JP2008188875A - Multilayer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer sheet excellent in heat resistance and transparency.
A polyester resin excluding a polyester resin (A) and at least one layer comprising a polyester resin (A) comprising a unit derived from a diol having a cyclic acetal skeleton and a unit derived from a dicarboxylic acid having a naphthalene skeleton; A multilayer sheet comprising at least one layer composed of at least one resin selected from the group consisting of acrylic resin, polystyrene resin, polycarbonate resin and methyl methacrylate-styrene copolymer.
[Selection figure] None

Description

  The present invention includes a layer composed of a polyester resin (A) having a unit derived from a diol having a cyclic acetal skeleton and a unit derived from a dicarboxylic acid having a naphthalene skeleton, and a layer composed of a resin other than the polyester resin (A). The present invention relates to a multilayer sheet excellent in transparency and heat resistance.

  Sheets made of transparent resin are used for exterior applications such as showcases, outdoor signage, carports, transparent containers, heat-resistant transparent beverage cups, side dishes trays, containers that require reheating, food applications such as lids, etc. Resins such as polycarbonate, polystyrene, polymethyl methacrylate, methyl methacrylate-styrene copolymer have been used as the base material. However, since polycarbonate has inferior weather resistance, rigidity and low surface hardness, and polystyrene, polymethyl methacrylate, and methyl methacrylate-styrene copolymer have inferior impact resistance, any resin can be used. There were limitations.

  On the other hand, polyethylene terephthalate (hereinafter sometimes referred to as “PET”) is a resin balanced in transparency, mechanical performance, solvent resistance, aroma retention, weather resistance, recyclability, etc. The demand for transparent sheets is expanding. In particular, the demand for food applications is increasing due to its excellent environmental suitability, such as no generation of environmental hormones, no generation of dioxins during incineration, and recyclability. However, since PET does not necessarily have good heat resistance, it cannot be used in fields where high heat resistance is required.

で表される３，９−ビス（１，１−ジメチル−２−ヒドロキシエチル）−２，４，８，１０−テトラオキサスピロ〔５．５〕ウンデカン及びジメチルテレフタレートをチタン化合物触媒の存在下で重合せしめて１８０〜２２０℃で溶融するポリエステル樹脂が得られたことが記載されている。また同公報中には、開示されているポリエステル樹脂は、ガラス転移点が高く耐熱性に優れるとの記載がなされている。 As heat-resistant polyesters, Examples 9 and 10 of Patent Document 1 include ethylene glycol and the following structural formula (5):

3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane and dimethyl terephthalate in the presence of a titanium compound catalyst It is described that a polyester resin that has been polymerized and melted at 180 to 220 ° C. was obtained. In the publication, it is described that the disclosed polyester resin has a high glass transition point and excellent heat resistance.

  When the present inventors polymerized the polyester resin disclosed in the US patent, the polymerization proceeded with gelation, and a polyester resin suitable for molding such as extrusion could not be obtained.

The inventors of the present invention disclosed in Patent Document 2 a PET copolymerized with 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane. A multilayer sheet containing at least one layer is disclosed. However, the multilayer sheet disclosed in the publication does not always have sufficient heat resistance.
US Pat. No. 2,945,008 JP 2003-182014 A

  In view of the above situation, an object of the present invention is to provide a multilayer sheet excellent in heat resistance and transparency.

  As a result of intensive studies, the present inventors have found that at least one layer composed of a polyester resin (A) comprising a unit derived from a diol having a cyclic acetal skeleton and a unit derived from a dicarboxylic acid having a naphthalene skeleton, and a polyester resin A multilayer sheet comprising at least one layer composed of at least one resin selected from the group consisting of polyester resin, acrylic resin, polystyrene resin, polycarbonate resin and methyl methacrylate-styrene copolymer excluding (A) is heat resistant and transparent. And the present invention has been found.

