Adhesive tape, method for manufacturing hard disk drive, and hard disk drive sealing structure

Abstract

The purpose of the present invention is to provide an adhesive tape having excellent barrier properties and L-shaped bending adhesion. Another purpose of the present invention is to provide a method for manufacturing a hard disk drive having excellent sealing properties even when a case is sealed from outside by using the adhesive tape. In addition, an object of the present invention is to provide a hard disk drive sealing structure that is sufficiently sealed even when the case is sealed from the outside of the case. The present invention relates to an adhesive tape having a water vapor transmission rate of 7.5 g / (m < 2 > day) or less at 40 DEG C and 90% RH, a flexural rigidity of 1.0 N mm < 2 > or less at 25 DEG C at a bending width of 2.0 mm in at least one of the MD direction and the TD direction, and a 180 DEG peel force of 5.0 N / 25 mm or more with respect to SUS at 23 DEG C.

Description

Technical Field

[0001] The present invention relates to an adhesive tape, a method for manufacturing a hard disk drive using the adhesive tape, and a sealing structure for a hard disk drive. Background Art

[0002] Adhesive tapes, which consist of a base material with an adhesive layer (pressure-sensitive adhesive layer), are widely used for various purposes, such as bonding, fixing, protection, and sealing. Adhesive tapes are also used in electronic devices, for example, to airtightly seal the interior of magnetic disk devices. Patent Documents 1 to 4 are examples of prior art that disclose adhesive tapes suitable for use in such electronic devices.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-163368

[0006] Patent Document 2: International Publication No. 2021 / 106997

[0007] Patent Document 3: International Publication No. 2020 / 218430

[0008] Patent Document 4: Japanese Patent Application Laid-Open No. 04-053841 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] Traditionally, during the manufacturing process of hard disk drives (hereinafter referred to as "HDDs"), gaskets (sealants) were installed to seal helium within the casing. However, as the number of disks (magnetically coated disks) housed in the casing has increased to achieve higher capacities, creating space within the casing for gasket sealing has become difficult. Research is underway to switch from gasket sealing inside the casing to sealing with adhesive tape from the outside. Specifically, if helium could be sealed by applying adhesive tape from the outside of the casing, space within the casing could be secured, potentially increasing HDD capacity. It should be noted that in this application, the adhesive tape is typically removed after the helium filling process.

[0011] When sealing the housing from the outside with an adhesive tape, to improve sealing performance, the tape needs to be bent into an L-shape and attached to the housing (L-shaped bend adhesion). Furthermore, to achieve high productivity, it is desirable to apply the tape to one surface of the housing, then press a mold to bend the tape and attach it, thereby sealing the housing in one go.

[0012] Furthermore, in recent years, research has been underway into magnetic disk devices employing HAMR (Heat-Assisted Magnetic Recording) to further increase capacity. Briefly, HAMR utilizes a laser beam to increase areal recording density. However, the presence of moisture within the system can lead to laser attenuation, negatively impacting write life. Therefore, HAMR requires minimizing the intrusion of moisture from the outside.

[0013] The present invention aims to provide an adhesive tape having excellent barrier properties and L-shaped bend adhesion. Furthermore, the present invention aims to provide a method for manufacturing a hard disk drive that exhibits excellent sealing properties even when the housing is sealed from the outside using the adhesive tape. Furthermore, the present invention aims to provide a hard disk drive sealing structure that is sufficiently sealed even when the housing is sealed from the outside.

[0014] Means for solving problems

[0015] The present disclosure 1 relates to an adhesive tape having a water vapor transmission rate of 7.5 g / (m 2 ·day) or less, in at least one of the MD direction and the TD direction, the bending rigidity of the adhesive tape at 25°C with a bending width of 2.0 mm is 1.0 N·mm 2 The adhesive tape has a 180° peel strength against SUS at 23° C. of 5.0 N / 25 mm or more.

[0016] Disclosure 2 relates to the adhesive tape of Disclosure 1, wherein the adhesive tape has a bending rigidity of 0.45 N·mm at 25° C. in at least one of the MD direction and the TD direction. 2 the following.

[0017] Disclosure 3 relates to the adhesive tape of Disclosure 1 or 2, wherein the adhesive tape has a 10% heat shrinkage temperature of 95° C. or lower in at least one of the MD direction and the TD direction.

[0018] Disclosure 4 relates to the adhesive tape of Disclosure 1, 2 or 3, wherein the adhesive tape has two or more layers, the two or more layers include at least a first substrate layer and a first adhesive layer, and all of the two or more layers of the adhesive tape satisfy that the product of the tensile storage modulus and the thickness at 25°C is not more than 200 MPa·mm.

[0019] Disclosure 5 relates to the adhesive tape of Disclosure 4, wherein the water vapor permeability of the first substrate layer at 40° C. and 90% RH is 40 g / (m 2 ·day) or less.

[0020] This disclosure 6 relates to the pressure-sensitive adhesive tape according to this disclosure 4 or 5, wherein the first substrate layer contains a foam.

[0021] Disclosure 7 relates to the pressure-sensitive adhesive tape of Disclosure 6, wherein the foam comprises a polyolefin foam.

[0022] Disclosure 8 relates to the pressure-sensitive adhesive tape of Disclosure 4, 5, 6, or 7, wherein the 10% heat shrinkage temperature of the first base layer in at least one of the MD direction and the TD direction is 95° C. or lower.

[0023] Disclosure 9 relates to the pressure-sensitive adhesive tape of Disclosure 8, wherein the 10% heat shrinkage temperature of the first base layer in the MD direction and the TD direction is 95° C. or lower.

[0024] Disclosure 10 relates to the adhesive tape of Disclosure 4, 5, 6, 7, 8 or 9, wherein the adhesive tape comprises the first substrate layer, the first adhesive layer, the second substrate layer and the second adhesive layer in this order, the first substrate layer contains a foam, and the water vapor permeability of the first substrate layer at 40°C and 90% RH is 40 g / (m 2 ·day) or less, the first substrate layer satisfies that the product of the average value of the tensile storage modulus at 25°C in the MD and TD directions and the thickness is 50 MPa·mm or less, and in at least one direction of the MD and TD directions, the 10% thermal shrinkage temperature of the second substrate layer is 95°C or less.

[0025] Disclosure 11 relates to the adhesive tape of Disclosure 4, 5, 6, 7, 8, 9 or 10, further comprising an inorganic layer.

[0026] Disclosure 12 relates to the adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, which has a thickness of 0.20 mm or more.

[0027] The present disclosure 13 relates to a method for manufacturing a hard disk drive, wherein the hard disk drive has a main body portion and a cover portion having a hard disk, and the method for manufacturing the hard disk drive includes a process of sealing the hard disk drive by attaching the adhesive tape of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 to the main body portion and the cover portion.

[0028] Disclosure 14 relates to the method for manufacturing the hard disk drive of Disclosure 13, wherein, in the step of sealing the hard disk drive, the adhesive tape is bent and attached from the cover to the main body, and then the adhesive tape is heat-shrunk.

[0029] Disclosure 15 relates to a method for manufacturing a hard disk drive of Disclosure 14, wherein the main body portion includes a main body bottom portion and a main body side wall portion protruding upward from the outer peripheral edge of the main body bottom portion, the cover portion is a structure mounted on the main body side wall portion of the main body portion, and the process of sealing the hard disk drive includes: a process (I) of bending the adhesive tape and attaching it from the cover portion to the main body side wall portion; and a process (II) of heat shrinking the adhesive tape after the process (I).

[0030] Disclosure 16 relates to a method for manufacturing a hard disk drive of Disclosure 15, wherein the main body portion has a main body corner portion on the surface of the main body side wall portion on which the cover portion is installed, and the cover portion has a cover corner portion in contact with the main body corner portion, and in the above-mentioned process (I), the adhesive tape is bent and attached at least from the above-mentioned cover corner portion to the above-mentioned main body corner portion, and in the above-mentioned process (II), the portion of the adhesive tape attached from the above-mentioned cover corner portion to the above-mentioned main body corner portion is heat-shrunk.

[0031] Disclosure 17 relates to a method for manufacturing a hard disk drive of Disclosure 15 or 16, wherein, in the above-mentioned process (I), the above-mentioned cover portion is installed on the above-mentioned main body side wall portion, the above-mentioned adhesive tape is installed on the outer peripheral edge of the upper surface of the above-mentioned cover portion so that a portion of the above-mentioned adhesive tape is located outside the outer peripheral edge of the upper surface of the above-mentioned cover portion, a mold including a mold bottom and a mold side wall portion protruding downward from the outer peripheral edge of the mold bottom is pressed in a manner such that the upper surface of the above-mentioned cover portion and the lower surface of the above-mentioned mold bottom are opposite to each other, the above-mentioned adhesive tape is bent in a manner such that a portion of the above-mentioned adhesive tape that is not in contact with the upper surface of the above-mentioned cover portion is located between the above-mentioned mold side wall portion and the above-mentioned main body side wall portion, and the above-mentioned adhesive tape is attached to the above-mentioned main body side wall portion, thereby bonding the above-mentioned main body portion and the above-mentioned cover portion.

[0032] Disclosure 18 relates to the method for manufacturing a hard disk drive according to Disclosure 17, wherein the mold is heated to 35° C. or higher and 60° C. or lower when pressing the upper surface of the cover portion against the lower surface of the mold bottom.

[0033] Disclosure 19 relates to a method for manufacturing a hard disk drive of Disclosure 15, 16, 17 or 18, wherein, in the above-mentioned step (I), the above-mentioned adhesive tape is in the shape of a frame having a shape corresponding to the outer peripheral edge of the upper surface of the above-mentioned cover portion, and is installed in a manner such that the outer frame of the frame-shaped adhesive tape is located outside the outer peripheral edge of the upper surface of the above-mentioned cover portion.

[0034] Disclosure 20 relates to the method for manufacturing a hard disk drive according to Disclosure 15, 16, 17, 18 or 19, wherein in the above-mentioned step (II), the above-mentioned adhesive tape is heat-shrunk by 10% or more in at least one of the MD direction and the TD direction, and the adhesive tape is heat-shrunk at a temperature of 95° C. or less.

[0035] Disclosure 21 relates to a hard disk drive sealing structure including a main body and a cover, wherein the main body and the cover are fixed by a heat-shrunk adhesive tape.

[0036] Hereinafter, the present invention will be described in detail.

[0037] The present inventors have studied how to adjust the water vapor transmission rate, bending rigidity in at least one of the MD and TD directions, 180° peel strength against SUS, and thickness of adhesive tapes to appropriate ranges. As a result, they discovered that adhesive tapes with excellent barrier properties and L-shaped bend adhesion can be obtained, leading to the completion of the present invention.

[0038] It should be noted that in this specification, the "L-shape" mentioned above refers to a bent state, and does not only refer to a state of being bent at a right angle, but also includes a state of being bent two or more times.

[0039] The upper limit of the water vapor transmission rate of the adhesive tape of the present invention at 40°C and 90% RH is 7.5 g / m 2 ·day. The water vapor permeability of the adhesive tape of the present invention is set to 7.5 g / (m 2 The upper limit of the water vapor transmission rate of the adhesive tape of the present invention at 40°C and 90% RH is preferably 5.0 g / (m 2 ·day), the more preferred upper limit is 3.0g / (m 2 ·day), and the more preferred upper limit is 2.0g / (m 2 ·day), the upper limit of which is particularly preferred is 1.0 g / (m 2 ·day), the most preferred upper limit is 0.5g / (m 2 ·day).

[0040] The lower limit of the water vapor transmission rate of the adhesive tape of the present invention at 40°C and 90% RH is not particularly limited, but the upper and lower limits are substantially 0.1 g / (m 2 ·day) degree.

[0041] In this specification, the water vapor transmission rate at 40°C and 90% RH can be measured, for example, by measuring the water vapor transmission rate in the thickness direction of the pressure-sensitive adhesive tape under the conditions of 40°C and 90% RH using a water vapor transmission rate measuring apparatus (such as "PERMATRAN-W" manufactured by MOCON) in accordance with JIS K 7129 Method B.

[0042] Examples of methods for adjusting the water vapor permeability of the adhesive tape of the present invention at 40°C and 90% RH to the above range include adjusting the water vapor permeability of the substrate layer and adhesive layer included in the adhesive tape, which will be described later, and adding another substrate layer and adhesive layer.

[0043] The upper limit of the flexural rigidity of the adhesive tape of the present invention at 25°C with a bending width of 2.0 mm in at least one of the MD and TD directions (hereinafter sometimes simply referred to as "flexural rigidity") is 1.0 N·mm 2 By setting the bending rigidity of at least one of the MD and TD directions of the adhesive tape of the present invention to 1.0 N·mm 2 The following is the result: the bent state is easily maintained, and even when bent and attached, peeling from the adherend can be suppressed, and the obtained adhesive tape has excellent L-shaped bending adhesion. In addition, by setting the bending rigidity of at least one direction of the MD direction and the TD direction of the adhesive tape of the present invention to 1.0 N·mm 2 The preferred upper limit of the bending rigidity of the adhesive tape of the present invention in at least one of the MD and TD directions is 0.45 N·mm 2 , the more preferred upper limit is 0.30N·mm 2 .

