Double-sided coated tape

Abstract

An object of the present invention is to provide a double-sided coated tape that has sufficient adhesive performance, is thin and easy to handle, and does not undergo thermal shrinkage, and is particularly suitable for the manufacture of electronic devices. The double-sided coated tape of the present invention has a core layer and first and second pressure-sensitive adhesive layers disposed on first and second major surfaces of the core layer, respectively, and the double-sided coated tape has an overall thickness of 50 μm or less. The core layer includes a urethane resin and at least one of an additive and a curing agent, and has a glass transition temperature of 0°C or lower and a Young's modulus in the range of 15 MPa to 1200 MPa. The double-sided coated tape of the present invention has a breaking elongation of 150% or less.

Description

[0001] DOUBLE-SIDED COATED TAPE

[0002] Technical Field

[0003] The present invention relates to a double-sided coated tape that is thinner than conventional products and is useful in the manufacture of electronic devices.

[0004] Conventional Technology

[0005] In the manufacture of electronic devices, double-sided coated tape (sometimes simply referred to herein as "tape" in the present specification) having a pressure-sensitive adhesive (pressure-sensitive adhesive) coating on both sides is widely used to bond components together. Typically, the pressure-sensitive adhesive surface of the doublesided coated tape is covered with a separator (liner) and is pre-die or kiss cut to the desired shape. When joining components, the separator is peeled off, and during this process, the pressure-sensitive adhesive on the surface of the tape may separate irregularly from the main body of the tape. To prevent such separation, double-sided coated tape typically includes a core layer to support the pressure -sensitive adhesive.

[0006] An example of the material used for the core layer of a typical double-sided coated tape is polyester. However, polyester undergoes thermal shrinkage, making polyester unsuitable for use in tapes used in the manufacture of electronic devices that undergo a reflow process. Therefore, conventionally, tissue made of cellulose, which does not undergo thermal shrinkage, has been used as the core layer of tape used in the manufacture of electronic devices.

[0007] As electronic devices evolve, they are always required to become smaller and thinner, and this in turn requires that the tape used in their manufacture also becomes thinner. Recently, there has been a demand for tapes with a thickness of 50 pm or less. However, when trying to reduce thickness of a double-sided coated tape that uses conventional cellulose tissue for the core layer, the adhesive performance can decrease due to the non-uniformity of the core layer, and reducing thickness of the core layer can make it difficult to produce the tape itself. In addition, when the thickness of the core layer is reduced as much as possible, the strength for supporting the pressure-sensitive adhesive is reduced, and the pressure-sensitive adhesive tends to separate irregularly from the tape when the separator is peeled off, which tends to reduce the handleability of the tape. Therefore, a new material must be found for the core layer that would overcome these problems and enable the thickness of tape to be reduced.

[0008] Patent Document 1 describes a resin sheet for laminating rigid flat plates, which comprises at least three resin layers, and proposes using a urethane -modified polyester resin for the resin layer that is not in contact with the adherend. However, such resins are likely to undergo thermal shrinkage and cannot be used in tape used in the manufacture of electronic devices that undergo a reflow process.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Unexamined Patent Application Publication 2013- 146945

[0012] Summary of the Invention

[0013] An object of the present invention is to provide a double-sided coated tape that has sufficient adhesive performance, is thin and easy to handle, and does not undergo thermal shrinkage, and is particularly suitable for the manufacture of electronic devices.

[0014] The present inventors have found that the above problems can be resolved by providing a double-sided coated tape having a core layer and two pressure-sensitive adhesive layers respectively disposed on both major surfaces of the core layer, where the core layer is formed from a material containing a urethane resin and at least one of an additive and a curing agent, and is configured to have a glass transition temperature of 0°C or lower, a Young's modulus in the range of 15 MPa to 1200 MPa, and a breaking elongation of 150% or less. A summary of the present invention is as follows.

[0015] (1) A double-sided coated tape, comprising: a core layer having a first major surface and a second major surface opposite the first major surface; a first pressure-sensitive adhesive layer disposed on a first major surface of the core layer; and a second pressure-sensitive adhesive layer disposed on a second major surface of the core layer; wherein the double-sided coated tape has a total thickness of 50 pm or less; the core layer contains urethane resin, and at least one of an additive or a curing agent, the core layer has a glass transition temperature of 0°C or lower and a Young's modulus in the range of 15 MPa to 1200 MPa; and the double-sided coated tape has a breaking elongation of 150% or less.

[0016] (2) The double-sided coated tape according to item (1), wherein the thickness of the core layer is in the range of 1 pm to 10 pm.

[0017] (3) The double-sided coated tape according to item (1) or (2), wherein the ratio of the total thickness of the double-sided coated tape to the thickness of the core layer is in the range of 1:2 to 1:50.

[0018] (4) The double-sided coated tape according to any one of items (1) to (3), wherein the core layer includes a pigment as the additive.

[0019] (5) The double-sided coated tape according to item (4), wherein the content of the pigment is 1 mass% to 80 mass% based on the total mass of the core layer.

[0020] (6) The double-sided coated tape according to any one of items (1) to (5), wherein the core layer includes a polyfunctional isocyanate compound as a curing agent.

[0021] (7) The double-sided coated tape according to any one of items (1) to (6), which has a thermal shrinkage rate of 0.1% or less when heated at 250°C for 8 minutes.

