JP7063667B2 - Decorative sheet - Google Patents

Description

The present disclosure relates to decorative sheets used for interior and exterior applications.

In vehicles, buildings, traffic signs, packaging materials, signboards, etc., marking films, decorative films, or decorative sheets in which a pressure-sensitive adhesive layer is provided on a base material such as film, synthetic leather, or paper are used.

Patent Document 1 (Japanese Unexamined Patent Publication No. 5-271628) states that "a base material having a fine powder silica having a silanol group on the surface of particles having an average particle size of 40 nm or less and a pH of 6 or less of primary particles produced by a dry method". A removable pressure-sensitive adhesive sheet provided with an acrylic pressure-sensitive adhesive layer on the top is described.

Japanese Unexamined Patent Publication No. 5-271628

Since the decorative sheet may be used in the form of a large area, it is desirable that the decorative sheet has excellent reworkability (reworkability) so that it can be repeatedly peeled off in the positioning work at the time of construction. In addition, when the decorative sheet contracts or expands excessively in response to temperature changes throughout the year, the decorative sheet floats from the surface of the adherend, cracks occur in the decorative sheet surface, and the design is affected by deformation of the decorative sheet. There is a risk of deterioration, which is especially noticeable in large-area decorative sheets. Therefore, it is desirable that the decorative sheet has high dimensional stability.

The present disclosure provides a decorative sheet having excellent reworkability and dimensional stability.

According to one embodiment of the present disclosure, it is a decorative sheet including a base layer and an adhesive layer arranged on or above the base layer, and the adhesive layer has a weight average molecular weight of 400,000 or less (meth). ) A cured product of a pressure-sensitive adhesive composition containing an acrylic polymer and hydrophobic nanosilica particles, and 0.1 to 25 parts by mass of the hydrophobic nanosilica particles based on 100 parts by mass of the (meth) acrylic polymer. , Decorative sheets are provided.

According to the present disclosure, the use of a combination of a (meth) acrylic polymer having a weight average molecular weight of 400,000 or less and hydrophobic nanosilica particles in the adhesive layer imparts excellent reworkability and dimensional stability to the decorative sheet. be able to.

The above description shall not be deemed to disclose all embodiments of the invention and all advantages relating to the invention.

It is a schematic sectional drawing of the decorative sheet of one Embodiment.

Hereinafter, the present invention will be described in more detail for the purpose of illustrating typical embodiments of the present invention, but the present invention is not limited to these embodiments.

In the present disclosure, "decorative sheet" means a sheet used for decorative purposes, which may be colorless or colored, transparent, translucent or opaque, with or without a design. good.

In the present disclosure, "(meth) acrylic" means acrylic or methacrylic, and "(meth) acrylate" means acrylate or methacrylate.

In the present disclosure, "pressure-sensitive adhesion" is permanently adhesive in the operating temperature range, for example, 0 ° C. or higher and 50 ° C. or lower, adheres to various surfaces with a light pressure, and undergoes a phase change (from liquid). Means the properties of a material or composition that does not exhibit (to a solid).

In the present disclosure, "transparent" means that the total light transmittance of a certain material or article in the wavelength range of 400 to 700 nm is about 85% or more, and "semi-transparent" means the wavelength range of a certain material or article. It means that the total light transmittance at 400 to 700 nm is about 20% or more and less than about 85%, and "opaque" means that the total light transmittance of a certain material or article in the wavelength range of 400 to 700 nm is about 20%. Means less than. The total light transmittance is determined in accordance with JIS K 7631-1: 1997 (ISO 13468-1: 1996).

The decorative sheet of one embodiment includes a base layer and an adhesive layer placed on or above the base layer. The adhesive layer contains a cured product of a pressure-sensitive adhesive composition containing a (meth) acrylic polymer having a weight average molecular weight of 400,000 or less and hydrophobic nanosilica particles. The blending amount of the hydrophobic nanosilica particles based on 100 parts by mass of the (meth) acrylic polymer is 0.1 part by mass or more and 25 parts by mass or less. "Adhesive layer placed on top of the base layer" means that the adhesive layer is placed in direct contact with the base layer, and "adhesive layer placed above the base layer" means adhesion. It means that the layer is not in direct contact with the base layer but is arranged via another layer, for example a bonding layer. The same applies to the definitions of "above" and "above" referred to in this disclosure for other layers.

A schematic cross-sectional view of the decorative sheet of one embodiment is shown in FIG. The decorative sheet 10 of FIG. 1 includes a base layer 12 and an adhesive layer 14. The adhesive layer 14 contains a (meth) acrylic polymer having a weight average molecular weight of 400,000 or less and hydrophobic nanosilica particles 16.

The base layer may be formed of a transparent material, a translucent material or an opaque material. The base layer may be colorless or colored and may have patterns, letters, patterns and the like on its surface or inside.

As the base layer, for example, resins such as polyethylene, polypropylene, polyester, acrylic resin, polycarbonate, polyvinyl chloride, polyvinyl chloride, polystyrene, polyamide; fabrics such as woven fabric, non-woven fabric, knitted fabric; natural leather and artificial leather; paper. And laminated paper; wood; films, foils, sheets or boards such as metals such as iron and aluminum can be used. In one embodiment, the base layer is a resin film.

In one embodiment, the adhesive layer is placed on top of the base layer, i.e., in direct contact with the base layer. In another embodiment, the adhesive layer is placed above the base layer, i.e. another layer between the adhesive layer and the base layer, such as a primer layer, a bonded layer, a colored layer, a metal layer, a printed layer, a bulk layer. Etc. intervene. The contact surface of the base layer with the adhesive layer may be subjected to surface treatment such as corona treatment, plasma treatment, and frame treatment.

Other layers such as a colored layer, a metal layer, a printing layer, a bulk layer, a surface protection layer, and a clear layer may be arranged on or above the base layer. The base layer may be subjected to surface treatment such as matting or embossing.

