Single-sided adhesive tape

Abstract

The purpose of the present invention is to provide a single-sided adhesive tape that does not tend to wrinkle even when affixed to a thin adherend and that has exceptional resistance to strong alkaline solutions. The present invention is a single-sided adhesive tape having a base material and a heat-sensitive adhesive layer laminated on one side of the base material, wherein the base material has a metal layer at least on the surface opposite the heat-sensitive adhesive layer, and the heat-sensitive adhesive layer has a static friction coefficient against SUS of 5 or less.

Description

Single-sided adhesive tape

[0001] The present invention relates to a single-sided adhesive tape.

[0002] Conventionally, adhesives and adhesive tapes have been widely used to fix components in electronic devices. Adhesive tapes are also used as processing materials in the manufacturing process of electronic devices. For example, adhesive tapes are used to facilitate handling and prevent breakage when processing thin components in the manufacturing process of electronic devices. These adhesives and adhesive tapes are required to have not only high adhesiveness but also heat resistance, thermal conductivity, impact resistance, and other properties depending on the environment in which they are used (e.g., Patent Documents 1 to 3).

[0003] JP 2015-052050 A JP 2015-021067 A JP 2015-120876 A

[0004] On the other hand, substrates such as printed wiring boards used in electronic devices are manufactured by forming circuits on the copper foil portion of a copper-clad laminate (CCL) in which copper foil and a resin layer are laminated. In recent years, substrates such as printed wiring boards have become thinner, and for example, when the thickness of a copper-clad laminate is 100 μm or less, particularly around 30 to 40 μm, a problem occurs in that the edges of the copper-clad laminate are damaged during the manufacturing process in a process of manufacturing a substrate from the copper-clad laminate.

[0005] The present inventors have investigated the application of adhesive tape to the end of a copper-clad laminate to prevent damage to the end of the copper-clad laminate. However, because the copper-clad laminate is thin as described above, it was found that when adhesive tape is applied to the end of the copper-clad laminate, the copper-clad laminate flexes, warps, etc., causing a portion of the copper-clad laminate to come into contact with and adhere to the adhesive tape, which then becomes the starting point for wrinkling the adhesive tape. Furthermore, etching processes, desmear processes, and other processes performed in the manufacturing process of circuit boards use strongly alkaline solutions as treatment liquids. Therefore, when exposed to a strongly alkaline solution, the adhesive tape peels off, which can cause problems such as insufficient protection of the end of the copper-clad laminate or corrosion of the copper on the surface of the copper-clad laminate.

[0006] An object of the present invention is to provide a single-sided pressure-sensitive adhesive tape that is less likely to wrinkle even when applied to a thin adherend and that has excellent resistance to strong alkaline solutions.

[0007] Disclosure 1 is a single-sided pressure-sensitive adhesive tape having a substrate and a heat-sensitive adhesive layer laminated on one surface of the substrate, wherein the substrate has a metal layer on at least the surface opposite the heat-sensitive adhesive layer, and the heat-sensitive adhesive layer has a static friction coefficient against SUS of 5 or less. Disclosure 2 is the single-sided pressure-sensitive adhesive tape of Disclosure 1, in which the metal layer is made of copper. Disclosure 3 is the single-sided pressure-sensitive adhesive tape of Disclosure 1 or 2, in which the substrate is a metal substrate. Disclosure 4 is the single-sided pressure-sensitive adhesive tape of Disclosure 3, in which the metal substrate is copper foil. Disclosure 5 is the single-sided pressure-sensitive adhesive tape of Disclosure 1, 2, 3, or 4, further comprising a pressure-sensitive adhesive layer between the substrate and the heat-sensitive adhesive layer. Disclosure 6 is the single-sided pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, or 5, in which the heat-sensitive adhesive layer has a peak temperature of 40°C or higher in loss tangent measured at a measurement frequency of 1 Hz using a dynamic viscoelasticity measuring device. Disclosure 7 is the single-sided pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, or 6, wherein the heat-sensitive adhesive layer has a storage modulus G' at 23°C of 5 MPa or more and a storage modulus G' at 100°C of 0.2 MPa or less. Disclosure 8 is the single-sided pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the heat-sensitive adhesive layer has a gel fraction of 50 wt% or more. Disclosure 9 is the single-sided pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the heat-sensitive adhesive layer has a surface roughness Ra of 0.01 μm or more and 0.8 μm or less. Disclosure 10 is the single-sided pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the heat-sensitive adhesive layer contains an acrylic polymer.

[0023] Disclosure 11 is the single-sided pressure-sensitive adhesive tape of Disclosure 10, wherein the heat-sensitive adhesive layer further contains a tackifier resin. Disclosure 12 is the single-sided pressure-sensitive adhesive tape of Disclosure 11, wherein the tackifier resin has a softening point of 100°C or higher. Disclosure 13 is the single-sided pressure-sensitive adhesive tape of Disclosure 11 or 12, wherein the tackifier resin has a hydroxyl value of 25 mgKOH / g or higher. Disclosure 14 is the single-sided pressure-sensitive adhesive tape of Disclosure 11, 12, or 13, wherein the content of the tackifier resin per 100 parts by weight of the acrylic polymer is 5 parts by weight or more and 50 parts by weight or less. Disclosure 15 is the single-sided pressure-sensitive adhesive tape of Disclosure 10, 11, 12, 13, or 14, wherein the heat-sensitive adhesive layer contains an epoxy-based crosslinking agent.

[0023] Disclosure 16 is the single-sided pressure-sensitive adhesive tape of Disclosure 5, wherein the pressure-sensitive adhesive layer has a gel fraction of 50% by weight or more. Disclosure 17 is the single-sided pressure-sensitive adhesive tape of Disclosure 5, wherein the pressure-sensitive adhesive layer contains an epoxy-based crosslinking agent. Disclosure 18 is a single-sided pressure-sensitive adhesive tape having a substrate and a heat-sensitive adhesive layer laminated on one side of the substrate, wherein the substrate has a metal layer on at least the surface opposite to the heat-sensitive adhesive layer, the heat-sensitive adhesive layer contains an acrylic polymer and a tackifier resin, the tackifier resin has a softening point of 100°C or higher and a hydroxyl value of 25 mgKOH / g or higher, the content of the tackifier resin per 100 parts by weight of the acrylic polymer is 5 parts by weight or more and 50 parts by weight or less, and the heat-sensitive adhesive layer has a static friction coefficient of 5 or less against SUS. Disclosure 19 is the single-sided pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, which is used to protect the edge of a metal-clad laminate by being attached to the edge of the metal-clad laminate in an etching process, a desmear process, or an electroless plating process. Disclosure 20 is a single-sided pressure-sensitive adhesive tape having a metal layer on one side and a heat-sensitive adhesive layer on the other side, wherein the heat-sensitive adhesive layer has a static friction coefficient against SUS of 5 or less. Disclosure 21 is the single-sided pressure-sensitive adhesive tape of Disclosure 21, wherein the metal layer is made of copper. Disclosure 22 is the single-sided pressure-sensitive adhesive tape of Disclosures 20 or 21, further comprising a pressure-sensitive adhesive layer between the substrate and the heat-sensitive adhesive layer. Disclosure 23 is the single-sided pressure-sensitive adhesive tape of Disclosure 20, 21, or 22, wherein the heat-sensitive adhesive layer has a peak temperature of loss tangent of 40° C. or higher, measured at a measurement frequency of 1 Hz using a dynamic viscoelasticity measuring device. Disclosure 24 is the single-sided pressure-sensitive adhesive tape of Disclosure 20, 21, 22, or 23, wherein the heat-sensitive adhesive layer has a storage modulus G' at 23° C. of 5 MPa or higher and a storage modulus G' at 100° C. of 0.2 MPa or lower. Disclosure 25 is the single-sided pressure-sensitive adhesive tape of Disclosure 20, 21, 22, 23, or 24, wherein the heat-sensitive adhesive layer has a gel fraction of 50 wt % or higher.

[0033] Disclosure 26 is the single-sided pressure-sensitive adhesive tape of Disclosures 20, 21, 22, 23, 24, or 25, wherein the heat-sensitive adhesive layer has a surface roughness Ra of 0.01 μm or more and 0.8 μm or less. Disclosure 27 is the single-sided pressure-sensitive adhesive tape of Disclosures 20, 21, 22, 23, 24, 25, or 26, wherein the heat-sensitive adhesive layer contains an acrylic polymer. Disclosure 28 is the single-sided pressure-sensitive adhesive tape of Disclosure 27, wherein the heat-sensitive adhesive layer further contains a tackifier resin. Disclosure 29 is the single-sided pressure-sensitive adhesive tape of Disclosure 28, wherein the tackifier resin has a softening point of 100°C or more. Disclosure 30 is the single-sided pressure-sensitive adhesive tape of Disclosures 28 or 29, wherein the tackifier resin has a hydroxyl value of 25 mgKOH / g or more.