[0044] The lower limit of the bending rigidity of the adhesive tape of the present invention in at least one of the MD and TD directions is preferably 0.003 N·mm 2 By setting the bending rigidity of the adhesive tape of the present invention in at least one of the MD and TD directions to 0.003 N·mm 2 As a result, the adhesive can be easily attached without wrinkles, and the sealing performance is improved.

[0045] The more preferred lower limit of the bending rigidity of the pressure-sensitive adhesive tape of the present invention in at least one of the MD and TD directions is 0.006 N·mm 2 , and the further preferred lower limit is 0.01N·mm 2 .

[0046] It should be noted that in this specification, the "MD direction" refers to the machine direction, i.e., the direction of flow during manufacturing, and the "TD direction" refers to the transverse direction, i.e., the direction perpendicular to the MD direction. If the direction of flow during manufacturing is unknown, the longitudinal direction of the adhesive tape is defined as the MD direction. If the adhesive tape is square and has no longitudinal direction, the direction of any side is defined as the MD direction.

[0047] The bending rigidity of the adhesive tape of the present invention is as follows Figure 1 The bending rigidity when the pressure-sensitive adhesive tape is bent with the pressure-sensitive adhesive layer on the outermost surface facing inward as shown in the right figure of FIG. 3 was calculated using the following formula (1).

[0048] [Mathematical formula 1]

[0049]

[0050] In the above formula (1), E i The tensile storage modulus (MPa) of the i-th layer from the innermost outer surface at 25°C. i represents the interfacial moment of inertia of the i-th layer from the outermost surface (Japanese original: cross-sectional quadratic moment) (mm 4 ), b represents the bending width (mm), h i represents the total thickness (mm) of the i-th layer from the innermost outermost layer, and λ represents the distance (mm) from the neutral axis of the pressure-sensitive adhesive tape to the outermost surface calculated according to the following formula (2).

[0051] [Mathematical formula 2]

[0052]

[0053] In the above formula (2), E i The tensile storage modulus (MPa) of the i-th layer from the innermost outer surface at 25°C, h i The total thickness (mm) of the layer from the innermost surface to the i-th layer is t i Indicates the thickness (mm) of the i-th layer from the innermost surface.

[0054] As methods for adjusting the bending rigidity of the adhesive tape of the present invention to the above-mentioned range, for example, there can be cited: a method of using an adhesive tape having a substrate and adjusting the thickness of the adhesive tape; a method of adjusting the tensile storage modulus of each layer such as the substrate layer and the adhesive layer constituting the adhesive tape; a method of changing the thickness of each layer constituting the adhesive tape; a method of changing the stacking order of each layer constituting the adhesive tape, etc.

[0055] The lower limit of the 180° peel strength of the adhesive tape of the present invention against SUS at 23°C (hereinafter sometimes referred to as "180° peel strength") is 5.0 N / 25 mm. By having a 180° peel strength of 5.0 N / 25 mm or greater, the resulting adhesive tape exhibits high adhesive strength and improved L-shaped bend adhesion. The lower limit of the 180° peel strength of the adhesive tape of the present invention is preferably 7.0 N / 25 mm, and more preferably 9.0 N / 25 mm.

[0056] Furthermore, the preferred upper limit of the 180° peel strength of the adhesive tape of the present invention is 30 N / 25 mm. By setting the 180° peel strength of the adhesive tape of the present invention to 30 N / 25 mm or less, the resulting adhesive tape exhibits improved removability, making it more suitable for use in the HDD manufacturing method described below. The more preferred upper limit of the 180° peel strength of the adhesive tape of the present invention is 20 N / 25 mm, and even more preferably 10 N / 25 mm.

[0057] The 180° peel strength of the pressure-sensitive adhesive tape of the present invention with respect to SUS at 23° C. can be measured, for example, by the following method.

[0058] Specifically, the adhesive tape was cut into a flat rectangular shape measuring 25 mm wide by 150 mm long. The tape was then pressed against a SUS304 plate with a surface finish of 2B specified in JIS G 4305 (cleaned with ethanol and then dry-rubbed) using a 2 kg rubber roller at a speed of 10 mm / second twice in an environment of 23°C and 50% RH. Furthermore, the adhesive tape was allowed to stand for 20 minutes in an environment of 23°C and 50% RH. The adhesive tape was then peeled from the SUS plate in a 180° peel test using a tensile testing machine (e.g., Shimadzu Corporation's "AGS-X") at 23°C, 50% RH, and a peel rate of 300 mm / minute, according to JIS Z 0237. This was measured by, for example, peeling the tape from the SUS plate.

[0059] Examples of methods for adjusting the 180° peel strength of the adhesive tape of the present invention against SUS at 23° C. to the above range include: changing the adhesive in the adhesive layer; adjusting the thickness of the adhesive tape; and changing the material of the substrate layer.

[0060] The lower limit of the thickness of the adhesive tape of the present invention is 0.20 mm. A thickness of 0.20 mm or greater improves adhesion to the adherend, enabling sufficient adhesion when the adhesive tape is bent and applied by pressing a mold. This also helps ensure the barrier properties of the resulting adhesive tape. The lower limit of the thickness of the adhesive tape of the present invention is preferably 0.30 mm, and more preferably 0.40 mm.

[0061] The preferred upper limit of the thickness of the adhesive tape of the present invention is 2.4 mm. By setting the thickness of the adhesive tape of the present invention to 2.4 mm or less, the bending rigidity can be easily reduced. A more preferred upper limit of the thickness of the adhesive tape of the present invention is 1.5 mm, and an even more preferred upper limit is 1.0 mm.

[0062] It should be noted that in this specification, examples of methods for measuring thickness include: a method of measuring using a dial thickness gauge (manufactured by Mitutoyo, "ABS Digimatic Indicator", etc.); a method of photographing a cross-section of the adhesive tape using a digital microscope (manufactured by KEYENCE, "VHX-900", etc.) and measuring the thickness of each layer of the adhesive tape based on the photographed image; etc.

[0063] The adhesive tape of the present invention preferably has two or more layers. By having two or more layers, the adhesive tape of the present invention has an appropriate thickness, thereby improving adhesion to an adherend and providing more excellent barrier properties.

[0064] The two or more layers preferably include at least a first substrate layer and a first adhesive layer. The adhesive tape of the present invention having a first substrate layer and a first adhesive layer provides the resulting adhesive tape with appropriate stiffness, thereby improving L-shaped bending adhesion.

[0065] The preferred upper limit of the product of the tensile storage modulus and thickness at 25°C (hereinafter sometimes referred to as the "tensile storage modulus and thickness product") of the two or more layers of the adhesive tape of the present invention is 200 MPa·mm. By ensuring that the product of the tensile storage modulus and thickness of all two or more layers of the adhesive tape of the present invention is 200 MPa·mm or less, the resulting adhesive tape exhibits further improved flexibility and L-bend adhesion. The more preferred upper limit of the product of the tensile storage modulus and thickness is 50 MPa·mm, and even more preferably, 25 MPa·mm.

[0066] In addition, the preferred lower limit of the product of the tensile storage modulus and the thickness is not particularly limited, but the actual upper and lower limits are approximately 0.01 MPa·mm.

[0067] When the layer for which the product of the tensile storage modulus and thickness is calculated is the substrate layer, the tensile storage modulus at 25°C is the average value of the tensile storage moduli in the MD and TD directions at 25°C.

[0068] The first substrate layer preferably contains a foam. By including a foam in the first substrate layer, the first substrate layer has appropriate flexibility, thereby facilitating adjustment of the flexural rigidity of the adhesive tape of the present invention within the aforementioned range, further improving L-shaped bend adhesion. Furthermore, it facilitates adjustment of the tensile storage modulus of the first substrate, described later, within an appropriate range.

[0069] Examples of the foam include polyurethane foam, polyolefin foam, rubber foam, and acrylic foam. Among these, polyolefin foam is preferred because it allows the water vapor permeability of the first substrate layer, described later, to be easily adjusted to an appropriate range at 40°C and 90% RH, further improving the barrier properties of the resulting adhesive tape. Furthermore, the first substrate layer exhibits moderate flexibility, making it easy to adjust the bending rigidity of the resulting adhesive tape to the aforementioned range, further improving L-bend adhesion. Specifically, the foam preferably comprises polyolefin foam.

[0070] Examples of the polyolefin foam include foams containing polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, etc. Among them, foams containing polyethylene resin are preferred from the viewpoint of imparting appropriate flexibility to the first substrate layer.

[0071] Specific examples of the polyethylene resin include polyethylene resins polymerized using polymerization catalysts such as Ziegler-Natta compounds, metallocene catalysts, and chromium oxide compounds. Among them, polyethylene resins polymerized using metallocene catalysts are preferred from the viewpoint of removability due to improved strength of the polyethylene resin.

[0072] Examples of the metallocene catalyst include bis(cyclopentadienyl) metal complexes having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds. More specifically, examples include compounds in which one or more cyclopentadienyl rings or their analogs serve as ligands coordinated to a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, and platinum.

[0073] The active sites of such metallocene catalysts are uniform in properties, with each site having the same degree of activity. Polymers synthesized using metallocene catalysts have high uniformity in terms of molecular weight, molecular weight distribution, composition, and composition distribution. Therefore, when a sheet containing a polymer synthesized using a metallocene catalyst is crosslinked, the crosslinking proceeds uniformly.

[0074] Examples of the ligand include cyclic compounds such as cyclopentadienyl rings and indenyl rings. These cyclic compounds may be substituted with hydrocarbon groups, substituted hydrocarbon groups, hydrocarbon-substituted metalloid groups, and the like.

[0075] Examples of the hydrocarbon group include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, 2-ethylhexyl, n-heptyl, n-octyl, n-nonyl, and phenyl.

[0076] Furthermore, as a ligand, a compound obtained by polymerizing the above-mentioned cyclic compound in the form of an oligomer can also be used.

[0077] In addition to the π-electron unsaturated compounds, monovalent anionic ligands such as chlorine and bromine or divalent anionic chelate ligands, hydrocarbons, alcohol salts, arylamide, aryl oxide, amide, arylamide, phosphide, arylphosphide, etc. can also be used.

[0078] Examples of the metallocene catalyst containing a tetravalent transition metal and a ligand include cyclopentadienyl titanium tris(dimethylamide), methylcyclopentadienyl titanium tris(dimethylamide), bis(cyclopentadienyl)titanium dichloride, and dimethylsilyltetramethylcyclopentadienyl-tert-butylamide zirconium dichloride.

[0079] The metallocene catalyst, when combined with a specific co-catalyst (promoter), functions as a catalyst in the polymerization of various olefins. Examples of the co-catalyst include methylaluminoxane (MAO) and boron compounds. The ratio of the co-catalyst to the metallocene catalyst is preferably 100,000 to 1,000,000 molar times, and more preferably 500,000 to 5,000 molar times.

[0080] Examples of the polyethylene resin obtained by the polymerization include low-density polyethylene (density: less than 0.930 g / cm 3 ), medium density polyethylene (density: 0.930g / cm 3 Above and less than 0.942g / cm 3 ), high-density polyethylene (density: 0.942g / cm 3 above).

[0081] As the low-density polyethylene resin, linear low-density polyethylene is preferred. More preferably, the linear low-density polyethylene is obtained by copolymerizing ethylene (e.g., 75% by mass or more, preferably 90% by mass or more, relative to the total monomer amount) with a small amount of α-olefin as required.

[0082] Specific examples of the α-olefins include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Among them, α-olefins having 4 to 10 carbon atoms are preferred from the viewpoint of low tensile storage modulus and productivity.

[0083] From the viewpoint of flexibility, the density of the polyethylene resin, for example, the above-mentioned linear low-density polyethylene, is preferably 0.870 to 0.925 g / cm 3 , more preferably 0.890 to 0.925 g / cm 3, more preferably 0.910 to 0.925 g / cm 3 As the polyethylene resin, a plurality of polyethylene resins may be used, and polyethylene resins having a density outside the above-mentioned range may also be added.

[0084] Furthermore, from the viewpoint of barrier properties, it is preferred to use high-density polyethylene or to use high-density polyethylene and low-density polyethylene in combination.

[0085] Examples of the polypropylene resin include homopolypropylene and propylene-α-olefin copolymers containing 50% by mass or more of propylene. Specific examples of the α-olefins constituting the propylene-α-olefin copolymers include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Of these, α-olefins having 6 to 12 carbon atoms are preferred from the perspectives of barrier properties and productivity.

[0086] These polypropylene resins may be used alone or in combination of two or more.

[0087] The preferred lower limit of the content of the foam in the first substrate layer is 70% by mass, a more preferred lower limit is 80% by mass, and a further preferred lower limit is 90% by mass.

[0088] The first base layer may further contain additives such as a heat stabilizer, a colorant, a flame retardant, an antistatic agent, a filler, a filler having a function of improving barrier properties, and a layered clay mineral, as needed.