The thickness of the base layer can be, for example, about 5 μm or more, about 10 μm or more, or about 20 μm or more, about 500 μm or less, about 300 μm or less, or about 200 μm or less.

In one embodiment, the adhesive layer comprises a cured product of a pressure sensitive adhesive composition comprising a (meth) acrylic polymer having a weight average molecular weight of 400,000 or less and hydrophobic nanosilica particles.

The (meth) acrylic polymer can be obtained by polymerizing or copolymerizing a monomer mixture containing a monoethylenically unsaturated monomer. The (meth) acrylic polymer may be an adhesive polymer. The adhesive polymer means a polymer having a tack at an operating temperature (for example, 5 ° C, 10 ° C, 15 ° C, 20 ° C or 25 ° C) and imparting pressure-sensitive adhesiveness to an adhesive. If necessary, one kind or two or more kinds of monoethylenically unsaturated monomers can be used.

As a monoethylenically unsaturated monomer, the formula (1):
CH ₂ = CR ¹ COOR ² (1)
A (meth) acrylic ester monomer represented by can be used. In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a linear, cyclic or branched alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 20 carbon atoms, and the like. It is an alkoxyalkyl group having 2 to 20 carbon atoms, a phenoxyalkyl group having 7 to 20 carbon atoms, a hydroxyalkyl group having 1 to 20 carbon atoms, or a cyclic ether group having 2 to 20 carbon atoms.

Examples of the (meth) acrylic ester monomer represented by the formula (1) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isoamyl (meth) acrylate, and n-hexyl (meth). Alkyl (meth) acrylates such as acrylates, 2-ethylhexyl (meth) acrylates, isooctyl (meth) acrylates, isononyl (meth) acrylates, decyl (meth) acrylates, dodecyl (meth) acrylates, cyclohexyl (meth) acrylates, and isobornyl (meth) acrylates. ) Acrylate; Aromatic (meth) acrylates such as phenyl (meth) acrylates and p-tolyl (meth) acrylates; alkoxyalkyl (meth) acrylates such as methoxypropyl (meth) acrylates and 2-methoxybutyl (meth) acrylates; phenoxy Phenoxyalkyl (meth) acrylates such as ethyl (meth) acrylates; hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylates, 2-hydroxypropyl (meth) acrylates, 4-hydroxybutyl (meth) acrylates; glycidyl Examples thereof include cyclic ether group-containing (meth) acrylates such as (meth) acrylates and tetrahydrofurfuryl (meth) acrylates.

As monoethylenic unsaturated monomers, unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; unsaturated dicarboxylic acids such as itaconic acid, fumaric acid, citraconic acid and maleic acid; ω-carboxypolycaprolactone monoacrylate, Uses carboxyl group-containing unsaturated monomers such as monohydroxyethyl phthalate (meth) acrylate, β-carboxyethyl acrylate, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid. You may. The cohesive force of the adhesive layer can be enhanced by using the unsaturated monomer containing a carboxyl group.

As other monoethylene unsaturated monomers, aromatic vinyl monomers such as styrene, α-methylstyrene and vinyltoluene, vinyl esters such as vinyl acetate, and unsaturated nitriles such as acrylonitrile and methacrylonitrile may be used. The cohesive force of the adhesive layer can be enhanced by using unsaturated nitriles.

In some embodiments, the (meth) acrylic polymer is, for example, about 80 parts by mass or more, about 85 parts by mass or more, or about 90 parts by mass or more, about 99.5 parts by mass or less of the (meth) acrylic ester monomer. About 99 parts by mass or less, or about 98 parts by mass or less, about 0.5 parts by mass or more, about 1 part by mass or more, or about 2 parts by mass or more, about 15 parts by mass or less, about other monoethylene unsaturated monomers. It can be obtained by copolymerizing a monomer mixture contained in an amount of 10 parts by mass or less or about 10 parts by mass or less.

In some embodiments, the (meth) acrylic polymer is a (meth) acrylic ester monomer having an alkyl group having 8 or more carbon atoms, that is, a linear chain in which ^R2 has 8 or more carbon atoms in the formula (1). About 50 parts by mass or more, about 55 parts by mass or more, or about 60 parts by mass or more, about 90 parts by mass or less, about 85 parts by mass or less, or about 80 parts by mass or more of the (meth) acrylic ester monomer which is a cyclic or branched alkyl group. It can be obtained by copolymerizing a monomer mixture contained in an amount of parts by mass or less. The obtained (meth) acrylic polymer contains a unit derived from a (meth) acrylic ester monomer having 8 or more carbon atoms of an alkyl group in an amount of about 50% by mass or more, about 55% by mass or more, or about 60% by mass. As mentioned above, it includes about 90% by mass or less, about 85% by mass or less, or about 80% by mass or less. The (meth) acrylic polymer of this embodiment is excellent in weather resistance, transparency, and low temperature resistance.

The weight average molecular weight of the (meth) acrylic polymer is about 400,000 or less. In some embodiments, the weight average molecular weight of the (meth) acrylic polymer is about 100,000 or more, about 150,000 or more, or about 200,000 or more, about 400,000 or less, about 380,000 or less, Or it is about 350,000 or less. The "weight average molecular weight" in the present disclosure means the molecular weight converted into standard polystyrene by the GPC method. When the weight average molecular weight is in the above range, it is excellent in low temperature resistance and can impart sufficient cohesive force and adhesiveness to the adhesive layer when combined with hydrophobic nanosilica particles.

In some embodiments, the glass transition temperature (Tg) of the (meth) acrylic polymer is about −40 ° C. or lower, about −45 ° C. or lower, or about −50 ° C. or lower, and is about −80 ° C. or higher, about. -75 ° C or higher, or about -70 ° C or higher. When Tg is in the above range, sufficient cohesive force and adhesiveness can be imparted to the adhesive layer.