[0037] Disclosure 31 is the single-sided pressure-sensitive adhesive tape of Disclosure 28, 29, or 30, wherein the content of the tackifier resin per 100 parts by weight of the acrylic polymer is 5 parts by weight or more and 50 parts by weight or less. Disclosure 32 is the single-sided pressure-sensitive adhesive tape of Disclosure 27, 28, 29, 30, or 31, wherein the heat-sensitive adhesive layer contains an epoxy-based crosslinking agent. Disclosure 33 is the single-sided pressure-sensitive adhesive tape of Disclosure 22, wherein the pressure-sensitive adhesive layer has a gel fraction of 50% by weight or more. Disclosure 34 is the single-sided pressure-sensitive adhesive tape of Disclosure 22, wherein the pressure-sensitive adhesive layer contains an epoxy-based crosslinking agent. Disclosure 35 is the single-sided pressure-sensitive adhesive tape of Disclosures 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, or 34, which is used to protect the edge of a metal-clad laminate by being attached to the edge of the metal-clad laminate in an etching step, a desmear step, or an electroless plating step. The present invention will be described in detail below.

[0008] The present inventors have investigated a single-sided adhesive tape having a substrate and a heat-sensitive adhesive layer laminated on one side of the substrate, by providing the substrate with a metal layer on at least the surface opposite the heat-sensitive adhesive layer, and by adjusting the static friction coefficient of the heat-sensitive adhesive layer against SUS to a certain value or less. The present inventors have found that such a single-sided adhesive tape is less likely to wrinkle even when attached to a thin adherend, and has excellent resistance to strong alkaline solutions, which has led to the completion of the present invention.

[0009] In one aspect of the present invention, the single-sided adhesive tape has a substrate and a heat-sensitive adhesive layer laminated on one side of the substrate. The substrate refers to the entire portion of the single-sided adhesive tape excluding the adhesive layer, and is a member that supports the adhesive layer. The adhesive layer may include, in addition to the heat-sensitive adhesive layer located on the outermost surface of the single-sided adhesive tape, another adhesive layer (e.g., a pressure-sensitive adhesive layer) having a different composition from the heat-sensitive adhesive layer. That is, "a heat-sensitive adhesive layer laminated on one side of the substrate" means that a heat-sensitive adhesive layer is disposed on one side of the substrate, and the substrate and the heat-sensitive adhesive layer are directly or indirectly bonded to each other. Specifically, the single-sided adhesive tape includes a case in which the substrate and the heat-sensitive adhesive layer are in direct contact with each other, and a case in which the other adhesive layer is present between the heat-sensitive adhesive layer and the substrate. The heat-sensitive adhesive layer is a layer containing an adhesive that exhibits almost no adhesiveness at room temperature (23°C) but exhibits adhesiveness when heated to a temperature above the glass transition point of the adhesive layer, and the pressure-sensitive adhesive layer is a layer containing an adhesive that exhibits adhesiveness at room temperature (23°C).

[0010] The substrate has a metal layer at least on the surface opposite to the heat-sensitive adhesive layer. That is, in the single-sided adhesive tape of the present invention, one outermost surface is a metal layer constituting the substrate, and the other outermost surface is a heat-sensitive adhesive layer. By disposing the metal layer on at least the surface of the substrate, when the single-sided adhesive tape is attached to the end of a metal-clad laminate, the metal layer is exposed on the outermost surface. This makes the single-sided adhesive tape less likely to peel off even when exposed to a strong alkaline solution. Furthermore, when a metal plating process such as electroless plating is performed, the metal plating layer deposited on the surface of the metal layer is less likely to peel off from the metal layer. Therefore, even if a metal plating process is performed on a metal-clad laminate with the single-sided adhesive tape attached, it is possible to prevent the metal plating layer from peeling off from the single-sided adhesive tape in a subsequent process, causing problems.

[0011] The metal constituting the metal layer is not particularly limited, and examples thereof include copper, aluminum, nickel, titanium, etc. Further examples of the metal constituting the metal layer include alloys such as stainless steel and Monel. Among these, it is preferable that the metal layer be made of copper, since copper has a small restoring force after folding and is not easily torn, thereby improving the handleability of the single-sided pressure-sensitive adhesive tape.

[0012] The substrate is not particularly limited as long as it has the metal layer on at least the surface opposite to the heat-sensitive adhesive layer, and may be a single layer or multiple layers. When the substrate is a single layer, it is composed only of the metal layer. Hereinafter, a substrate composed only of the metal layer is also referred to as a metal substrate. Note that the metal substrate refers to substrates generally composed only of a metal layer, and includes not only substrates composed of a single metal layer but also substrates composed of multiple metal layers. When the substrate is composed of multiple layers, the layer constituting the surface opposite to the heat-sensitive adhesive layer is the metal layer, and the other layers are not limited. For example, the substrate itself may be a metal substrate, or it may be a laminated substrate having a resin substrate and the metal layer laminated on the surface of the resin substrate. In particular, when the substrate is a metal substrate, even if a single-sided adhesive tape is folded (bent) so as to span from the front surface to the back surface of the metal-clad laminate and attached to the edge of the metal-clad laminate, the metal substrate maintains its shape, thereby suppressing the restoring force caused by folding the metal substrate. This makes it less likely that gaps will occur between the end of the metal-clad laminate and the heat-sensitive adhesive layer, making peeling even less likely to occur.

[0013] The metal constituting the metal substrate is not particularly limited, and examples thereof include the metals constituting the metal layer as described above. Among these, it is preferable that the metal substrate is copper foil, since copper foil has a small restoring force after folding and is not easily torn, thereby improving the handleability of the single-sided pressure-sensitive adhesive tape.

[0014] The resin substrate is not particularly limited, and examples thereof include polyolefin resin films such as polyethylene film and polypropylene film, polyester resin films such as polyethylene terephthalate (PET) film, ethylene-vinyl acetate copolymer film, polyvinyl chloride resin film, and polyurethane resin film. Examples of the resin substrate also include polyolefin foam sheets such as polyethylene foam sheets and polypropylene foam sheets, and polyurethane foam sheets. Of these, PET film is preferred.

[0015] The thickness of the substrate (the entire thickness of the substrate including the metal layer) is not particularly limited, but a preferred lower limit is 2 μm, and a preferred upper limit is 30 μm. When the thickness of the substrate is within the above range, peeling is less likely to occur even when the single-sided adhesive tape is folded (bent) and attached to the end of a metal-clad laminate. A more preferred lower limit of the thickness of the substrate is 4 μm, and a more preferred upper limit is 20 μm. Furthermore, the thickness of the metal layer in the substrate is not particularly limited, but a preferred lower limit of the ratio of the thickness of the metal layer to the entire thickness of the substrate is 0.1%. If the thickness ratio of the metal layer is 0.1% or more, the resistance of the single-sided adhesive tape to strong alkaline solutions is improved. A more preferred lower limit of the thickness ratio of the metal layer is 1%. The upper limit of the thickness ratio of the metal layer is not particularly limited, and when the substrate is a metal substrate, the thickness ratio of the metal layer is 100%.

[0016] The heat-sensitive adhesive layer has an upper limit of the static friction coefficient against SUS (stainless steel) of 5. Because the heat-sensitive adhesive layer exhibits almost no adhesiveness at room temperature, even if a portion of the metal-clad laminate comes into contact with the heat-sensitive adhesive layer when the single-sided adhesive tape is applied to the end of the metal-clad laminate, the heat-sensitive adhesive layer does not stick to the metal-clad laminate, and wrinkles are unlikely to occur. Furthermore, since the static friction coefficient against SUS is 5 or less, the heat-sensitive adhesive layer can slide against the metal-clad laminate. Therefore, even if a portion of the metal-clad laminate comes into contact with the heat-sensitive adhesive layer when the single-sided adhesive tape is applied to the end of the metal-clad laminate, the contacting portion can slide, thereby uniforming the application stress. This prevents load from being applied to the substrate, and makes wrinkles unlikely to occur. The preferred upper limit of the static friction coefficient against SUS is 3, and more preferably 2. The lower limit of the static friction coefficient against SUS is not particularly limited, but is essentially about 0.1. The static friction coefficient against SUS can be measured using SUS304 (size 63 mm x 63 mm, weight 200 g) as the sliding piece, at a pulling speed of 100 mm / min, in accordance with JIS K7125, at room temperature (23°C) and 50% humidity. During measurement, a single-sided adhesive tape sample is placed on the counter material, and with a sliding piece (weight) placed on the single-sided adhesive tape, the single-sided adhesive tape is pulled with a string, and the resistance (friction) generated at this time is measured. Similar to the sliding piece, SUS304 (size 250 mm x 150 mm x thickness 1.5 mm) can be used as the counter material.

