Multilayer dust cover for head-up display

Abstract

The invention provides a multilayer body and a dust cover for a head-up display using the multilayer body. Wherein the multilayer body has a base material layer and an infrared ray absorbing layer, the infrared ray absorbing layer contains an ultraviolet curable resin and a tungsten oxide, the ultraviolet curable resin contains a component derived from a polyfunctional (meth) acrylate having a weight-average molecular weight of 1000 or more, and the ratio of the tungsten oxide in the infrared ray absorbing layer is 25-50 mass%.

Description

Technical Field

[0001] This invention relates to a multilayer dust cover for head-up displays. In particular, it relates to a multilayer comprising a polycarbonate resin layer and an acrylic resin layer. Background Technology

[0002] In addition to its excellent transparency, polycarbonate resin also has superior processability and impact resistance compared to glass. Furthermore, compared to other plastic materials, there is no need to worry about toxic gases. Therefore, it is widely used in various fields and is also used as a thermoforming material for vacuum forming and air compression forming.

[0003] On the other hand, because polycarbonate resin typically has low surface hardness, molded products made from polycarbonate resin are often easily scratched. Therefore, research has been conducted on techniques that, when polycarbonate resin is formed into a film, form a layer containing acrylic resin or an infrared absorbing layer (protective layer) on the surface to prevent scratches on the product surface. Such multilayers are described in Patent Documents 1 and 2.

[0004] Existing technical documents Patent documents Patent Document 1: International Publication No. 2016 / 060100 Patent Document 2: International Publication No. 2021 / 215435 Summary of the Invention

[0005] The problem that the invention aims to solve Therefore, tungsten oxide is typically added to the infrared absorbing layer as described above to suppress near-infrared transmission. Increasing the tungsten oxide content has been considered to further improve weather resistance. However, the inventors of this invention have discovered that interlayer adhesion (especially the adhesion of the infrared absorbing layer to the substrate) deteriorates depending on the tungsten oxide content.

[0006] The purpose of this invention is to solve the related problems and provide a multilayer with excellent weather resistance and excellent interlayer adhesion, as well as a dust cover for a head-up display using the multilayer.

[0007] Technical solutions for solving the problem After conducting research on the above-mentioned issues, the inventors discovered that by using tungsten oxide in the infrared absorption layer and using a specific resin as an ultraviolet curable resin, the above-mentioned issues can be solved.

[0008] Specifically, the above-mentioned problems were solved through the following solution.

[0009] <1> A multilayer having a substrate layer and an infrared absorbing layer, The aforementioned infrared absorbing layer comprises an ultraviolet-curable resin and tungsten oxide. The aforementioned UV-curable resin contains components derived from polyfunctional (meth)acrylates with a weight-average molecular weight of 1000 or higher. The proportion of the tungsten oxide in the infrared absorption layer is 25-50% by mass.

[0010] <2> according to <1> The multilayer body, wherein the ultraviolet-curable resin contains components derived from polyfunctional urethane (meth)acrylates.

[0011] <3> according to <1> or <2> The multilayer body, wherein the substrate layer comprises an acrylic resin layer and a polycarbonate resin layer, and the infrared absorbing layer is located on the side of the polycarbonate resin layer opposite to the acrylic resin layer.

[0012] <4> according to <1> ~ <3> The multilayer body described in any one of the following statements has a haze value of less than 2.0% as measured according to JIS K 7136.

[0013] <5> according to <1> ~ <4> The multilayer body according to any one of the following methods, wherein the infrared absorbing layer contains 30 to 50% by mass of the tungsten oxide described above.

[0014] <6> according to <1> ~ <5> The multilayer body according to any one of the following methods, wherein the multilayer body further comprises a hard coating layer, wherein the hard coating layer is stacked in the order of infrared absorbing layer, polycarbonate resin layer, acrylic resin layer and hard coating layer.

[0015] <7> according to <6> The multilayer body, wherein the hard coating contains inorganic particles.

[0016] <8> according to <1> ~ <7> The multilayer body according to any one of the following methods, wherein the multilayer body further comprises an anti-reflective layer.

[0017] <9> according to <1> ~ <8> The multilayer body according to any one of the following methods, wherein the multilayer body further comprises a polarizing layer.

[0018] <10> A dust cover for a head-up display, wherein the dust cover for a head-up display includes <1> ~ <9> The multilayer body as described in any one of the following.

[0019] Invention Effects According to the present invention, a multilayer body with excellent weather resistance and excellent interlayer adhesion can be provided, as well as a dust cover for a head-up display using the multilayer body. Attached Figure Description

[0020] Figure 1 This is a cross-sectional schematic diagram illustrating an example of a multilayer body according to the present invention. Detailed Implementation

[0021] The following will describe in detail specific embodiments for implementing the present invention (hereinafter referred to as "this embodiment"). It should be noted that the following embodiments are merely illustrative examples for illustrating the present invention, and the present invention is not limited to these embodiments.

[0022] It should be noted that in this specification, "~" is used to indicate the lower and upper limits, including the values ​​recorded before and after it.

[0023] Unless otherwise stated, all property values ​​and characteristic values ​​in this specification refer to values ​​at 23°C.

[0024] In this specification, unless otherwise stated, the weight-average molecular weight and number-average molecular weight are polystyrene equivalent values ​​determined by GPC (gel permeation chromatography).

[0025] In this specification, "(meth)acrylate" means either or both of acrylate and methacrylate.

[0026] In this specification, "multilayer body" means including articles that form the shape of a film or sheet. "Film" and "sheet" refer to molded articles that are thin relative to their length and width, and are generally flat. Furthermore, "film" and "sheet" in this specification can be single-layered or multi-layered.

[0027] Where the measurement methods described in accordance with the standards given in this instruction manual vary from year to year, the standards based on the date of January 1, 2022 shall be used unless otherwise stated.

[0028] The accompanying diagrams are schematic diagrams, and the scale may differ from the actual figures.

[0029] In this specification, near-infrared light refers to light with a wavelength of 700nm to 2500nm.

[0030] The multilayer body of this embodiment is a multilayer body having a substrate layer and an infrared absorption layer. The infrared absorption layer comprises an ultraviolet-curable resin and tungsten oxide. The ultraviolet-curable resin contains a component derived from a polyfunctional (meth)acrylate with a weight-average molecular weight of 1000 or more. The proportion of the tungsten oxide in the infrared absorption layer is 25 to 50% by mass.

[0031] By adopting this structure, multilayer bodies with excellent weather resistance and excellent interlayer adhesion can be obtained.

[0032] By setting the tungsten oxide content in the infrared absorption layer to 25-50% by mass, weather resistance can be improved. However, both excessive and insufficient tungsten oxide content can lead to inadequate curing and poor adhesion. The resin composition of this embodiment maintains high adhesion by using a polyfunctional (meth)acrylate with a weight-average molecular weight of 1000 or higher. The inventors infer that this is because the larger molecular weight allows for relaxation of shrinkage stress between crosslinking points, thereby reducing curing shrinkage.

[0033] The following describes the details of the invention.

[0034] <Infrared Absorption Layer> The infrared absorbing layer in this embodiment comprises an ultraviolet-curable resin and tungsten oxide. The ultraviolet-curable resin contains components derived from polyfunctional (meth)acrylates with a weight-average molecular weight of 1000 or higher. Typically, the infrared absorbing layer is formed in a cured state of the polyfunctional (meth)acrylate with a weight-average molecular weight of 1000 or higher.

[0035] <<UV-curable resins>> The type of UV-curable resin used in this embodiment is not particularly limited. Known resins can be used, as long as they are polyfunctional (meth)acrylates with a weight average molecular weight of 1000 or more.

[0036] Examples of UV-curable resins include polymers containing polyfunctional (meth)acryloyl groups with a weight average molecular weight of 1000 or more, and polyfunctional urethane (meth)acrylate oligomers with a weight average molecular weight of 1000 or more, with polyfunctional urethane (meth)acrylate oligomers with a weight average molecular weight of 1000 or more being preferred.

[0037] Polymers containing polyfunctional (meth)acryloyl groups with a weight average molecular weight of 1000 or higher can be obtained by, for example, copolymerizing (meth)acrylic acid and glycidyl ether of (meth)acrylic acid to synthesize an epoxy compound having a (meth)acrylic acid ester backbone, and then adding acrylic acid or methacrylic acid to it. Synthetic examples are shown below. Examples of epoxy (meth)acrylates used as polymers containing polyfunctional (meth)acryloyl groups with a weight average molecular weight of 1000 or more include compounds having repeating units as shown in formula (I). In formula (I), m is an alkylene group or a single bond with 1 to 4 carbon atoms, n is an alkyl group or a hydrogen atom with 1 to 4 carbon atoms, p is a single bond or an alkylene group with 1 or 2 carbon atoms, and q is an alkyl group or a hydrogen atom with a total number of 1 to 12 carbon atoms that may contain at least one of the substituents of epoxy, hydroxyl, acryloyl and methacryloyl.

[0038] The multifunctional epoxy (meth)acrylate polymer with a weight average molecular weight of 1000 or more is more preferably a repeating unit containing the following repeating unit, namely, in the above formula (I), m is an alkylene group with 1 or 2 carbon atoms, n is an alkyl group with 1 or 2 carbon atoms, p is a single bond or methylene group, and q is a repeating unit containing at least one of the substituents of glycidyl group, hydroxyl group, and acryloyl group with a total carbon number of 1 to 6 alkyl or hydrogen atoms.

