Laminated sheets and keychains

Abstract

The present invention provides a laminated sheet having a printable layer that exhibits high odor suppression characteristics while maintaining excellent print adhesion, a laminated sheet having a printed layer on its surface with excellent print adhesion and exhibiting high odor suppression characteristics, and a keychain. [Solution] A laminated sheet having a base layer made of a methacrylic resin and a surface layer on at least one surface of the base layer, or a laminated sheet further having a printed layer on the surface of the surface layer, wherein the surface layer is made of a methacrylic resin containing a copolymer of alkyl methacrylate and alkyl acrylate and rubber particles, and a key holder.

Description

Technical Field

[0001] The present invention relates to a laminated sheet and a key holder.

Background Art

[0002] Printed matter obtained by printing a design (including images, patterns, characters, solid printing, etc.) on the surface of a resin plate (resin sheet) has been widely used as advertising media, displays, etc. Particularly, due to recent improvements in printing technology, its use has also expanded to novelty goods and furniture used in events and amusement, such as key holders, straps, figures, acrylic stands, panels, etc. Usually, regardless of the application, after printing a predetermined design or the like on the surface of the resin plate, the printed matter is cut and machined by laser processing or the like to be formed into a predetermined shape. Therefore, for the printed matter and the resin plate constituting the printed matter (hereinafter sometimes simply referred to as "printed matter and resin plate"), ink adhesion on its surface (also referred to as printing adhesion) and characteristics for suppressing the generation of odors due to evaporation gas during laser processing (odor generation suppression characteristics during laser cutting, also simply referred to as odor generation suppression characteristics) are required.

[0003] As a laminated sheet having good printing adhesion and odor generation suppression characteristics in inkjet printing, for example, Patent Document 1 describes the following laminated sheet. "A laminated sheet having a base material layer and a surface layer laminated on at least one side of the base material layer, where the surface layer contains a styrene copolymer (S), the styrene copolymer (S) is one or more styrene copolymers selected from the group consisting of acrylonitrile-styrene copolymer (AS) containing 75 to 95% by mass of styrene units and styrene-maleic anhydride copolymer (SMA) containing 60 to 95% by mass of styrene units, the base material layer is composed of a methacrylic resin composition (MR) containing a methacrylic resin (M) containing 80 to 100% by mass of methyl methacrylate units and a styrene copolymer (S), The content of styrene monomer units in the substrate layer is 0.5 to 10.0% by mass. The substrate layer has a perfectly miscible structure of a styrene copolymer (S) and a methacrylic resin (M), or a sea-island structure in which a plurality of particulate island phases containing the styrene copolymer (S) are dispersed in a sea phase containing the methacrylic resin (M), and the maximum diameter of the plurality of particulate island phases is greater than 0 nm and less than or equal to 50 nm. A laminated sheet in which the ratio of the total thickness of the surface layer to the total thickness of the laminated sheet is 1 to 20%. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7487396 specification [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in recent years, with the increasing resolution of designs and patterns printed on printed materials, and with growing awareness of occupational safety and hygiene, there is a demand for printed materials and resin sheets to further enhance odor suppression characteristics while maintaining excellent print adhesion. However, although the laminated sheet described in Patent Document 1 is said to have good odor suppression characteristics, it contains a styrene copolymer (S), and therefore, Patent Document 1 does not consider highly suppressing the odor derived from styrene (also called styrene odor) generated during laser cutting.

[0006] The present invention aims to provide a laminated sheet having a printable layer that exhibits high odor suppression characteristics while maintaining excellent print adhesion. Furthermore, the present invention aims to provide a laminated sheet having a printable layer on its surface with excellent print adhesion and exhibiting high odor suppression characteristics, and a keychain containing this laminated sheet. [Means for solving the problem]

[0007] Styrene copolymers, used as materials for forming printed materials and resin sheets, can achieve excellent print adhesion but tend to generate odors and have poor odor suppression properties, exhibiting conflicting characteristics of print adhesion and odor suppression. Therefore, conventionally, in printed materials and resin sheets, as shown in Patent Document 1, it has been common to use styrene copolymer (S) to achieve excellent print adhesion while compromising to some extent on odor suppression properties by reducing the content of styrene structural units present in the printed material and resin sheet (finding a balance between print adhesion and odor suppression properties). The inventors of the present invention, in order to achieve advanced odor suppression characteristics for printed materials and resin plates, shifted their thinking from conventional methods and diligently investigated printed materials and resin plates that could achieve excellent print adhesion while exhibiting advanced odor suppression characteristics without using styrene copolymer (S) as a component of the printed materials and resin plates. As a result, the inventors of the present invention found that by adopting a resin layer formed from a methacrylic resin containing a copolymer of alkyl methacrylate and alkyl acrylate and rubber particles as a surface layer provided on the surface of a base layer made of methacrylic resin, advanced odor suppression characteristics could be achieved while the resin layer also exhibited excellent print adhesion.

[0008] In other words, the objectives of the present invention were achieved by the following means. <1> A laminated sheet having a base layer made of a methacrylic resin and a surface layer on at least one surface of the base layer, A laminated sheet in which the surface layer is a printable layer made of a methacrylic resin containing a copolymer of alkyl methacrylate and alkyl acrylate and rubber particles. <2> A laminated sheet having a base layer made of a methacrylic resin, a surface layer on at least one surface of the base layer, and a printed layer on the surface of the surface layer, A laminated sheet in which the surface layer is made of a methacrylic resin containing a copolymer of alkyl methacrylate and alkyl acrylate and rubber particles. <3> The copolymer of alkyl methacrylate and alkyl acrylate is a copolymer of methyl methacrylate and butyl acrylate. <1> or <2> The laminated sheet described above. <4> The methacrylic resin forming the base layer is a polymer of methyl methacrylate. <1> ~ <3> A laminated sheet as described in any one of the items. <5> The aforementioned printed layer is a layer printed using one or more of the following printing methods: inkjet printing, UV printing, screen printing, and offset printing. <2> ~ <4> A laminated sheet as described in any one of the items. <6> the above <2> ~ <5> A keychain containing a laminated sheet as described in any one of the items. [Effects of the Invention]

[0009] The present invention provides a laminated sheet having a printable layer that exhibits high odor suppression characteristics while maintaining excellent print adhesion. Furthermore, the present invention provides a laminated sheet having a printed layer on its surface with excellent print adhesion and exhibiting high odor suppression characteristics, and a keychain containing this laminated sheet. [Modes for carrying out the invention]

[0010] In the present invention and this specification, "(meth)acrylic" means either or both acrylic and methacrylic. Furthermore, in the present invention and this specification, the bonding mode (arrangement of structural units) of two or more structural units in a copolymer is not particularly limited and includes, for example, random bonding (random copolymer), block bonding (block copolymer), alternating bonding (alternating copolymer), graft bonding (graft copolymer), and the like. In the present invention and this specification, when describing content, physical properties, etc., by indicating numerical ranges, if the upper and lower limits of the numerical range are described separately, either upper or lower limit can be appropriately combined to form a specific numerical range. On the other hand, when multiple numerical ranges represented by "~" are set and described, the upper and lower limits forming the numerical range are not limited to a specific combination of the upper and lower limits described before and after "~" as a specific numerical range, but can be a numerical range formed by appropriately combining the upper and lower limits of each numerical range. In the present invention and this specification, a numerical range represented by "~" means a range that includes the numbers described before and after "~" as the lower and upper limits.