[0017] The method for adjusting the static friction coefficient within the above range is not particularly limited, and examples include a method for adjusting the peak temperature of the loss tangent measured at a measurement frequency of 1 Hz using a dynamic viscoelasticity measuring device, the storage modulus G' at 23°C, the gel fraction, the surface roughness Ra, and the like, within appropriate ranges. More specifically, examples of a method for adjusting the peak temperature of the loss tangent, the storage modulus G' at 23°C, the gel fraction, and the like of the heat-sensitive adhesive layer include a method for adjusting the type, molecular weight, and molecular weight distribution of the base polymer contained in the heat-sensitive adhesive layer, the type and content of the tackifier resin, and the type and content of the crosslinking agent. Another method for adjusting the surface roughness Ra includes a method for appropriately adjusting the surface roughness of a film (e.g., a release-treated PET film) onto which the adhesive solution for forming the heat-sensitive adhesive layer is applied when the heat-sensitive adhesive layer is formed. The surface roughness of the film used is transferred to the surface of the heat-sensitive adhesive layer, and therefore the surface roughness Ra of the heat-sensitive adhesive layer can be adjusted by appropriately adjusting the surface roughness of the film.

[0018] The heat-sensitive adhesive layer has a loss tangent (hereinafter referred to as tan δ, or simply loss tangent) peak temperature measured at a measurement frequency of 1 Hz using a dynamic viscoelasticity measuring device, but is preferably 40°C or higher. Having a loss tangent peak temperature of 40°C or higher makes it easier to adjust the static friction coefficient against SUS within the above range, thereby further suppressing wrinkles when the single-sided pressure-sensitive adhesive tape is attached to the edge of a metal-clad laminate. The loss tangent peak temperature is more preferably 42°C or higher, and even more preferably 45°C or higher. The loss tangent peak temperature is preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower. The loss tangent can be obtained by measuring a dynamic viscoelasticity spectrum from -40°C to 140°C using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., DVA-200, or an equivalent) in a slow heating rate shear deformation mode at 5°C / min and 1 Hz.

[0019] The storage modulus G' of the heat-sensitive adhesive layer is not particularly limited, but a preferred lower limit of the storage modulus G' at 23°C is 5 MPa, and a preferred upper limit of the storage modulus G' at 100°C is 0.2 MPa. If the storage modulus G' at 23°C is 5 MPa or more, the heat-sensitive adhesive layer exhibits almost no adhesiveness at room temperature, thereby further suppressing wrinkles when the single-sided adhesive tape is attached to the edge of a metal-clad laminate. A more preferred lower limit of the storage modulus G' at 23°C is 8 MPa, and an even more preferred lower limit is 10 MPa. The upper limit of the storage modulus G' at 23°C is not particularly limited, but from the viewpoint of easily forming the single-sided adhesive tape into a roll, a preferred upper limit is 10,000 MPa, and a more preferred upper limit is 1,000 MPa.

[0020] If the storage modulus G' at 100°C is 0.2 MPa or less, the heat-sensitive adhesive layer will exhibit sufficient adhesiveness upon heating, and the single-sided adhesive tape can be attached to the end of the metal-clad laminate by contacting the single-sided adhesive tape with the end of the metal-clad laminate, adjusting the position, etc. so that the single-sided adhesive tape does not wrinkle or lift, and then performing heat and pressure bonding. A more preferred upper limit of the storage modulus G' at 100°C is 0.1 MPa, and an even more preferred upper limit is 0.08 MPa. There are no particular restrictions on the lower limit of the storage modulus G' at 100°C, but from the viewpoint of suppressing exudation due to deformation of the heat-sensitive adhesive layer during heat and pressure bonding, a preferred lower limit is 0.01 MPa, and a more preferred lower limit is 0.05 MPa. The storage modulus G' at 23°C or 100°C can be obtained by measuring from -40°C to 140°C using a dynamic viscoelasticity measuring device (for example, "DVA-200" manufactured by IT Measurement & Control Co., Ltd., or "ARES" manufactured by Rheometrics Co., Ltd.) under the conditions of shear mode of dynamic viscoelasticity measurement, angular frequency of 1 Hz, and speed of 5°C / min.

[0021] The gel fraction of the heat-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 50% by weight. A gel fraction of 50% by weight or more suppresses swelling of the heat-sensitive adhesive layer in a strong alkaline solution, thereby improving the resistance of the single-sided adhesive tape to a strong alkaline solution. Furthermore, a gel fraction of 50% by weight or more makes it easier to adjust the static friction coefficient against SUS to the above range, thereby further reducing wrinkling when the single-sided adhesive tape is applied to the edge of a metal-clad laminate. A more preferred lower limit of the gel fraction is 60% by weight. The upper limit of the gel fraction is not particularly limited, but a preferred upper limit is 90% by weight, and a more preferred upper limit is 80% by weight, because the heat-sensitive adhesive layer is likely to exhibit sufficient adhesiveness upon heating. The gel fraction can be measured by the following method. 0.1 g of the heat-sensitive adhesive layer (adhesive composition) alone is removed from the single-sided adhesive tape, immersed in 50 mL of ethyl acetate, and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the ethyl acetate and the adhesive composition that has absorbed the ethyl acetate and swollen are separated using a metal mesh (opening #200 mesh). The separated adhesive composition is dried at 110°C for 1 hour. The weight of the dried adhesive composition including the metal mesh is measured, and the gel fraction is calculated using the following formula: Gel fraction (wt%) = 100 x (W １ -W ２ ) / W ０ (W ０ : initial pressure-sensitive adhesive composition weight, W １ : Weight of the pressure-sensitive adhesive composition including the metal mesh after drying, W ２ : initial weight of the metal mesh)

[0022] The surface roughness Ra of the heat-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 0.01 μm and a preferred upper limit is 0.8 μm. If the surface roughness Ra is within the above range, it becomes easier to adjust the static friction coefficient against SUS to the above range, and wrinkles can be more effectively suppressed when the single-sided adhesive tape is attached to the edge of the metal-clad laminate. A more preferred lower limit of the surface roughness Ra is 0.02 μm and a more preferred upper limit is 0.1 μm. The surface roughness Ra refers to the arithmetic mean roughness defined in JIS B 0601-2001.

[0023] The heat-sensitive adhesive layer is not particularly limited, and for example, a rubber-based, styrene-based, polyester-based, acrylic-based or other heat-sensitive adhesive layer can be used. However, it is preferable that the heat-sensitive adhesive layer contains an acrylic polymer, since the heat-sensitive adhesive layer is relatively stable against light, heat, moisture, etc., and can be adhered to various adherends by heat and pressure bonding.

[0024] The acrylic polymer contained in the heat-sensitive adhesive layer (hereinafter also referred to as the acrylic polymer for the heat-sensitive adhesive layer) is not particularly limited, but preferably contains a structural unit derived from a monomer having a crosslinkable functional group. The presence of such a structural unit allows crosslinking between the acrylic polymers for the heat-sensitive adhesive layer when a crosslinking agent is used in combination. By adjusting the degree of crosslinking, it becomes easier to adjust the storage modulus G' of the heat-sensitive adhesive layer to within the above range, and it becomes easier to adjust the static friction coefficient against SUS to within the above range.

[0025] Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group, and a nitrile group. Among these, a hydroxyl group or a carboxyl group is preferred because it allows for easy adjustment of the storage modulus G' of the heat-sensitive adhesive layer. Examples of the monomer having a hydroxyl group include (meth)acrylic acid esters having a hydroxyl group, such as 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Examples of the monomer having a carboxyl group include (meth)acrylic acid. Examples of the monomer having a glycidyl group include glycidyl (meth)acrylate. Examples of the monomer having an amide group include hydroxyethyl acrylamide, isopropyl acrylamide, and dimethylaminopropyl acrylamide. Examples of the monomer having a nitrile group include acrylonitrile. These monomers having a crosslinkable functional group may be used alone, or two or more of them may be used in combination. In this specification, (meth)acrylate means acrylate or methacrylate, and (meth)acrylic means acrylic or methacrylic. The acrylic polymer may be a methacrylic polymer.

[0026] The content of the structural unit derived from the monomer having a crosslinkable functional group in the acrylic polymer for the heat-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 0.1 wt % and a preferred upper limit is 5 wt %. Furthermore, when the monomer having a carboxyl group is used as the monomer having a crosslinkable functional group, the resistance of the single-sided pressure-sensitive adhesive tape to a strong alkaline solution is further increased, so that the upper limit of the content of the structural unit derived from the monomer having a carboxyl group is more preferably 3 wt %, and even more preferably 0.5 wt %.

[0027] The acrylic polymer for the heat-sensitive adhesive layer preferably contains a structural unit derived from a (meth)acrylate having an alkyl group with 1 to 4 carbon atoms, and more preferably a structural unit derived from a methacrylate having an alkyl group with 1 to 4 carbon atoms. The acrylic polymer for the heat-sensitive adhesive layer also preferably contains a structural unit derived from a (meth)acrylate having an alkyl group with a cyclic structure. The inclusion of these structural units in the acrylic polymer for the heat-sensitive adhesive layer makes it easier to adjust the loss tangent peak temperature and storage modulus G' of the heat-sensitive adhesive layer within the above-mentioned ranges, and also makes it easier to adjust the static friction coefficient against SUS within the above-mentioned ranges, thereby further suppressing wrinkles when the single-sided pressure-sensitive adhesive tape is attached to the edge of a metal-clad laminate. The acrylic polymer for the heat-sensitive adhesive layer more preferably contains at least one structural unit selected from the group consisting of a structural unit derived from a methacrylate having an alkyl group with 1 to 4 carbon atoms and a structural unit derived from a methacrylate having an alkyl group with a cyclic structure.

