Adhesive sheet and decorative adhesive sheet using the same

Abstract

To provide an adhesive sheet which exhibits excellent adhesive strength to PP and a decorative adhesive sheet using the same.SOLUTION: There is provided an adhesive sheet 12 which is an adhesive sheet used for attaching a decorative sheet to an adherend and is provided with an adhesive layer 3. The adhesive strength is 10 N / 25 mm or more under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min under 23°C and 50% relative humidity after 24 hours of attachment to a polypropylene board and the adhesive strength is 5.0 N / 25 mm or more under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 100°C after 48 hours of attachment to a polypropylene board.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to an adhesive sheet used for decorative molding of articles.

Background Art

[0002] For the purpose of decorating automotive interior and exterior parts, building supplies, daily necessities, etc., decorative molding is performed. For example, Japanese Patent Application Laid-Open No. 2014-159154 (Patent Document 1) describes that an acrylic-based base-free pressure-sensitive adhesive sheet is attached to the back surface of a resin base material and used as a decorative pressure-sensitive adhesive sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, polypropylene (hereinafter abbreviated as "PP"), which is light in specific gravity and has good processability, has been attracting attention as a material for adherends and decorative sheets. However, since PP is a non-polar material, for example, when the adherend is made of PP, the decorative pressure-sensitive adhesive sheet may not adhere well. Since it is heated during molding, it is desired that the decorative pressure-sensitive adhesive sheet has a strong adhesive force to the adherend not only at normal temperature but also at high temperature.

[0005] An object of the present invention is to provide an adhesive sheet that exhibits excellent adhesive force to PP and a decorative pressure-sensitive adhesive sheet using the same.

Means for Solving the Problems

[0006] An example of the adhesive sheet disclosed in this specification is an adhesive sheet used for attaching a decorative sheet to a adherend, and it has an adhesive layer. The adhesive strength under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 23°C and a relative humidity of 50% after 24 hours from the attachment to the polypropylene plate is 10 N / 25 mm or more, and the adhesive strength under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 100°C after 48 hours from the attachment to the polypropylene plate is 5.0 N / 25 mm or more.

Advantages of the Invention

[0007] The adhesive sheet disclosed in this specification exhibits excellent adhesive strength to PP, and thus is preferably used for decorative molding using a PP adherend or decorative molding using a decorative sheet having a PP resin sheet.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0009] FIG. 1 is a cross-sectional view showing an example of the adhesive sheet according to an embodiment of the present disclosure. The adhesive sheet 12 shown in the figure includes an adhesive layer 3, a first release liner 1 bonded to one surface of the adhesive layer 3, and a second release liner 5 bonded to the other surface of the adhesive layer 3. The adhesive sheet 12 is an adhesive sheet used for attaching a decorative sheet to a adherend as described later.

[0010] The adhesive strength under the conditions of 23°C, 50% relative humidity, a peeling angle of 180 degrees, and a peeling speed of 300 mm / min, 24 hours after the adhesion to the PP plate of the adhesive layer 3, is 10 N / 25 mm or more. The adhesive strength under the conditions of 100°C, a peeling angle of 180 degrees, and a peeling speed of 300 mm / min, 48 hours after the adhesion to the PP plate of the adhesive layer 3, is 5.0 N / 25 mm or more.

[0011] Thus, not only is the adhesive strength to PP at room temperature high, but also the adhesive strength to PP at high temperatures is high. Therefore, even when the adherend is made of PP, the adhesive sheet 12 can be preferably used as the adhesive layer of the decorative adhesive sheet.

[0012] The storage elastic modulus (G’) of the adhesive layer 3 at 23°C and a frequency of 1 Hz is, for example, greater than 1.0×10 5 Pa and may be 1.0×10 8 Pa or less, or may be greater than 1.0×10 6 Pa and 1.0×10 7 Pa or less. Being within this range makes it easier to follow a three-dimensional adherend and less likely to cause lifting even when the temperature becomes high during molding. When the storage elastic modulus (G’) of the adhesive layer 3 is greater than 1.0×10 6 Pa and 1.0×10 7 Pa or less, it becomes easier to maintain the state where the adhesive sheet 12 follows the adherend after molding.