  That is, the present invention is a unit in which 1 to 80 mol% in the diol unit is derived from a diol having a cyclic acetal skeleton, and 1 to 100 mol% in a dicarboxylic acid unit is a unit derived from a dicarboxylic acid having a naphthalene skeleton. It is selected from the group consisting of at least one layer comprising a certain polyester resin (A) and a polyester resin (B) other than the polyester resin (A), an acrylic resin, a polystyrene resin, a polycarbonate resin and a methyl methacrylate-styrene copolymer. In addition, the present invention relates to a multilayer sheet including at least one layer made of at least one resin.

  The multilayer sheet of the present invention is excellent in heat resistance and transparency, and can be used as a material for exterior use, food use, etc., and the industrial significance of the present invention is great.

または一般式（２）：

で表される化合物に由来する単位をジオール単位中１〜８０モル％有する。一般式（１）と（２）において、Ｒ^１およびＲ^２はそれぞれ独立して、炭素数が１〜１０の脂肪族炭化水素基、炭素数が３〜１０の脂環式炭化水素基、及び炭素数が６〜１０の芳香族炭化水素基からなる群から選ばれる炭化水素基を表す。Ｒ^１およびＲ^２は、メチレン基、エチレン基、プロピレン基、ブチレン基、又はこれらの構造異性体が好ましい。これらの構造異性体としては、例えば、イソプロピレン基、イソブチレン基が例示される。Ｒ^３は炭素数が１〜１０の脂肪族炭化水素基、炭素数が３〜１０の脂環式炭化水素基、及び炭素数が６〜１０の芳香族炭化水素基からなる群から選ばれる炭化水素基を表す。Ｒ^３は、メチル基、エチル基、プロピル基、ブチル基、又はこれらの構造異性体が好ましい。これらの構造異性体としては、例えば、イソプロピル基、イソブチル基が例示される。一般式（１）及び（２）の化合物は１種類を単独で用いても良いし、２種類以上を使用しても良い。一般式（１）及び（２）の化合物としては、３，９−ビス（１，１−ジメチル−２−ヒドロキシエチル）−２，４，８，１０−テトラオキサスピロ〔５．５〕ウンデカン、５−メチロール−５−エチル−２−（１，１−ジメチル−２−ヒドロキシエチル）−１，３−ジオキサン等が特に好ましい。 The multilayer sheet of the present invention will be described in detail below.
First, the polyester resin (A) used in the present invention will be described. The polyester resin (A) has the general formula (1):

Or general formula (2):

1 to 80 mol% of diol units derived from a compound represented by In the general formulas (1) and (2), R ¹ and R ² are each independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and This represents a hydrocarbon group selected from the group consisting of aromatic hydrocarbon groups having 6 to 10 carbon atoms. R ¹ and R ² are preferably a methylene group, an ethylene group, a propylene group, a butylene group, or a structural isomer thereof. Examples of these structural isomers include an isopropylene group and an isobutylene group. R ³ is a carbon selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and an aromatic hydrocarbon group having 6 to 10 carbon atoms. Represents a hydrogen group. R ³ is preferably a methyl group, an ethyl group, a propyl group, a butyl group, or a structural isomer thereof. Examples of these structural isomers include isopropyl group and isobutyl group. As for the compounds of the general formulas (1) and (2), one type may be used alone, or two or more types may be used. Examples of the compounds of the general formulas (1) and (2) include 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 5-methylol-5-ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1,3-dioxane and the like are particularly preferable.

  The proportion of units derived from the diol having a cyclic acetal skeleton in the polyester resin (A) is 1 to 80 mol%, preferably 5 to 60 mol%, more preferably 10 to 45 mol% in the diol unit. . Having a unit derived from a diol having a cyclic acetal skeleton is preferable because the glass transition temperature of the polyester resin (A) is increased and the heat resistance of the multilayer sheet of the present invention is improved.

