Decorative sheet

Abstract

To provide a decorative sheet having improved cohesive strength of an adhesive layer and enhanced shrinkage resistance.SOLUTION: There is provided a decorative sheet having a substrate composed of a material containing polyvinyl chloride and an adhesive layer containing an ultraviolet-curable hot-melt adhesive. The adhesive layer preferably contains an acrylic adhesive as the ultraviolet-curable hot-melt adhesive. Further, the adhesive layer preferably contains a tackifier. Furthermore, the content of the tackifier in the adhesive layer is preferably 5 pts.mass or more and 40 pts.mass or less based on 100 pts.mass of the adhesive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a decorative sheet. [Background technology]

[0002] Decorative sheets generally have a structure in which a pressure-sensitive adhesive layer is provided on a substrate, and the substrate is attached to an adherend so as to cover the surface of the adherend, thereby decorating and protecting the adherend. For example, decorative sheets include those that are attached to the wall surfaces of rooms as interior building materials.

[0003] As the substrate of a decorative sheet, materials containing polyvinyl chloride are widely used from the viewpoints of durability, flame retardancy, processability, workability, etc. (see, for example, Patent Document 1).

[0004] Meanwhile, solvent-based adhesives have traditionally been widely used to form adhesive layers on decorative sheets, but in recent years, the use of non-solvent-based adhesives has been considered from the perspective of reducing volatile organic compound (VOC) emissions during manufacturing and reducing the amount of residual solvent in the product after manufacturing.

[0005] Hot-melt pressure-sensitive adhesives have been attracting attention in recent years as pressure-sensitive adhesives that can be produced without using solvents (see, for example, Patent Document 2).

[0006] However, conventional hot melt adhesives did not have sufficient cohesive strength, and when such hot melt adhesives were used in decorative sheets, the shrinkage resistance of the decorative sheets was insufficient, and when decorative sheets 1 were attached edge-to-edge, the adhesive layer was unable to prevent the substrate from shrinking over time, resulting in the formation of gaps (openings). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-099752 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-186487 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a decorative sheet having improved cohesive strength of the pressure-sensitive adhesive layer and improved shrink resistance. [Means for solving the problem]

[0009] These objects can be achieved by the present invention as set forth in (1) to (4) below. (1) a substrate made of a material containing polyvinyl chloride; and a pressure-sensitive adhesive layer containing an ultraviolet-curable hot-melt pressure-sensitive adhesive.

[0010] (2) The decorative sheet according to (1) above, wherein the adhesive layer contains an acrylic adhesive as the ultraviolet-curable hot-melt adhesive.

[0011] (3) The decorative sheet according to (1) or (2), wherein the pressure-sensitive adhesive layer contains a tackifier.

[0012] (4) The decorative sheet according to (3) above, wherein the content of the tackifier in the adhesive layer is 5 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the adhesive. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a decorative sheet having improved cohesive strength of the pressure-sensitive adhesive layer and improved shrinkage resistance. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic longitudinal sectional view showing a preferred embodiment of the decorative sheet of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will be described in detail below. [1] Decorative sheet First, the decorative sheet of the present invention will be described. FIG. 1 is a schematic longitudinal sectional view showing a preferred embodiment of the decorative sheet of the present invention.

[0016] The decorative sheet 1 has a substrate 10 made of a material containing polyvinyl chloride, and an adhesive layer 20 containing an ultraviolet-curable hot-melt adhesive.

[0017] The decorative sheet 1 is applied so as to cover at least a portion of the surface of the adherend, and decorates and protects the surface of the adherend. In this specification, the term "sheet" includes the concept of film.

[0018] According to the decorative sheet 1, the base material 10 is made of a material containing polyvinyl chloride, which can improve the flame retardancy, weather resistance, strength, durability, processability, workability, etc. of the base material 10.

[0019] Furthermore, the decorative sheet 1 uses an ultraviolet-curable hot-melt adhesive in the adhesive layer 20, which provides the following effects: When the decorative sheet 1 is manufactured, ultraviolet light is applied to cure the ultraviolet-curable hot-melt adhesive, improving the cohesive strength of the adhesive layer 20. This allows the adhesive layer 20 to suppress shrinkage of the substrate 10 over time, improving the shrinkage resistance of the decorative sheet 1. Furthermore, the improved cohesive strength of the adhesive layer 20 also improves the constant load resistance and holding power of the decorative sheet 1.

[0020] Furthermore, the decorative sheet 1 uses a non-solvent, ultraviolet-curable hot-melt adhesive as its adhesive, which not only reduces the amount of volatile organic compounds (VOCs) emitted during the production of the decorative sheet 1, but also reduces the amount of residual solvent in the product after production.

[0021] Furthermore, by including a tackifier in the ultraviolet-curable hot-melt adhesive, the adhesive strength of the decorative sheet 1 to the adherend can be made sufficiently high.

[0022] In this specification, the term "hot melt pressure-sensitive adhesive composition" refers to a type of pressure-sensitive adhesive composition that melts when heated and becomes spreadable and coatable, and that develops adhesiveness and cohesive strength when cooled.

[0023] [1-1] Base material The substrate 10 is a sheet-like member, and as described above, is made of a material containing polyvinyl chloride.

