Adhesive sheet

Abstract

[Problem] This is to provide an adhesive sheet having curved surface followability and chemical resistance. [Means for solving] The adhesive sheet is an adhesive sheet having at least a substrate and an adhesive layer, a load at the time of 5% elongation of the substrate is 15 N/cm or less, a stress relaxation rate of the substrate by elongating to 10%, stopping the elongation at that state and after lapsing 600 seconds is 40% or more and 100% or less, and a chemical weight increased ratio of the substrate is 60% or less.

Claims

1. An adhesive sheet which comprises a substrate and an adhesive layer, wherein the substrate consists of a substrate layer containing a urethane-based polymer and a surface protective layer comprising an acrylic-based resin or a fluorine-based resin as an effective ingredient, the surface protective layer is provided at the outermost surface of the adhesive sheet, the adhesive layer is directly on the substrate layer, and a thickness of the substrate layer is 150 m or more, wherein the urethane-based polymer is a non-yellowing ester-based thermoplastic polyurethane, a load at the time of 5% elongation of the substrate is 15 N/cm or less, a stress relaxation rate of the substrate by elongating to 10%, stopping the elongation at that state and after lapsing 600 seconds is 40% or more and 100% or less, and a chemical weight increased ratio of the substrate is 60% or less.

2. The adhesive sheet according to claim 1, wherein the load at the time of 5% elongation of the substrate is 1 N/cm or more and 15 N/cm or less.

3. The adhesive sheet according to claim 1, wherein a Shore hardness of the substrate layer is 80 A or more and 65 D or less.

4. The adhesive sheet according to claim 1 wherein the acrylic-based resin contains a (meth)acrylic-based polymer having a hydroxyl value of 20 to 120 (KOH mg/g).

5. The adhesive sheet according to claim 1, wherein the adhesive sheet is used as a protective sheet for protecting the surface of an adherend.

6. The adhesive sheet according to claim 1 wherein the fluorine-based resin contains a fluoroethylene vinyl ether alternating copolymer.

7. The adhesive sheet according to claim 1 wherein the acrylic-based resin is a HALS-hybrid (meth)acrylic-based polymer.

8. The adhesive sheet according to claim 1, wherein the substrate layer has a thickness of 150 m to 1 mm.

9. The adhesive sheet according to claim 1, wherein a thickness of the surface protective layer is 2 to 40 m.

10. The adhesive sheet according to claim 1, wherein the surface protective layer is formed by adding a crosslinking agent to a resin for forming the surface protective layer.

11. The adhesive sheet according to claim 10, wherein the crosslinking agent is at least one selected from the group consisting of an isocyanate-based crosslinking agent and an oxazoline-based crosslinking agent.

12. The adhesive sheet according to claim 1, wherein the surface protective layer is formed by coating a coating solution for surface protective layer onto the substrate layer.

Description

EXAMPLES

(1) In the following, the present invention is explained in detail by referring to Examples, but the present invention is not limited by these. Incidentally, in the following Examples, part(s) means part(s) by weight and % means % by weight within the range which does not cause any problems in the common knowledge, otherwise specifically mentioned.

(2) In addition, the measurement method and the evaluation method used in the following Examples are shown below.

(3) (Measurement Method and Evaluation Method)

(4) (1) Evaluation of Flexibility (Measurement of Load at the Time of 5% Elongation)

(5) An acrylic-based adhesive layer with a thickness of 50 m was formed on one of the surfaces of the substrate to prepare an adhesive tape. Provided that in the case of the substrate having a substrate layer and a surface protective layer, the adhesive layer was formed onto the substrate layer. This adhesive tape was cut to a width of 10 mm and a length of 160 mm, and a tensile test was carried out with a tensile rate of 200 mm/min, a distance between chucks of 100 mm at 23 C. to obtain a stress-strain curve. A load at the time of 5% elongation of the adhesive sheet was obtained.

