohexyl maleimide diimide, isopropyl maleimide diimide etc. Amine-based monomer; isocyanate group-containing monomer such as isocyanate-2-methacryloxyethyl ester. Among them, carboxyl group-containing monomers such as acrylic acid and hydroxyl group-containing monomers such as hydroxybutyl acrylate are preferred.

The carboxyl-containing single system can improve the characteristics of narrow frame adhesion, load resistance, processability, and narrow frame moisture and heat resistance. In 100% by mass of the acrylic polymer, the amount of the carboxyl group-containing monomer is preferably 10 to 20% by mass, and more preferably 10 to 12% by mass. The lower limit of these ranges is meaningful in terms of narrow frame adhesion, load resistance, workability, and narrow frame moisture and heat resistance. In addition, the upper limit value is significant from the initial adhesiveness of the adhesive tape when various evaluations are performed.

The hydroxyl-containing single system can improve the characteristics of narrow frame adhesion, load resistance, processability, and narrow frame resistance to moisture and heat. In 100% by mass of the acrylic polymer, the amount of the hydroxyl group-containing monomer is preferably 0.01 to 2.0% by mass, and more preferably 0.05 to 0.15% by mass. The upper limit of these ranges is from the viewpoint of suppressing the change of the adhesive tape with time under heating and humid environment, maintaining sufficient narrow frame adhesion, load resistance, workability, and narrow frame resistance to humidity and heat load. significance.

The thickness of the adhesive layer is preferably 5 to 200 μm, and more preferably 10 to 100 μm.

The adhesive layer can be formed, for example, by subjecting the adhesive composition to a cross-linking reaction. That is, the adhesive composition is coated on the substrate, and the cross-linking reaction is performed by heating to form an adhesive layer on the substrate. Alternatively, the adhesive composition may be coated on a release paper or other film, and a cross-linking reaction may be performed by heating to form an adhesive layer, and then the adhesive layer may be attached to one side or both sides of the substrate. When coating the adhesive composition, a coating device such as a roll coater, die coater, lip coater, etc. can be used. When heating is applied after coating, the solvent in the adhesive composition can also be removed while the crosslinking reaction is performed by heating. In addition, the adhesive layer preferably does not contain an adhesive resin.

    <Adhesive tape>    

The adhesive tape of the invention is provided with an adhesive layer on one side or both sides of the substrate. The adhesive layer may be formed only on one side of the substrate, but it is preferably a double-sided adhesive tape formed on both sides.

When the adhesive tape of the present invention is compressed within the range of 0.3 to 5.0 MPa, the compression deformation rate is 0 to -10%, preferably 0 to -8%. In addition, after the compression is performed in the range of 0.3 to 5.0 MPa, the retention rate of the compression deformation rate during the subsequent period is preferably within ± 3%, and more preferably within ± 2%.

The minimum loss tangent of the adhesive tape of the present invention is preferably in the range of 50-100 ° C, and the difference between the minimum loss tangent and the loss tangent of 150 ° C is preferably 1.5 × 10 ^-1 or less. The minimum loss tangent is in the range of 50 ~ 100 ℃, which is meaningful for dynamic adhesive force and peeling displacement. In addition, the difference between the minimum loss tangent and the loss tangent at 150 ° C is 1.5 × 10 ^-1 or less, which is significant for the compression deformation rate, dynamic adhesive force, and peeling displacement at the time of bonding.

The storage elastic modulus change point α of the adhesive tape of the present invention is preferably above 100 ° C. In addition, in the load-displacement curve when stretching at 1 mm per minute, no interlayer failure occurs in the substrate, the maximum load value is preferably 40 N / cm ² or more, and the peeling displacement is preferably 2.0 mm or less.

When the adhesive tape of the present invention is measured according to the compressive strength measurement of JIS K-7181, the 40% compressive strength is preferably 2 MPa or more, and more preferably 2 to 5 MPa.

The specific measurement conditions for each physical property value described above are as described in the examples described below.

The adhesive tape of the present invention can be pressed at a very high pressure of 0.1 to 5.0 MPa. Especially in terms of its size stability, it is most suitable for narrow width adhesive tapes. Therefore, it can be effectively used for various applications in fields where such characteristics are required. Specifically, it can be used very effectively as a structure followed by an adhesive tape and an electronic device followed by an adhesive tape.

    [Example]    

Hereinafter, the present invention will be described in more detail with examples and comparative examples. In the following description, "parts" means mass parts, and "%" means mass%.