[0028] The (meth)acrylate having an alkyl group having 1 to 4 carbon atoms is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. The (meth)acrylate having an alkyl group with a cyclic structure is not particularly limited, and examples thereof include cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. These (meth)acrylates may be used alone or in combination of two or more. Among these, it is preferable to use at least one selected from the group consisting of methyl methacrylate, butyl acrylate, butyl methacrylate, and isobornyl methacrylate, since this makes it easier to adjust the peak temperature of the loss tangent and the storage modulus G' of the heat-sensitive adhesive layer to more preferred ranges.

[0029] The total content of the structural units derived from a (meth)acrylate having an alkyl group with 1 to 4 carbon atoms and the structural units derived from a (meth)acrylate having an alkyl group with a cyclic structure in the acrylic polymer for the heat-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 50 wt% and a preferred upper limit is 98 wt%. When the total content of these structural units is within the above range, it becomes easier to adjust the loss tangent peak temperature and storage modulus G' of the heat-sensitive adhesive layer to the above ranges, and it becomes easier to adjust the static friction coefficient against SUS to the above ranges, thereby further suppressing wrinkles when the single-sided pressure-sensitive adhesive tape is attached to the edge of a metal-clad laminate. The lower limit of the total content of these structural units is more preferably 60 wt%, even more preferably 70 wt%, and more preferably 95 wt%, even more preferably 90 wt%, and even more preferably 80 wt%. The above total content represents the total content of the structural units derived from a (meth)acrylate having an alkyl group with 1 to 4 carbon atoms and the structural units derived from a (meth)acrylate having an alkyl group with a cyclic structure, but the acrylic polymer for the heat-sensitive adhesive layer may contain only one of them or both.

[0030] From the same viewpoint, the total content of the structural units derived from methacrylate having an alkyl group with 1 to 4 carbon atoms and the structural units derived from methacrylate having an alkyl group with a cyclic structure in the acrylic polymer for the heat-sensitive adhesive layer is preferably 50% by weight at the lower limit and 90% by weight at the upper limit, and more preferably 60% by weight at the lower limit and 80% by weight at the upper limit, respectively.

[0031] The acrylic polymer for the heat-sensitive adhesive layer may further contain structural units derived from other monomers, provided that the effects of the present invention are not impaired. Examples of such other monomers include n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, vinyl acetate, and fluorine-containing (meth)acrylates. When the acrylic polymer for the heat-sensitive adhesive layer is prepared by ultraviolet polymerization, it is preferable that the polymer further contain structural units derived from polyfunctional monomers such as divinylbenzene and trimethylolpropane tri(meth)acrylate.

[0032] The solubility parameter (SP value) of the acrylic polymer for the heat-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 9.2 and a preferred upper limit is 10.5. If the SP value is within the above range, swelling of the heat-sensitive adhesive layer in a strong alkaline solution is suppressed, and the resistance of the single-sided adhesive tape to a strong alkaline solution is improved. Furthermore, if the SP value is within the above range, the adhesion of the heat-sensitive adhesive layer to a metal-clad laminate is increased, and the metal-clad laminate can be sufficiently protected. A more preferred lower limit of the SP value is 9.5, a more preferred upper limit is 10.2, an even more preferred lower limit is 9.6, and an even more preferred upper limit is 10. The solubility parameter (SP value) is the solubility parameter (SP value) according to the Fedors method ((cal / cm ３ )０．５ ) and is an index that can represent the ease of dissolution, calculated using the Fedors method (R.F. Fedors, Polym. Eng. Sci., 14(2), 147-154 (1974)).

[0033] The weight-average molecular weight (Mw) of the acrylic polymer for the heat-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 250,000, a preferred upper limit is 2,000,000, a more preferred lower limit is 300,000, an even more preferred lower limit is 400,000, and a more preferred upper limit is 1,500,000. The weight-average molecular weight (Mw) can be adjusted by the polymerization conditions (e.g., the type or amount of polymerization initiator, the polymerization temperature, the monomer concentration, etc.). The weight-average molecular weight (Mw) can be measured by the following method. The acrylic polymer solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm). The obtained filtrate is fed to a gel permeation chromatograph (e.g., Waters, 2690 Separations Model) and subjected to GPC measurement under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The polystyrene-equivalent molecular weight of the acrylic polymer is measured to determine the weight-average molecular weight (Mw). As the column, for example, GPC KF-806L or GPC LF-804 (manufactured by Showa Denko KK) is used, and as the detector, a differential refractometer is used.

[0034] The method for preparing the acrylic polymer for the heat-sensitive adhesive layer is not particularly limited, and examples thereof include a method in which a monomer from which the structural unit is derived is subjected to a radical reaction in the presence of a polymerization initiator. The polymerization method is not particularly limited, and conventionally known methods can be used. Examples include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization is preferred from the viewpoints of easy synthesis and water resistance.

[0035] When solution polymerization is used as the polymerization method, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, diethyl ether, etc. These reaction solvents may be used alone or in combination of two or more.

[0036] The polymerization initiator is not particularly limited, and examples thereof include organic peroxides and azo compounds. Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

[0037] The heat-sensitive adhesive layer preferably further contains a tackifier resin. By including the tackifier resin in the heat-sensitive adhesive layer, the interfacial adhesion when the single-sided adhesive tape is heated and pressed is improved, and the resistance of the single-sided adhesive tape to strong alkaline solutions is further increased. The tackifier resin is not particularly limited, and examples thereof include coumarone resins, terpene resins, terpene phenol resins, rosin resins, rosin derivative resins, petroleum resins, alkylphenol resins, and hydrogenated versions of these. These tackifier resins may be used alone or in combination of two or more.

[0038] The terpene phenolic resin refers to a polymer containing a terpene residue and a phenol residue. The term "terpene phenolic resin" encompasses a copolymer of a terpene and a phenolic compound (terpene-phenol copolymer resin), a phenol-modified terpene resin obtained by phenol-modifying a terpene homopolymer or copolymer (terpene resin, typically an unmodified terpene resin), and a resin obtained by hydrogenating the terpene moiety in these resins.

[0039] The terpene constituting the terpene phenol resin is not particularly limited, but is preferably a monoterpene such as α-pinene, β-pinene, limonene, camphene, etc. Limonene includes d-, l- and d / l-isomers (dipentene).

[0040] More specifically, examples of the rosin resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, as well as modified rosins obtained by modifying these unmodified rosins. Modifications of the modified rosins include, for example, hydrogenation, disproportionation, and polymerization. More specifically, examples of the modified rosins include hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins.

[0041] More specifically, examples of the rosin derivative resin include rosin ester resins obtained by esterifying the rosin resin with alcohols, unsaturated fatty acid-modified rosin resins obtained by modifying the rosin resin with unsaturated fatty acids, and unsaturated fatty acid-modified rosin ester resins obtained by modifying the rosin ester resin with unsaturated fatty acids. Other examples of the rosin derivative resin include rosin alcohol resins obtained by reducing the carboxyl groups in the unsaturated fatty acid-modified rosin resins or unsaturated fatty acid-modified rosin ester resins. Furthermore, examples of the rosin derivative resin include metal salts of the rosin resins or rosin derivative resins (particularly rosin ester resins) and rosin phenolic resins. Rosin phenolic resins can be obtained by adding phenol to the rosin resin or rosin derivative resin in the presence of an acid catalyst and then thermally polymerizing the resulting mixture.

[0042] More specific examples of the petroleum resin include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, C5 / C9 copolymer petroleum resins, alicyclic petroleum resins, and hydrogenated products thereof.

[0043] In particular, the tackifier resin preferably has a softening point of 100°C or higher and a hydroxyl value of 25 mgKOH / g or higher. When the heat-sensitive adhesive layer contains such a tackifier resin, the interfacial adhesion when the single-sided adhesive tape is heated and pressed is improved, and the resistance of the single-sided adhesive tape to strong alkaline solutions is further increased. Furthermore, the tackifier resin more preferably contains a hydrogenated rosin ester resin having a hydroxyl value of 40 mgKOH / g or higher. The upper limit of the hydroxyl value of the hydrogenated rosin ester resin having a hydroxyl value of 40 mgKOH / g or higher is not particularly limited, but is typically about 80 mgKOH / g, and preferably 50 mgKOH / g or lower.

[0044] The content of the tackifier resin is not particularly limited, but a preferred lower limit is 5 parts by weight and a preferred upper limit is 50 parts by weight, more preferably 10 parts by weight and more preferably 35 parts by weight, per 100 parts by weight of the acrylic polymer for the heat-sensitive adhesive layer. When the content of the tackifier resin is within the above range, the interfacial adhesion when the single-sided pressure-sensitive adhesive tape is heated and pressed is improved, and the resistance of the single-sided pressure-sensitive adhesive tape to strong alkaline solutions is further increased.

[0045] The heat-sensitive adhesive layer may contain a silane coupling agent, which improves the interfacial adhesion when the single-sided pressure-sensitive adhesive tape is heated and pressed, and further increases the resistance of the single-sided pressure-sensitive adhesive tape to strong alkaline solutions.