[0024] Polyvinyl chloride has higher flame retardancy than other resin materials, and is also excellent in weather resistance, and its strength and plasticity can be easily adjusted by adding a plasticizer, etc.

[0025] Therefore, by using polyvinyl chloride to form the substrate 10, the flame retardancy, weather resistance, strength, durability, processability, workability, and the like of the substrate 10 can be easily improved.

[0026] The substrate 10 preferably contains a plasticizer in addition to polyvinyl chloride. This makes the substrate 10 soft, highly impact resistant, and easy to handle.

[0027] Examples of the plasticizer that can be used include phthalate ester plasticizers such as dioctyl phthalate (di-2-ethylhexyl phthalate (DOP)), dibutyl phthalate, dinonyl phthalate, and diisononyl phthalate (DINP); aliphatic dibasic acid diester plasticizers such as dioctyl adipate and dioctyl sebacate; phosphate ester plasticizers such as tricresyl phosphate and trioctyl phosphate; epoxy plasticizers such as epoxidized soybean oil and epoxy resin; and polyester plasticizers.

[0028] This makes it possible to improve the impact resistance and handling properties of the substrate 10 and the decorative sheet 1, and also to improve the elongation and breaking strength of the substrate 10.

[0029] The content of the plasticizer in the substrate 10 is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 10 parts by mass or more and 45 parts by mass or less, and even more preferably 15 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of polyvinyl chloride. This makes it possible to make the above-mentioned effects more pronounced.

[0030] The substrate 10 may contain other resin materials in addition to polyvinyl chloride. Furthermore, the material that constitutes the substrate 10 may contain various additives as needed.

[0031] Examples of the additives include stabilizers and colorants. Examples of the stabilizer that can be used include metal soaps such as fatty acid calcium, fatty acid zinc, and fatty acid barium; hydrotalcite; epoxy-based stabilizers; barium-based stabilizers; calcium-based stabilizers; tin-based stabilizers; zinc-based stabilizers; and composite stabilizers such as calcium-zinc (Ca-Zn) and barium-zinc (Ba-Zn) systems. Specific examples of the metal soaps include calcium laurate, calcium stearate, calcium ricinoleate, zinc laurate, zinc ricinoleate, zinc stearate, barium laurate, barium stearate, and barium ricinoleate. As the colorant, for example, organic pigments, inorganic pigments, dyes, etc. can be used.

[0032] The substrate 10 only needs to be made of a material containing polyvinyl chloride at least in the area that comes into contact with the pressure-sensitive adhesive layer 20, and may have an area that does not contain polyvinyl chloride.

[0033] The polyvinyl chloride content in the portion of the substrate 10 that comes into contact with the adhesive layer 20 is preferably 50% by mass or more and 95% by mass or less, more preferably 55% by mass or more and 93% by mass or less, and even more preferably 60% by mass or more and 90% by mass or less.

[0034] If the polyvinyl chloride content is too low, the strength, rigidity, flame retardancy, etc. of the substrate 10 may decrease. If the polyvinyl chloride content is too high, the strength and rigidity of the substrate 10 may become too high, which may decrease processability and workability.

[0035] A printed layer constituting the decoration may be formed on the substrate 10. For example, the printed layer may be formed inside the substrate 10, or may be laminated on the surface opposite to the surface that comes into contact with the pressure-sensitive adhesive layer 20. Furthermore, a coating layer that protects the surface of the substrate 10 may be provided on the surface of the substrate 10 opposite to the surface that comes into contact with the pressure-sensitive adhesive layer 20, either on top of the printed layer or instead of the printed layer. Another layer may be laminated on the surface of the substrate 10 opposite to the surface that comes into contact with the pressure-sensitive adhesive layer 20.

[0036] The thickness of the substrate 10 is preferably 100 μm or more and 300 μm or less, more preferably 130 μm or more and 250 μm or less, and even more preferably 150 μm or more and 200 μm or less. This makes the decorative sheet 1 easier to handle.

[0037] [1-2] Adhesive layer The pressure-sensitive adhesive layer 20 is the portion that comes into contact with and bonds to the adherend when the decorative sheet 1 is attached to the adherend.

[0038] The adhesive layer 20 is formed using an ultraviolet-curable hot-melt adhesive composition that undergoes a curing reaction when irradiated with ultraviolet light.

[0039] In the following description, the ultraviolet-curable hot-melt pressure-sensitive adhesive composition may be simply referred to as the "pressure-sensitive adhesive composition."

[0040] Such an ultraviolet-curable hot-melt pressure-sensitive adhesive composition can be, for example, one containing a polymer having ultraviolet-reactive groups that contribute to a crosslinking reaction upon irradiation with ultraviolet light. Also, an ultraviolet-curable hot-melt pressure-sensitive adhesive composition can be, for example, one containing, in addition to a polymer exhibiting adhesiveness, a low-molecular-weight compound having ultraviolet-reactive groups that contribute to a crosslinking reaction upon irradiation with ultraviolet light.

[0041] By using the hot melt pressure-sensitive adhesive composition as described above, the pressure-sensitive adhesive layer 20 will have a suitable crosslinked structure and excellent cohesive strength.

[0042] The UV-reactive group is excited by UV irradiation to generate radicals that trigger a curing reaction (crosslinking reaction).

