JP7549591B2 - Adhesive sheet and method for producing the adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet and a method for producing the adhesive sheet.

Conventionally, there are high-gloss adhesive sheets that are applied to the surfaces of automobiles, home appliances, furniture, etc. to add decoration. For example, Patent Document 1 discloses an adhesive sheet in which a high-gloss substrate layer, an adhesive layer, and a release liner are laminated. Such an adhesive sheet is applied to an adherend via the adhesive layer after the release liner is peeled off.

In this case, air can get in between the adhesive sheet and the adherend, causing what is known as "blistering." However, if continuous convex portions are provided on the surface of the release liner, which then form corresponding concave portions in the adhesive layer, the air can be expelled through the concave portions, thereby preventing blistering.

JP 2007-269928 A

However, when protrusions are provided on the paper release liner, although swelling is suppressed, depending on the texture of the paper that forms the release liner, marks may remain on the base layer of the adhesive sheet, which is undesirable, particularly in high-gloss adhesive sheets, as such marks are easily noticeable.

Therefore, the present invention aims to provide a release liner, an adhesive sheet, and a method for producing an adhesive sheet that are less likely to leave texture marks.

The release liner of the present invention for achieving the above object comprises a polyolefin layer having continuous convex portions on its surface, and a cast-coated paper on which the polyolefin layer is laminated. The paper base material on which the cast-coated layer forming the surface layer of the cast-coated paper is laminated is made of wood pulp, and the ratio of N-material to L-material, N-material/L-material, is 0 or more and 2/3 or less by mass.

To achieve the above object, the adhesive sheet of the present invention has a base layer having a specular gloss Gs (60°) of 60% or more in accordance with JIS Z8741-1997 (ISO 2813:1994), an adhesive layer, and the release liner, in this order in the lamination direction.

To achieve the above object, the method for producing the adhesive sheet of the present invention comprises forming an adhesive layer on at least one of a base layer having a specular gloss Gs (60°) of 60% or more in accordance with JIS Z8741-1997 and the release liner, and bonding the base layer and the release liner together via the adhesive layer.

In the invention having the above configuration, the cast-coated paper used for the release liner has an excellent smoothness of the cast-coated surface layer, and furthermore, the paper base material itself formed from wood pulp contains a large amount of L material, which makes it difficult for texture to occur. As a result, texture of the release liner is effectively suppressed, and texture marks are unlikely to remain on the PSA sheet.

1 is a perspective view showing a pressure-sensitive adhesive sheet according to an embodiment. FIG. 2 is a perspective view showing the pressure-sensitive adhesive sheet of the embodiment with the release liner removed. FIG. 2 is a side view showing the release liner of the embodiment. FIG. 2 is a side view showing bonding of a base layer and a release liner via a pressure-sensitive adhesive layer.

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and differ from the actual ratios.

As shown in Figure 1, the adhesive sheet 10 of the embodiment has a base layer 11, an adhesive layer 12, and a release liner 100, in this order in the stacking direction. The adhesive sheet 10 is a high-gloss decorative sheet that decorates the surface of an adherend such as an automobile, home appliance, or furniture, and can be used, for example, as a substitute for paint.

As shown in Figure 2, the adhesive sheet 10 is used by peeling off the release liner 100, and is attached to an adherend via the adhesive layer 12. A release agent layer may be formed on the surface of the release liner 100 that comes into contact with the adhesive layer 12 using a release agent. The release liner 100 has protruding portions 111, and corresponding recessed portions 13 are formed in the adhesive layer 12.

The protrusions 111 are continuous and extend linearly, but are not limited thereto and may be curved. The number of protrusions 111 is also not particularly limited. In the illustrated example, the multiple protrusions 111 extend parallel to each other, but are not limited thereto, and the scope of the present invention also includes a configuration in which the multiple protrusions 111 intersect with each other, for example, in a lattice pattern.

In addition, the protrusions 111 have a triangular cross-sectional shape in a cross section in the thickness direction of the release liner 100, but are not limited to this. In the same cross section, the protrusions 111 may have other cross-sectional shapes, such as a rectangular shape (square, rectangle), a trapezoidal shape, or a semi-elliptical shape. The recesses 13 have a shape that is the inverse of the shape of the protrusions 111.

The adhesive sheet 10 has groove-shaped recesses 13 formed in the adhesive layer 12, so that even if air gets between the sheet and the adherend when the sheet is applied to the adherend, the air can be expelled through the recesses 13, preventing swelling.

The adhesive sheet 10 decorates the adherend with the color and gloss imparted to the base layer 11. The base layer 11 may also have a pattern. The surface of the base layer 11 opposite the adhesive layer 12 has a specular gloss Gs (60°) of 60% or more according to JIS Z8741-1997. The upper limit of the specular gloss Gs (60°) is not particularly limited, but is, for example, 120%. The specular gloss Gs (60°) can be measured, for example, by a gloss meter "VG7000" manufactured by Nippon Denshoku Industries Co., Ltd.