[0039] For example, in the above formula (I), m is methylene, n is methyl, p is a single bond, q is methyl, alkyl with 5 or fewer carbon atoms containing glycidyl (epoxy) group, alkyl with 8 or fewer carbon atoms containing hydroxyl and acryloyl group, etc.

[0040] Specific examples of repeating units contained in multifunctional epoxy (meth)acrylate polymers with a weight average molecular weight of 1000 or more include repeating units shown in formulas (II-a), (II-b), and (II-c). In polyfunctional (meth)acrylate polymers with a weight-average molecular weight of 1000 or more, based on the total molar number of repeating units of formula (II-a), formula (II-b), and formula (II-c), the proportion of repeating units of formula (II-a) is preferably 30 to 85 mol%, more preferably 40 to 80 mol%. The proportion of repeating units of formula (II-b) is preferably 5 to 30 mol%, more preferably 10 to 25 mol%, based on the total molar number described above. Furthermore, the proportion of repeating units of formula (II-c) is preferably 10 to 40 mol%, more preferably 10 to 35 mol%, based on the total molar number described above.

[0041] Furthermore, the molar ratio of the repeating unit in formula (II-a), the repeating unit in formula (II-b), and the repeating unit in formula (II-c) is preferably 4.5 to 5.5: 1.5 to 2.5: 2.5 to 3.5, for example, 5: 2: 3.

[0042] Polymers containing polyfunctional (meth)acryloyl groups with a weight average molecular weight of 1000 or higher are readily available and commercially available. Examples include SMP-220A (manufactured by Kyoeisha Chemical Co., Ltd.), SMP-250A (manufactured by Kyoeisha Chemical Co., Ltd.), SMP-360A (manufactured by Kyoeisha Chemical Co., Ltd.), SMP-550A (manufactured by Kyoeisha Chemical Co., Ltd.), HA7975 (manufactured by Showa Denko Materials Co., Ltd.), HA7975D (manufactured by Showa Denko Materials Co., Ltd.), RA-4101 (manufactured by Negami Kogyo Co., Ltd.), 8KX-078 (manufactured by Taisei Fine Chemicals Co., Ltd.), and 8KX-212 (manufactured by Taisei Fine Chemicals Co., Ltd.).

[0043] Examples of polyfunctional urethane (meth)acrylate oligomers with a weight average molecular weight of 1000 or more include the urethane esterification reaction products of (meth)acrylate monomers having at least one (meth)acryloyloxy and hydroxyl group per molecule with polyisocyanates, and the urethane esterification reaction products of isocyanate compounds obtained by reacting polyols with polyisocyanates with (meth)acrylate monomers having at least one (meth)acryloyloxy and hydroxyl group per molecule.

[0044] Examples of (meth)acrylate monomers used in carbamate reactions that have at least one (meth)acryloyloxy and one hydroxyl group in each molecule include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, glyceryl di(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol penta(meth)acrylate.

[0045] Examples of polyisocyanates used in carbamate reactions include hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, phenyl diisocyanate, diisocyanates obtained by hydrogenation of aromatic isocyanates (e.g., hydrogenated toluene diisocyanate, hydrogenated phenyl diisocyanate, etc.), triphenylmethane triisocyanate, dimethylene triphenyl triisocyanate, etc., or polyisocyanates obtained by polymerizing diisocyanates.

[0046] Polyols used in urethane esterification reactions typically include, in addition to aromatic, aliphatic, and alicyclic polyols, polyester polyols and polyether polyols. Examples of aliphatic and alicyclic polyols include 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, ethylene glycol, propylene glycol, trimethylolethane, trimethylolpropane, dimethylolheptane, dimethylolpropionic acid, dimethylolbutyric acid, glycerol, and hydrogenated bisphenol A.

[0047] Examples of polyester polyols include products obtained through the dehydration condensation reaction of the aforementioned polyols with polycarboxylic acids. Specific compounds of polycarboxylic acids include succinic acid, adipic acid, maleic acid, trimellitic acid, hexahydrophthalic acid, phthalic acid, isophthalic acid, and terephthalic acid. These polycarboxylic acids can also be acid anhydrides. Furthermore, in addition to polyalkylene glycols, examples of polyether polyols include polyoxyalkylene modified polyols obtained by reacting the aforementioned polyols or phenols with epoxides.

[0048] Furthermore, multifunctional polyester (meth)acrylate oligomers are obtained through a dehydration condensation reaction of (meth)acrylic acid, polycarboxylic acids, and polyols. Examples of polycarboxylic acids used in the dehydration condensation reaction include succinic acid, adipic acid, maleic acid, itaconic acid, trimellitic acid, pyromellitic acid, hexahydrophthalic acid, phthalic acid, isophthalic acid, and terephthalic acid. These polycarboxylic acids can also be acid anhydrides. Examples of polyols used in the dehydration condensation reaction include 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, dimethylolheptan, dimethylolpropionic acid, dimethylolbutyric acid, trimethylolpropane, bis(trimethylolpropane), pentaerythritol, and dipentaerythritol.

[0049] Polyfunctional epoxy (meth)acrylate oligomers with a weight average molecular weight of 1000 or higher are obtained through the addition reaction of polyglycidyl ethers with (meth)acrylic acid. Examples of polyglycidyl ethers include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and bisphenol A diglycidyl ether.

[0050] As polyfunctional urethane (meth)acrylates, commercially available products can also be used. Examples include UN-3320HA, UN-3320HC, UN-906S, UN-901T, UN-952, UN-904, UN-905, UN-3320HS, H-575 (all manufactured by Negami Kogyo Co., Ltd.), U-6LPA, UA-1100H (all manufactured by Shin-Nakamura Chemical Co., Ltd.), EBECRYL5129, EBECRYL4738, EBECRYL4740, EBECRYL4513, EBECRYL8254, EBECRYL220, and EBECRYL8701 (all manufactured by Daicel Allnex Co., Ltd.).

[0051] The double bond equivalent of the UV-curable resin is 400 g / mol or less, preferably 360 g / mol or less, and more preferably 250 g / mol or less. Setting the value above or above this lower limit often improves the hardness of the resulting infrared absorption layer. A lower limit of 100 g / mol or more is preferred.

[0052] The weight-average molecular weight of the UV-curable resin is 1000 or more, preferably 2000 or more, and more preferably 3000 or more. By setting it above the lower limit value, curing shrinkage can be suppressed more effectively. Furthermore, the weight-average molecular weight of the UV-curable resin is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. By setting it below the upper limit value, coating is easier.

[0053] The weight-average molecular weight of the UV-curable resin in this embodiment is the value obtained by the following method.

[0054] The weight-average molecular weight of the UV-curable resin can be measured based on the description in paragraphs

[0061] to

[0064] of Japanese Patent Application Publication No. 2007-179018. Details of the measurement method are shown below.

[0055] First, a calibration curve showing the relationship between elution time and the molecular weight of the UV-curable resin was prepared using the Universal Calibration Method with polystyrene as the standard polymer. Then, the elution curve (chromatogram) of the UV-curable resin was measured under the same conditions as the calibration curve. The weight-average molecular weight (Mw) was then calculated based on the elution time (molecular weight) and the peak area (number of molecules) at that elution time. The weight-average molecular weight is expressed by equation (A), where Ni represents the number of molecules with a molecular weight Mi.

[0056] Mw=Σ(NiMi2 ) / Σ(NiMi)(A) Device: Waters Corporation, Alliance Chromatographic columns: Shodex K-805L (two columns) manufactured by Showa Denko Co., Ltd. Detector: UV detector, wavelength 254nm Eluent: Chloroform.

[0057] In addition to the above, UV-curable resins may also contain monofunctional (meth)acrylate alkyl ester monomers and / or polyfunctional (meth)acrylate alkyl ester monomers. Furthermore, they may also contain styrene monomers, styrene oligomers, cyclic anhydrides, N-substituted maleimide compounds, and lactone ring compounds, etc.

[0058] In this embodiment, the content of the component derived from polyfunctional (meth)acrylates with a weight-average molecular weight of 1000 or more in the infrared absorption layer is preferably 45% by mass or more, more preferably 50% by mass or more, and preferably 75% by mass or less, more preferably 70% by mass or less. By setting the content above the lower limit, multilayers with higher toughness and higher hardness can often be obtained. Furthermore, by setting the content below the upper limit, a coating film with a good balance between light transmittance and infrared absorption can be obtained.

[0059] The infrared absorbing layer of this embodiment may contain only one type of UV-curable resin and / or a component derived from a polyfunctional (meth)acrylate with a weight average molecular weight of 1000 or more, or it may contain two or more components. When two or more components are contained, it is preferable that the total amount is within the above-mentioned range.

[0060] <<Tungsten Oxide>> The infrared absorbing layer in this embodiment contains tungsten oxide.

[0061] The colorant used in this embodiment includes tungsten oxide. By including tungsten oxide, the multilayer can block near-infrared light, thus making it more suitable for use as a dust cover for head-up displays.

[0062] Cesium tungsten oxide (CWO) is preferred as the tungsten oxide.