[0043] Examples of the ultraviolet-reactive group include a functional group having a benzophenone structure, a functional group having a benzyl structure, a functional group having an o-benzoylbenzoate structure, a functional group having a thioxanthone structure, a functional group having a 3-ketocoumarin structure, a functional group having a 2-ethylanthraquinone structure, and a functional group having a camphorquinone structure, with a functional group having a benzophenone structure being preferred.

[0044] This makes it possible to improve the reactivity to ultraviolet light and also improve the stability to stimuli other than ultraviolet light.

[0045] The ultraviolet-curable hot-melt pressure-sensitive adhesive composition preferably contains an acrylic polymer as the polymer that exhibits adhesive properties.

[0046] The acrylic polymer is a polymer or copolymer of acrylic monomers. Examples of acrylic monomers include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, and lauryl (meth)acrylate. In particular, the acrylic polymer preferably contains, as the acrylic monomer, an alkyl (meth)acrylate whose alkyl group has 1 to 8 carbon atoms. Among alkyl (meth)acrylates whose alkyl group has 1 to 8 carbon atoms, 2-ethylhexyl (meth)acrylate and butyl (meth)acrylate are particularly preferred.

[0047] When the polymer contained in the pressure-sensitive adhesive composition has an ultraviolet-reactive group, the ultraviolet-reactive group is usually introduced into the side chain of the polymer.

[0048] In particular, when the acrylic polymer has an ultraviolet-reactive group, the proportion of the ultraviolet-reactive group in the entire acrylic polymer is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.2% by mass or more and 3.0% by mass or less.

[0049] This makes it possible to prolong the pot life of the pressure-sensitive adhesive composition and to provide the pressure-sensitive adhesive layer 20 with superior adhesiveness.

[0050] An example of such an acrylic polymer having a UV-reactive group is commercially available from BASF under the trade name "acResin (registered trademark) UV." Examples of "acResin (registered trademark) UV" include "acResin (registered trademark) A250 UV," "acResin (registered trademark) A260 UV," "acResin (registered trademark) A204 UV," and "acResin (registered trademark) UV 3532."

[0051] The glass transition temperature of the acrylic polymer having an ultraviolet-reactive group is preferably 0°C or lower, more preferably -20°C or lower, and even more preferably -30°C or lower.

[0052] This makes it easier for adhesive properties to be exerted. Note that, unlike hot melt adhesives, ultraviolet-curable hot melt pressure-sensitive adhesives maintain their adhesive strength even without heating, and can be suitably attached to adherends.

[0053] The adhesive layer 20 preferably contains a tackifier. This increases the adhesive strength to the adherend, and the effects of the present invention described above are more pronounced.

[0054] The tackifier is not particularly limited, and examples thereof include alicyclic petroleum resins, terpene resins, rosin resins, and styrene resins. One or a combination of two or more selected from these may be used, but at least one selected from the group consisting of styrene resins, hydrogenated terpene phenol resins, and hydrogenated rosin resins is preferred.

[0055] This more effectively prevents the ultraviolet curing properties of the ultraviolet-curable hot-melt pressure-sensitive adhesive from being hindered, while more significantly demonstrating the effects of using the tackifier described above.

[0056] Petroleum resins are obtained by polymerizing, by known methods, diolefins and monoolefins in the fraction of cracked oil, a by-product of the production of ethylene by steam cracking petroleum. C5 petroleum resins are made from C5 fractions such as isoprene, 1,3-pentadiene, cyclopentene, and cyclopentadiene, while C9 petroleum resins are made from C9 fractions such as styrene, vinyltoluene, α-methylstyrene, indene, alkylindene, and dicyclopentadiene.

[0057] Examples of alicyclic petroleum resins include alicyclic hydrocarbon resins obtained by cyclodimerizing C5 petroleum resins and then polymerizing them; polymers of cyclic diene compounds (cyclopentadiene, dicyclopentadiene, ethylidene norbornene, dipentene, ethylidene bicycloheptene, vinylcycloheptene, tetrahydroindene, vinylcyclohexene, limonene, etc.) or hydrogenated products thereof; and alicyclic hydrocarbon resins obtained by hydrogenating the aromatic rings of C9 petroleum resins or C5 petroleum resins / C9 petroleum resins.

[0058] Among these, the alicyclic petroleum resin is preferably an alicyclic petroleum resin obtained by hydrogenating a C5 petroleum resin / C9 petroleum resin.

[0059] The alicyclic petroleum resin may be a commercially available product, and examples of commercially available products include the Alcon (registered trademark) series (Alcon (registered trademark) P-90, P-100, P-115, P-125, P-140, M-90, M-100, M-115, M-135 (all manufactured by Arakawa Chemical Industries, Ltd.)) and the Quintone (registered trademark) series (Quintone (registered trademark) 1105, 1325, 1340, 1500, etc. (all manufactured by Zeon Corporation). One type of alicyclic petroleum resin may be used alone, or two or more types may be used in combination.

[0060] Examples of terpene resins include terpene resins, terpene phenol resins, aromatic modified terpene resins, and hydrogenated terpene phenol resins obtained by hydrogenating these resins.

