Decorative sheet

Abstract

To provide a decorative sheet which has a simple configuration and can be inexpensively manufactured, has high designability, and has good adhesion between a transparent resin layer and a base material layer.SOLUTION: A decorative sheet 1 has a base material layer 10, a printing layer 20 partially printed on the base material layer 10, and a transparent resin layer 30 laminated on the base material layer 10 across the printing layer 20. The printing layer 20 has a thickness of 3 μm or more and 12 μm or less, at least a part thereof is embedded in the base material layer 10, and storage elastic modulus at 165°C of the base material layer 10 is smaller than storage elastic modulus at 165°C of the transparent resin layer 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a decorative sheet that is attached to an article to decorate the article. [Background technology]

[0002] Decorative sheets have been used for a long time to be attached to the surface of items such as furniture and fixtures to add decoration. In recent years, there has been an increasing demand for decorative sheets (wrapping sheets) with patterns to decorate the exterior of automobiles. In a decorative sheet having a design, a printed layer corresponding to the pattern of the design is partially formed on a base layer, and the design of this printed layer is imparted to the sheet. Patent Documents 1 to 3 disclose decorative sheets in which a printed layer is partially formed on a base layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2007 / 116942 [Patent Document 2] Japanese Patent Application Publication No. 3-224736 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-239926 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, in order to improve durability, a decorative sheet with a printed pattern needs to have a transparent resin layer laminated on the surface side (the side where the printed layer is provided). However, because the printed layer on which the pattern is printed is provided partially, the following problems arise depending on the thickness of the printed layer portion.

[0005] In order to improve the design, it is basically desirable that the printed layer be thick. However, if the printed layer is too thick, the step at the boundary between the part where the printed layer is provided and the other part becomes large. The transparent resin layer is provided on the base layer on which the printed layer is provided by thermal lamination, but during this process, voids are generated at the edge of the printed layer where the step of the printed layer occurs, and there is a concern that this will result in a decrease in adhesion. On the other hand, if the printing layer is made too thin in order to prevent the occurrence of the voids, there is a concern that the hiding power of the base may be insufficient, or the depth of the color or pearl may be insufficient, resulting in a decrease in design.

[0006] As a countermeasure to the above problem, it is conceivable to provide an adhesive layer or a pressure-sensitive adhesive layer between the substrate layer and the transparent resin layer to fill the step. However, in this case, the manufacturing process becomes complicated and the amount of material increases, resulting in an increase in cost. In addition, a new problem arises in that the ability of the transparent resin layer to follow deformation of the substrate decreases. In addition, it becomes necessary to consider the environmental resistance of the adhesive layer or the pressure-sensitive adhesive layer.

[0007] An object of the present invention is to provide a decorative sheet that has a simple structure, can be manufactured inexpensively, has a high designability, and has good adhesion between the transparent resin layer and the substrate layer. [Means for solving the problem]

[0008] The present invention solves the above-mentioned problems by the following means: For ease of understanding, the following description will be given with reference to the corresponding embodiments of the present invention, but the present invention is not limited to these.

[0009] The first invention is a decorative sheet (1) comprising a base layer (10), a partially printed printing layer (20) arranged on top of the base layer (10), and a transparent resin layer (30) laminated on the base layer (10) with the printing layer (20) sandwiched between them, wherein the printing layer (20) has a thickness of 3 μm or more and 12 μm or less, and at least a portion of the printing layer (20) is embedded in the base layer (10), and the storage modulus of the base layer (10) at 165°C is smaller than the storage modulus of the transparent resin layer (30) at 165°C.

[0010] A second invention is the decorative sheet (1) according to the first invention, wherein the storage modulus of the base layer (10) at 165° C. is 1.5 MPa or less.

[0011] The third invention is the decorative sheet (1) according to the first or second invention, wherein the base layer (10) contains 31 to 45 parts by mass of a polyester plasticizer per 100 parts by mass of vinyl chloride resin.

[0012] A fourth invention is the decorative sheet (1) according to any one of the first to third inventions, wherein the transparent resin layer (30) contains an acrylic resin and the printing layer (20) contains an acrylic resin.