    <Production Examples 1 to 3 of the adhesive layer>    

In a reaction device equipped with a stirrer, thermometer, reflux cooler, and nitrogen introduction tube, fill the components (A1) to (A5), ethyl acetate, and chain transfer agent in the amount (%) shown in Table 1 0.1 parts of lauryl peroxide of dialkyl mercaptan and peroxide-based radical polymerization initiator. Nitrogen was sealed in the reaction apparatus, and the polymerization reaction was carried out at 68 ° C. for 3 hours under a nitrogen flow while stirring, and then at 78 ° C. for 3 hours. Next, it was cooled to room temperature, and ethyl acetate was added. Thus, an acrylic copolymer (A) having a solid content concentration of 30% was obtained.

Table 1 shows the weight average molecular weight (Mw) and theoretical Tg of each acrylic copolymer. This weight-average molecular weight (Mw) is the value of the standard polystyrene-equivalent molecular weight of the acrylic copolymer measured by the GPC method according to the following measuring device and conditions.

‧Apparatus: LC-2000 series (manufactured by JASCO Corporation)

‧Tube: Shodex KF-806M × 2pcs, Shodex KF-802 × 1pcs

‧Eluent: Tetrahydrofuran (THF)

‧Flow rate: 1.0mL / min

‧Column temperature: 40 ℃

‧Injection volume: 100μL

‧Detector: Refractometer (RI)

‧Measurement sample: Dissolve the acrylic polymer in THF to prepare a solution with an acrylic polymer concentration of 0.5% by mass, and filter with a filter to remove impurities.

The theoretical Tg is the value calculated from the FOX formula.

The code names in Table 1 are as follows: "MA": methyl acrylate

"2-EHA": 2-ethylhexyl acrylate

"BA": n-butyl acrylate

"AA": Acrylic

"4-HBA": 4-hydroxybutyl acrylate

"Vac": vinyl acetate

Then, with respect to 100 parts of the solid content of each acrylic copolymer (A), a crosslinking agent (B), an isocyanate crosslinking agent (CORONATE (registered trademark) L-45E, 45% solution manufactured by Tosoh Corporation) was added ) 0.04 parts, 0.1 part of the silane coupling agent (C) made by Shin-Etsu Chemical Co., Ltd., silane coupling agent (trade name KBM-403), and antioxidant (D) made by BASF company (IRGANOX (registered trademark) 1010) Parts, the adhesive composition is prepared by mixing. Secondly, the solvent was removed and dried at 110 ° C, and a cross-linking reaction was carried out. The adhesive composition was coated on the silicone-treated release paper so that the thickness after drying would be 0.075 mm.

    <Example 1>    

First, prepare a base material composed of a polyethylene (PE) foam containing an ethylene-vinyl acetate copolymer [thickness = 0.15 mm, tensile modulus of elasticity = 46.1 N / mm ² , bending moment (MD direction) = 16gf / cm, (TD direction) = 17gf / cm, expansion ratio = 1.9, density = 544kg / m ^3], which is not included voids (bubbles defective) substrate. Then, the substrate was subjected to corona discharge treatment on both sides, and the adhesive layer on the release paper obtained in Production Example 1 was laminated on both sides of the substrate, and cured at 40 ° C for 3 days to obtain a double-sided adhesive tape .

    <Examples 2 and 3>    

A double-sided adhesive tape was obtained in the same manner as in Example 1, except that the adhesive layer was obtained using the adhesive layers obtained in Production Examples 2 and 3.

    <Comparative example 1>    

In addition to the base material, PE foam is used [thickness = 0.2 mm, tensile modulus of elasticity = 21.0 N / mm ² , bending moment (MD direction) = 3 gf / cm, (TD direction) = 4 gf / cm, foam Magnification = 3, density = 330 kg / m ³ ], and the thickness of the adhesive layer after drying became 0.05 mm, and the rest was obtained in the same manner as in Example 1 to obtain a double-sided adhesive tape.

    <Comparative example 2>    

Except for the base material, PE foam is used [thickness = 0.15mm, tensile modulus of elasticity = 23.7N / mm ² , bending moment (MD direction) = 7gf / cm, (TD direction) = 8gf / cm, foam Except for magnification = 1.8 and density = 560 kg / m ³ ], the rest of the adhesive tape was obtained in the same manner as in Example 1.

The tensile modulus of elasticity of the substrate and the bending moment of the substrate and the adhesive tape in Examples and Comparative Examples are values measured according to the following methods. The measured values are shown in Table 2.

    (Tensile elastic modulus)    

The base material was cut into a short sheet shape with a width (W) of 10 mm and a length of 70 mm (the long side was in the MD direction), and it was used as a test piece. Then, the thickness was measured in accordance with a 1/100 scale (N = 5), and the average value at 5 points was regarded as the thickness (t), and the cross-sectional area (S) of the test piece was obtained from the following formula.