[0046] The silane coupling agent is not particularly limited, and examples thereof include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethylmethoxysilane, N-(2-aminoethyl)3-aminopropyltriethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptobutyltrimethoxysilane, and γ-mercaptopropylmethyldimethoxysilane. Of these, γ-glycidoxypropyltriethoxysilane and γ-mercaptopropyltrimethoxysilane are preferred.

[0047] The content of the silane coupling agent is not particularly limited, but a preferred lower limit is 0.1 parts by weight and a preferred upper limit is 5 parts by weight per 100 parts by weight of the acrylic polymer for the heat-sensitive adhesive layer.By having the content of the silane coupling agent within this range, the interface adhesion when the single-sided adhesive tape is heated and pressed is improved, and the resistance of the single-sided adhesive tape to strong alkaline solutions is further increased.A more preferred lower limit of the content of the silane coupling agent is 0.5 parts by weight and a more preferred upper limit is 3 parts by weight.

[0048] The heat-sensitive adhesive layer may further contain a crosslinking agent. When the heat-sensitive adhesive layer contains the crosslinking agent, crosslinking between the acrylic polymers for the heat-sensitive adhesive layer can be achieved when the acrylic polymer for the heat-sensitive adhesive layer contains a structural unit derived from the monomer having a crosslinkable functional group. The crosslinking agent is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-type crosslinking agents. Of these, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred. Furthermore, epoxy-based crosslinking agents are more preferred because they react with the structural unit derived from the monomer having a crosslinkable functional group to form an ester bond that is resistant to hydrolysis, thereby further increasing the resistance of the single-sided pressure-sensitive adhesive tape to strong alkaline solutions.

[0049] The content of the crosslinking agent is not particularly limited, but a preferred lower limit is 0.01 parts by weight and a preferred upper limit is 10 parts by weight, more preferably 0.1 parts by weight and more preferably 5 parts by weight, relative to 100 parts by weight of the acrylic polymer for the heat-sensitive adhesive layer.

[0050] The heat-sensitive adhesive layer may contain additives such as plasticizers, emulsifiers, softeners, fillers, pigments, and dyes, as well as other resins, if necessary.

[0051] The thickness of the heat-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 5 μm and a preferred upper limit is 100 μm. A thickness within this range allows the single-sided adhesive tape to be well heat-pressed, wrinkles during the process to be more effectively suppressed, and the single-sided adhesive tape to have higher resistance to strong alkaline solutions. A more preferred lower limit is 10 μm, a more preferred upper limit is 50 μm, an even more preferred lower limit is 20 μm, and an even more preferred upper limit is 40 μm. Furthermore, the thickness of the heat-sensitive adhesive layer is preferably thicker than half the thickness of the metal-clad laminate used as the adherend. In such a case, even when the single-sided adhesive tape is attached to the edge of the metal-clad laminate so as to extend from the front to the back of the metal-clad laminate, gaps are less likely to form between the edge of the metal-clad laminate and the heat-sensitive adhesive layer, and peeling is less likely to occur. The thickness of the heat-sensitive adhesive layer is more preferably thicker than two-thirds the thickness of the metal-clad laminate.

[0052] The single-sided adhesive tape preferably further comprises a pressure-sensitive adhesive layer between the substrate and the heat-sensitive adhesive layer, which enhances the anchoring properties between the substrate and the heat-sensitive adhesive layer, thereby further increasing the resistance of the single-sided adhesive tape to strong alkaline solutions.

[0053] The storage modulus G' of the pressure-sensitive adhesive layer is not particularly limited, but a preferred upper limit of the storage modulus G' at 23°C is 0.2 MPa. If the storage modulus G' at 23°C is 0.2 MPa or less, the anchoring property between the substrate and the heat-sensitive adhesive layer is further improved. A more preferred upper limit of the storage modulus G' at 23°C is 0.15 MPa. The lower limit of the storage modulus G' at 23°C is not particularly limited, but from the viewpoint of maintaining the cohesive strength of the pressure-sensitive adhesive layer, a preferred lower limit is 0.01 MPa, and a more preferred lower limit is 0.03 MPa. The storage modulus at 23°C can be obtained by measuring from -40°C to 140°C using a dynamic viscoelasticity measuring device (for example, "DVA-200" manufactured by IT Measurement & Control Co., Ltd. or "ARES" manufactured by Rheometrics Co., Ltd.) under dynamic viscoelasticity measurement shear mode, angular frequency 1 Hz, and speed 5°C / min.

[0054] The storage modulus G' at 23°C can be adjusted by the type, molecular weight and molecular weight distribution of the base polymer contained in the pressure-sensitive adhesive layer, the type and content of the tackifier resin, the type and content of the crosslinking agent, and the like.

[0055] The pressure-sensitive adhesive layer is not particularly limited, and for example, a rubber-based, styrene-based, polyester-based, acrylic-based, or other pressure-sensitive adhesive layer can be used. However, it is preferable that the pressure-sensitive adhesive layer contain an acrylic polymer, since the pressure-sensitive adhesive layer is relatively stable against light, heat, moisture, etc., exhibits adhesiveness at room temperature, and can adhere to a variety of substrates.

[0056] The acrylic polymer contained in the pressure-sensitive adhesive layer (hereinafter also referred to as the acrylic polymer for the pressure-sensitive adhesive layer) is not particularly limited. The acrylic polymer for the pressure-sensitive adhesive layer is preferably a (meth)acrylic acid ester copolymer obtained by copolymerizing, by a conventional method, an alkyl acrylate and / or an alkyl methacrylate ester having an alkyl group carbon number of 1 to 18 as the main monomer with a monomer having a crosslinkable functional group as needed. Furthermore, other copolymerizable modifying monomers may also be copolymerized.

[0057] The acrylic polymer for the pressure-sensitive adhesive layer preferably contains a structural unit derived from a monomer having a crosslinkable functional group. The presence of such a structural unit allows crosslinking between the acrylic polymers for the pressure-sensitive adhesive layer when a crosslinking agent is used in combination. By adjusting the degree of crosslinking, the storage modulus G' of the pressure-sensitive adhesive layer can be adjusted.

[0058] Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, a glycidyl group, an amino group, an amide group, and a nitrile group. Among these, a hydroxyl group or a carboxyl group is preferred because it allows for easy adjustment of the storage modulus G' of the pressure-sensitive adhesive layer. Examples of the monomer having a hydroxyl group include (meth)acrylic acid esters having a hydroxyl group, such as 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Examples of the monomer having a carboxyl group include (meth)acrylic acid. Examples of the monomer having a glycidyl group include glycidyl (meth)acrylate. Examples of the monomer having an amide group include hydroxyethyl acrylamide, isopropyl acrylamide, and dimethylaminopropyl acrylamide. Examples of the monomer having a nitrile group include acrylonitrile. These monomers having a crosslinkable functional group may be used alone, or two or more of them may be used in combination.

[0059] The content of the structural unit derived from the monomer having a crosslinkable functional group in the acrylic polymer for the pressure-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 0.1 wt % and a preferred upper limit is 5 wt %. Furthermore, when the monomer having a carboxyl group is used as the monomer having a crosslinkable functional group, the resistance of the single-sided pressure-sensitive adhesive tape to strong alkaline solutions is further increased, so the upper limit of the content of the structural unit derived from the monomer having a carboxyl group is more preferably 3 wt %, and even more preferably 0.5 wt %.

[0060] The acrylic polymer for the pressure-sensitive adhesive layer preferably has a structural unit derived from a (meth)acrylate having an alkyl group having at least 8 carbon atoms. The presence of such a structural unit increases the hydrophobicity of the acrylic polymer for the pressure-sensitive adhesive layer, further inhibiting penetration of strong alkaline solutions into the molecular chains, thereby further increasing the resistance of the single-sided pressure-sensitive adhesive tape to strong alkaline solutions.

[0061] Examples of the (meth)acrylate having an alkyl group having 8 or more carbon atoms include n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and isobornyl (meth)acrylate. These (meth)acrylates having an alkyl group having 8 or more carbon atoms may be used alone or in combination of two or more. Of these, 2-ethylhexyl acrylate, lauryl acrylate, and lauryl methacrylate are preferred because they prevent the pressure-sensitive adhesive layer from becoming too hard and allow sufficient tackiness to be maintained.

[0062] The content of the structural unit derived from the (meth)acrylate having an alkyl group with 8 or more carbon atoms in the acrylic polymer for the pressure-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 15 wt% and a preferred upper limit is 99 wt%. When the content of the (meth)acrylate having an alkyl group with 8 or more carbon atoms is within the above range, the hydrophobicity of the acrylic polymer for the pressure-sensitive adhesive layer is increased, and penetration of strong alkaline solutions into the molecular chain is further suppressed, thereby further improving the resistance of the single-sided adhesive tape to strong alkaline solutions. A more preferred lower limit of the content of the structural unit derived from the (meth)acrylate having an alkyl group with 8 or more carbon atoms is 20 wt%, and a more preferred upper limit is 30 wt%.