[0063] In this embodiment, the tungsten oxide content in the infrared absorption layer is preferably 25% by mass or more, more preferably 28% by mass or more, further preferably 30% by mass or more, even more preferably 35% by mass or more, and can be 40% by mass or more, and 50% by mass or less, preferably 47% by mass or less, more preferably 45% by mass or less, and can be 44% by mass or less. By setting it above the above-mentioned lower limit value, the infrared absorption effect can often be further improved. By setting it below the above-mentioned upper limit value, excellent transparency can be maintained.

[0064] The infrared absorbing layer of this embodiment may contain only one type of tungsten oxide, or it may contain two or more types. When it contains two or more types, the total amount is preferably within the above-mentioned range.

[0065] The infrared absorbing layer in this embodiment is also preferably substantially free of pigments (or even colorants) other than tungsten oxide. "Substantially free" means that the content of pigments (and thus colorants) other than tungsten oxide in the infrared absorbing layer is preferably less than 10% by mass of the tungsten oxide content, more preferably less than 5% by mass, and even more preferably less than 1% by mass.

[0066] <<Photopolymerization Initiators>> In this embodiment, the infrared absorbing layer may further contain a photopolymerization initiator. The photopolymerization initiator can be any known photopolymerization initiator, as long as it can cure the UV-curable resin.

[0067] As a photopolymerization initiator, a photoradical initiator that can break bonds and generate free radicals under the action of visible light or ultraviolet light with a wavelength shorter than 450 nm is preferred. Examples include photopolymerization initiators having an acylphosphine oxide skeleton, an α-hydroxy ketone skeleton, a benzyl dimethyl ketal skeleton, an amino ketone skeleton, a benzophenone skeleton, or a triazine skeleton containing trichloromethyl. Photopolymerization initiators having an acylphosphine oxide skeleton and / or an α-hydroxy ketone skeleton are preferred.

[0068] Specific examples of photopolymerization initiators include benzophenone, thioxanone, benzyl dimethyl ketal, α-hydroxy ketone, α-hydroxyalkyl phenyl ketone, α-amino ketone, α-aminoalkyl phenyl ketone, monoacylphosphine oxide, diacylphosphine oxide, hydroxybenzophenone, aminobenzophenone, dicene, oxime ester, and oxyphenyl acetate.

[0069] In addition to the examples mentioned above, as polymerization initiators, references can also be made to the descriptions in International Publication No. 2023 / 095664, paragraph

[0039] ; International Publication No. 2022 / 102736, paragraphs

[0234] to

[0238] ; Japanese Patent Application Publication No. 2010-106268, paragraph

[0135] ; Japanese Patent Application Publication No. 2009-13115, paragraphs

[0018] to

[0025] ; and Japanese Patent Application Publication No. 2005-154312, paragraphs

[0018] to

[0025] , the contents of which are incorporated herein by reference.

[0070] The content of the photopolymerization initiator contained in the infrared absorption layer of this embodiment is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 1.5% by mass or more, and preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 4% by mass or less. By setting it above the above lower limit value, sufficient curability can be exhibited. By setting it below the above upper limit value, storage stability and aging degradation can often be further improved.

[0071] The infrared absorbing layer of this embodiment may contain only one photopolymerization initiator, or it may contain two or more. When it contains two or more, the total amount is preferably within the above-mentioned range.

[0072] <<Other Ingredients>> In addition to the components mentioned above, the infrared absorbing layer may also contain leveling agents, ultraviolet absorbers, light stabilizers, heat stabilizers, flame retardants, flame retardant additives, colorants, antistatic agents, fluorescent whitening agents, antifogging agents, flow improvers, plasticizers, dispersants, antibacterial agents, anti-blocking agents, impact resistance improvers, slip resistance improvers, color improvers, acid scavengers, etc. One or more of these components may be used.

[0073] The total amount of these other components in the infrared absorption layer is preferably 0% or more and less than 10% by mass, more preferably 0% or more and less than 5% by mass, or may be 0% or more and less than 1% by mass.

[0074] <<Light Stabilizers>> As light stabilizers, hindered amine light stabilizers such as bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate, bis(1-undecalkoxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate, 1,2,2,6,6-13-pentamethyl-4-piperidinyl methacrylate, 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, bis[2,2,6,6-tetramethyl-1-(octoxy)piperidin-4-yl] sebacate, and 2-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-2-butylmalonic acid bis[1,2,2,6,6-pentamethyl-4-piperidinyl] ester can be used.

[0075] The content ratio of light stabilizer in the infrared absorption layer is preferably 0-5% by mass, more preferably 0-3% by mass, and even more preferably 0-1% by mass. By setting it below the above upper limit, the UV-curable resin can often be cured more effectively.

[0076] Examples of flame retardants include halogen-based flame retardants and phosphorus-based flame retardants. Examples of phosphorus-based flame retardants include aromatic phosphate compounds, phenanthrene phosphate compounds, phosphonate metal salts, ammonium polyphosphate, melamine polyphosphate, phosphate ester amides, and red phosphorus. For further information on flame retardants, please refer to paragraphs

[0054] to

[0082] of Japanese Patent Application Publication No. 2022-104214 and paragraphs

[0052] to

[0077] of Japanese Patent No. 7021724, the contents of which are incorporated herein by reference.

[0077] In the infrared absorption layer, the total amount of ultraviolet-curable resin, photopolymerization initiator, colorant and light stabilizer preferably accounts for more than 90% by mass, more preferably more than 95% by mass, and even more preferably more than 97% by mass.

[0078] In addition, the total amount of UV-curable resin, photopolymerization initiator, colorant and light stabilizer in the infrared absorption layer will not exceed 100% by mass.

[0079] The thickness of the infrared absorption layer is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 1.5 μm or more, and preferably 10 μm or less, more preferably 8 μm or less, even more preferably 5 μm or less. By setting it below the above upper limit value, curing defects will not occur during UV curing. By setting it above the above lower limit value, the effect as an infrared absorption layer can be more effectively demonstrated.

[0080] <Layer Composition of Multi-layer Structures> Next, the layer structure of the multilayer body in this embodiment will be described.

[0081] The multilayer in this embodiment has a substrate layer and an infrared absorbing layer. The substrate layer preferably comprises an acrylic resin layer and a polycarbonate resin layer, more preferably, both acrylic resin and polycarbonate resin layers, and the infrared absorbing layer is located on the side of the polycarbonate resin layer opposite to the acrylic resin layer. By adopting this configuration, a multilayer with superior weather resistance can be obtained.

[0082] The following is for reference Figure 1 This section describes a preferred example of a multilayer structure in this embodiment. It goes without saying that the multilayer structure in this embodiment is not limited to... Figure 1 The method described above.

[0083] Figure 1 This is a cross-sectional schematic diagram illustrating an example of a multilayer structure according to this embodiment. 1 represents the multilayer structure, 2 represents the acrylic resin layer, 3 represents the polycarbonate resin layer, and 4 represents the infrared absorbing layer. In the multilayer structure 1 of this embodiment, the infrared absorbing layer 4 is located on the side of the polycarbonate resin layer 3 opposite to the acrylic resin layer 2. This configuration improves the weather resistance of the multilayer structure. It should be noted that in this specification, the acrylic resin layer 2 and the polycarbonate resin layer 3 are sometimes referred to together as the substrate. Furthermore, it is self-evident that the substrate may also include other layers without departing from the spirit of the invention. Details of these other layers will be described later.

[0084] The infrared absorption layer 4 can be the outermost layer of the multilayer 1. By providing the infrared absorption layer 4, the surface hardness of the multilayer can often be further improved. In the multilayer 1 of this embodiment, it is preferable to stack the acrylic resin layer 2, the polycarbonate resin layer 3, and the infrared absorption layer 4 in that order, with the infrared absorption layer 4 located on the surface of the polycarbonate resin layer 3. By placing the infrared absorption layer 2 on the surface of the polycarbonate resin layer 3, the formability of the infrared absorption layer 2 (the coatability of the composition for forming the infrared absorption layer) can be further improved. As long as the multilayer of this embodiment stacks the acrylic resin layer 2, the polycarbonate resin layer 3, and the infrared absorption layer 4 in the above order, other layers may be present without departing from the spirit of this embodiment, but it is preferable that there are no other layers, that is, the above three layers are adjacent to each other.

[0085] Furthermore, the multilayer in this embodiment can be a flame-retardant substrate in which at least one of the acrylic resin layer and the polycarbonate resin layer contains 0.01 to 0.80% by mass of metal sulfonate. By using such a flame-retardant substrate, it can also be applied to applications requiring flame retardancy. These details will be explained later.

[0086] The thickness (total thickness) of the multilayer is preferably, but not particularly limited to, 30 μm or more, more preferably 100 μm or more. Furthermore, the thickness of the multilayer is preferably 10,000 μm or less, more preferably 5,000 μm or less, and even more preferably 2,000 μm or less, but can be 1,000 μm or less, or 500 μm or less.

[0087] The multilayer structure in this embodiment preferably exhibits excellent infrared shielding performance.

[0088] Specifically, the transmittance of the multilayer at a wavelength of 1000 nm in this embodiment is preferably 60% or less, more preferably 40% or less, further preferably 25% or less, even more preferably 20% or less, and still more preferably 10% or less. Although no specific lower limit is specified, it is actually greater than 0%.

