Polyester film for molding

Abstract

The purpose of the present invention is to provide a polyester film for molding, which is excellent in terms of moldability, in particular, moldability at low temperature and low pressure even if the film is thin, and which is also excellent in terms of solvent resistance and heat resistance, while having a small environmental load. A polyester film for molding according to the present invention has a surface layer on one surface or both surfaces of a base material layer, and satisfies: (1) the storage elastic modulus (E') in the flow direction and that in the width direction are respectively 10-700 MPa at 100°C; (2) the refractive index Nx in the flow direction and the refractive index Ny in the width direction are respectively 1.650-1.570, and satisfy 0.995 ≤ Nx / Ny ≤ 1.005; (3) the density is 1.365-1.385 g / cm3; (4) the thermal shrinkage ratio at 150°C in the flow direction and that in the width direction are respectively 0.01-3.0%; and (5) the specific heat difference ΔCp at the glass transition temperature in temperature-modulated DSC is 0.12-0.20 J / (g∙°C).

Description

Polyester film for molding

[0001] The present invention relates to a polyester film for molding that has excellent formability, particularly at low temperatures and low pressures, even in the form of a thin film, and also has excellent solvent resistance and heat resistance, and further has a small environmental impact, and can be suitably used for nameplates of home appliances and automobiles or as building materials, and to a method for producing a molded product using the same.

[0002] Conventionally, polyvinyl chloride film has been a typical molding sheet and has been used favorably in terms of processability, etc. However, this film has problems such as the generation of toxic gases when the film burns in a fire or the like, and the bleed-out of plasticizers, and in response to the recent need for environmental resistance, new materials with a low environmental impact are being sought.

[0003] To satisfy these requirements, unstretched sheets made of non-chlorine-based materials such as polyester, polycarbonate, and acrylic resins have been used in a wide range of fields. Unstretched sheets made of polyester resins have attracted attention, particularly because of their excellent mechanical properties, transparency, and economical advantages. For example, an unstretched polyester sheet has been disclosed, which is made of a substantially amorphous polyester resin in which approximately 30 mol% of the ethylene glycol component in polyethylene terephthalate has been replaced with 1,4-cyclohexanedimethanol (see, for example, Patent Document 1).

[0004] Although the above-mentioned unstretched polyester sheets satisfy market requirements in terms of formability and lamination suitability, because they are unstretched sheets, they do not have sufficient heat resistance or solvent resistance and do not yet satisfy the high demands of the market.

[0005] As a method for solving the above problems, a method using a biaxially stretched polyethylene terephthalate film has been disclosed (see, for example, Patent Document 2).

[0006] However, although the above method improves heat resistance and solvent resistance, it also increases the degree of orientation and crystallinity, resulting in insufficient moldability, and does not satisfy market demands in terms of overall quality balance.

[0007] As a method for solving the above-mentioned problems, a method has been proposed in which a copolymer polyester resin of a specific composition is used as a raw material to improve the above-mentioned problems (see, for example, Patent Document 3). These methods can significantly improve moldability, which allows for lower molding temperatures, and the finish quality of the resulting molded product in molded molding methods that use high molding pressures during molding. However, for molding methods that use low molding pressures during molding, such as compressed air molding and vacuum molding, which have seen increasing market demand in recent years, there is a need for further improvement in the finish quality of molded products. As a method for satisfying the above-mentioned needs, it has been proposed to specify the storage modulus of a biaxially oriented polyester film containing neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, or the like as a copolymerization component (see, for example, Patent Document 4).

[0008] Furthermore, with the recent increase in environmental awareness, there is a demand for thinner films. However, it has been found that the thermal shrinkage rate of the biaxially oriented polyester film increases with the reduction in thickness, and wrinkles appear over time. As a result, conventional biaxially oriented polyester films have not been able to achieve both volume reduction and designability, which are required in the market.

[0009] Japanese Patent Application Laid-Open No. 2002-249652 Japanese Patent Application Laid-Open No. 11-268215 Japanese Patent Application Laid-Open No. 2004-75713 Japanese Patent Application Laid-Open No. 2010-229416

[0010] The object of the present invention is to solve the problems of the prior art described above, and to provide a polyester film for molding that has excellent formability, particularly at low temperatures and low pressures, even when it is a thin film, and that also has excellent solvent resistance and heat resistance, and that further has a small environmental impact, and a method for producing a molded product using the same.