[0061] Commercially available terpene resins may be used. Examples of terpene resins include YS Resin (registered trademark) PX1250, PX1150, PX1000, PX800, PX1150N, and PX300N (all manufactured by Yasuhara Chemical Co., Ltd.). Examples of terpene phenol resins include YS Polystar (registered trademark) U130, U115, T160, T145, T130, T115, T100, T80, T30, S145, G150, G125, N125, K125, and TH130 (all manufactured by Yasuhara Chemical Co., Ltd.), and Tamanol E-100 and E-300-NT (manufactured by Arakawa Chemical Industries, Ltd.). Examples of aromatic modified terpene resins include YS Resin (registered trademark) TO125, TO115, TO105, and TO85 (all manufactured by Yasuhara Chemical Co., Ltd.). Examples of hydrogenated terpene phenol resins include YS Polystar (registered trademark) UH115 (all manufactured by Yasuhara Chemical Co., Ltd.). The terpene resins may be used alone or in combination of two or more.

[0062] Examples of rosin-based resins include natural rosin, hydrogenated rosin, and polymerized rosin, and one or more selected from these may be used in combination. Commercially available rosin-based resins may also be used.

[0063] Examples of styrene-based resins include homopolymers of α-methylstyrene, homopolymers of styrene-based monomers, copolymers of α-methylstyrene and styrene-based monomers, and copolymers of α-methylstyrene, styrene-based monomers, and other monomers.

[0064] The method for adding the tackifier is not particularly limited. The content of the tackifier in the pressure-sensitive adhesive layer 20 is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the pressure-sensitive adhesive. The content of the tackifier in the pressure-sensitive adhesive layer 20 is preferably 40 parts by mass or less, per 100 parts by mass of the pressure-sensitive adhesive.

[0065] This makes it possible to increase the adhesive strength to the adherend, and to more significantly exhibit the effects of the present invention described above.

[0066] The adhesive layer 20 may contain a flame retardant. This can improve the flame retardancy of the pressure-sensitive adhesive layer 20, and can improve the flame retardancy of the entire decorative sheet 1.

[0067] The flame retardant to be used may have a thermal decomposition temperature or flash point higher than the coating temperature of the ultraviolet-curable hot-melt pressure-sensitive adhesive composition.

[0068] The flame retardant contained in the adhesive layer 20 may be, for example, a halogen-based flame retardant.

[0069] Halogen-based flame retardants exhibit flame retardancy by trapping active radicals generated during combustion, reducing the amount of heat generated by preferentially generating carbon monoxide, and providing a masking effect due to non-flammable gases such as halogen gases, which can improve the flame retardancy of the pressure-sensitive adhesive layer 20 and the decorative sheet 1 as a whole.

[0070] In particular, when the pressure-sensitive adhesive layer 20 contains a brominated flame retardant as the flame retardant, the above-mentioned effects are more pronounced.

[0071] Examples of bromine-based flame retardants include tetrabromobisphenol A, tetrabromobisphenol A diallyl ether, tetrabromobisphenol A dimethallyl ether, tetrabromobisphenol A diglycidyl ether, tribromophenol adduct of tetrabromobisphenol A diglycidyl ether; tetrabromobisphenol A bis(2,3-dibromopropyl ether), tetrabromobisphenol A bis(2-bromoethyl ether), tetrabromobisphenol A bis(2,3-dibromo-2-methylpropyl ether), Brominated bisphenol compounds or their derivatives such as tetrabromobisphenol S bis(2,3-dibromopropyl ether), tetrabromobisphenol S; hexabromobenzene, pentabromotoluene, ethylenebispentabromodiphenyl, decabromodiphenyl ether, octabromodiphenyl ether, pentabromobenzyl bromide, bis(2,4,6-tribromophenoxy)ethane, tetrabromophthalic anhydride, octabromotrimethylphenylindane, pentabromobenzyl acrylate, tributary brominated aromatic compounds or derivatives thereof, such as bromophenyl allyl ether and 2,3-dibromopropyl pentabromophenyl ether; brominated aromatic compounds or derivatives thereof, such as mono(2,3-dibromopropyl)isocyanurate, di(2,3-dibromopropyl isocyanurate), p(2,3-dibromopropyl)isocyanurate, mono(2,3,4-tribromobutyl)isocyanurate, di(2,3,4-tribromobutyl)isocyanurate, tris(2,3,4-tribromobutyl)isocyanurate, and tris(2,3-dibromopropyl)isocyanurate; Bromine and nitrogen atom-containing compounds such as brominated isocyanurates or ethylene bistetrabromophthalimide, ethylene bisdibromonorbornanedicarboximide, and 2,4,6-tris(2,4,6-tribromophenoxy)1,3,5-triazine; brominated bisphenol derivative oligomers such as tetrabromobisphenol A polycarbonate oligomer and brominated bisphenol adduct epoxy oligomer with tetrabromobisphenol A diglycidyl ether; brominated acrylic resins such as pentabromobenzyl acrylate polymer;Examples of suitable bromine and phosphorus atom-containing compounds include tris(tribromoneopentyl)phosphate and tris(bromophenyl)phosphate; and brominated inorganic compounds such as ammonium bromide. These may be used alone or in combination of two or more.

[0072] Among these, from the viewpoint of superior flame retardancy, brominated isocyanurate is preferred, and tris(2,3-dibromopropyl)isocyanurate is more preferred. Commercially available tris(2,3-dibromopropyl)isocyanurate includes, for example, "EB-70" manufactured by Manac Corporation.