[0013] The fifth invention is the decorative sheet (1) according to any one of the first to fourth inventions, wherein the printed layer (20) is entirely embedded in the base material layer (10).

[0014] A sixth aspect of the present invention is the decorative sheet (1) according to any one of the first to fifth aspects of the present invention, which is used for the body of an automobile.

[0015] The seventh invention is a method for manufacturing a decorative sheet according to any one of the first to sixth inventions, comprising the steps of forming the printing layer (20) on the base layer (10) or the transparent resin layer (30), and thermally laminating the transparent resin layer (30) to the base layer (10) with the printing layer (20) sandwiched therebetween at a temperature of 150°C or higher and 170°C or lower. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a decorative sheet that has a simple structure, can be manufactured at low cost, has a high designability, and has good adhesion between the transparent resin layer and the substrate layer. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing an embodiment of a decorative sheet 1 according to the present invention. [Figure 2] 2A to 2C are diagrams illustrating a method for manufacturing the decorative sheet 1. [Figure 3] FIG. 10 is a cross-sectional view of a decorative sheet 100 in which the printed layer 20 is not embedded in the base layer 10 side. [Figure 4] FIG. 10 is a diagram showing the results of comparative evaluation. [Figure 5] FIG. 2 is a micrograph showing a cross section of the decorative sheet 1. [Figure 6] FIG. 1 is a cross-sectional view showing an embodiment of a decorative sheet 2 according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

[0019] (Embodiment) FIG. 1 is a cross-sectional view showing an embodiment of a decorative sheet 1 according to the present invention. Note that the figures shown below, including Figure 1, are schematic diagrams, and the size and shape of each part are exaggerated or omitted as appropriate to make them easier to understand. In the following description, specific numerical values, shapes, materials, etc. are given, but these can be changed as appropriate. The specific numerical values ​​specified in the specification and claims should be treated as including a general margin of error. In other words, a difference of about ±10% is not substantially different, and values ​​set within a range slightly exceeding the numerical range of the present invention should be interpreted as being substantially within the scope of the present invention.

[0020] The decorative sheet 1 of this embodiment can impart excellent design and weather resistance to adherends, particularly those with three-dimensional curved surfaces. This decorative sheet is suitable for use on automobile bodies, but is not limited thereto. It can also be used for interior or exterior (exterior) covering materials for vehicles such as railway cars, ships, and airplanes, panel materials for various signs and outdoor advertisements, wall materials (exterior and interior materials) for buildings, fittings such as partitions, doors, and window frames, desks, dining tables, cupboards, counter tables, sinks, furniture, interior decorations, and the like. The decorative sheet 1 of this embodiment includes a base layer 10, a printing layer 20, a transparent resin layer 30, and an adhesive layer 40. The decorative sheet 1 of this embodiment is a hand-applied decorative sheet that is manually attached to an object.

[0021] <Base material layer> The storage modulus of the base material layer 10 at 165°C is smaller than the storage modulus of the transparent resin layer 30 at 165°C. This makes the base material layer 10 more easily deformable than the transparent resin layer 30 during thermal lamination, which will be described later. By performing thermal lamination in this state, the printing layer 20 becomes embedded in the base material layer 10. Note that the base material layer 10 is not limited to being colorless and transparent, and may contain a colorant.

[0022] The storage modulus (E') of the base material layer 10 at 165°C, as measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 165°C, is preferably 0.2 MPa or more and 1.5 MPa or less. When the storage modulus is 0.2 MPa or more, the base material layer 10 is not too soft and tends to have sufficient strength as the base material layer 10, while when the storage modulus is 1.5 MPa or less, the base material layer 10 is not too hard and tends to allow sufficient embedding of the printing layer 20. In this specification, the storage modulus at 165°C is a value measured in accordance with JIS K 7244-4:1999 using a dynamic modulus measuring device (DVA-225 manufactured by IT Measurement & Control Co., Ltd.) at a frequency of 10 Hz, a temperature of 165°C, a heating rate of 5°C / min, a sample width of 5 mm, a chuck distance of 10 mm, an upper limit elongation of 200%, and a minimum load of 1 mN, and the same value is obtained before and after lamination or thermal lamination.