The substrate layer 11 preferably contains a colorant and a resin. The thickness of the substrate layer 11 is not particularly limited, but is, for example, 50 μm or more and 200 μm or less.

Examples of resins that form the base layer 11 include polyurethane, polyolefin, polyvinyl chloride, ethylene-vinyl acetate copolymer, etc.

Examples of colorants contained in the base layer 11 include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine soot, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, composite oxide-based black pigments, and anthraquinone-based organic black pigments.

The base layer 11 may have a clear layer with adjustable gloss on the surface opposite the adhesive layer 12. Examples of resins that can be used to form the clear layer include fluororesins, polyurethanes, acrylic polymers, polyvinyl chloride, polyolefins such as polyethylene and polypropylene, thermoplastic elastomers such as olefins and polyesters, and ionomers.

In addition, the base layer 11 may contain, as necessary, appropriate stabilizers (e.g., Ba-Zn based, etc.), lubricants, fillers, processing aids, plasticizers, softeners, metal powders, anti-fogging agents, UV shielding agents such as UV scattering agents or UV absorbing agents, antioxidants, antistatic agents, twist retardants, etc.

The adhesive layer 12 is not particularly limited as long as it can exert the desired adhesive strength on the adherend. Examples of adhesives that form the adhesive layer 12 include, but are not limited to, acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, styrene-diene block copolymer adhesives, vinyl alkyl ether adhesives, polyamide adhesives, and fluorine-based adhesives. These adhesives may be used alone or in combination of two or more. The thickness of the adhesive layer 12 is, for example, 10 μm or more and 100 μm or less, but is not limited to this.

As shown in FIG. 3, the release liner 100 has a configuration in which a polyolefin layer 110 and a polyolefin layer 120 are laminated to both sides of the thickness direction of a cast coated paper 130.

In addition, the surface of the release liner 100 on the polyolefin layer 110 side may have a release agent layer formed thereon using a release agent such as, for example, a rubber-based elastomer such as silicone, olefin resin, isoprene resin, or butadiene resin, a long-chain alkyl resin, a long-chain alkyl acrylate resin, an alkyd resin, or a fluorine-based resin, but is not limited thereto. If the polyolefin layer 110 is formed using a copolymer of a release agent and a polyolefin resin as exemplified here, the polyolefin layer 110 itself can exhibit good releasability even without a release agent layer.

The polyolefin layers 110 and 120 are layers in which polyolefin resin is the main component of the resin contained therein. Here, the main component refers to a resin that is contained in an amount of 60% by mass or more (upper limit 100% by mass) relative to the resin, preferably 75% by mass or more (upper limit 100% by mass), more preferably 85% by mass or more (upper limit 100% by mass), and most preferably 95% by mass or more (upper limit 100% by mass).

Examples of polyolefin resins that form the polyolefin layers 110 and 120 include polyethylene, polypropylene, and polymethylpentene. Since the polyolefin layer 110 has the convex portion 111, it is preferable that the polyolefin layer 110 is formed of polyethylene from the viewpoint of processability. The thickness (maximum thickness) of the polyolefin layers 110 and 120 is not particularly limited, but is, for example, 5 μm or more and 50 μm or less.

The cast-coated paper 130 has a configuration in which a paper base material 131, a clay coat layer 132 (filler layer), and a cast coat layer 133 are laminated in this order.

The paper base material 131 is formed from wood pulp. There are two types of wood pulp: N-wood and L-wood. N-wood is wood pulp made from coniferous trees and has thick, long fibers. On the other hand, L-wood is wood pulp made from broadleaf trees and has thin, short fibers. The paper base material 131 contains N-wood and L-wood in such a way that the latter is more abundant than the former, or it is made of L-wood with no N-wood.

Specifically, the ratio N material/L material of the N material and L material in the paper base material 131 is 0 or more and 2/3 or less in mass ratio. Here, when N material/L material is 0, the paper base material 131 is composed of L material without containing N material. The thickness of the paper base material 131 is not particularly limited, but is, for example, 80 μm or more and 150 μm or less.

The clay coat layer 132 includes clay and a binder resin. The clay coat layer 132 may also include other additives in addition to the clay and the binder resin.

Examples of clays contained in the clay coat layer 132 include, but are not limited to, kaolin, talc, bentonite, smectite, vermiculite, mica, chlorite, wood-bush clay, gairome clay, halloysite, etc. These clays may be used alone or in combination of two or more types.