[0011] [[Laminated Sheet]] The laminated sheets of the present invention include laminated sheets having a printable layer as a surface layer on at least one surface of the base layer (laminated sheets without a printed layer) and laminated sheets having a surface layer on at least one surface of the base layer and a printed layer on the surface of the surface layer (laminated sheets with a printed layer). In the present invention, a laminated sheet without a printed layer corresponds to the material that forms a laminated sheet with a printed layer, and is a laminated sheet on which a design or pattern is to be printed (a printed layer is formed) on the surface of its printable layer. Therefore, the surface layer of a laminated sheet without a printed layer is the outermost layer (exposed layer) and becomes the printable layer (printing surface layer) on which the printed layer is to be formed. In the present invention, when clearly distinguishing between the two, a laminated sheet without a printed layer is referred to as a "printing laminated sheet," and a laminated sheet with a printed layer is referred to as a "printed material" or "printed laminated sheet."

[0012] The laminated sheets of the present invention include laminated sheets having a surface layer on one surface of the base layer (for convenience, referred to as "two-layer laminated sheets") and laminated sheets having surface layers on both surfaces of one of the base layers (for convenience, referred to as "three-layer laminated sheets"). In the laminated sheets of the present invention, the base layer and the surface layer may each have a single-layer structure or a multi-layer structure. Furthermore, the laminated sheets of the present invention may have layers that do not correspond to either the base layer or the surface layer. In the three-layer laminated sheet, the surface layer and the printing layer may be the same or different from each other.

[0013] The total thickness of the laminated sheet of the present invention is not particularly limited, but is usually 0.1 to 10.0 mm, preferably 0.2 to 5.0 mm, and more preferably 0.3 to 3.0 mm. The thickness of the base layer is not particularly limited, but is preferably 0.1 to 10.0 mm, and more preferably 0.2 to 5.0 mm. The thickness of the surface layer is not particularly limited, but is preferably 0.01 to 0.5 mm, and more preferably 0.02 to 0.3 mm. Each surface layer in the three-layer laminated sheet may have the same thickness or different thicknesses. In the laminated sheet of the present invention, the ratio [total thickness of surface layer / thickness of base layer] between the thickness of the base layer and the total thickness of the surface layer is not particularly limited, and can be, for example, 0.01 to 0.30, and preferably 0.02 to 0.25.

[0014] The laminated sheet of the present invention has an appropriate sheet shape (plate shape) in consideration of the usage mode and the like. For example, it may be a strip-shaped sheet or a short sheet (single-sheet), but is preferably a long sheet.

[0015] [Base layer] The base layer is formed of a methacrylic resin. In the present invention, the methacrylic resin refers to a resin (resin composition) containing a polymer of methacrylic acid ester, and may contain other components described later. The polymer of methacrylic acid ester is a polymer in which the content of the structural unit derived from methacrylic acid ester is 50 mol% or more and the content of the structural unit derived from acrylic acid ester is less than 50 mol% with respect to the total content of all structural units constituting the polymer. This polymer may contain other structural units other than the structural unit derived from methacrylic acid ester.

[0016] The methacrylic acid ester is not particularly limited, and examples include alkyl methacrylates, aryl methacrylates, etc., and alkyl methacrylates are preferred. The alkyl group constituting the alkyl methacrylate is not particularly limited, but an alkyl group having 1 to 8 carbon atoms is preferred, and an alkyl group having 1 to 4 carbon atoms is more preferred. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, benzyl methacrylate, etc. In the present invention, propyl includes n-propyl and iso-propyl, and butyl includes n-butyl, tert-butyl, sec-butyl, and iso-butyl. The methacrylic acid ester preferably includes methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate, and more preferably includes methyl methacrylate. The polymer of the methacrylic acid ester may contain one or more structural units derived from the above methacrylic acid ester.

[0017] Other compounds (monomers) that can lead to structural units are not particularly limited as long as they are copolymerizable with methacrylic acid esters, and include monofunctional monomers having one polymerizable carbon-carbon double bond in the molecule, and polyfunctional monomers having two or more polymerizable carbon-carbon double bonds in the molecule. Examples of such monofunctional monomers include (meth)acrylic acid; acrylic acid esters; aromatic vinyl compounds such as styrene and α-methylstyrene; vinyl cyanide compounds such as (meth)acrylonitrile and (meth)acrylamide; and unsaturated carboxylic acids such as maleic acid and itaconic acid (excluding (meth)acrylic acid). Acrylic acid esters are not particularly limited, but examples include acrylic acid esters corresponding to the methacrylic acid esters mentioned above. Examples of polyfunctional monomers include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, and trimethylolpropane triacrylate; alkenyl esters of unsaturated carboxylic acids such as allyl acrylate, allyl methacrylate, and allyl cinnamate; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, and triallyl isocyanurate; and aromatic polyalkenyl compounds such as divinylbenzene. The methacrylate ester polymer may contain one or more of the above-mentioned other structural units.

[0018] The alkyl methacrylate polymer is preferably a polymer of methyl methacrylate, and more preferably a homopolymer of methyl methacrylate.

[0019] The content of each structural unit in the total 100 mol% of all structural units constituting the methacrylic acid ester polymer is set as appropriate, but is preferably set within the following range. In a polymer of methacrylic acid ester, the content of structural units derived from methacrylic acid ester is preferably 90 mol% or more, more preferably 91 to 99.5 mol%, and even more preferably 92 to 99 mol%. In the total content of all structural units constituting the methacrylic acid ester polymer (100 mol%), the content of other structural units is appropriately determined according to the application, properties, etc., and can be, for example, 10 mol% or less, preferably 0.5 to 9 mol%, and more preferably 1 to 8 mol%.

[0020] In the present invention, the content of each structural unit in the polymer can be calculated from the amount of compound used to derive each structural unit from the polymerization, and can also be measured by known methods, such as the method described in the examples below. Furthermore, if a polymer of methacrylic acid ester contains two or more of each structural unit, the above-mentioned content of each structural unit shall be the total content of the two or more structural units.

[0021] The properties and physical characteristics of methacrylic acid ester polymers are not particularly limited and are determined appropriately according to the application, the characteristics of the laminated sheet, etc. For example, the weight-average molecular weight of methacrylic acid ester polymers is not particularly limited, but 5 × 10 4 ~5×10 5 It can be done this way.

[0022] (Method for synthesizing polymers of methacrylate esters) The methacrylate ester polymer can be synthesized in the same manner as the synthesis method for copolymer (A) that forms the surface layer, as described later.

[0023] (Other ingredients) The methacrylic resin, i.e., the base layer, may optionally contain other components besides polymers of methacrylic acid esters. These other components are not particularly limited and may include, for example, rubber particles (described later); antistatic agents such as sodium alkyl sulfonate, sodium alkyl sulfonate, sodium alkyl sulfate, monoglyceride stearate, and polyether ester amide; antioxidants such as hindered phenol; flame retardants such as phosphate esters; lubricants such as palmitic acid and stearyl alcohol; light stabilizers such as hindered amines; UV absorbers such as benzotriazole-based UV absorbers, benzophenone-based UV absorbers, cyanoacrylate-based UV absorbers, malonic acid-based UV absorbers, oxalic acid anilide-based UV absorbers, and acetate-based UV absorbers; light diffusers; dyes; pigments; and fluorescent whitening agents. The other components may optionally contain two or more of these.