より求めることができる。式中、Ｔｇ_ｉは成分ｉのホモポリマーのガラス転移温度（℃）、Ｘ_ｉは重合の際に添加した成分ｉのモノマーの質量分率をそれぞれ示し、ｉは１～ｎの自然数であり、

である。 The glass transition temperature Tg (° C.) of the (meth) acrylic polymer is the following FOX formula, assuming that each polymer is copolymerized from n kinds of monomers.

Can be obtained more. In the formula, Tg _i indicates the glass transition temperature (° C.) of the homopolymer of the component i, X _i indicates the mass fraction of the monomer of the component i added during the polymerization, and i is a natural number of 1 to n.

Is.

The polymerization or copolymerization of the (meth) acrylic polymer is preferably carried out by radical polymerization, and known polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization and bulk polymerization can be used. As initiators, organic peroxides such as benzoyl peroxide, lauroyl peroxide, and bis (4-tert-butylcyclohexyl) peroxydicarbonate, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2). -Methylbutyronitrile), dimethyl-2,2-azobis (2-methylpropionate), 4,4'-azobis (4-cyanovalerian acid), 2,2'-azobis (2-methylpropionic acid) An azo-based polymerization initiator such as dimethyl or azobis (2,4-dimethylvaleronitrile) (AVN) can be used. The amount of the initiator used is generally about 0.01 part by mass or more, or about 0.05 part by mass or more, about 5 parts by mass or less, or about 3 parts by mass or less with respect to 100 parts by mass of the monomer mixture.

Hydrophobic nanosilica particles can generally be obtained by hydrophobicizing at least a part of silanol groups (Si—OH groups) present on the surface of the nanosilica particles by surface treatment. For the surface treatment of nanosilica particles, a surface treatment agent such as silane, silazane, aluminate, titanate or a coupling agent having an alkyl group such as a methyl group, an ethyl group, an n-propyl group or an isopropyl group is used as a hydrophobic group. be able to. The hydrophobic nanosilica particles disperse in the (meth) acrylic polymer and contribute to controlling the wettability of the (meth) acrylic polymer and / or enhancing the cohesive force of the adhesive layer, resulting in excellent results. It is possible to impart reworkability and dimensional stability to the adhesive layer.

Since the particle size of the hydrophobic nanosilica particles is smaller than the wavelengths of visible light and some ultraviolet rays, the hydrophobic nanosilica particles have almost no effect on the light transmission of the adhesive layer. In one embodiment, the adhesive layer has a high total light transmittance, eg, about 85% or more, about 90% or more, or about 95% or more total light transmittance in the wavelength range of 400 to 700 nm. In this embodiment, a transparent decorative sheet can be obtained by using a colorless transparent or colored transparent base layer.

In some embodiments, the average primary particle size of the hydrophobic nanosilica particles is about 1 nm or more, about 2 nm or more, or about 5 nm or more, about 100 nm or less, about 50 nm or less, or about 30 nm or less. By setting the average primary particle size of the hydrophobic nanosilica particles in the above range, the hydrophobic nanosilica particles can be more uniformly dispersed in the adhesive layer, and the reworkability and dimensional stability of the decorative sheet can be improved. The average primary particle size of the hydrophobic nanosilica particles is the volume cumulative particle size _D50 obtained using laser diffraction / scattering particle size distribution measurement.

The blending amount of the hydrophobic nanosilica particles is about 0.1 part by mass or more and about 25 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic polymer. The blending amount of the hydrophobic nanosilica particles is within the above range, considering the average primary particle size of the hydrophobic nanosilica particles, the type of surface treatment, etc., and the hydrophobic nanosilica particles without gelling the pressure-sensitive adhesive composition. Can be appropriately selected so as to be uniformly dispersed in the pressure sensitive adhesive composition. In some embodiments, the blending amount of the hydrophobic nanosilica particles is about 1 part by mass or more, about 3 parts by mass or more, or about 5 parts by mass or more, about 15 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer. Parts or less, or about 12 parts by mass or less, or about 10 parts by mass or less.

The pressure sensitive adhesive composition is a low molecular weight dispersant including known dispersants that aid in the dispersion of hydrophobic nanosilica particles in the pressure sensitive adhesive composition, such as anionic compounds, cationic compounds and nonionic compounds. , Or may contain a polymer dispersant having anionic, cationic or nonionic polar groups.

In one embodiment, the polymer dispersant comprises an amino group-containing (meth) acrylic polymer. The amino group-containing (meth) acrylic polymer not only enhances the dispersibility of the hydrophobic nanosilica particles, but also has excellent compatibility with the (meth) acrylic polymer having an acidic group such as a carboxyl group. The weight average molecular weight of the amino group-containing (meth) acrylic polymer is not particularly limited, but is, for example, about 1,000 or more, about 5,000 or more, about 10,000 or more, about 500,000 or less, and about 200,000 or less. , Or about 100,000 or less.

In some embodiments, the amino group-containing (meth) acrylic polymer has a glass transition temperature (Tg) of about 0 ° C. or higher, about 20 ° C. or higher, or about 40 ° C. or higher, about 150 ° C. or lower, about 135 ° C. or lower, Or it is about 120 ° C. or lower. The glass transition temperature of the amino group-containing (meth) acrylic polymer can be determined by using the FOX formula as in the case of the (meth) acrylic polymer.

The amount of the dispersant to be blended is about 1 part by mass or more, about 5 parts by mass or more, or about 10 parts by mass or more, about 100 parts by mass or less, about 50 parts by mass or less, or about 50 parts by mass or more with respect to 100 parts by mass of the hydrophobic nanosilica particles. It can be 30 parts by mass or less.

The pressure-sensitive adhesive composition may contain a cross-linking agent. As the cross-linking agent, a thermal cross-linking agent or an ultraviolet cross-linking agent can be used. By cross-linking the (meth) acrylic polymer with a cross-linking agent, the cohesive force of the adhesive layer can be enhanced, and the reworkability and dimensional stability of the decorative sheet can be enhanced.