[0023] The storage modulus of the base material layer 10 can be adjusted to fall within the above range by, for example, optimizing the type and amount of plasticizer in the vinyl chloride resin, changing the type of resin, or optimizing the density or molecular weight of the resin. In this embodiment, the base material layer 10 used contains 100 parts by mass of 150 μm polyvinyl chloride and 31 parts by mass, 39 parts by mass, or 45 parts by mass of polyester plasticizer.

[0024] The vinyl chloride resin is mainly polyvinyl chloride (PVC) obtained by polymerizing vinyl chloride monomer, but the following copolymers obtained by copolymerizing vinyl chloride monomer with other monomers can also be used. Monomers copolymerizable with vinyl chloride monomer include vinyl esters such as vinyl acetate and vinyl propionate; acrylic esters such as methyl acrylate and butyl acrylate; methacrylic esters such as methyl methacrylate and ethyl methacrylate; maleic esters such as butyl maleate and diethyl maleate; fumaric esters such as dibutyl fumarate and diethyl fumarate; vinyl ethers such as vinyl methyl ether, vinyl butyl ether and vinyl octyl ether; vinyl cyanides such as acrylonitrile and methacrylonitrile; olefins such as ethylene, propylene, butylene, and styrene; dienes such as isoprene and butadiene; vinylidene halides other than vinyl chloride, such as vinylidene chloride and vinyl bromide, and vinyl halides; and allyl phthalates such as diallyl phthalate. These monomers may be used alone or in combination of two or more.

[0025] Furthermore, as the vinyl chloride resin, a graft copolymer in which a vinyl chloride monomer is grafted onto the following polymers can also be used: Examples of polymers to which a vinyl chloride monomer is grafted include ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl acrylate-carbon monoxide copolymer, ethylene-methyl methacrylate copolymer, and ethylene-propylene copolymer.

[0026] The average degree of polymerization of the vinyl chloride resin is preferably 500 to 4000, more preferably 700 to 3900, and even more preferably 1000 to 3800. When the average degree of polymerization is within the above range, excellent mechanical strength and excellent moldability can be obtained. The average degree of polymerization is the average degree of polymerization measured in accordance with JIS K6721.

[0027] A plasticizer is added to the vinyl chloride resin used as the base layer 10 to adjust the storage modulus, hardness, elastic modulus, etc., in order to enhance the embedding properties of the printing layer 20. The plasticizer is not particularly limited as long as it is compatible with the vinyl chloride resin, and examples thereof include phthalate-based plasticizers such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and diundecyl phthalate (DUP); adipate-based plasticizers such as dibutyl adipate; phosphate-based plasticizers such as tributyl phosphate, tricresyl phosphate, and triphenyl phosphate; trimellitic acid-based plasticizers such as tributyl trimellitate and trioctyl trimellitate; various known polyester-based plasticizers such as adipate-based polyesters; and citric acid esters such as acetyl tributyl citrate and acetyl trioctyl citrate. Of these, polyester-based plasticizers are preferred. These plasticizers may be used alone or in combination of two or more.

[0028] The adipic acid-based polyester plasticizer preferably has a weight-average molecular weight of 1,000 to 3,000. The adipic acid-based polyester plasticizer is a reaction product of adipic acid and a dihydric alcohol, such as ethylene glycol, propylene glycol, butanediol, or 1,6-hexanediol. These dihydric alcohols may be used singly or in combination. Specific examples of the adipic acid-based polyester plasticizer include poly(propylene glycol, adipic acid) ester, poly(butanediol, adipic acid) ester, poly(ethylene glycol, adipic acid) ester, poly(1,6-hexanediol, butanediol, adipic acid) ester, poly(butanediol, ethylene glycol, adipic acid) ester, and poly(ethylene glycol, propylene glycol, butanediol, adipic acid) ester. By using a polymeric plasticizer with an adipic acid polyester plasticizer having a weight average molecular weight of 1,000 or more and 3,000 or less, the embedding properties of the printing layer 20 can be exhibited and bleeding out can be suppressed.