[0089] Furthermore, the first base layer can be cross-linked by ionizing radiation or the like.

[0090] The first substrate layer can be produced, for example, by feeding a foaming composition containing a polyethylene resin and a foaming agent into an extruder, melt-kneading the mixture, and then extruding the mixture from the extruder.

[0091] As the foaming agent, a thermally decomposable foaming agent is preferred from the viewpoint of productivity. As the thermally decomposable foaming agent, an organic foaming agent or an inorganic foaming agent can be used.

[0092] Examples of the organic foaming agent include azodicarbonamide, azodicarboxylic acid metal salts (barium azodicarboxylate, etc.), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, biureas, hydrazine derivatives such as 4,4'-oxybis(benzenesulfonylhydrazide), and p-toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonylsemicarbazide.

[0093] Examples of the inorganic foaming agent include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and anhydrous monosodium citrate.

[0094] Among them, from the viewpoint of obtaining fine bubbles, and from the viewpoint of economic efficiency and safety, azo compounds are preferred, and azodicarbonamide is more preferred.

[0095] Such thermally decomposable foaming agents may be used alone or in combination of two or more.

[0096] In order to lower the decomposition temperature of the thermally decomposable foaming agent or accelerate the decomposition rate, a decomposition temperature regulator may be added to the foamable resin composition. Examples of the decomposition temperature regulator include zinc oxide, zinc stearate, and urea.

[0097] The foamable resin composition may contain an antioxidant. Examples of the antioxidant include phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol, sulfur-based antioxidants, phosphorus-based antioxidants, and amine-based antioxidants.

[0098] The preferred lower limit of the density of the first substrate layer is 0.01 kg / m 3 The preferred upper limit is 0.8 kg / m 3 By setting the density of the first substrate layer within the above range, the resulting adhesive tape has better barrier properties and better L-shaped bending adhesion. The more preferred lower limit of the density of the first substrate layer is 0.05 kg / m 3 The more preferred upper limit is 0.6 kg / m 3 , and the further preferred lower limit is 0.1 kg / m 3 The upper limit is preferably 0.3 kg / m 3 .

[0099] The density of the first base material layer refers to the apparent density, which can be measured, for example, using an electronic densitometer using a water displacement method (eg, "EDM Series" manufactured by AS ONE Co., Ltd.) in accordance with JIS K7222.

[0100] Examples of methods for adjusting the density of the first substrate layer include adjusting the type and content of the foaming agent contained in the foaming composition and adjusting the foaming temperature.

[0101] The upper limit of the water vapor transmission rate of the first substrate layer at 40°C and 90% RH is preferably 40 g / (m 2 ·day). The water vapor permeability of the first substrate layer at 40°C and 90% RH is set to 40 g / (m 2The upper limit of the water vapor transmission rate of the first substrate layer at 40°C and 90% RH is more preferably 21 g / (m 2 ·day), and the more preferred upper limit is 1.0 g / (m 2 ·day).

[0102] The preferred lower limit of the water vapor transmission rate of the first substrate layer at 40°C and 90% RH is not particularly limited, but the actual upper and lower limits are 0.1 g / (m 2 ·day) degree.

[0103] As methods for adjusting the water vapor transmission rate of the above-mentioned first substrate layer at 40°C and 90% RH, for example, there are: a method of changing the thickness of the substrate layer; a method of changing the material of the substrate layer; a method of changing the foaming ratio when the substrate layer is a foam; a method of making the substrate layer contain an inorganic mineral; a method of laminating an inorganic layer on the substrate layer, etc.

[0104] The expansion ratio is obtained by measuring the apparent density and finding its inverse. The apparent density can be measured in accordance with JIS K 7222.

[0105] The preferred upper limit of the 10% thermal shrinkage temperature of the first substrate layer in at least one of the MD and TD directions is 95°C. By setting the 10% thermal shrinkage temperature of the first substrate layer in at least one of the MD and TD directions to 95°C or lower, the resulting adhesive tape can be more suitably used in the HDD manufacturing method described below. The more preferred upper limit of the 10% thermal shrinkage temperature of the first substrate layer in at least one of the MD and TD directions is 80°C, further preferred is 70°C, and particularly preferred is 60°C. It should be noted that the 10% thermal shrinkage temperature of the first substrate layer in both the MD and TD directions is more preferably 95°C or lower.

[0106] Furthermore, the preferred lower limit of the 10% thermal shrinkage temperature of the first substrate layer in at least one of the MD and TD directions is 40°C. By setting the 10% thermal shrinkage temperature of the first substrate layer to 40°C or higher in at least one of the MD and TD directions, the pressure-sensitive adhesive tape can be stored at room temperature. The more preferred lower limit of the 10% thermal shrinkage temperature of the first substrate layer in at least one of the MD and TD directions is 50°C, and even more preferably 60°C.

[0107] In addition, in this specification, the 10% heat shrinkage temperature can be measured by the following method.

[0108] Specifically, first, a test piece is prepared by cutting the substrate layer and adhesive tape to be measured into a flat square shape measuring 50 mm wide and 50 mm long. The resulting test piece is immersed in approximately 1 L of water preheated to 50°C for 10 seconds, then air-cooled to room temperature. The width and length of the test piece are measured, and the measured width and length are used to calculate the thermal shrinkage at 50°C in the MD and TD directions, respectively, according to the following formula (3). Similarly, the test piece is immersed in water at 60°C, 70°C, 80°C, 90°C, and 100°C. The width and length measured after cooling to room temperature are used to calculate the thermal shrinkage at 60°C, 70°C, 80°C, 90°C, and 100°C in the MD and TD directions, respectively, according to the following formula (3). Regarding the obtained thermal shrinkage rate, when the thermal shrinkage rate at 50°C exceeds 10%, the 10% thermal shrinkage temperature is set to less than 50°C. When the thermal shrinkage rate at 100°C is less than 10%, the 10% thermal shrinkage temperature is set to more than 100°C. In other cases, the 10% thermal shrinkage temperature is calculated assuming that the temperature and the thermal shrinkage rate are proportional between the maximum temperature at which the thermal shrinkage rate is less than 10% and the minimum temperature at which the thermal shrinkage rate exceeds 10%.

[0109] Thermal shrinkage (%) = [(L0-L1) / L0] × 100 (3)

[0110] (L0: Dimensions of the adhesive tape before being soaked in heated water, L1: Dimensions of the adhesive tape after being soaked in heated water and then air-cooled to room temperature)

[0111] Examples of methods for adjusting the 10% heat shrinkage temperature of the first base material layer include a method of changing the stretching ratio and a method of changing the material of the base material layer.

[0112] The preferred lower limit of the tensile storage modulus of the first substrate layer at 25°C in at least one of the MD and TD directions is 0.1 MPa, and the preferred upper limit is 200 MPa. By adjusting the tensile storage modulus of the first substrate layer at 25°C in at least one of the MD and TD directions within the above range, it is easy to adjust the product of the average tensile storage modulus of the first substrate layer in the MD and TD directions and the thickness to within the above range, further improving the L-shaped bending adhesion of the resulting adhesive tape. The more preferred lower limit of the tensile storage modulus of the first substrate layer at 25°C in at least one of the MD and TD directions is 1 MPa, the more preferred upper limit is 80 MPa, the further preferred lower limit is 5 MPa, and the further preferred upper limit is 40 MPa.

[0113] It should be noted that the tensile storage modulus of the above-mentioned first substrate layer at 25°C can be obtained by measuring using a dynamic viscoelasticity measuring apparatus (manufactured by IT Measurement and Control Co., Ltd., "DVA-200") under the following conditions: measurement mode tension, 25°C, frequency 1 Hz, heating rate 5°C / min, temperature range 0 to 100°C, and set strain 0.1%.

[0114] Examples of methods for adjusting the tensile storage modulus of the first substrate layer at 25° C. include a method of changing the expansion ratio and a method of changing the material of the substrate layer.

[0115] The preferred lower limit of the thickness of the first substrate layer is 100 μm, and the preferred upper limit is 2000 μm. By setting the thickness of the first substrate layer within this range, the resulting adhesive tape exhibits superior barrier properties and superior L-shaped bend adhesion. The more preferred lower limit of the thickness of the first substrate layer is 150 μm, the more preferred upper limit is 1000 μm, the further preferred lower limit is 200 μm, and the further preferred upper limit is 500 μm.

[0116] Examples of the first adhesive layer include adhesives such as acrylic adhesives, rubber adhesives, urethane adhesives, and silicone adhesives. Of these, acrylic adhesives are preferred because they further improve the L-shaped bend adhesion of the resulting adhesive tape. Furthermore, rubber adhesives are preferred because they facilitate lowering of the water vapor transmission rate.

[0117] The acrylic pressure-sensitive adhesive includes a (meth)acrylic copolymer.

[0118] The (meth)acrylic acid-based copolymer preferably contains an alkyl (meth)acrylate having an alkyl group having 1 to 18 carbon atoms at the ester terminal.

[0119] Examples of the alkyl (meth)acrylates having an alkyl group having 1 to 18 carbon atoms at the ester terminus include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, tridecyl methacrylate, and stearyl (meth)acrylate. Among these, n-butyl acrylate and 2-ethylhexyl acrylate are preferred due to ease of controlling adhesive strength. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0120] In addition, in this specification, "(meth)acrylic acid" means acrylic acid or methacrylic acid.

[0121] The (meth)acrylic copolymer may contain a structural unit derived from another copolymerizable polymerizable monomer as needed.

[0122] Examples of the other copolymerizable monomers include hydroxyalkyl (meth)acrylates, glycerol dimethacrylate, glycidyl (meth)acrylate, 2-methacryloyloxyethyl isocyanate, (meth)acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, and fumaric acid. Among these, functional monomers having polar functional groups such as hydroxyl groups and carboxyl groups are preferred because they can form a crosslinked structure with a crosslinking agent, thereby facilitating adjustment of the gel fraction of the first adhesive layer.

[0123] These other copolymerizable polymerizable monomers may be used alone or in combination of two or more.

[0124] The preferred lower limit of the weight-average molecular weight (Mw) of the (meth)acrylic copolymer is 300,000, and the preferred upper limit is 2,000,000. By adjusting the weight-average molecular weight of the (meth)acrylic copolymer within this range, the first adhesive layer has an appropriate hardness and sufficient cohesive force, resulting in a higher adhesive strength for the resulting adhesive tape, further improving L-shaped bend adhesion. The more preferred lower limit of the weight-average molecular weight of the (meth)acrylic copolymer is 500,000, the more preferred upper limit is 1,400,000, the even more preferred lower limit is 600,000, and the even more preferred upper limit is 1,300,000.

[0125] The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the (meth)acrylic copolymer (molecular weight distribution, Mw / Mn) preferably has a lower limit of 1.05 and an upper limit of 10.0. By keeping the molecular weight distribution (Mw / Mn) of the (meth)acrylic copolymer within this range, the content of low-molecular weight components and the like is reduced, thereby further improving the cohesive strength of the first adhesive layer and providing a high adhesive strength to the resulting adhesive tape. A more preferred lower limit of the molecular weight distribution (Mw / Mn) of the (meth)acrylic copolymer is 1.1, a more preferred upper limit is 8.0, a further preferred lower limit is 1.2, and a further preferred upper limit is 5.0.

[0126] It should be noted that in this specification, the number average molecular weight (Mn) and weight average molecular weight (Mw) refer to molecular weights calculated based on standard polystyrene based on GPC (Gel Permeation Chromatography). For example, a 2690 Separations Model (manufactured by Waters) can be used for GPC. Alternatively, a GPC apparatus (such as the "HLC-8220" manufactured by Tosoh Corporation, columns: TSK gelSurper HZM-N (4 columns)) can be used. Tetrahydrofuran can be used as the solvent, and measurement conditions, for example, can be 40°C and a flow rate of 0.5 mL / min.

[0127] In order to adjust the weight average molecular weight and molecular weight distribution (Mw / Mn) of the (meth)acrylic copolymer to the above ranges, polymerization conditions such as the polymerization initiator and the polymerization temperature may be adjusted.

[0128] To obtain the (meth)acrylic copolymer, the monomer mixture may be subjected to a free radical reaction in the presence of a polymerization initiator. Conventionally known methods, such as solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization, can be used to subject the monomer mixture to a free radical reaction. Examples of reaction methods for subjecting the monomer mixture to a free radical reaction include living radical polymerization and free radical polymerization.

[0129] Examples of the polymerization initiator include organic peroxides and azo compounds.

[0130] Examples of the organic peroxide include 1,1-bis(tert-hexylperoxy)-3,3,5-trimethylcyclohexane, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, tert-hexyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyisobutyrate, tert-butyl peroxy-3,5,5-trimethylhexanoate, and tert-butyl peroxylaurate.

