Foamed laminate and adhesive tape

Abstract

The foamed laminate (10) is provided with: a core layer (11) that is a foam; and a surface resin layer (12) that is provided on at least one surface of the core layer (11) and contains an organosilicon compound. The foamed laminate (10) has a static friction coefficient of 0.64 or less.

Description

Technical Field

[0001] The present invention relates to a foamed laminate as a multilayer sheet containing a foam, and an adhesive tape using the foamed laminate as a substrate. Background Technology

[0002] In electronic devices such as mobile phones, smartphones, tablets, cameras, displays, gaming devices, e-notebooks, and personal computers, foam sheets are widely used as sealing materials or impact absorbers. Previously, polyolefin resin foam sheets, obtained by foaming foaming polyolefin resin sheets containing thermally decomposable foaming agents, were known as foam sheets for these applications. These foam sheets are sometimes used inside electronic devices, for example, by coating at least one side with an adhesive to form adhesive tape. Furthermore, to impart various functions, research has been conducted on making foam sheets into multiple layers of foam, or into multilayer sheets containing both foam and non-foamed resin sheets.

[0003] On the other hand, for polyolefin resin sheets containing polyolefin resins, modifications to the composition and surface shape have been attempted to impart various functions. For example, Patent Document 1 shows that, in order to achieve excellent antifouling properties, in addition to polyolefins, a siloxane-olefin copolymer is also contained, and the arithmetic mean roughness Ra of the surface or back side is less than 0.15 μm.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-206587 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In recent years, foldable terminals, including displays, have become practical in portable electronic devices such as smartphones and tablets. However, the resin foam used in these foldable terminals sometimes slips from the display panel when bent.

[0009] However, conventional polyolefin resin foam sheets have poor sliding properties. When sliding between the foam sheet and the panel, the increased resistance causes jamming. This results in significant forces acting on the foam resin layer and adhesive tape, sometimes leading to adhesive peeling, especially when the opposite side is fixed by the adhesive layer. Furthermore, if multiple foam sheets are stacked, problems arise such as difficulty in separating the sheets, decreased productivity during foam production, and reduced productivity during overlapping and punching.

[0010] Patent document 1 shows that polyolefin resin sheets use siloxane-olefin copolymers, but does not show that the resin sheets are applied to foam sheets, nor does it suggest that the resin sheets have good sliding properties.

[0011] Therefore, the objective of this invention is to provide a resin foam that improves slip properties while maintaining the softness of the foam, resulting in good slip properties and manufacturability during use.

[0012] Methods for solving problems

[0013] The inventors conducted in-depth research and found that by preparing a foamed laminate having a core layer as a foaming body and a surface resin layer disposed on at least one side of the core layer, and by making the surface resin layer contain an organosilicon compound and making the static friction coefficient below a certain value, the above-mentioned problems can be solved, and the following invention is completed. That is, the present invention provides the following [1] to [8].

[0014] [1] A foamed laminate comprising a core layer as a foam and a surface resin layer comprising an organosilicon compound disposed on at least one side of the core layer, wherein the static friction coefficient of the foamed laminate is 0.64 or less.

[0015] [2] According to the foamed laminate described in [1] above, the static friction coefficient is 0.6 or less.

[0016] [3] The thickness of the foamed laminate as described in [1] or [2] above is 0.05~0.3 mm.

[0017] [4] In any one of the above [1] to [3] foamed laminates, the content of organosilicon compound in the above surface resin layer is 1 to 40% by mass.

[0018] [5] The foamed laminate according to any one of [1] to [4] above, wherein the surface resin layer is a foamed body or a non-foamed body.

[0019] [6] The foamed laminate according to any one of [1] to [5] above, wherein the surface resin layer comprises a polyolefin resin.

[0020] [7] The foamed laminate according to any one of [1] to [6] above, wherein the organosilicon compound is a siloxane-olefin copolymer.

[0021] [8] An adhesive tape comprising a foamed laminate as described in any one of [1] to [7] above, and an adhesive material disposed on at least one surface of the foamed laminate.

[0022] The effects of the invention

[0023] According to the present invention, a foam laminate can be provided that improves slipability while maintaining the softness of the foam body, resulting in good slippage and productivity during use. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a foamed laminate according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of a foamed laminate according to another embodiment of the present invention. Detailed Implementation

[0026] [Foamed Laminated Structure]

[0027] The foamed laminate of the present invention comprises a core layer as a foam and a surface resin layer containing an organosilicon compound disposed on at least one side of the core layer, and has a static coefficient of friction of 0.64 or less. By having the above-described structure, the foamed laminate of the present invention can improve sliding properties while maintaining the softness of the foam, resulting in good slippage and productivity during use. Furthermore, as described later, for example, when using the foamed laminate of the present invention as a substrate for adhesive tape and attaching the tape to an object such as electrical equipment, sometimes rework is performed to peel the adhesive tape from the object for reuse of the object or re-attachment of the tape. In this case, it also has the effect of suppressing breakage of the laminate and suppressing adhesive residue on the object side.

[0028] Figure 1 , 2 This illustrates a specific example of the layer composition of a foamed laminate. For example... Figure 1 As shown, the foamed laminate 10 has a surface resin layer 12 on only one side of the core layer 11, or it can be as follows: Figure 2 As shown, surface resin layers 12, 12 are provided on both sides of the core layer 11. However, from the viewpoint of easily suppressing glue residue during rework, it is preferable to provide surface resin layers 12, 12 on both sides of the core layer 11.

[0029] The foamed laminate of the present invention, by providing a core layer 11 and a surface resin layer 12, and wherein the core layer 11 is a foam, can maintain flexibility while possessing a certain tensile strength. Therefore, the foamed laminate of the present invention can be removed from the adherend by means of an adhesive tape, which is then applied to the adherend, and the core layer is cracked along the surface direction to create a so-called "mid-crack," and the remaining tape is then peeled off from the adherend. This method reduces adhesive residue during rework.

[0030] <Coefficient of static friction>

[0031] The static friction coefficient of the foamed laminate of the present invention is 0.64 or less. If the static friction coefficient exceeds 0.64, even if an organosilicon compound is mixed into the surface resin layer as described later, the sliding properties become insufficient. Therefore, when the foamed laminate is applied to foldable types and is used in a bent manner, it sometimes slips relative to the display panel or the like. In this case, the resistance increases and jamming occurs, which can sometimes lead to undesirable conditions. For example, if the surface opposite to the slipping surface is bonded to the substrate via an adhesive layer, the adhesive layer may peel off.

[0032] Furthermore, due to insufficient slippage, the foam laminates sometimes stick together when overlapped. Therefore, if the foam laminates are overlapped during production, such as during die-cutting, it becomes difficult to separate them after die-cutting, sometimes reducing productivity. Moreover, adhesion also easily occurs when the foam laminates are rolled into rolls, or when the adhesive tape described later is rolled into rolls.

[0033] From the viewpoints of ensuring good slippage during bending and use, and improving productivity, the static friction coefficient of the foamed laminate is preferably 0.6 or less, more preferably 0.55 or less, and even more preferably 0.4 or less. Furthermore, the static friction coefficient of the foamed laminate is not particularly limited, but is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.25 or more. By ensuring that the static friction coefficient of the foamed laminate is at or above a certain value, it is less likely that undesirable conditions such as excessively high slippage leading to reduced operability will occur.

[0034] It should be noted that, regarding the static friction coefficient of the foamed laminate, any surface 10A, 10A (refer to...) of the foamed laminate 10... Figure 1 , 2 The static friction coefficient of the foam laminate can be as described above, but it is preferable that the static friction coefficients of the two surfaces 10A, 10A of the foam laminate are as described above. In addition, the static friction coefficient of the surface of the foam laminate where the surface resin layer is provided can be as described above. Therefore, it is particularly preferable that the foam laminate has a surface resin layer on both sides of the foam laminate, and the static friction coefficients of the two surfaces of the surface resin layer are as described above.

[0035] It should be noted that the static friction coefficient of the foamed laminate can be appropriately adjusted by the composition of the surface resin layer and the surface state of the surface resin layer.

[0036] <Tensile Strength>

[0037] The tensile strength of the foamed laminate is preferably 1.5 to 9 MPa. With a tensile strength of 1.5 MPa or higher, when the foamed laminate and adhesive are peeled together from the substrate in an adhesive tape, the breakage of the foamed laminate and the resulting adhesive residue on the substrate can be further suppressed, resulting in better reworkability. Furthermore, with a tensile strength of 9 MPa or less, the foamed laminate can easily crack along the surface direction through a central crack, facilitating excellent reworkability. Additionally, with a tensile strength within the above range, flexibility and mechanical strength are good, and it is also easy to achieve good conformability to elevation differences and impact absorption. The tensile strength of the foamed laminate is more preferably 1.5 to 8.5 MPa, and even more preferably 1.6 to 5 MPa.

[0038] <25% compressive strength>

[0039] The 25% compressive strength of the foamed laminate of the present invention is preferably 30 to 800 kPa. By having the 25% compressive strength within this range, the foamed laminate exhibits good flexibility and mechanical strength, and readily adapts to elevation differences and provides good impact absorption. More preferably, the 25% compressive strength is 40 to 400 kPa, and even more preferably, 50 to 200 kPa.