[0011] The present inventors conducted extensive research to solve the above-mentioned problems, and discovered that by appropriately adjusting physical properties of a polyester film for molding, such as its molecular orientation and in-plane balance, rigidity during heating, residual stress, and crystallinity, which are indicators of moldability, particularly at low and high temperatures, the moldability can be improved. This led to the completion of the present invention. Specifically, the present invention comprises the following configuration: 1. A polyester film for molding having a base layer and a surface layer on one or both sides of the base layer, the polyester film for molding satisfying the following (1) to (5): (1) The storage modulus (E') in both the machine direction and the width direction is 10 to 700 MPa at 100°C; (2) The refractive index Nx in the machine direction and the refractive index Ny in the width direction are both 1.650 to 1.570, and Nx / Ny satisfies the relationship 0.995≦Nx / Ny≦1.005; and (3) The density is 1.365 to 1.385 g / cm. ３(4) The heat shrinkage at 150°C in the machine direction and width direction is 0.01 to 3.0%. (5) The specific heat difference ΔCp at the glass transition temperature in temperature-modulated DSC is 0.12 to 0.20 J / (g°C). 2. The polyester film for molding described in above 1, having a haze of 0.1 to 3.0%. 3. The polyester film for molding described in above 1 or 2, wherein at least one of the base layer and the surface layer contains a copolymer polyester, the dicarboxylic acid component constituting the copolymer polyester is an aromatic dicarboxylic acid, and the diol component contains only ethylene glycol and diethylene glycol. 4. The polyester film for molding described in above 3, wherein the base layer and the surface layer contain the copolymer polyester, and when the total amount of diol components constituting the entire polyester containing the copolymer polyester contained in the base layer and the surface layer is taken as 100 mol %, diethylene glycol accounts for 14 to 20 mol %. 5. 5. The polyester film for molding according to any one of items 1 to 4, wherein the surface layer has a thickness of 0.01 to 3 μm. 6. The polyester film for molding according to any one of items 1 to 5, wherein the surface layer contains particles, the average particle size of the particles being 0.01 to 6 μm, and the particle content in the surface layer being 0.01 to 25 mass %. 7. A method for producing a molded product, comprising molding a film-like or bulk-like molded product using the polyester film for molding according to any one of items 1 to 6.

[0012] The polyester film for molding of the present invention, even though it is a thin film, has excellent moldability during heat molding, particularly at low temperatures and low pressures, and is therefore applicable to a wide range of molding methods.In addition, when used as a molded product under room temperature, it has excellent elasticity and shape stability, as well as excellent solvent resistance and heat resistance, and is suitable for use as a nameplate for home appliances and automobiles or as a building material component, while reducing the environmental load.

[0013] (Polyester Film for Molding of the Present Invention) The polyester film for molding of the present invention has a base layer and a surface layer on one or both sides thereof, and is characterized by satisfying the physical properties described in detail below. The physical properties may be specified in the machine direction and width direction of the film, but the "machine direction" is synonymous with the longitudinal direction, longitudinal direction, machine direction, and MD direction, and the "width direction" refers to the direction perpendicular to these. Furthermore, the term "polyester film for molding" refers to a polyester film before molding that undergoes thermal deformation during molding. This term includes not only cases where the film is used for molding itself, but also cases where it is used for integral molding with other components or transfer molding in which a printed layer or the like is transferred to other components. It also includes cases where a molded film is obtained using the polyester film for molding in advance, and then this film is used to integrally mold other components, and cases where the molding of the polyester film for molding and the molding of other components are carried out simultaneously.

[0014] Regardless of the type of molded product, the polyester film for molding of the present invention has excellent moldability during hot molding, particularly at low temperatures and low pressures, even though it is a thin film, and can therefore be applied to a wide range of molding methods.

[0015] (Physical Properties of Polyester Film for Molding) The polyester film for molding of the present invention preferably has a storage modulus (E') in both the machine direction and the width direction of 10 to 700 MPa at 100° C. The storage modulus (E') is an index of rigidity around the measurement temperature, and by controlling this within the above range, moldability, particularly moldability at low temperatures and low pressures, can be ensured, and molded products with good finish can be obtained even by molding methods with low molding pressures of 10 atmospheres or less, such as pressure molding and vacuum molding.

[0016] The inventors have not been able to clearly clarify the mechanism why the storage modulus (E') at 100°C serves as an index for expressing the above-mentioned film properties, but they presume that this is because the molecular structure of the copolymerization component contained in the polyester constituting the film contributes to the rigidity of the film at around 100°C.