[0022] According to the double-sided coated tape of the present invention, a urethane resin-based material is used for the core layer instead of the conventional cellulose tissue, so even when the core layer is made thin, the layer is less likely to become uneven and problems with adhesive performance are less likely to occur. Furthermore, by adjusting the physical properties of the core layer so that the Young's modulus of the core layer and the breaking elongation of the double-sided coated tape are within prescribed ranges, good handleability of the double-sided coated tape can be ensured. Furthermore, by setting the glass transition temperature of the core layer to 0°C or lower, the problem of heat shrinkage does not occur. In addition, since the materials for the core layer are all inexpensive, the double-sided coated tape of the present invention is also advantageous in terms of manufacturing cost.

[0023] Brief Description of the Drawings

[0024] FIG. 1 is a cross-sectional view depicting an outline of a double-sided coated tape according to an embodiment of the present invention. Embodiments of the Invention

[0025] (double-sided coated tape)

[0026] FIG. 1 is a cross-sectional view depicting an outline of a double-sided coated tape according to an embodiment of the present invention. A double-sided coated tape (100) has at least three layers: a core layer (11) having a first major surface and a second major surface opposite the first major surface, a first pressure-sensitive adhesive layer (12) disposed on the first major surface of the core layer, and a second pressure-sensitive adhesive layer (13) disposed on the second major surface of the core layer. The first pressure-sensitive adhesive layer (12) and the second pressure-sensitive adhesive layer (13) may be the same or different in terms of material and thickness. The double-sided coated tape (100) may have additional core layers and / or pressure-sensitive adhesive layers within either the core layer (11), the first pressure-sensitive adhesive layer (12), or the second pressure-sensitive adhesive layer (13), so long as the breaking elongation requirements described below are met. The double-sided coated tape (100) may also be provided in such a manner that the exposed surface of at least one of the first pressuresensitive adhesive layer (12) and the second pressure-sensitive adhesive layer (13) is covered with a separator (not depicted).

[0027] In one embodiment, the double-sided coated tape of the present invention has a thickness, defined as the distance between the exposed surface of the first pressure sensitive adhesive layer (12) and the exposed surface of the second pressure-sensitive adhesive layer (13), of 50 pm or less, 45 pm or less, 40 pm or less, 35 pm or less, 30 pm or less, 25 pm or less, or 20 pm or less. Furthermore, when the thickness of the doublesided coated tape is 15 pm or more, 16 pm or more, 17 pm or more, 18 pm or more, or 19 pm or more, it becomes easier to provide a sufficient thickness for providing the pressuresensitive adhesive layer with the required adhesive strength. In one embodiment, specific examples of the thickness range of the double-sided coated tape of the present invention include 15 pm to 50 pm, 15 pm to 45 pm, 15 pm to 40 pm, 15 pm to 35 pm, or 15 pm to 30 pm.

[0028] The double-sided coated tape of the present invention has a breaking elongation, measured in a tensile test in accordance with JIS-K-7127, of 150% or less, 145% or less, 140% or less, 135% or less, 130% or less, 125% or less, 120% or less, 115% or less, 110% or less, 105% or less, or 100% or less. A double-sided coated tape with an excessively large breaking elongation has low strength and is difficult to handle, but such problems do not occur with the double-sided coated tape of the present invention. Furthermore, suppressing the breaking elongation leads to suppression of the pressure-sensitive adhesive layer from separating irregularly from the tape when the separator is peeled off.

[0029] In one embodiment, the double-sided coated tape of the present invention has a heat shrinkage rate when heated at 250°C for 8 minutes of 0.1% or less, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, 0.05% or less, or 0.04% or less. This manner of double-sided coated tape is useful in the manufacture of electronic devices because they undergo little or no dimensional change when exposed to the environment of the reflow process. The thermal shrinkage rate can be calculated by measuring the distance that the tape has shrunk from the initial state after heating and from the size of the tape in the initial state at this distance.

[0030] The adhesive strength of the double-sided coated tape of the present invention can be evaluated, for example, using a 90° peel strength test according to JIS-Z-0237. The adhesive strength required for the double-sided coated tape of the present invention varies depending on the application. In one embodiment, the double-sided coated tape of the present invention preferably has a configuration that enables the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer on the surface of the core layer to exhibit the inherent adhesive strength thereof. For example, if the core layer is too stiff, the elongation of the pressure-sensitive adhesive layer may be suppressed, resulting in a decrease in adhesive strength. The adhesive strength of a pressure-sensitive adhesive is affected by the thickness of the pressure-sensitive adhesive. In one embodiment, the adhesive strength of the double-sided coated tape of the present invention is preferably 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more, compared to an adhesive of the same thickness that consists only of the pressure-sensitive adhesive constituting the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer and does not have a core layer. In one embodiment, when used in the manufacture of small and / or thin electronic devices, the double-sided coated tape of the present invention preferably has an adhesive strength measured by a 90° peel strength test in accordance with JIS-Z-0237 of 1.0 N / cm or more, 1.5 N / cm or more, 2.0 N / cm or more, 2.5 N / cm or more, or 3.0 N / cm or more.