[0024] In the present invention, the base layer may be colored or colorless, but it is preferably colorless and transparent. For example, one preferred embodiment is that the methacrylic resin forming the base layer does not contain pigments and dyes as other components. In the present invention, the statement that the methacrylic resin forming the base layer does not contain pigments and dyes is not particularly limited as long as the base layer maintains colorless transparency, but for example, it means that the pigments and dyes are contained in an amount of less than 2% by mass (total content) per 100% by mass of the methacrylic resin.

[0025] (Composition of methacrylic resin) The methacrylic resin forming the base layer only needs to contain the polymer of the methacrylic acid ester described above, and the content of each component (composition of the composition) is not particularly limited and is determined appropriately according to the application, the characteristics of the laminated sheet, etc., and is preferably set within the following range, for example. The content of the methacrylic acid ester polymer in 100 parts by mass of methacrylic resin is not particularly limited, but is preferably 90 parts by mass or more, more preferably 91 to 99 parts by mass, and even more preferably 92 to 98 parts by mass. The total content of other components in 100 parts by mass of methacrylic resin can be appropriately determined within a range that does not impair the effects of the present invention, and can be, for example, 10 parts by mass or less.

[0026] (Preparation of methacrylic resin) The methacrylic resin forming the base layer can be a commercially available product or a prepared product. When preparing the methacrylic resin, it can be prepared by melt-mixing the polymer of the methacrylic acid ester mentioned above with other components as appropriate. For example, it can be prepared in the same manner as the methacrylic resin forming the surface layer described later, except that rubber particles are not mixed in.

[0027] [Surface layer] The surface layer is formed of a methacrylic resin (resin composition) containing a copolymer of alkyl methacrylate and alkyl acrylate, and rubber particles.

[0028] (Copolymer (A)) The copolymer (A) of alkyl methacrylate and alkyl acrylate may also be a copolymer that contains structural units derived from another monomer (a) that does not correspond to either alkyl methacrylate or alkyl acrylate.

[0029] The alkyl methacrylate (monomer) that forms copolymer (A) is not particularly limited and includes those described above for alkyl methacrylate esters, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. Among the alkyl methacrylates that form copolymer (A), methyl methacrylate is preferred.

[0030] The alkyl acrylate (monomer) that forms copolymer (A) is not particularly limited, and examples include acrylic acid esters corresponding to the alkyl methacrylates mentioned above, such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. Among the alkyl acrylates, butyl acrylate is preferred, and n-butyl acrylate is more preferred.

[0031] Other monomers (a) include monomers other than acrylic acid esters from the monomers described above in the section on compounds that derive other structural units.

[0032] Copolymer (A) may be a block copolymer, but is preferably a random copolymer. In one preferred embodiment, the methacrylic resin forming the surface layer does not contain a block copolymer as copolymer (A). In the present invention, "the methacrylic resin does not contain a block copolymer" means that it contains a block copolymer in an amount of less than 1% by mass per 100% by mass of the methacrylic resin. The copolymer (A) is preferably a copolymer of methyl methacrylate and butyl acrylate (particularly n-butyl acrylate) in terms of print adhesion and odor generation suppression properties. The mass ratio (content) of alkyl methacrylate and alkyl acrylate in copolymer (A) is not particularly limited and can be determined as appropriate. For example, based on a total of 100% by mass of alkyl methacrylate and alkyl acrylate, the content of alkyl methacrylate is preferably 40 to 90% by mass, and more preferably 40 to 80% by mass. On the other hand, based on the above total of 100% by mass, the content of alkyl acrylate is preferably 60 to 10% by mass, and more preferably 60 to 20% by mass.

[0033] Copolymer (A) can also be made in combination of two or more types. The combination of two or more copolymers (A) is not particularly limited, but a combination including a copolymer of methyl methacrylate and butyl acrylate (preferably n-butyl acrylate) is preferred. Specifically, a combination including a copolymer of methyl methacrylate and butyl acrylate (preferably n-butyl acrylate) and a copolymer of methyl methacrylate and methyl acrylate is preferred. The mass ratio of the copolymer of methyl methacrylate and butyl acrylate and the copolymer of methyl methacrylate and methyl acrylate is preferably such that, based on a total of 100% by mass of these copolymers, the content of the copolymer of methyl methacrylate and butyl acrylate is 50 to 90% by mass, and the content of the copolymer of methyl methacrylate and methyl acrylate is 50 to 10% by mass, more preferably, the content of the copolymer of methyl methacrylate and butyl acrylate is 70 to 90% by mass, and the content of the copolymer of methyl methacrylate and methyl acrylate is 30 to 10% by mass.

[0034] The properties and physical characteristics of copolymer (A) are not particularly limited and are determined appropriately according to the application, the characteristics of the laminated sheet, etc. For example, the weight-average molecular weight of copolymer (A) is not particularly limited, but is 5 × 10 4 ~5×10 5 It can be done this way.

[0035] (Method for synthesizing copolymer (A)) Copolymer (A) can be synthesized by conventional methods for synthesizing (meth)acrylic acid esters. For example, one method involves placing the above-mentioned monomers, a radical polymerization initiator, water, and a dispersant in a reactor and heating it while stirring to carry out suspension polymerization.

[0036] The radical polymerization initiator is not particularly limited and includes, for example, peroxide-based initiators such as lauroyl peroxide, benzoyl peroxide, di-t-butyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butyl peroxybenzoate, t-butyl peroxyacetate, diisopropyl peroxycarbonate, and di-s-butyl peroxycarbonate, as well as azo-based initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile). In the synthesis method of copolymer (A), a suspension stabilizer may also be used. The suspension stabilizer is not particularly limited and includes known suspension stabilizers such as alkali polymethacrylate salts (sodium salt, potassium salt, etc.), sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, boric acid, sodium carbonate, disodium hydrogen phosphate, disodium hydrogen phosphate, and sodium sulfate. Furthermore, in the method for synthesizing copolymer (A), a chain transfer agent may be used to adjust the molecular weight of the polymer. The chain transfer agent is not particularly limited and includes known chain transfer agents such as alkyl mercaptans, alkyl sulfides, alkyl disulfides, thioglycolic acid esters, and α-methylstyrene dimers.

[0037] The amount of radical polymerization initiator mixed is preferably 0.02 to 2 parts by mass, more preferably 0.05 to 1 part by mass, per 100 parts by mass of the total monomers. The amount of suspension stabilizer mixed is preferably 0.001 to 2 parts by mass, more preferably 0.01 to 0.5 parts by mass, per 100 parts by mass of the total monomers. The amount of chain transfer agent mixed is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 1 part by mass, per 100 parts by mass of the total monomers.

[0038] Polymerization is preferably carried out at a relatively low temperature to prevent monomer residue. Typically, the polymerization reaction can be completed by heating at 60-80°C for 30 minutes to 3 hours under stirring, followed by raising the temperature to 80-130°C for 10 minutes to 2 hours. In this way, for example, copolymer particles with an average particle size of about 100-800 μm can be obtained as copolymer (A).