[0029] The content of the plasticizer is preferably 31 to 45 parts by mass, more preferably 34 to 40 parts by mass, and particularly preferably 37 to 39 parts by mass, relative to 100 parts by mass of the vinyl chloride resin. By setting the content of the plasticizer to 31 parts by mass or more, the vinyl chloride resin becomes flexible, allowing the printing layer 20 to be embedded. On the other hand, by setting the content to 45 parts by mass or less, the strength of the base layer 10 can be maintained and bleeding out of the plasticizer can be suppressed.

[0030] Examples of resins other than vinyl chloride resins that can be used for the base layer 10 include thermoplastic polyurethane (TPU), PVA, and EVA.

[0031] The thickness of the base layer 10 is preferably 80 to 180 μm. A thickness of 80 to 180 μm is advantageous in terms of bending processability in wrapping, etc. The base layer 10 may be colored.

[0032] <Print layer> The printing layer 20 is a pattern layer on which the pattern (design) of the decorative sheet 1 is formed. Examples of binder resins constituting the printing layer 20 include acrylic resins, vinyl chloride-vinyl acetate copolymer resins, and acrylic-(vinyl chloride-vinyl acetate copolymer) resins. Among these, from the viewpoint of embedding in the base layer 10, it is preferable to include an acrylic resin having a higher storage modulus and hardness than the base layer 10. Note that in the present invention, the base layer 10 is adjusted to be soft, making it possible for the printing layer 20 to be embedded in the base layer 10, so there is no need to include a photocurable component in the printing layer as in Patent Document 1. This allows for the use of a normal printing layer, and the photocuring process is unnecessary.

[0033] As described above, adjusting the base layer 10 to be soft allows the printing layer 20 to be embedded in the base layer 10, so the storage modulus of the printing layer 20 at 165°C is not particularly limited, but is preferably greater than the storage modulus of the base layer 10 at 165°C. Furthermore, the storage modulus of the printing layer 20 at 165°C is preferably 2 MPa or more and 15 MPa or less. If it is 2 MPa or more, the printing layer 20 is more likely to be embedded in the base layer 10, and if it is 15 MPa or less, cracking of the printing layer 20 during wrapping is more likely to be prevented.

[0034] The storage modulus of the printed layer 20 at 165°C can be adjusted, for example, by adjusting the molecular weight of the binder resin, or, when multiple binder resins are used, by adjusting the compounding ratio thereof.

[0035] Various color pigments, color dyes, etc. are added to the printed layer 20. The printed layer 20 can be formed by, for example, screen printing, gravure printing, etc. In this embodiment, the printed layer 20 is partially formed on the base layer 10 by applying a printing ink containing a mixed resin of vinyl chloride-vinyl acetate copolymer and acrylic resin as a binder using a gravure printing method. The printed layer 20 has a thickness of 3 μm or more and 12 μm or less. Furthermore, the thickness of the printed layer 20 is preferably 6 μm or more. In this specification, the thickness of the printed layer means the maximum value measured at 20 random locations.

[0036] The thickness of the printed layer embedded in the base material layer 10 is, for example, 1 to 10 μm. The thickness of the printed layer present in the transparent resin layer 30 is preferably 3 μm or less, and more preferably 2 μm or less. Within this range, the effects of the present invention can be more effectively obtained.

[0037] <Transparent resin layer> The transparent resin layer 30 is a transparent resin layer laminated on the base material layer 10 with the printed layer 20 sandwiched therebetween, and is provided to protect the printed layer 20.

[0038] The transparent resin layer 30 is required to have a higher storage modulus and hardness than the above-described base layer 10, so that the printing layer 20 is embedded in the base layer 10. From this viewpoint, the transparent resin layer 30 preferably contains an acrylic resin. The thickness of the transparent resin layer 30 is preferably 30 μm or more and 100 μm or less, and more preferably 40 μm or more and 90 μm or less.