The binder resin contained in the clay coat layer 132 is not particularly limited, but examples include emulsions of copolymers such as styrene-butadiene copolymer, ethylene-vinyl chloride copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl acetate copolymer, and (meth)acrylic acid ester copolymer; water-soluble resins such as casein, dextrin, starch, oxidized starch, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and polyvinyl alcohol. These binder resins may be used alone or in combination of two or more.

Additives contained in the clay coating layer 132 other than the clay and binder resin are not particularly limited, but may include, for example, pigments, pigment dispersants, defoamers, foam inhibitors, viscosity adjusters, lubricants, water-resistant agents, water retention agents, colorants, etc.

In this embodiment, the clay coat layer 132 is given as an example of a filling layer, but the filling layer of the present invention is not limited to the clay coat layer 132 and may be a resin layer formed of a binder resin such as those mentioned in the paragraph before last without including clay. In addition, such a resin layer may include an additive such as those mentioned in the paragraph before last.

The cast coat layer 133 includes a pigment and a binder resin. The cast coat layer 133 may also include other additives in addition to the pigment and the binder resin.

Examples of pigments contained in the cast coat layer 133 include, but are not limited to, kaolin, calcined kaolin, calcium carbonate, talc, aluminum hydroxide, titanium dioxide, barium sulfate, zinc oxide, satin white, aluminum silicate, magnesium silicate, synthetic amorphous silica, etc. These pigments may be used alone or in combination of two or more.

The binder resin contained in the cast coat layer 133 is not particularly limited, and for example, the resins listed above can be used as the binder resin contained in the clay coat layer 132. In addition, one type of resin may be used alone, or two or more types of resins may be used in combination.

Additives contained in the cast coat layer 133 other than the pigment and binder resin are not particularly limited, but examples include pigment dispersants, release agents, defoamers, viscosity adjusters, water-resistant agents, preservatives, etc.

Cast-coated paper 130 is produced by forming a clay coat layer 132 on a paper base material 131 and then forming a cast coat layer 133.

The clay coating layer 132 is formed by applying a coating liquid prepared by diluting clay and a binder resin with any suitable solvent to the paper substrate 131 and drying the coating liquid, and then calendering is performed after the coating liquid has dried. The method of applying the coating liquid is not particularly limited, and examples include roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, impregnation, and curtain coating.

The cast coat layer 133 is formed by applying a coating liquid prepared by diluting a pigment and a binder resin with any suitable solvent to the clay coat layer 132 by the coating method described above to form a coating film, and then drying the coating film while pressing it with a heated metal mirror drum (cast drum). Here, the coating film may be dried by the mirror drum while still in a wet state, or may be passed through a coagulating liquid to make it gelled and then dried by the mirror drum, or may be dried once and then returned to a wet state with a re-wetting liquid and then dried by the mirror drum. The cast coat layer 133 has excellent smoothness and exhibits strong gloss because it is formed while being pressed by the mirror drum (cast drum).

After preparing the cast-coated paper 130, the polyolefin layers 110 and 120 are formed. The polyolefin layer 110 is formed on the surface of the cast-coated paper 130 that faces the cast-coated layer 133, and the polyolefin layer 120 is formed on the opposite surface. After the polyolefin layer 120 is formed, the polyolefin layer 110 is formed, but this order of formation is not limited to this. The polyolefin layers 110 and 120 are formed, for example, by a melt extrusion method.

The protrusions 111 are formed, for example, by embossing a layer of polyolefin resin formed by melt extrusion, preferably before the polyolefin resin solidifies. In the embossing process, an embossing roll with recesses formed on its outer peripheral surface is pressed against the layer of polyolefin resin, and the recesses on the outer peripheral surface of the embossing roll are inverted and transferred to the polyolefin resin, forming the protrusions 111.

As shown in FIG. 4, after the release liner 100 is produced, an adhesive layer 12 is formed on the surface where the convex portions 111 are provided, and the base layer 11 and the release liner 100 are bonded together via the adhesive layer 12 to produce the adhesive sheet 10. The adhesive layer 12 is formed, for example, by applying an adhesive composition to the surface where the convex portions 111 of the release liner 100 are provided, and then drying the applied composition. There are no particular limitations on how the adhesive composition is applied, and the adhesive composition can be applied using a known application device such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, or gravure coater.

Next, the effects of this embodiment will be described.

In this embodiment, cast-coated paper 130 is used for the release liner 100. In the cast-coated paper 130, the cast-coated layer 133 on the surface is formed while being pressed by a mirror-finished drum (cast drum). Therefore, compared to a general coating layer, the cast-coated layer 133 has particularly excellent smoothness.

In addition, in the cast coated paper 130 of this embodiment, the paper base material 131 formed from wood pulp contains a large amount of L material, which makes the paper base material 131 itself less likely to develop texture.