[0039] (rubber particles) The methacrylic resin that makes up the surface layer contains rubber particles. The inclusion of rubber particles in the methacrylic resin allows for high odor suppression while also providing excellent print adhesion to the surface layer. The rubber particles are not particularly limited, and for example, (meth)acrylic rubber particles, butadiene rubber particles, styrene-butadiene rubber particles, etc. can be used, but among these, (meth)acrylic rubber particles are preferred in terms of weather resistance and durability. (Meth)acrylic rubber particles include those having a layer (also called an elastic copolymer layer or a soft polymer layer) made of an elastic polymer (soft polymer) mainly composed of (meth)acrylic acid ester. These may be single-layer particles consisting only of an elastic copolymer layer, or multilayer particles consisting of an elastic copolymer layer and a layer made of a hard polymer (hard polymer layer). In the present invention, one or more types of rubber particles can be used.

[0040] The multilayer structure constituting the (meth)acrylic rubber particles only needs to include an elastic polymer layer. For example, a two- to four-layer structure including an elastic polymer layer is possible, and a two-layer or three-layer structure is preferred.

[0041] <Three-layer structure (meth)acrylic rubber particles> The three-layered (meth)acrylic rubber particles are not particularly limited, but are preferably spherical (meth)acrylic rubber particles with a three-layered structure consisting of an inner layer made of a hard polymer mainly composed of alkyl methacrylate, an intermediate layer made of an elastic copolymer mainly composed of alkyl acrylate, and an outer layer made of a hard polymer mainly composed of alkyl methacrylate. These three-layered spherical (meth)acrylic rubber particles have a so-called core-shell structure.

[0042] In the above-described three-layer structure of (meth)acrylic rubber particles, the inner layer is a layer composed of a hard polymer mainly composed of alkyl methacrylate. This hard polymer is preferably obtained by polymerizing monomers consisting of 70-100% by mass (preferably 90-100% by mass) of alkyl methacrylate and 0-30% by mass (preferably 0-10% by mass) of another vinyl monomer copolymerizable thereto. As the alkyl methacrylate, esters having an alkyl group with about 1-4 carbon atoms, particularly methyl methacrylate, are advantageous. Other vinyl monomers that can be optionally used include, for example, acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and cyclohexyl acrylate, aromatic vinyl compounds such as styrene, and vinyl cyanide compounds such as acrylonitrile.

[0043] Furthermore, it is also effective to use copolymerizable crosslinkable monomers as other vinyl monomers. The crosslinkable monomer only needs to have at least two polymerizable carbon-carbon double bonds in one molecule; for example, the polyfunctional monomers described above for methacrylic acid ester polymers can be cited. Among these, alkenyl esters of unsaturated carboxylic acids and polyalkenyl esters of polybasic acids are preferred. These crosslinkable monomers can be used individually or in combination of two or more as needed. The rigid polymer constituting the inner layer preferably contains acrylic acid esters and crosslinkable monomers as other vinyl monomers, and more preferably contains 1 to 10% by mass (preferably 2 to 8% by mass) of acrylic acid esters and 0.1 to 1.0% by mass (preferably 0.2 to 0.8% by mass) of crosslinkable monomers in 100% by mass of the total monomers forming the rigid polymer.

[0044] The intermediate layer of the (meth)acrylic rubber particles in the above three-layer structure is a layer composed of an elastic copolymer mainly composed of alkyl acrylate. Specifically, it is preferable that the layer be an elastic copolymer obtained by polymerizing monomers consisting of 50 to 99.9% by mass (preferably 60 to 90% by mass) of alkyl acrylate, 0 to 49.9% by mass (preferably 9 to 30% by mass) of other vinyl monomers copolymerizable thereto (excluding copolymerizable crosslinkable monomers), and 0.1 to 10% by mass (preferably 1 to 10% by mass) of copolymerizable crosslinkable monomers. The intermediate layer can be formed by polymerizing the monomer mixture of the composition shown herein in the presence of the rigid polymer constituting the inner layer. Two or more types of alkyl acrylate, other vinyl monomers, and crosslinkable monomers may be used, as long as their compositions fall within the above ranges.

[0045] Examples of alkyl acrylates used here include those with 1 to 8 carbon atoms in the alkyl group. Among these, alkyl groups with 4 to 8 carbon atoms, such as butyl acrylate and 2-ethylhexyl acrylate, are preferred.

[0046] Other vinyl monomers that can be copolymerized with alkyl acrylate and are optionally used to constitute an elastic copolymer are monofunctional compounds having one polymerizable carbon-carbon double bond in one molecule. Specifically, suitable examples include methacrylic acid esters such as methyl methacrylate, butyl methacrylate, and cyclohexyl methacrylate, aromatic vinyl compounds such as styrene, and vinyl cyanide compounds such as acrylonitrile.

[0047] The copolymerizable crosslinkable monomers used to construct the elastic copolymer only need to have at least two polymerizable carbon-carbon double bonds in one molecule, and the same ones exemplified earlier as optional components constituting the inner rigid polymer layer can be used. For the elastic copolymer of the intermediate layer, alkenyl esters of unsaturated carboxylic acids or polyalkenyl esters of polybasic acids are preferably used.

[0048] The elastic polymer constituting the intermediate layer preferably contains styrene and a crosslinkable monomer, and more preferably contains 10 to 30% by mass (preferably 15 to 25% by mass) of styrene and 1 to 10% by mass (preferably 2 to 8% by mass) of the total monomers forming the elastic polymer.

[0049] The (meth)acrylic rubber particles with the above three-layer structure have an outer layer made of a hard polymer mainly composed of alkyl methacrylate, further outside the intermediate layer made of the elastic copolymer. This outer layer is preferably formed by polymerizing monomers consisting of 50 to 100% by mass (preferably 80 to 100% by mass) of alkyl methacrylate, 0 to 50% by mass (preferably 0 to 10% by mass) of an acrylic acid ester, and at least one other vinyl monomer copolymerizable with these, in the presence of the polymers formed as the inner layer and intermediate layer. As a result, at least one outer layer of polymer composed of the monomers shown above is bonded to the surface of the intermediate layer made of the elastic copolymer.

[0050] The alkyl methacrylate that forms the main component of the outer layer is preferably an ester having an alkyl group with approximately 1 to 8 carbon atoms, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate. Optional acrylic acid esters include alkyl esters of acrylic acid, such as methyl acrylate, ethyl acrylate, butyl acrylate, and cyclohexyl acrylate. Other vinyl monomers that can copolymerize with alkyl methacrylate and / or acrylic acid esters and can be optionally used include aromatic vinyl compounds such as styrene and vinyl cyanide compounds such as acrylonitrile.

[0051] The rigid polymer constituting the outer layer preferably contains an acrylic acid ester, and more preferably contains 1 to 10% by mass (preferably 2 to 8% by mass) of the acrylic acid ester in 100% by mass of the total monomers forming the rigid polymer.