[0017] The lower limit of the storage modulus (E') at 100°C in the machine direction and width direction is more preferably 20 MPa, even more preferably 30 MPa, and particularly preferably 40 MPa. The upper limit is more preferably 680 MPa, even more preferably 660 MPa, and particularly preferably 640 MPa. A storage modulus of 10 MPa or more is preferable because sufficient stress is generated at the corners of the mold during molding, resulting in good uniform moldability. A storage modulus of 700 MPa or less is also preferable because good molding can be easily achieved even at low temperatures and low pressures.

[0018] The polyester film for molding of the present invention preferably has a machine direction refractive index Nx and a width direction refractive index Ny of 1.650 to 1.570, and Nx / Ny preferably satisfies the following formula: 0.995≦Nx / Ny≦1.005. Nx and Ny are indicators of the molecular orientation of polymer chains, and Nx / Ny is an indicator of the in-plane balance of molecular orientation. The upper limits of Nx and Ny are more preferably 1.640, even more preferably 1.630, and particularly preferably 1.620. The lower limits of Nx and Ny are more preferably 1.575, even more preferably 1.580, and particularly preferably 1.585. Setting Nx and Ny to 1.650 or less is preferable because stress during molding does not increase too much, resulting in good moldability. Furthermore, setting Nx and Ny to 1.570 or more is preferable because sufficient stress is generated at the corners of the mold during molding, resulting in good, uniform moldability.

[0019] In the present invention, the density of the film is an index of crystallinity and degree of crystallinity, and is 1.365 to 1.385 g / cm ３ The upper limit of the density of the film is preferably 1.384 g / cm ３ More preferably, 1.383 g / cm ３ More preferably, 1.382 g / cm ３ The lower limit of the film density is 1.366 g / cm ３ More preferably, 1.367 g / cm ３ is more preferably 1.368 g / cm ３ The density of the film is particularly preferably 1.385 g / cm ３If the density of the film is 1.365 g / cm or less, the stress does not increase too much, the film is less likely to break during molding, and sufficient moldability is obtained, which is preferable. ３ By setting the temperature to the above level, appropriate crystallinity can be obtained, and peeling and wrinkling due to shrinkage of the molded product can be suppressed, which is preferable.

[0020] In the present invention, the specific heat difference ΔCp at the glass transition temperature measured by temperature-modulated DSC is preferably 0.12 to 0.20 J / (g °C). The polymer chain of a polyester is considered to consist of a relatively rigid crystalline component, a rigid amorphous component, and a mobile amorphous component. ΔCp is an index of the amount of mobile amorphous component and is a parameter that affects shrinkage stress and dimensional stability. ΔCp is obtained from the reversible curve of temperature-modulated differential scanning calorimetry. In the stepwise change portion of the glass transition in a differential scanning calorimetry chart conforming to JIS K7121 (1987), the glass transition temperature is determined from the point where a line equidistant in the vertical direction from each extended baseline intersects with the curve of the stepwise change portion of the glass transition. Then, ΔCp is determined from the distance between two lines extending each of the baselines at the glass transition temperature.

[0021] The upper limit of ΔCp is more preferably 0.195 J / (g ° C), even more preferably 0.19 J / (g ° C), and particularly preferably 0.185 J / (g ° C). On the other hand, the lower limit of ΔCp is more preferably 0.125 J / (g ° C), even more preferably 0.13 J / (g ° C), and particularly preferably 0.135 J / (g ° C). When ΔCp is 0.12 J / (g ° C) or more, the shrinkage stress of the molded product is reduced, and peeling of the molded product is suppressed, which is preferable. Furthermore, when ΔCp is 0.20 J / (g ° C) or less, the shrinkage rate of the film over time is reduced, and even when the film is thinned, wrinkles over time are less likely to be observed in the film roll, which is preferable.

[0022] In the film of the present invention, the heat shrinkage rate in the longitudinal and width directions at 150°C is preferably 0.01 to 3.0%. The lower limit of the heat shrinkage rate at 150°C is more preferably 0.1%, even more preferably 0.4%. On the other hand, the upper limit of the heat shrinkage rate at 150°C is more preferably 2.6%, even more preferably 2.2%, and particularly preferably 1.8%. Even if a biaxially stretched polyester film for molding is produced having a heat shrinkage rate of less than 0.01% in the longitudinal and width directions at 150°C, no significant difference in practical effect is observed and productivity is significantly reduced, so there is no need to make the heat shrinkage rate less than 0.01% at 150°C. A heat shrinkage rate of 3.0% or less in the longitudinal and width directions at 150°C is preferred because the film is less likely to deform in post-treatment processes that involve heat, such as vapor deposition, sputtering, or printing, and a good film appearance and design can be easily obtained after post-processing.