[0031] (Core layer) The core layer of the double-sided coated tape of the present invention contains a urethane resin and at least one of an additive or a curing agent, and has a glass transition temperature (Tg) of 0°C or lower, -5°C or lower, -10°C or lower, -15°C or lower, or -20°C or lower. A core layer having a relatively high glass transition temperature is likely to experience heat shrinkage, whereas a core layer having a glass transition temperature of 0°C or lower is unlikely to experience heat shrinkage. In the present specification, the term "urethane resin" broadly refers to a resin whose main component is polyurethane obtained by polymerization of polyol and isocyanate, and is a concept that also includes polyurethane (meth)acrylate in which a (meth)acrylate group has been introduced into polyurethane. In one embodiment, among urethane resins, a urethane resin having a polyester-based soft segment is preferred from the viewpoint of heat resistance and mechanical properties. As the urethane resin constituting the core layer, a commercially available urethane resin solution or a commercially available ink base material based on a urethane resin can be used. Specific examples include Lamic SR Medium F-3 (Dainichiseika Color & Chemicals Mfg. Co., Ltd.) and Nipporan 5253 (Tosoh Corporation). The glass transition temperature of the urethane resin before the addition of the additive or curing agent is preferably 0°C or lower, -5°C or lower, -10°C or lower, -15°C or lower, or -20°C or lower, since this enables the glass transition temperature of the core layer to be set to a prescribed temperature or lower.

[0032] The glass transition temperature of the core layer of the double-sided coated tape can be measured, for example, by analyzing a cross-section of the tape using nano-thermal analysis (nano-TA) techniques. Nanothermal analysis is an analytical technique that combines a special probe with heating function with an atomic force microscope (AFM) to measure the thermal behavior of materials with a resolution of approximately 100 nm. When the probe is placed in contact with the surface area to be measured and then heated, the material initially expands thermally, deflecting the probe upwards. Then, when the phase transition temperature of the material is reached, the material begins to soften, causing the probe to deflect downward. By plotting the deflection of the probe versus temperature, information about the thermal properties, such as the glass transition temperature or melting point, of the surface region being measured can be obtained. Nanothermal analysis is said to be capable of measuring the glass transition temperature with an accuracy close to that of conventional DSC. The core layer of the double-sided coated tape of the present invention includes, in addition to the urethane resin, at least one of an additive or a curing agent. The core layer may include only one of the additive and the curing agent, or may include both. By adding an additive or a curing agent to the core layer, the Young's modulus of the core layer can be improved and the breaking elongation of the double-sided coated tape can be suppressed. The breaking elongation of the double-sided coated tape is significantly affected by the breaking elongation of core layer only without the pressure-sensitive adhesive layer, and can be considered to be substantially the same.

[0033] Additives that can be included in the core layer include pigments and inorganic compound materials such as metals and salts thereof. The concept of pigment includes various pigments classified into color pigments, extender pigments, metal powder pigments, pearlescent pigments, and anti-rust pigments. The pigment may be an inorganic pigment or an organic pigment. Inorganic pigments include titanium oxide, zinc oxide, antimony oxide, lithopone, carbon black, complex metal oxide black, molybdenum red, cadmium red, iron oxide red, cerium sulfide, lead yellow, cadmium yellow, lead-iron oxide yellow, complex metal oxide yellow, bismuth yellow, chromium oxide green, complex metal oxide green, Prussian blue, ultramarine, complex metal oxide blue, calcium carbonate, barium sulfate, aluminum hydroxide, talc, clay, silica powder, silicate (white carbon), aluminum powder, copper powder, brass powder, stainless steel powder, titanium oxide-coated mica, ferrous oxide-coated mica, ferric oxide-coated mica, titanium dioxidecoated mica, natural pearlescent materials, basic lead carbonate, red lead, lead suboxide, basic lead chromate, lead cyanamide, basic lead sulfate, zinc chromate, strontium chromate, calcium chromate, aluminum condensed phosphate, metal salts of phosphomolybdic acid, zinc phosphate, vanadium phosphate, calcium phosphate, zinc molybdate, calcium molybdate, mica-like iron oxide, zinc dust, cuprous oxide, silver particles, and the like. Examples of organic pigments include monoazo-based, disazo- based, azo chelate-based, disazo condensation-based, benzimidazolone-based, P-naphthol- based, naphthol AS-based, isoindolinone-isoindoline-based, metal complex-based, phthalocyanine-based, quinacridone-based, dioxazine-based, diketopyrrolopyrrole -based, quinophthalone-based, perylene-perinone-based, thioindigo-based, anthraquinone-based pigments, and the like. Representative examples of pigments include: inorganic pigments such as carbon black, titanium oxide, aluminum hydroxide, and powdered silica; and organic pigments such as phthalocyanine pigments, quinacridone pigments, and the like. Carbon black that is commercially available as a black pigment can be used. An example of commercially available carbon black is Mitsubishi Carbon Black RCF#85 (manufactured by Mitsubishi Chemical Corporation). Titanium oxide that is commercially available as a white pigment can be used. An example of commercially available titanium oxide is JR-805 (manufactured by Teika Corporation). Phthalocyanine pigments include, for example, copper phthalocyanine, also known as Phthalocyanine Blue or Pigment Blue 15, and highly chlorinated copper phthalocyanine, known as Phthalocyanine Green. An example of a commercially available phthalocyanine pigment is Cyanine Blue 4920 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.). These may be used alone or in combination of two or more.