[0013] The storage elastic modulus (G’) of the adhesive layer 3 at 100°C and a frequency of 1 Hz is, for example, 1.0×10 4 Pa or more and 1.0×10 7 Pa or less, or may be 5.0×10 4 Pa or more and 5.0×10 6 Pa or less.

[0014] The loss elastic modulus (G’’) of the adhesive layer 3 at 23°C and a frequency of 1 Hz is, for example, 1.0×10 5 Pa or more and 1.0×10 8 Pa or less, or may be 5.0×105 Greater than Pa and 1.0×10 7 It may also be below Pa. The loss modulus (G'') of the adhesive layer 3 at 100 °C and a frequency of 1 Hz is, for example, 1.0×10 4 Pa or more and 5.0×10 7 It may be below Pa, and 5.0×10 4 Greater than Pa and 5.0×10 6 It may also be below Pa.

[0015] The tanδ of the adhesive layer 3 at 23 °C and a frequency of 1 Hz is 1.0×10 ー1 Or more and 1.0×10 2 It may also be below.

[0016] The elongation at break of the adhesive layer 3 at 23 °C may be 400% or more, or 500% or more. The elongation at break of the adhesive layer 3 at 100 °C may be greater than the elongation at break of the adhesive layer 3 at 23 °C. In this case, during molding, the followability to the adherend having a three-dimensional shape is good, which is preferable.

[0017] For the production of the adhesive layer 3, for example, one or a mixture of two or more selected from acrylic adhesives, acrylic-urethane adhesives, urethane adhesives, polyester adhesives, silicone adhesives, and rubber adhesives can be used. The adhesive composition for forming the adhesive layer 3 may be thermosetting or photocurable and cured by ultraviolet rays or the like. In the case of thermosetting, it is preferable that the adhesive composition contains a known curing agent. When the adhesive composition contains an acrylic adhesive or an acrylic-urethane adhesive, it is preferable to use an isocyanate curing agent, an epoxy curing agent, or a chelate curing agent, or a mixture of these curing agents as the curing agent.

[0018] The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer 3 may contain a tackifier in order to improve the adhesion to PP. Examples of the tackifier include rosin-based tackifiers and terpene-based tackifiers. The content of the tackifier in the pressure-sensitive adhesive layer 3 may be, for example, about 5% by mass or more and 60% by mass or less, or may be 10% by mass or more and 40% by mass or less. If the addition amount of the tackifier is too small, it is difficult to improve the adhesion to PP. If the addition amount is too large, the holding force may decrease and there may be a tendency for glue residue to occur easily.

[0019] When the pressure-sensitive adhesive layer 3 is formed of a cured product of an acrylic pressure-sensitive adhesive, the pressure-sensitive adhesive layer 3 has an acrylic copolymer containing units derived from butyl acrylate, and the content of the units derived from butyl acrylate is preferably 30% by mass or more based on the total mass of the acrylic copolymer. With this configuration, even when the adherend or the decorative sheet contains PP, a relatively strong adhesive force can be exhibited.

[0020] The thickness of the pressure-sensitive adhesive layer 3 is not particularly limited, and may be, for example, 5 μm or more and 100 μm or less, or may be 10 μm or more and 50 μm or less. When the thickness of the pressure-sensitive adhesive layer 3 is 5 μm or more, the adhesive force to the adherend can be strengthened, and it becomes easier to absorb even when there are irregularities on the surface of the adherend. When the thickness of the pressure-sensitive adhesive layer 3 is 100 μm or less, the manufacturing cost can be suppressed.