[0063] The acrylic polymer for the pressure-sensitive adhesive layer may further contain structural units derived from other monomers, provided that the effects of the present invention are not impaired. Examples of such other monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, vinyl acetate, and fluorine-containing (meth)acrylates. When the acrylic polymer for the pressure-sensitive adhesive layer is prepared by ultraviolet polymerization, it is preferable that the polymer further contain structural units derived from polyfunctional monomers such as divinylbenzene and trimethylolpropane tri(meth)acrylate.

[0064] The solubility parameter (SP value) of the acrylic polymer for the pressure-sensitive adhesive layer is not particularly limited, and may be the same as the solubility parameter (SP value) of the acrylic polymer for the heat-sensitive adhesive layer.

[0065] The weight average molecular weight (Mw) of the acrylic polymer for the pressure-sensitive adhesive layer is not particularly limited, and may be the same as the weight average molecular weight (Mw) of the acrylic polymer for the heat-sensitive adhesive layer.

[0066] The method for preparing the acrylic polymer for the pressure-sensitive adhesive layer is not particularly limited, and examples thereof include a method in which a monomer from which the structural unit is derived is subjected to a radical reaction in the presence of a polymerization initiator, as in the case of the acrylic polymer for the heat-sensitive adhesive layer.

[0067] The pressure-sensitive adhesive layer preferably further contains a tackifier resin. By including the tackifier resin in the pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive layer is improved. The tackifier resin is not particularly limited, and the same tackifier resin as the tackifier resin used in the heat-sensitive adhesive layer can be used. The content of the tackifier resin is not particularly limited, but a preferred lower limit is 3 parts by weight, a preferred upper limit is 50 parts by weight, a more preferred lower limit is 10 parts by weight, and a more preferred upper limit is 35 parts by weight, per 100 parts by weight of the acrylic polymer for the pressure-sensitive adhesive layer. When the content of the tackifier resin is within the above range, the adhesive strength of the pressure-sensitive adhesive layer is improved.

[0068] The pressure-sensitive adhesive layer may contain a silane coupling agent. The silane coupling agent is not particularly limited, and the same silane coupling agent as that used in the heat-sensitive adhesive layer can be used. The content of the silane coupling agent is also not particularly limited, and the same content as that in the heat-sensitive adhesive layer can be used.

[0069] The pressure-sensitive adhesive layer may further contain a crosslinking agent. When the pressure-sensitive adhesive layer contains the crosslinking agent, crosslinking between the acrylic polymers for the pressure-sensitive adhesive layer can be achieved when the acrylic polymer for the pressure-sensitive adhesive layer contains a structural unit derived from the monomer having a crosslinkable functional group. The crosslinking agent is not particularly limited, and the same crosslinking agent as that used in the heat-sensitive adhesive layer can be used, with epoxy-based crosslinking agents being more preferred. The content of the crosslinking agent is also not particularly limited, and the same content as that in the heat-sensitive adhesive layer can be used.

[0070] The pressure-sensitive adhesive layer may contain additives such as plasticizers, emulsifiers, softeners, fillers, pigments, and dyes, as well as other resins, if necessary.

[0071] The gel fraction of the pressure-sensitive adhesive layer is not particularly limited and may be the same as that of the heat-sensitive adhesive layer, preferably 50% by weight or more. The thickness of the pressure-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 0.1 μm and a preferred upper limit is 30 μm. If the thickness of the pressure-sensitive adhesive layer is within the above range, the anchoring property between the substrate and the heat-sensitive adhesive layer is further improved. The more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 5 μm and a more preferred upper limit is 20 μm.

[0072] As described above, one aspect of the present invention is a single-sided pressure-sensitive adhesive tape having a substrate and a heat-sensitive adhesive layer laminated on one side of the substrate, with the substrate having a metal layer on at least the surface opposite the heat-sensitive adhesive layer. However, if the relationship between the heat-sensitive adhesive layer and the metal layer is replaced with the relationship between the substrate, the heat-sensitive adhesive layer, and the metal layer, the single-sided pressure-sensitive adhesive tape of the present invention can be any tape in which the metal layer, as a component of the substrate, is disposed on the surface opposite the heat-sensitive adhesive layer. That is, another aspect of the present invention is a single-sided pressure-sensitive adhesive tape having a metal layer on one side and a heat-sensitive adhesive layer on the other side, wherein the heat-sensitive adhesive layer has a static friction coefficient of 5 or less against SUS. Even with this alternative aspect, a single-sided pressure-sensitive adhesive tape that is less likely to wrinkle when attached to a thin adherend and has excellent resistance to strong alkaline solutions can be achieved.

[0073] The method for producing the single-sided pressure-sensitive adhesive tape of the present invention is not particularly limited, and examples thereof include a method in which an adhesive solution is prepared by blending an acrylic polymer, a tackifying resin, a silane coupling agent, a crosslinking agent, etc., and this adhesive solution is then coated on a release-treated PET film, followed by drying to form a heat-sensitive adhesive layer, and this heat-sensitive adhesive layer is then transferred to a substrate.

[0074] The use of the single-sided pressure-sensitive adhesive tape of the present invention is not particularly limited. However, because it is less likely to wrinkle when applied to a thin substrate and has excellent resistance to strong alkaline solutions, it can be suitably used in the production of printed wiring boards. In particular, the single-sided pressure-sensitive adhesive tape of the present invention is particularly suitable for use in protecting the edges of metal-clad laminates by applying it to the edges of the metal-clad laminates during etching, desmearing, or electroless plating. More specifically, the single-sided pressure-sensitive adhesive tape of the present invention can be applied to the edges of metal-clad laminates, particularly those with thin thicknesses (specifically, thicknesses of 100 μm or less, preferably around 20 to 50 μm, and particularly around 30 to 40 μm), to protect the edges of the metal-clad laminates. After the process is completed, the area of ​​the metal-clad laminate protected by the single-sided pressure-sensitive adhesive tape can be separated (removed) by trimming it.

[0075] The method for protecting the edge of a metal-clad laminate by applying the single-sided adhesive tape of the present invention to the edge of the metal-clad laminate is not particularly limited, and examples thereof include a method of using a press to heat and press the single-sided adhesive tape to the edge of the metal-clad laminate. Heat and pressure bonding conditions that can be used include a temperature of 80 to 120°C, a pressure of 0.1 to 5 MPa, and a time of 30 to 300 seconds. When applying the single-sided adhesive tape to the square corners of the metal-clad laminate, the single-sided adhesive tape may be applied overlapping or non-overlapping.

[0076] Figures 1 to 8 are cross-sectional views schematically illustrating examples of a state in which the edge of a metal-clad laminate is protected using the single-sided adhesive tape of the present invention. In the edge-protected metal-clad laminate 1 shown in Figures 1 to 4, a single-sided adhesive tape 30 having a substrate 31 and a heat-sensitive adhesive layer 32 is used. In Figures 1 to 4, the single-sided adhesive tape 30 is folded (bent) so as to span from the front surface to the back surface of the metal-clad laminate 2 and attached to the edge of the metal-clad laminate 2. Furthermore, in Figure 4, the entire back surface of the metal-clad laminate 2 is covered with the single-sided adhesive tape 30. In the edge-protected metal-clad laminate 1 shown in Figures 5 to 7, a single-sided adhesive tape 30 having a substrate 31 and a heat-sensitive adhesive layer 32, and a single-sided adhesive tape 30' having a substrate 31' and a heat-sensitive adhesive layer 32' are used. In the edge-protected metal-clad laminate 1 shown in Figure 8, a single-sided adhesive tape 30 having a substrate 31 and a heat-sensitive adhesive layer 32, a single-sided adhesive tape 30' having a substrate 31' and a heat-sensitive adhesive layer 32', and a single-sided adhesive tape 30'' having a substrate 31'' and a heat-sensitive adhesive layer 32'' are used.

[0077] In Figures 2 to 8, 3a indicates the interface between the heat-sensitive adhesive layers, and by minimizing gaps at this interface 3a as much as possible, damage to the ends of the metal-clad laminate 2 can be further suppressed, and even when exposed to a strong alkaline solution, penetration of the solution into the ends can be further suppressed.

[0078] According to the present invention, it is possible to provide a single-sided pressure-sensitive adhesive tape that is less likely to wrinkle even when attached to a thin adherend and that has excellent resistance to strong alkaline solutions.

[0079] FIG. 1 is a cross-sectional view schematically showing an example of a state in which an edge of a metal-clad laminate is protected using the single-sided pressure-sensitive adhesive tape of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a state in which an edge of a metal-clad laminate is protected using the single-sided pressure-sensitive adhesive tape of the present invention. FIG. 3 is a cross-sectional view schematically showing an example of a state in which an edge of a metal-clad laminate is protected using the single-sided pressure-sensitive adhesive tape of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of a state in which an edge of a metal-clad laminate is protected using the single-sided pressure-sensitive adhesive tape of the present invention. FIG. 5 is a cross-sectional view schematically showing an example of a state in which an edge of a metal-clad laminate is protected using the single-sided pressure-sensitive adhesive tape of the present invention. FIG. 6 is a cross-sectional view schematically showing an example of a state in which an edge of a metal-clad laminate is protected using the single-sided pressure-sensitive adhesive tape of the present invention.