[0073] The pressure-sensitive adhesive layer 20 may also contain a phosphorus-based flame retardant as a flame retardant. Phosphorus-based flame retardants exhibit flame retardancy by producing phosphoric acid, polyphosphoric acid, etc. during combustion, which extract hydrogen and oxygen from the polymer, carbonizing the polymer and forming a highly flame-retardant carbonized film that blocks oxygen.

[0074] Examples of phosphorus-based flame retardants include phosphate ester-based flame retardants, ammonium polyphosphate-based flame retardants, melamine phosphate-based flame retardants, phosphoric acid amide-based flame retardants, and phosphazene compound-based flame retardants.

[0075] Commercially available phosphate ester flame retardants include, for example, non-halogen phosphate esters "TMP (trimethyl phosphate)," "TEP (triethyl phosphate)," "TPP (triphenyl phosphate)," "TCP (tricresyl phosphate)," "TXP (trixylenyl phosphate)," "CDP (cresyl diphenyl phosphate)," and "PX-110 (cresyl di-2,6-xylenyl phosphate)" manufactured by Daihachi Chemical Industry Co., Ltd., non-halogen condensed phosphate esters "CR-733S," "CR-741," "PX-200," "DAIGUARD-580," "DAIGUARD-850," and "DAIGUARD-880," halogen-containing phosphate esters "TMCPP (tris(chloropropyl) phosphate)" and "CR-900 (tris(tribromoneopentyl) phosphate)," halogen-containing condensed phosphate esters "CR-504L," "CR-570," and "DAIGUARD-540" manufactured by Akzo Nobel Prize winners. The Phosflex series, such as "Phosflex 4, 71B, TXP, T-BEP" manufactured by Pan Co., Ltd.; the Phylor series, such as "Phylorflex RDP, Sol-DP, Firequel 220, EHC, Phylor PCF, 6" manufactured by Pan Co., Ltd.; the Leophos series, such as "Leophos 35, 50, 65, 95, 110, BAPP" which are non-halogen phosphate esters manufactured by Ajinomoto Fine-Techno Co., Ltd.; and the Chronitex series, such as "Cronitex CDP, TCP, TXP" manufactured by Ajinomoto Fine-Techno Co., Ltd. Examples include the Leomol series, the Durad series such as "Leolube HYD-110, Durad TXP" and the like; the Adekastab series such as "ADK STAB PFR, FP-600, FP-900L" which are condensed phosphate esters manufactured by ADEKA Corporation; and the condensed phosphate ester "NcendXP-30", halogen-containing phosphate esters "Antiblaze TMCP, 195", and halogen-containing condensed phosphate ester "Antiblaze V-6", manufactured by Albemarle Japan.

[0076] Examples of the ammonium polyphosphate-based flame retardant include ammonium polyphosphate alone and composite materials containing ammonium polyphosphate as a main component.

[0077] Ammonium polyphosphate has the general formula (NH4) r+2 P r O 3r+1 (where r is an integer between 20 and 1000), and when r is large enough, the formula for metaphosphoric acid is (NH4PO3) r (where r is the same as above)

[0078] On the other hand, examples of composite materials containing ammonium polyphosphate as a main component include those in which the ammonium polyphosphate is coated or microencapsulated with a thermosetting resin, those in which the surface of the ammonium polyphosphate is coated with melamine monomer or other nitrogen-containing organic compounds, etc., those treated with surfactants or silicon compounds, and those in which melamine or the like is added during the production process of ammonium polyphosphate to make it less soluble.

[0079] Examples of commercially available ammonium polyphosphate flame retardants include "Exolit-AP422, AP423, AP462" manufactured by Clariant, "TERRAJU-S10, C30, C60, C70, C80" manufactured by Budenheim, "Firecut P-770, P-790" manufactured by Suzuhiro Chemical Co., Ltd., and "Taien K, C=II" manufactured by Taihei Chemical Industry Co., Ltd.

[0080] Examples of commercially available phosphazene compound-based flame retardants include "Lavitol FP-110, FP-100" manufactured by Fushimi Pharmaceutical Co., Ltd.

[0081] The pressure-sensitive adhesive layer 20 may contain both a bromine-based flame retardant and a phosphorus-based flame retardant as the flame retardant.

[0082] This makes it possible to increase the content of the flame retardant in the pressure-sensitive adhesive layer 20 while suppressing a decrease in the adhesiveness of the pressure-sensitive adhesive layer 20. As a result, the flame retardancy of the decorative sheet 1 can be more effectively improved.

[0083] When the adhesive layer 20 contains a bromine-based flame retardant and a phosphorus-based flame retardant, when the content of the bromine-based flame retardant in the adhesive layer 20 is X2B [mass%] and the content of the phosphorus-based flame retardant in the adhesive layer 20 is X2P [mass%], it is preferable to satisfy the relationship 0.1≦X2P / X2B≦3.0, it is more preferable to satisfy the relationship 0.3≦X2P / X2B≦2.5, and it is even more preferable to satisfy the relationship 0.5≦X2P / X2B≦2.0.

[0084] By satisfying this relationship, the effect of using a bromine-based flame retardant and a phosphorus-based flame retardant in combination is more pronounced, and the flame retardancy of the decorative sheet 1 can be further improved while suppressing a decrease in the adhesiveness of the adhesive layer 20.