[0089] The multilayer in this embodiment is preferably highly transparent.

[0090] Specifically, it is even more preferable that the haze of the multilayer body, as measured according to JIS K7136, is 3.0% or less, more preferably 2.0% or less, further preferably 1.5% or less, and even more preferably 1.0% or less. Although the lower limit is preferably 0% or more, in practice it exceeds 0%.

[0091] In addition, specifically, the full-spectrum transmittance of the multilayer in this embodiment is preferably 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more. Although the ideal value is 100%, 90% or less is sufficient to meet the required performance.

[0092] The multilayer structure in this embodiment is preferably characterized by excellent weather resistance.

[0093] Specifically, the haze of the multilayer material, measured according to JIS K7136 after weathering resistance testing, is more preferably 10.0% or less, further preferably 8.0% or less, even more preferably 5.0% or less, and still more preferably 4.5% or less. Although the lower limit is preferably 0% or more, in practice it exceeds 0%.

[0094] The multilayer body of this embodiment may also have flame retardancy. Specifically, the multilayer body preferably meets the C rating in the FMVSS test (it is burning before reaching the B mark, but the burning rate is less than 102 mm / min), and more preferably meets the B rating in the FMVSS test (it self-extinguishes within 51 mm of the A mark (and within 60 seconds).

[0095] The transmittance at a wavelength of 1000 nm, the full-spectrum transmittance, the haze after the heat resistance test, and the FMVSS test were measured according to the description in the following embodiments.

[0096] The multilayer structure of this embodiment preferably further includes a hard coating layer. Preferably, the hard coating layer is present on at least one side of the multilayer structure, more preferably on the side of the acrylic resin layer opposite to the polycarbonate resin layer. The hard coating layer can be the outermost surface layer of the multilayer structure. By providing a hard coating layer, the surface hardness of the multilayer structure can often be further improved. In the multilayer structure of this embodiment, the hard coating layer is preferably stacked in the order of infrared absorption layer, polycarbonate resin layer, acrylic resin layer, and hard coating layer. In the multilayer structure of this embodiment, the hard coating layer is preferably provided on the surface of the acrylic resin layer. By providing a hard coating layer on the surface of the acrylic resin layer, the coatability of the hard coating layer can be further improved.

[0097] The hard coating layer included in the multilayer of this embodiment may be a layer with a surface hardness higher than that of the polycarbonate resin layer. By including such a hard coating layer, the surface hardness of the multilayer and even the molded article can be improved.

[0098] The thickness of the hard coating is preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 2 μm or more, even more preferably 2.5 μm or more, and still more preferably 3 μm or more. By setting the thickness above or below the above-mentioned lower limit, the overall pencil hardness of the multilayer body can often be further improved by using the hard coating. The upper limit of the thickness of the hard coating is preferably 20 μm or less, more preferably 15 μm or less, further preferably 12 μm or less, even more preferably 10 μm or less, and still more preferably 8 μm or less, and can be 5 μm or less. By setting the thickness below the above-mentioned upper limit, the flame retardancy can often be further improved.

[0099] The hard coating is preferably a layer obtained by applying a hard coating material that can be cured by heat curing or active energy rays and then curing it.

[0100] As an example of a coating that uses active energy rays for curing, a resin composition comprising one or more monofunctional or polyfunctional (preferably 2- to 10-functional) (meth)acrylate monomers or oligomers can be cited. A resin composition comprising monofunctional or polyfunctional (preferably 2- to 10-functional) urethane (meth)acrylate oligomers is preferred. In these resin compositions, a photopolymerization initiator is preferably added as a curing catalyst.

[0101] In addition, examples of thermosetting resin coatings include polyorganosiloxane-based and cross-linked acrylic coatings. These resin compositions are also commercially available as hard coating agents for acrylic resins or polycarbonate resin films or sheets, and can be appropriately selected based on their compatibility with the coating production line.

[0102] As a hard coating, reference can be made to the descriptions in Japanese Patent Application Publication No. 2013-020130, paragraphs

[0045] to

[0055] , Japanese Patent Application Publication No. 2018-103518, paragraphs

[0073] to

[0076] , and Japanese Patent Application Publication No. 2017-213771, paragraphs

[0062] to

[0082] , the contents of which are incorporated herein by reference.

[0103] The hard coating preferably includes, in addition to the above-mentioned components, inorganic particles, organic pigments, ultraviolet absorbers, light stabilizers, heat stabilizers, flame retardants, flame retardant additives, colorants, antistatic agents, fluorescent whitening agents, antifogging agents, flow improvers, plasticizers, dispersants, antibacterial agents, antiblocking agents, impact resistance improvers, slip resistance improvers, hue improvers, acid scavengers, etc., and more preferably, inorganic particles. These components may be used individually or in combination.

[0104] Examples of inorganic particles are preferably nanoparticles composed of metals and / or metal compounds. Examples include gold, silver, copper, platinum, palladium, nickel, cobalt, iron, manganese, silicon, titanium, zirconium, tungsten, molybdenum, chromium, zinc, aluminum, and composite metals composed of two or more of these metals. Furthermore, metal compounds are preferably metal oxides, metal carbides, metal borides, metal carbonates, zeolites, clays, and their complexes, such as iron oxide, silicon dioxide, zirconium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, cobalt oxide, nickel oxide, cerium oxide, copper oxide, zinc oxide, tin oxide, antimony oxide, titanium dioxide, aluminum oxide, indium tin oxide (ITO), cesium tungsten oxide (CWO), and mixtures thereof; silicon dioxide is more preferred.

[0105] The aforementioned inorganic particles may or may not undergo surface treatment. Surface treatment is preferred. The surface treatment agent is preferably a silane coupling agent.

[0106] The average particle size (D50) of the aforementioned inorganic particles is preferably 5 nm or more, more preferably 7 nm or more, and preferably 30 nm or less, more preferably 20 nm or less. Setting the particle size above the aforementioned lower limit often improves flame retardancy. Setting the particle size below the aforementioned upper limit often improves transparency.

[0107] In this embodiment, the content of inorganic particles in the hard coating is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less. By setting the content above the lower limit, the flame retardancy can often be further improved. By setting the content below the upper limit, the crack suppression effect during heat resistance testing can often be further improved.

[0108] The aforementioned hard coating may contain only one type of inorganic particle or two or more types of inorganic particles. When containing two or more types, the total amount is preferably within the aforementioned range.

[0109] Examples of flame retardants include halogen-based flame retardants and phosphorus-based flame retardants. Examples of phosphorus-based flame retardants include aromatic phosphate compounds, phenanthrene phosphate compounds, phosphonate metal salts, ammonium polyphosphate, melamine polyphosphate, phosphate ester amides, and red phosphorus. For further information on flame retardants, please refer to paragraphs

[0054] to

[0082] of Japanese Patent Application Publication No. 2022-104214 and paragraphs

[0052] to

[0077] of Japanese Patent No. 7021724, the contents of which are incorporated herein by reference.

[0110] In addition to the above-described structure, the multilayer body of this embodiment may also have other layers. Examples include bonding layers, adhesive layers, antifouling layers, antireflective layers, and polarizing layers, with an antireflective layer being preferred.

[0111] The anti-reflective layer is typically preferably located on the opposite side of the polycarbonate resin layer of the infrared absorbing layer (e.g., Figure 1 (of) 4 on the lower side.

[0112] Details of the anti-reflective layer can be found in Japanese Patent Application Publication No. 2023-114940, paragraphs

[0062] to

[0083] , Japanese Patent Application Publication No. 2022-174051, paragraphs

[0013] to

[0041] , and Japanese Patent Application Publication No. 2021-081596, paragraphs

[0043] to

[0046] , the contents of which are incorporated herein by reference.

[0113] The polarizing layer is typically preferably located on the opposite side of the polycarbonate resin layer of the infrared absorbing layer (e.g., Figure 1 (of) 4 on the lower side.

[0114] Details of the polarizing layer can be found in Japanese Patent Application Publication No. 2008-105225, paragraphs

[0022] to

[0029] , Japanese Patent Application Publication No. 2020-52406, paragraphs

[0011] to

[0021] , and Japanese Patent Application Publication No. 2023-13533, paragraphs

[0014] to

[0037] , the contents of which are incorporated herein by reference.

[0115] Furthermore, the multilayer can also undergo one or more of the following treatments on at least one surface: fingerprint resistance treatment, anti-glare treatment, weather resistance treatment, antistatic treatment, anti-fouling treatment, and anti-blocking treatment. In addition, anti-blocking treatment refers to a treatment that allows the films to be easily peeled off even if they adhere to each other, and examples include adding anti-blocking agents and creating textures on the surface of the multilayer.

[0116] <<Polycarbonate resin layer>> The polycarbonate resin layer in this embodiment contains polycarbonate resin.

[0117] There are no particular limitations on the polycarbonate resin, and various polycarbonate resins can be used, as long as they include the -[O-R-OCO]- structural unit (R is a hydrocarbon group, such as aliphatic group, aromatic group, or both aliphatic group and aromatic group, and has a straight chain structure or a branched chain structure) in the main molecular chain. Aromatic polycarbonate resins are preferred.