[0040] <Thickness>

[0041] The overall thickness of the foamed laminate is preferably 0.8 mm or less. By being 0.8 mm or less, it can be used internally in thin electronic devices and the like. The overall thickness of the foamed laminate is preferably 0.5 mm or less, and more preferably 0.3 mm or less. By making the foamed laminate thinner, the difference between the inner and outer circumferences when wound into a roll is reduced, making it less prone to lateral wrinkles and improving productivity.

[0042] The overall thickness of the foamed laminate is preferably 0.05 mm or more. By having an overall thickness of 0.05 mm or more, sufficient clearance is ensured for cutting into the foamed laminate using tools or similar implements, allowing for easy cracking along the surface direction via a central crack, thus facilitating rework. Furthermore, it readily imparts a certain degree of flexibility and mechanical strength to the foamed laminate. More preferably, the overall thickness of the foamed laminate is 0.07 mm or more, and even more preferably, 0.12 mm or more.

[0043] <Glossiness>

[0044] The surface gloss of the foamed laminate is preferably 50% or higher. If the gloss is 50% or higher, the silicone compound provides sufficient gloss, easily ensuring surface smoothness. From the viewpoint of smoothness, the surface gloss of the foamed laminate of the present invention is more preferably 52% or higher, and even more preferably 54% or higher. It should be noted that the gloss is not particularly limited; for example, it may be 100% or lower, but preferably 80% or lower.

[0045] The gloss is measured according to JIS Z 8741 at an incident angle of 60°.

[0046] Regarding the gloss of the foamed laminate, the gloss of the surface with the surface resin layer is as described above. Furthermore, the gloss of the surface of the foamed laminate with the static friction coefficient set to a predetermined value is as described above. Therefore, it is particularly preferable that the foamed laminate has surface resin layers on both sides, and that the gloss of both surfaces of the surface resin layer is as described above.

[0047] [Core Layer]

[0048] The core layer of the foamed laminate is a resin foam. Examples of resins constituting the core layer include polyolefin resins, polyurethane resins, acrylic resins, and elastic resins. One type of resin can be used alone, or two or more types can be used in combination. Among the above, polyolefin resins are preferred for the core layer. Using polyolefin resins in the core layer results in good flexibility, mechanical strength, and also facilitates good adaptability to height differences and impact absorption.

[0049] (Polyolefin resins)

[0050] Examples of polyolefin resins include polyethylene resin, polypropylene resin, and ethylene-vinyl acetate copolymer, with polyethylene resin being preferred. By using polyethylene resin, the foamed laminate is easily imparted with flexibility. Examples of polyethylene resins include those obtained by polymerization using Ziegler-Natta compounds, metallocene compounds, chromium oxide compounds, etc., with polyethylene resin obtained by polymerization using metallocene compound catalysts being preferred.

[0051] In addition, low-density polyethylene (DPE) (density: less than 0.930 g / cm³) can be cited as an example of the polyethylene resin used in the core layer. 3 Medium-density polyethylene (density: 0.930 g / cm³) 3 Above and below 0.942 g / cm³ 3 High-density polyethylene (density: 0.942 g / cm³) 3 The above-mentioned materials include linear low-density polyethylene (LLDPE), among which linear LLDPE is preferred, and linear LLDPE obtained by polymerization using a metallocene compound polymerization catalyst is more preferred. By using linear LLDPE, the foamed laminate is endowed with high flexibility, and the thinning of the foamed laminate becomes easier.

[0052] Linear low-density polyethylene is preferably obtained by copolymerizing ethylene (for example, at least 75% by mass, preferably at least 90% by mass, relative to the total monomer content) with a small amount of α-olefin as needed. Here, specific examples of α-olefins include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene, among which α-olefins with 4 to 10 carbon atoms are preferred.

[0053] The density of linear low-density polyethylene is preferably 0.870~0.910 g / cm³. 3 More preferably, it is 0.875~0.907 g / cm³. 3 More preferably, it is 0.880~0.905 g / cm³. 3 As a polyethylene resin, various polyethylene resins can be used, and polyethylene resins outside the density range mentioned above can also be added.

[0054] (metallocene compounds)

[0055] Examples of metallocene compounds include bis(cyclopentadienyl) metal coordination compounds, which have a structure in which a transition metal is sandwiched between a π-electron unsaturated compound. More specifically, examples include compounds in which one or more cyclopentadienyl rings or their analogues act as ligands (ligands) in tetravalent transition metals such as titanium, zirconium, nickel, palladium, hafnium, and platinum.

[0056] Such metallocene compounds exhibit uniform properties at their active sites, with each site possessing the same level of activity. Polymers synthesized using metallocene compounds exhibit high uniformity in molecular weight, molecular weight distribution, composition, and compositional distribution. Therefore, when crosslinking sheets containing polymers synthesized using metallocene compounds is performed, crosslinking occurs uniformly. The uniformly crosslinked sheets exhibit uniform foaming, thus facilitating property stability. Furthermore, the ability to stretch uniformly allows for uniform thickness of the foamed laminate.

[0057] Examples of ligands include cyclopentadienyl rings and indenyl rings. These cyclic compounds can be substituted with hydrocarbon groups, substituted hydrocarbon groups, or hydrocarbon-substituted metalloid groups. Examples of hydrocarbon groups include methyl, ethyl, various propyl, various butyl, various pentyl, various hexyl, 2-ethylhexyl, various heptyl, various octyl, various nonyl, various decyl, various cetyl, phenyl, etc. It should be noted that "various" refers to all isomers, including n-, secondary, tert-, and isomers.

[0058] Alternatively, substances obtained by polymerizing cyclic compounds into oligomers can also be used as ligands.

[0059] Furthermore, in addition to unsaturated compounds with π electron systems, monovalent anionic ligands or divalent anionic chelate ligands such as chlorine and bromine, hydrocarbons, alkoxides, arylamides, aryl oxides, amides, arylamides, phosphido, arylphosphine, etc., can also be used.

[0060] Examples of metallocene compounds containing tetravalent transition metals and ligands include cyclopentadienyltitanium tri(dimethylamide), methylcyclopentadienyltitanium tri(dimethylamide), bis(cyclopentadienyl)titanium dichloride, and dimethylsilyltetramethylcyclopentadienyl-tert-butylaminozirconium dichloride.

[0061] Metallocene compounds act as catalysts in the polymerization of various olefins by combining with specific co-catalysts (pro-catalysts). Examples of specific co-catalysts include methylaluminoxane (MAO) and boron compounds. It should be noted that the ratio of the co-catalyst to the metallocene compound is preferably 10 to 1,000,000 molar ratios, more preferably 50 to 5,000 molar ratios.

[0062] In the core layer, when linear low-density polyethylene (LLDPE) is used as the polyolefin resin, LLDPE can be used alone or in combination with other polyolefin resins besides LLDPE. For example, it can be used in combination with polyethylene resins other than LLDPE, or with polyolefin resins other than polyethylene resins. The content of LLDPE in the core layer, based on the total amount of polyolefin resin, is preferably 60-100% by mass, more preferably 70-100% by mass, and even more preferably 80-100% by mass.

[0063] Examples of ethylene-vinyl acetate copolymers used as polyolefin resins include ethylene-vinyl acetate copolymers containing 50% by mass or more of ethylene.

[0064] In addition, examples of polypropylene resins include homopolymer polypropylene and propylene-α-olefin copolymers containing, for example, 75% or more by mass of propylene, more preferably 90% or more by mass of propylene. One of these resins may be used alone, or two or more may be used in combination.

[0065] Examples of α-olefins constituting propylene-α-olefin copolymers include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene, among which α-olefins with 6 to 12 carbon atoms are preferred.

[0066] Furthermore, when using a polyolefin resin in the core layer, the resin contained in the core layer can be a polyolefin resin alone, or it can contain a resin other than a polyolefin resin. As for the resin other than a polyolefin resin used in conjunction with the polyolefin resin, any resin other than a polyolefin resin can be used, but it is preferable to use an elastic system resin.

[0067] The content of polyolefin resin in the core layer, based on the total amount of the core layer, is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Furthermore, the content of polyolefin resin in the core layer only needs to be 100% by mass or less, but in order to allow for the mixing of a certain amount or more of other additives, it is preferably 99.9% by mass or less, and may also be 99.5% by mass or less.

[0068] <Foaming Agent>

[0069] The foam constituting the core layer is preferably a foam formed by foaming a foaming composition containing the above-mentioned resin and foaming agent. The foam obtained by foaming is composed of a foam with a resin as the matrix resin, either alone or mixed with additives as needed, and having a large number of cells formed by air bubbles inside.

[0070] As a foaming agent, thermally decomposable foaming agents can be cited. Both organic and inorganic foaming agents can be used as thermally decomposable foaming agents. Thermally decomposable foaming agents typically use substances with a decomposition temperature higher than the melting temperature of the resin; for example, substances with a decomposition temperature of 140~270℃ are sufficient.