[0085] The content of the flame retardant in the pressure-sensitive adhesive layer 20 is preferably 10% by mass to 45% by mass, more preferably 15% by mass to 40% by mass, and even more preferably 20% by mass to 35% by mass.

[0086] If the content of the flame retardant in the pressure-sensitive adhesive layer 20 is less than the lower limit, the amount of flame retardant contained in the pressure-sensitive adhesive layer 20 will be too small, making it difficult to improve the flame retardancy of the decorative sheet 1. On the other hand, if the content of the flame retardant in the pressure-sensitive adhesive layer 20 exceeds the upper limit, the amount of flame retardant contained in the pressure-sensitive adhesive layer 20 will be too great, which will affect the adhesive properties of the pressure-sensitive adhesive layer 20 and may reduce the adhesion of the pressure-sensitive adhesive layer 20 to the substrate 10 or the adherend.

[0087] The average particle size of the flame retardant contained in the pressure-sensitive adhesive layer 20 is preferably 50 nm or more and 1000 nm or less, more preferably 100 nm or more and 800 nm or less, and even more preferably 150 nm or more and 600 nm or less.

[0088] If the average particle size of the flame retardant is less than the lower limit, the flame retardancy of the flame retardant may be difficult to exhibit. On the other hand, if the average particle size of the flame retardant is more than the upper limit, the flame retardant may be too large, which may reduce the adhesion of the pressure-sensitive adhesive layer 20 to the substrate 10 or the adherend.

[0089] The ultraviolet-curable hot-melt pressure-sensitive adhesive composition may contain other components in addition to the components described above, if necessary.

[0090] Examples of other components include dispersants, antioxidants, polymerization initiators, ultraviolet absorbers, light stabilizers, heat stabilizers, softeners, silane coupling agents, fillers, colorants, antistatic agents, etc. These components may be used alone or in combination of two or more.

[0091] The thickness of the pressure-sensitive adhesive layer 20 is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 55 μm or less.

[0092] This allows the decorative sheet 1 to better exert its adhesive strength to the adherend, and improves the workability when attaching the decorative sheet 1 to the adherend. In addition, the pressure-sensitive adhesive layer 20 can more reliably suppress shrinkage of the substrate 10 over time, further improving the shrinkage resistance of the decorative sheet 1.

[0093] [1-3] Release liner The surface of the pressure-sensitive adhesive layer 20 of an unused decorative sheet 1 is preferably covered with a release liner 30, as shown in FIG.

[0094] This makes it possible to suitably protect the pressure-sensitive adhesive layer 20 before it is attached to the adherend, and also makes it easier to handle an unused decorative sheet 1.

[0095] The release liner 30 has releasability relative to the pressure-sensitive adhesive layer 20. The release liner 30 functions to protect the pressure-sensitive adhesive layer 20 at least during storage of the decorative sheet 1. The release liner 30 is peeled from the pressure-sensitive adhesive layer 20 so that at least the portion of the pressure-sensitive adhesive layer 20 that will come into contact with the adherend is exposed before the decorative sheet 1 is attached to the adherend. The decorative sheet 1 does not necessarily have to be provided with a release liner 30.

[0096] Examples of materials constituting the release liner 30 include paper, various plastics such as polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, and metals, and one or more selected from these may be used in combination.

[0097] A release treatment may be applied to the release liner 30. Examples of release agents used for the release treatment include silicone, olefin-based resins, isoprene-based resins, butadiene-based resins, long-chain alkyl-based resins, and alkyd-based resins.

[0098] The thickness of the release liner 30 is not particularly limited, but is preferably 10 μm or more and 150 μm or less, and more preferably 20 μm or more and 140 μm or less.

[0099] The decorative sheet 1 is preferably used by being attached to the interior walls, floors, ceilings, etc. of a building, or by being attached to gypsum board used for the interior walls, floors, ceilings, etc. of a building.

[0100] The decorative sheet 1 has improved shrinkage resistance due to the improved cohesive strength of the pressure-sensitive adhesive layer 20. As a result, when the decorative sheets 1 are attached with their edges butted together, for example, the pressure-sensitive adhesive layer 20 can suppress shrinkage of the substrate 10 over time, and the occurrence of gaps (openings) is suitably suppressed.

[0101] [2] Manufacturing method of decorative sheet The decorative sheet 1 may be produced by any method, but can be suitably produced, for example, by a method comprising a first step of preparing an ultraviolet-curable hot-melt adhesive composition, a second step of applying the ultraviolet-curable hot-melt adhesive composition to the substrate 10, and a third step of curing the ultraviolet-curable hot-melt adhesive composition applied to the substrate 10.

[0102] [2-1] First step In the first step, an ultraviolet-curable hot-melt adhesive composition is prepared for forming the adhesive layer 20. The adhesive composition is produced by blending the above-mentioned components constituting the adhesive layer 20, including the adhesive, in appropriate ratios.

[0103] It is preferable to add a tackifier and a flame retardant to the ultraviolet-curable hot-melt pressure-sensitive adhesive composition.

[0104] [2-2] Second step In the second step, an ultraviolet-curable hot-melt adhesive composition is applied to one surface of the substrate 10 to form an adhesive layer 20 .