[0131] The azo compound is not particularly limited as long as it is a compound commonly used in free radical polymerization. Examples of the azo compound include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis(cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl)azo]formamide, 4,4'-azobis(2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis(cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl)azo]formamide, Azobis(4-cyanovaleric acid), dimethyl-2,2'-azobis(2-methylpropionate), dimethyl-1,1'-azobis(1-cyclohexanecarboxylate), 2,2'-azobis{2-methyl-N-[1,1'-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis[N-(2- propylene)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis [2-(2-imidazolin-2-yl)propane], 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate, 2,2'-azobis(1-imino-1-pyrrolidino (Japanese original: ピロリジノ)-2-methylpropane) dihydrochloride, 2,2'-azobis(2,4,4-trimethylpentane), etc.

[0132] The polymerization initiator is not particularly limited to a polymerization initiator that initiates living radical polymerization, but is preferably an organic tellurium polymerization initiator.

[0133] These polymerization initiators may be used alone or in combination of two or more.

[0134] When the monomer mixture is subjected to a radical reaction, a dispersion stabilizer may be used. Examples of the dispersion stabilizer include polyvinyl pyrrolidone, polyvinyl alcohol, methyl cellulose, ethyl cellulose, poly(meth)acrylic acid, poly(meth)acrylate, and polyethylene glycol.

[0135] When a polymerization solvent is used when subjecting the monomer mixture to a free radical reaction, the polymerization solvent is not particularly limited. As the polymerization solvent, for example, non-polar solvents such as hexane, cyclohexane, octane, toluene, and xylene can be used. In addition, as the polymerization solvent, for example, highly polar solvents such as water, methanol, ethanol, propanol, butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, and N,N-dimethylformamide can be used. These polymerization solvents can be used alone or in combination of two or more.

[0136] The rubber-based adhesive comprises a rubber-based polymer. Examples of the rubber-based polymer include natural rubber and ABA block copolymer rubber.

[0137] Specific examples of the natural rubber include styrene-butadiene rubber, polyisoprene, polybutene (1-butene and cis- or trans-2-butene), polyisobutylene, ABA-type block copolymer rubber, and hydrogenated products thereof.

[0138] Specific examples of the ABA block copolymer rubber include styrene-butadiene-styrene block (SBS) copolymers, styrene-isoprene-styrene block (SIS) copolymers, styrene-isobutylene-styrene block copolymer rubbers, styrene-vinyl / isoprene-styrene block copolymer rubbers, styrene-ethylene-butylene-styrene block (SEBS) copolymer rubbers, which are hydrogenated products of SBS, styrene-ethylene-propylene-styrene block (SEPS) copolymer rubbers, which are hydrogenated products of SIS, and styrene-isoprene-propylene-styrene block copolymers. These rubber-based polymers may be used alone or in combination of two or more.

[0139] The rubber-based polymer preferably contains less than 20% by mass of structural units derived from styrene. By limiting the content of structural units derived from styrene in the rubber-based polymer to less than 20% by mass, outgassing caused by the resulting adhesive tape can be further reduced (particularly, the generation of gases that can reduce the durability, reliability, or operating accuracy of electronic devices such as magnetic disk devices can be suppressed). The content of structural units derived from styrene is more preferably less than 10% by mass, and it is particularly preferred that the rubber-based polymer contain no structural units derived from styrene.

[0140] The first adhesive layer preferably further contains an inorganic mineral. When the first adhesive layer contains an inorganic mineral, the barrier properties of the resulting adhesive tape are further improved.

[0141] Examples of the inorganic minerals include inorganic fillers and layered clay minerals.

[0142] Specific examples of the inorganic filler include silica fillers.

[0143] Specific examples of the layered clay mineral include montmorillonite (e.g., oleophilic montmorillonites such as Lucentite SAN316, SAN, STN, and SPN (manufactured by Co-op Chemical)) and finely divided mica (e.g., MK-300 (manufactured by Katakura & Co-op Agriculture)). These inorganic minerals may be used alone or in combination of two or more.

[0144] The preferred lower limit of the inorganic mineral content relative to 100 parts by mass of the adhesive is 10 parts by mass, and the preferred upper limit is 200 parts by mass. By setting the inorganic mineral content to 10 parts by mass or more, the barrier properties of the resulting adhesive tape are further improved. By setting the inorganic mineral content to 200 parts by mass or less, the resulting adhesive tape has higher adhesion and further improved L-shaped bend adhesion. The more preferred lower limit of the inorganic mineral content is 30 parts by mass, the more preferred upper limit is 100 parts by mass, the further preferred lower limit is 40 parts by mass, and the further preferred upper limit is 75 parts by mass.

[0145] The first adhesive layer preferably further contains a crosslinking agent. The inclusion of a crosslinking agent in the first adhesive layer forms a crosslinked structure between the main chains of the resin constituting the first adhesive layer (e.g., the (meth)acrylic copolymer, the tackifier described below, etc.), thereby enhancing the cohesive strength of the first adhesive layer. As a result, the resulting adhesive tape exhibits even higher adhesive strength and further improved L-shaped bend adhesion.

[0146] Examples of the crosslinking agent include isocyanate crosslinking agents, aziridine crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking agents. Among these, isocyanate crosslinking agents are preferred because they can easily form a crosslinked structure.

[0147] The crosslinking agent content preferably has a lower limit of 0.01 parts by mass and an upper limit of 10 parts by mass relative to 100 parts by mass of the adhesive. By adjusting the crosslinking agent content within the above range, the L-shaped bend adhesion of the resulting adhesive tape is further improved. A more preferred lower limit of the crosslinking agent content is 0.1 parts by mass, and a more preferred upper limit is 3 parts by mass.

[0148] The first adhesive layer may further contain a tackifier. When the first adhesive layer contains a tackifier, the resulting adhesive tape has higher adhesive strength and further improves L-shaped bending adhesion.

[0149] Examples of the tackifier include rosin resins, rosin ester resins, hydrogenated rosin resins, terpene resins, terpene phenol resins, coumarone-indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, C9 petroleum resins, C5-C9 copolymer petroleum resins, hydrogenated C5 petroleum resins, hydrogenated C9 petroleum resins, and hydrogenated C5-C9 copolymer petroleum resins.

[0150] Among them, hydrogenated rosin-based resins, alicyclic saturated hydrocarbon-based resins, hydrogenated C5-based petroleum resins, hydrogenated C9-based petroleum resins, and hydrogenated C5-C9 copolymer-based petroleum resins are preferred from the viewpoint of further reducing the polarity of the adhesive layer, further reducing the water vapor transmission rate at 40°C and 90% RH, and further improving the barrier properties of the resulting adhesive tape.

[0151] Furthermore, from the viewpoint of controlling the adhesive force, rosin-based resins or terpene-based resins are preferred, and rosin-based resins or terpene-based resins containing a hydroxyl group are more preferred.

[0152] These thickeners may be used alone or in combination of two or more.

[0153] The preferred lower limit of the softening temperature of the tackifier is 70°C, and the preferred upper limit is 170°C. By setting the softening temperature of the tackifier at 70°C or higher, the first adhesive layer can be prevented from becoming excessively soft. By setting the softening temperature of the tackifier at 170°C or lower, the wettability of the first adhesive layer to the adherend is enhanced. The more preferred lower limit of the softening temperature of the tackifier is 120°C, and the more preferred upper limit is 160°C.

[0154] In addition, the softening temperature means the softening temperature measured by JIS K 2207 (ring and ball method).

[0155] To improve the adhesive tape, the first adhesive layer may further contain a silane coupling agent. Examples of the silane coupling agent include epoxy silanes, acrylic silanes, methacrylic silanes, amino silanes, isocyanate silanes, vinyl silanes, and butadiene polymer-modified silanes.

[0156] The upper limit of the water vapor transmission rate of the first adhesive layer at 40°C and 90% RH is preferably 300 g / (m 2 ·day). The water vapor permeability of the first adhesive layer at 40°C and 90% RH is set to 300 g / (m 2 The upper limit of the water vapor transmission rate of the first adhesive layer at 40°C and 90% RH is more preferably 200 g / (m 2·day), and the upper limit is preferably 100g / (m 2 ·day).

[0157] The preferred lower limit of the water vapor transmission rate of the first adhesive layer at 40°C and 90% RH is not particularly limited, but the actual upper and lower limits are 10 g / (m 2 ·day) degree.

[0158] The water vapor transmission rate of the first adhesive layer at 40°C and 90% RH can be measured by laminating the adhesive layer with a 200-mesh metal mesh and measuring the water vapor transmission rate at 40°C and 90% RH using the same method as described above for measuring the water vapor transmission rate at 40°C and 90% RH on a sample of the prepared adhesive layer.

[0159] The water vapor permeability of the first adhesive layer at 40°C and 90% RH can be adjusted by the type of adhesive used in the adhesive layer and the density of the adhesive layer. For example, selecting a material with a large polarity difference from that of water vapor, i.e., water molecules, will reduce moisture permeability. Specifically, since water molecules are highly polar, selecting a material composed of low-polarity atomic groups will reduce moisture permeability. Furthermore, when the adhesive is composed of a high-molecular-weight polymer, the lower the free volume of the polymer, the lower the moisture permeability. Specifically, polymers with symmetrical side chains tend to stack easily, resulting in a smaller free volume and lower moisture permeability. Furthermore, polymers with a crystalline structure have even lower moisture permeability. Alternatively, moisture permeability can be adjusted by adjusting the free volume of the polymer, its molecular weight, hydrogen bonding properties, molecular rigidity, and crosslink density. Furthermore, when a lamellar adhesive compound (lamellar adhesive compound) that blocks the permeation of water molecules is added and dispersed in the adhesive, the compound occludes the water molecules, thereby reducing moisture permeability.

[0160] The preferred lower limit of the tensile storage modulus of the first adhesive layer at 25°C is 0.01 MPa, and the preferred upper limit is 5 MPa. By adjusting the tensile storage modulus of the first adhesive layer at 25°C within this range, it is easier to adjust the product of the tensile storage modulus and the thickness of the first adhesive layer within this range, further improving the L-shaped bending adhesion of the resulting adhesive tape. The more preferred lower limit of the tensile storage modulus of the first adhesive layer at 25°C is 0.05 MPa, the more preferred upper limit is 1 MPa, the further preferred lower limit is 0.1 MPa, and the further preferred upper limit is 0.5 MPa.

[0161] The tensile storage modulus of the first pressure-sensitive adhesive layer at 25° C. can be obtained by the following method.

[0162] Specifically, multiple PSA layers were laminated to create a 1 mm thick PSA layer for measurement. The shear storage modulus at 25°C was then measured using a dynamic viscoelasticity measuring instrument ("DVA-200," manufactured by IT Instruments & Controls Co., Ltd.) under the following conditions: shear mode, 25°C, frequency of 1 Hz, heating rate of 5°C / min, temperature range of 0-100°C, and set strain of 0.1%. The tensile storage modulus at 25°C was then determined by multiplying the obtained shear storage modulus at 25°C by three.

[0163] Examples of methods for adjusting the tensile storage modulus of the first adhesive layer at 25° C. include methods of changing the composition of the adhesive contained in the adhesive layer.

[0164] The preferred lower limit of the thickness of the first adhesive layer is 10 μm, and the preferred upper limit is 200 μm. By setting the thickness of the first adhesive layer within this range, the resulting adhesive tape exhibits superior barrier properties and superior L-shaped bend adhesion. The more preferred lower limit of the thickness of the first adhesive layer is 15 μm, the more preferred upper limit is 180 μm, the further preferred lower limit is 18 μm, and the further preferred upper limit is 150 μm.

[0165] The preferred lower limit of the gel fraction of the first adhesive layer is 1% by mass, and the preferred upper limit is 90% by mass. By making the gel fraction of the first adhesive layer 1% or more, the cohesive force of the first adhesive layer is further improved. By making the gel fraction of the first adhesive layer 90% or less by mass, it is possible to suppress the wettability of the first adhesive layer to the adherend from being excessively reduced. The more preferred lower limit of the gel fraction of the first adhesive layer is 20% by mass, the more preferred upper limit is 80% by mass, the further preferred lower limit is 30% by mass, and the further preferred upper limit is 70% by mass.

[0166] The gel fraction of the first pressure-sensitive adhesive layer can be measured, for example, by the following method.

[0167] Test pieces were prepared by cutting the adhesive tape into a flat rectangular shape measuring 50 mm x 100 mm. The test pieces were immersed in ethyl acetate at 23°C for 24 hours, removed from the ethyl acetate, and dried at 110°C for 1 hour. The mass of the dried test piece was measured, and the gel fraction and other parameters were calculated using the following formula (4). The test pieces were not laminated with a release film to protect the adhesive layer.

[0168] Gel fraction (mass %) = 100 × (W2-W0) / (W1-W0) (4)

[0169] (W0: mass of the substrate, W1: mass of the test piece before immersion, W2: mass of the test piece after immersion and drying)

[0170] The pressure-sensitive adhesive tape of the present invention may have other layers as long as the effects of the present invention are not impaired.

[0171] The adhesive tape of the present invention preferably has a structure in which a second substrate layer and a second adhesive layer are further laminated on the first adhesive layer side of a laminate comprising the first substrate layer and the first adhesive layer. That is, the adhesive tape of the present invention preferably comprises a first substrate layer, a first adhesive layer, a second substrate layer, and a second adhesive layer in this order. This structure of the adhesive tape of the present invention further improves barrier properties and L-shaped bend adhesion.