[0071] Specific examples of organic foaming agents include azodicarbonamide, metal salts of azodicarboxylic acid (such as barium azodicarboxylic acid), azobisisobutyronitrile and other azo compounds, nitroso compounds such as N,N'-dinitrospentamethylenetetramine, hydrazine dicarboxamide, hydrazine derivatives such as 4,4'-oxobis(benzenesulfonylhydrazine) and toluenesulfonylhydrazine, and aminourea compounds such as toluenesulfonylaminourea.

[0072] Examples of inorganic foaming agents include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and anhydrous sodium citrate.

[0073] Among these, azo compounds are preferred from the perspectives of obtaining fine bubbles, as well as from the perspectives of economy and safety, and azodicarbonamide is particularly preferred. These thermally decomposable foaming agents can be used alone or in combination of two or more.

[0074] The amount of the thermally decomposable foaming agent in the foaming composition is preferably 0.5 to 20 parts by weight relative to 100 parts by weight of the resin, more preferably 1 to 15 parts by weight, and even more preferably 2 to 10 parts by weight.

[0075] When using polyolefin resins, acrylic resins, or elastic resins as the resin, the aforementioned thermally decomposable blowing agent is preferred as the blowing agent. However, blowing agents other than thermally decomposable blowing agents can also be used. For example, when using polyurethane resins, water, organohalogen compounds, etc., are preferred as the blowing agent. Examples of organohalogen compounds include organochlorine compounds and organofluorine compounds, with organofluorine compounds being preferred. Examples of organofluorine compounds include hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs), which may further contain chlorine atoms.

[0076] In addition, physical blowing agents can be used as blowing agents. As physical blowing agents, high-pressure inert gases are preferred. There are no particular limitations on the inert gas, as long as it is a substance that is inert to the resin composition and can be impregnated; examples include carbon dioxide, butane gas, nitrogen, and air. These gases can be mixed. Among them, carbon dioxide and butane gas are preferred from the viewpoint of easily increasing the foaming ratio of the foam. The inert gas used for impregnation is preferably in a supercritical or subcritical state.

[0077] <Other Additives>

[0078] Depending on the requirements, additives commonly used in foams, such as antioxidants, heat stabilizers, colorants, flame retardants, antistatic agents, fillers, and decomposition temperature regulators, can be blended into the foam or foaming composition. Among these, antioxidants and decomposition temperature regulators are preferred.

[0079] Specific compounds that can be used as decomposition temperature regulators include zinc oxide, zinc stearate, and urea. The content of the decomposition temperature regulator relative to 100 parts by weight of the resin is preferably 0.01 to 5 parts by weight, more preferably 0.1 to 3 parts by weight.

[0080] Examples of antioxidants include phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol, sulfur-based antioxidants, phosphorus-based antioxidants, and amine-based antioxidants. The content of the antioxidant is, for example, 0.01 to 5 parts by weight relative to 100 parts by weight of the resin.

[0081] <Expansion Ratio>

[0082] The preferred expansion ratio of the core layer foam is 4~20cm. 3 / g, preferably 5~15cm 3 / g, further preferably 6~13cm 3 / g. If the foaming ratio is above the lower limit mentioned above, the tensile strength of the foamed laminate decreases, and the core layer is more likely to crack along the surface direction before the foamed laminate is peeled off, resulting in better reworkability. In addition, the foamed laminate becomes softer, easily imparting excellent contour following and impact absorption properties.

[0083] If the foaming ratio is below the aforementioned upper limit, a certain tensile strength is imparted to the foamed laminate, preventing tearing during peeling during rework. Furthermore, various mechanical strengths become good, and impact absorption also tends to improve. Additionally, since it is easy to keep the bubble diameter below a certain level, for example, when obtaining the adhesive tape described later, even if the adhesive layer is directly laminated to the core layer, it is easy to prevent the adhesive from penetrating into the bubbles in the core layer.

[0084] <Independent bubble rate>

[0085] The independent bubble rate of the core layer is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. Furthermore, the upper limit of the independent bubble rate is not particularly limited, and is 100%. By having an independent bubble rate above the aforementioned lower limit, excellent height difference tracking and impact absorption are easily imparted. In addition, since the fracture strength of the core layer is increased, adverse conditions such as cracking within the core layer during use can be prevented.

[0086] It should be noted that the independent bubble rate can be determined according to the method of ASTM D2856 (1998).

[0087] Specifically, it is best to measure according to the following guidelines.

[0088] First, a square test piece with a side length of 5 cm is cut from the foam. Then, the thickness of the test piece is measured to calculate the apparent volume V1, and the weight W1 of the test piece is measured.

[0089] Next, the volume V2 occupied by the air bubble is calculated using the following formula. It should be noted that the density of the matrix resin constituting the test piece is set as ρ (g / cm³). 3 ).

[0090] The volume occupied by the bubble is V2 = V1 - W1 / ρ

[0091] Next, the test piece was submerged in distilled water at 23°C to a depth of 100 mm from the water surface, and a pressure of 15 kPa was applied to the test piece for 3 minutes. Then, the pressure was released in the water, and after standing for 1 minute, the test piece was removed from the water, the water adhering to the surface of the test piece was removed, and the weight W2 of the test piece was measured. The continuous bubble rate F1 and the independent bubble rate F2 were calculated according to the following formula.

[0092] Continuous bubble rate F1(%) = 100 × (W2 - W1) / V2

[0093] Independent bubble rate F2 (%) = 100 - F1

[0094] <Degree of crosslinking>

[0095] The core layer is preferably a cross-linked foam. The degree of cross-linking of the core layer is preferably 10-70% by mass, more preferably 20-60% by mass, and even more preferably 25-55% by mass. By ensuring the degree of cross-linking of the core layer is within the above range, it is easy to achieve good mechanical strength, flexibility, and impact absorption of the foamed laminate. Furthermore, foaming in the core layer can be appropriately performed. It should be noted that the method for determining the degree of cross-linking is as follows.

[0096] Take approximately 100 mg of the test tablet from the foam and accurately weigh the tablet (A, mg). Then, immerse the test tablet in xylene at 120°C for 30 cm. 3 After being placed in the solution for 24 hours, the solution is filtered through a 200-mesh metal mesh. The insoluble components on the mesh are collected, vacuum dried, and the weight B (mg) of the insoluble components is accurately measured. The degree of crosslinking (mass %) is calculated from the obtained value using the following formula.

[0097] Degree of crosslinking (mass%) = 100 × (B / A)

[0098] The thickness of the core layer is preferably 0.05 mm or more, more preferably 0.1 mm or more, and even more preferably 0.12 mm or more. If the core layer thickness is at or above the lower limit mentioned above, sufficient clearance for cutting into the foamed laminate with tools or the like can be ensured, allowing for easy reworkability through cracking along the surface direction. Furthermore, it readily imparts appropriate flexibility to the foamed laminate. The thickness of the core layer is preferably 0.7 mm or less, more preferably 0.4 mm or less, and even more preferably 0.25 mm or less. If the core layer thickness is at or below the upper limit mentioned above, the overall thickness of the foamed laminate can be thin, making it suitable for use inside thin electronic devices and the like.

[0099] It should be noted that the core layer is sometimes formed by slicing, as described later. In this case, the surface of the core layer can be the slice facet formed by slicing. The slice facet is preferably any surface of the foamed laminate. Furthermore, when the foamed laminate is manufactured using the third manufacturing method described later, the thickness of the core layer refers to the thickness of the core layer after slicing.

[0100] [Surface resin layer]

[0101] The surface resin layer can be a foamed layer formed from a foaming material or a non-foamed layer formed from a non-foaming material. It should be noted that when the surface resin layer is a foamed layer, it is only necessary that the foaming ratio is lower than that of the foaming material constituting the core layer. In this invention, the surface resin layer is preferably a non-foaming material. By using a non-foaming material for the surface resin layer, the tensile strength of the foamed laminate is increased, preventing breakage of the foamed laminate during peeling and facilitating excellent reworkability.

[0102] In addition, the surface resin layer is preferably directly laminated to the core layer, but it can also be laminated via an adhesive layer or the like.

[0103] In this invention, each surface resin layer contains an organosilicon compound. By including an organosilicon compound in the surface resin layer, the static coefficient of friction of the foam laminate surface can be reduced, resulting in good sliding properties. Furthermore, good sealing properties are also achieved, thus exhibiting excellent waterproofing, for example, when the foam laminate is used inside electronic devices. Moreover, good low adhesiveness is achieved, preventing the foam laminates from sticking together when formed into rolls for storage, transportation, etc. Therefore, surface treatment or other anti-adhesion processes for the foam laminate are unnecessary, improving the productivity of the foam laminate. Additionally, as described later, the same anti-adhesion measures can be taken when adhesive tape using the foam laminate as a substrate is formed into rolls.

[0104] In addition, due to its good low adhesiveness, it can suppress the adhesion of waste to the surface of isotropic foam laminates, especially the surface resin layer.

[0105] (organosilicon compounds)

[0106] Examples of organosilicon compounds used in the surface resin layer include siloxane-olefin copolymers and oxyalkylene silane compounds. One organosilicon compound can be used alone, or two or more can be used in combination. Siloxane-olefin copolymers are preferred as organosilicon compounds. By using siloxane-olefin copolymers, the compatibility and miscibility with polyolefin resins used in the surface resin layer become good, preventing the organosilicon compound from leaching out and facilitating the appropriate application of the mixed organosilicon compound.