[0021] The peeling force A1 required to peel the first release liner 1 from the pressure-sensitive adhesive layer 3 may be greater than the peeling force A2 required to peel the second release liner 5 from the pressure-sensitive adhesive layer 3. With this configuration, when using the adhesive sheet 12, it becomes easy to first peel off the second release liner 5 and bond the pressure-sensitive adhesive layer 3 to the decorative sheet, and then peel off the first release liner 1 and attach it to the adherend.

[0022] The first release liner 1 and the second release liner 5 may each have a laminated structure in which a blocking layer and a release agent layer are formed on the surface of high-quality paper, glassine paper, or the like, or may be a laminate in which a silicone-based or fluorine-based release agent layer is provided on the surface of a resin film such as polyethylene terephthalate (PET).

[0023] As an environmental measure, a recycled material may be used for part or all of the material of the resin film, or a paper-based release liner that is easy to recycle and does not have a resin laminate layer on the surface may be used. Alternatively, a release liner that does not contain PFAS in the release agent layer may be used.

[0024] Figure 2 is a cross-sectional view showing a decorative adhesive sheet using the adhesive sheet 12 shown in Figure 1. As shown in the figure, the decorative adhesive sheet 10 of the present embodiment includes, for example, a decorative sheet 15 having a surface layer 9 and a resin sheet 7 formed on one surface of the surface layer 9, an adhesive layer 3 formed on the surface of the resin sheet 7 opposite to the surface layer 9, and a first release liner 1 formed on the surface of the adhesive layer 3 opposite to the resin sheet 7.

[0025] As the resin sheet 7, a film formed by extruding and stretching resins such as olefin resins, styrene resins, and vinyl chloride resins can be used. In the decorative adhesive sheet 10 of the present embodiment, since the adhesive layer 3 exhibits strong adhesion to PP, the resin sheet 7 may be made of PP. The resin sheet 7 may be a laminate composed of a plurality of resin layers.

[0026] The thickness of the resin sheet 7 is not particularly limited as long as it can prevent dust and uneven shapes on the surface of the adherend from propagating to the surface layer 9 and does not excessively impair the moldability of the decorative adhesive sheet 10. The thickness of the resin sheet 7 may be, for example, 30 μm or more, 50 μm or more, or 80 μm or more, and may be 500 μm or less, 300 μm or less, or 250 μm or less.

[0027] As the surface layer 9, various resins can be used, such as acrylic resins containing polymethyl methacrylate (PMMA), polyurethane, ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), fluororesins such as methyl methacrylate-vinylidene fluoride copolymer (PMMA / PVDF), polyvinyl chloride (PVC), polycarbonate (PC), polyolefins such as polyethylene (PE) and PP, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), copolymers such as ethylene-acrylic acid copolymer (EAA) and its ionomer, ethylene-ethyl acrylate copolymer, and ethylene-vinyl acetate copolymer (EVA) can be used. Because of excellent weather resistance, one or more selected from acrylic resins, polyurethane, fluororesins, and polyvinyl chloride are preferably used as materials. Because of excellent scratch resistance and low environmental load when incinerated or landfilled as waste, acrylic resins or polyurethane are more preferable.

[0028] The thickness of the surface layer 9 is not particularly limited, and for example, it may be 1 μm or more, 5 μm or more, or 10 μm or more, and may also be 150 μm or less, 100 μm or less, or 80 μm or less.

[0029] Although not shown, a design layer may be provided between the resin sheet 7 and the surface layer 9. Examples of the design layer include a color layer containing a plurality of colors or a metal layer, patterns such as wood grain, stone grain, geometric patterns, and leather patterns, a pattern layer for imparting a logo, a pattern, etc. to the structure, and a relief layer. The surface layer 9 itself may be provided as a colored or embossed design layer.

[0030] As described above, the adhesive strength under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 23°C and a relative humidity of 50% after 24 hours from the attachment of the adhesive layer 3 to the PP plate is 10 N / 25 mm or more. The adhesive strength under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 100°C after 48 hours from the attachment of the adhesive layer 3 to the PP plate is 5.0 N / 25 mm or more.