[0023] In the present invention, the haze of the film is preferably 0.1 to 3.0%. The lower limit of the haze is more preferably 0.3%, and even more preferably 0.5%. On the other hand, the upper limit of the haze is more preferably 2.5%, and even more preferably 2.0%. A film with a haze of less than 0.1% has poor slip properties, making it difficult to produce on an industrial scale with normal productivity. Furthermore, when the vapor-deposited or sputtered surface of a metal or the like or the printed surface is viewed from the back of the film, the metal surface or printing becomes clear, which is preferable, as it makes it easier to achieve a good design.

[0024] (Materials and Manufacturing Method) In the present invention, the film raw materials for the base layer and surface layer may be any of copolymer polyester alone, a blend of one or more homopolyesters or copolymer polyesters, or a combination of homopolyester and copolymer polyester.

[0025] When a copolymer polyester composed of an aromatic dicarboxylic acid component, ethylene glycol, and diethylene glycol is used as the copolymer polyester, the aromatic dicarboxylic acid component is preferably terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, or an ester-forming derivative thereof, and the amount of the terephthalic acid and / or naphthalenedicarboxylic acid component relative to the total dicarboxylic acid components is preferably 70 mol % or more, more preferably 85 mol % or more, even more preferably 95 mol % or more, and particularly preferably 100 mol %. Such a copolymer polyester can be used in at least one of the base layer and the surface layer, but is preferably used in the base layer and the surface layer.

[0026] The use of diethylene glycol as a copolymerization component is suitable for imparting good moldability, and is also preferred in terms of excellent transparency and heat resistance, and improving adhesion with the adhesion-modifying layer.

[0027] Furthermore, when a copolymerized polyester composed of an aromatic dicarboxylic acid component and a diol component containing diethylene glycol and ethylene glycol, or when such a copolymerized polyester and another polyester are used as the polyester, it is preferable that the diethylene glycol content be 14 to 20 mol% relative to the total diol component constituting the entire polyester, including the copolymerized polyester, contained in the base layer and the surface layer, be 100 mol%. The upper limit of diethylene glycol is more preferably 19.5 mol%, even more preferably 19 mol%, and particularly preferably 18.5 mol%. The lower limit of diethylene glycol is more preferably 14.5 mol%, even more preferably 15 mol%, and particularly preferably 15.5 mol%. A diethylene glycol content of 14 mol% or more relative to the total diol components is preferred because it provides a film that conforms well to the mold during molding and is less likely to break. Furthermore, a diethylene glycol content of 20 mol% or less relative to the total diol components is preferred because it not only provides sufficient stress during molding, reducing molding unevenness, but also reduces shrinkage over time and reduces wrinkles over time. The diol components constituting the copolymerized polyester contained in the base layer and the surface layer are preferably ethylene glycol and diethylene glycol only.

[0028] Furthermore, when the total amount of all diol components constituting the entire polyester, including the copolymerized polyester, contained in the base layer and the surface layer is taken as 100 mol %, it is preferable to use 14 to 20 mol % of diethylene glycol, since this makes it easy to control the storage modulus to 10 to 700 MPa and improves low-temperature moldability.

[0029] Furthermore, when the total diol components constituting the entire polyester including the copolymerized polyester contained in the base layer and the surface layer are taken as 100 mol %, if diethylene glycol is 14 to 20 mol %, Nx and Ny are 1.650 to 1.570, and the density is 1.365 to 1.385 g / cm ３ This is preferable because it is easy to control the viscosity and to obtain easy moldability.

[0030] Examples of the catalyst that can be used in producing the copolymerized polyester include alkaline earth metal compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, titanium / silicon composite oxides, germanium compounds, etc. Among these, titanium compounds, antimony compounds, germanium compounds, and aluminum compounds are preferred in terms of catalytic activity.

[0031] When the copolymer polyester is produced, it is preferable to add a phosphorus compound as a heat stabilizer, such as phosphoric acid or phosphorous acid.