[0107] <<Siloxane-Olefin Copolymer>>

[0108] Siloxane-olefin copolymers are copolymers of siloxanes (high molecular weight compounds with siloxane bonds) and olefins or polyolefins, but copolymers of siloxanes and polyolefins are preferred.

[0109] More specifically, it is a copolymer having constituent units derived from hydrosilane compounds containing one or more of the following general formula (1) as constituent units, and constituent units derived from polyolefins containing terminal vinyl groups.

[0110] The siloxane-olefin copolymer comprises a -Si-CC- structure obtained by reacting the -Si-H of the hydrosilane compound with the vinyl group of the polyolefin containing terminal vinyl groups. The polymerization method of the copolymer of the hydrosilane compound and the polyolefin containing terminal vinyl groups is not particularly limited; it can be any of random copolymers, block copolymers, and graft copolymers, but block copolymers are preferred.

[0111]

[0112] In equation (1), R 1 Y represents a hydrogen atom, a halogen atom, a hydrocarbon group, an oxygen-containing group, or a silicon-containing group. The hydrocarbon group, oxygen-containing group, and silicon-containing group may contain more than one heteroatom. 1 It represents O, S, or NR (R represents a hydrogen atom or a hydrocarbon group).

[0113] As R 1 Halogen atoms in fluorine can be exemplified by fluorine, chlorine, bromine, and iodine.

[0114] Examples of hydrocarbon groups include alkyl, alkenyl, and aryl groups. Hydrocarbon groups typically have 1 to 18 carbon atoms, with 1 to 10 carbon atoms being preferred.

[0115] Examples of alkyl groups include straight-chain or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, hexyl, 2-ethylhexyl, octyl, decyl, and octadecyl; cyclopentyl, cyclohexyl, and norbornyl; and arylalkyl groups such as benzyl, phenylethyl, and phenylpropyl.

[0116] Examples of alkenyl groups include vinyl, propenyl, and cyclohexenyl. Examples of aryl groups include phenyl, tolyl, dimethylphenyl, trimethylphenyl, ethylphenyl, propylphenyl, biphenyl, naphthyl, methylnaphthyl, anthraceneyl, and phenanthryl.

[0117] An oxygen-containing group is an organic group containing oxygen, for example, with approximately 1 to 18 carbon atoms, preferably 1 to 10. The oxygen-containing group typically has one oxygen atom, but can also have two or more. Examples of oxygen-containing groups include alkoxy and aryloxy groups. Examples of alkoxy groups include methoxy, ethoxy, propoxy, butoxy, hexoxy, octoxy, benzyloxy, and 2-phenylethoxy. Examples of aryloxy groups include phenoxy, tolyloxy, biphenyloxy, and naphthoxy.

[0118] As a silicon-containing group, it is an organic group containing silicon, and examples include alkylsilyl, alkenylsilyl, arylsilyl, alkylsiloxy, alkenylsiloxy, arylsiloxy, alkoxysilyl, aryloxysilyl, alkoxysiloxy, aryloxysiloxy, and polysiloxane. Polysiloxane is a group having two or more repeating siloxane units, and can be straight-chain or branched. Preferably, the polysiloxane has 1 to 50 silicon atoms.

[0119] Furthermore, the aforementioned hydrocarbon groups, oxygen-containing groups, and silicon-containing groups may contain more than one heteroatom. Specifically, these groups are groups in which at least one hydrogen atom is replaced by a group containing a halogen atom, oxygen, nitrogen, silicon, phosphorus, or sulfur.

[0120] As R in equation (1) 1 Of the atoms or groups listed above, preferably one or more atoms or groups selected from hydrogen atoms, halogen atoms, polysiloxane groups with 1 to 50 silicon atoms, alkoxy groups with 1 to 4 carbon atoms, and phenyl groups, and the R in the hydrosilane compound... 1 At least one of them is a polysiloxane group with 1 to 50 silicon atoms.

[0121] As a hydrosilane compound containing one or more general formulas (1) as constituent units, it is suitable to use substances with multiple Si-H bonds as shown in the following general formulas (2) and (3).

[0122]

[0123] In the above general formulas (2) and (3), R 1 For the structural unit R shown in general formula (1) 1 The same group. R 11 The atom or group is selected from one or more atoms or groups selected from hydrogen atoms, halogen atoms, silicon-containing groups with 1 to 10 silicon atoms, alkoxy groups with 1 to 4 carbon atoms, phenyl groups, and alkyl groups, preferably silicon-containing groups with 1 to 10 silicon atoms, alkoxy groups with 1 to 4 carbon atoms, phenyl groups, or alkyl groups with 1 to 4 carbon atoms. m is a number from 1 to 500, and n is a number from 1 to 50. Halogen atoms, silicon-containing groups, alkoxy groups, and alkyl groups are used with respect to R in formula (1). 1 The atoms or groups shown are examples.

[0124] Furthermore, as a hydrosilane compound comprising one or more general formulas (1) as constituent units, compounds represented by the following general formula (4) are particularly preferred.

[0125]

[0126] In equation (4), R 1and R 3 This represents hydrogen atoms, halogen atoms, hydrocarbon groups, oxygen-containing groups, or silicon-containing groups, which can be the same or different from each other. Additionally, in R... 1 and R 3 When multiple instances exist, they can be the same or different, R 2 and R 4 Y represents a hydrogen atom, a halogen atom, a hydrocarbon group, an oxygen-containing group, or a group represented by general formula (5), which may be the same as or different from each other. 1 and Y 2 The symbols O, S, or NR (R represents a hydrogen atom or a hydrocarbon group) can be the same or different from each other. Additionally, in Y... 1 and Y 2 When multiple bases exist, they can be the same or different. m is an integer from 1 to 20, and n is an integer from 0 to 20. When n is 1 or higher, Z represents the dual-valent linkage basis shown in general formula (6). When n is 0, Z represents Y. 1 With R 4 Direct bonding.

[0127]

[0128] In equation (5), R 21 Representing a hydrogen atom, halogen atom, or hydrocarbon group, with multiple Rs present. 21 They can be the same or different, and x is an integer from 0 to 10.

[0129]

[0130] In equation (6), R 11 Representing a hydrogen atom, halogen atom, or hydrocarbon group, with multiple Rs present. 11 They can be the same or different, and l is an integer from 0 to 500.

[0131] In the above general formulas (4), (5), and (6), halogen atoms, hydrocarbon groups, oxygen-containing groups, or silicon-containing groups can be represented by R in formula (1). 1 Examples of atoms or groups.

[0132] As described above, the polyolefin used in the siloxane-olefin copolymer contains one or more terminal vinyl groups. Among the polyolefins, the structures other than vinyl groups are preferably ethylene homopolymer chains, propylene homopolymer chains, or copolymer chains of two or more olefins selected from ethylene, propylene, butene, vinyl norbornene, cyclic polyenes having two or more double bonds, and chain polyenes having two or more double bonds. These preferably include polymer chains derived from ethylene; specifically, ethylene homopolymer chains, ethylene-propylene copolymer chains, and ethylene-norbornene copolymer chains are preferred.

[0133] Siloxane-olefin copolymers can be synthesized by known methods. The proportion of structural units derived from formula (1) in the siloxane-olefin copolymer is not particularly limited as long as it can represent the target function of the siloxane-olefin copolymer, and is usually 5 to 99% by mass, preferably 10 to 95% by mass.

[0134] Siloxane-olefin copolymers can be commercially available copolymers or manufactured substances. Examples of commercially available products include "Ixfora" (a registered trademark) (manufactured by Mitsui Chemicals Fin Co., Ltd., a trade name).

[0135] In addition, siloxane-olefin copolymers can use dimethyl ether with a vinyl content of 0-1 mol%. Partially crosslinked products of vinyl polysiloxanes with EPDM (ethylene-propylene rubber), SBS (styrene-butadiene-styrene block copolymer), or SIS (styrene-isoprene block copolymer) containing 0-5% by mass of unsaturated groups; amino-modified or carboxyl-modified organosilicon polymers or oligomers (polypropylene, polyethylene, ethylene) modified with maleic anhydride. Reactants of propylene copolymers, etc.

[0136] Siloxane-olefin copolymers can be masterbatches made by mixing with resins other than silicone compounds. There are no particular limitations on the form of masterbatch; granules or similar materials are acceptable. For example, polyolefin resins can be used as the resin other than silicone compounds in the masterbatch, as detailed below.

[0137] (Oxyalkylsilyl compounds)

[0138] Examples of oxyalkylene silane compounds include compounds having a polyoxyalkylene structure and a silicon-containing group. Examples of polyoxyalkylene compounds include polyoxyethylene, polyoxypropylene, polyoxybutylene, polyoxytetramethylene, polyoxyethylene-polyoxypropylene copolymers, and polyoxypropylene-polyoxybutylene copolymers. Among these, polyoxyethylene is preferred.