[0034] Additives such as pigments that may be contained in the core layer preferably have an average particle size of 1.0 pm or less, 0.9 pm or less, 0.8 pm or less, 0.7 pm or less, 0.6 pm or less, 0.5 pm or less, 0.4 pm or less, 0.3 pm or less, 0.2 pm or less, or 0.1 pm or less, from the viewpoint of dispersibility.

[0035] When the core layer contains a pigment, the pigment content is preferably 1 mass% or more, 5 mass% or more, 10 mass% or more, 15 mass% or more, or 20 mass% or more, and 80 mass% or less, 75 mass% or less, 70 mass% or less, 65 mass% or less, or 60 mass% or less, based on the total mass of the core layer. In order to improve Young's modulus and suppress breaking elongation, a certain amount of pigment is preferably included, but on the other hand, if the pigment is contained in an excessively large amount, bonding to the pressure-sensitive adhesive layer may become difficult. In one embodiment, when the core layer contains a pigment, the content of the pigment, based on the total mass of the core layer, may be 1 mass% to 80 mass%, 5 mass% to 80 mass%, 10 mass% to 80 mass%, 15 mass% to 80 mass%, 20 mass% to 80 mass%, 1 mass% to 75 mass%, 1 mass% to 70 mass%, 1 mass% to 65 mass%, 1 mass% to 60 mass%, 15 mass% to 80 mass%, 15 mass% to 75 mass%, 15 mass% to 70 mass%, 15 mass% to 65 mass%, or 15 mass% to 60 mass%.

[0036] When the core layer contains a pigment, a commercially available ink with urethane resin as a base (for example, gravure ink) can be used to form the core layer. This manner of commercially available ink already contains pigment in an ink base based on a urethane resin, and can be used to form a core layer as-is, or by adding more pigment to increase the pigment concentration, or by adding more ink base material to decrease the pigment concentration. Examples of commercially available inks that can be used include the Lamic SR series (Dainichiseika Color & Chemicals Mfg. Co., Ltd.), the Bellcolor series (SAKATA INX CORPORATION), and the Lamister series (TOYO INK CO., LTD.). Examples of commercially available inks containing carbon black include R ink 1000 of the Lamiall Mark III series (manufactured by SAKATA INX CORPORATION) and SR795R ink of the Lamic series (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.). Examples of commercially available inks containing titanium oxide include R White 110 of the Lamiall Mark III series (manufactured by SAKATA INX CORPORATION), L220 701 White of the Lamic series (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and R61S White of the Lamistar series (manufactured by TOYO INK CO., LTD.). Examples of commercially available inks containing phthalocyanine blue include R Blue 800 of the Lamiall Mark III series (manufactured by SAKATA INX CORPORATION) and SR739R Blue of the Lamic series (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

[0037] As a curing agent that can be contained in the core layer, a polyfunctional isocyanate compound having two or more isocyanate groups can be suitably used. As the polyfunctional isocyanate compound, known diisocyanates such as toluene diisocyanate (TDI), xylylene diisocyanate (XDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI), as well as commercially available polyisocyanate curing agents, can be used. Examples of commercially available polyisocyanate curing agents include Curing Agent L-45K (manufactured by Soken Chemical & Engineering Co., Ltd.) and PAPI-135 (Dow Toray Co., Ltd.). Prom the viewpoint of improving the Young's modulus and suppressing the breaking elongation, it is more preferable to use a polyfunctional isocyanate compound having three or more isocyanate groups per molecule as the curing agent. The amount of the curing agent can be appropriately adjusted so as to contribute to improving the Young's modulus and suppressing the breaking elongation. Excessive amounts of curing agent may render the core layer brittle and unable to provide the necessary performance to support the pressuresensitive adhesive.

[0038] The Y oung's modulus of the core layer of the double-sided coated tape of the present invention is 15 MPa or more, 20 MPa or more, 30 MPa or more, 40 MPa or more, 50 MPa or more, 60 MPa or more, 70 MPa or more, 80 MPa or more, 90 MPa or more, or 100 MPa or more, and is 1200 MPa or less, 1150 MPa or less, 1100 MPa or less, 1050 MPa or less, 1000 MPa or less, 900 MPa or less, 800 MPa or less, 700 MPa or less, 600 MPa or less, or 500 MPa or less. A double-sided coated tape in which the core layer has an excessively large Young's modulus is rigid and difficult to bend, which makes it difficult to apply to an adherend and may even result in wrinkling of the tape. Furthermore, if the Young's modulus of the core layer is excessively large, the core layer inhibits the elongation of the pressure-sensitive adhesive layer, resulting in a decrease in adhesive strength. On the other hand, with a double-sided coated tape in which the Young's modulus of the core layer is excessively small, for example, when an attempt is made to peel off only one separator from a state in which both sides are covered with separators, the tape may lift off from the other separator. The double -sided coated tape of the present invention does not have such problems. In one embodiment, specific examples of the range of Young's modulus of the core layer of the double-sided coated tape of the present invention include 15 MPa to 1200 MPa, 15 MPa to 1100 MPa, 15 MPa to 1000 MPa, 15 MPa to 900 MPa, 15 MPa to 800 MPa, 15 MPa to 700 MPa, 15 MPa to 600 MPa, or 15 MPa to 500 MPa.