[0039] The acrylic resin is not particularly limited as long as it can be formed into a film or sheet by a calendaring method, and any known acrylic resin can be appropriately selected and used. Specific examples include polymers or copolymers of methacrylic acid or methacrylic acid esters, such as polymethyl (meth)acrylate (PMMA), and copolymers of alkyl methacrylate, alkyl acrylate, and styrene.

[0040] The transparent resin layer 30 may have a two-layer structure consisting of an acrylic resin layer located on the substrate layer side and a fluororesin-containing layer located on the surface side. The term "fluororesin" refers to a polymer containing a fluorine-containing monomer as a polymerization component. Examples of fluororesins include resins containing a polymerization component selected from tetrafluoroethylene, trifluorochloroethylene, vinyl fluoride, and vinylidene fluoride. More specific examples of fluororesins in the present invention include homopolymers of fluorine-containing polymerization components such as tetrafluoroethylene resin, vinyl fluoride resin, and vinylidene fluoride resin, as well as copolymers containing the above polymerization components, such as trifluorochloroethylene-vinylidene fluoride copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer. The thickness of the fluororesin-containing layer 16 is preferably 3 μm to 20 μm, more preferably 5 μm to 15 μm.

[0041] As the transparent resin layer 30 of this embodiment, for example, a commercially available laminate in which an acrylic resin layer and a fluororesin layer are laminated by co-extrusion can be used. Examples of such a laminate film include ACRYPLEN FBS006 manufactured by Mitsubishi Chemical Corporation, FT-50Y manufactured by Kureha Corporation, and DX film manufactured by Denka Company Limited.

[0042] The storage modulus of the transparent resin layer 30 at 165°C is greater than the storage modulus of the base layer 10 at 165°C. This allows the printing layer 20 to be embedded within the base layer 10. Specifically, the storage modulus (E') measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 165°C is preferably 4 MPa or more and 15 MPa or less. If it is 4 MPa or more, the transparent resin layer 30 is not too soft, and the printing layer 20 tends to be sufficiently embedded in the base layer 10. If it is 15 MPa or less, the processability and shape followability during thermal lamination tend to be good. The storage modulus can be measured using a conventionally known dynamic modulus measuring device (DMA).

[0043] The storage modulus of the transparent resin layer 30 can be adjusted to fall within the above range by, for example, changing the type of resin or optimizing the density or molecular weight of the resin.

[0044] <Adhesive layer> The adhesive layer 40 is an adhesive layer for attaching the decorative sheet 1 to an article. There are no particular limitations on the adhesive used for the adhesive layer 40, but examples of adhesives that can be used include rubber-based, acrylic-based, olefin-based, polyester-based, and polyurethane-based adhesives. If necessary, a separator may be provided that is temporarily bonded to and covers the adhesive layer 40.

[0045] Next, a method for manufacturing the decorative sheet 1 will be described. FIG. 2 is a diagram illustrating a method for manufacturing the decorative sheet 1. As shown in FIG. First, the print layer 20 is printed on one surface (the upper surface in FIG. 2) of the base material layer 10, and then dried (FIG. 2(a)).

[0046] Next, a transparent resin sheet that will become the transparent resin layer 30 is placed on the side on which the printing layer 20 is provided (Figure 2(b)), and the base material layer 10 and the transparent resin layer 30 are thermally laminated by passing them between pressure rollers (not shown) heated to a temperature of 150°C or higher and 170°C or lower. Here, the storage modulus of the base material layer 10 in this embodiment at 165°C is 1.1 MPa. The storage modulus of the transparent resin layer 30 at 165°C is 4.7 MPa. That is, the storage modulus of the base material layer 10 at 165°C is smaller than the storage modulus of the transparent resin layer 30 at 165°C. Therefore, when thermally laminated, the base material layer 10 is more easily deformed than the transparent resin layer 30. By performing thermal lamination in this state, the printing layer 20 is embedded in the base material layer 10. By setting the thermal lamination temperature to 150°C or higher, the laminate strength is increased, and the transparent resin layer 30 is less likely to peel off from the base layer 10 when the decorative sheet 1 is attached to an object while being stretched. Furthermore, by setting the thermal lamination temperature to 170°C or lower, the base layer 10 can be made more easily deformable than the transparent resin layer 30, so the printing layer 20 can be embedded in the base layer 10 side.