  Moreover, the polyester resin (A) has 20 to 99 mol% of units derived from a diol having no cyclic acetal skeleton in the diol unit. The unit derived from a diol having no cyclic acetal skeleton is not particularly limited, but ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, Aliphatic diols such as propylene glycol and neopentyl glycol; 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-decahydronaphthalene diethanol, 1,3-decahydronaphthalene diethanol, 1 , 4-Decahydronaphthalene diethanol, 1,5-decahydronaphthalene diethanol, 1,6-decahydronaphthalene diethanol, 2,7-decahydronaphthalene diethanol, tetralin dimethanol, norbornane dimethanol, Cycloaliphatic diols such as cyclodecane dimethanol and pentacyclododecane dimethanol; polyether compounds such as polyethylene glycol, polypropylene glycol and polybutylene glycol; 4,4 ′-(1-methylethylidene) bisphenol, methylenebisphenol ( Bisphenols such as bisphenol F), 4,4′-cyclohexylidene bisphenol (bisphenol Z), 4,4′-sulfonylbisphenol (bisphenol S); alkylene oxide adducts of the bisphenols; hydroquinone, resorcin, 4,4 Aromatic dihydroxy compounds such as' -dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenylbenzophenone; and the aromatic dihydroxy Units derived from diols such as alkylene oxide adducts of compounds can be exemplified. In consideration of the mechanical strength and heat resistance of the polyester resin (A), units derived from ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, etc. are preferred, and units derived from ethylene glycol are preferred. Particularly preferred. In addition, the polyester resin (A) may contain one type or two or more types of units derived from a diol having no cyclic acetal skeleton.

  The polyester resin (A) used in the present invention is a unit derived from a dicarboxylic acid having 1 to 100 mol% of the dicarboxylic acid unit having a naphthalene skeleton. The dicarboxylic acid unit having a naphthalene skeleton is not particularly limited. For example, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2, It is preferably a unit derived from 7-naphthalenedicarboxylic acid, particularly preferably a unit derived from 2,6-naphthalenedicarboxylic acid. The polyester resin (A) may contain one type of unit derived from dicarboxylic acid having a naphthalene skeleton or two or more types. 1-100 mol% in the dicarboxylic acid unit is a unit derived from a dicarboxylic acid having a naphthalene skeleton, the glass transition temperature of the polyester resin (A) is increased, and the heat resistance of the multilayer sheet of the present invention is improved. Therefore, it is preferable.

  The polyester resin (A) used in the present invention is a unit derived from dicarboxylic acid in which 0 to 99 mol% of the dicarboxylic acid unit does not have a naphthalene skeleton, and is not particularly limited, but succinic acid, glutaric acid, adipic acid, Aliphatic dicarboxylic acids such as pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid, decanedicarboxylic acid, norbornanedicarboxylic acid, tricyclodecanedicarboxylic acid, pentacyclododecanedicarboxylic acid; terephthalic acid, isophthalic acid Examples include units derived from aromatic dicarboxylic acids such as acid, phthalic acid, 2-methylterephthalic acid, biphenyldicarboxylic acid, and tetralindicarboxylic acid. Among these, a unit derived from an aromatic dicarboxylic acid is preferable from the viewpoint of thermal properties and mechanical properties of the polyester resin (A), and a unit derived from terephthalic acid and isophthalic acid is particularly preferable. The polyester resin (A) may contain one type of unit derived from dicarboxylic acid not having a naphthalene skeleton, or may contain two or more types.

  The polyester resin (A) of the present invention is 3,9-bis (1,1-dimethyl-2-hydroxyethyl) 2,4,8,10- as a unit derived from a diol having a cyclic acetal skeleton in consideration of heat resistance. The unit derived from tetraoxaspiro [5.5] undecane preferably has a unit derived from 2,6-naphthalenedicarboxylic acid as a unit derived from a dicarboxylic acid having a naphthalene skeleton, and is economical and has mechanical properties. Considering the balance, it is preferable to have a unit derived from ethylene glycol as a unit derived from diol having no cyclic acetal skeleton and a unit derived from terephthalic acid as a unit derived from dicarboxylic acid not having a naphthalene skeleton.

  The method for producing the polyester resin (A) used in the present invention is not particularly limited, and conventionally known methods can be applied. Examples thereof include a melt polymerization method such as a transesterification method and a direct esterification method, or a solution polymerization method. As the transesterification catalyst, esterification catalyst, etherification inhibitor, heat stabilizer, light stabilizer and other various stabilizers, polymerization regulators and the like, conventionally known ones can be used.