As the heat-crosslinking agent, a heat-crosslinking agent selected from the group consisting of an epoxy cross-linking agent and a bisamide cross-linking agent can be used. When the (meth) acrylic polymer has a polar group such as a carboxyl group or a hydroxyl group, these thermal cross-linking agents form covalent cross-linking between these polymer chains, and the cohesive force of the adhesive layer is more effective. Can be enhanced. As an epoxy cross-linking agent, for example, N, N, N', N'-tetraglycidyl-1,3-benzenedi (methaneamine) (Mitsubishi Gas Chemical Co., Ltd .: TETRAD-X, Soken Kagaku Co., Ltd .: E-AX, E- 5XM), N, N'-(cyclohexane-1,3-diylbismethylene) bis (diglycidylamine) (Mitsubishi Gas Chemical Company: TETRAD-C, Soken Chemical Co., Ltd .: E-5C) and the like. .. Examples of the bisamide cross-linking agent include 1,1'-(1,3-phenylenedicarbonyl) -bis (2-methylaziridine) (1,1'-isophthaloyl-bis (2-methylaziridine)), 1,4-. Examples thereof include bis (ethyleneiminocarbonylamino) benzene, 4,4'-bis (ethyleneiminocarbonylamino) diphenylmethane, and 1,8-bis (ethyleneiminocarbonylamino) octane.

In one embodiment, the thermal crosslinker does not have an isocyanate group. In the present disclosure, an isocyanate cross-linking agent having an isocyanate group can be used as the heat-cross-linking agent, but the curing rate of the pressure-sensitive adhesive composition may not satisfy the manufacturing requirements.

The blending amount of the thermal cross-linking agent is about 0.01 part by mass or more, about 0.02 part by mass or more, about 0.05 part by mass or more, and about 0.5 mass with respect to 100 parts by mass of the (meth) acrylic polymer. It can be less than or equal to, about 0.4 parts by mass or less, and about 0.3 parts by mass or less.

Since the particle size of the hydrophobic nanosilica particles is smaller than the wavelength of some ultraviolet rays and does not affect the transmission of ultraviolet rays of the wavelength, the pressure-sensitive adhesive composition is impregnated with an ultraviolet cross-linking agent to form an ultraviolet curable composition. can do. As the ultraviolet cross-linking agent, a compound having a structure capable of extracting hydrogen radicals by a site that can be activated by ultraviolet irradiation to form a cross-link between (meth) acrylic polymer chains, for example, by ultraviolet irradiation is used. can do. This structure is excited by UV irradiation to extract hydrogen radicals from the (meth) acrylic polymer. As a result, radicals are generated on the (meth) acrylic polymer, and the formation of bridges by the bonds between the generated radicals, the generation of peroxide radicals by the reaction with oxygen molecules, and the formation of bridges via the generated peroxide radicals. Various reactions occur in the system, such as withdrawal of another hydrogen radical by the generated radical, and finally the (meth) acrylic polymer is crosslinked. Examples of such a compound include compounds having a hydrogen radical abstraction structure such as a benzophenone structure, a benzyl structure, an o-benzoyl benzoic acid ester structure, a thioxanthone structure, a 3-ketocoumarin structure, a 2-ethylanthraquinone structure, and a camphorquinone structure. Be done. It is advantageous to use a compound having a benzophenone structure in terms of transparency and reactivity.

The ultraviolet cross-linking agent has a hydrogen radical abstraction structure selected from the group consisting of a benzophenone structure, a benzyl structure, an o-benzoyl benzoic acid ester structure, a thioxanthone structure, a 3-ketocoumarin structure, a 2-ethylanthraquinone structure, and a camphorquinone structure. It may be a (meth) acrylic polymer. By using a (meth) acrylic polymer having a hydrogen radical extraction structure, the cross-linking reactivity can be enhanced while adjusting the viscosity of the pressure-sensitive adhesive composition. In one embodiment, the UV cross-linking agent is a benzophenone-modified (meth) acrylic polymer.

A (meth) acrylic polymer having a hydrogen radical abstraction structure may further have an amino group. The (meth) acrylic polymer having a hydrogen radical abstraction structure and an amino group can function as an ultraviolet cross-linking agent and a dispersant.

In some embodiments, in the (meth) acrylic polymer having a hydrogen radical abstraction structure, the polymerization unit having a hydrogen radical abstraction structure is about 0.1 mass by mass based on the total polymerization units of the (meth) acrylic polymer. % Or more, about 0.5% by mass or more, or about 1% by mass or more, about 10% by mass or less, about 8% by mass or less, or about 6% by mass or less.

The blending amount of the ultraviolet cross-linking agent is about 0.1 part by mass or more, about 0.5 part by mass or more, about 1 part by mass or more, about 20 parts by mass or less, and about about 100 parts by mass of the (meth) acrylic polymer. It can be 10 parts by mass or less and about 5 parts by mass or less.

The (meth) acrylic polymer may have a hydrogen radical abstraction structure in the molecule and itself may function as an ultraviolet cross-linking agent.

The pressure-sensitive adhesive composition may contain fillers, pigments, dyes, antioxidants, heat stabilizers, UV stabilizers, tackifiers and the like other than the hydrophobic nanosilica particles as other components.

The pressure-sensitive adhesive composition may be solvent-based or solvent-free. In one embodiment, the pressure sensitive adhesive composition is solvent based. Examples of the solvent contained in the pressure-sensitive adhesive composition include methanol, ethanol, hexane, toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate and the like, or a mixed solvent thereof. As the solvent, a solvent containing an aprotonic polar solvent such as a ketone such as acetone, methyl ethyl ketone and methyl isobutyl ketone and an ester such as ethyl acetate and butyl acetate can be advantageously used.