[0172] The second base layer may or may not contain a foam, but preferably contains no foam from the viewpoint of further improving the barrier properties of the resulting pressure-sensitive adhesive tape.

[0173] As the resin constituting the above-mentioned second substrate layer, for example, olefin-based thermoplastic resins, thermoplastic elastomers, acrylic resins and polyurethane-based resins can be cited. They can be used alone or in combination of two or more. In addition, in addition to these, silicone-based resins, polyvinyl chloride-based resins, styrene-based resins, polyester-based resins, polyamide-based resins, ionomer-based resins, etc. can also be used. Among them, from the viewpoint of easily adjusting the 10% heat shrinkage temperature described later to an appropriate range, it is preferred to include at least one resin selected from olefin-based thermoplastic resins and thermoplastic elastomers. In addition, from the viewpoint of further improving the barrier properties of the obtained adhesive tape, it is more preferred to include olefin-based thermoplastic resins. The resin used in the second resin sheet layer can be used alone or in combination of two or more.

[0174] The upper limit of the water vapor transmission rate of the second substrate layer at 40°C and 90% RH is preferably 100 g / (m 2 ·day). The water vapor permeability of the second base material layer at 40°C and 90% RH is set to 100 g / (m 2 The upper limit of the water vapor transmission rate of the second substrate layer at 40°C and 90% RH is more preferably 50 g / (m 2 ·day), and the more preferred upper limit is 30g / (m 2 ·day).

[0175] The preferred lower limit of the water vapor transmission rate of the second substrate layer at 40°C and 90% RH is not particularly limited, but the actual upper and lower limits are 0.1 g / (m 2 ·day).

[0176] The preferred upper limit of the 10% thermal shrinkage temperature of the second substrate layer in at least one of the MD and TD directions is 95°C. By setting the 10% thermal shrinkage temperature of the second substrate layer in at least one of the MD and TD directions to 95°C or lower, the resulting adhesive tape can be more suitably used in the HDD manufacturing method described below. The more preferred upper limit of the 10% thermal shrinkage temperature of the second substrate layer in at least one of the MD and TD directions is 75°C, an even more preferred upper limit is 65°C, and an especially preferred upper limit is 55°C. It should be noted that the 10% thermal shrinkage temperature of the second substrate layer in both the MD and TD directions is more preferably 95°C or lower.

[0177] Furthermore, the preferred lower limit of the 10% thermal shrinkage temperature of the second substrate layer in at least one of the MD and TD directions is 40°C. By setting the 10% thermal shrinkage temperature of the second substrate layer in at least one of the MD and TD directions to 40°C or higher, the pressure-sensitive adhesive tape can be stored at room temperature. The more preferred lower limit of the 10% thermal shrinkage temperature of the second substrate layer in at least one of the MD and TD directions is 50°C, and even more preferably 60°C.

[0178] The preferred lower limit of the tensile storage modulus of the second substrate layer at 25°C in at least one of the MD and TD directions is 0.1 MPa, and the preferred upper limit is 10,000 MPa. By adjusting the tensile storage modulus of the second substrate layer at 25°C in at least one of the MD and TD directions within the above range, it is easier to adjust the product of the average tensile storage modulus of the second substrate layer in the MD and TD directions and the thickness to within the above range, further improving the L-shaped bending adhesion of the resulting adhesive tape. The more preferred lower limit of the tensile storage modulus of the second substrate layer at 25°C in at least one of the MD and TD directions is 1 MPa, the more preferred upper limit is 5,000 MPa, the further preferred lower limit is 5 MPa, and the further preferred upper limit is 3,000 MPa.

[0179] The tensile storage modulus of the second base layer at 25° C. can be measured by the same method as that for the first base layer.

[0180] The preferred lower limit of the thickness of the second substrate layer is 10 μm, and the preferred upper limit is 2000 μm. By setting the thickness of the second substrate layer within this range, the resulting adhesive tape exhibits superior barrier properties and superior L-shaped bend adhesion. The more preferred lower limit of the thickness of the second substrate layer is 20 μm, the more preferred upper limit is 1000 μm, the further preferred lower limit is 25 μm, and the further preferred upper limit is 500 μm.

[0181] The second adhesive layer may be the same adhesive layer as the first adhesive layer.

[0182] The pressure-sensitive adhesive tape of the present invention preferably further comprises an inorganic layer. When the pressure-sensitive adhesive tape of the present invention comprises an inorganic layer, the barrier properties are further improved.

[0183] Examples of the inorganic layer include aluminum, silver, copper, and aluminum oxide, among which aluminum is preferred from the viewpoints of productivity and price.

[0184] The inorganic layer is preferably laminated on the surface of the second substrate layer on the second adhesive layer side. As a method for laminating the inorganic layer, for example, vapor deposition, sputtering, etc. can be cited. Among them, vapor deposition is preferred from the perspective of productivity.

[0185] Examples of a method for laminating the inorganic layer by vapor deposition include vacuum vapor deposition and the like.

[0186] Preferably, the adhesive tape of the present invention comprises the first substrate layer, the first adhesive layer, the second substrate layer, and the second adhesive layer in this order, wherein the first substrate layer contains a foam, and the water vapor permeability of the first substrate layer at 40°C and 90% RH is 40 g / (m 2 The first substrate layer satisfies the requirement that the product of the average tensile storage modulus at 25°C in the MD and TD directions and the thickness is 50 MPa·mm or less, and the second substrate layer has a 10% thermal shrinkage temperature of 95°C or less in at least one of the MD and TD directions. The pressure-sensitive adhesive tape of the present invention has such features, further improving barrier properties and L-bend adhesion, making it more suitable for use in the HDD manufacturing method described below.

[0187] The method for producing the pressure-sensitive adhesive tape of the present invention is not particularly limited, and the pressure-sensitive adhesive tape can be produced, for example, by the following method.

[0188] Specifically, an adhesive comprising a (meth)acrylic copolymer and a rubber-based polymer, optionally an inorganic mineral, a crosslinking agent, a tackifier, and a solvent are added and stirred thoroughly to prepare an adhesive solution. The prepared adhesive solution is applied to the release-treated surface of a release film with a release-treated surface using an applicator and dried at 110°C for 5 minutes to produce a laminate film (a) having a first adhesive layer formed thereon. Furthermore, the resulting laminate film (a) is overlaid with the prepared first substrate layer so that the first adhesive layer faces the prepared first substrate layer, thereby producing a laminate comprising the first substrate layer and the first adhesive layer. The release film of the resulting laminate is peeled off and applied to the prepared second substrate layer. The laminate film (b) having a second adhesive layer formed thereon is then overlaid with the second adhesive layer facing the second substrate layer in the same manner as for laminate film (a), thereby achieving a laminated and integrated structure. The laminate can then be manufactured by curing at 40°C for 2 days to obtain an adhesive tape.

[0189] The preferred upper limit of the 10% heat shrinkage temperature of the adhesive tape of the present invention in at least one of the MD and TD directions is 95°C. By setting the 10% heat shrinkage temperature of the adhesive tape of the present invention in at least one of the MD and TD directions to 95°C or lower, the adhesive tape can be more suitably used in the HDD manufacturing method described below. The more preferred upper limit of the 10% heat shrinkage temperature of the adhesive tape of the present invention in at least one of the MD and TD directions is 80°C, the further preferred upper limit is 70°C, and the particularly preferred upper limit is 60°C. It should be noted that the 10% heat shrinkage temperature of the adhesive tape of the present invention in both the MD and TD directions is more preferably 95°C or lower.

[0190] Furthermore, the preferred lower limit of the 10% thermal shrinkage temperature of the adhesive tape of the present invention in at least one of the MD and TD directions is 40°C. By setting the 10% thermal shrinkage temperature of the adhesive tape of the present invention to 40°C or higher, the adhesive tape can be stored at room temperature. The more preferred lower limit of the 10% thermal shrinkage temperature of the adhesive tape of the present invention is 50°C, and even more preferably 60°C.

[0191] The adhesive tape of the present invention can be used, for example, in electronic devices, etc. Among them, it is preferably used in hard disks mounted in electronic devices, and specifically, can be used as a sealing material around the outer periphery of a HDD casing in a gas purge environment.

[0192] The electronic device is not particularly limited, and examples thereof include mobile phones, cameras, displays, game consoles, electronic organizers, and personal computers.

[0193] As described above, the adhesive tape of the present invention has excellent barrier properties and L-shaped bending adhesion, and is therefore preferably used for temporary fixation of components mounted on electronic devices, in particular for temporary fixation to maintain a gas purge (Japanese original: ガスパージ) environment. Among them, it is more preferably used for temporary fixation of the outer periphery of a shell in which a purge gas is sealed, and more specifically, it is further preferably used for temporary fixation of the outer periphery of a hard disk shell under a gas purge environment. Here, "temporary fixation" in this specification means that the gas purge environment is maintained by fixing the outer periphery of the shell during transportation, etc., thereby suppressing the release of gas after purging, and peeling it off for use when mounted on an electronic device, etc. By using the adhesive tape of the present invention on the outer periphery of the hard disk shell, it is possible to maintain a gas purge environment even in a case where there is a height difference in the shell.

[0194] The present invention also includes a method for manufacturing an HDD, comprising a main body with a hard disk and a cover, and comprising the step of sealing the HDD by applying the adhesive tape of the present invention to the main body and the cover. The HDD manufacturing method of the present invention uses the adhesive tape of the present invention to seal gas from the exterior of the housing, thereby enabling the manufacture of high-capacity HDDs without compromising sealing performance, even when housing a large number of disks.

[0195] In the method for manufacturing an HDD of the present invention, generally, before the step of attaching the adhesive tape of the present invention to the main body and the cover to seal the HDD, the step of attaching the cover to the main body is performed.

[0196] Specifically, examples of the step of sealing the HDD using the adhesive tape include the following steps.

[0197] Specifically, a process such as the following can be employed: using an HDD having a main body and a cover, attaching the HDD cover to the main body, and then bending an adhesive tape and attaching it from the outer periphery of the HDD cover to the main body, thereby bonding the main body and cover together and sealing the outer periphery of the HDD with the adhesive tape. In particular, the process of sealing the HDD with the adhesive tape is preferably a process of bending the adhesive tape and attaching it from the cover to the main body, followed by heat shrinking the adhesive tape. By using the adhesive tape of the present invention, bending and attaching the adhesive tape to bond the cover to the main body, and heat shrinking the attached adhesive tape, excellent sealing performance is achieved even when sealing the housing from the outside.

[0198] The HDD preferably has a structure in which the main body includes a main body bottom and a main body side wall portion protruding upward from the outer periphery of the main body bottom, and the cover portion is attached to the side wall portion. This structure further improves the sealing performance of the HDD manufacturing method of the present invention.

[0199] Furthermore, the main body is preferably configured such that a main body corner portion is formed on a surface of the main body side wall portion to which the cover portion is attached, and the cover portion has a cover corner portion that contacts the main body corner portion. In the case of the HDD having such a configuration, heat shrinking of the adhesive tape, described later, is performed at the portion where the main body corner portion and the cover corner portion of the adhesive tape are bonded together. This further improves the sealing performance of the HDD manufacturing method of the present invention, thereby further enhancing the manufacturing quality of the manufactured HDD.

[0200] A schematic diagram of a preferred embodiment of the cover is shown in FIG. Figure 2 A schematic diagram of a preferred embodiment of the main body is shown in Figure 3 It should be noted that Figure 3 In the example, the hard disk is omitted.

[0201] The step of sealing the HDD in the HDD manufacturing method of the present invention preferably includes: a step (I) of folding the adhesive tape and attaching it from the lid to the main body sidewall; and a step (II) of heat shrinking the adhesive tape after step (I). By including these steps (I) and (II), the HDD manufacturing method of the present invention improves sealing performance.

[0202] In the HDD manufacturing method of the present invention, the main body preferably includes the main body corner portion, the cover preferably includes the cover corner portion, and in step (I), the adhesive tape is bent and attached to at least the main body corner portion and the cover corner portion. In step (II), the portion of the adhesive tape extending from the cover corner portion to the main body corner portion is thermally shrunk. By performing the HDD manufacturing method of the present invention in this manner, sealing performance is further improved, thereby further enhancing the manufacturing quality of the manufactured HDD.

[0203] In the above-mentioned step (I), as a method for bending the adhesive tape and attaching it from the above-mentioned cover portion to the above-mentioned main body side wall portion, for example, the following method can be cited: after the above-mentioned cover portion is installed on the above-mentioned main body side wall portion, it is installed in a manner such that a portion of the above-mentioned adhesive tape extends outward from the outer peripheral edge of the upper surface of the above-mentioned cover portion, and the extended portion is bent to attach it from the above-mentioned cover portion to the above-mentioned main body side wall portion.