[0080] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0081] The tackifying resins used in the examples and comparative examples are as follows: Hydrogenated rosin ester resin (KE-359, manufactured by Arakawa Chemical Industries, Ltd., softening point 100°C, hydroxyl value 42 mgKOH / g) Hydrogenated rosin ester resin (KE-311, manufactured by Arakawa Chemical Industries, Ltd., softening point 100°C, hydroxyl value 8 mgKOH / g) Hydrogenated rosin ester resin (Ester Gum H, manufactured by Arakawa Chemical Industries, Ltd., softening point 68°C, hydroxyl value 29 mgKOH / g) Disproportionated rosin ester resin (KE-100, manufactured by Arakawa Chemical Industries, Ltd., softening point 100°C, hydroxyl value 6 mgKOH / g) Disproportionated rosin ester resin (A-100, manufactured by Arakawa Chemical Industries, Ltd., softening point 100°C, hydroxyl value 16 mgKOH / g) Polymerized rosin ester resin (manufactured by Arakawa Chemical Industries, Ltd., D-135, softening point 135°C, hydroxyl value 45 mgKOH / g)

[0082] Example 1 (1) Preparation of Acrylic Polymer Ethyl acetate was added as a polymerization solvent to a reaction vessel, and after bubbling with nitrogen, the reaction vessel was heated while injecting nitrogen to initiate reflux. Subsequently, a polymerization initiator solution prepared by diluting 0.3 parts by weight of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was added to the reaction vessel, and a total of 100 parts by weight of monomers having the composition shown in Table 1 was added dropwise over 2 hours. After completion of the dropwise addition, a polymerization initiator solution prepared by diluting 0.3 parts by weight of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was again added to the reaction vessel, and a polymerization reaction was carried out for 4 hours to obtain an acrylic polymer-containing solution. The solubility parameter (SP value) of the obtained acrylic polymer was determined. Furthermore, the weight average molecular weight (Mw) of the obtained acrylic polymer, calculated in terms of polystyrene, was determined by gel permeation chromatography using a GPC LF-804 (Showa Denko KK) column.

[0083] (2) Production of Single-Sided Pressure-Sensitive Adhesive Tape To the obtained acrylic polymer-containing solution, 1 part by weight of a silane coupling agent (KBM803, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.3 parts by weight (solids ratio) of a crosslinker (epoxy-based crosslinker, Tetrad C, manufactured by Mitsubishi Gas Chemical Company, Inc.) were added per 100 parts by weight of the acrylic polymer to prepare a pressure-sensitive adhesive solution. The obtained pressure-sensitive adhesive solution was applied to a 75 μm-thick release-treated PET film (SP3000-75, manufactured by Toyo Cross Co., Ltd.) so that the thickness of the heat-sensitive adhesive layer after drying was the thickness shown in Table 1, and then dried at 110 °C for 5 minutes to form a heat-sensitive adhesive layer. This heat-sensitive adhesive layer was transferred to an electrolytic copper foil (thickness 18 μm, manufactured by Fukuda Metal Foil and Powder Co., Ltd.) as a substrate at 100 °C and aged for 48 hours at 40 °C to obtain a single-sided pressure-sensitive adhesive tape in which the substrate, heat-sensitive adhesive layer, and release-treated PET film were laminated in this order.

[0084] (3) Measurement of gel fraction 0.1 g of only the heat-sensitive adhesive layer (adhesive composition) was taken out from the single-sided adhesive tape, immersed in 50 mL of ethyl acetate, and shaken in a shaker at a temperature of 23°C and 200 rpm for 24 hours. After shaking, ethyl acetate and the adhesive composition that had absorbed the ethyl acetate and swollen were separated using a metal mesh (opening #200 mesh). The separated adhesive composition was dried at 110°C for 1 hour. The weight of the adhesive composition including the metal mesh after drying was measured, and the gel fraction was calculated using the following formula: Gel fraction (wt%) = 100 × (W １ -W ２ ) / W ０ (W ０ : initial pressure-sensitive adhesive composition weight, W １ : Weight of the pressure-sensitive adhesive composition including the metal mesh after drying, W ２ : initial weight of the metal mesh)

[0085] (4) Measurement of storage modulus G' and peak temperature of loss tangent A measurement sample consisting only of a heat-sensitive adhesive layer measuring 10 mm x 6 mm and 1 mm thick was prepared in the same manner as in the examples. The obtained measurement sample was subjected to dynamic viscoelasticity measurement from -40°C to 140°C under the conditions of a shear mode of dynamic viscoelasticity measurement, an angular frequency of 1 Hz, and a rate of 5°C / min using a dynamic viscoelasticity measurement device (IT Measurement Control Co., Ltd., DVA-200) to measure the storage modulus G' at 23°C and 100°C. Furthermore, the dynamic viscoelasticity spectrum was measured from -40°C to 140°C using a dynamic viscoelasticity measurement device (IT Measurement Control Co., Ltd., DVA-200) under the conditions of a slow heating rate shear deformation mode of 5°C / min and 1 Hz, to measure the peak temperature of the loss tangent.

[0086] (5) Measurement of static friction coefficient Using SUS304 (size 63 mm x 63 mm, weight 200 g, manufactured by Yutaka Panel Service) as a sliding piece, the static friction coefficient of the single-sided pressure-sensitive adhesive tape was measured at room temperature (23°C) and 50% humidity in accordance with JIS K 7125 under the condition of a pulling speed of 100 mm / min. Note that, as with the sliding piece, SUS304 (size 250 mm x 150 mm x thickness 1.5 mm, manufactured by Yutaka Panel Service) was used as the mating material of the sample during the measurement.

[0087] (6) Measurement of Surface Roughness Ra The arithmetic mean roughness of the heat-sensitive adhesive layer of the single-sided adhesive tape was measured according to JIS B 0601-2001, and this was taken as the surface roughness Ra.

[0088] Examples 2 and 3, Comparative Example 1 Single-sided adhesive tapes were obtained in the same manner as in Example 1, except for the changes shown in the table.

[0089] (Example 4) (1) Preparation of acrylic polymer In the same manner as in Example 1, a solution containing an acrylic polymer to be used in the heat-sensitive adhesive layer (acrylic polymer for heat-sensitive adhesive layer) and a solution containing an acrylic polymer to be used in the pressure-sensitive adhesive layer (acrylic polymer for pressure-sensitive adhesive layer) were prepared.

[0090] (2) Production of Single-Sided Pressure-Sensitive Adhesive Tape To the obtained acrylic polymer-containing solution for the heat-sensitive adhesive layer, 30 parts by weight of hydrogenated rosin ester resin (KE-359, manufactured by Arakawa Chemical Industries, Ltd., softening point 100°C, hydroxyl value 42 mgKOH / g) was added per 100 parts by weight of the acrylic polymer. Furthermore, 1 part by weight of a silane coupling agent (KBM803, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.3 parts by weight (solid component ratio) of a crosslinking agent (epoxy crosslinking agent, Tetrad C, manufactured by Mitsubishi Gas Chemical Company, Inc.) were added to prepare a pressure-sensitive adhesive solution for the heat-sensitive adhesive layer. Furthermore, to the obtained acrylic polymer-containing solution for the pressure-sensitive adhesive layer, 15 parts by weight of polymerized rosin ester resin (D-135, manufactured by Arakawa Chemical Industries, Ltd., softening point 135°C, hydroxyl value 45 mgKOH / g) was added per 100 parts by weight of the acrylic polymer. Further, 0.15 parts by weight (solid component ratio) of a crosslinking agent (epoxy crosslinking agent, Tetrad C, manufactured by Mitsubishi Gas Chemical Company, Inc.) was added to prepare an adhesive solution for the pressure-sensitive adhesive layer.

[0091] The obtained pressure-sensitive adhesive solution for the pressure-sensitive adhesive layer was coated on a 75 μm-thick release-treated PET film (manufactured by Toyo Cross Co., Ltd., SP3000-75) so that the thickness of the pressure-sensitive adhesive layer after drying would be the thickness shown in Table 1, and then dried at 110°C for 5 minutes to form a pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer was transferred to an electrolytic copper foil (thickness 18 μm, manufactured by Fukuda Metal Foil and Powder Co., Ltd.) as a substrate, and the release-treated PET film was peeled off. Thereafter, the adhesive solution for the heat-sensitive adhesive layer was coated on a 75 μm-thick release-treated PET film (manufactured by Toyo Cross Co., Ltd., SP3000-75) so that the thickness of the heat-sensitive adhesive layer after drying would be the thickness shown in Table 1, and then dried at 110°C for 5 minutes to form a heat-sensitive adhesive layer. This heat-sensitive adhesive layer was transferred to the pressure-sensitive adhesive layer at 23°C and then cured at 40°C for 48 hours to obtain a single-sided adhesive tape having a substrate, a pressure-sensitive adhesive layer, a heat-sensitive adhesive layer, and a release-treated PET film laminated in this order.