The solid content of the pressure-sensitive adhesive composition shall be about 10% by mass or more, about 20% by mass or more, about 30% by mass or more, about 95% by mass or less, about 90% by mass or less, or about 80% by mass or less. be able to. The solid content includes (meth) acrylic polymers, hydrophobic nanosilica particles, and optionally added dispersants, crosslinkers, and other non-volatile components. In some embodiments, the solid content of the pressure sensitive adhesive composition is about 50% by weight or more, about 60% by weight or more, or about 70% by weight or more, about 95% by weight or less, about 90% by weight or less. Alternatively, it is about 80% by mass or less, and has excellent coatability even with such a high solid content.

The pressure-sensitive adhesive composition may contain a premix agent in which hydrophobic nanosilica particles and a dispersant are mixed. By including the hydrophobic nanosilica particles in the pressure sensitive adhesive composition in the form of a premix, i.e., pre-dispersed in the dispersant, more hydrophobic nanosilica particles can be incorporated into the pressure sensitive adhesive composition. It can be dispersed stably.

The premix agent can be obtained by mixing the hydrophobic nanosilica particles and the dispersant by a known method. For mixing, for example, a paint shaker (manufactured by Shinky Co., Ltd.), a sand grind mill, a ball mill, an attritor mill, a three-roll mill and the like can be used. If necessary, an organic solvent may be used at the time of mixing.

The amount of the dispersant contained in the premix agent may be 100% by mass of the dispersant contained in the pressure-sensitive adhesive composition. The dispersant may be added to the pressure sensitive adhesive composition separately from the premix agent.

In the premix agent, the blending amount of the dispersant is about 1 part by mass or more, about 5 parts by mass or more, or about 10 parts by mass or more, about 100 parts by mass or less, about 50 parts by mass with respect to 100 parts by mass of the hydrophobic nanosilica particles. It can be less than a part, or less than about 30 parts by mass.

The pressure-sensitive adhesive composition can be obtained by mixing (meth) acrylic polymer and hydrophobic nanosilica particles, and if necessary, a dispersant, a cross-linking agent, and other components by using a known method. ..

For example, each component may be placed in a mixing container substantially simultaneously or sequentially and mixed using a paint shaker (manufactured by Shinky Co., Ltd.), a sand grind mill, a ball mill, an attritor mill, a three-roll mill, or the like. If necessary, an aqueous solvent or an organic solvent may be used at the time of mixing. Hydrophobic nanosilica particles can also be dispersed in an organic solvent and then mixed with other components.

As described above, after preparing a premix agent by mixing all or part of the hydrophobic nanosilica particles with all or part of the dispersant, the obtained premix agent and the remaining components are mixed by a known method. The pressure-sensitive adhesive composition can also be prepared.

An adhesive layer can be formed by curing the pressure sensitive adhesive composition on a base layer or liner. The adhesive layer formed on the liner can be transferred to the base layer and laminated on the base layer.

The thickness of the adhesive layer can be about 5 μm or more, about 10 μm or more, or about 20 μm or more, about 200 μm or less, about 100 μm or less, or about 50 μm or less.

If necessary, a liner may be arranged on both sides or one side of the adhesive layer thus formed, and the adhesive layer may be used as a double-sided adhesive sheet or tape.

The decorative sheet may have a liner on the surface of the adhesive layer opposite the base layer. Examples of the liner as an arbitrary component include plastic materials such as polyethylene, polypropylene, polyester, and cellulose acetate, paper, and laminated paper made of these plastic materials. The liner may have a surface that has been peeled off with silicone or the like.

The thickness of the liner can be, for example, about 10 μm or more, or about 25 μm or more, about 500 μm or less, or about 200 μm or less.

The adhesive layer may be solid, porous or foam. A support such as a non-woven fabric may be embedded inside the adhesive layer. The adhesive surface of the adhesive layer may be flat or may have irregularities.

On the uneven adhesive surface, a convex portion containing a cured product of the pressure-sensitive adhesive composition and a concave portion surrounding the convex portion are formed on the adhesive surface of the adhesive layer, and are adhered to the adherend. Includes an adhesive surface on which a communication path communicating with the outside is formed, which is defined by a recess between the surface of the adherend and the adhesive surface.

An example of a method for forming an uneven adhesive surface will be described below. A liner having a peeling surface having a predetermined uneven structure is prepared. A pressure-sensitive adhesive composition is applied to the peeled surface of this liner and, if necessary, heat-cured to form an adhesive layer. As a result, the uneven structure (negative structure) of the liner is transferred to the surface of the adhesive layer in contact with the liner (this is the adhesive surface in the decorative sheet), and the uneven adhesive surface having a predetermined structure (positive structure) on the adhesive surface. To form. As described above, the unevenness of the adhesive surface is preliminarily designed to include a groove in which a continuous passage can be formed when the convex portion adheres to the adherend.

The grooves of the adhesive layer may be formed by arranging grooves of a certain shape on the adhesive surface along a regular pattern to form a groove of a regular pattern as long as it can prevent air bubbles from remaining when the decorative sheet is applied. A fixed groove may be arranged to form an irregularly patterned groove. When a plurality of grooves are formed so as to be arranged substantially parallel to each other, the arrangement intervals of the grooves are preferably about 10 μm or more and about 2000 μm or less. The groove depth (distance from the adhesive surface to the bottom of the groove measured toward the base layer) is usually about 10 μm or more and about 100 μm or less. The shape of the groove is also not particularly limited as long as the effect of the present invention is not impaired. For example, the shape of the groove can be a substantially rectangular shape (including a trapezoid), a substantially semicircular shape, or a substantially semi-elliptical shape in the cross section of the groove in the direction perpendicular to the bonding surface.