[0052] In the above three-layer structure of (meth)acrylic rubber particles, the mass ratio of the inner layer / intermediate layer / outer layer is not particularly limited and can be set as appropriate, but for example, it is preferable to set it to 30-40 / 40-50 / 10-30.

[0053] The three-layered (meth)acrylic rubber particles described above can be manufactured, for example, by emulsion polymerization, which involves first polymerizing the monomers that will form the inner layer, polymerizing the monomers that will form the intermediate layer in the presence of the resulting polymer particles, and then polymerizing the monomers that will form the outer layer in the presence of the polymer particles that have been formed up to the intermediate layer. In this process, the particle size of the (meth)acrylic rubber particles can be adjusted by adjusting the amount of emulsifier added and the amount of monomers used.

[0054] In addition to the acrylic rubber particles described above, other examples of three-layered (meth)acrylic rubber particles include spherical (meth)acrylic rubber particles with a three-layer structure, consisting of an inner layer made of a hard polymer mainly composed of alkyl (meth)acrylate, an intermediate layer made of an elastic copolymer mainly composed of alkyl methacrylate, and an outer layer made of a hard polymer mainly composed of alkyl (meth)acrylate. These spherical (meth)acrylic rubber particles are the same as the three-layered spherical (meth)acrylic rubber particles described above, except that the main component of the polymer constituting the intermediate layer is alkyl methacrylate.

[0055] The particle size of the (meth)acrylic rubber particles in the above three-layer structure is not particularly limited and can be determined as appropriate. In terms of particle size, it is preferable that the particle size up to the intermediate layer is in the range of 0.2 to 0.30 μm on a mass average, in order to further improve print adhesion while maintaining odor suppression properties.

[0056] <Two-layer structure (meth)acrylic rubber particles> The two-layered (meth)acrylic rubber particles are not particularly limited, but are preferably spherical (meth)acrylic rubber particles with a two-layered structure consisting of an inner layer made of a hard polymer mainly composed of alkyl methacrylate and an outer layer made of an elastic copolymer mainly composed of alkyl methacrylate. These two-layered spherical (meth)acrylic rubber particles have a so-called core-shell structure.

[0057] In the above-described two-layer structure of (meth)acrylic rubber particles, the inner layer is composed of a rigid polymer mainly composed of alkyl methacrylate. This rigid polymer is preferably obtained by polymerizing monomers consisting of 50-100% by mass (preferably 60-70% by mass) of alkyl methacrylate and 0-50% by mass (preferably 30-40% by mass) of another vinyl monomer copolymerizable thereto. As the alkyl methacrylate, esters having an alkyl group with about 1-4 carbon atoms, particularly methyl methacrylate, are advantageous. Other vinyl monomers that can be optionally used include, for example, acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and cyclohexyl acrylate, aromatic vinyl compounds such as styrene, and vinyl cyanide compounds such as acrylonitrile. Two or more of each of the other vinyl monomers, especially the acrylic acid esters, can also be used. Furthermore, it is also effective to use a copolymerizable crosslinkable monomer as one of the other vinyl monomers. The crosslinkable monomer is the same as the crosslinkable monomer in the three-layer structured (meth)acrylic rubber particles described above.

[0058] The rigid polymer constituting the inner layer preferably contains acrylic acid esters and styrene as other vinyl monomers, and more preferably contains 0 to 40% by mass (preferably 5 to 30% by mass) of acrylic acid ester and 1 to 20% by mass (preferably 5 to 10% by mass) of styrene in 100% by mass of the total monomers forming the rigid polymer.

[0059] In the above-described two-layer structure of (meth)acrylic rubber particles, the outer layer is a layer composed of an elastic copolymer mainly composed of alkyl methacrylate. Specifically, it is preferable that the layer is an elastic copolymer obtained by polymerizing monomers consisting of 80-99% by mass (preferably 85-95% by mass) of alkyl methacrylate, 1-10% by mass (preferably 5-10% by mass) of other vinyl monomers copolymerizable thereto (excluding copolymerizable crosslinkable monomers), and 0-10% by mass (preferably 0-5% by mass) of copolymerizable crosslinkable monomers. The outer layer can be formed by polymerizing the monomer mixture of the composition shown herein in the presence of the rigid polymer that constitutes the inner layer. Two or more types of alkyl methacrylate, other vinyl monomers, and crosslinkable monomers may be used, provided that their compositions fall within the above-described ranges.

[0060] Examples of alkyl methacrylates included in the elastic copolymer include those with 1 to 8 carbon atoms in the alkyl group, preferably those with 1 to 4 carbon atoms, and more preferably methyl methacrylate. Other vinyl monomers that can be copolymerized with alkyl methacrylate and optionally used to constitute the elastic copolymer are monofunctional compounds having one polymerizable carbon-carbon double bond in one molecule. Specifically, suitable examples include atacrylate esters such as methyl atacrylate, butyl atacrylate, and cyclohexyl atacrylate, aromatic vinyl compounds such as styrene, and vinyl cyanide compounds such as acrylonitrile. Copolymerizable crosslinkable monomers used to constitute the elastic copolymer only need to have at least two polymerizable carbon-carbon double bonds in one molecule, and those similar to those exemplified as optional components constituting the rigid polymer of the inner layer can be used.

[0061] The elastic polymer constituting the outer layer preferably contains atacrylate esters, and more preferably contains 1 to 10% by mass (preferably 2 to 8% by mass) of methyl atacrylate and 0.1 to 2% by mass (preferably 0.5 to 1.5% by mass) of butyl acrylate in 100% by mass of the total monomers forming the elastic polymer.

[0062] In the above-described two-layer structure of (meth)acrylic rubber particles, the mass ratio of the inner layer to the outer layer is not particularly limited and can be set as appropriate, but for example, it is preferable to set it to 30-70 / 70-30.

[0063] The above-described two-layer (meth)acrylic rubber particles can be manufactured, for example, by first polymerizing the monomer that will form the inner layer using an emulsion polymerization method, and then polymerizing the monomer that will form the outer layer in the presence of the resulting polymer particles. In this process, the particle size of the (meth)acrylic rubber particles can be adjusted by adjusting the amount of emulsifier added and the amount of monomer added.

[0064] In addition to the acrylic rubber particles described above, other examples of two-layered (meth)acrylic rubber particles include spherical (meth)acrylic rubber particles with a two-layered structure, consisting of an inner layer made of a hard polymer mainly composed of alkyl methacrylate and an outer layer made of an elastic copolymer mainly composed of alkyl acrylate. These spherical (meth)acrylic rubber particles are the same as the two-layered spherical (meth)acrylic rubber particles described above, except that the main component of the polymer constituting the outer layer is alkyl acrylate. Furthermore, as a two-layered (meth)acrylic rubber particle, there is also a spherical (meth)acrylic rubber particle with a two-layered structure, consisting of an inner layer made of an elastic copolymer mainly composed of alkyl methacrylate and an outer layer made of a hard polymer mainly composed of alkyl methacrylate. This spherical (meth)acrylic rubber particle is the same as the two-layered spherical (meth)acrylic rubber particle described above, except that the inner and outer layers are swapped.

[0065] The particle size of the (meth)acrylic rubber particles in the above two-layer structure is not particularly limited and can be determined as appropriate. In terms of particle size, it is preferable that the inner layer particle size is in the range of 70 to 90 nm on a mass average, in order to further improve print adhesion while maintaining odor suppression properties.