[0092] (3) Measurement of Gel Fraction Measurement was carried out in the same manner as in Example 1.

[0093] (4) Measurement of Storage Modulus G′ and Peak Temperature of Loss Tangent: Measurement was carried out in the same manner as in Example 1.

[0094] (5) Measurement of static friction coefficient Measurement was carried out in the same manner as in Example 1.

[0095] (6) Measurement of Surface Roughness Ra Measurement was carried out in the same manner as in Example 1.

[0096] (Examples 5 to 14, Comparative Examples 2 and 3) Single-sided adhesive tapes were obtained in the same manner as in Example 1, except for the changes shown in the table. In Example 5, the release-treated PET film onto which the adhesive solution for the heat-sensitive adhesive layer was applied was changed to a PET film (Type 10, manufactured by Toyo Cross Co., Ltd.), thereby changing the surface roughness Ra of the heat-sensitive adhesive layer.

[0097] <Evaluation> The single-sided pressure-sensitive adhesive tapes obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 1 to 3.

[0098] (1) Evaluation of Wrinkles During Application The obtained single-sided adhesive tape was cut into 7 mm x 80 mm pieces and applied to the edge of a copper-clad laminate (CCL) (Panasonic Corporation, R1515E, resin layer thickness 40 μm, copper foil thickness 2 μm). More specifically, the single-sided adhesive tape was applied to the edge of the copper-clad laminate (CCL) to form the coating configuration shown in FIG. 1. First, the single-sided adhesive tape was placed on one side of one side of the copper-clad laminate, with the edge of the long side of the single-sided adhesive tape positioned 3.5 mm from the edge of the copper-clad laminate, and then heated and pressed at 100°C under a pressure of 0.3 MPa for 30 seconds. Then, while pressing the unattached substrate side of the single-sided adhesive tape with a stainless steel plate, the single-sided adhesive tape was folded toward the other side of the copper-clad laminate so as not to leave a gap, and brought into contact with the other side of the copper-clad laminate, and then heated and pressed at 100°C under a pressure of 0.3 MPa for 30 seconds. The applied single-sided adhesive tape was visually inspected to check for the occurrence of wrinkles. A mark of ◯ was given if no wrinkles were present, and a mark of × was given if wrinkles were present.

[0099] (2) Evaluation of Resistance to Strong Alkaline Solution In the same manner as in "(1) Evaluation of Wrinkles Upon Application" above, test pieces were prepared by applying single-sided adhesive tape to the edge of a copper-clad laminate, and the following evaluations were carried out. Table 4 shows the conditions for electroless plating, and Table 5 shows the conditions for desmear treatment.

[0100] (2-1) Strong alkaline solution A 5 wt% aqueous sodium hydroxide solution was heated to 50°C, and the test piece was immersed for 5 minutes. After removing the test piece, the single-sided adhesive tape was peeled off from the copper-clad laminate. The resistance to strong alkaline solution was evaluated by checking the discoloration of the copper in the area of ​​the copper-clad laminate where the single-sided adhesive tape had been attached. A rating of ⊚ was given for cases where no copper discoloration was observed, a rating of ◯ was given for cases where copper discoloration was observed within 2 mm from the edge of the area where the single-sided adhesive tape had been attached, and an × was given for cases where copper discoloration was observed in an area more than 2 mm from the edge of the area where the single-sided adhesive tape had been attached.

[0101] (2-2) Desmear and Electroless Plating The test pieces were subjected to a desmear treatment under the conditions shown in Table 5, and then electroless plating was performed under the conditions shown in Table 4. After removing the test pieces, the single-sided adhesive tape was peeled off from the copper-clad laminate. Resistance to desmear and electroless plating was evaluated by checking for copper discoloration in the area of ​​the copper-clad laminate where the single-sided adhesive tape had been attached. A rating of ⊚ was given when no copper discoloration was observed, a rating of ◯ was given when copper discoloration was observed within 2 mm from the edge of the area where the single-sided adhesive tape had been attached, and an rating of × was given when copper discoloration was observed in an area more than 2 mm from the edge of the area where the single-sided adhesive tape had been attached.

[0102]

[0103]

[0104]

[0105] BA: Butyl acrylate 2-EHA: 2-ethylhexyl acrylate MMA: Methyl methacrylate BMA: Butyl methacrylate IBOA: Isobornyl acrylate IBOMA: Isobornyl methacrylate AAc: Acrylic acid HEA: 2-hydroxyethyl acrylate

[0106]

[0107]

[0108] According to the present invention, it is possible to provide a single-sided pressure-sensitive adhesive tape that is less likely to wrinkle even when attached to a thin adherend and that has excellent resistance to strong alkaline solutions.

[0109] 1 Edge-protected metal-clad laminate 2 Metal-clad laminate 30, 30', 30'' Single-sided adhesive tape 31, 31', 31'' Substrate 32, 32', 32'' Heat-sensitive adhesive layer 3a Interface between heat-sensitive adhesive layers

Claims

1. A single-sided adhesive tape having a base material and a heat-sensitive adhesive layer laminated on one surface of the base material, wherein the base material has a metal layer on at least the surface opposite to the heat-sensitive adhesive layer, the heat-sensitive adhesive layer has a static friction coefficient against SUS of 5 or less, a pressure-sensitive adhesive layer is further provided between the base material and the heat-sensitive adhesive layer, and the pressure-sensitive adhesive layer has a gel fraction of 50% by weight or more. A single-sided adhesive tape characterized by the above.

2. A single-sided adhesive tape having a base material and a heat-sensitive adhesive layer laminated on one surface of the base material, wherein the base material has a metal layer on at least the surface opposite to the heat-sensitive adhesive layer, the heat-sensitive adhesive layer has a static friction coefficient against SUS of 5 or less, a pressure-sensitive adhesive layer is further provided between the base material and the heat-sensitive adhesive layer, and the pressure-sensitive adhesive layer contains an epoxy crosslinking agent. A single-sided adhesive tape characterized by the above.

3. A single-sided adhesive tape having a base material and a heat-sensitive adhesive layer laminated on one surface of the base material, wherein the base material has a metal layer on at least the surface opposite to the heat-sensitive adhesive layer, the heat-sensitive adhesive layer has a static friction coefficient against SUS of 5 or less, and it is used for protecting the edge of a metal-clad laminate by attaching it to the edge of the metal-clad laminate in an etching process, a desmear process, or an electroless plating process. A single-sided adhesive tape characterized by the above.

4. The single-sided adhesive tape according to any one of Claims 1 to 3, wherein the metal layer is made of copper.

5. The single-sided adhesive tape according to any one of Claims 1 to 3, wherein the base material is a metal base material.

6. The single-sided adhesive tape according to Claim 5, wherein the metal base material is a copper foil.

7. The single-sided adhesive tape according to any one of Claims 1 to 3, wherein the heat-sensitive adhesive layer has a peak temperature of loss tangent measured at a measurement frequency of 1 Hz using a dynamic viscoelasticity measuring device of 40°C or more.

8. The single-sided adhesive tape according to any one of Claims 1 to 3, wherein the heat-sensitive adhesive layer has a storage elastic modulus G' at 23°C of 5 MPa or more and a storage elastic modulus G' at 100°C of 0.2 MPa or less.

9. The single-sided adhesive tape according to any one of Claims 1 to 3, wherein the heat-sensitive adhesive layer has a gel fraction of 50% by weight or more.

10. The single-sided adhesive tape according to any one of claims 1 to 3, wherein the heat-sensitive adhesive layer has a surface roughness Ra of 0.01 µm or more and 0.8 µm or less.

11. The single-sided adhesive tape according to any one of claims 1 to 3, wherein the heat-sensitive adhesive layer contains an acrylic polymer.

12. The single-sided adhesive tape according to claim 11, wherein the weight-average molecular weight of the acrylic polymer is 250,000 or more and 2,000,000 or less.

13. The single-sided adhesive tape according to claim 11, wherein the heat-sensitive adhesive layer further contains a tackifier resin.

14. The single-sided adhesive tape according to claim 13, wherein the tackifier resin has a softening point of 100°C or more.

15. The single-sided adhesive tape according to claim 13, wherein the tackifier resin has a hydroxyl value of 25 mgKOH / g or more.

16. The single-sided adhesive tape according to claim 13, wherein the content of the tackifier resin with respect to 100 parts by weight of the acrylic polymer is 5 parts by weight or more and 50 parts by weight or less.

17. The single-sided adhesive tape according to claim 11, wherein the heat-sensitive adhesive layer contains an epoxy crosslinking agent.

18. The single-sided adhesive tape according to claim 17, wherein the content of the epoxy crosslinking agent with respect to 100 parts by weight of the acrylic polymer is 0.01 part by weight or more and 10 parts by weight or less.

19. The single-sided adhesive tape according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer contains an acrylic polymer.

20. The single-sided adhesive tape according to claim 19, wherein the acrylic polymer in the pressure-sensitive adhesive layer has a structural unit derived from a monomer having a crosslinkable functional group.