[0105] A melt extrusion method can be suitably employed as a method for forming the pressure-sensitive adhesive layer 20. More specifically, the pressure-sensitive adhesive layer 20 can be suitably formed by supplying a molten ultraviolet-curable hot-melt pressure-sensitive adhesive composition onto the substrate 10 from a T-die or the like using an extruder.

[0106] When forming the adhesive layer 20 (when supplying the ultraviolet-curable hot-melt adhesive composition onto the substrate 10), the adhesive composition needs only to be heated so as to melt, and the temperature of the adhesive composition (coating temperature) is preferably 120°C or higher and 210°C or lower, and more preferably 130°C or higher and 190°C or lower.

[0107] The softening point of the ultraviolet-curable hot-melt pressure-sensitive adhesive composition is preferably 90°C or higher and 150°C or lower, and more preferably 100°C or higher and 150°C or lower.

[0108] The melt viscosity of the ultraviolet-curable hot-melt pressure-sensitive adhesive composition at 160°C is preferably 2000 mPa·s or more and 13000 mPa·s or less, and more preferably 4000 mPa·s or more and 12000 mPa·s or less.

[0109] The melt viscosity of the ultraviolet-curable hot-melt pressure-sensitive adhesive composition can be determined by measurement in accordance with JIS K6862:1984.

[0110] [2-3] Third step In the third step, the adhesive layer 20 is cured by irradiating it with light including ultraviolet light.

[0111] The pressure-sensitive adhesive layer 20 is cured by irradiating it with light containing ultraviolet rays from an ultraviolet light source (ultraviolet irradiator).

[0112] Examples of ultraviolet light sources include high-pressure mercury UV lamps, low-pressure mercury UV lamps, metal halide UV lamps, excimer lamps, light-emitting diodes (LEDs), etc. Among these, high-pressure mercury UV lamps and metal halide UV lamps are preferred.

[0113] When the pressure-sensitive adhesive layer 20 is irradiated with ultraviolet light, a crosslinking reaction occurs, and the pressure-sensitive adhesive composition is cured.

[0114] The pressure-sensitive adhesive layer 20 thus formed has a crosslinked structure and has improved cohesive strength.

[0115] By the method described above, the adhesive layer 20 can be formed on the surface of the substrate 10, and the decorative sheet 1 can be obtained.

[0116] Furthermore, the method for producing a decorative sheet may include a fourth step of laminating a release liner 30 onto the pressure-sensitive adhesive layer 20 formed on the substrate 10.

[0117] Furthermore, when obtaining a decorative sheet 1 in which the surface of the pressure-sensitive adhesive layer 20 (the surface opposite to the surface facing the substrate 10) is covered with a release liner 30, a step of covering the surface of the pressure-sensitive adhesive layer 20 before curing with a release liner 30 may be provided between the second and third steps described above. In such a case, in the third step, a substrate 10 or release liner 30 that is UV-transparent is used, and UV light is irradiated onto the pressure-sensitive adhesive layer 20 through the substrate 10 or release liner 30, thereby allowing the pressure-sensitive adhesive layer 20 to be cured appropriately.

[0118] In the manufacturing method of this embodiment, a non-solvent-based adhesive, an ultraviolet-curable hot-melt adhesive, is used as the adhesive, which not only reduces the amount of volatile organic compounds (VOCs) emitted during the production of decorative sheets, but also reduces the amount of residual solvent in the product after production.

[0119] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these.

[0120] For example, the decorative sheet of the present invention may further comprise components other than those described above. For example, the decorative sheet of the present invention may comprise a coating layer (e.g., a coating layer for printing) or an intermediate layer.

[0121] Furthermore, the decorative sheet of the present invention may be produced by any method, and is not limited to those produced by the methods described in the above-mentioned embodiments. [Example]

[0122] The present invention will be described in detail below based on specific examples, but the present invention is not limited thereto. Treatments and measurements in the following examples, for which no temperature conditions are specified, were carried out at room temperature (23°C).

[0123] [3] Manufacturing of decorative sheets Example 1 (1) Manufacturing of substrate First, a molten composition containing the above components in the proportions of 100 parts by mass of polyvinyl chloride, 20 parts by mass of dioctyl phthalate, 5 parts by mass of epoxy plasticizer, 2 parts by mass of barium zinc stabilizer, and 10 parts by mass of titanium oxide (pigment) was formed into a film having a thickness of 160 μm using a calendar roll to obtain a substrate.

[0124] (2) Production of UV-curable hot-melt adhesive composition 100 parts by mass of an ultraviolet-curable acrylic resin having a benzophenone structure in the side chain (acResin A204UV, manufactured by BASF, glass transition temperature: -34°C), 30 parts by mass of a styrene-based tackifier (YS Resin SX100, manufactured by Yasuhara Chemical Co., Ltd.), 15 parts by mass of a bromine-based flame retardant (DAIGUARD D-850, manufactured by Daihachi Chemical Industry Co., Ltd.), and 15 parts by mass of a phosphorus-based flame retardant (EB-70, manufactured by Manac Corporation) were blended and kneaded using a heated kneader at 130°C for 20 minutes under a nitrogen purge to obtain an ultraviolet-curable hot-melt pressure-sensitive adhesive composition.