[0032] The copolymer polyester preferably has an intrinsic viscosity of 0.50 dL / g or more, more preferably 0.55 dL / g or more, and particularly preferably 0.60 dL / g or more. An intrinsic viscosity of 0.50 dL / g or more is preferred because it tends to improve moldability, adhesion, and film formation stability. Furthermore, when a filter for removing foreign matter is provided in the melt line, the upper limit of the intrinsic viscosity is preferably set to 1.0 dL / g from the viewpoint of discharge stability during extrusion of the molten resin.

[0033] In the present invention, by forming a film by blending one or more homopolyesters or copolymer polyesters as raw materials for the base layer and the surface layer, it is possible to achieve transparency and a high melting point (heat resistance) while maintaining flexibility equivalent to that achieved when only copolymer polyesters are used.Furthermore, compared to when only a high-melting-point homopolyester (e.g., polyethylene terephthalate) is used, it is possible to achieve flexibility and a practically acceptable melting point (heat resistance) while maintaining high transparency.

[0034] The melting point of the polyester film is preferably 200 to 245°C from the viewpoints of heat resistance and moldability. By controlling the type and composition of the polymer used and the film-forming conditions within the above melting point range, a balance between moldability and finish can be achieved, enabling economical production of high-quality molded products. Here, the melting point refers to the endothermic peak temperature during melting detected during the first temperature rise in so-called differential scanning calorimetry (DSC). The melting point was determined by measurement at a temperature rise rate of 20°C / min using a differential scanning calorimeter (DSC3100S, manufactured by Mac Science). The lower limit of the melting point is more preferably 210°C, and particularly preferably 220°C. A melting point of 200°C or higher is preferable because it provides good heat resistance.

[0035] The upper limit of the melting point is preferably higher from the viewpoint of heat resistance, but when the polyethylene terephthalate unit is the main component, a melting point of 250° C. or less is preferred because it provides good moldability and transparency.

[0036] The base layer preferably comprises only a polyester component as a polymer component, and preferably contains 14 to 20 mol% diethylene glycol when the total diol components constituting the polyester are taken as 100 mol%, and preferably has a thickness of 5 μm or more. The lower limit of the base layer thickness is more preferably 10 μm, and particularly preferably 15 μm. On the other hand, the upper limit of the base layer thickness is preferably 300 μm, and more preferably 280 μm. A base layer thickness of 5 μm or more is preferred because it results in a film that is less likely to break during film formation or molding. Furthermore, a base layer thickness of 300 μm or less is preferred because it is more likely to increase stress when the film is stretched, and therefore a film with excellent thickness precision is more likely to be obtained.

[0037] The thin surface layer can be formed by coating or co-extrusion, of which the co-extrusion method is preferred because it does not require a solvent, which reduces the environmental impact and improves economic efficiency.

[0038] When a thin surface layer is formed by co-extrusion, it is preferable that the polymer component is composed solely of a polyester component, and that the amount of diethylene glycol is 14 to 20 mol % when the total amount of diol components constituting the polyester is 100 mol %. Controlling the amount of diethylene glycol within this range is preferable because it not only makes the film less likely to break during molding, improves mold conformability, and reduces molding unevenness, but also makes it easier to obtain a film that shrinks less over time and is less likely to wrinkle over time.

[0039] In addition, in order to improve the handling properties of the film, such as its slipperiness and winding properties, it is preferable to form irregularities on the film surface. As a method for forming irregularities on the film surface, a method of incorporating particles into the film is preferably used. In particular, it is preferable to incorporate particles into the surface layer.

[0040] Examples of the particles include internally precipitated particles having an average particle size of 0.01 to 6 μm, and external particles such as inorganic and / or organic particles. Using particles having an average particle size of 6 μm or less is preferable because it is less likely to cause defects in the film and is more likely to achieve good design and transparency. Furthermore, an average particle size of 0.01 μm or more is preferable because it provides good film lubricity, windability, and other properties, resulting in good handleability. From the viewpoint of handleability, such as lubricity and windability, the lower limit of the average particle size of the particles is more preferably 0.1 μm, and even more preferably 0.5 μm. On the other hand, from the viewpoint of transparency and reduction of film defects due to coarse protrusions, the upper limit of the average particle size of the particles is more preferably 5 μm, and even more preferably 2 μm.

[0041] The average particle diameter of the particles can be calculated by taking multiple photographs of at least 200 particles using an electron microscope, tracing the outlines of the particles on an OHP film, and converting the traced images into circle-equivalent diameters using an image analyzer.