Cross-sectional area S (mm ² ) = t × W

t: thickness (mm)

W: width (mm)

According to JIS K7161 2014, the clamp interval (L) of a commercially available tensile test device (manufactured by Toyo Seiki Co., Ltd., device name Strograph V-10C, full width 50N) was set to 20 mm, and the upper and lower ends of the test piece were sandwiched. Then, stretching was performed at a stretching speed of 10 mm / min to obtain a tensile load-displacement curve. From the tensile load of the obtained tensile load-displacement curve with displacements of 0.05 mm and 0.25 mm, a linear formula is obtained. The displacement x (mm) when the tensile load F = 10N is obtained from the obtained linear formula, and then the tensile elastic modulus which is an index of the rigidity of the substrate is obtained from the following formula.

Tensile elastic modulus (N / mm ² ) = (F / S) / (x / L)

F: Tensile load = 10 (N)

S: Cross-sectional area (mm ² )

x: displacement when tensile load = 10N (mm)

L: fixture interval = 20 (mm)

In addition, each linear formula and tensile elastic modulus system are as follows.

Examples 1 to 3: Linear type y = 3.6667x + 0.0767, tensile elastic modulus 46.1N / mm ²

Comparative Example 1: Linear formula y = 1.2632x-0.0432, tensile modulus of elasticity 21.0N / mm ²

Comparative Example 2: Linear formula y = 2.1026x + 0.1349, tensile modulus of elasticity 23.7N / mm ²

    (Bending moment)    

The base material (or double-sided adhesive tape) 11 was cut into a short piece having a width of 38 mm and a length of 50 mm, and used as a test piece. The obtained test piece is sandwiched by four terminals 12 as shown in FIG. 1. Then, according to JIS P8125, it is installed in the part that is operated during the test of a commercially available Taber stiffness tester (manufactured by Toyo Seiki Co., Ltd.), a 10 g hammer is attached to the pendulum, and the bending speed is read at 3 ° / sec , Scale at a bending angle of 15 °, and set it as the measured value. Then, the measured value is substituted into the following calculation formula to calculate the bending moment (M) in the MD direction and the TD direction.

Bending moment (gf / cm) = 38.0nk / w

n: scale read (1 at 10g hammer)

k: torque per scale (gf / cm)

w: width of test piece

    <Evaluation test>    

The double-sided adhesive tapes obtained in Examples and Comparative Examples were evaluated according to the following methods. The results are shown in Tables 3-6.

    (Compression deformation rate afterwards)    

The double-sided adhesive tapes obtained in Examples and Comparative Examples were processed into a square shape of 10 mm × 10 mm, sandwiched from both sides by a white PET film with a thickness of 75 μm, and pressurized by a pressing machine. At this time, pressurization is performed under the conditions that the pressure actually applied to the adhesive tape becomes 0.3 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 4.0 MPa, 5.0 MPa.

After this pressurization, within 5 minutes, the tape cross section was observed using a laser scanning microscope VK-X260 manufactured by KEYENCE, and the thickness was measured. Then, the compression deformation rate at the next time was calculated from the following formula.

(Compression deformation rate at the time) = (Thickness before compression-Thickness after compression) / (Thickness before compression) × 100 [%]

    (The maintenance rate of compression deformation rate at the time)    

The double-sided adhesive tapes after compressive deformation at the time of measurement were stored at 23 ° C. and 50% RH for 24 hours. Then, the belt section was observed using a laser scanning microscope VK-X260 manufactured by KEYENCE, and the thickness was measured. Next, the maintenance rate of the compression deformation rate at the time of adhesion is calculated from the following formula.

(Retention rate of compression deformation rate at the time of next) = (Thickness after 24 hours of storage after pressing-Thickness immediately after pressing) / (Thickness immediately after pressing) × 100 [%]

    (Storage elastic modulus change point α, minimum loss tangent, loss tangent at 150 ℃)    

The double-sided adhesive tapes obtained in the examples and the comparative examples were overlapped to a thickness of 2 mm, a dynamic viscoelasticity measuring device (TA Instruments Japan Co., Ltd., RDA-III) was used, and a parallel plate was used for the jig 8mm, the dynamic viscoelasticity is measured under the conditions of frequency 10Hz, measuring temperature -50 ℃ ~ 150 ℃, heating rate 10 ℃ / min, the main curve shown in Figure 2 is obtained, and the storage elastic modulus change point α and the minimum loss tangent , Loss tangent at 150 ℃.