[0125] (3) Manufacture of decorative sheets The obtained ultraviolet-curable hot-melt pressure-sensitive adhesive composition was applied to the substrate obtained above in a molten state using a slot die type hot-melt coater to a thickness of 50 μm. Thereafter, the pressure-sensitive adhesive composition layer was irradiated with a high-pressure mercury lamp (manufactured by Eye Graphics Co., Ltd.) with an integrated light dose of 30 mJ / cm in the UV-C region. 2 The adhesive layer was formed by irradiating the adhesive with ultraviolet light under the conditions of

[0126] A release liner (thickness: 135 μm) was laminated onto the resulting pressure-sensitive adhesive layer to obtain a decorative sheet consisting of substrate / pressure-sensitive adhesive layer / release liner.

[0127] (Comparative Example 1) (1) Production of hot melt adhesive composition A non-UV-curable rubber-based hot-melt adhesive composition was obtained by blending 100 parts by mass of styrene-isoprene-styrene block copolymer rubber (styrene content 15% by mass, diblock content 40% by mass), 65 parts by mass of petroleum resin-based tackifier (Quinton E200SN, manufactured by Zeon Corporation), 15 parts by mass of paraffin-based process oil, 15 parts by mass of bromine-based flame retardant (DAIGUARD D-850, manufactured by Daihachi Chemical Industry Co., Ltd.), and 15 parts by mass of phosphorus-based flame retardant (EB-70, manufactured by Manac Corporation). The mixture was kneaded in a heated kneader at 140°C for 20 minutes under a nitrogen purge to obtain a non-UV-curable rubber-based hot-melt adhesive composition.

[0128] (2) Manufacturing of decorative sheets The obtained pressure-sensitive adhesive composition was applied to a substrate in a molten state using a slot die type hot melt coater to a thickness of 50 μm to form a pressure-sensitive adhesive layer. The substrate used was one produced in the same manner as described in Example 1.

[0129] A release liner (thickness: 135 μm) was laminated onto the resulting pressure-sensitive adhesive layer to obtain a decorative sheet consisting of substrate / pressure-sensitive adhesive layer / release liner.

[0130] [4] Evaluation The decorative sheets of the above-mentioned Examples and Comparative Examples were evaluated as follows.

[0131] [4-1] Amount of opening The decorative sheets of the Examples and Comparative Examples were cut to a width of 50 mm and a length of 50 mm, and then the release liner was peeled off and the sheets were attached to an aluminum plate. A cross cut of 30 mm in the width direction and 30 mm in the length direction was made in each of the attached samples, and after storing them at 70°C for 48 hours, the width of the cut opening was measured and evaluated according to the following criteria.

[0132] ○: The opening width was less than 2 mm. ×: The opening width was 2 mm or more.

[0133] [4-2] Constant load resistance The decorative sheets of the Examples and Comparative Examples were cut to a width of 25 mm and a length of 150 mm, and the release liner was peeled off from one end of the sample to 50 mm, and the sample was attached to a stainless steel plate. The stainless steel plate was placed horizontally in a thermostatic chamber at 40°C with the surface to which the sample was attached facing downwards, and a load of 9.8 N was applied to the other end of the sample so that the sample would peel off in the vertical direction. After 5 hours, the condition of the sample was visually inspected, and the constant load resistance was evaluated according to the following criteria.

[0134] ○: The sample did not fall. ×: The sample was completely peeled off and dropped.

[0135] [4-3] Holding power Using the decorative sheets of the above examples and comparative examples, tests were carried out at 40°C in accordance with the method described in JIS Z 0237:2022, and the time to fall was measured. If the sheet had not fallen after 50,000 seconds, it was recorded as 50,000 seconds or more. These results are summarized in Table 1.

[0136] [Table 1]

[0137] As is clear from Table 1, excellent results were obtained with the decorative sheet of the present invention. It was also confirmed that the decorative sheet of the present invention has sufficient cohesive strength and shrinkage resistance. In contrast, the comparative examples did not provide satisfactory results. In particular, in comparative example 1, cohesive failure of the pressure-sensitive adhesive layer was confirmed in the evaluation of [4-2] above.

[0138] In addition, in the production of the ultraviolet-curable hot-melt pressure-sensitive adhesive composition, a decorative sheet was produced and evaluated in the same manner as in Example 1, except that a hydrogenated terpene phenol resin or a hydrogenated rosin resin was used as the tackifier instead of the styrene resin, and the same good results as above were obtained.

[0139] In addition, decorative sheets were produced and evaluated in the same manner as in Example 1, except that the content of tackifier in the adhesive layer per 100 parts by mass of adhesive was varied within the range of 5 parts by mass or more and 40 parts by mass or less, and good results were obtained as described above. [Explanation of symbols]

[0140] 1...Decorative sheet 10...Base material 20...Adhesive layer 30...Release liner

Claims

1. a substrate made of a material containing polyvinyl chloride; and a pressure-sensitive adhesive layer containing an ultraviolet-curable hot-melt pressure-sensitive adhesive.

2. The decorative sheet according to claim 1 , wherein the adhesive layer contains an acrylic adhesive as the ultraviolet-curable hot-melt adhesive.

3. The decorative sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer contains a tackifier.

4. The decorative sheet according to claim 3, wherein the content of the tackifier in the pressure-sensitive adhesive layer is 5 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the pressure-sensitive adhesive.

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