[0039] The Y oung's modulus of the core layer can be calculated, for example, by carrying out a tensile test as specified in JIS-K-7127 to measure the tensile stress for a prescribed elongation strain and from the obtained tensile stress and the cross-sectional area of the core layer. With the double-sided coated tape of the present invention, the strength of the tape depends largely on the strength of the core layer, and is affected only to a small extent by the presence of the pressure-sensitive adhesive layer. Therefore, tensile stress data obtained by subjecting a double-sided coated tape having a pressure-sensitive adhesive layer in addition to a core layer to a tensile test can be considered to be substantially the same as data obtained by subjecting only the core layer to the same test.

[0040] The breaking elongation of the core layer of the double-sided coated tape of the present invention, as measured by a tensile test in accordance with JIS-K-7127, is 150% or less, 145% or less, 140% or less, 135% or less, 130% or less, 125% or less, 120% or less, 115% or less, 110% or less, 105% or less, or 100% or less. With the double-sided coated tape of the present invention, the breaking elongation of the tape depends largely on the breaking elongation of the core layer, and is only slightly affected by the presence of the pressure-sensitive adhesive layer. Therefore, the breaking elongation data obtained by subjecting a double-sided coated tape having a pressure-sensitive adhesive layer in addition to a core layer to a tensile test can be considered to be substantially the same as the data obtained by subjecting only the core layer to the same test.

[0041] In one embodiment, the core layer of the double-sided coated tape of the present invention has a thickness of 10 pm or less, 9 pm or less, 8 pm or less, 7 pm or less, 6 pm or less, 5 pm or less, 4 pm or less, or 3 pm or less. The thin core layer contributes to the overall thinness of the double-sided coated tape. In one embodiment, the lower limit of the thickness of the core layer of the double-sided coated tape of the prescribed the present invention is not particularly limited as long as it satisfies certain conditions such as breaking elongation, and is, for example, 1 pm or more, 1.5 pm or more, 2 pm or more, 2.5 pm or more, or 3 pm or more. In one embodiment, specific examples of the thickness range of the core layer of the double-sided coated tape of the present invention include 1 pm to 10 pm, 1 pm to 9 pm, 1 pm to 8 pm, 1 pm to 7 pm, 1 pm to 6 pm, 1 pm to 5 pm, 1 pm to 4 pm, or 1 pm to 3 pm.

[0042] In one embodiment, the thickness of the core layer of the double-sided coated tape of the present invention, as a ratio of the thickness of the core layer to the thickness of the entire double-sided coated tape (core layer:total thickness), is in the range of 1:2 to 1:50, 1:2 to 1:40, 1:2 to 1:30, 1:2 to 1:20, 1:2 to 1: 15, 1:3 to 1: 15, 1:4 to 1: 15, 1:5 to 1: 15, or 1:6 to 1: 15. Setting such a ratio is preferable to facilitate achieving a good balance between the breaking elongation, Young's modulus, and adhesive strength. (Pressure-sensitive adhesive layer)

[0043] The double-sided coated tape of the present invention has at least two pressuresensitive adhesive layers disposed on each of the two major surfaces of a core layer. The two pressure-sensitive adhesive layers may be the same or different in terms of material and thickness. In general, pressure-sensitive adhesives are known to have (1) strong and permanent adhesion, (2) adhesion with no more than finger pressure, (3) sufficient retention ability on a substrate, and (4) sufficient cohesive strength to be removed cleanly from the substrate. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer in the double-sided coated tape of the present invention exerts and maintains sufficient adhesive strength between an adherend such as an electronic component and the core layer, and further has sufficient cohesive strength to peel off at least the separator covering the pressure-sensitive adhesive layer. Examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives, rubber pressuresensitive adhesives, silicone pressure-sensitive adhesives, urethane pressure-sensitive adhesives, and block copolymer pressure -sensitive adhesives. Among these, from the viewpoint of performance, acrylic pressure-sensitive adhesives and silicone pressuresensitive adhesives are preferably used, and from the viewpoint of cost, acrylic pressuresensitive adhesives are preferably used. Acrylic pressure-sensitive adhesives include copolymers of C4-8 alkyl (meth)acrylates with (meth)acrylic acid, acrylonitrile, acrylamide, and the like. Silicone-based pressure-sensitive adhesives include polydimethylsiloxane or mixtures thereof with MQ resins. The acrylic pressure-sensitive adhesive may be a commercially available one. Commercially available acrylic pressuresensitive adhesives (pressure-sensitive adhesive adhesives) include SK Dyne 1503 and SK Dyne 1717DT (Soken Chemical & Engineering Co., Ltd.). Commercially available silicone-based pressure-sensitive adhesives (pressure-sensitive adhesives) include KR3700 (Shin-Etsu Chemical Co., Ltd.) and SD4580PSA (Dow Toray Co., Ltd.). If necessary, additives such as a curing agent may be added to the pressure-sensitive adhesive.