    (Maximum load and displacement of load-displacement curve)    

The double-sided adhesive tapes obtained in Examples and Comparative Examples were cut to a size of 10 mm × 10 mm, and one of the release papers was torn apart. Then, as shown in FIG. 3, the double-sided adhesive tape 31 was attached to a T-shaped jig 32 made of SUS304, and then another release paper was ripped to be attached to a glass plate 33 having a length of 125 mm, a width of 50 mm, and a thickness of 2.0 mm. Apply pressure at 0.5MPa for 10 seconds, then within 5 minutes, under 23 ℃, 50% RH environment, at a speed of 1mm / min in the upward direction to obtain a load-displacement curve. From the obtained curve, the maximum load and the displacement mm at the time of peeling off from the bonded portion were measured.

    (40% and 50% compression strength)    

The double-sided adhesive tapes obtained in the Examples and Comparative Examples were superimposed to a thickness of 12 mm, a compressive strength measuring device (Shimadzu Corporation, AG-20kNX) was used, and the measurement (analysis) soft system used Trapezium X, measurement mode The system is set to a single condition, and the 0-50% compressive strength is measured according to JIS K-7181, and the main curve is prepared to obtain 40% and 50% compressive strength.

    <Evaluation>    

From the evaluation results of Tables 3 to 5, it is known that the double-sided adhesive tapes of Examples 1 to 3 have no compressive strength of 40% and 50% at all, and all the characteristics are excellent.

The double-sided adhesive tapes of Comparative Examples 1 and 2 have a large compression deformation rate during the subsequent bonding process. Therefore, as shown in FIG. 4 (A), in the pressing step, the thickness of the double-sided adhesive tape 41 changes, resulting in the cover 42 The gap G with the frame 43 becomes larger, the sense of unity is reduced, and the original appearance may be greatly impaired. In addition, in the double-sided adhesive tapes of Comparative Examples 1 and 2, since the compression deformation rate at the time of each pressure under 0.1 MPa to 5.0 MPa is poor, it is difficult to predict the gap G and design the cover 42 and the frame 43.

The double-sided adhesive tape of Comparative Example 1 has a large retention rate of compression deformation rate (the deformation cannot be maintained). Therefore, even if the cover 42 and the frame 43 are designed to predict the gap G, it is still as shown in FIG. 4 (B). There is a possibility that the cover 42 pops out of the frame 43.

In the double-sided adhesive tapes of Comparative Examples 1 and 2, since the storage elastic modulus change point α is below 100 ° C., it is more difficult to predict the gap G and design the cover 42 and the frame 43. In addition, the double-sided adhesive tape of Comparative Example 1 has a tendency to peel off easily due to the tensile force because the maximum load of the load-displacement curve due to the tensile force is low.

    (Industrial availability)    

The adhesive tape of the present invention has no compressive strength of 40% and 50%, and the compressive deformation rate at the time of bonding is small, so that it can be used for various applications in fields where such characteristics are required. Especially suitable for electronic devices such as smart phones and tablet terminals. Specifically, it can be used for fixing the frame and the cover, and fixing the LCD for the vehicle and the frame.

Claims (13)

    An adhesive tape, which is an adhesive tape provided with an adhesive layer on one side or both sides of a substrate, characterized in that the above substrate is a foam, which is compressed when compressed in the range of 0.3 to 5.0 MPa Compression deformation rate is 0 ~ -10%.         For example, the adhesive tape of claim 1, wherein after compression is performed in the range of 0.3 to 5.0 MPa, the maintenance rate of the compression deformation rate during the subsequent period is within ± 3%.     For example, the adhesive tape of claim 1, wherein the minimum loss tangent is within the range of 50 ~ 100 ℃, and the difference between the minimum loss tangent and 150 ℃ loss tangent is 1.5 × 10 ^-1 or less.     The adhesive tape according to claim 1, wherein the storage elastic modulus change point α is above 100 ° C.     As in the adhesive tape of claim 1, in the load-displacement curve when stretched at 1 mm per minute, there is no interlayer failure of the substrate, the maximum load value is 40 N / cm ² or more, and the peeling displacement is 2.0 mm or less .     The adhesive tape according to claim 1, wherein the 40% compressive strength measured according to the compressive strength measurement of JIS K-7181 is 2 MPa or more.         The adhesive tape according to claim 1, wherein the base material is composed of a polyolefin-based resin composition containing an ethylene-vinyl acetate copolymer and other polyolefin-based resin, and its expansion ratio is 1.1 to 3.5 times.         The adhesive tape according to claim 1, wherein the adhesive layer contains a (meth) acrylate copolymer.         The adhesive tape according to claim 1, wherein the adhesive layer does not contain an adhesive resin.     The adhesive tape according to claim 1, wherein the tensile elastic modulus of the base material measured in accordance with JIS K7161 2014 is 30 N / mm ² or more.     As in the adhesive tape of claim 1, wherein the base material contains independent bubbles.         If the adhesive tape of claim 1, its structure is followed by an adhesive tape.         If the adhesive tape of claim 1, it is an electronic device and then the adhesive tape is used.