  Next, the multilayer sheet of the present invention will be described. The multilayer sheet of the present invention comprises the above-described polyester resin (A), polyester resin (B) excluding polyester resin (A), acrylic resin, polystyrene resin, polycarbonate resin, methyl methacrylate-styrene copolymer, acrylonitrile-butadiene- It is obtained by molding one or more transparent resins selected from styrene copolymers, vinyl chloride resins, and alicyclic polyolefin resins into a multilayer sheet having at least two layers. As the polyester resin (B), polyethylene terephthalate, polyethylene naphthalate, isophthalic acid-modified polyethylene terephthalate, 1,4-cyclohexanedimethanol-modified polyethylene terephthalate, and polyarylate are preferable.

  The configuration of the multilayer sheet of the present invention may be selected depending on the application. For example, polyester resin (A) layer / transparent resin layer, two types and two layers, transparent resin layer / polyester resin (A) layer / transparent resin layer or polyester resin ( A) layer / transparent resin layer / polyester resin (A) layer, two types and three layers, polyester resin (A) layer / transparent resin layer / polyester resin (A) layer / transparent resin layer / polyester resin (A) or transparent resin Examples of the structure include layer 5 / polyester resin (A) layer / transparent resin layer / polyester resin (A) layer / transparent resin layer. For example, when an acrylic resin is selected as the transparent resin in a configuration using a transparent resin for the skin layer, a multilayer sheet having excellent weather resistance and surface hardness can be obtained with respect to the single-layer sheet of the polyester resin (A). When acrylic resin, polystyrene resin, methyl methacrylate-styrene copolymer, etc. are selected as the transparent resin in a configuration using a transparent resin for the core layer, a multilayer sheet having excellent impact resistance with respect to a single layer sheet of these resins. can get. When a polycarbonate resin is selected for the core layer, a multilayer sheet having an excellent surface hardness relative to a single layer sheet of the polycarbonate resin can be obtained.

  Among the multilayer sheets of the present invention, a particularly preferred structure is a multilayer sheet comprising at least one layer comprising a polyester resin (A) and at least one layer comprising a polyester resin (B), and the polyester resin (A) / polyester resin. (B) two types and two layers, polyester resin (A) / polyester resin (B) / polyester resin (A) or polyester resin (B) / polyester resin (A) / polyester resin (B), two types and three layers, Polyester resin (A) / Polyester resin (B) / Polyester resin (A) / Polyester resin (B) / Polyester resin (A) or Polyester resin (B) / Polyester resin (A) / Polyester resin (B) / Polyester resin (A) / polyester resin (B), 2 types, 5 layers, polyester resin (B) / polyester Fat (A) / Polyester resin (B ′) / Polyester resin (A) / Polyester resin (B) or Polyester resin (A) / Polyester resin (B) / Polyester resin (B ′) / Polyester resin (B) / Polyester Three types and five layers of the resin (A) can be exemplified. Of the above-described structures, the polyester resin (B) is particularly preferably polyethylene terephthalate. The multilayer sheet composed of the polyester resin (A) and polyethylene terephthalate has improved heat resistance as compared with the single-layer sheet of polyethylene terephthalate. Therefore, the multilayer sheet of the present invention is, for example, a transparent container that requires sterilization and sterilization, a heat-resistant transparent beverage cup, a vegetable tray, a container that requires reheating, a food packaging material such as a lid, and a clear case. / It can be suitably used for packaging materials for export products that exceed the equator, such as clear boxes (bending products), electric lamp covers, blisters.

  As a method for producing the multilayer sheet of the present invention, a known laminating technique such as a coextrusion method, a coextrusion laminating method, an extrusion laminating method, or a dry laminating method can be used. Moreover, you may use the adhesive agent suitable between resin for these lamination | stacking, or adhesive resin.

  The total light transmittance of the multilayer sheet of the present invention is preferably 86% or more as measured by a 1.0 mm thick multilayer sheet based on ASTM D1003. If it is less than 86%, a multilayer sheet having a thickness exceeding 1.0 mm is not preferable because of insufficient transparency.