[0044] In one embodiment, the thickness of the pressure-sensitive adhesive layer is 5 pm or more, 6 pm or more, 7 pm or more, 8 pm or more, 9 pm or more, or 10 pm or more. Such a thickness is capable of providing the required adhesive strength. In one embodiment, the thickness of the pressure-sensitive adhesive layer is 30 pm or less, 25 pm or less, 20 pm or less, or 15 pm or less. Suppressing the thickness of the pressure-sensitive adhesive layer contributes to the overall thinness of the double-sided coated tape. Specific examples of the thickness range of the pressure-sensitive adhesive layer include 5 pm to 30 pm, 5 pm to 25 pm, 5 pm to 20 pm, or 5 pm to 15 pm. The at least two pressuresensitive adhesive layers disposed on each of the two major surfaces of the core layer may have the same thickness or may have different thicknesses. The surface of the pressuresensitive adhesive layer may also be provided with a microstructure and / or microparticles to facilitate positioning and air escape when the double-sided coated tape is attached to an object.

[0045] (Manufacturing Method)

[0046] In one embodiment, the double-sided coated tape of the present invention can be produced by forming the core layer and the pressure-sensitive adhesive layer separately on a separator, and then peeling off the separator as necessary and laminating the two. In another embodiment, the double-sided coated tape of the present invention can be produced by forming a pressure-sensitive adhesive layer directly on the surface of a core layer that has previously been formed on a separator, and then peeling the separator off, and directly forming the opposing side pressure-sensitive adhesive layer on the surface of the core layer thereby revealed. In another embodiment, the double-sided coated tape of the present invention can be produced by forming a core layer directly on the surface of a pressure-sensitive adhesive layer that has already been formed on a separator, and then forming an opposing side pressure-sensitive adhesive layer directly on the surface of the core layer. The core layer and the pressure-sensitive adhesive layer can be formed by applying the precursor composition to an object using a suitable coater such as a comma coater or a knife coater, and then drying while heating as necessary.

[0047] Examples

[0048] The present invention will be described more specifically below using examples, but the present invention is not intended to be limited to the examples.

[0049] Material

[0050] Table 1

[0051] • Test Procedure

[0052] (Preparation of Core Layer Film)

[0053] 10 g (100 parts by mass) of a prescribed ink and 0 to 1000 mg (0 to 10 parts by mass) of a curing agent were placed in a 30 cc screw cap bottle and set in a mixer (ARE- 250, manufactured by THINKY CORPORATION). The mixture was stirred at 2000 rpm for 2 minutes to obtain a core layer precursor.

[0054] The previously prepared core layer precursor was applied to a silicone-treated PET separator (Purex A50) using a comma coater. After drying at 65 °C for 1 hour, a core layer film sample having a thickness of 2 to 10 pm was obtained. The sample was allowed to stand at 40°C for 1 day, and then allowed to stand at room temperature for 5 days or more, and then subjected to measurement.

[0055] The core layer precursor samples in which a pigment was added to the ink or urethane resin solution were prepared as follows. Blue pigment, ink or urethane resin solution, and solvent (LAMIC F NO2 Solvent (S)), as well as a curing agent if necessary, were placed in a 30 cc screw cap bottle, and the bottle was then set in a mixer (ARE-250, THINKY CORPORATION). The mixture was stirred at 2000 rpm for 2 minutes, and the resulting mixture was placed in an agate mortar. If necessary, a solvent (RAMIC F NO2 solvent (S)) was added, and the mixture was ground with a pestle for about 20 minutes to obtain a core layer precursor.

[0056] (Tensile test)

[0057] The tensile test was carried out in accordance with JIS-K-7127, except that a sample having a width of 15 mm and a gauge length of 25 mm was used. A sample of the core layer film together with the separator was cut into a 15 mm wide strip, and cellulose pressure-sensitive adhesive tape was attached to the surface at intervals of 25 mm. The separator was peeled off from the sample, and a cellulose pressure-sensitive adhesive tape was applied to the surface thereby revealed so as to overlap the cellulose pressuresensitive adhesive tape previously applied to the opposite side surface of the sample. This resulted in a test piece in which the gripping portion was reinforced with cellulose pressure-sensitive adhesive tape so as to enable being gripped by a tensile tester with an initial length of 25 mm.

[0058] The test was performed at room temperature using a tensile tester (Tensilon universal tester RTG-1225, load cell UR250N D, manufactured by ORIENTEC CO., LTD.: gripping width 25 mm, tensile speed 50 mm / min) by gripping the test piece at the location covered with the cellulose pressure-sensitive adhesive tape. The Young's modulus was calculated from the tensile stress and cross-sectional area for an elongation strain of 1% to 2%, with 25 mm as the initial state. The breaking elongation was calculated from the ratio of the elongation distance at break to the initial 25 mm (breaking elongation=elongation distance at break / initial 25 mm).

[0059] (Thickness Measurement)

[0060] The thickness of the core layer fdm before peeling off the separator was measured with a thickness gauge (Upright Gauge 7053, Dial Gauge 2110F, manufactured by Mitutoyo Corporation), and then the thickness of the peeled separator was measured in the same manner, and the difference therebetween was regarded as the thickness of the core layer fdm. Each measurement was carried out three times, and the average value was used. (Peel Test)