In addition to L-wood, there is also N-wood as a type of wood pulp. In N-wood, the fibers are relatively aligned in the same direction, and when the moisture content increases or decreases as the coating liquid is applied and dried during the coating layer formation process, dense and sparse fiber areas are likely to form. This uneven fiber density can easily cause undulations, which are a factor in the texture.

In addition to the relatively large-scale "waviness," the more microscopic thickness and length of each fiber can also be factors that cause texture, but N wood is more likely to cause texture because its fibers are thick and long.

On the other hand, the L material, which is contained in large amounts in the paper base material 131 of this embodiment, has fibers that are randomly oriented and have little bias in fiber density, making it less likely to cause "waviness" and each fiber is also thin and short. Therefore, the paper base material 131 itself is less likely to form a texture.

As described above, in this embodiment, the texture of the release liner 100 is effectively suppressed by the characteristics of the cast coat layer 133, which has excellent smoothness, and the paper base material 131 itself, which contains a large amount of L material. Therefore, even when the release liner 100 and the base material layer 11 are bonded together, the texture of the release liner 100 is unlikely to be transferred to the base material layer 11, and texture marks are unlikely to remain on the adhesive sheet 10.

The release liner 100 has a clay coat layer 132 (a sealing layer) between the paper substrate 131 and the cast coat layer 133, which prevents the coating liquid applied when the cast coat layer 133 is formed from seeping into the paper substrate 131.

As the coating liquid soaks into the paper substrate 131, there is a risk that the texture of the paper substrate 131 will become visible on the surface of the coating film and, ultimately, the cast coat layer 133. However, in this embodiment, the clay coat layer 132 (filler layer) seals the gaps between the fibers on the surface of the paper substrate 131, preventing the coating liquid from soaking in, thereby further improving the smoothness of the cast coat layer 133.

In this embodiment, a polyolefin layer 120 is laminated on the opposite side of the cast-coated paper 130 from the polyolefin layer 110, making the release liner 100 less likely to curl.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, the present invention also includes an embodiment in which the polyolefin layer 120 is omitted from the above embodiment.

In addition, in the above embodiment, as shown in FIG. 4, the base layer 11 and the release liner 100 are bonded to each other by forming an adhesive layer 12 on the release liner 100 side, but the present invention also includes a form in which an adhesive layer 12 is formed on the base layer 11 side and the base layer 11 and the release liner 100 are bonded to each other.

In addition, as in the above embodiment, it is preferable that the cast-coated paper has a filler layer between the cast-coat layer and the paper base material, but the present invention is not limited to this. The scope of the present invention also includes a form in which there is no filler layer between the cast-coat layer and the paper base material, and the cast-coat layer is laminated directly on the paper base material.

The shape of the adhesive sheet is not particularly limited and may be, for example, a rectangular shape such as a square or a rectangle, a long shape, or a shape that corresponds to the shape of the adherend.

10 Adhesive sheet,
11 Base material layer,
12 adhesive layer,
13 recessed portion,
100 release liner,
110 polyolefin layer,
111 convex portion,
120 polyolefin layer,
130 cast coated paper,
131 Paper substrate,
132 clay coat layer (filling layer),
133 Cast coat layer.

Claims (5)

An adhesive sheet that is a decorative sheet,
A substrate layer having a specular gloss Gs (60°) of 60% or more in accordance with JIS Z8741-1997;
An adhesive layer;
a release liner, in this order in the stacking direction;
The release liner is
a polyolefin layer having continuous protrusions on a surface thereof;
and a cast-coated paper having the polyolefin layer laminated thereon;
The paper base material on which the cast coat layer forming the surface layer of the cast coated paper is laminated is formed from wood pulp, and the ratio of N material to L material, N material/L material, is a mass ratio of 0 or more and 2/3 or less. The pressure-sensitive adhesive sheet according to claim 1 , wherein the cast-coated paper has a sealing layer between the cast-coated layer and the paper base material. The pressure-sensitive adhesive sheet according to claim 1 or 2, further comprising a polyolefin layer on the opposite side of the cast-coated paper to the polyolefin layer on which the convex portions are provided. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the cast coat layer does not contain kaolin. A method for producing a decorative sheet, which is an adhesive sheet, comprising the steps of:
A substrate layer having a specular gloss Gs (60 °) of 60% or more in accordance with JIS Z8741-1997; and
a polyolefin layer having continuous protrusions on a surface thereof;
and a cast-coated paper having the polyolefin layer laminated thereon;
The cast-coated paper has a paper base material on which a cast-coated layer forming a surface layer is laminated, the paper base material being made of wood pulp, and a pressure-sensitive adhesive layer is formed on at least one of the release liners, the ratio of N material to L material being 0 or more and 2/3 or less by mass ,
a method for producing a pressure-sensitive adhesive sheet, comprising bonding the base layer and the release liner together via the pressure-sensitive adhesive layer.