(6) (2) Evaluation of Stress Relaxation Property (Measurement of Stress Relaxation Rate)

(7) An acrylic-based adhesive layer with a thickness of 50 m was formed on one of the surfaces of the substrate to prepare an adhesive sheet. Provided that in the case of the substrate having a substrate layer and a surface protective layer, the adhesive layer was formed onto the substrate layer. This adhesive sheet was cut to a width of 10 mm and a length of 160 mm, and at a tensile rate of 200 mm/min and a distance between chucks of 100 mm at 23 C., it was continued to tension until the distance between chucks became 110 mm and stopped at 10% elongated state. A load (residual stress) after lapsing 600 seconds from the stopping was measured, and a stress relaxation rate was obtained by using the following calculation formula.
Stress relaxation rate (%)={(load at 10% elongationload at 10% elongation after lapsing 600 seconds)/load at 10% elongation}100
(3) Evaluation of Chemical Resistance

(8) As the evaluation of chemical resistance, a weight increased ratio of a fuel such as gasoline, etc., was measured. That is, the substrate was cut to a width of 30 mm and a length of 30 mm to prepare samples for measurement. The sample for measurement was dipped into an organic solvent in which regular gasoline and ethanol had been mixed with a ratio of 90% by weight/10% by weight, and a weight after lapsing 30 minutes was measured. An increased ratio of the weight of chemicals (ex. an organic solvent) was obtained by using the following calculation formula.
Weight increased ratio (%)={(Weight after 30 minutes from dipping into chemicalsWeight before dipping)/Weight before dipping}100

Example 1

(9) A substrate comprising a substrate layer alone was prepared by using, as a substrate layer, a non-yellowing adipate ester-based thermoplastic polyurethane film having a thickness of 240 m and a Shore hardness of 85 A.

(10) With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

Example 2

(11) A substrate comprising a substrate layer alone was prepared by using, as a substrate layer, a non-yellowing caprolactone ester-based thermoplastic polyurethane film having a thickness of 240 m and a Shore hardness of 95 A.

(12) With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

Example 3

(13) A substrate comprising a substrate layer alone was prepared by using, as a substrate layer, a non-yellowing caprolactone ester-based thermoplastic polyurethane film having a thickness of 150 m and a Shore hardness of 97 A.

(14) With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

Comparative Example 1

(15) A substrate comprising a substrate layer alone was prepared by using, as a substrate layer, a non-yellowing carbonate-based thermoplastic polyurethane film having a thickness of 150 m and a Shore hardness of 95 A.

(16) With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

Comparative Example 2

(17) A substrate comprising a substrate layer alone was prepared by using, as a substrate layer, a non-yellowing ether-based thermoplastic polyurethane film having a thickness of 150 m and a Shore hardness of 97 A.

(18) With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

Comparative Example 3

(19) A substrate comprising a substrate layer alone was prepared by using, as a substrate layer, a non-yellowing ether-based thermoplastic polyurethane film having a thickness of 145 m and a Shore hardness of 56 D.

(20) With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

Example 4

(21) A non-yellowing caprolactone ester-based thermoplastic polyurethane film having a thickness of 240 m and a Shore hardness of 95 A used in Example 2 was used as a substrate layer. Onto the film was coated a resin composition for a surface protective layer which had been obtained by mixing 100 parts of a 43% concentration solution of an acrylic-based resin (HALS-hybrid UV-G301, trade name, available from NIPPON SHOKUBAI CO., LTD., a hydroxyl value of the (meth)acrylic-based polymer is 45 (KOH mg/g)) in ethyl acetate and 28.07 parts of isocyanate-based crosslinking agent (Duranate TSE-100, trade name, available from Asahi Kasei Chemicals Corporation) to which 108.8 parts of ethyl acetate as a diluting solvent had been added, so that a thickness after curing became 10 m, and it was dried and cured at a temperature of 120 C. for 2 minutes. The surface protective layer was thus formed onto the substrate layer to form a substrate. With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