[0061] 3 g of a curing agent (curing agent L-45K) was added to 100 g of a pressuresensitive adhesive (SK Dyne 1503) and stirred to obtain an adhesive composition. The pressure-sensitive adhesive composition was applied to a low-adhesion treated surface of a polylaminated paper separator (SLB-50WD #1300, separator made of silicone treated polylaminated paper) using a knife coater. The coating was dried in a dryer at 65°C for 3 minutes to obtain a pressure-sensitive adhesive layer having a thickness of 10 pm. A silicone-treated PET separator (Purex A50) was laminated onto the pressure-sensitive adhesive layer, and the resulting sheet was allowed to stand at 40°C for 1 day, and then allowed to stand at room temperature for 6 days or more to obtain a pressure-sensitive adhesive layer sheet. Two pressure-sensitive adhesive layer sheets were prepared in the same manner. The PET separator was peeled off from the first pressure-sensitive adhesive layer sheet, and the previously prepared core layer film was placed on the surface of the pressuresensitive adhesive layer thereby revealed, and the two were laminated together while being pressed against each other with a hand roller. The separator was peeled off from the core layer film, and the PET separator of the second pressure-sensitive adhesive layer sheet was peeled off and placed on top, and the two were laminated together while being pressed against each other with a hand roller. This resulted in a double-sided pressure-sensitive adhesive sheet in which pressure-sensitive adhesive layers were provided on both sides of the core layer film, and all of the pressure-sensitive adhesive layer surfaces were covered with the same polylaminated paper separator.

[0062] The double-sided pressure-sensitive adhesive sheet was cut with a cutter to a size of about 70 mm (CD) x about 150 mm (MD). One of the separators was pinched with fingers along the short side and peeled off, and then the other separator and the doublesided pressure-sensitive adhesive sheet were each pinched with fingers and T-peeled in the direction along the long side at a speed of about 10 to 20 m / min. Those that could be peeled off from the double-sided pressure-sensitive adhesive sheet without any detachment of the adhesive were rated as OK, whereas those in which even partial detachment of the adhesive was observed were rated as NG.

[0063] (Heat Shrinkage Test)

[0064] 1.5 g of a curing agent (curing agent L-45K) was added to 100 g of a pressuresensitive adhesive (SK Dyne 1717DT) and stirred to obtain a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition was applied to a low-adhesion treated surface of a polylaminated paper separator (SLB-50WD #1300, separator made of silicone treated polylaminated paper) using a knife coater. The coating was dried in a dryer at 65°C for 3 minutes to obtain a pressure-sensitive adhesive layer having a thickness of 10 pm. A silicone-treated PET separator (Purex A50) was laminated onto the pressuresensitive adhesive layer, and the resulting sheet was allowed to stand at 40°C for 1 day, and then allowed to stand at room temperature for 6 days or more to obtain a pressuresensitive adhesive layer sheet. Two of the prepared pressure-sensitive adhesive layer sheets were used and attached to a core layer film according to the procedure described above to prepare a double-sided pressure-sensitive adhesive sheet. The double-sided pressure-sensitive adhesive sheet was cut with a cutter to a size of 25 mm x 25 mm, and the separator on one side was peeled off. A double-sided pressure-sensitive adhesive sheet was attached to a 50 mm* 100 mmx2 mm SUS304BA panel, and the ends of each side were marked with a marker pen, after which the other separator was peeled off. The end part of the sheet in the initial state thereof was photographed using a digital microscope (VHX-1000, manufactured by Keyence Corporation), and then the sheet was heated in an oven at 250°C for 8 minutes. After being left to cool to room temperature, the end part of the sheet was photographed again with a microscope, and the shrink distance from the initial state was measured. (90° Peel Strength Test)

[0065] The test was carried out in accordance with JIS-Z-0237. The same double-sided pressure-sensitive adhesive sheet as that used in the heat shrinkage test was prepared. The sheet was cut with a cutter to have a length of approximately 80 mm in the MD direction, and the separator on one side was peeled off. A 25 pm thick PET film (Emblet S-25) was cut with a cutter to have a width similar to that of the double-sided pressure-sensitive adhesive sheet and a length of about 150 mm, and was attached to the adhesive surface of the double-sided pressure-sensitive adhesive sheet. At this time, the PET film was extended on one side of the double-sided pressure-sensitive adhesive sheet so as to serve as a gripping part for the tensile tester. After the PET film was attached, the test was performed after allowing to stand for one day.

[0066] A test piece of 15 mm (CD) x 80 mm (MD) was cut out from the prepared laminate body, the separator was peeled off, and the piece was attached to an adherend (a panel made of SUS304BA) and pressed against the adherend by rolling it back and forth once with a 2 kg roller. After allowing to stand for 20 minutes, the 90° peel strength was measured using a tensile tester (Tensilon universal tester RTG-1225, load cell UR250N D, manufactured by ORIENTEC CO., LTD.: tensile speed 300 mm / min). (Tensile test of double-sided pressure-sensitive adhesive sheet)

[0067] The same double-sided pressure-sensitive adhesive sheet as that used in the heat shrinkage test and the 90° peel strength test was prepared. The whole piece including the separator was cut into a 15 mm wide strip, and the separator on one side was peeled off. The grip portion was reinforced with cellulose pressure-sensitive adhesive tape to enable gripping by a tensile tester with an initial length of 25 mm. The exposed pressure-sensitive adhesive surface was coated with talc to remove the adhesive properties. The other separator was peeled off, and a cellulose pressure-sensitive adhesive tape was applied to the surface revealed so as to overlap the cellulose pressure-sensitive adhesive tape previously applied to the opposite surface. As before, talc was applied to the exposed pressure-sensitive adhesive surface to remove the adhesive properties. The obtained sample was subjected to a tensile test in the same manner as the core layer fdm sample. (Glass Transition Temperature Measurement)