[0118] In this embodiment, the polycarbonate resin preferably comprises a bisphenol-type polycarbonate resin. A bisphenol-type polycarbonate resin refers to a polycarbonate resin in which 80 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more of the structural units constituting the polycarbonate resin are carbonate structural units derived from bisphenol and / or its derivatives. Bisphenol and / or its derivatives are preferably bisphenol A, bisphenol AP, bisphenol C, bisphenol BP, or derivatives of these bisphenols, more preferably bisphenol A, bisphenol AP, or derivatives of both, and even more preferably bisphenol A or its derivatives.

[0119] Bisphenol type polycarbonate resin is preferably bisphenol A type polycarbonate resin.

[0120] The molecular weight of polycarbonate resin is typically calculated by converting the viscosity of the solution measured at 25°C using dichloromethane as a solvent. Preferably, but not particularly limited to, it is 20,000 or more, more preferably 22,000 or more. Furthermore, the aforementioned viscosity-average molecular weight is preferably 35,000 or less, more preferably 32,000 or less, and even more preferably 30,000 or less. By setting the aforementioned viscosity-average molecular weight to the lower limit or above, the strength of the obtained flat molded body can be improved. In addition, by setting the aforementioned viscosity-average molecular weight to the upper limit or below, the molding and processing performance is often improved.

[0121] Wherein, viscosity-average molecular weight [Mv] refers to the intrinsic viscosity [η] (unit: dL / g) at 25°C using dichloromethane as a solvent and an Ubbelohde viscometer, based on the Schnell viscosity formula, i.e., η = 1.23 × 10⁻⁶. ﹣4 Mv 0.83 The calculated value. Furthermore, intrinsic viscosity [η] refers to the specific viscosity [η] measured at various solution concentrations [C] (g / dL). sp ], and the value is calculated according to the following formula. It should be noted that, in this embodiment, two or more polycarbonate resins with different viscosity-average molecular weights can be mixed and used. In this case, the viscosity-average molecular weight of the mixture is used.

[0122] The initial glass transition temperature (Tg) of the polycarbonate resin used in this embodiment is preferably 160°C or less, more preferably 155°C or less, even more preferably 154°C or less, even more preferably 153°C or less, even more preferably 152°C or less, and even more preferably 151°C or less. Furthermore, the initial glass transition temperature (Tg) of the polycarbonate resin used in this embodiment is, for example, 140°C or more, and further preferably 143°C or more, 145°C or more, 147°C or more, or 148°C or more.

[0123] The glass transition temperature was measured according to the description in paragraph

[0056] of Japanese Patent Application Publication No. 2022-080270.

[0124] Furthermore, as long as the main idea of ​​this embodiment is not deviated from, the details of the polycarbonate resin can also be found in paragraphs

[0011] to

[0020] of Japanese Patent Application Publication No. 2012-144604 and paragraphs

[0014] to

[0035] of Japanese Patent Application Publication No. 2019-002023, which are incorporated herein by reference.

[0125] The content of polycarbonate resin in the polycarbonate resin layer of this embodiment is preferably 90% by mass or more, more preferably 92% by mass or more, further preferably 94% by mass or more, even more preferably 96% by mass or more, and even more preferably 97% by mass or more, and can be 98% by mass or more. The upper limit can be 100% by mass.

[0126] In this embodiment, when the polycarbonate resin layer contains two or more types of polycarbonate resin, it is preferable that their total amount is within the above-mentioned range.

[0127] The polycarbonate resin layer in this embodiment may also contain sulfonate metal salts. Sulfonate metal salts are typically used as flame retardants in polycarbonate resins.

[0128] The sulfonate metal salt is preferably an alkali metal salt. Lithium, sodium, potassium, and rubidium are preferred as the alkali metal constituting the alkali metal salt, with sodium and potassium being more preferred. Additionally, the sulfonate metal salt may also contain fluorine atoms.

[0129] The molecular weight of the sulfonate metal salt used in this embodiment is preferably 100-900, more preferably 100-500.

[0130] Specific examples of the sulfonate metal salts used in this embodiment are shown below. It goes without saying that the sulfonate metal salts used in this embodiment are not limited to these. The content of sulfonate metal salt in the polycarbonate resin layer is preferably 0.01 to 0.80% by mass, more preferably 0.7% by mass or less, even more preferably 0.6% by mass or less, even more preferably 0.5% by mass or less, and even more preferably 0.4% by mass or less. Depending on the application, it may be less than 0.1% by mass or less than 0.05% by mass.

[0131] The polycarbonate resin layer of this embodiment may contain only one sulfonate metal salt, or it may contain two or more sulfonate metal salts. When it contains two or more, the total amount is preferably within the above-mentioned range.

[0132] The polycarbonate resin layer in this embodiment may also contain flame retardants other than sulfonate metal salts, such as phosphorus-based flame retardants like condensed phosphate esters and phosphazenes, organosilicon-based flame retardants like polyorganosiloxanes, and halogen-based flame retardants like Br-modified polycarbonate oligomers. Specific examples of phosphorus-based flame retardants include condensed phosphate esters such as resorcinol bis(diphenyl phosphate) (RDP), resorcinol bis(xylyl phosphate) (RDX), bisphenol A bis(diphenyl phosphate) (BDP), and biphenyl bis(diphenyl phosphate), as well as linear phenoxyphosphazenes and cyclic phenoxyphosphazenes. The content of the flame retardant in the polycarbonate resin layer is preferably 0.3 to 20% by mass, more preferably 0.5 to 10% by mass.

[0133] The polycarbonate resin layer of this embodiment may also contain ultraviolet absorbers such as triazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers. The content of the ultraviolet absorber in the polycarbonate resin layer is preferably 0.1 to 5.0% by mass, more preferably 0.5 to 2.0% by mass.

[0134] In addition to the components described above, the polycarbonate resin layer of this embodiment may also contain antioxidants, release agents, flame retardants, heat stabilizers, colorants, antistatic agents, fluorescent whitening agents, antifogging agents, flow improvers, plasticizers, dispersants, antibacterial agents, antiblocking agents, impact resistance improvers, slip resistance improvers, hue improvers, acid scavengers, etc. One or more of these components may be used. The preferred content of the above components, in total, is 0-5% by mass of the polycarbonate resin layer; more preferably, 0-3% by mass; further preferably, 0-1% by mass; even more preferably, 0-0.5% by mass; still more preferably, 0-0.3% by mass; and still more preferably, 0-0.1% by mass.

[0135] Examples of antioxidants include phenolic antioxidants, amine antioxidants, phosphorus-based antioxidants, and thioether antioxidants. In this embodiment, phosphorus-based antioxidants and phenolic antioxidants (more preferably hindered phenolic antioxidants), and even more preferably phosphorus-based antioxidants, are preferred.

[0136] The phosphorus-based antioxidant is preferably a phosphite antioxidant, and more preferably a phosphite compound represented by formula (1) or (2).

[0137] (1) In equation (1), R 11 and R 12 Each can be independently represented as an alkyl group with 1 to 30 carbon atoms or an aryl group with 6 to 30 carbon atoms. In equation (2), R 13 ~R 17 Each can be independently represented by a hydrogen atom, an aryl group with 6 to 20 carbon atoms, or an alkyl group with 1 to 20 carbon atoms.

[0138] In the above equation (1), R 11 R 12 Each alkyl group represented is preferably a straight-chain or branched alkyl group having 1 to 10 carbon atoms. In R 11 R 12 When the aryl group is aryl, it is preferably represented by any one of the following formulas (1-a), (1-b), and (1-c). The "*" in the formula indicates the bonding position. In equation (1-a), R A Each of the following independently represents an alkyl group having 1 to 10 carbon atoms. In formula (1-b), R B Each can be used independently to represent an alkyl group having 1 to 10 carbon atoms.

[0139] As a hindered phenolic antioxidant, reference can be made to paragraphs

[0063] of Japanese Patent Application Publication No. 2018-090677 and

[0076] of Japanese Patent Application Publication No. 2018-188496, the contents of which are incorporated herein by reference.

[0140] In addition to the compounds mentioned above, antioxidants can be found in paragraphs

[0057] to

[0061] of Japanese Patent Application Publication No. 2017-031313, the contents of which are incorporated herein by reference.

[0141] The antioxidant content is preferably 0.001 parts by weight or more, more preferably 0.005 parts by weight or more, further preferably 0.010 parts by weight or more, and even more preferably 0.050 parts by weight or more, relative to 100 parts by weight of the polycarbonate resin layer. As for the upper limit of the antioxidant content, relative to 100 parts by weight of the polycarbonate resin layer, it is preferably 0.500 parts by weight or less, more preferably 0.300 parts by weight or less, further preferably 0.200 parts by weight or less, even more preferably 0.150 parts by weight or less, even more preferably 0.100 parts by weight or less, and particularly more preferably 0.080 parts by weight or less.

[0142] Antioxidants may be used in single or multiple forms. When using multiple forms, it is preferable that their combined amount is within the range described above.

[0143] Next, we will explain the release agents that can be included in the polycarbonate resin layer.