The decorative sheet can be manufactured by a known method. For example, a pressure-sensitive adhesive composition or a solution obtained by diluting the pressure-sensitive adhesive composition with an organic solvent or the like, if necessary, is applied onto a liner with a knife coat, bar coat, etc., and dried to obtain a pressure-sensitive adhesive. It forms an adhesive layer containing a cured product of the composition. The adhesive layer may be heated using hot air, an oven, or the like during drying in order to react the cross-linking agent. A decorative sheet can be formed by laminating a base layer on the obtained adhesive layer by dry laminating or the like.

The decorative sheet may be colorless and transparent, or may be colored and transparent. Such a transparent decorative sheet can be used, for example, as an overlaminate film applied on top of other decorative sheets.

The decorative sheet of the present disclosure can be used for interior / exterior applications such as vehicles, buildings, traffic signs, packaging materials, signboards, etc., and may be suitably used particularly for applications requiring reworkability and dimensional stability. can.

The following examples exemplify specific embodiments of the present disclosure, but the present invention is not limited thereto. All parts and percentages are by mass unless otherwise stated.

In this embodiment, the following abbreviations shown in Table 1 may be used.

より求めた。式中、Ｔｇ_ｉは成分ｉのホモポリマーのガラス転移温度（℃）、Ｘ_ｉは重合の際に添加した成分ｉのモノマーの質量分率をそれぞれ示し、ｉは１～ｎの自然数であり、

である。 Production of Adhesive Polymer 1 (ADH1) 64 parts by mass of 2EHA, 30 parts by mass of BA, and 6 parts by mass of AA are dissolved in 42 parts by mass of ethyl acetate, and 2,2'-azobis (2,4-dimethylvaleronitrile) is used as a polymerization initiator. ) (Product name V-65, manufactured by Wako Pure Chemical Industries, Ltd.) After adding 0.67 parts by mass, the reaction was carried out at 75 ° C. under a nitrogen atmosphere for 24 hours, and the ethyl acetate solution (solid) of the adhesive polymer 1 (ADH1) was allowed to react. 70%) was prepared. The weight average molecular weight (Mw) of ADH1 was 280,000, and the glass transition temperature (Tg) was −57 ° C. The Tg (° C.) of ADH1 is based on the following FOX formula, assuming that each polymer is copolymerized from n kinds of monomers.

Asked more. In the formula, Tg _i indicates the glass transition temperature (° C.) of the homopolymer of the component i, X _i indicates the mass fraction of the monomer of the component i added during the polymerization, and i is a natural number of 1 to n.

Is.

Production of Adhesive Polymer 2 (ADH2) 64 parts by mass of 2EHA, 30 parts by mass of BA, and 6 parts by mass of AA are dissolved in 66.7 parts by mass of ethyl acetate, and 2,2'-azobis (2,4-dimethyl) is used as a polymerization initiator. Valeronitrile) (trade name V-65, manufactured by Wako Pure Chemical Industries, Ltd.) is added in an amount of 0.7 parts by mass and then reacted at 75 ° C. for 24 hours under a nitrogen atmosphere to obtain an ethyl acetate solution of the adhesive polymer 2 (ADH2). (Solid content 60%) was prepared. The weight average molecular weight (Mw) of ADH2 was 290,000, and the glass transition temperature (Tg) was −57 ° C.

Production of Adhesive Polymer 3 (ADH3) 2 EHA 62 parts by mass, BA31 parts by mass, AN2 parts by mass, and AA 5 parts by mass are dissolved in 66.7 parts by mass of ethyl acetate, and dimethyl 2,2'-azobis (as a polymerization initiator). 2-Methylpropionate)) (trade name V-601, manufactured by Wako Pure Chemical Industries, Ltd.) After adding 0.65 parts by mass, the mixture was reacted at 65 ° C. for 24 hours under a nitrogen atmosphere to obtain the adhesive polymer 3 (ADH2). ) Was prepared (solid content 60%). The weight average molecular weight (Mw) of ADH3 was 320,000, and the glass transition temperature (Tg) was −56 ° C.

Production of Adhesive Polymer 4 (ADH4) 2EHA 62 parts by mass, BA31 parts by mass, AN2 parts by mass, and AA 5 parts by mass are dissolved in 66.7 parts by mass of ethyl acetate, and dimethyl 2,2'-azobis (as a polymerization initiator). 2-Methylpropionate)) (trade name V-601, manufactured by Wako Pure Chemical Industries, Ltd.) After adding 0.65 parts by mass, the mixture was reacted at 65 ° C. under a nitrogen atmosphere for 24 hours to obtain an adhesive polymer 4 (ADH4). ) Was prepared (solid content 60%). The weight average molecular weight (Mw) of ADH4 was 370,000, and the glass transition temperature (Tg) was −56 ° C.

Production of Adhesive Polymer 5 (ADH5) 94 parts by mass of BA and 6 parts by mass of AA are dissolved in 150 parts by mass of ethyl acetate, and dimethyl 2,2'-azobis (2-methylpropionate) as a polymerization initiator) (commodity). Name V-601, manufactured by Wako Pure Chemical Industries, Ltd.) After adding 0.5 parts by mass, the reaction was carried out at 75 ° C. under a nitrogen atmosphere for 24 hours, and an ethyl acetate solution (solid content 40%) of the adhesive polymer 5 (ADH5) was added. ) Was prepared. The weight average molecular weight (Mw) of ADH5 was 580,000, and the glass transition temperature (Tg) was −48 ° C.

Production of Adhesive Polymer 6 (ADH6) 70 parts by mass of IOA, 22.5 parts by mass of MA, and 7.5 parts by mass of AA are dissolved in 150 parts by mass of ethyl acetate, and dimethyl 2,2'-azobis (2-) as a polymerization initiator. Methylpropionate)) (trade name V-601, manufactured by Wako Pure Chemical Industries, Ltd.) After adding 0.7 parts by mass, the reaction was carried out at 75 ° C. under a nitrogen atmosphere for 24 hours to obtain an adhesive polymer 6 (ADH6). An ethyl acetate solution (solid content 40%) was prepared. The weight average molecular weight (Mw) of ADH6 was 360,000, and the glass transition temperature (Tg) was −35 ° C.