[0042] Examples of the outer particles that can be used include inorganic particles such as wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, and hydroxyapatite, and organic particles containing styrene, silicone, acrylic acids, etc. Among these, inorganic particles such as dry, wet, and dry colloidal silica and alumina, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene, etc. are preferably used. Two or more of these inner particles, inorganic particles, and / or organic particles may be used in combination within a range that does not impair the properties specified in the present invention.

[0043] Furthermore, the content of the particles in the film is preferably in the range of 0.01 to 25% by mass. A content of 0.01% by mass is preferred because it facilitates obtaining good slipperiness of the film, improves winding properties, and provides good handling properties. Furthermore, a content of 25% by mass or less is preferred because it facilitates obtaining good transparency, further reduces the formation of coarse protrusions, and facilitates obtaining good film-forming properties and transparency. In particular, the content of the particles in the surface layer is preferably 0.01 to 25% by mass, more preferably 0.02 to 10% by mass, particularly preferably 0.02 to 3% by mass, and most preferably 0.03 to 1% by mass.

[0044] Furthermore, particles contained in the film generally have a different refractive index from that of polyester, which can reduce the transparency of the film. To enhance the design of molded products, printing is often applied to the film surface before molding. Since such a printing layer is often applied to the back side of the molding film, high film transparency is required for print clarity.

[0045] Therefore, in order to obtain high transparency while maintaining the film's handleability, it is effective to use a laminate film having a laminate structure in which particles are substantially not contained in the base layer of the main layer, and particles are contained only in the surface layer having a thickness of 0.01 to 3 μm per layer. The upper limit of the thickness of the surface layer is more preferably 2 μm, and particularly preferably 1 μm. In this case, the particles exemplified above can be used.

[0046] In the present invention, in order to make the haze of the film 0.1 to 3.0%, it is preferable to form a laminate structure in which the above-mentioned base layer does not substantially contain particles, and surface layers each having a thickness of 0.01 to 3 μm are formed and particles are contained only in the surface layers.

[0047] The above phrase "substantially no particles are contained in the base layer" means, for example, in the case of inorganic particles, that the content is below the detection limit when the inorganic element is quantified by fluorescent X-ray analysis. This is because even if particles are not intentionally added to the base layer, contaminants derived from foreign matter may be mixed in. To obtain a film with low haze and excellent design, it is preferable that the base layer does not substantially contain particles, but particles may be added to the base layer as long as the content is 30 ppm or less.

[0048] On the other hand, when silica particles having an average particle diameter of 1.5 μm or less are used as particles to be contained in the surface layer, cut edges of the film or waste film generated during paper passing may be remelted and contained in the base layer. In this case, the particle content in the base layer is preferably 700 ppm or less. When silica particles having an average particle diameter of 1.5 μm or less are used, it is preferable to set the particle content in the base layer to 700 ppm or less, because this makes it easier to obtain a film with low haze and excellent design. By reusing the film in this way, the amount of film to be discarded is reduced and environmental adaptability is improved.

[0049] The particles contained in the surface layer may be the same as those described above. Among these particles, silica particles, glass filler, and silica-alumina composite oxide particles are particularly suitable from the viewpoint of transparency because their refractive indexes are relatively close to that of polyester.

[0050] The polyester film of the present invention can be formed into a laminate structure by a known method using different types of polyesters to impart other functions. The form of such a laminate film is not particularly limited, but examples thereof include a two-type two-layer structure (X / Y), a two-type three-layer structure (X / Y / X), and a three-type three-layer structure (X / Y / Z), where the layers formed by different extruders are a surface layer X, a base layer Y, and another layer Z, respectively.

[0051] The polyester film for molding of the present invention is preferably a biaxially stretched film. In the present invention, molecular orientation by biaxial stretching improves the solvent resistance and dimensional stability, which are drawbacks of unstretched sheets. That is, the present invention can improve the solvent resistance and heat resistance, which are drawbacks of unstretched sheets, while maintaining the excellent moldability of the unstretched sheet.

[0052] The method for producing the biaxially stretched polyester film is not particularly limited, but an example thereof is a method in which a polyester resin is dried as necessary, then fed into a known melt extruder, extruded into a sheet form through a slit die, brought into close contact with a casting drum by electrostatic application or the like, cooled and solidified, to obtain an unstretched sheet (raw sheet), and then the unstretched sheet is biaxially stretched. For the melt extrusion, so-called coextrusion, in which the raw materials for the base layer and the surface layer are simultaneously extruded from separate extruders, can be preferably used.