[0204] Regarding the HDD manufacturing method of the present invention, it is preferred that in the above-mentioned step (I), the above-mentioned cover portion is installed on the above-mentioned main body side wall portion, an adhesive tape is installed on the outer peripheral edge of the upper surface of the above-mentioned cover portion so that a portion of the above-mentioned adhesive tape is located outside the outer peripheral edge of the upper surface of the above-mentioned cover portion, a mold including a mold bottom and a mold side wall portion protruding downward from the outer peripheral edge of the mold bottom is pressed in a manner such that the upper surface of the above-mentioned cover portion and the lower surface of the above-mentioned mold bottom are opposite to each other, the above-mentioned adhesive tape is bent in a manner such that a portion of the above-mentioned adhesive tape that is not in contact with the upper surface of the above-mentioned cover portion is located between the above-mentioned mold side wall portion and the above-mentioned main body side wall portion, and the above-mentioned adhesive tape is attached to the above-mentioned main body side wall portion, thereby bonding the above-mentioned main body portion and the above-mentioned cover portion.

[0205] By performing the HDD manufacturing method of the present invention in this manner, the entire portion of the adhesive tape located outside the outer peripheral edge of the upper surface of the cover can be easily bent simultaneously and instantly using the mold, thereby improving the simplicity of the HDD manufacturing method of the present invention.

[0206] A schematic diagram of a preferred embodiment of the mold is shown in Figure 4 . By pressing the mold 4 so that the lower surface 42 of the mold bottom of the mold 4 is opposite to the upper surface of the cover of the HDD to which the above-mentioned adhesive tape is attached, it is possible to easily bend all the parts of the above-mentioned adhesive tape attached to the above-mentioned cover so as to be located outside the outer peripheral edge of the upper surface of the above-mentioned cover. In addition, the mold side wall portion 43 of the above-mentioned mold 4 makes it easy to maintain the bent adhesive tape in an L-shape, thereby making it easier to seal the above-mentioned HDD, and further improving the sealing performance of the HDD manufacturing method of the present invention. It should be noted that the bottom of the above-mentioned mold can be a hollow structure.

[0207] A cross-sectional view schematically showing a state where the adhesive tape is bent into an L-shape using the mold and attached to the cover and the side wall of the main body is shown in FIG. Figure 5 .

[0208] When pressing the mold so that the upper surface of the lid portion faces the lower surface of the mold base, the mold is preferably heated to a temperature between 35°C and 60°C. Heating the mold to 35°C or higher facilitates bending and attaching the adhesive tape, improving the wettability of the adhesive layer and further enhancing the sealing performance of the HDD manufacturing method of the present invention. Furthermore, heating the mold to a temperature below 60°C further minimizes deterioration in the manufacturing quality of the resulting HDD. More preferably, the mold is heated to a temperature between 50°C and 60°C.

[0209] Examples of a method for heating the metal include a method of placing the mold still on a heated hot plate.

[0210] In step (I), the adhesive tape is preferably in the form of a frame having a shape corresponding to the outer periphery of the upper surface of the cover, and is preferably attached so that the outer frame of the frame-shaped adhesive tape is positioned outside the outer periphery of the upper surface of the cover. This frame-shaped adhesive tape can prevent interference with other functional components on the surface of the HDD.

[0211] Examples of a method for forming the pressure-sensitive adhesive tape into a frame shape include a method of punching the pressure-sensitive adhesive tape by pressing it with a punching blade.

[0212] In step (II), the adhesive tape is preferably thermally shrunk by 10% or more in at least one of the MD and TD directions. Thermally shrinking the adhesive tape by 10% or more in at least one of the MD and TD directions further improves the sealing performance of the HDD manufacturing method of the present invention. More preferably, the adhesive tape is thermally shrunk by 20% or more in at least one of the MD and TD directions, and even more preferably, by 30% or more. Furthermore, thermally shrinking the adhesive tape by 10% or more in both the MD and TD directions is even more preferred.

[0213] In step (II), the upper limit of the temperature of the adhesive tape during heat shrinkage is preferably 95°C. In other words, the adhesive tape is preferably heat-shrunk at a temperature of 95°C or lower. By setting the temperature of the adhesive tape during heat shrinkage to 95°C or lower, the quality of the manufactured HDD is further improved. The upper limit of the temperature of the adhesive tape during heat shrinkage is more preferably 80°C, further preferably 70°C, and particularly preferably 60°C.

[0214] Another aspect of the present invention is an HDD sealing structure comprising a main body and a cover, wherein the main body and the cover are secured with heat-shrinkable adhesive tape. The HDD sealing structure of the present invention secures the HDD from the outside using heat-shrinkable adhesive tape. Therefore, even when the HDD main body is sealed from the outside without a gasket, sufficient sealing is achieved. Consequently, even when manufacturing high-capacity HDDs with increased disk capacity, excellent manufacturing quality is maintained.

[0215] Examples of the HDD sealing structure of the present invention include a sealing structure obtained by bending an adhesive tape and attaching it from the cover to the main body side wall of the HDD using the HDD manufacturing method of the present invention, followed by heat shrinking the adhesive tape.

[0216] Effects of the Invention

[0217] According to the present invention, it is possible to provide an adhesive tape having excellent barrier properties and L-shaped bend adhesion. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a hard disk drive that exhibits excellent sealing properties even when the housing is sealed from the outside using the adhesive tape. Furthermore, according to the present invention, it is possible to provide a hard disk drive sealing structure that is sufficiently sealed even when the housing is sealed from the outside. BRIEF DESCRIPTION OF THE DRAWINGS

[0218] Figure 1 This is a schematic diagram of the model used in the calculation of bending stiffness.

[0219] Figure 2 This is a schematic diagram showing a preferred embodiment of a cover portion of an HDD device used in the manufacturing method of the present invention.

[0220] Figure 3 This is a schematic diagram showing a preferred embodiment of the main body of the HDD device used in the manufacturing method of the present invention.

[0221] Figure 4 This is a schematic diagram showing a preferred embodiment of a mold used in the production method of the present invention.

[0222] Figure 5 This is a cross-sectional view schematically showing a state in which an adhesive tape is bent into an L-shape using a mold and attached from the cover to the side wall of the main body of the HDD.

[0223] Figure 6 This is a schematic diagram showing the shape of the pressure-sensitive adhesive tape used for evaluating the peeling resistance.

[0224] Figure 7 This is a schematic diagram showing how the HDD cover is attached to the main body side wall in the evaluation of the peeling resistance.

[0225] Figure 8 This is a schematic diagram showing a state where an adhesive tape is attached to the upper surface of a cover attached to a main body side wall portion of an HDD in evaluation of peeling resistance.

[0226] Figure 9 This is a schematic diagram showing how the adhesive tape was bent into an L-shape using a mold and attached from the cover to the side wall of the main body of the HDD in the evaluation of the peeling resistance.

[0227] Figure 10 This is a schematic diagram showing the shape of the adhesive tape used in the evaluation of housing sealing properties (without corner heating). DETAILED DESCRIPTION

[0228] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0229] (Preparation of a solution containing acrylic copolymer)

[0230] Ethyl acetate was added to a reaction vessel as a polymerization solvent, and after bubbling with nitrogen, the reaction vessel was heated while nitrogen was flowing, and reflux was initiated. A polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile (a polymerization initiator) 10-fold with ethyl acetate was added to the reaction vessel. 96.9 parts by mass of n-butyl acrylate, 3 parts by mass of acrylic acid, and 0.1 parts by mass of 2-hydroxyethyl acrylate were added dropwise over 2 hours. After the dropwise addition was completed, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile (a polymerization initiator) 10-fold with ethyl acetate was again added to the reaction vessel, and a polymerization reaction was carried out for 4 hours to obtain a solution containing an acrylic copolymer.

[0231] (Preparation of Binder Solution A)

[0232] To the resulting acrylic copolymer-containing solution, 30 parts by mass of Super Ester A-125 (manufactured by Arakawa Chemical Industries, Ltd.) was added as a thickener relative to 100 parts by mass of the acrylic copolymer, followed by stirring. Furthermore, 2 parts by mass of TAKENATE D-101E (manufactured by Mitsui Chemicals, Inc.) as a crosslinking agent and ethyl acetate were added and thoroughly stirred to obtain an adhesive solution A having a solid content of 30% by mass.

[0233] (Binder solution B)

[0234] SK Dyne 2563PS (rubber-based adhesive solution, manufactured by Soken Chemical Co., Ltd.) was used as adhesive solution B as it was.

[0235] (Preparation of Binder Solution C)

[0236] To the obtained adhesive solution A, 50 parts by mass of MK-300 (Micromica, manufactured by Katakura & Co-op Agri) as an inorganic mineral was added with respect to 100 parts by mass of the acrylic copolymer and stirred to obtain an adhesive solution C.

[0237] (Preparation of Binder Solution D)

[0238] To 100 parts by mass of solid content, 5 parts by mass of Coronate HX (manufactured by Tosoh Corporation) as a crosslinking agent was added SK Dyne 2030U (acrylic adhesive solution, manufactured by Soken Chemical Co., Ltd.) and the mixture was thoroughly stirred to obtain an adhesive solution D.

[0239] (Preparation of Binder Solution E)

[0240] PSA solution E was obtained in the same manner as in the above “(Preparation of PSA solution A)” except that Super Ester A-125 as a thickener was not added to the obtained acrylic copolymer solution.

[0241] (Preparation of Binder Solution F)

[0242] To the obtained adhesive solution A, 50 parts by mass of MAE (Somasif, manufactured by Katakura & Co-op Agri) as an inorganic mineral was added with respect to 100 parts by mass of the acrylic copolymer and stirred to obtain an adhesive solution F.

[0243] (Preparation of Binder Solution G)

[0244] To the obtained adhesive solution A, 50 parts by mass of FB-5D (spherical silica, manufactured by DENKA Corporation) as an inorganic mineral was added with respect to 100 parts by mass of the acrylic copolymer and stirred to obtain an adhesive solution G.

[0245] (Preparation of Binder Solution H)

[0246] To the obtained adhesive solution A, 50 parts by mass of iM30K (hollow silica, Glass bubbles, manufactured by 3M) as an inorganic mineral was added with respect to 100 parts by mass of the acrylic copolymer and stirred to obtain an adhesive solution H.

[0247] (Example 1)

[0248] (Adhesive Tape Production)

[0249] The obtained adhesive solution A was applied to the release-treated surface of a 50 μm thick release film (SP3000, manufactured by Toyo Cloth Co., Ltd.) using an applicator and then heated and dried (110° C.) to produce a laminated film (a) having a 75 μm (0.075 mm) thick adhesive layer A as the first adhesive layer.

[0250] The resulting laminated film (a) was laminated onto a polyethylene foam ("Volara XL-H#0180015," manufactured by Sekisui Chemical Co., Ltd.) prepared as the first substrate layer, to produce a laminate. The release film of the resulting laminate was peeled off, and a polyester shrink film ("HISHIPET PX-40S," manufactured by Mitsubishi Chemical Co., Ltd.) was laminated onto the exposed surface of the adhesive layer A of the laminate as the second substrate layer. Then, using the same method as for the laminated film (a), a laminated film (b) having adhesive layer A formed thereon as the second adhesive layer was laminated so that the adhesive layer and the second substrate layer faced each other. The laminated film was then allowed to stand at 40°C for two days for curing, thereby producing an adhesive tape. All layers were laminated with their MD directions aligned. The following measurements and calculations were performed with the release film peeled off.

[0251] (Measurement of Tensile Storage Modulus of Base Material Layer at 25°C)

[0252] The first and second substrate layers were measured for their tensile storage moduli at 25°C in the MD and TD directions using a dynamic viscoelasticity measuring instrument (DVA-200, manufactured by IT Instruments & Controls Co., Ltd.) under the following conditions: tensile mode, 25°C, frequency 1 Hz, heating rate 5°C / min, temperature range 0-100°C, and set strain 0.1%. The results are shown in Table 1.

[0253] (Calculation of the Tensile Storage Modulus of the Adhesive Layer at 25°C)

[0254] The resulting PSA layers were laminated to create a 1 mm thick PSA layer for measurement. The shear storage modulus at 25°C was measured using a dynamic viscoelasticity measuring instrument (DVA-200, manufactured by IT Instruments & Controls Co., Ltd.) under the following conditions: shear mode, 25°C, frequency of 1 Hz, heating rate of 5°C / min, temperature range of 0-100°C, and set strain of 0.1%. The tensile storage modulus at 25°C was calculated by multiplying the obtained shear storage modulus at 25°C by three. The tensile storage modulus at 25°C was calculated for both the MD and TD directions, and the results are shown in Table 1.

[0255] (Measurement of water vapor transmission rate at 40°C and 90% RH)

[0256] The water vapor transmission rates of the first substrate layer, first adhesive layer, second substrate layer, second adhesive layer, and the resulting adhesive tape were measured in the thickness direction at 40°C and 90% RH using a water vapor transmission rate meter (PERMATRAN-W 1 / 50, manufactured by MOCON). For the first and second adhesive layers, the adhesive layers were laminated with a 200-mesh metal mesh to create measurement samples. The results are shown in Table 1.