[0031] The decorative adhesive sheet 10 of this embodiment is preferably used for vacuum and pressure forming such as TOM forming.

[0032] 3 is a diagram showing an example of a vacuum pressure-sensitive adhesive sheet-using vacuum pressure-sensitive adhesive forming apparatus. As shown in the figure, a known vacuum pressure-sensitive adhesive forming apparatus 30 has a first vacuum chamber 31 and a second vacuum chamber 32 on the top and bottom, respectively, and a jig for setting the decorative adhesive sheet 10 of the present embodiment to be attached to the adherend 20 is provided between the top and bottom vacuum chambers. In addition, in the lower first vacuum chamber 31, a partition plate 34, a table 25, and a pedestal 33 are installed on a lifting platform 35 that can be raised and lowered up and down, and the adherend 20 having a three-dimensional shape is set on this pedestal 33. The adherend 20 is made of PP. As such a vacuum pressure-sensitive adhesive forming apparatus 30, for example, a double-sided vacuum forming machine (manufactured by Fuse Vacuum Co., Ltd.) can be used.

[0033] During molding, first, the first vacuum chamber 31 and the second vacuum chamber 32 of the vacuum and pressure forming device 30 are opened to atmospheric pressure, and the decorative adhesive sheet 10 is set between the upper and lower vacuum chambers. The decorative adhesive sheet 10 is set with the adhesive layer 3 facing the adherend 20.

[0034] Next, the first vacuum chamber 31 and the second vacuum chamber 32 are closed, and the inside of each chamber is evacuated. Then, the decorative adhesive sheet 10 is heated. After that, the lifting platform 35 is raised to push the adherend 20 up to the second vacuum chamber 32. The heated decorative adhesive sheet 10 is pressed against the adherend 20 and stretched. Next, the second vacuum chamber 32 is filled with an appropriate pressure (0.0 Pa to 2.0×10 5 By setting the pressure inside the vacuum chamber 31 to a pressure of 10 Pa, the decorative adhesive sheet 10 will cover the exposed surface of the adherend 20 due to the pressure difference. Next, the first vacuum chamber 31 and the second vacuum chamber 32 are opened again to return the pressure to atmospheric pressure, and the adherend 20 covered with the decorative adhesive sheet 10 is removed.

[0035] Thereafter, the edge portion of the decorative adhesive sheet 10 that is in close contact with the adherend 20 is trimmed, and the forming process is completed.

[0036] Since the adhesive layer 3 exhibits a stronger adhesive force to the adherend 20 made of PP than conventional ones, when the decorative adhesive sheet 10 is attached to the adherend 20, molding can be performed without floating.

Example

[0037] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by these examples.

[0038] - Preparation of Adhesive Sheet - A coating solution prepared by adding and mixing a predetermined amount of an isocyanate-based curing agent to an acrylic-based adhesive A was applied to the release surface of a first release liner. After application, it was dried at 100 °C to form an adhesive layer with a thickness of 50 μm, and a second release liner was bonded to the exposed surface of the adhesive layer to produce an adhesive sheet as Example 1. The acrylic-based adhesive A has an acrylic copolymer containing units derived from butyl acrylate, and the content of units derived from butyl acrylate is 30% by mass or more based on the total mass of the acrylic copolymer.

[0039] Also, as Comparative Example 1, an adhesive sheet was produced in the same manner as described above using an acrylic-based adhesive B. Further, as Comparative Example 2, "Mold Fit50" manufactured by Nikka Shinkawa Co., Ltd. was prepared. This is a substrate-less sheet in which an acrylic-based adhesive layer with a thickness of 50 μm is sandwiched between a first release liner on the heavy release side and a second release liner on the light release side.

[0040] - Preparation of Decorative Adhesive Sheet - The second release liner on the light release side of the adhesive sheet produced in Example 1 was peeled off, and the exposed adhesive layer was bonded to one surface of a 100-μm-thick PP film to produce a decorative adhesive sheet.