[0144] Types of mold release agents can be listed, but are not specifically limited to, aliphatic carboxylic acids, esters of aliphatic carboxylic acids and alcohols, aliphatic hydrocarbon compounds with a number average molecular weight of 200 to 15,000, polyethers with a number average molecular weight of 100 to 5,000, and polysiloxane-based silicone oils.

[0145] Details of the release agent can be found in paragraphs

[0035] to

[0039] of International Publication No. 2015 / 190162, the contents of which are incorporated herein by reference.

[0146] The content of the release agent relative to 100 parts by weight of the polycarbonate resin layer is preferably 0.001 parts by weight or more, more preferably 0.005 parts by weight or more, further preferably 0.010 parts by weight or more, and even more preferably 0.050 parts by weight or more. As an upper limit, it is preferably 0.5 parts by weight or less, more preferably 0.3 parts by weight or less, and even more preferably 0.1 parts by weight or less.

[0147] A single mold release agent may be used, or two or more may be used. When using two or more, it is preferable that their total amount is within the range described above.

[0148] The thickness of the polycarbonate resin layer is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 150 μm or more. Setting it above the above lower limit not only makes it easier to mold, but also often improves flame retardancy. The upper limit of the polycarbonate resin layer thickness is preferably 1000 μm or less, more preferably 750 μm or less, and even more preferably 500 μm or less.

[0149] <<Acrylic Resin Layer>> The acrylic resin layer in this embodiment contains acrylic resin.

[0150] Furthermore, the acrylic resin layer can be a single layer or multiple layers, but a single layer is preferred.

[0151] The acrylic resin layer in this embodiment comprises acrylic resin as described above.

[0152] An example of an acrylic resin is preferably a polymer in which the content of (meth)acrylate alkyl ester units (preferably alkyl methacrylate units) in all structural units is 50% by mass or more (preferably 90% by mass or more), and more preferably a polymer in which the content of (meth)acrylate methyl acrylate units (preferably methyl methacrylate units) in all structural units is 50% by mass or more (preferably 90% by mass or more). Other structural units besides (meth)acrylate alkyl ester units can be cited as examples, such as other (meth)acrylate units, styrene units, cyclic anhydride units, N-substituted maleimide units, and lactone ring units.

[0153] The acrylic resin layer may be formed solely of acrylic resin, or it may contain other thermoplastic resins in addition to acrylic resin.

[0154] As other thermoplastic resins, it is more preferable to include at least one thermoplastic resin selected from styrene-based resins, fluorinated resins such as polyvinylidene fluoride, and aromatic polyether resins such as polyphenylene ether, and even more preferably, it includes styrene-based resins.

[0155] An example of an acrylic resin layer is a layer in which 90% or more (preferably 95% or more, more preferably 97% or more, and even more preferably 98% or more) is formed of acrylic resin.

[0156] Another example of an acrylic resin is a layer formed of the above-mentioned acrylic resin and other thermoplastic resins (preferably styrene-based resins) comprising 90% or more by mass (preferably 95% or more by mass, more preferably 97% or more by mass, and even more preferably 98% or more by mass).

[0157] The weight-average molecular weight of the acrylic resin is preferably, but not particularly limited to, 10,000 or more, more preferably 30,000 or more, further preferably 50,000 or more, even more preferably 60,000 or more, and still more preferably 70,000 or more. Furthermore, the weight-average molecular weight of the acrylic resin is preferably 250,000 or less, more preferably 200,000 or less, further preferably 150,000 or less, even more preferably 100,000 or less, and still even more preferably 90,000 or less.

[0158] The glass transition temperature of the acrylic resin layer used in this embodiment is preferably 80°C or higher, more preferably 90°C or higher, even more preferably 95°C or higher, even more preferably 100°C or higher, and still more preferably 105°C or higher. There is no particular upper limit, but in practice it is, for example, 200°C or lower.

[0159] The glass transition temperature was measured according to the description in paragraph

[0056] of Japanese Patent Application Publication No. 2022-080270.

[0160] In addition to the above-mentioned components, the acrylic resin layer may also contain inorganic particles, antioxidants, release agents, ultraviolet absorbers, heat stabilizers, flame retardants, flame retardant additives, colorants, antistatic agents, fluorescent whitening agents, antifogging agents, flow improvers, plasticizers, dispersants, antibacterial agents, anti-blocking agents, impact resistance improvers, slip resistance improvers, color improvers, acid scavengers, etc. One or more of these components may be used. The preferred content of the above components, in total, is 0-5% by mass of the acrylic resin layer; more preferably 0-3% by mass; further preferably 0-1% by mass; even more preferably 0-0.5% by mass; still more preferably 0-0.3% by mass; and even more preferably 0-0.1% by mass.

[0161] <<Ultraviolet Absorbers>> As described above, in order to prevent ultraviolet degradation of the polycarbonate resin layer, acrylic resin layer and infrared absorption layer in this embodiment, the acrylic resin layer in this embodiment may contain an ultraviolet absorber.

[0162] Examples of usable ultraviolet absorbers include benzotriazole, benzophenone, phenyl salicylate, benzoxazine, malonate, triazine, and polymeric ultraviolet absorbers with the above compounds added as side groups.

[0163] Examples of benzotriazole-based ultraviolet absorbers include 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2-methylenebis[4-(1,1,3,3-tetramethylenebutyl)-6-(2H-benzotriazole-2-yl)phenol], and 2-(2H-benzotriazole-2-yl)phenol. Examples include triazol-2-yl)-6-(1-methyl-1-phenethyl)-4-(1,1,3,3-tetramethylbutyl)phenol; examples of benzophenone-based ultraviolet absorbers include 2-hydroxy-4-octoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, and 2,2-dihydroxy-4,4'-dimethoxybenzophenone.

[0164] In addition, examples of phenyl salicylate-based ultraviolet absorbers include p-tert-butyl salicylate. Examples of benzoxazine-based ultraviolet absorbers include 2,2'-(1,4-phenylene)bis[4H-3,1-benzoxazine-4-one].

[0165] Examples of malonate-based ultraviolet absorbers include dimethyl [(4-methoxyphenyl)-methylene]malonate.

[0166] Examples of triazine-based ultraviolet absorbers include 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, and 2,6-di(4-biphenyl)-4-(2-hydroxy-4-(2-ethylhexyl)oxy Examples of triazine include (-phenylene)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-dodecanoyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-benzyloxyphenyl)-1,3,5-triazine, and 2,4-diphenyl-6-(2-hydroxy-4-butoxyethoxy)-1,3,5-triazine, but these are not limited to these examples; they also include commonly available ultraviolet absorbers.

[0167] Examples of polymeric ultraviolet absorbers include polymers with hydroxybenzophenone or hydroxybenzotriazole structures, as well as substituted products in which some hydrogen atoms are replaced by alkyl groups. One example of a polymeric ultraviolet absorber is UVA-633L (2-hydroxy-4-(methacryloyloxyethoxy)benzophenone) methyl methacrylate copolymer, commercially manufactured by BASF.

[0168] As described above, the acrylic resin layer in this embodiment may contain an antioxidant. Examples of antioxidants include phenolic antioxidants, amine antioxidants, phosphorus-based antioxidants, and thioether antioxidants. In this embodiment, a phosphorus-based antioxidant is also preferred.

[0169] The phosphorus-based antioxidant is preferably a phosphite antioxidant, and more preferably a phosphite compound represented by formula (1) or (2).

[0170] (1) In equation (1), R 11 and R 12 Each can be independently represented as an alkyl group with 1 to 30 carbon atoms or an aryl group with 6 to 30 carbon atoms. In equation (2), R 13 ~R 17 Each can be independently represented by a hydrogen atom, an aryl group with 6 to 20 carbon atoms, or an alkyl group with 1 to 20 carbon atoms.

[0171] In the above equation (1), R 11 R 12 The alkyl groups represented are preferably each a straight-chain or branched alkyl group having 1 to 10 carbon atoms. In R 11 R 12 When the aryl group is aryl, it is preferably represented by any one of the following formulas (1-a), (1-b), and (1-c). The "*" in the formula indicates the bonding position. Relative to 100 parts by weight of the acrylic resin layer, the content of the antioxidant is preferably 0.001 parts by weight or more, more preferably 0.005 parts by weight or more, and even more preferably 0.010 parts by weight or more. As for the upper limit of the antioxidant content, relative to 100 parts by weight of the acrylic resin layer, it is preferably 0.500 parts by weight or less, more preferably 0.300 parts by weight or less, even more preferably 0.200 parts by weight or less, even more preferably 0.150 parts by weight or less, even more preferably 0.100 parts by weight or less, and even more preferably 0.080 parts by weight or less.

[0172] Antioxidants may be used in single or multiple forms. When using multiple forms, it is preferable that their combined amount is within the range described above.

[0173] <<Mold Release Agent>> As described above, the acrylic resin layer in this embodiment may contain a release agent. Examples of release agents include, but are not particularly limited to, aliphatic carboxylic acids, esters of aliphatic carboxylic acids and alcohols, aliphatic hydrocarbon compounds with a number average molecular weight of 200 to 15,000, polyethers with a number average molecular weight of 100 to 5,000, and polysiloxane-based silicone oils.

[0174] Details of the release agent can be found in paragraphs

[0035] to

[0039] of International Publication No. 2015 / 190162, the contents of which are incorporated herein by reference.