[0066] As described above, the three-layer or two-layer (meth)acrylic rubber particles can be appropriately referenced from, for example, Japanese Patent Publication No. 55-27576 and Japanese Patent Application Publication No. 2013-022822, and their contents are incorporated as part of this specification.

[0067] (Other ingredients) The methacrylic resin forming the surface layer, i.e., the surface layer, may optionally contain other components besides copolymer (A) and rubber particles. These other components are not particularly limited and are the same as those contained in the methacrylic resin forming the base layer (except for rubber particles). In the present invention, the surface layer may be colored or colorless, but it is preferably colorless and transparent. For example, one preferred embodiment is that the methacrylic resin forming the surface layer does not contain pigments and dyes as other components. In the present invention, the statement that the methacrylic resin forming the surface layer does not contain pigments and dyes is not particularly limited as long as the surface layer maintains colorless transparency, but for example, it means that the methacrylic resin contains pigments and dyes in an amount of less than 2% by mass (total content) per 100% by mass of the methacrylic resin.

[0068] (Composition of methacrylic resin) The methacrylic resin forming the surface layer only needs to contain the copolymer (A) and rubber particles described above. The content of each component (composition of the composition) is not particularly limited and is determined appropriately according to the application, the characteristics of the laminated sheet, etc. For example, it is preferably set within the following range. The content of copolymer (A) in 100 parts by mass of methacrylic resin is not particularly limited, and can be, for example, 10% by mass or more, preferably 20 parts by mass or more, more preferably 40 to 90 parts by mass, and even more preferably 50 to 80 parts by mass. The content of rubber particles in 100 parts by mass of methacrylic resin is not particularly limited, and can be, for example, 10 parts by mass or more, preferably 20 to 90% by mass, more preferably 20 to 60 parts by mass, and even more preferably 30 to 50 parts by mass. The total content of other components in 100 parts by mass of methacrylic resin can be appropriately determined within a range that does not impair the effects of the present invention, and can be, for example, 10 parts by mass or less.

[0069] (Preparation of methacrylic resin) The methacrylic resin forming the surface layer can be a commercially available product or a specially prepared product. When preparing the methacrylic resin, it can be prepared by melt-mixing the copolymer (A), the rubber particles, and other components as appropriate. For example, the preparation method described in the examples below can be used.

[0070] [Other layers] The laminated sheet of the present invention may have a layer that does not correspond to the base layer, the surface layer, or the printing layer described later (referred to as "other layers" in the present invention). Depending on its function, the other layer may be provided between the base layer and the surface layer, or on the surface of the surface layer (excluding the layer to be printed). Other layers include thermoplastic resin layers, adhesive layers, primer layers, surface curing layers, and protective layers for the surface or printed layer.

[0071] Examples of thermoplastic resin layers include layers formed from thermoplastic resins that do not correspond to either the methacrylic resin forming the base layer or the methacrylic resin forming the surface layer. Such thermoplastic resins are not particularly limited, but examples include polycarbonate resin, polyvinyl chloride resin, acrylonitrile-butadiene-styrene resin, low-density polyethylene resin, high-density polyethylene resin, linear low-density polyethylene resin, polystyrene resin, polypropylene resin, acrylonitrile-styrene resin, cellulose acetate resin, ethylene-vinyl acetate resin, acrylic-acrylonitrile-styrene resin, acrylic-chlorinated polyethylene resin, ethylene-vinyl alcohol resin, fluororesin, methyl methacrylate-styrene resin, polyacetal resin, polyamide resin, polyethylene terephthalate resin, and In addition to general-purpose or engineering plastics such as lysulfone resins, polyethersulfone resins, methylpentene resins, polyarylate resins, polybutylene terephthalate resins, resins containing ethylenically unsaturated monomer units with alicyclic structures, polyphenylene sulfide resins, polyphenylene oxide resins, and polyetheretherketone resins, other examples include polyvinyl chloride elastomers, chlorinated polyethylene, ethylene-ethyl acrylate resins, thermoplastic polyurethane elastomers, thermoplastic polyester elastomers, ionomer resins, styrene-butadiene block polymers, ethylene-propylene rubber, and polybutadiene resins. For thermoplastic resins, those that do not contain structural units derived from styrene are preferred in terms of odor suppression properties. One type of thermoplastic resin may be used, or two or more types may be used.

[0072] [Print layer] The laminated sheet (printed material, pre-printed laminated sheet) of the present invention has a printed layer on the surface of at least one of the surface layers. The surface on which the printed layer is formed may be the entire surface of the surface layer or a part of the surface. The surface region on which the printed layer is formed can be appropriately determined according to the application and purpose of the laminated sheet. The printed layer may be any layer formed using a known ink and a known printing method. For example, it is preferable that the layer be formed using the inks described later and one of the following printing methods or a combination of two or more methods. In this invention, the design printed (formed) on the surface of the surface layer is conveniently referred to as the printed layer, but the printed layer does not necessarily have to be layered depending on the design.

[0073] There are no particular restrictions on the printing method, and any appropriate printing method can be adopted. Examples include plated printing methods such as flexographic printing, gravure printing, offset printing, and (silk)screen printing, and plateless printing methods such as electrostatic printing, inkjet printing, and laser printing. UV printing using ultraviolet (UV) curable inks is also an option. Two or more of the above printing methods can also be combined. An example of a combined printing method is a printing method that combines UV printing with inkjet printing, offset printing, flexographic printing, or screen printing (a printing method using UV curable inks). Of the printing methods listed above, inkjet printing, UV printing, screen printing, and offset printing are preferred, as is a combination of two or more of these methods. Among these, inkjet printing, UV printing, screen printing, and offset printing (inkjet printing using UV-curable ink) are more preferred because they allow for the printing of high-definition designs. Inkjet printing methods include electrostatic attraction, methods using piezoelectric elements such as piezo elements, and methods that heat the ink to cause foaming and utilize the resulting pressure.

[0074] The ink (composition) forming the printed layer is not particularly limited, and various known inks commonly used in each printing method can be used. Among these, UV-curable inks are preferred because they are quick-drying and can form high-definition patterns. In particular, since the surface layer of the laminated sheet of the present invention exhibits high print adhesion, UV-curable inks that do not conventionally exhibit sufficient print adhesion to (meth)acrylic resins can be used by taking advantage of this characteristic.

[0075] (Method of manufacturing laminated sheets) The laminated sheet of the present invention can be manufactured by laminating a base layer and a surface layer, and optionally providing a printed layer on the surface of the surface layer. The method for producing a laminated sheet for printing (a laminated sheet without a printed layer) by laminating a base layer and a surface layer is not particularly limited, and it may be produced by separately producing the base layer and surface layer and then laminating them by a conventional method, but in terms of workability and other factors, it is preferable to produce it by co-extruding the base layer and surface layer. The method for producing a laminated sheet with a printed layer (a printed material) may be to form a printed layer on a surface layer produced separately from the base layer and then laminate it with the base layer, but in terms of workability and other factors, it is generally preferable to produce the laminated sheet for printing and then form the printed layer. The methods for forming a printed layer on the surface of the surface layer include the various printing methods described above.