[0047] FIG. 3 is a cross-sectional view of a decorative sheet 100 in which the printed layer 20 is not embedded in the base layer 10 side. 3, in the decorative sheet 100, the printing layer 20 is not embedded in the base layer 10. In this state, the protrusion of the printing layer 20 creates a large step, which can result in thermal lamination with voids 21 remaining near the edges of the printing layer 20. If voids 21 remain, this can result in a decrease in adhesion. In contrast, in the decorative sheet 1 of this embodiment, at least a portion of the printed layer 20 is embedded in the base material layer 10, thereby reducing the amount of protrusion of the printed layer 20 toward the transparent resin layer 30, and as a result, no voids remain after thermal lamination. The amount of the printed layer 20 embedded in the base material layer 10 varies depending on the storage modulus of the base material layer 10 and the transparent resin layer 30, but it is desirable for 40% or more of the thickness of the printed layer 20 to be embedded in the base material layer 10 to prevent the generation of voids. Alternatively, the entire printed layer 20 may be embedded in the base material layer 10, as in the decorative sheet 2 shown in FIG. 6.

[0048] Next, the present invention will be described in more detail with reference to several examples and comparative examples, but the present invention is not limited to the following examples.

[0049] Example 1 A vinyl chloride resin (storage modulus at 165°C: 1.1 MPa) containing a plasticizer and having a thickness of 150 μm was used as the base layer 10. The plasticizer was a polyester plasticizer, with 39 parts by mass added to 100 parts by mass of the vinyl chloride resin. One surface of this base layer 10 was gravure printed using a printing ink (storage modulus at 165°C: 3.0 MPa) containing a mixed resin of vinyl chloride-vinyl acetate copolymer and acrylic resin as a binder, to form the printed layer 20. A 50 μm thick transparent resin layer 30 (FBS007 manufactured by Mitsubishi Chemical Corporation, storage modulus at 165°C: 4.7 MPa), consisting of a 45 μm acrylic resin layer and a 5 μm fluororesin layer laminated by co-extrusion, was heat-laminated onto the surface of the printed layer 20 at a set temperature of 165°C to produce a decorative sheet. The roll material was metal, and the sheet was pressed at 2.5 tons against a width of 1300 mm to heat-laminate the acrylic resin layer side and the printed layer 20 side. The thickness of the printed layer 20 of the prepared decorative sheet was 12 μm.

[0050] Example 2 A decorative sheet having a printing layer 20 of 6 μm thickness was produced using the same materials and conditions as in Example 1, except that the thickness of the printing ink in the gravure printing was changed.

[0051] Example 3 A decorative sheet with a printing layer 20 having a thickness of 3 μm was produced using the same materials and conditions as in Example 1, except that the thickness of the printing ink in the gravure printing was changed.

[0052] Example 4 A decorative sheet was produced using the same materials and conditions as in Example 2, except that a 150 μm thick vinyl chloride resin (storage modulus at 165°C: 1.4 MPa) containing 31 parts by mass of polyester plasticizer added to 100 parts by mass of vinyl chloride resin was used as the base layer 10.

[0053] Example 5 A decorative sheet was produced using the same materials and conditions as in Example 2, except that a 150 μm thick vinyl chloride resin (storage modulus at 165°C: 0.8 MPa) containing 45 parts by mass of polyester plasticizer added to 100 parts by mass of vinyl chloride resin was used as the base layer 10.

[0054] Example 6 A decorative sheet was produced using the same materials and conditions as in Example 5, except that a 50 μm transparent resin layer 30 of acrylic resin (HBS006H manufactured by Mitsubishi Chemical Corporation, storage modulus at 165° C.: 1.0 MPa) was used.

[0055] (Comparative Example 1) A decorative sheet with a printing layer 20 having a thickness of 15 μm was produced using the same materials and conditions as in Example 1, except that the thickness of the printing ink in the gravure printing was changed.