[0175] The content of the release agent relative to 100 parts by weight of the acrylic resin layer is preferably 0.001 parts by weight or more, more preferably 0.005 parts by weight or more, further preferably 0.010 parts by weight or more, and even more preferably 0.050 parts by weight or more. As an upper limit, it is preferably 0.5 parts by weight or less, more preferably 0.3 parts by weight or less, and even more preferably 0.2 parts by weight or less.

[0176] A single mold release agent may be used, or two or more may be used. When using two or more, it is preferable that their total amount is within the range described above.

[0177] As described above, the acrylic resin layer in this embodiment may contain inorganic particles. Examples of inorganic particles include silica particles, alumina particles, zirconium oxide particles, silicon particles, silver particles, and glass particles.

[0178] As described above, the acrylic resin layer in this embodiment may contain a flame retardant. Examples of flame retardants that can be included in the acrylic resin layer include phosphorus-based flame retardants and sulfonate metal salts, with phosphorus-based flame retardants being preferred.

[0179] Examples of phosphorus-based flame retardants include aromatic phosphate compounds, phosphazene compounds, phosphazene compounds, phosphonate metal salts, ammonium polyphosphate, melamine polyphosphate, phosphate ester amides, and red phosphorus, with aromatic phosphate compounds, phosphazene compounds, and phosphazene compounds being preferred.

[0180] Examples of aromatic phosphate compounds include resorcinol diphenyl phosphate, hydroquinone diphenyl phosphate, bisphenol A diphenyl phosphate, and biphenyl diphenyl phosphate. Commercially available examples include PX-202, CR-741, PX-200, and PX-201 manufactured by Daihachi Chemical Industry Co., Ltd., and FP-500, FP-600, FP-700, and PFR manufactured by ADEKA Corporation.

[0181] Examples of aromatic phosphate compounds include cyclic phenoxyphosphazenes and their derivatives. Commercially available examples include Rabitle FP-110 manufactured by Fushimi Pharmaceutical Co., Ltd.

[0182] Phosphenanthrene compounds are phosphorus-based flame retardants with at least one phosphenanthrene skeleton in the molecule. Commercially available products include HCA, HCA-HQ, BCA, SANKO-220, and M-Ester manufactured by Sanko Corporation.

[0183] Phosphonic acid metal salts are phosphonates and / or diphosphonates and / or polymers thereof. Examples of such salts include salts of calcium, aluminum, and zinc. Commercially available phosphonic acid metal salts include Clariant's "Exolit" (registered trademark) OP1230 and OP1240 from Japan.

[0184] Phosphate ester amides are aromatic amide flame retardants containing phosphorus and nitrogen atoms. Among commercially available phosphate ester amides, SP-703 manufactured by Shikoku Kasei Corporation is preferred.

[0185] Examples of ammonium polyphosphates include ammonium polyphosphate, melamine-modified ammonium polyphosphate, and carbamoyl ammonium polyphosphate. Examples of melamine polyphosphates include melamine phosphate, melamine pyrophosphate, and phosphates formed with melamine, melamine, and melamine. MPP-A manufactured by Sanwa Chemical Co., Ltd., PMP-100 manufactured by Nissan Chemical Co., Ltd., and PMP-200 manufactured by Nissan Chemical Co., Ltd. are preferred.

[0186] When the acrylic resin layer contains a flame retardant (phosphorus-based flame retardant, sulfonate metal salt, or other flame retardant), its content relative to 100 parts by weight of the acrylic resin layer is preferably 1 part by weight or more, more preferably 2 parts by weight or more, further preferably 5 parts by weight or more, and even more preferably 7 parts by weight or more. Furthermore, relative to 100 parts by weight of the acrylic resin layer, the upper limit of the content of the aforementioned flame retardant is preferably 25 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 15 parts by weight or less.

[0187] The acrylic resin layer may contain only one flame retardant or two or more. When containing two or more flame retardants, the total amount is preferably within the range described above.

[0188] The thickness of the acrylic resin layer is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 150 μm or more. By setting it above the above lower limit, it is not only easier to achieve molding, but also often the hardness can be improved. In addition, the upper limit of the acrylic resin layer thickness is preferably 1000 μm or less, more preferably 750 μm or less, and even more preferably 500 μm or less.

[0189] <Manufacturing Methods of Multilayer Materials> The multilayer body of this embodiment can be manufactured according to known methods.

[0190] The multilayer body of this embodiment can be manufactured, for example, by using a main extruder for extruding a polycarbonate resin layer forming composition and an auxiliary extruder for extruding an acrylic resin layer forming composition, melting and extruding the resin according to the conditions of each resin used, guiding it to a die, stacking it inside the die and forming it into a sheet, or stacking it after forming it into a sheet, to form a substrate. Then, an infrared absorption layer forming composition is coated on one side of the polycarbonate resin layer of the substrate and cured.

[0191] The multilayer body of this embodiment can be used directly or can be processed, especially by heating, to form a molded product.

[0192] <Application> The multilayer body of this embodiment can be applied to optical components, appearance design products, anti-reflective molded bodies, etc.

[0193] The multilayer body of this embodiment can be applied to components of display devices, electrical and electronic equipment, OA (office automation) equipment, portable information terminals, mechanical parts, home appliances, vehicle parts, various containers, lighting equipment, etc. It is particularly suitable for housings of various displays, electrical and electronic equipment, OA equipment, portable information terminals, and home appliances; surface films of lighting equipment and vehicle parts (especially automotive interior parts); optical materials of smartphones and touchscreens; and optical discs. The multilayer body of this embodiment is especially preferred for use as a dust cover for head-up displays.

[0194] Example The following examples illustrate the present invention in more detail. The materials, dosages, ratios, processing contents, and processing steps shown in the following examples can be appropriately modified as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0195] When the measuring instruments used in the embodiments are difficult to obtain due to reasons such as production stoppage, other devices with equivalent performance can be used for measurement.

[0196] 1. Raw materials SMP-220A: A polymer containing acryloyl groups, with a solid content of 50% by mass, a weight-average molecular weight of 20,000, and an acrylic acid equivalent of 220 g / mol, manufactured by Kyoei Chemical Co., Ltd.

[0197] UN-901T: Carbamate acrylate, solid content 80% by mass, weight average molecular weight 4000, functional groups 9, manufactured by Nejou Kogyo Co., Ltd. PE3A: Multifunctional acrylate, solid component 100% by mass, molecular weight 298, functional group number 3, manufactured by Kyoei Chemical Co., Ltd.

[0198] PE4A: Multifunctional acrylate, solid component 100% by mass, molecular weight 352, number of functional groups 4, manufactured by Kyoei Chemical Co., Ltd.

[0199] YMF-02A: CWO (cesium tungsten oxide) dispersion, CWO content 18.5% by mass, manufactured by Sumitomo Metal Mining Co., Ltd.

[0200] BYK-UV3575: Silicone-based leveling agent, manufactured by BYK (BYK Chemical Company).

[0201] PGM: Propylene Glycol Monomethyl Ether Omnirad 819: Acylphosphine oxide photopolymerization initiator, solid component 100% by mass, manufactured by IGM RESINS BV.

[0202] DF02U: A double-layer film consisting of a polycarbonate resin layer and an acrylic resin layer, manufactured by Mitsubishi Gas Chemical Co., Ltd., with a thickness of 0.375 mm.

[0203] E-2000F: A polycarbonate resin obtained by interfacial polymerization using bisphenol A as the starting material (Mitsubishi Gas Chemical Co., Ltd. E-2000F, viscosity-average molecular weight: 27000, Tg: 150℃).

[0204] KSS-FR: Manufactured by Arichem, KSS-FR stands for potassium diphenyl sulfone-3-sulfonate.

[0205] NATS: Manufactured by Tokyo Chemical Industry Co., Ltd., NATS stands for Sodium p-toluenesulfonate.

[0206] F-114P: Manufactured by DIC Corporation, F-114P is potassium perfluorobutane sulfonate.

[0207] 2112: Tris(2,4-di-tert-butylphenyl) phosphite (phosphorus antioxidant, manufactured by ADEKA Corporation, adekastab 2112).

[0208] S-100A: Glyceryl monostearate (RIKEMAL S-100A manufactured by Riken Vitamin Co., Ltd.).

[0209] 80HD: Made by Asahi Kasei Co., Ltd., polymethylmethacrylate.

[0210] 2. Examples 1-9, Comparative Examples 1-4 Fabrication of Multilayers (Coating of Infrared Absorption Layers) Regarding the composition for forming the infrared absorption layer, the components shown in Tables 1 and 2 are used. In Tables 1 and 2, the proportions of each component represent the amount of solid component (parts by mass).

[0211] The infrared absorption layer forming composition obtained above was applied to the coated surfaces of the substrates shown in Tables 1 and 2 using a doctor blade coater. The coated infrared absorption layer forming composition was dried in an oven at 80°C for 3 minutes and then cured under nitrogen atmosphere using a Heraeus UV irradiation system until the cumulative light intensity reached 500 mJ / cm². 2 (UV illuminance meter manufactured by ORC, measuring wavelength 360nm).

[0212] <Full Spectrum Transmittance (%)> The full-spectrum transmittance of the multilayer was measured using the "HM-150" manufactured by the Murakami Color Technology Research Institute in Japan.