[0068] The glass transition temperature was measured using differential scanning calorimetry (DSC). Approximately 2 mL of the solution to be measured was placed in an ointment can, which was then placed in an oven at 65 °C for 1 hour to vaporize the solvent, and then the can was allowed to stand at 40°C for 24 hours. The film-like material obtained after drying was peeled off with tweezers and subjected to measurement. [Data Evaluation] (Test group 1)

[0069] Table 2 shows data for a core layer film sample prepared using a black ink with urethane resin as a base (LAMIC SR795R Ink F-3). (In the data shown hereinafter in this embodiment, sample numbers with C indicate comparative examples, and sample numbers with E indicate examples of the invention in the present application. Furthermore, the pigment concentration (mass%) is a value based on the entire core layer film, and the amount of the curing agent (parts by mass) is a value based on the amount of ink. However, this does not apply if specifically stated otherwise.) It was shown that the breaking elongation can be suppressed by adjusting the amount of the curing agent. It was also shown that the breaking elongation could be suppressed by further adding a pigment (Cyanine Blue 4920) to the ink.

[0070] Table 2

[0071] *1: The amount of E16 curing agent is in parts by mass relative to Lamic SR795R ink. (Test group 2)

[0072] Data for core layer film samples prepared using a blue ink with urethane resin as a base (LAMIC SR739R Indigo F-3) are indicated in Table 3. It was shown that the breaking elongation can be suppressed by adjusting the amount of the curing agent.

[0073] Table 3

[0074] (Test group 3) Table 4 indicates data for core layer fdm samples prepared using a pigment-free, ink base material with urethane resin as a base (LAMIC SR Medium F-3). The amount of the curing agent (parts by mass) is based on the amount of the ink base material. It was indicated that even in the absence of a pigment, the breaking elongation can be suppressed by adjusting the amount of the curing agent.

[0075] Table 4

[0076] (Test group 4) Table 5 depicts data for a core layer fdm sample prepared using a urethane resin solution (Nippolan 5253) that does not contain a pigment, which is different from Test Group 3. The amount of curing agent (parts by mass) is based on the amount of the urethane resin solution. In the case of this urethane resin solution, it was indicated that the breaking elongation could be effectively suppressed by adding a pigment.

[0077] Table 5

[0078] (Test group 5)

[0079] As a reference example, a core layer film was produced using a urethane-modified polyester resin solution (Vylon UR- 1400) having a relatively high glass transition temperature (Tg), but the Young's modulus was high and the thermal shrinkage was very large. A similar test was also carried out using a PET film (Emblet S-12), and the Young's modulus was high and the thermal shrinkage was very large. Table 6

[0080] (Test group 6) As a comparative test, a sample of only the core layer film and a sample of a double-sided pressure-sensitive adhesive sheet in which pressure-sensitive adhesive layer sheets were laminated on both sides of the core layer film were prepared and a tensile test was performed. The data are depicted in Table 7. All samples had the same core layer film configuration. Two samples of the double-sided pressure-sensitive adhesive sheet having the same configuration were prepared, and measurements were performed on each. Although there were measurement errors that were thought to be due to the difficulty of conducting tensile tests on double-sided pressure-sensitive adhesive sheets, it was confirmed that there was no significant difference in the data obtained in the tensile tests between the core layer film alone and the double-sided pressure-sensitive adhesive sheet.

[0081] Table 7

[0082] (Test group 7)

[0083] In order to examine the effect of the thickness of the core layer film on the Young's modulus and breaking elongation, samples of the core layer film differing only in thickness were prepared and subjected to a tensile test. The data are depicted in Table 8. It was confirmed that, at least within the range of the tests conducted, the thickness of the core layer film did not have a significant effect on the measurement data of Young's modulus and breaking elongation. Table 8

Claims

What is claimed is:

1. A double-sided coated tape, comprising: a core layer having a first major surface and a second major surface opposite the first major surface; a first pressure-sensitive adhesive layer disposed on the first major surface of the core layer; and a second pressure-sensitive adhesive layer disposed on the second major surface of the core layer; wherein the double-sided coated tape has a total thickness of 50 pm or less; the core layer contains urethane resin, and at least one of an additive or a curing agent, the core layer has a glass transition temperature of 0°C or lower and a Young's modulus in the range of 15 MPa to 1200 MPa; and the double-sided coated tape has a breaking elongation of 150% or less.

2. The double-sided coated tape according to claim 1, wherein the thickness of the core layer is in the range of 1 pm to 10 pm.

3. The double-sided coated tape according to claim 1, wherein the ratio of the total thickness of the double-sided coated tape to the thickness of the core layer is in the range of 1:2 to 1:50.

4. The double-sided coated tape according to claim 1, wherein the core layer includes a pigment as the additive.

5. The double-sided coated tape according to claim 4, wherein the content of the pigment is 1 mass% to 80 mass% based on the total mass of the core layer.

6. The double-sided coated tape according to claim 1, wherein the core layer includes a polyfimctional isocyanate compound as a curing agent.

7. The double-sided coated tape according to claim 1, which has athermal shrinkage rate of 0.1% or less when heated at 250°C for 8 minutes.

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