[0257] (Determination of 10% thermal shrinkage temperature)

[0258] The first substrate layer, the second substrate layer, and the resulting adhesive tape were cut into a flat square shape measuring 50 mm wide and 50 mm long to prepare test pieces. The resulting test pieces were immersed in approximately 1 L of water preheated to 50°C for 10 seconds. The width and length of the test pieces, which were then air-cooled to room temperature, were measured. The heat shrinkage rates at 50°C in the MD and TD directions were calculated using the measured widths and lengths of the test pieces, respectively. Similarly, the heat shrinkage rates at 60°C, 70°C, 80°C, 90°C, and 100°C in the MD and TD directions were calculated using the following formula (3). Regarding the obtained thermal shrinkage, if the thermal shrinkage at 50°C exceeded 10%, the 10% thermal shrinkage temperature was set to less than 50°C. If the thermal shrinkage at 100°C was less than 10%, the 10% thermal shrinkage temperature was set to more than 100°C. In other cases, the 10% thermal shrinkage temperature was calculated by assuming that the temperature and the thermal shrinkage were proportional between the maximum temperature at which the thermal shrinkage was less than 10% and the minimum temperature at which the thermal shrinkage exceeded 10%. The 10% thermal shrinkage temperature was measured in both the MD and TD directions, and the results are shown in Table 1.

[0259] Thermal shrinkage (%) = [(L0-L1) / L0] × 100 (3)

[0260] (L0: Dimensions of the adhesive tape before being soaked in heated water, L1: Dimensions of the adhesive tape after being soaked in heated water and then air-cooled to room temperature)

[0261] (Calculation of Flexural Rigidity of Adhesive Tape)

[0262] The obtained adhesive tape was folded with the adhesive layer on the outermost surface facing inward, using the above-mentioned equations (1) and (2) with a bending width of 2.0 mm in both the MD and TD directions. The results are shown in Table 1.

[0263] (Measurement of 180° peel strength of adhesive tape against SUS at 23°C)

[0264] The resulting adhesive tape was cut into a flat rectangular shape measuring 25 mm wide by 150 mm long. The tape was then press-bonded to a SUS304 plate with a surface finish of 2B specified in JIS G 4305 (cleaned with ethanol and then dry-rubbed) using a 2 kg rubber roller at a speed of 10 mm / second twice at 23°C and 50% RH. After allowing the tape to stand for 20 minutes at 23°C and 50% RH, a 180° peel test was conducted using a tensile testing machine (Shimadzu Corporation, "AGS-X") at 23°C, 50% RH, and a peel rate of 300 mm / min in accordance with JIS Z 0237. The 180° peel strength of the tape against the SUS plate at 23°C was measured. The results are shown in Table 1.

[0265] (Examples 2 to 9, 12 to 14, 16 to 29, 37 to 39, Comparative Examples 1 to 5)

[0266] A pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the type of substrate layer, the type of pressure-sensitive adhesive solution, and the thickness of the pressure-sensitive adhesive layer were as shown in Tables 1 to 6. The results are shown in Tables 1 to 6.

[0267] The adhesive layers (second adhesive layers) having a thickness exceeding 0.15 mm in Examples 37 to 39 were prepared to have the thicknesses listed in Table 5 by laminating a plurality of heat-dried adhesive layers having a thickness of 0.15 mm.

[0268] (Example 10)

[0269] A 45 nm thick aluminum layer was deposited as an inorganic layer on the second adhesive layer side of the prepared HISHIPET PX-40S by vacuum deposition, and this layer served as the second substrate layer. The same procedures as in Example 1 were followed, except that the type of substrate layer, type of adhesive solution, and thickness of the adhesive layer were as shown in Table 2. Measurements and calculations were performed. The results are shown in Table 2.

[0270] (Example 11, Comparative Examples 6 and 7)

[0271] An adhesive tape was prepared in the same manner as in Example 1 except that the adhesive layer A was laminated on the first substrate layer shown in Tables 2 and 6 as the adhesive layer. Measurements and calculations were performed. The results are shown in Tables 2 and 6.

[0272] (Example 15)

[0273] In the above "(Preparation of Adhesive Tape)", a pre-cured laminate comprising a first substrate layer, a first adhesive layer, a second substrate layer, and a second adhesive layer, as shown in Table 2, and prepared in the same manner as in Example 1, was prepared. The release film protecting the second adhesive layer was removed, and a polyester shrink film ("HISHIPET LX-21S" manufactured by Mitsubishi Chemical Co., Ltd.) prepared as a third substrate layer was laminated onto the second adhesive layer such that its TD direction overlapped with the MD direction of the first and second substrate layers, and vice versa. Subsequently, a laminate film (c) having adhesive layer A formed as the third adhesive layer was laminated using the same method as for laminate film (a), with adhesive layer A facing the third substrate layer. The laminate was then allowed to stand at 40°C for two days for curing, thereby producing an adhesive tape comprising, in this order, a first substrate layer, a first adhesive layer, a second substrate layer, a second adhesive layer, a third substrate layer, and a third adhesive layer.

[0274] The measurements and calculations were performed in the same manner as in Example 1, except that the adhesive tape was produced in the above-mentioned “(Preparation of Adhesive Tape)”. The results are shown in Table 2.

[0275] (Examples 30 to 35)

[0276] The inorganic layers listed in Tables 4 and 5 were laminated onto the second adhesive layer side of the prepared HISHIPET PX-40S (Examples 30, 33-35) or Spaceclean S2600 (Examples 31 and 32), and these were used as the second substrate layer. The type of substrate layer, type of adhesive solution, and thickness of the adhesive layer were set as shown in Tables 4 and 5. Adhesive tapes were prepared in the same manner as in Example 1, and measurements and calculations were performed. The results are shown in Tables 4 and 5. The inorganic layers (Al layer (Examples 30-32), Ag layer (Example 33), and Cu layer (Example 34)) in the adhesive tapes of Examples 30-34 were formed by vacuum deposition, while the inorganic layer (Al layer) in the adhesive tape of Example 35 was formed by vacuum sputtering.

[0277] (Example 36)

[0278] A 70nm thick aluminum layer was deposited as an inorganic layer on the second adhesive layer side of the prepared Spaceclean S2600 by vacuum deposition, serving as the second substrate layer. In the "(Adhesive Tape Preparation)" section above, the pre-cured laminate comprising the first substrate layer, the first adhesive layer, the second substrate layer, and the second adhesive layer, as shown in Table 5, and prepared in the same manner as in Example 1, was prepared. The release film protecting the second adhesive layer was removed, and Spaceclean S2600, prepared as the third substrate layer, was laminated onto the second adhesive layer such that its TD direction overlapped with the MD direction of the first and second substrate layers, and vice versa. Then, using the same method as for the laminated film (a), a laminated film (c) having the adhesive layer A formed as the third adhesive layer was overlapped so that the adhesive layer A and the third substrate layer faced each other, and the laminated film was allowed to stand at 40°C for 2 days for curing, thereby obtaining an adhesive tape having, in this order, a first substrate layer, a first adhesive layer, a second substrate layer, a second adhesive layer, a third substrate layer, and a third adhesive layer.

[0279] The measurements and calculations were performed in the same manner as in Example 1, except that the adhesive tape was produced in the above-mentioned “(Preparation of Adhesive Tape)”. The results are shown in Table 5.

[0280] The types of substrates shown in Tables 1 to 6 are shown below.

[0281] Volara XL-H #0180015 (polyethylene foam, manufactured by Sekisui Chemical Co., Ltd.)

[0282] Volara XL-H #05002 (polyethylene foam, manufactured by Sekisui Chemical Co., Ltd.)

[0283] Volara XL-H #018002 (polyethylene foam, manufactured by Sekisui Chemical Co., Ltd.)

[0284] Volara XL-H #15004 (polyethylene foam, manufactured by Sekisui Chemical Co., Ltd.)

[0285] Volara XL-H #12003 (polyethylene foam, manufactured by Sekisui Chemical Co., Ltd.)

[0286] Saran Wrap (registered trademark) (polyvinylidene chloride film, manufactured by Asahi Kasei Home Products Co., Ltd.)

[0287] EMBLEM DCDCR-15 (polyvinylidene chloride-coated nylon membrane, manufactured by Unitika)

[0288] EMBLET DCKPT-12 (polyvinylidene chloride-coated polyester film, manufactured by Unitika)

[0289] Techbarrier LS (transparent silica vapor-deposited high gas barrier film, manufactured by Mitsubishi Chemical Co., Ltd.)

[0290] BR-PET1012 (aluminum-deposited polyester film, manufactured by TORAY ADVANCED FILM)

[0291] VM-CPP2203 (aluminum-deposited unstretched polypropylene film, manufactured by TORAY ADVANCED FILM)

[0292] My Foil (aluminum foil, manufactured by UACJ Foil Co., Ltd.)

[0293] PE Sheet EL (low-density polyethylene film, manufactured by Sekisui Molding Co., Ltd.)

[0294] PE Sheet EH (High-density polyethylene film, manufactured by Sekisui Forming Co., Ltd.)

[0295] HISHIPET PX-40S (polyester shrink film, manufactured by Mitsubishi Chemical Co., Ltd.)

[0296] Krehalon ML40-G (multi-layer heat shrinkable film, manufactured by Kureha Corporation)

[0297] FE2002 (manufactured by Futamura Chemical Co., Ltd., polyester film)

[0298] HISHIPET LX-21S (polyester shrink film, manufactured by Mitsubishi Chemical Co., Ltd.)

[0299] Krehalon MT500R (polyvinylidene chloride shrink film, manufactured by Kureha Corporation)

[0300] Fancywrap FL2 (polyolefin shrink film, manufactured by GUNZE)

[0301] Spaceclean S7200 (polyester shrink film, manufactured by Toyobo Co., Ltd.)

[0302] Spaceclean S2600 (polyester shrink film, manufactured by Toyobo Co., Ltd.)

[0303] Foam layer A (the foam layer obtained in the following "(Preparation of Foam Layer A)")

[0304] (Preparation of Foam Layer A)

[0305] 100 parts by mass of n-butyl acrylate and 11 parts by mass of acrylic acid were introduced into a reaction vessel to obtain a monomer component. This monomer component was dissolved in ethyl acetate, and 0.1 parts by mass of lauroyl peroxide was added as a polymerization initiator at the reflux point. The mixture was refluxed at 70°C for 5 hours to obtain a solution of an acrylic polymer with a weight-average molecular weight of 720,000. With respect to 100 parts by mass of the obtained acrylic polymer, 6.3 parts by mass of rosin ester resin P (softening point 140°C) as a tackifier, 0.054 parts by mass of M-A5DT (Soken Chemical Co., Ltd., aluminum chelate crosslinker) as a crosslinker, and 2.1 parts by mass of Expancel DU120 (Japan Fillite Co., Ltd., thermally expandable microcapsules) were added and mixed. The resulting mixture was poured into a mold and left at 120°C for 0.03 hours to obtain a foam with an expansion ratio of 1.5 cm. 3 / g, and a foam layer A having a thickness of 100 μm.

[0306] <Evaluation>

[0307] The pressure-sensitive adhesive tapes obtained in Examples and Comparative Examples were evaluated by the following methods. The results are shown in Tables 1 to 6.

[0308] (Evaluation of peeling resistance)

[0309] (1) Preparation of the evaluation shell

[0310] The obtained adhesive tape was Figure 6 Cut into a frame shape (outer frame 110 mm × 150 mm, inner frame 90 mm × 130 mm). A housing made of SUS304 with a surface 2B finish specified in JIS G 4305 was prepared, comprising a lid 31 (96 mm × 136 mm, 1 mm thick) and a main body 32. The main body 32 had the following structure: the main body bottom measured 100 mm × 140 mm and was 5 mm thick. Regarding the main body sidewalls, when viewed from the direction opposite the main body bottom, the outer frame measured 100 mm × 140 mm, the inner frame measured 90 mm × 130 mm, and the height was 22 mm thick in the vertical direction from the main body bottom, with a height difference of 2 mm from the uppermost portion of the main body (outer frame 97 mm × 137 mm, inner frame 90 mm × 130 mm). The cover 31 is sandwiched between a frame-shaped silicone rubber sheet (manufactured by ASONE Co., Ltd., "Silicon Rubber Sheet (Japanese original: シリコンゴムシート)", outer frame 94×134 mm, inner frame 92×132 mm, thickness 1 mm), as shown in FIG. Figure 7 After overlapping and installing on the main body 32, the cut adhesive tape 21 is pressed vertically on the upper surface of the cover 31 under the conditions of 23°C and 50% RH. Figure 8Then, press the mold 5 (outer frame 140mm×180mm, inner frame 60mm×100mm, thickness 9mm, with a height difference 6mm from the top of the mold (outer frame 100.6mm×140.6mm, inner frame 60mm×100mm), and circular cutouts with a diameter of 2mm at the four corners of the outer frame) heated to 60°C. Figure 9 The surface of the housing covered with the cover 31 was fitted as shown, and the adhesive tape 21 extending from the cover 31 was bent by 5 mm. The cover 31 and the main body side wall of the main body 32 were attached to produce a housing for evaluation.