[0213] <Transmittance at 1000nm wavelength (%)> The transmittance of the multilayer at a wavelength of 1000 nm was measured.

[0214] The transmittance was measured using a Hitachi High Technology Co., Ltd. U-4000 spectrophotometer.

[0215] <Haze (%) of multilayers after weathering resistance test> The acrylic resin layer of the multilayer was used as the irradiation surface, and light was irradiated under the following conditions.

[0216] Device: SUV-W161, manufactured by Iwasaki Electric Co., Ltd.

[0217] Light source: metal halide lamp.

[0218] Test environment: 85℃ (temperature of black panel), 50%RH.

[0219] Illuminance: 100mW / cm 2 (365nm).

[0220] Irradiation cycle: 24 hours (continuous irradiation).

[0221] Irradiation time: 200 hours.

[0222] The haze of the multilayer was evaluated according to JIS K 7136:2000.

[0223] Haze was measured using the "HM-150" manufactured by the Murakami Color Technology Research Institute in Japan. Units are expressed as "%".

[0224] <Adhesion> The adhesion between the infrared absorption layer and the substrate was evaluated according to the evaluation method of JIS K5600-5-6:1999. The adhesion ratings of the examples and comparative examples with the evaluation result classified as "0" were rated as "A", and the adhesion ratings of those with the evaluation results classified as "1" to "5" were rated as "C".

[0225] <Heat resistance test> The fabricated laminate was heated in an oven at a temperature of 120 °C for 5 minutes, and the degree of crack generation was evaluated as described below. The evaluation was performed by visual observation, confirmed by 5 experts, and judged according to the majority decision principle.

[0226] A: No crack generation was observed B: A small amount of cracks were observed C: Obvious cracks were observed <FMVSS test> For the above-mentioned multilayer body obtained, using a FMVSS No.302 flammability test device, starting from the right end of the test piece (350 mm × 100 mm × 0.375 mm), it was brought into contact with a 38-mm-high combustion flame for 15 seconds, and the combustion speed within a 254-mm combustion distance between the markings was measured. The measurement was carried out without a heat-resistant metal support wire (wire) in the test fixture, and the evaluation was performed as described below.

[0227] A: The test piece was non-combustible or self-extinguished before reaching the A marking B: Self-extinguished within 51 mm from the A marking (and within 60 seconds) of the combustion distance C: Although it was burning before reaching the B marking, the combustion speed was 102 mm / min or less D: It was burning before reaching the B marking, and the combustion speed was faster than 102 mm / min.

[0228] [Table 1] [Table 2] 3. Examples 10 to 12 <Manufacture of flame-retardant substrate> A resin composition (pellets) for forming a polycarbonate resin layer (PC layer) and a resin composition (pellets) for forming an acrylic resin layer were manufactured according to the following method.

[0229] The above components were weighed according to the addition amounts described in Table 3 (all components in Table 3 are expressed as mass %). Then, after mixing with a tumbler for 15 minutes, the mixture was melt-blended using a twin-screw extruder (TEX30α, manufactured by Nippon Steel Corporation) with a 32mm screw diameter and equipped with a vent, and the resulting material was cut into granules. It should be noted that the polycarbonate resin layer forming resin composition (granules) was melt-blended at a temperature that was adjusted according to the resin viscosity between 260 and 300°C, while the acrylic resin layer forming resin composition (granules) was melt-blended at 260°C.

[0230] A multi-layer extrusion unit was used, comprising a single-screw extruder with a shaft diameter of 32 mm, a single-screw extruder with a shaft diameter of 65 mm, a feeding unit connected to all extruders, and a 650 mm wide T-die connected to the feeding unit, to form flame-retardant substrates. The acrylic resin layer of each flame-retardant substrate shown in the table was introduced into the single-screw extruder with a shaft diameter of 32 mm, and extrusion was performed at a barrel temperature of 240°C and a discharge rate of 0.3–6.4 kg / h. Furthermore, the polycarbonate resin layer forming resin composition (granules) of each flame-retardant substrate shown in Table 1 was continuously introduced into the single-screw extruder with a shaft diameter of 65 mm, and extrusion was performed at a discharge rate of 17.4–23.5 kg / h, with the barrel temperature varying between 250°C and 290°C depending on the resin viscosity. The feeding unit connected to all extruders was equipped with two types of double-layer distributors (distribution pins) for extrusion and stacking. The material is extruded into sheets using a T-shaped die connected to the front end of the extruder. Simultaneously, it is mirror-transferred using three mirror-polishing rollers with temperatures of 120°C, 120°C, and 140°C from the upstream side, while being cooled to obtain various flame-retardant substrates.

[0231] Fabrication of Multilayers (Coating of Infrared Absorption Layers) The same infrared absorption layer forming composition as in Example 9 was applied to the surface of the polycarbonate resin layer of the substrate layer obtained as described above. The coating was dried in an oven at 80°C for 3 minutes and then cured under nitrogen atmosphere using a Heraeus UV irradiation system until the cumulative light intensity reached 500 mJ / cm². 2 (UV illuminance meter manufactured by ORC, measuring wavelength 360nm) <Evaluation> Similar to Example 1, the full-spectrum transmittance, transmittance at a wavelength of 1000 nm, haze after weathering test, adhesion, heat resistance test, and FMVSS were evaluated.

[0232] [Table 3] 4. Examples 13-16 Fabrication of Multilayers with Infrared Absorption Layers A multilayer with an infrared absorption layer was fabricated using the same method as in Example 9 or Example 10.

[0233] <Hard coating on the opposite side> A hard coating is applied to the side of the multilayer body fabricated as described above, opposite to the side with the infrared absorption layer.

[0234] In Table 4, a and b represent the resin compositions used for the hard coating, which are described below.

[0235] a: Fujikura Chemicals HO3313U-10 b: A resin composition for hard coating prepared by mixing 67.5% by mass of Genjo Industrial's UN-3320HC, 29.0% by mass of silica particles surface-treated with 3-acryloyloxypropyltrimethoxysilane, 2.5% by mass of photopolymerization initiator, and 1% by mass of leveling agent.

[0236] The above-mentioned hard coating resin composition was applied to the outermost surface (the surface of the acrylic resin layer) of the multilayer, opposite to the side containing the infrared absorbing layer, using a doctor blade coater. The applied hard coating resin composition was dried in an oven at 80°C for 3 minutes and then cured under nitrogen atmosphere using a Heraeus UV irradiation system until the cumulative light intensity reached 500 mJ / cm². 2 (Using an ORC UV illuminometer, measuring wavelength 360nm), a hard coating with a thickness of 4.5μm was formed.

[0237] <Evaluation> Similar to Example 1, the full-spectrum transmittance, transmittance at a wavelength of 1000 nm, haze after weathering test, adhesion, heat resistance test, and FMVSS were evaluated.

[0238] [Table 4] In the table above, HC layer coating describes the composition of the hard coating layer on the surface of the acrylic resin layer, and a and b represent the composition of the resin composition used for the hard coating layer.

[0239] As shown in Tables 1 to 4 above, the multilayer of the present invention exhibits low haze and excellent interlayer adhesion after weathering tests (Examples 1 to 16). Furthermore, the multilayer of the present invention has high full-spectrum transmittance, low near-infrared transmittance, and excellent heat resistance. Moreover, when a flame-retardant substrate is used (Examples 10 to 12, 15, and 16), flame retardancy is also excellent.

[0240] Symbol Explanation 1: Multi-layered body 2: Acrylic resin layer 3: Polycarbonate resin layer 4: Infrared absorption layer.

Claims

1. A multilayer comprising a substrate layer and an infrared absorbing layer, characterized in that: The infrared absorption layer comprises an ultraviolet-curable resin and tungsten oxide. The UV-curable resin contains components derived from polyfunctional (meth)acrylates with a weight-average molecular weight of 1000 or higher. The proportion of tungsten oxide in the infrared absorption layer is 25-50% by mass.

2. The multilayer body according to claim 1, characterized in that: The UV-curable resin contains components derived from polyfunctional urethane (meth)acrylates.

3. The multilayer body according to claim 1 or 2, characterized in that: The substrate layer comprises an acrylic resin layer and a polycarbonate resin layer. The infrared absorbing layer is located on the side of the polycarbonate resin layer opposite to the acrylic resin layer.

4. The multilayer body according to any one of claims 1 to 3, characterized in that: The haze value measured according to JIS K 7136 is below 2.0%.

5. The multilayer body according to any one of claims 1 to 4, characterized in that: The infrared absorption layer contains 30-50% by mass of the tungsten oxide.

6. The multilayer body according to any one of claims 1 to 5, characterized in that: The multilayer body also has a hard coating. The hard coating layer is stacked in the following order: infrared absorption layer, polycarbonate resin layer, acrylic resin layer, and hard coating layer.

7. The multilayer body according to claim 6, characterized in that: The hard coating contains inorganic particles.

8. The multilayer body according to any one of claims 1 to 7, characterized in that: The multilayer body also has an anti-reflective layer.

9. The multilayer body according to any one of claims 1 to 8, characterized in that: The multilayer body also has a polarizing layer.

10. A dust cover for a head-up display, characterized in that: The dust cover for the head-up display comprises a multilayer body as described in any one of claims 1 to 9.

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