[0139] As a silicon-containing group, alkoxysilyl is preferred. Alternatively, it can be a group formed by the reaction of alkoxysilyl with a hydroxyl group. It should be noted that alkoxysilyl is preferably a group represented by the following general formula (7).

[0140] -Si(R 21 ) 3-a (OR 22 ) a (7)

[0141] In general formula (7), R 21 Each is an alkyl group having 1 to 4 carbon atoms, R22 Each is an alkyl group with 1 to 4 carbon atoms, and a is an integer from 1 to 3. R 21 Preferably methyl or ethyl, more preferably methyl. R 22 Preferably methyl or ethyl, more preferably methyl. a is 1 to 3, preferably 3.

[0142] The oxyalkylene silyl compound preferably has a polyoxyalkylene structure in its main chain and at least one of its terminal and side chains having an alkoxysilyl group, more preferably having an alkoxysilyl group at the terminal.

[0143] Oxyalkylsilyl compounds can be obtained by silylation reactions using polyoxyalkylene compounds and alkoxysilyl compounds as starting materials.

[0144] Examples of the aforementioned polyoxyalkylene compounds include polyethylene glycol, polyethylene glycol monoceryl ether, polyethylene glycol monododecyl ether, polyethylene glycol monooleyl ether, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol monooctylphenyl ether, polyethylene glycol monononylphenyl ether, and polypropylene glycol.

[0145] In addition, examples of alkoxysilyl compounds include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetra-n-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, methylphenyldimethoxysilane, diphenyldimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, triphenylmethoxysilane, methyl-2-(3-cyclohexene)dimethoxysilane, methylcyclohexylethoxysilane, n-propyltrimethoxysilane, trimethoxysilylbenzene oxide, trimethoxysilylnonylbenzene oxide, trimethoxysilyl(1-methyl-1-phenylethyl)benzene oxide, and 1,6-bis(trimethoxysilyl)hexane.

[0146] The content of the organosilicon compound in each surface resin layer, based on the total amount of each surface resin layer, is preferably 1 to 40% by mass. By having a content of 1% by mass or more, the effect of the mixed organosilicon compound is easily achieved. In addition, by having a content of 40% by mass or less, a decrease in various physical properties such as tensile elongation is prevented. Therefore, for example, breakage can be prevented during the manufacturing process. The content of the organosilicon compound is more preferably 2 to 25% by mass, and even more preferably 4 to 15% by mass.

[0147] [Resins other than organosilicon compounds]

[0148] The surface resin layer comprises a resin other than a silicone compound. Examples of resins other than silicone compounds include polyolefin resins, polyurethane resins, acrylic resins, and elastic resins, among which polyolefin resins are preferred. By using a polyolefin resin, the silicone compound can be appropriately mixed or compatible in the surface resin layer.

[0149] In addition to the polyolefin resins described in the core layer, acid-modified polyolefin resins can also be used as the surface resin layer. Detailed descriptions of polyolefin resins other than acid-modified polyolefin resins are the same as those in the core layer description, and are omitted here.

[0150] Examples of acid-modified polyolefin resins include those modified with at least one acid selected from unsaturated carboxylic acids and their anhydrides. Specifically, unsaturated carboxylic acids are chemically incorporated into the polyolefin resin through addition reactions, grafting reactions, or similar processes. Examples of unsaturated carboxylic acids used to modify the polyolefin resin in acid-modified polyolefin resins include, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, or their anhydrides.

[0151] Examples of polyolefin resins used in acid-modified polyolefin resins include homopolymers or copolymers of α-olefins with approximately 2 to 12 carbon atoms, such as ethylene, propylene, butene, and methylpentene-1. Among these, polyethylene resins and polypropylene resins are preferred, with polyethylene resins being the most preferred. Therefore, acid-modified polyethylene resins are preferred over olefin resins. Furthermore, acid-modified polyolefin resins may contain constituent units derived from components other than olefins and unsaturated carboxylic acids and their anhydrides, and may also contain constituent units derived from vinyl acetate and various (meth)acrylates.

[0152] Acid-modified polyolefin resins can be made primarily of olefin-derived constituent units, for example, preferably containing 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more of olefins relative to the total monomer content. Examples of acid-modified polyolefin resins include substances obtained by graft copolymerization of at least one unsaturated carboxylic acid and its anhydride with a polyolefin resin such as a polyethylene resin. Other examples include copolymers of olefins such as ethylene with unsaturated carboxylic acids such as maleic anhydride or their anhydrides, and with other components used as needed.

[0153] Specific examples of preferred acid-modified polyolefin resins include maleic anhydride-modified polyethylene resins and maleic acid-modified polyethylene resins.

[0154] Acid-modified polyolefin resins are best used when oxyalkylene silane compounds are used as organosilicon compounds. Oxyalkylene silane compounds have poor compatibility with olefin resins, but by using acid-modified polyolefin resins, their compatibility with polyolefin resins becomes good, and they can be properly mixed or dispersed in the surface resin layer.

[0155] When using acid-modified polyolefin resins, it is preferable to use a combination of acid-modified polyolefin resins and other polyolefin resins in the surface resin layer. When using them together, the proportion of acid-modified polyolefin resin in the polyolefin resin is, for example, about 1 to 50% by mass, preferably 3 to 40% by mass, and more preferably 5 to 30% by mass.

[0156] On the other hand, when using siloxane-olefin copolymers as organosilicon compounds, substances other than acid-modified polyolefin resins can be used as polyolefin resins.

[0157] As the polyolefin resin used in the surface resin layer, polyethylene resin is preferred, and linear low-density polyethylene is more preferred. Therefore, when using an oxyalkylene silane compound as the organosilicon compound, it is preferable to use polyethylene resin in combination with an acid-modified polyolefin resin as the polyolefin resin. On the other hand, when using a siloxane-olefin copolymer as the organosilicon compound, it is preferable to use polyethylene resin alone as the polyolefin resin.

[0158] When a polyolefin resin is used in the surface resin layer, the content of the polyolefin resin in each surface resin layer is preferably 50 to 98% by mass, based on each surface resin layer. By ensuring the content is 50% by mass or more, it is easy to meet the mechanical properties required for a foamed laminate, such as softness, mechanical strength, and elongation. Furthermore, by ensuring the content is 98% by mass or less, it is easy to include a certain amount of other components such as organosilicon compounds and additives in the surface resin layer.

[0159] The content of polyolefin resin in each surface resin layer is more preferably 60-97% by mass, and even more preferably 70-95% by mass.

[0160] In each surface resin layer, when linear low-density polyethylene (LLDPE) is used as the polyolefin resin, LLDPE can be used alone, or it can be used in combination with other polyolefin resins besides LLDPE. For example, it can be used in combination with polyethylene resins other than LLDPE, or with polyolefin resins other than polyethylene resins. The content of linear low-density polyethylene in each surface resin layer, based on the total amount of polyolefin resin, is preferably 60-100% by mass, more preferably 70-100% by mass, and even more preferably 80-100% by mass.

[0161] The resin used in the core layer and the resin used in the surface resin layer can be different types of resin, but are preferably the same type of resin. By using the same resin, the adhesive strength between the core layer and the surface resin layer can be easily improved, and interfacial delamination can be prevented. Therefore, both the core layer and the surface resin layer are preferably made of polyolefin resin, more preferably of polyethylene resin, and even more preferably of linear low-density polyethylene.

[0162] It should be noted that additives can be appropriately mixed into the resin of the surface resin layer. The same substances used as those used in the core layer can be used as additives.

[0163] As described above, the surface resin layer can be either a foam or a non-foamed material. When the surface resin layer is a foam, it is preferably a foam formed by foaming a foaming composition comprising a silicone compound, a resin other than a silicone compound, and a foaming agent. The specific foaming agent used is, for example, as described in the core layer section, preferably a thermally decomposable foaming agent. Furthermore, the amount of the thermally decomposable foaming agent in the resin composition is not particularly limited as long as the foaming ratio falls within the range described later; it is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, and even more preferably 0.8 to 5 parts by weight, relative to 100 parts by weight of the total mass of the silicone compound and the resin other than the silicone compound.

[0164] When the surface resin layer is a foam, the foam constituting each surface resin layer only needs to have a lower expansion ratio than the foam constituting the core layer. Preferably, the expansion ratio of the foam constituting each surface resin layer is greater than 1 cm. 3 / g and less than 5cm 3 / g, more preferably 1.1~4cm 3 / g, further preferably 1.1~2cm 3 / g. By making the foaming ratio of the surface resin layer low, it is easy to achieve good mechanical strength such as tensile strength of the foamed laminate, and also easy to achieve good reworkability.

[0165] When the surface resin layer is a foam, the independent bubble rate of each surface resin layer is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. Furthermore, there is no particular upper limit to the independent bubble rate; it is 100%.

[0166] The surface resin layer is preferably a cross-linked material, and the degree of cross-linking of each surface resin layer is not particularly limited, but is preferably 10-70% by mass, more preferably 20-60% by mass, and even more preferably 25-55% by mass. By keeping the degree of cross-linking of the surface resin layer within the above range, it is easy to achieve good mechanical strength, softness, and impact absorption of the foamed laminate.