[0311] (2) Confirmation of the adhesion of the edge

[0312] After the obtained evaluation housing was left at 23°C and 50% RH for 3 days, the adhesion of the edge of the attachment point between the cover 31 and the main body 32 was visually checked to evaluate the peeling resistance. However, the adhesion of the corners was not considered in this evaluation. The case where the adhesion of the edge was maintained (no peeling was observed) was marked as "○". On the other hand, if partial peeling was observed at the edge, the adhesive tape 21 extending from the cover 31 was bent 5 mm around, and the cover 31 and the main body side wall of the main body 32 were attached. The surface of the adhesive tape was immediately pressed with a hand roller to produce an evaluation housing (hereinafter also referred to as a "hand roller pressed housing"). The adhesion of the edge of the obtained hand roller pressed housing after being left at 23°C and 50% RH for 3 days was similarly checked. In the above hand roller pressed housing, the case where the adhesion of the edge was maintained was marked as "△", and the case where partial peeling was observed at the edge was marked as "×".

[0313] (Evaluation of corner sealing performance temperature)

[0314] After the "(Evaluation of Peel Resistance)" test, the temperature of the adhesive tape at the corners of the housing was raised by 5°C in increments of 5°C using a vinyl chloride welder (hot air jet) (Fuji Impulse, Inc., "NS-300"). The lowest temperature at which adhesion at the corners was visually maintained was recorded. Temperature control was performed by adjusting the output of the NS-300 and the distance between the hot air jet and the adhesive tape while measuring the temperature using a thermal imaging camera (FLIR Systems, Inc., "FLIR i60"). If the "(Evaluation of Peel Resistance)" test was negative or positive, the housing was crimped using the hand roller described above after the "(Evaluation of Peel Resistance)" test.

[0315] (Evaluation of housing sealing (without corner heating))

[0316] A small temperature and humidity recorder (Maxim, "iButton Hygrochron DS1923-F5#") was placed inside the housing to Figure 10 The shape (from Figure 6 The four corners of the shape were removed to form a 5mm×5mm square), and the same operation as in the above “(Evaluation of peeling resistance)” was performed except that the adhesive tape was cut. The shell for evaluation was produced in the same manner as in the above “(Evaluation of peeling resistance)”. The obtained shell was allowed to stand at 40°C for 1 hour and then at 65°C and 95% RH for 168 hours, and then the humidity inside the shell was measured. The case where the humidity inside the shell was less than 60% was recorded as “○”, and the case where it exceeded 60% was recorded as “×”, and the sealing property of the shell was evaluated (without heating the corners). In the case of “△” or “×” in the above “(Evaluation of peeling resistance)”, a small temperature and humidity recorder (manufactured by Maxim, “iButton Hygrochron DS1923-F5#”) was put into the shell to measure the humidity inside the shell. Figure 10 The shape (from Figure 6 The adhesive tape was cut into a shape of a 5 mm × 5 mm square with the four corners of the shape removed. Otherwise, the same operation as in the above "(Evaluation of Peel Resistance)" was performed to prepare a hand roller pressed shell, and the obtained hand roller pressed shell was used to implement this evaluation.

[0317] (Evaluation of housing sealing (with corner heating))

[0318] A small temperature and humidity recorder ("iButton Hygrochron DS1923-F5#" manufactured by Maxim) was placed inside the housing. Furthermore, the housing, to which the adhesive tape was bent and attached, was heated at any one of 75°C, 85°C, or 95°C for 10 seconds at its corner. The same procedures as in the "(Evaluation of Peel Resistance)" were followed, to produce an evaluation housing. The resulting evaluation housing was allowed to stand at 40°C for 1 hour, and then at 65°C and 95% RH for 168 hours. The humidity inside the housing was then measured. The case where the humidity inside the housing after heating the corners at 75°C was 60% or less was marked as "◎," the case where the humidity inside the housing after heating the corners at 85°C was 60% or less was marked as "○," the case where the humidity inside the housing after heating the corners at 95°C was 60% or less was marked as "△," and the case where the humidity exceeded 60% in any of the cases was marked as "×." The sealing properties of the housing (with corner heating) were evaluated. If the result in the "(Evaluation of Peel Resistance)" is "△" or "X," a small temperature and humidity recorder ("iButton Hygrochron DS1923-F5#," manufactured by Maxim Corporation) is placed inside the housing. Furthermore, the housing, formed by bending and bonding the adhesive tape, is heated at its corners for 10 seconds at either 75°C, 85°C, or 95°C. This evaluation is conducted using a hand-roller-bonded housing fabricated in the same manner as in the "(Evaluation of Peel Resistance)" above. It should be noted that even if this evaluation is "X," the adhesive tape of the present invention can be used without problems for HDD sealing.

[0319] (Evaluation of housing sealing (with corner heating, long term))

[0320] Using adhesive tapes obtained in the same manner as the adhesive tapes whose evaluation results were "◎", "○" or "△" in the above-mentioned "(Evaluation of shell sealing (with corner heating))", the heating temperature of the shell corners was set to the temperature at which the humidity inside the shell became below 60% in the above-mentioned "(Evaluation of shell sealing (with corner heating))", and the standing time in an environment of 65°C and 95%RH was changed to 336 hours. Except for this, the humidity inside the shell was measured in the same manner as in the above-mentioned "(Evaluation of shell sealing (with corner heating))". Here, the temperature at which the humidity inside the housing becomes 60% or less in the "(Evaluation of Housing Sealing Performance (with Corner Heating))" above refers to 75°C for a "◎" rating, 85°C for a "○" rating, and 95°C for a "△" rating. Housing sealing performance (with corner heating, long-term) was evaluated by denoting "◎" when the humidity inside the housing was 50% or less, "○" when it exceeded 50% but was 60% or less, and "×" when it exceeded 60%. It should be noted that even if this rating is "×," the adhesive tape of the present invention can be used for HDD sealing without any problems.

[0321] [Table 1]

[0322]

[0323] [Table 2]

[0324]

[0325] [Table 3]

[0326]

[0327] [Table 4]

[0328]

[0329] [Table 5]

[0330]

[0331] [Table 6]

[0332]

[0333] Industrial applicability

[0334] According to the present invention, it is possible to provide an adhesive tape having excellent barrier properties and L-shaped bend adhesion. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a hard disk drive that exhibits excellent sealing properties even when the housing is sealed from the outside using the adhesive tape. Furthermore, according to the present invention, it is possible to provide a hard disk drive sealing structure that is sufficiently sealed even when the housing is sealed from the outside.

[0335] Description of Reference Numerals

[0336] t n Thickness of the nth layer from the outermost surface (n = 1, 2, etc.)

[0337] h n Total thickness from the outermost layer to the nth layer (n = 1, 2, etc.)

[0338] b Bending width

[0339] λ Distance from the neutral axis of the adhesive tape to the outermost surface

[0340] 0 HDD cover

[0341] 01 Top surface

[0342] 02 Cover the corners

[0343] 1 Main body of the HDD

[0344] 11 Main body bottom

[0345] 12 Main body side wall

[0346] 13 Main body corner

[0347] 2 adhesive tape

[0348] 21 Adhesive tape used in evaluation of peel resistance

[0349] 22 Adhesive tape used for evaluating housing sealing (without corner heating)

[0350] 31 HDD cover used in the evaluation of peeling resistance

[0351] 32 Main body of HDD used in evaluation of peeling resistance

[0352] 4 Mold

[0353] 41 Upper surface of the mold bottom

[0354] 42 Lower surface of the mold bottom

[0355] 43 mold side wall

[0356] 5. Mold used in evaluation of peeling resistance

Claims

1. An adhesive tape, characterized in that: Its water vapor transmission rate at 40℃ and 90%RH is 7.5g / (m 2 day) or less, The adhesive tape has a bending rigidity of 1.0 N·mm at 25° C. in at least one of the MD and TD directions with a bending width of 2.0 mm. 2 the following, The adhesive tape has a 180° peel strength against SUS at 23° C. of 5.0 N / 25 mm or more.

2. The adhesive tape according to claim 1, wherein The adhesive tape has a bending rigidity of 0.45 N·mm at 25° C. in at least one of the MD and TD directions with a bending width of 2.0 mm. 2 the following.

3. The adhesive tape according to claim 1 or 2, wherein The adhesive tape has a 10% heat shrinkage temperature of 95° C. or lower in at least one of an MD direction and a TD direction.

4. The adhesive tape according to claim 1, 2 or 3, wherein The adhesive tape has two or more layers, The two or more layers include at least a first base material layer and a first adhesive layer, The two or more layers of the pressure-sensitive adhesive tape all satisfy a requirement that the product of the tensile storage modulus and the thickness at 25° C. is 200 MPa·mm or less.

5. The adhesive tape according to claim 4, wherein The water vapor permeability of the first substrate layer at 40°C and 90% RH is 40 g / (m 2 ·day) or less.

6. The adhesive tape according to claim 4 or 5, wherein The first base layer contains a foam.

7. The adhesive tape according to claim 6, wherein The foam comprises a polyolefin foam.

8. The adhesive tape according to claim 4, 5, 6 or 7, wherein The first base layer has a 10% heat shrinkage temperature of 95° C. or lower in at least one of the MD and TD directions.

9. The adhesive tape according to claim 8, wherein The 10% heat shrinkage temperature of the first base layer in the MD direction and the TD direction is 95° C. or lower.

10. The adhesive tape according to claim 4, 5, 6, 7, 8 or 9, wherein The adhesive tape comprises the first base layer, the first adhesive layer, the second base layer, and the second adhesive layer in this order. The first substrate layer contains a foam, The water vapor permeability of the first substrate layer at 40°C and 90% RH is 40 g / (m 2 day) or less, The first substrate layer satisfies the requirement that the product of the average value of the tensile storage modulus in the MD direction and the TD direction at 25°C and the thickness is 50 MPa·mm or less. The second base material layer has a 10% heat shrinkage temperature of 95° C. or lower in at least one of the MD direction and the TD direction.

11. The adhesive tape according to claim 4, 5, 6, 7, 8, 9 or 10, further comprising an inorganic layer.

12. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, which has a thickness of 0.20 mm or more.

13. A method for manufacturing a hard disk drive, wherein: The hard disk drive comprises a main body having a hard disk and a cover. The method for manufacturing the hard disk drive includes the step of attaching the adhesive tape according to claim 1 to the main body and the cover to seal the hard disk drive.

14. The method for manufacturing a hard disk drive according to claim 13, wherein: In the step of sealing the hard disk drive, the adhesive tape is folded and attached from the cover to the main body, and then the adhesive tape is thermally shrunk.

15. The method for manufacturing a hard disk drive according to claim 14, wherein: The main body portion includes a main body bottom portion and a main body side wall portion protruding upward from the outer peripheral edge of the main body bottom portion. The cover is a structure mounted on the side wall of the main body. The step of sealing the hard disk drive includes: a step (I) of bending the adhesive tape and attaching it from the cover to the main body side wall; and a step (II) of heat shrinking the adhesive tape after the step (I).

16. The method for manufacturing a hard disk drive according to claim 15, wherein: The main body has a main body corner portion on a surface of the main body side wall portion where the cover portion is mounted. The cover has a cover corner portion in contact with the main body corner portion, In the step (I), the adhesive tape is bent and attached at least from the lid corner to the main body corner. In the step (II), the portion of the adhesive tape attached from the lid corner to the main body corner is heat shrunk.

17. The method for manufacturing a hard disk drive according to claim 15 or 16, wherein: In the step (I), the cover is mounted on the side wall of the main body. The adhesive tape is mounted on the outer periphery of the upper surface of the cover so that a portion of the adhesive tape is located outside the outer periphery of the upper surface of the cover. The mold including the mold bottom and the mold side wall portion protruding downward from the outer peripheral edge of the mold bottom is pressed in a manner such that the upper surface of the cover portion is opposite to the lower surface of the mold bottom, the adhesive tape is bent in a manner such that the portion of the adhesive tape that is not in contact with the upper surface of the cover portion is located between the mold side wall portion and the main body side wall portion, and the adhesive tape is attached to the main body side wall portion, thereby fitting the main body portion and the cover portion.

18. The method for manufacturing a hard disk drive according to claim 17, wherein: When pressing the mold so that the upper surface of the lid portion faces the lower surface of the mold bottom, the mold is heated to 35° C. or higher and 60° C. or lower.

19. The method for manufacturing a hard disk drive according to claim 15, 16, 17 or 18, wherein: In the step (I), the adhesive tape is in a frame shape corresponding to the outer periphery of the upper surface of the cover, and is attached so that the outer frame of the frame-shaped adhesive tape is located outside the outer periphery of the upper surface of the cover.

20. The method for manufacturing a hard disk drive according to claim 15, 16, 17, 18 or 19, wherein: In the step (II), the adhesive tape is thermally shrunk by 10% or more in at least one of the MD direction and the TD direction, and the thermal shrinkage is performed at a temperature of 95° C. or lower.

21. A sealing structure for a hard disk drive, characterized in that: The invention comprises a main body and a cover, and the main body and the cover are fixed by means of a heat-shrinkable adhesive tape.

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