Example 5

(22) A non-yellowing caprolactone ester-based thermoplastic polyurethane film having a thickness of 240 m and a Shore hardness of 95 A used in Example 2 was used as a substrate layer. Onto the film was coated a resin composition for a surface protective layer which had been obtained by mixing 100 parts of a 70% concentration solution of an acrylic-based resin (SETALUX D A 870BA, trade name, available from Nuplex Resins GmbH, a hydroxyl value of the (meth)acrylic-based polymer is 99 (KOH mg/g)) in butyl acetate and 34.00 parts of an isocyanate-based crosslinking agent (Sumidur N3300, trade name, available from Sumika Bayer Urethane Ltd.) to which 51.31 parts of a mixed solvent of ethyl acetate and xylene (ethyl acetate/xylene=1/1 wt %) had been added as a diluting solvent, so that a thickness after curing became 10 m, and it was dried and cured at a temperature of 120 C. for 2 minutes. The surface protective layer was thus formed onto the substrate layer to form a substrate. With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

Example 6

(23) A non-yellowing caprolactone ester-based thermoplastic polyurethane film having a thickness of 240 m and a Shore hardness of 95 A used in Example 2 was used as a substrate layer. Onto the film was coated a resin composition for a surface protective layer which had been obtained by mixing 100 parts of a 50% concentration solution of a fluoroethylene/vinyl ether alternating copolymer (LUMIFLON LF600, trade name, available from ASAHI GLASS CO., LTD.) in xylene and toluene and 9.51 parts of an isocyanate-based crosslinking agent (Coronate HX, trade name, available from Nippon Polyurethane Industry Co., Ltd.) to which 76.46 parts of ethyl acetate had been added as a diluting solvent, so that a thickness after curing became 10 m, and it was dried and cured at a temperature of 120 C. for 2 minutes. The surface protective layer was thus formed onto the substrate layer to form a substrate. With regard to the obtained substrate, measurement of the load at the time of 5% elongation, measurement of the stress relaxation rate and evaluation of the chemical resistance were carried out. The results were shown in Table 1.

(24) Also, overall evaluation was carried out with regard to the substrates of Examples 1 to 6 and Comparative examples 1 to 3. That is, when it satisfies all the ranges of the load at the time of 5% elongation of 10 N/10 mm or less, the stress relaxation rate of 40% or more and 100% or less and the chemical weight increased ratio of 60% or less, then, it was designated by the symbol , while it does not satisfy either one of these, then, it was designated by the symbol x.

(25) TABLE-US-00002 TABLE 1 Flexi- bility Stress Chemical Load relaxa- resist- at tion ance Substrate 5% Stress Chemical Substrate layer Surface elonga- relaxa- weight Over- Shore Thick protec- tion tion increased all hard- ness tive (N/10 rate ratio evalu- Material ness (m) layer mm) (%) (%) ation Example Non- 85A 240 None 2.88 49.80 33.23 1 yellowing adipate- based TPU Example Non- 95A 240 None 4.17 56.03 24.07 2 yellowing caprolac- tone ester- based TPU Example Non- 97A 150 None 5.76 70.50 45.10 3 yellowing caprolac- tone ester- based TPU Example Non- 95A 240 Present 7.80 65.56 46.18 4 yellowing caprolac- tone ester- based TPU Example Non- 95A 240 Present 6.68 67.57 58.23 5 yellowing caprolac- tone ester- based TPU Example Non- 95A 240 Present 9.26 71.96 57.77 6 yellowing caprolac- tone ester- based TPU Compara- Non- 95A 150 None 6.57 29.90 13.53 x tive ex- yellowing ample 1 carbonate- based TPU Compara- Non- 97A 150 None 7.10 68.80 72.05 x tive ex- yellowing ample 2 ether-based TPU Compara- Non- 56D 145 None 15.75 74.50 66.44 x tive ex- yellowing ample 3 ether-based TPU

(26) As can be clearly seen from Table 1, it could be understood that the substrates of Example 1 to 6 had a load at the time of 5% elongation of 15 N/cm or less, the stress relaxation rate of 40% or more, and the chemical resistance (the chemical weight increased ratio) of less than 60%.