[0076] Methods for separately producing the base layer and surface layer include, for example, melt extrusion in which each resin layer is melt-extruded using an extruder and at least one side of the resulting plate-like material is brought into contact with a roll or belt to form it into a plate; and press molding in which each resin is formed into a plate using a heated press device.

[0077] One method for producing laminated sheets for printing by co-extrusion is to use multiple uni-screw or twin-screw extruders to melt-knead a methacrylic resin that forms the base layer and a methacrylic resin that forms the surface layer, and then laminate them via a feed block or multi-manifold die. Here, each methacrylic resin forming the base layer or surface layer can be used as pellets obtained by, for example, mixing a polymer, optionally rubber particles, and appropriately added additives in a super mixer or the like to obtain a mixture, and then melt-kneading the resulting mixture in an extruder. The conditions for the above-mentioned melt extrusion, heating press, and melt kneading can be appropriately selected to ensure that each methacrylic resin melts or softens. For example, the heating temperature can be set to 200-290°C.

[0078] (Applications of laminated sheets) The laminated sheet of the present invention can be used as a (material) sheet for exterior applications, signage applications (advertising media, displays), etc., but taking advantage of its properties, it can be suitably used as a (material) sheet for novelty goods and fixtures at events and amusement parks, such as keychains, straps, figurines, acrylic stands, panels, etc.

[0079] (molded product) The molded product of the present invention is formed by cutting and shaping a laminated sheet (printed laminated sheet) of the present invention into a predetermined shape using laser processing or the like. The laser processing conditions are not particularly limited, and ordinary conditions can be applied, for example, the laser cutting conditions in the embodiments described later. The shape, dimensions, etc. of the molded product are determined as appropriate depending on the application. The molded articles of the present invention can be used for exterior applications, signage (advertising media, displays), etc., but are particularly suitable for use as novelty goods and fixtures at events and amusement facilities. [Examples]

[0080] The following are examples of the present invention, but the present invention is not limited thereto.

[0081] [Preparation of methacrylic resin for forming the surface layer] <Synthesis of a copolymer of alkyl methacrylate and alkyl acrylate (A)> 80 parts by mass of methyl methacrylate, 20 parts by mass of n-butyl acrylate, 0.45 parts by mass of lauroyl peroxide, 0.14 parts by mass of dodecyl mercaptan, 120 parts by mass of deionized water, 0.03 parts by mass of 1.2% aqueous solution of polysodium methacrylate, 0.24 parts by mass of disodium hydrogen phosphate heptahydrate, and 0.28 parts by mass of monosodium hydrogen phosphate were placed in a reaction vessel and mixed, and the mixture was heated to 60°C to polymerize it and obtain a particulate random copolymer (A). In the obtained copolymer (A), the n-butyl acrylate content was 20% by mass, based on 100% by mass of the total of methyl methacrylate and n-butyl acrylate. Here, the n-butyl acrylate content was measured by pyrolysis gas chromatography.

[0082] <Preparation of (meth)acrylic rubber particles> (Preparation of three-layered spherical (meth)acrylic rubber particles (1)) Three-layered spherical (meth)acrylic rubber particles (1) manufactured by emulsion polymerization were used. The synthesized (meth)acrylic rubber particles (1) consisted of an innermost layer made of a rigid polymer obtained by polymerizing a monomer composition consisting of 93.8% by mass of methyl methacrylate, 6.0% by mass of methyl acrylate, and 0.2% by mass of allyl methacrylate; an intermediate layer made of an elastic polymer obtained by polymerizing a monomer composition consisting of 81% by mass of butyl acrylate, 17% by mass of styrene, and 2% by mass of allyl methacrylate; and an outermost layer made of a rigid polymer obtained by polymerizing a monomer composition consisting of 94% by mass of methyl methacrylate and 6% by mass of methyl acrylate. The mass ratio of the innermost layer / intermediate layer / outermost layer was 35% by mass / 45% by mass / 20% by mass, and the average particle size of the elastic polymer layer of the intermediate layer was 220 nm.

[0083] (Preparation of two-layered spherical (meth)acrylic rubber particles (2)) Two-layered spherical (meth)acrylic rubber particles (2) manufactured by emulsion polymerization were used. The synthesized (meth)acrylic rubber particles (2) consisted of an inner layer made of a rigid polymer obtained by polymerizing a monomer composition consisting of 67% by mass of methyl methacrylate, 7% by mass of methyl acrylate, 19% by mass of butyl acrylate, and 7% by mass of styrene, and an outer layer made of a flexible polymer obtained by polymerizing a monomer composition consisting of 91% by mass of methyl methacrylate, 7% by mass of methyl acrylate, and 2% by mass of butyl acrylate. The weight ratio of the inner layer / outer layer was 50% by mass / 50% by mass, and the average particle size of the rigid polymer layer was 70 nm.

[0084] <Preparation or preparation of methacrylic resin to form the surface layer> (Preparation of methacrylic resins 1-1 to 1-3 for surface layer formation) As the methacrylic resin 1-1 for forming the surface layer, 50% by mass of the copolymer (A) and 50% by mass of the acrylic rubber particles (1) were melt-kneaded using a 40 mm extruder to prepare the methacrylic resin 1-1 for forming the surface layer. As the methacrylic resin 1-2 for forming the surface layer, 25% by mass of the copolymer (A) and 75% by mass of the acrylic rubber particles (1) were melt-kneaded using a 40 mm extruder to prepare the methacrylic resin 1-2 for forming the surface layer. As the methacrylic resin 1-3 for forming the surface layer, 10% by mass of the copolymer (A) and 90% by mass of the acrylic rubber particles (1) were melt-kneaded using a 40 mm extruder to prepare the methacrylic resin 1-3 for forming the surface layer.

[0085] (Preparation of methacrylic resin 2 for surface layer formation) As the methacrylic resin 2 for forming the surface layer, 50% by mass of Clarity LA4285 (trade name, block copolymer consisting of methyl methacrylate block, n-butyl acrylate block, and methyl methacrylate block, manufactured by Kuraray Co., Ltd.) and 50% by mass of Sumipex EX (trade name, polymethyl methacrylate, manufactured by Sumitomo Chemical Co., Ltd.) were melt-kneaded using a 40 mm extruder to prepare the methacrylic resin 2 for forming the surface layer. (Preparation of methacrylic resin 3 for surface layer formation) Toyo MS600 (trade name, copolymer (MS) of methyl methacrylate and styrene, manufactured by Toyo Styrene Co., Ltd.) was used as the methacrylic resin 3 for surface layer formation. This copolymer (MS) does not contain structural units derived from alkyl acrylate.

[0086] (Preparation of methacrylic resins 4-1 to 4-3 for surface layer formation) As the methacrylic resin 4-1 for forming the surface layer, 50% by mass of the copolymer (A) and 50% by mass of the acrylic rubber particles (2) were melt-kneaded using a 40 mm extruder to prepare the methacrylic resin 4-1 for forming the surface layer. As the methacrylic resin 4-2 for forming the surface layer, 25% by mass of the copolymer (A) and 75% by mass of the acrylic rubber particles (2) were melt-kneaded using a 40 mm extruder to prepare the methacrylic resin 4-2 for forming the surface layer. As the methacrylic resin 4-3 for forming the surface layer, 10% by mass of the copolymer (A) and 90% by mass of the acrylic rubber particles (2) were melt-kneaded using a 40 mm extruder to prepare the methacrylic resin 4-3 for forming the surface layer. Table 1 shows the components of the methacrylic resins used to form each surface layer.