[0041] The adhesive sheets produced in Comparative Example 1 and the adhesive sheet prepared in Comparative Example 2 were also bonded to a 100-μm-thick PP film in the same manner as the adhesive sheet in Example 1 to form decorative adhesive sheets.

[0042] - Preparation of Molded Bodies - The decorative adhesive sheets according to Example 1 were each set in a vacuum pressure forming apparatus manufactured by Fuse Vacuum Co., Ltd., and an adherend made of PP and having a three-dimensional shape was placed on a pedestal, and vacuum pressure forming was carried out. As a result, a molded body having an adherend and a decorative adhesive sheet covering the surface of the adherend was produced. The decorative adhesive sheet according to Comparative Example 2 was also used for vacuum pressure forming in the same manner as the decorative adhesive sheet according to Example 1 to produce a molded body. The molding temperature was 135°C for all.

[0043] - Measurement of Adhesive Strength - Regarding test pieces of each adhesive sheet cut to a width of 25 mm, after peeling off the release liner, a PET film with a thickness of 25 μm was laminated on the back, and the other release liner was peeled off and attached to the adherend. Here, SUS (BA) plates and PP plates were used as adherends. After attaching to the adherend, it was reciprocated once with a 2 kg rubber roller, and then measured 1 minute and 24 hours later. The measurement was carried out under the conditions of 23°C (room temperature) and after leaving at room temperature for 48 hours and then transferring to a 100°C atmosphere. For the measurement, TENSILON RTI-1225 manufactured by A&D Co., Ltd. was used. Three measurements were made for each condition.

[0044] - Measurement of Elongation at Break and Tensile Strength - The adhesive sheets produced in Example 1, Comparative Example 1, and the adhesive sheet prepared in Comparative Example 2 were cut into strips with a width of 37.5 mm and a length of 30 mm, and after peeling off the release liner on the light peeling side, while peeling off the release liner on the heavy peeling side, the adhesive layer was rolled up to create a cylindrical body with a length of 30 mm. Five millimeters at both ends of this cylindrical body were sandwiched between papers, and it was set in a tensile tester (TENSILON RTI-1225) with a 20 mm central part exposed. With both ends of the cylindrical body gripped by the gripping tools, a tensile test was carried out at 23°C, a relative humidity of 50%, and in an environment of 100°C, with a gripping interval of 20 mm and a tensile speed of 300 mm / min to measure the tensile strength and elongation at break.

[0045] - Measurement of Storage Elastic Modulus of Adhesive Sheet - The pressure-sensitive adhesive sheets prepared in Example 1 and Comparative Example 1 and the pressure-sensitive adhesive sheet prepared in Comparative Example 2 were each laminated until the total thickness reached 1 mm, and then punched into tablets having a diameter of 8 mm. These tablets were sandwiched between the plates of a rheometer (product name: AR2000ex), and the storage modulus G' and the loss modulus G'' were measured under the conditions of a frequency of 1 Hz and a strain of 0.05%, and tanδ was calculated. The temperature was measured at both 23°C and 100°C.

[0046] -Measurement Results- Table 1 shows the results of the adhesive force measurement tests of the pressure-sensitive adhesive sheets prepared in Example 1 and Comparative Example 1 and the pressure-sensitive adhesive sheet prepared in Comparative Example 2. In Table 1, as the measured values of the adhesive force, the average values of three cases are shown except when dipping was performed. When dipping was performed, the lower limit value and the upper limit value of the measured adhesive force were described and denoted as "zip". In Table 1, the attachment of "AT" to the measured value of the adhesive force means that the entire adhesive layer was transferred to the adherend side (complete transfer).

[0047]

Table 1

[0048] Also, in the pressure-sensitive adhesive sheet prepared in Example 1, the adhesive force with respect to the PP plate at 100°C exceeded 5.0 N / 25 mm, maintaining a relatively high adhesive force. In contrast, in the pressure-sensitive adhesive sheet prepared in Comparative Example 1, the adhesive force with respect to the PP plate at 100°C was very small. In the pressure-sensitive adhesive sheet prepared in Comparative Example 2, the adhesive force with respect to the PP plate at 100°C was also less than 5.0 N / 25 mm.