[0056] (Comparative Example 2) A decorative sheet having a printing layer 20 of 2 μm thickness was produced using the same materials and conditions as in Example 1, except that the thickness of the printing ink in the gravure printing was changed.

[0057] (Comparative Example 3) A decorative sheet was produced using the same materials and conditions as in Example 2, except that a 100 μm thick PET (storage modulus at 165° C.: 590 MPa) was used as the base layer 10 .

[0058] Comparative Example 4 A decorative sheet was produced using the same materials and conditions as in Example 2, except that the base layer 10 was a 120 μm thick vinyl chloride resin (storage modulus at 165°C: 2.0 MPa) in which 28 parts by mass of polyester plasticizer was added to 100 parts by mass of vinyl chloride resin, and the transparent resin layer 30 was a 50 μm thick transparent resin layer 30 (DX-14S0250, manufactured by Denka Company Ltd., storage modulus at 165°C: 1.3 MPa) in which an acrylic resin layer and a fluororesin layer were laminated by co-extrusion.

[0059] (Comparative Example 5) A decorative sheet was produced using the same materials and conditions as in Example 2, except that a 120 μm thick vinyl chloride resin (storage modulus at 165°C: 2.0 MPa) containing 28 parts by mass of polyester plasticizer added to 100 parts by mass of vinyl chloride resin was used as the base layer 10, and a 50 μm thick acrylic resin transparent resin layer 30 (HBS006H manufactured by Mitsubishi Chemical Corporation, storage modulus at 165°C: 1.0 MPa) was used.

[0060] FIG. 4 is a diagram showing the results of the comparative evaluation. In the column for evaluating the base hiding ability in Figure 4, ◯ indicates that the base was sufficiently hidden by the printing layer, △ indicates that the base was slightly visible through the printing layer but was still usable, and × indicates that the base was clearly visible through the printing layer and was therefore unusable. In addition, in the column for evaluating defects during lamination in Figure 4, ◯ indicates that there are no air bubbles in the laminate surface and there are no problems with adhesion, △ indicates that air bubbles (voids) are visible with a microscope but there are no problems with the design or adhesion, and × indicates that air bubbles (voids) are visible with the naked eye and there is poor adhesion.

[0061] 4, it can be said that a thickness of 3 μm or more of the printed layer 20 can maintain good design. Also, it can be said that a thickness of 12 μm or less of the printed layer 20 can be thermally laminated with almost no air bubbles mixed in. Furthermore, by comparing the results of Comparative Examples 3 to 5 with the Examples, it was confirmed that the effect of the storage modulus of the base layer 10 at 165°C being smaller than the storage modulus of the transparent resin layer 30 at 165°C was fully exerted.

[0062] Fig. 5 is a micrograph showing a cross section of the decorative sheet 1. Note that Fig. 5 is upside down compared to Figs. 1 to 3 above. The decorative sheet 1 illustrated in Figure 5 has a base layer 10 made of PVC with a thickness of 150 μm, a transparent resin layer 30 which is a laminate of an acrylic resin film (45 μm) with a thickness of 50 μm and a fluororesin film (5 μm), and a printing layer 20 with a thickness of 6 μm, which corresponds to Example 2 in Figure 4. As shown in FIG. 5, it was confirmed that the entire printed layer 20 was embedded in the base material layer 10 in the decorative sheet 1 of this embodiment.