[0167] <Thickness of surface resin layer>

[0168] The thickness of each surface resin layer in the foam laminate is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more. If the thickness of the surface resin layer is at or above the aforementioned lower limit, the foam laminate is endowed with tensile strength through the surface resin layer. When the foam laminate is made into an adhesive tape, it can prevent the foam laminate from tearing when peeled from the adhered object, thus facilitating good reworkability.

[0169] Furthermore, the thickness of the surface resin layer is preferably 200 μm or less, more preferably 80 μm or less. If the thickness of the surface resin layer is below the above-mentioned upper limit, the overall thickness of the foamed laminate can be thin, making it easily suitable for use in thin electronic devices. In addition, when winding into a roll, from the viewpoint of reducing the difference between the inner and outer circumferences and suppressing the occurrence of transverse wrinkles, it is preferable to further reduce the thickness of the surface resin layer, more preferably 30 μm or less.

[0170] It should be noted that when the foamed laminate has surface resin layers on both sides of the core layer, the thickness of the surface resin layer refers to the thickness of each individual surface resin layer. For example, if the thickness of each surface resin layer is 5 μm or more, then all surface resin layers are 5 μm or more. Furthermore, when the foamed laminate has surface resin layers on both sides of the core layer, it is preferable that all surface resin layers fall within the above-mentioned range.

[0171] When the foamed laminate has a surface resin layer on both sides, the thickness of the two surface resin layers may be the same or different, but it is preferred that they are the same.

[0172] Furthermore, the ratio of the core layer thickness to the surface resin layer thickness (core layer thickness / thickness of each surface resin layer) is, for example, 2.0 or more, preferably 5.0 or more, more preferably 8.0 or more, more preferably 12.0 or more, and preferably 50 or less, more preferably 30 or less, and more preferably 20 or less. It should be noted that when the core layer has surface resin layers on both sides, it is preferable that the ratios are within the above-mentioned ranges.

[0173] The foamed laminate has a surface resin layer containing an organosilicon compound on at least one surface. As long as its static coefficient of friction is 0.64 or less, the other surface of the foamed laminate can be left un-formed, as described above, with the core layer constituting the other surface of the foamed laminate. Alternatively, the other surface of the foamed laminate can also be composed of layers other than the surface resin layer (also referred to as other layers). There are no particular limitations on these other layers; for example, resin layers, non-woven fabrics, paper such as Japanese paper, woven fabrics made of natural fibers, synthetic fibers, etc., can be used. It is preferable that the other layers are laminated on the core layer. Among these, a resin layer is preferred. When the other layers are composed of resin layers, it is preferable that the resin layer does not contain an organosilicon compound. Furthermore, when a resin layer is provided, it is preferable that the surface of the resin layer has a coefficient of friction greater than 0.64. It should be noted that the details of the resin layer without an organosilicon compound are the same as those of the surface resin layer, except that it does not contain an organosilicon compound; therefore, its detailed description is omitted.

[0174] [Surface Treatment]

[0175] The foam laminate can be surface-treated. By performing surface treatment, the surface condition of the foam laminate changes, and the static friction coefficient can be adjusted. Corona treatment is a preferred surface treatment. Corona treatment improves the adhesion of the foam laminate to adhesives, thus improving the adhesive performance when made into adhesive tapes. It is preferable to perform the surface treatment on the surface of the foam laminate where a surface resin layer is provided.

[0176] <Manufacturing Method of Foamed Laminated Structures>

[0177] The foamed laminate of the present invention is not particularly limited, and for example, it can be manufactured by any of the following manufacturing methods 1 to 3.

[0178] (Manufacturing Method 1)

[0179] The foamed laminate of the present invention is not particularly limited. For example, it can be manufactured by the following method: for an intermediate layer formed of a foaming composition, a surface layer for constituting a surface resin layer is laminated on one or both sides of the intermediate layer to obtain a laminate sheet, and then the laminate sheet is foamed to obtain the laminate sheet (hereinafter also referred to as "first manufacturing method").

[0180] The first manufacturing method more specifically includes the following steps I to II.

[0181] (I) A process for obtaining a laminate sheet having an intermediate layer made of a foaming composition for forming a core layer and a surface layer made of a resin composition for forming a surface resin layer on one or both sides of the intermediate layer.

[0182] (II) A process of obtaining a foamed laminate by foaming at least the middle layer of the laminate sheet.

[0183] The following describes each process.

[0184] (Process (I))

[0185] There are no particular limitations on the method for obtaining the laminated sheet in process (I), but co-extrusion molding is preferred.

[0186] Specifically, when surface resin layers are formed on both sides of the intermediate layer, silicone compounds, resins other than silicone compounds, and other additives to be blended as needed are supplied to the first and third extruders respectively for melt blending to obtain a resin composition for forming the surface resin layers. Additionally, a resin for forming the core layer, a foaming agent such as a thermally decomposable foaming agent, and additives to be blended as needed are supplied to the second extruder for melt blending to obtain a foamable composition for forming the core layer.

[0187] Next, the compositions supplied by the first to third extruders are combined with the composition supplied by the second extruder as an intermediate layer, and extruded into a sheet using a T-die or the like, thereby obtaining a three-layer laminated sheet. However, in the method for obtaining a three-layer laminated sheet, if the compositions of the two surface resin layers are the same, it is possible to use only one extruder instead of two extruders (the first and third extruders), and supply the resin composition of the two surface resin layers from this one extruder.

[0188] In the case where a surface resin layer is formed on one side of the core layer, the components for forming the surface resin layer are supplied to a first extruder and melt-blended to obtain a resin composition for forming the surface resin layer. The components for forming the core layer are then supplied to a second extruder and melt-blended to obtain a foamed composition for forming the core layer. Next, the resin composition supplied from the first extruder and the foamed composition supplied from the second extruder are combined and extruded in a sheet shape using a T-die or similar device to obtain a multilayer laminate with a two-layer structure.

[0189] In co-extrusion molding, either the feed block method or the manifold method can be used, but the feed block method is preferred.

[0190] In the above method, after step (I), it is preferable to further crosslink the laminated sheet. As a crosslinking method, there is also a method of pre-mixing an organic peroxide and then heating the laminated sheet obtained in step (I) to achieve crosslinking, but it is preferable to irradiate the laminated sheet with ionizing radiation to achieve crosslinking. It should be noted that examples of ionizing radiation include electron beams and beta rays, but electron beams are preferred.

[0191] The irradiation dose of ionizing radiation is preferably 1 to 10 Mrad, more preferably 1.5 to 5 Mrad. Crosslinking is preferably performed before step (II).

[0192] (Process (II))

[0193] In step (II), the laminated sheet obtained in step (I) is foamed, at least the middle layer is foamed. The middle layer can be foamed using a foaming agent. If the foaming agent is a thermally decomposable foaming agent, it is foamed by heating the laminated sheet. The heating temperature only needs to be above the decomposition temperature of the thermally decomposable foaming agent, for example, around 150~320℃.

[0194] There are no particular limitations on the method of heating the laminated sheet. Examples include heating the laminated sheet with hot air, heating with infrared rays, heating with a salt bath, heating with an oil bath, etc., and these methods can be used in combination.

[0195] In addition, the laminated sheets can be foamed while being stretched appropriately, or foamed and then stretched appropriately.

[0196] It should be noted that the above explanation is based on the case where the surface resin layer is a non-foaming material. When the surface resin layer is a foaming material, a thermally decomposable foaming agent or other foaming agent can be pre-mixed into the resin composition used to form the surface resin layer as an additive, and the surface layer and the intermediate layer can be foamed together in step (II).

[0197] (Second Manufacturing Method)

[0198] The method for manufacturing the foamed laminate of the present invention can also be used to manufacture it by other methods. Specifically, a method can be described as follows: a foamed body constituting the core layer is pre-manufactured, and a resin film or foamed body constituting a surface resin layer is overlapped on one or both sides of the foamed body to bond it together (hereinafter also referred to as "the second manufacturing method").

[0199] In the second manufacturing method, as a method for obtaining a foamed body, a resin for forming the core layer, a thermally decomposable foaming agent, and additives to be mixed as needed are melt-blended to obtain a foamed composition for forming the core layer. It is preferable to form the foamed composition into a sheet (foamed composition sheet). The method of melt-blending the foamed composition and forming it into a sheet is not particularly limited, but it is preferred to use an extruder.

[0200] The resulting foamed composition sheet is preferably further cross-linked before the foaming process described later. As a cross-linking method, there is also a method of pre-mixing an organic peroxide and then heating the foamed composition sheet to cross-link it; however, it is preferable to irradiate the foamed composition sheet with ionizing radiation to achieve cross-linking. It should be noted that the type and amount of ionizing radiation are as described in the first manufacturing method above.

[0201] Next, the foaming composition sheet is preferably foamed. The foaming composition sheet can be treated by foaming with a foaming agent. If the foaming agent is a thermally decomposable foaming agent, foaming is performed by heating the foaming composition sheet. The heating temperature and heating method are as described in the first manufacturing method above. Furthermore, the foaming composition sheet may be appropriately stretched while foaming, or appropriately stretched after foaming.