[0049] In the adhesive sheet produced in Example 1, it was confirmed that the breaking stress was greater under both the conditions of 23°C and 100°C compared to the adhesive sheet produced in Comparative Example 1 and the adhesive sheet prepared in Comparative Example 2.

[0050] Regarding the storage elastic modulus, the adhesive sheet produced in Example 1 showed higher values under both the conditions of 23°C and 100°C compared to the adhesive sheet produced in Comparative Example 1 and the adhesive sheet prepared in Comparative Example 2.

[0051] Figure 4 is a photographic view showing the results of performing TOM molding using a decorative adhesive sheet provided with the adhesive sheet produced in Example 1 and the adhesive sheet prepared in Comparative Example 2, respectively.

[0052] As shown in the figure, when using the decorative adhesive sheet provided with the adhesive sheet produced in Example 1, it was confirmed that the decorative adhesive sheet followed the unevenness of the adherend well and no lifting or peeling occurred. On the other hand, when using the decorative adhesive sheet provided with the adhesive sheet prepared in Comparative Example 2, slight lifting of the decorative adhesive sheet was observed at the ends of the front and rear parts. Thus, it was confirmed that by using the adhesive sheet of the present embodiment, it is possible to perform molding on a PP adherend without causing lifting.

Industrial Applicability

[0053] The adhesive sheet of the present disclosure can be used for decoration of automotive parts, household appliances, daily necessities, vehicles such as railways, and building materials.

Explanation of Signs

[0054] 1 First release liner 3 Adhesive layer 5 Second release liner 7 Resin sheet 9 Surface layer 10 Decorative adhesive sheet 12 Adhesive sheet 15 Decorative sheet 20 Adherend 30 Vacuum pressure forming device

Claims

1. An adhesive sheet used for attaching a decorative sheet to an adherend, comprising an adhesive layer, wherein the adhesive strength under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 23°C and a relative humidity of 50% 24 hours after attachment to a polypropylene plate is 10 N / 25 mm or more, and the adhesive strength under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 100°C 48 hours after attachment to a polypropylene plate is 5.0 N / 25 mm or more.

2. The storage elastic modulus of the adhesive layer at 23°C is greater than 1.0×10 ５ Pa and less than or equal to 1.0×10 ８ Pa. The adhesive sheet according to claim 1.

3. The storage elastic modulus of the adhesive layer at 23°C is greater than 1.0×10 ６ Pa and not greater than 1.0×10 ７ Pa. The pressure-sensitive adhesive sheet according to claim 2.

4. The elongation at break of the adhesive layer at 23°C is 400% or more, and the elongation at break of the adhesive layer at 100°C is greater than the elongation at break of the adhesive layer at 23°C. The adhesive sheet according to Claim 1.

5. The adhesive layer has an acrylic copolymer containing units derived from butyl acrylate, and the content of the units derived from butyl acrylate is 30% by mass or more based on the total mass of the acrylic copolymer. The adhesive sheet according to any one of Claims 1 to 4.

6. A decorative adhesive sheet comprising a decorative sheet having a resin sheet and an adhesive layer attached to one surface of the resin sheet, wherein the adhesive strength of the adhesive layer under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 23°C and a relative humidity of 50% 24 hours after attachment to a polypropylene plate is 10 N / 25 mm or more, and the adhesive strength of the adhesive layer under the conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 100°C 48 hours after attachment to a polypropylene plate is 5.0 N / 25 mm or more.

7. The resin sheet contains polypropylene as a main material. The decorative adhesive sheet according to Claim 6.

8. The adhesive layer has an acrylic copolymer containing units derived from butyl acrylate, and the content of the units derived from butyl acrylate is 30% by mass or more based on the total mass of the acrylic copolymer. The decorative adhesive sheet according to Claim 6 or 7.

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