[0063] (Reference example) Decorative sheets were produced in the same manner as in Example 2, except that the thermal lamination temperatures were set to 145°C, 155°C, 165°C, and 175°C. The laminate strength (adhesion) between the transparent resin layer 30 and the base layer 10 of the produced decorative sheets was confirmed. The decorative sheets produced by thermal lamination at a set temperature of 145°C suffered interfacial failure at the bonding interface between the transparent resin layer 30 and the base layer 10, resulting in weak laminate strength. The decorative sheets produced by thermal lamination at set temperatures of 155°C, 165°C, and 175°C suffered cohesive failure within the transparent resin layer 30 or the base layer 10, resulting in strong laminate strength. The laminate strength (adhesion) was confirmed using the following procedure. Prior to thermal lamination, adhesive tape (Nichiban Cellotape (registered trademark)) was applied to a portion of the surface of the base layer 10 that would be bonded to the transparent resin layer 30. The base material layer 10 with adhesive tape attached is placed on the transparent resin layer 30 and thermally laminated. The surface of the base material layer 10 with the adhesive tape attached is not bonded to the transparent resin layer 30, and the surface of the base material layer 10 without the adhesive tape is bonded to the transparent resin layer 30. After a certain time has passed after thermal lamination, the part of the transparent resin layer 30 that is not bonded to the base material layer 10 is held and slowly peeled at 180°C toward the part of the transparent resin layer 30 that is bonded to the base material layer 10.

[0064] In the decorative sheets produced by thermal lamination at set temperatures of 145°C, 155°C, and 165°C, most of the printed layer 20 (more than 70% of the total) was embedded in the base layer 10. In the decorative sheets produced by thermal lamination at a set temperature of 175°C, part of the printed layer 20 was not embedded in the base layer 10. The transparent resin layer 30 of Example 2 had a storage modulus of 2.4 MPa at 145°C, 5.4 MPa at 155°C, 4.7 MPa at 165°C, and 0.8 MPa at 175°C. The base layer 10 of Example 2 had a storage modulus of 1.8 MPa at 145°C, 1.4 MPa at 155°C, 1.1 MPa at 165°C, and 0.8 MPa at 175°C. In addition, the decorative sheet produced by thermal lamination at a set temperature of 175°C had a portion of the printed layer 20 not embedded in the base layer 10, but the evaluation above showed that it had strong lamination strength (adhesion). However, from the viewpoint of long-term reliability, it is preferable that the majority of the printed layer 20 (70% or more of the total) is embedded in the base layer 10.

[0065] The above reference examples show that by focusing on the storage modulus at 165°C of the transparent resin layer 30 and the substrate layer 10, and by making the storage modulus at 165°C of the substrate layer 10 smaller than that of the transparent resin layer 30, and then thermally laminating the transparent resin layer 30 and the substrate layer 10 at a set temperature of 150°C to 170°C, a decorative sheet with high laminate strength and good adhesion, in which most of the printed layer 20 is embedded in the substrate layer 10, can be obtained. A decorative sheet with good adhesion is important for ensuring durability in outdoor environments when used for the exterior of vehicles such as automobiles and train bodies. It is also important for decorative sheets for uses other than exterior applications to have durability that can withstand a variety of usage environments.

[0066] In the above-described manufacturing method, the printing layer 20 is printed on the surface of the base material layer 10, and then thermally laminated with the transparent resin layer 30. The manufacturing method of the decorative sheet 1 is not limited to this, and may be a process of printing the printing layer 20 on the surface of the transparent resin layer 30, and then thermally laminating with the base material layer 10.

[0067] As described above, according to the decorative sheet 1 of this embodiment, the printed layer 20 is embedded in the base material layer 10, so that the decorative sheet can have a high designability and good adhesion between the base material layer 10 and the transparent resin layer 30. Furthermore, the decorative sheet 1 of this embodiment does not require an adhesive layer or the like to be provided between the base material layer 10 and the transparent resin layer 30, so it can be manufactured inexpensively with a simple configuration. [Explanation of symbols]

[0068] 1, 2 Decorative sheet 10 Base material layer 20 printing layer 21 void 30 Transparent resin layer 40 Adhesive layer 100 Decorative sheet (comparison example)

Claims

[Claim 1] a substrate layer; a printing layer that is partially printed and that is disposed on the base layer; a transparent resin layer laminated on the base layer with the printed layer sandwiched therebetween; A decorative sheet comprising: the printing layer has a thickness of 3 μm or more and 12 μm or less, and is at least partially embedded in the base material layer; The decorative sheet has a storage modulus at 165°C of the base layer that is smaller than the storage modulus at 165°C of the transparent resin layer.

Images