(27) Adhesive sheets were prepared by using the substrates of Examples 1 to 6.

(28) <<Preparation of Adhesive Layer>>

(29) To a mixture in which 90 parts of isononyl acrylate and 10 parts of acrylic acid had been mixed as monomer components were formulated 0.05 part of Irgacure 651 (trade name, available from Ciba Speciality Chemicals Corporation) and 0.05 part of Irgacure 184 (trade name, available from Ciba Speciality Chemicals Corporation) as photopolymerization initiators, and ultraviolet ray was irradiated until the viscosity became about 25 Pa.Math.s (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 C.) to prepare an acrylic composition (UV syrup) a part of which has been polymerized.

(30) To 100 parts of the obtained UV syrup were added 0.20 part of isononyl acrylate, 0.20 part of trimethylol propane triacrylate and 1 part of a hindered phenol type antioxidant (trade name: Irganox 1010, available from Ciba Speciality Chemicals Corporation) to prepare an adhesive composition.

(31) This adhesive composition was coated, as a temporary support 2, onto a peeling treatment surface of the polyethylene terephthalate film with a thickness of 50 m so that a thickness as the final product became 50 m.

(32) A PET film which had been subjected to peeling treatment was overlapped thereon as a separator and covered, then, ultraviolet ray (illumination: 290 mW/cm.sup.2, light quantity: 4,600 mJ/cm.sup.2) was irradiated to the PET film surface by using a metal halide lamp to cure the same to form an adhesive layer on a temporary support 2. Thereafter, it was dried at 140 C. for 3 minutes to dry the unreacted residual acrylic-based monomer to prepare an adhesive layer.

(33) <<Preparation of Adhesive Sheet>>

(34) The separator was then removed, and adhesive sheets were prepared by using the substrates of Examples 1 to 6.

(35) That is, with regard to the substrates obtained in Examples 1 to 3, an adhesive layer was laminated to one of the surfaces of the substrate so that they were overlapped to prepare an adhesive sheet (a layer constitution is a temporary support 1/a substrate/an adhesive layer/a temporary support 2).

(36) Also, with regard to the substrates obtained in Examples 4 to 6, an adhesive layer was laminated to the opposite side surface (i.e., the substrate layer surface) from the surface protective layer side surface of the substrate so that they were overlapped to prepare an adhesive sheet (a layer constitution is a temporary support 1/a surface protective layer/a substrate layer/an adhesive layer/a temporary support 2).

(37) The respective adhesive sheets obtained by using the substrates of Examples 1 to 6 have been found that each is excellent in curved surface followability and well followed to the portion having a three-dimensionally curved surface, can be neatly adhered without repelling or floating after the adhesion, and excellent chemical resistance can be realized.

(38) That is, according to the present invention, an adhesive sheet excellent in all of flexibility, a stress relaxation rate and chemical resistance could be realized.

UTILIZABILITY IN INDUSTRY

(39) The adhesive sheet of the present invention can be suitably used as an adhesive sheet for protection which is required to have resistance to chemicals such as an organic solvent, etc. Also, the adhesive sheet of the present invention can be suitably used as an adhesive sheet which is further required to have flexibility to a curved surface, etc., in particular, it can be suitably used for an adherend (a material to be adhered) having a severe three-dimensionally curved surface. It can be used as an adhesive sheet for protecting a coating film surface exposed to a harmful environment including, for example, weather outdoors, a solvent, dust, oil and fats, and marine environment, etc., or an adhesive sheet for decoration. In addition, it is also suitable as a chipping tape for protecting a coating film of a body of an automobile, etc., an adhesive sheet for a body protection film or an adhesive sheet.