[0053] As a biaxial stretching method, a method is employed in which an unstretched sheet is stretched in the machine direction (MD) and the width direction (TD) and heat-treated to obtain a biaxially stretched film with the desired planar orientation. Among these methods, from the viewpoint of film quality, sequential biaxial stretching methods such as the MD / TD method in which the sheet is stretched in the machine direction and then in the width direction, or the TD / MD method in which the sheet is stretched in the width direction and then in the machine direction, and simultaneous biaxial stretching methods in which the sheet is stretched in the machine direction and the width direction almost simultaneously are desirable. In addition, in the case of simultaneous biaxial stretching, a tenter driven by a linear motor may be used. Furthermore, if necessary, a multi-stage stretching method in which stretching in the same direction is performed in multiple stages may be used.

[0054] The film stretching ratio during biaxial stretching is preferably 3.4 to 4.2 times in the longitudinal direction, and particularly preferably 3.5 to 4.1 times. Furthermore, the stretching ratio in the width direction is preferably 3.1 to 3.5 times, and particularly preferably 3.2 to 3.4 times. When the stretching ratio is within the above range, Nx and Ny can be easily controlled to 1.650 to 1.570, and a film with good formability, finishability, and dimensional stability can be easily obtained, which is preferable.

[0055] As the stretching conditions when producing the polyester film for molding of the present invention, for example, the following conditions are preferably adopted.

[0056] In the longitudinal stretching, it is more preferable that the stretching temperature is 50 to 150° C. and the stretching ratio is 3.4 to 4.2 times so that the transverse stretching, which is usually performed afterward, can be carried out smoothly.

[0057] Furthermore, after biaxial stretching, the film is subsequently heat-treated in a tenter. The heat treatment is preferably carried out in a temperature range of 190 to 210°C. The lower limit of the heat treatment temperature is more preferably the melting point of 195°C, and the upper limit of the heat treatment temperature is more preferably 205°C. If the temperature is 210°C or lower, there is no risk of the film becoming embrittled and breaking during molding. Furthermore, if the temperature is 190°C or higher, the heat shrinkage rate and the degree of planar orientation do not become too high, and a film with excellent moldability is obtained, which is preferable. The heat treatment may be either a tension heat treatment or a relaxation treatment. To reduce the heat shrinkage rate, a relaxation treatment of 3 to 10% is preferred.

[0058] Generally, known means for reducing the heat shrinkage at 150°C are to reduce the stretch ratio and to reduce the amount of copolymerization component, but the former method may worsen the thickness unevenness of the film, and the latter method may increase the orientation of the molecular chains constituting the film, thereby worsening the formability, so these are not very preferred. In the present invention, it is preferable to perform heat setting in order to reduce the heat shrinkage at 150°C of the biaxially stretched polyester film.

[0059] (Method for Producing Molded Articles) The method for producing a molded article of the present invention is a production method in which a film-like or bulk-shaped molded article is molded using the polyester film for molding of the present invention as described above. When molding a bulk-shaped molded article, the polyester film for molding may be integrally molded with other members, or the polyester film for molding may be used as a transfer substrate. Furthermore, when producing a molded article integrated with other members, a method in which a molded film is obtained in advance using the polyester film for molding, and then the other members are integrally molded using this may be used, or a method in which the molding of the polyester film for molding and the molding of the other members are simultaneously performed.

[0060] In any case where a molded product is obtained, the polyester film for molding itself will be thermally deformed during molding. However, the polyester film for molding of the present invention, even though it is a thin film, has excellent moldability during heat molding, particularly at low temperatures and low pressures, and can therefore be applied to a wide range of molding methods.

[0061] In producing any molded product, a printability improving layer, a release layer, etc. can be provided on the polyester film for molding during molding, if necessary, and then a design such as a printed layer or a pattern layer can be applied by various printing and decoration methods such as letterpress printing, intaglio printing, lithographic printing, screen printing, offset printing, gravure printing, inkjet printing, and flexographic printing, as well as by decoration methods such as textile printing, transfer, coating, painting, vapor deposition, sputtering, CVD, lamination, etc. In this way, the film itself, a molded product in which the film is integrated with other members, or a molded product after transfer can be decorated.

[0062] As a method for molding (embossing, etc.) a film-shaped molded product, various molding methods such as mold molding, compressed air molding, vacuum molding, and roll molding can be used, and these molding methods can also be used when the polyester film for molding is molded in advance.