  In addition, the multilayer sheet of the present invention was cut out from a 1.0 mm thick multilayer sheet in a lengthwise and widthwise direction with a lengthwise and widthwise direction cut out to a square and 100 mm square test piece, and the test piece was placed in an oven in increments of 5 ° C. The maximum temperature at which the vertical and horizontal shrinkage after heating is not more than 5% is preferably 85 ° C. or higher, more preferably 90 ° C. or higher. When the maximum temperature is less than 85 ° C., the multilayer sheet tends to be deformed when touched with hot water or the like, which is not preferable.

  The thickness of each layer of the multilayer sheet of the present invention is determined according to the use, the type of resin forming the layer, the number of layers, etc., but is usually 50 μm to 10 mm. Moreover, the total thickness of a multilayer sheet changes with uses, for example, is 0.1-3 mm in the sheet | seat for foodstuffs, etc., and 1-40 mm is used in thick material sheets, such as a building material and a product display. The total number of layers of the polyester resin (A) layer and the transparent resin layer is usually up to 6 layers.

  The multilayer sheet of the present invention can be used for building materials, for example, exterior applications such as vending machine lighting panels, showcases, outdoor signage, carports, various industrial machine covers, windshields, partition boards, and the like. Examples of food applications include transparent containers that require sterilization and sterilization, heat-resistant transparent beverage cups, prepared food trays, containers that require reheating, and lid materials. In other fields, clear cases / clear boxes (folded and molded products), electric lamp covers, blisters, packaging materials for export products that go directly under the equator, and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by these examples.

[Synthesis of polyester resin (A)]
The raw material monomers in the amounts shown in Tables 1 and 2 were added to a 0.15 cubic meter polyester production apparatus equipped with a packed tower rectification tower, a partial condenser, a full condenser, a cold trap, a stirrer, a heating device, and a nitrogen introduction pipe. In the presence of 0.03 mol of manganese acetate tetrahydrate per 100 mol of the dicarboxylic acid component, the ester exchange reaction was carried out by raising the temperature to 215 ° C. in a nitrogen atmosphere. After the amount of distilled methanol reached 80% or more of the theoretical amount, 0.01 mol of antimony (III) oxide and 0.06 mol of triethyl phosphate were added to 100 mol of the dicarboxylic acid component, The pressure was gradually reduced, and polymerization was finally performed at 280 ° C. and 100 Pa or less. The reaction was terminated when an appropriate melt viscosity was reached, and a polyester resin (A) was obtained.

[Production of multilayer sheet]
The core layer raw material is extruded using a 65 mm extruder, while the skin layer raw material is extruded using a 30 mm extruder, and a two-layer / three-layer multilayer sheet (multilayer sheet thickness: about 1.0 mm, using a feed block type die) Skin layer thickness: about 100 μm) was prepared. In addition, Nihon Unipet Co., Ltd. and UNIPET RT553C were used as polyethylene terephthalate (PET), and Mitsubishi Engineering Plastics Co., Ltd. Iupilon E-2000 was used as polycarbonate.

[Preparation of multilayer sheet compact]
The multilayer sheet was formed into a cup having a drawing ratio of 0.5 using a vacuum / pressure forming machine manufactured by Asano Laboratory.

[Evaluation of polyester resin (A)]
(1) Resin composition The composition of each structural unit was calculated by ¹ H-NMR measurement. The measuring apparatus used JNM-AL400 by JEOL Co., Ltd., and measured it at 400 MHz. Deuterated chloroform was used as the solvent.
(2) Glass transition temperature As for the glass transition temperature of the polyester resin, DSC / TA-50WS manufactured by Shimadzu Corporation is used, about 10 mg of the polyester resin is put in an aluminum non-sealed container, and the temperature is increased in a nitrogen gas (30 ml / min) stream. A sample heated and melted to 280 ° C. at a rate of 20 ° C./min was rapidly cooled to obtain a measurement sample. The sample was measured under the same conditions, and the temperature at which the difference between the baselines before and after the transition of the DSC curve changed by 1/2 was taken as the glass transition temperature.