[0087] [Table 1]

[0088] [Preparation of the methacrylic resin that forms the base layer] As the methacrylic resin for forming the base layer, we prepared Sumipex EX (trade name, polymethyl methacrylate, manufactured by Sumitomo Chemical Co., Ltd.).

[0089] [[Examples 1-6 and Comparative Examples 1-3]] [Fabrication of laminated sheets] <Preparation of laminated sheets (laminated sheets for printing)> Using a φ25mm single-screw extruder for the surface layer and a φ40mm single-screw extruder for the base layer, the methacrylic resin for surface layer formation and Sumipex EX for base layer formation, as shown in the "Surface Layer (Printed Layer)" column of Table 2, were co-extruded to produce two types of three-layer sheets, each with a surface layer (printed layer, thickness 0.05mm) laminated on both surfaces of the base layer. Lamination was performed using a feed block located upstream of the T-die. A methacrylic resin for surface layer formation and Sumipex EX for base layer formation were laminated in the feed block, and then passed through the T-die to obtain a sheet-like molded body. The sheet-like molded body exiting the die was cooled using three mirror-polished rolls (upper, middle, and lower) to produce each laminated sheet (printing laminated sheet). The extruder and T-die temperatures were set to 250-260°C, and the surface temperature of all polishing rolls was set to 80°C. The thickness of each layer was adjusted by controlling the extruder's discharge rate. Specifically, the discharge rate of the φ25mm extruder was adjusted so that the surface layer was of a predetermined thickness, and then the discharge rate of the φ40mm extruder was adjusted so that the overall thickness of the laminated sheet was 3mm. In Comparative Example 1, a single-layer sheet was produced by using only a φ40 mm extruder without using a φ25 mm extruder, and adjusting the discharge rate of the methacrylic resin 2 for surface layer formation to a thickness of 3 mm.

[0090] <Preparation of laminated sheets or single-layer sheets (printed laminated sheets)> As described above, UV-curable inks of red, yellow, white, and black were printed on one surface layer (printed layer) of each laminated sheet or single-layer sheet (printable laminated sheet) using a UV inkjet printer under the following printing conditions. The UV-curable inks were then cured to produce laminated sheets or single-layer sheets with a printed layer, as described in Examples 1-6 and Comparative Examples 1-3. The printed pattern was an 8.5cm x 11.5cm rectangle, with solid prints of red, white, yellow, and black arranged side by side on the surface of the surface layer. - Printing conditions - <UV-LEDインクジェットプリンター> UJF-7151 plus, manufactured by Mimaki Engineering Co., Ltd. <UV-curable ink> LH-100 UV-curable ink, manufactured by Mimaki Engineering Co., Ltd.

[0091] [Evaluation] The following evaluations were performed on each of the fabricated laminated sheets or single-layer sheets. The results are shown in Table 2. <Evaluation 1: Appearance evaluation> The appearance of the surface of each of the obtained laminated sheets or single-layer sheets (printing laminated sheets) (the surface on which the 4-color solid printing layer was to be printed) and the surface of each solid printing layer was visually evaluated. The evaluation was such that when the surface of the printing laminated sheet was transparent and could withstand printing, and the surface of each solid printing layer also had good appearance, it was marked as "〇" (qualified), and when there were unacceptable problems with the surface appearance of the printing laminated sheet, it was marked as "×" (unqualified). Since the single-layer sheet of Comparative Example 1 had poor hairline appearance in this evaluation, the following Evaluation 2 and Evaluation 3 were not performed (in Table 2, non-implementation of evaluation is indicated by "-").

[0092] <Evaluation 2: Printing adhesion evaluation> Using a cutter, a 100-lattice pattern of 1 mm square was made on the UV ink printing surface (each of the 4-color solid printing layers) of each laminated sheet (printed laminated sheet). After adhering cellophane tape (registered trademark) to the entire 100 lattices of each solid printing layer, it was strongly peeled off by hand. At this time, the presence or absence of peeling of the UV ink (printing layer) from the surface layer in each solid printing layer was visually determined. The evaluation was such that when no peeling occurred in all 100 lattices in each of the 4-color solid printing layers, it was marked as "〇" (qualified), and when peeling occurred even in 1 liter in the 4-color solid printing layers, it was marked as "×" (unqualified).

[0093] <Evaluation 3: Odor generation evaluation> Small 50mm square pieces were cut from each 300mm square laminated sheet (printing laminated sheet) using laser cutting, and the odor suppression characteristics were qualitatively evaluated based on the degree of styrene odor detected at this time. Laser cutting was performed using a laser processing machine: SEI series DRAGON (product name, manufactured by COMNET). The evaluation was based on whether a styrene odor was detected ("○" - pass) or not ("×" - fail).

[0094] [Table 2]

[0095] The results shown in Table 2 reveal the following: The single-layer sheet of Comparative Example 1, which consisted of a surface layer of methacrylic resin 2 that did not contain rubber particles, exhibited a poor hairline appearance and was therefore unsuitable as a single-layer sheet. This is thought to be partly due to the inclusion of block copolymer in the surface layer. Furthermore, the laminated sheet of Comparative Example 2, which contained random copolymer (A) and had a surface layer made of methacrylic resin (A) that did not contain rubber particles, showed a good appearance but had poor print adhesion. In addition, the laminated sheet of Comparative Example 3, which had a surface layer made of methacrylic resin 3 containing a copolymer of methyl methacrylate and styrene, showed a good appearance but had an odor derived from styrene and poor odor suppression characteristics. In contrast, each laminated sheet of Examples 1 to 6, having a base layer made of methacrylic resin and a surface layer made of methacrylic resins 1-1 to 1-3 and 4-1 to 4-3 containing rubber particles, all exhibited a good appearance and high print adhesion, while also possessing a high degree of odor suppression, to the point where no styrene odor was detected.

Claims

1. A laminated sheet having a base layer made of a methacrylic resin and a surface layer on at least one surface of the base layer, A laminated sheet in which the surface layer is a printable layer made of a methacrylic resin containing a copolymer of alkyl methacrylate and alkyl acrylate and rubber particles.

2. A laminated sheet having a base layer made of a methacrylic resin, a surface layer on at least one surface of the base layer, and a printed layer on the surface of the surface layer, A laminated sheet in which the surface layer is made of a methacrylic resin containing a copolymer of alkyl methacrylate and alkyl acrylate and rubber particles.

3. The laminated sheet according to claim 1 or 2, wherein the copolymer of alkyl methacrylate and alkyl acrylate is a copolymer of methyl methacrylate and butyl acrylate.

4. The laminated sheet according to claim 1 or 2, wherein the methacrylic resin forming the base layer is a polymer of methyl methacrylate.

5. The laminated sheet according to claim 2, wherein the printed layer is a layer printed by one or more of the following printing methods: inkjet printing, UV printing, screen printing, and offset printing.

6. A key holder comprising the laminated sheet described in claim 5.

Images