Table 2 shows the materials used for producing the decorative sheet in this example.

Evaluation method The characteristics of the decorative sheet were evaluated according to the following method.

1. 1. Reworkability The test piece was cut into a length of 300 mm and a width of 210 mm. The test piece was attached to a melamine baking finish plate (manufactured by Paltek Corporation) with a squeegee in an environment of 23 ° C. The test piece was peeled off at high speed by hand. "Good" when the test piece can be easily peeled off without deformation, "Defective" when the test piece is not deformed but the peeling is heavy, and when the test piece is deformed at high speed and cannot be peeled off. Judged as "poor".

2. 20 ° C. Initial Adhesive Strength-Phosphated Steel Sheet Specimens were cut to a length of 150 mm and a width of 25 mm. JIS Z 0237 8.2.3. The test piece was attached to a phosphate-treated steel sheet (manufactured by Paltek Corporation) in an environment of 20 ° C. in accordance with the above. The test piece was left in a 20 ° C. environment for 5 minutes. The adhesive strength was measured at 180 degrees with a tensile tester (Tensilon (trademark) manufactured by Orientec Co., Ltd.) in an environment of 20 ° C. The gripping interval was 100 mm, and the peeling speed was 300 mm / min.

3.5 ° C. Initial Adhesive Strength-Phosphated Steel Sheet Specimens were cut to a length of 150 mm and a width of 25 mm. JIS Z 0237 8.2.3. The test piece was attached to a phosphate-treated steel sheet (manufactured by Paltek Corporation) in an environment of 5 ° C. in accordance with the above. The test piece was left in an environment of 5 ° C. for 5 minutes. The adhesive strength was measured at 180 degrees with a tensile tester (Tensilon (trademark) manufactured by Orientec Co., Ltd.) in an environment of 5 ° C. The gripping interval was 100 mm, and the peeling speed was 300 mm / min.

A 4.5 ° C normal adhesive force-phosphate treated steel sheet test piece was cut into a length of 150 mm and a width of 25 mm. JIS Z 0237 8.2.3. The test piece was attached to a phosphate-treated steel sheet (manufactured by Paltek Corporation) in an environment of 5 ° C. in accordance with the above. The test piece was left in an environment of 5 ° C. for 24 hours. The adhesive strength was measured at 180 degrees with a tensile tester (Tensilon (trademark) manufactured by Orientec Co., Ltd.) in an environment of 5 ° C. The gripping interval was 100 mm, and the peeling speed was 300 mm / min.

5. After peeling off the test piece according to the adhesive residue "20 ° C. initial adhesive strength-phosphate treated steel sheet", the surface of the phosphate-treated steel sheet was visually observed. The case where the adhesive residue did not remain on the surface of the phosphate-treated steel sheet was regarded as "good", and the case where the adhesive residue remained on the surface of the phosphate-treated steel sheet was regarded as "poor".

6. 20 ° C. Initial Adhesive Strength-Melamine Baked Paint Plate The test piece was cut to a length of 150 mm and a width of 25 mm. JIS Z 0237 8.2.3. The test piece was attached to a melamine baking finish plate (manufactured by Paltek Corporation) in an environment of 20 ° C. in accordance with the above. The test piece was left in a 20 ° C. environment for 5 minutes. The adhesive strength was measured at 180 degrees with a tensile tester (Tensilon (trademark) manufactured by Orientec Co., Ltd.) in an environment of 20 ° C. The gripping interval was 100 mm, and the peeling speed was 300 mm / min.

7. 20 ° C. Initial Adhesive Strength-Aluminum Plate The test piece was cut to a length of 150 mm and a width of 25 mm. JIS Z 0237 8.2.3. The test piece was attached to an aluminum plate (A5052P manufactured by Asahi Bee Techno Co., Ltd.) in an environment of 20 ° C. in accordance with the above. The test piece was left in a 20 ° C. environment for 5 minutes. The adhesive strength was measured at 180 degrees with a tensile tester (Tensilon (trademark) manufactured by Orientec Co., Ltd.) in an environment of 20 ° C. The gripping interval was 100 mm, and the peeling speed was 300 mm / min.

8. Heat shrinkability (dimensional stability)
The test piece was cut into a square of 50 mm square. After attaching the test piece to an aluminum plate (A5052P manufactured by Asahi Bee Techno Co., Ltd.) in an environment of 23 ° C and leaving it in an environment of 23 ° C for 24 hours, make a cross cut in the test piece and make a square of 25 mm square. Divided. The test piece was left in an environment of 65 ° C. for 24 hours. The shrinkage state of the test piece after the heat treatment was observed with an optical microscope, and the largest gap between the 25 mm square squares was taken as the heat shrinkage value (mm). When the outer circumference of the test piece contracted and no gap was observed between the 25 mm square squares, it was defined as "closed". "Closed" means that the adhesive layer could not follow the shrinkage of the base layer due to the small cohesive force of the adhesive layer of the decorative sheet, and generally, the adhesive layer protruding outward from the outer periphery of the test piece after heat treatment. Residues are observed.

Example 1
The filler (F1) and the adhesive polymer 1 (ADH1) were mixed to prepare an adhesive solution. The adhesive solution contained 100 parts by mass of ADH1 and 5 parts by mass of F1 in terms of solid content. In terms of solid content, the cross-linking agent 1 (CL1) was added to the adhesive solution in an amount such that CL1 was 0.20 parts by mass with respect to 100 parts by mass of ADH1. The solid content of the adhesive solution was 70% by mass. The adhesive solution was applied on the silicone-treated surface of the release liner 1 (L1) with a knife coater. The coated layer was dried at 95 ° C. for 5 minutes to obtain a transparent pressure-sensitive adhesive layer having a thickness of 38 μm. The transparent pressure-sensitive adhesive layer was bonded to a 170 μm thick polyvinyl chloride film to obtain a decorative sheet of Example 1.