[0202] Then, a surface layer, made of a non-foamed material (resin film) or a foamed material, which is separately prepared to form the surface resin layer, is overlapped onto one or both sides of the foam forming the core layer and bonded together to obtain a foamed laminate. Specifically, it can also be heat-pressed by heating and pressurizing using a press or the like. Alternatively, adhesives or bonding agents can be applied to the bonding surfaces between the foam forming the core layer and the surface layer, or double-sided adhesive tape can be attached, and the layers can be bonded together using adhesives, bonding agents, double-sided adhesive tape, etc. The foam forming the surface resin layer can be manufactured using the same method as the foam forming the core layer, or it can be manufactured using a different method.

[0203] (Third Manufacturing Method)

[0204] The method for manufacturing the foamed laminate of the present invention can also be used in other ways. Specifically, one example is a method (hereinafter also referred to as "the third manufacturing method") in which the core layer of the foamed laminate obtained by the first and second manufacturing methods described above (hereinafter referred to as "the laminate intermediate") is sliced ​​along the surface direction to obtain a foamed laminate with a surface layer provided on one side of the core layer. The slicing method of the core layer is not particularly limited, and it is preferable to use a known slicing machine or the like. In this manufacturing method, the laminate intermediate before slicing is preferably manufactured by the first manufacturing method described above. In addition, the laminate intermediate before slicing preferably has a surface resin layer provided on both sides of the core layer. By slicing such a laminate intermediate, two foamed laminates with a surface layer provided on one side of the core layer can be obtained.

[0205] It should be noted that when obtaining the laminated intermediate, the thickness of the core layer can be adjusted appropriately so that the thickness of the core layer after slicing is the desired thickness.

[0206] It should be noted that the third manufacturing method described above describes obtaining a laminated intermediate formed by a resin layer on the surface of the core layer laminate, and obtaining a foamed laminate by slicing the core layer constituting the laminate. However, it is also possible to manufacture a foam without a surface resin layer, slice the obtained foam, and laminate the surface resin layer of the sliced ​​foam to obtain a foamed laminate. In this case, the manufacturing method of the foam and the lamination method of the surface resin layer onto the foam are as described in the second manufacturing method.

[0207] [Adhesive tape]

[0208] The present invention also provides an adhesive tape using the aforementioned foamed laminate as a substrate. The adhesive tape includes, for example, an adhesive material disposed on at least one side of the foamed laminate. The adhesive tape can be bonded to other components via the adhesive material. The adhesive tape may have adhesive material disposed on both sides of the foamed laminate, or on only one side.

[0209] In addition, the adhesive material can be applied to the surface resin layer constituting the foamed laminate, or it can be applied to the surface where no surface resin layer is applied.

[0210] As a specific example of setting the adhesive material on the surface resin layer, when using a multilayer laminate with a surface resin layer on only one side of the foam laminate as the substrate, it is preferable to set the adhesive material only on the side with the surface resin layer. With this configuration, the foam laminate is less likely to break during the peeling of the adhesive tape, and it is easy to peel off from the adhered object without adhesive residue, thus improving reworkability. Alternatively, when the foam laminate has surface resin layers on both sides, the adhesive material can be set on only one side of the foam laminate or on both sides, but it is preferable to set it on only one side.

[0211] As a specific example of setting the adhesive on a surface without a surface resin layer, it is preferable to use a multilayer laminate with a surface resin layer on only one side of the foam laminate as the substrate, and to set the adhesive on the side opposite to the side with the surface resin layer.

[0212] The adhesive tape with the above-described structure has one surface resin layer and the other surface adhesive material. Therefore, when the adhesive tape is formed into a roll, for example, the surface resin layer and the adhesive material are in contact, but because the surface resin layer has a low coefficient of friction and low adhesiveness, adhesion is unlikely. Therefore, even without a release film on the surface of the adhesive material, unwinding of the tape is possible even when it is formed into a roll. Furthermore, by not using a release film, wrinkles are less likely to occur when the adhesive tape is formed into a roll, and unfolding is also good.

[0213] When the adhesive material is placed on a surface without a surface resin layer, the adhesive material can be directly laminated onto the core layer, or it can be laminated via the other layers mentioned above. Among these, from the viewpoint of preventing air bubbles from penetrating the core layer into the adhesive constituting the adhesive material, it is preferable to laminate the adhesive material via other layers, more preferably onto a resin layer with a static friction coefficient greater than 0.64, and even more preferably onto a resin layer made of a non-foamed layer. By laminating the adhesive material onto a resin layer with a static friction coefficient greater than 0.64, the adhesive material can be laminated onto the foamed laminate with high adhesion.

[0214] Furthermore, the adhesive material only needs to have at least one adhesive layer. This can be a single adhesive layer laminated on the surface of the foam laminate, or a double-sided adhesive sheet attached to the surface of the foam laminate, but a single adhesive layer is preferred. It should be noted that the double-sided adhesive sheet has a substrate and adhesive layers disposed on both sides of the substrate. The double-sided adhesive sheet is used to bond one adhesive layer to the foam laminate, and the other adhesive layer to other components.

[0215] There are no particular limitations on the adhesive used to form the adhesive layer; for example, acrylic adhesives, polyurethane adhesives, and rubber adhesives can be used. Additionally, release sheets such as mold release paper can be further bonded to the adhesive material.

[0216] The thickness of the adhesive material is preferably 5~200μm, more preferably 7~150μm, and even more preferably 10~100μm.

[0217] [use]

[0218] The uses of the foamed laminate of the present invention and the adhesive tape having the foamed laminate are not particularly limited, but for example, they are preferably used inside electronic devices.

[0219] Examples of electronic devices include laptop computers, mobile phones, smartphones, tablets, portable music devices, televisions, cameras, monitors, gaming devices, electronic laptops, and personal computers.

[0220] Furthermore, the electronic device is preferably a foldable electronic device whose display itself can be bent. Foldable electronic devices are preferably portable electronic devices such as mobile phones, smartphones, and tablet terminals. It should be noted that the display can be any type of liquid crystal display (LCD) or organic EL display, without particular limitation.

[0221] The foamed laminate is preferably used as an impact absorber for the display in foldable electronic devices and as a sealant when the display is housed within the electronic device. Specifically, the foamed laminate is preferably disposed on the back side of the display or on the frame used to mount the display.

[0222] When the foamed laminate of the present invention is used in a foldable type, it may sometimes slide with the display panel when the display is bent. However, as described above, due to its good sliding properties, it does not become stuck due to increased resistance, thereby preventing adverse conditions caused by sticking. For example, even if the side opposite to the side where the sliding occurs is fixed by an adhesive, adverse conditions such as adhesive peeling can be prevented.

[0223] Furthermore, since the adhesive tape of the present invention suppresses adhesive residue during rework, it facilitates the re-application of the adhesive tape and the reuse of the electronic device, for example, when it is used in an electronic device.

[0224] Furthermore, as described above, the foamed laminate of the present invention exhibits excellent height-adaptability and impact absorption, thus enabling it to adequately absorb impacts acting on the display when the adhesive tape of the present invention is used in a display. Additionally, because the adhesive tape of the present invention can adapt to the height differences of the display frame, the gap between the adhesive tape and the frame can be reduced. Moreover, the foamed laminate of the present invention also possesses excellent water resistance, making it suitable for applications requiring waterproofing.

[0225] The foamed laminate and adhesive tape of the present invention can be wound into a roll to form a roll body. When the foamed laminate of the present invention is formed into a roll body, by providing a surface resin layer with a high coefficient of friction on the surface, adhesion and other issues are less likely to occur.

[0226] Furthermore, when the adhesive tape is made into a roll, it is preferable that one surface is a surface resin layer and the other surface is an adhesive material. With such a configuration, as described above, adhesion can be adequately prevented even without a release film.

[0227] Example

[0228] The invention is further illustrated in detail by way of examples, but the invention is not limited by these examples.

[0229] [Determination Method]

[0230] The methods for determining and evaluating each physical property are described below.

[0231] <Thickness of core layer and surface resin layer>

[0232] A digital microscope (manufactured by KAIENS Co., Ltd., product name VHX-900) was used to photograph the cross-section of the foamed laminate or foam, and the thickness of the core layer and the surface resin layer was determined based on the photographed image.

[0233] Overall thickness (thickness of the foamed laminate)

[0234] The thickness of the foamed laminate is the sum of the thickness of the core layer and the thickness of the surface resin layer.

[0235] <Apparent density and foaming ratio>

[0236] Apparent density was determined according to JIS K7222. Additionally, the apparent density (g / cm³) was... 3 The reciprocal of ) is used as the foaming ratio (cm). 3 / g).

[0237] <25% compressive strength>

[0238] The determination was performed at a temperature of 23°C in accordance with the method described in JIS K 6767.

[0239] <Tensile Strength>

[0240] The foamed laminates and foams prepared in each embodiment and comparative example were cut into dumbbell-shaped No. 1 shapes as specified in JIS K6251 4.1. Using these as specimens, tensile testing was performed using a tensile testing machine (product name: Tensoron RTF235, A...). アンド (Manufactured by Dai Corporation), the test was conducted by stretching along the MD direction at a speed of 500 mm / min at a test temperature of 23°C.