[Evaluation of multilayer sheet]
(1) Heat resistance From a 1.0 mm thick multi-layer sheet, a square test piece of length and width 100 mm is cut out with the extrusion direction being vertical and the width direction being horizontal, and this test piece is heated in an oven in increments of 5 ° C. for 30 minutes. The maximum shrinkage rate in the vertical and horizontal directions after heating did not exceed 5%.
(2) Total light transmittance A multilayer sheet having a thickness of 1.0 mm was measured according to JIS-K-7105 and ASTM D1003. The measuring device used is a cloudiness value measuring device (model: COH-300A) manufactured by Nippon Denshoku Industries Co., Ltd.
(3) Haze value
A 1.0 mm thick multilayer sheet was measured according to JIS-K-7105 and ASTM D1003. The measuring device used is a cloudiness value measuring device (model: COH-300A) manufactured by Nippon Denshoku Industries Co., Ltd.
(4) Layer configuration The thickness of each layer was measured by observing with a microscope the cross section of the multilayer sheet that had been smoothed by cutting with a glass knife.

[Evaluation of multilayer sheet compacts]
(1) Heat resistance The multilayer sheet molded body was heated in an oven in increments of 5 ° C for 30 minutes, and the maximum temperature at which the volume retention after heating did not become 95% or less was set. The volume retention rate was calculated from the weight of water that can be filled in the container before and after the treatment.

Abbreviations in the table are shown below.
DMT: dimethyl terephthalate EG: ethylene glycol SPG: 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane DOG: 5-methylol -5-ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1,3-dioxane PET: Polyethylene terephthalate PC: Polycarbonate

Claims (7)

1-80 mol% in the diol unit is a unit derived from a diol having a cyclic acetal skeleton, and 1-100 mol% in a dicarboxylic acid unit is a unit derived from a dicarboxylic acid having a naphthalene skeleton (A And at least one selected from the group consisting of a polyester resin (B) other than the polyester resin (A), an acrylic resin, a polystyrene resin, a polycarbonate resin, and a methyl methacrylate-styrene copolymer. A multilayer sheet comprising at least one layer made of a resin. The diol unit having a cyclic acetal skeleton of the polyester resin (A) is represented by the general formula (1):

(In the formula, R ¹ and R ² are each independently an aliphatic group having 1 to 10 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and an aromatic group having 6 to 10 carbon atoms. Represents an organic group selected from the group consisting of
Or general formula (2):

(In the formula, R ¹ is the same as above, and R ³ is an aliphatic group having 1 to 10 carbon atoms, an alicyclic group having 3 to 10 carbon atoms, and an aromatic group having 6 to 10 carbon atoms. Represents an organic group selected from the group consisting of
The multilayer sheet according to claim 1, which is a unit derived from a diol represented by the formula: The diol unit having a cyclic acetal skeleton of the polyester resin (A) is 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, The multilayer sheet according to claim 1, which is a unit derived from 5-methylol-5-ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1,3-dioxane. The dicarboxylic acid unit having a naphthalene skeleton in the dicarboxylic acid unit of the polyester resin (A) is 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid. The multilayer sheet according to any one of claims 1 to 3, which is a unit derived from one or more dicarboxylic acids selected from the group consisting of 2,7-naphthalenedicarboxylic acid. The multilayer sheet according to any one of claims 1 to 4, which has the following physical properties (1) to (2).
(1) The total light transmittance of a multilayer sheet having a thickness of 1.0 mm is 86% or more.
(2) When a square test piece of length and width 100 mm is cut out from a 1.0 mm-thick multilayer sheet with the extrusion direction as the length and the width direction as the width, and this test piece is heated in an oven in increments of 5 ° C. for 30 minutes The maximum temperature at which the shrinkage in the vertical and horizontal directions after heating does not exceed 5% is 85 ° C. or higher. The multilayer sheet according to any one of claims 1 to 5, wherein the layer made of a resin other than the polyester resin (A) is a layer made of the polyester resin (B). The multilayer sheet according to any one of claims 1 to 6, wherein the polyester resin (B) is polyethylene terephthalate.