Examples 2 to 17 and Comparative Examples 1 to 5
The decorative sheets of Examples 2 to 17 and Comparative Examples 1 to 5 were produced in the same manner as the decorative sheets of Example 1. Table 3 shows the types of adhesive polymers, solid content, types and amounts of fillers, types and amounts of cross-linking agents, types of release liners, and pressure-sensitive adhesive layers of these decorative sheets.

Example 18
The filler (F1) and the adhesive polymer 2 (ADH2) were mixed to prepare an adhesive solution. The adhesive solution contained 100 parts by mass of ADH2 and 5 parts by mass of F1 in terms of solid content. The cross-linking agent 4 (CL4) was added to the adhesive solution in an amount of 2.0 parts by mass of CL4 with respect to 100 parts by mass of ADH2 in terms of solid content. The solid content of the adhesive solution was 60% by mass. The adhesive solution was applied on the silicone-treated surface of the release liner 2 (L2) with a knife coater. The coated layer was dried at 95 ° C. for 5 minutes to form a transparent pressure-sensitive adhesive layer having a thickness of 38 μm. The transparent pressure-sensitive adhesive layer was irradiated with ultraviolet rays using a high-pressure mercury lamp. The irradiation amount of UVC was 60 mJ / cm ² . The transparent pressure-sensitive adhesive layer was bonded to a 170 μm thick polyvinyl chloride film to obtain a decorative sheet of Example 18.

Example 19
The decorative sheet of Example 19 was obtained by the same procedure as in Example 18 except that CL4 was 4 parts by mass and the UVC irradiation amount was 30 mJ / cm ² .

Example 20
The decorative sheet of Example 20 was obtained by the same procedure as in Example 19 except that the UVC irradiation amount was 60 mJ / cm ² .

Table 4 shows the evaluation results of the decorative sheets of Examples 1 to 18 and Comparative Examples 1 to 8. Table 5 shows the 20 ° C. initial adhesive strength of the melamine-baked coated plate for Examples 8 to 10, and the 20 ° C. initial adhesive strength of the aluminum plate for Examples 9 to 10.

It will be apparent to those skilled in the art that the above embodiments and examples can be variously modified without departing from the basic principles of the present invention. It is also apparent to those skilled in the art that various improvements and modifications of the present invention can be carried out without departing from the spirit and scope of the present disclosure. A part of the embodiment of the present invention is described in the following aspects 1 to 7.
[Aspect 1]
A decorative sheet containing a base layer and an adhesive layer arranged on or above the base layer, wherein the adhesive layer contains a (meth) acrylic polymer having a weight average molecular weight of 400,000 or less and hydrophobic nanosilica particles. A decorative sheet containing a cured product of the pressure-sensitive adhesive composition containing 0.1 to 25 parts by mass of the hydrophobic nanosilica particles based on 100 parts by mass of the (meth) acrylic polymer.
[Aspect 2]
The decorative sheet according to aspect 1, wherein the (meth) acrylic polymer has a glass transition temperature of −40 ° C. or lower.
[Aspect 3]
The decorative sheet according to any one of aspects 1 or 2, wherein the (meth) acrylic polymer contains 50% by mass or more of units derived from a (meth) acrylic ester monomer having an alkyl group having 8 or more carbon atoms.
[Aspect 4]
The decorative sheet according to any one of aspects 1 to 3, wherein the adhesive layer contains 5 to 10 parts by mass of the hydrophobic nanosilica particles based on 100 parts by mass of the (meth) acrylic polymer.
[Aspect 5]
The decorative sheet according to any one of aspects 1 to 4, wherein the hydrophobic nanosilica particles have an average primary particle size of 100 nm or less.
[Aspect 6]
The decorative sheet according to any one of aspects 1 to 5, wherein the pressure-sensitive adhesive composition comprises a thermal cross-linking agent selected from the group consisting of an epoxy-based cross-linking agent and a bisamide cross-linking agent.
[Aspect 7]
The decorative sheet according to any one of aspects 1 to 5, wherein the pressure-sensitive adhesive composition contains an ultraviolet cross-linking agent having a structure capable of extracting hydrogen radicals by irradiation with ultraviolet rays.

10 Decorative sheet 12 Base layer 14 Adhesive layer 16 Hydrophobic nanosilica particles

Claims (5)

A decorative sheet including a base layer and an adhesive layer arranged on or above the base layer, wherein the adhesive layer contains a (meth) acrylic polymer having a weight average molecular weight of 400,000 or less and hydrophobic nanosilica particles. It contains a cured product of the pressure-sensitive adhesive composition, and contains 0.1 to 25 parts by mass of the hydrophobic nanosilica particles based on 100 parts by mass of the (meth) acrylic polymer, and contains 0.1 to 25 parts by mass of the (meth) acrylic polymer. A decorative sheet having a glass transition temperature of −40 ° C. or lower, and the (meth) acrylic polymer containing 50% by mass or more of units derived from a (meth) acrylic ester monomer having 8 or more carbon atoms of an alkyl group . The decorative sheet according to claim 1 , wherein the adhesive layer contains 5 to 10 parts by mass of the hydrophobic nanosilica particles based on 100 parts by mass of the (meth) acrylic polymer. The decorative sheet according to claim 1 or 2 , wherein the hydrophobic nanosilica particles have an average primary particle size of 100 nm or less. The decorative sheet according to any one of claims 1 to 3 , wherein the pressure-sensitive adhesive composition contains a thermal cross-linking agent selected from the group consisting of an epoxy-based cross-linking agent and a bisamide cross-linking agent. The decorative sheet according to any one of claims 1 to 3 , wherein the pressure-sensitive adhesive composition contains an ultraviolet cross-linking agent having a structure capable of extracting hydrogen radicals by irradiation with ultraviolet rays.

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