[0241] <Coefficient of static friction>

[0242] According to the method specified in JIS K 7125, the foamed laminate or foam obtained in each embodiment and comparative example is placed on an SUS plate (SUS304), a sliding plate with a felt bottom is placed on it, and a 200g weight is placed on it. Then, the foamed laminate or foam is pulled in a direction parallel to the contact interface, and the static friction coefficient of the foamed laminate or foam when it starts to move is measured.

[0243] <Glossiness>

[0244] The gloss of the surface of the foamed laminate was measured based on JIS Z 8741 using a HORIBA "Gross Checker IG-331" at an incident angle of 60°.

[0245] <Sliding Evaluation>

[0246] An adhesive layer was formed by coating one side of the foamed laminate or foam obtained in each embodiment and comparative example with an adhesive. The foamed laminate or foam was then bonded to a bendable frame (25 μm polyimide film) via the adhesive layer and placed on a specially processed stainless steel plate (SUS) in a bendable state for 24 hours. At this time, the adhesive layer was visually evaluated to determine whether it had peeled off. A case where the adhesive layer did not peel off was rated as "A", and a case where it peeled off was rated as "C".

[0247] <Rework Assessment>

[0248] After applying adhesive to both sides of the foamed laminate or foam body prepared in each embodiment and comparative example, the foamed laminate or foam body was clamped with an SUS plate to bond it together, thus obtaining a test sample. A blade of a cutting tool (OLFA, trade name "folding blade cutter") was introduced along the MD direction onto the side of the foamed laminate or foam body of the test sample. By sliding the blade along the MD direction, the foamed laminate or foam body was cut (mid-slit). Next, the mid-slit foamed laminate or foam body was peeled off from the SUS plate, which served as the bonded object. After peeling, the SUS plate was observed, and a reworkability evaluation was performed based on the amount of adhesive residue (adhesive residue). The case with no adhesive residue was evaluated as "A", the case with almost no adhesive residue was evaluated as "B", and the case with a relatively large amount of adhesive residue was evaluated as "C".

[0249] Is repair of post-production wrinkles necessary?

[0250] The operability of winding the foamed laminate or foam obtained in each embodiment and comparative example into a core with a diameter of 76.2 mm for a length of 300 m with a width of 1020 mm was evaluated. Cases in which no winding wrinkles occurred and no repair was required during winding were evaluated as "A", and cases in which wrinkles needed to be repaired during winding were evaluated as "B".

[0251] The components used in each embodiment and comparative example are described below.

[0252] Polyolefin resin: Linear low-density polyethylene resin obtained using a metallocene catalyst, manufactured by Nippon Polyethylene Co., Ltd., trade name "Carnell KF283".

[0253] Organosilicon compound: "Ixfora (registered trademark) LL1513", masterbatch (organosilicon compound 30% by mass, LLDPE 70% by mass)

[0254] Foaming agent: azodicarbonamide

[0255] Decomposition temperature regulator: Zinc oxide, manufactured by Sakai Chemical Industry Co., Ltd., trade name "OW-212F"

[0256] Antioxidant: 6-di-tert-butyl-p-cresol

[0257] [Example 1]

[0258] According to the mixing proportions listed in Table 1, polyolefin resin, foaming agent, decomposition temperature regulator, and antioxidant are supplied to the second extruder and melt-blended at 130°C to produce a foamed composition for the core layer. Additionally, according to the mixing proportions listed in Table 1, polyolefin resin, silicone compound, decomposition temperature regulator, and antioxidant are supplied to the first and third extruders and melt-blended at 130°C to produce a resin composition for the surface resin layer.

[0259] A foaming composition is co-extruded from a second extruder to a thickness of 330 μm, and a resin composition is co-extruded from a first and a third extruder to a thickness of 220 μm, respectively, to obtain an unfoamed laminate sheet having an intermediate layer made of a foaming composition for a core layer and an unfoamed laminated surface layer made of a resin composition for a surface resin layer on both sides of the intermediate layer.

[0260] Next, the laminated sheet was crosslinked by irradiating it with an electron beam of 4.0 Mrad at an accelerating voltage of 550 kV. Then, the crosslinked laminated sheet was continuously fed into a foaming furnace maintained at 250°C by hot air and infrared heaters for heating, causing the middle layer to foam. A stretching process was then performed to match the target thickness, thereby obtaining the foamed laminate of Example 1, composed of a non-foamed body (surface resin layer 1), a foamed body (core layer), and a non-foamed body (surface resin layer 2). The physical properties of the obtained foamed laminate were measured and evaluated. The results are shown in Table 1.

[0261] [Example 2]

[0262] The two surfaces of the resulting foamed laminate were subjected to corona treatment, otherwise performed in the same manner as in Example 1. It should be noted that the conditions for corona treatment were an output of 0.15 kW and a conveying speed of 5.0 m / min.

[0263] [Example 3]

[0264] The content of the foaming agent in the foaming composition was changed as shown in Table 1, and the foaming composition was extruded from the second extruder with a thickness of 330 μm and the resin composition was extruded from the first and third extruders with a thickness of 220 μm, respectively, with the thickness of each layer as described in Table 1. The stretching conditions were also adjusted. Otherwise, the foamed laminate was obtained by the same method as in Example 1.

[0265] [Example 4]

[0266] The mixing of each composition was modified as shown in Table 1. Otherwise, a laminated intermediate consisting of a non-foamed body (surface resin layer), a foamed body (core layer), and a non-foamed body (surface resin layer) was obtained using the same method as in Example 1. Based on this, the core layer constituting the laminated intermediate was sliced ​​along its surface direction to obtain two foamed laminates with a surface resin layer on one side of the core layer. The physical properties of one of the two obtained foamed laminates were measured and evaluated. The core layer thickness and overall thickness listed in Table 1 are the thicknesses after slicing the core layer.

[0267] It should be noted that the core layer was sliced ​​using a cutting blade. Furthermore, the surface resin layers obtained before core layer slicing were all obtained by mixing the surface resin layer compositions described in Table 1.

[0268] [Compare Examples 1 and 2]

[0269] Raw materials were not supplied to the first and third extruders, nor to the laminated resin composition made from the foaming composition for the core layer. The thickness of the resulting foam was adjusted as described in Table 1. Otherwise, a foam formed from individual foaming layers was obtained using the same method as in Example 1. The physical properties of the obtained foam were measured and evaluated. The results are shown in Table 1.

[0270] [Comparative Example 3]

[0271] The resin composition for the surface resin layer was modified as described in Table 1, but no organosilicon compound was added to the surface resin layer. Otherwise, it was carried out in the same manner as in Example 1.

[0272] [Table 1]

[0273] *It should be noted that the static friction coefficient and gloss level are recorded based on the larger value measured for both surfaces. It should also be noted that as long as the static friction coefficient and gloss level of either surface are within the scope of the claims of this invention, they fall within the scope of this application.

[0274] As described above, the foamed laminates of Examples 1-4 have a core layer as a foam and a surface resin layer containing an organosilicon compound, and have a static coefficient of friction of 0.64 or less, thus exhibiting good sliding properties. Even when used with a flexible frame and the frame is bent, no adhesive layer peeling or other defects occur, making them suitable for foldable electronic devices. Furthermore, the foamed laminates of Examples 1-3 do not leave adhesive residue when peeled off after being attached to the substrate, resulting in good reworkability. Moreover, their low compressive strength allows for good flexibility, making them suitable for use as sealing materials, impact-absorbing materials, etc.

[0275] In contrast, the foams or foam laminates of Comparative Examples 1-3 do not contain silicone compounds in their surface resin layers and have a static friction coefficient greater than 0.64. Therefore, they have low sliding properties. If they are applied to a flexible frame and the frame is bent, the resistance increases, causing jamming and applying excessive force to the adhesive tape, resulting in tape peeling. Furthermore, in Comparative Examples 1 and 2, because they are single-layer foams, adhesive residue remains after peeling from the adhered object, hindering reworkability.

[0276] Explanation of symbols

[0277] 10 Foamed Laminated Structures

[0278] 11 core layers

[0279] 12. Surface resin layer.

Claims

1. A foamed laminate comprising a core layer as a foam and a surface resin layer disposed on at least one side of the core layer and comprising an organosilicon compound, wherein the static friction coefficient of the foamed laminate is 0.64 or less.

2. The foamed laminate according to claim 1, wherein the static friction coefficient is 0.6 or less.

3. The foamed laminate according to claim 1, wherein the thickness of the foamed laminate is 0.05~0.3mm.

4. The foamed laminate according to claim 1, wherein the content of the organosilicon compound in the surface resin layer is 1-40% by mass.

5. The foamed laminate according to claim 1, wherein the surface resin layer is a foamed material or a non-foamed material.

6. The foamed laminate according to claim 1, wherein the surface resin layer comprises a polyolefin resin.

7. The foamed laminate according to claim 1, wherein the organosilicon compound is a siloxane-olefin copolymer.

8. An adhesive tape comprising a foamed laminate according to any one of claims 1 to 7, and an adhesive material disposed on at least one surface of the foamed laminate.

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