[0063] Examples of methods for molding a bulk molded product include insert molding, in which a molded or unmolded film is placed in a mold, and in-mold molding, in which a decorated polyester film for molding is used and transferred inside the mold.

[0064] The molding temperature when molding the polyester film for molding is, for example, 70 to 200°C, preferably 80 to 150°C. When the polyester film for molding is integrally molded with other members or when the polyester film for molding is used as a transfer substrate, a molding temperature appropriate for the materials of the other members or the transfer target is adopted. Other forming conditions can also be adopted depending on the various molding methods.

[0065] Specific examples of molded articles include housings or components for portable devices such as mobile phones, audio equipment, portable players / recorders, IC recorders, car navigation systems, and PDAs, and notebook PCs, nameplate components for home appliances and automobiles, and building materials.

[0066] The present invention will be described in detail below with reference to examples. The film properties obtained in each example were measured and evaluated by the following methods.

[0067] (1) Intrinsic Viscosity 0.1 g of a chip sample was precisely weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 60 / 40 (mass ratio), and the intrinsic viscosity was measured using an Ostwald viscometer at 30° C. The measurement was performed three times, and the average value was calculated.

[0068] (2) Haze According to JIS-K7136-2000, the haze of the film was measured using a haze meter (300A, manufactured by Nippon Denshoku Industries Co., Ltd.) The measurement was carried out twice, and the average value was calculated.

[0069] (3) Film Thickness Using a Millitron 1202D manufactured by Seiko EM Co., Ltd., measurements were taken at five points per film, for a total of three films, for a total of 15 points, and the average value was calculated.

[0070] (4) Heat Shrinkage at 150°C Strip samples 150 mm long and 20 mm wide are cut out in the machine direction and width direction, respectively. Two marks are made at 100 mm intervals along the length of each sample, and the distance A between the two marks is measured under no load. Next, one side of each strip sample is hung with a clip under no load from a basket, and placed in a gear oven in an atmosphere of 150°C, while the time is measured. After 30 minutes, the basket is removed from the gear oven and left at room temperature for 30 minutes. Next, the distance B is read for each sample under no load. From the read distances A and B, the heat shrinkage of each sample at 150°C is calculated using the following formula: Heat Shrinkage (%) = ((A - B) / A) x 100

[0071] (5) Melting point (Tm) of raw material (substance) Using a differential scanning calorimeter (DSC3100S, manufactured by Mac Science), approximately 5 mg of the film of each example was placed in a sample pan, the pan was covered, and the temperature was increased from room temperature to 300°C at a heating rate of 20°C / min in a nitrogen gas atmosphere. The melting point was determined as the melting peak temperature (Tpm) defined in JIS-K7121-1987, Section 9.1.

[0072] (6) Refractive Index (Ny, Nz) The refractive index in the flow direction (Nx) and the refractive index in the width direction (Ny) were measured using an Abbe refractometer with sodium D line (wavelength 589 nm) as a light source.

[0073] (7) Storage Modulus (E') Using a dynamic viscoelasticity measuring device (DVA225, manufactured by IT Measurement Control Co., Ltd.), the storage modulus (E') at 100°C in the machine direction (MD) and the transverse direction (TD) was determined under the following conditions.

[0074] (a) Sample width: 5 mm (b) Measurement temperature range: -50 to 250°C (c) Frequency: 10 Hz (d) Heating rate: 5°C / min

[0075] (8) Specific Heat Difference ΔCp at Glass Transition Temperature Using a temperature-modulated DSC manufactured by TA Instruments, 5 mg of sample was measured under a nitrogen atmosphere from 0°C to 150°C at a heating rate of 2°C / min, a temperature modulation amplitude of ±1°C, and a temperature modulation period of 60 seconds. The specific heat difference ΔCp (unit: J / (g°C)) at the glass transition temperature was calculated from the reversible curve obtained in the range from 0°C to 150°C. Specifically, in the stepwise change portion of the glass transition in a differential scanning calorimetry chart according to JIS K7121 (1987) obtained from the reversible curve, the glass transition temperature was determined from the point where a line equidistant in the vertical direction from each extended baseline intersected with the curve of the stepwise change portion of the glass transition, and the glass transition temperature was determined from the distance between the two lines extending each of the baselines at the glass transition temperature. The measurement was performed three times, and the average value was calculated.

[0076] (9) Density: Density was measured by the sink-float method at 25°C using a density gradient tube containing an aqueous calcium nitrate solution.

[0077] (10) Low-Temperature Formability After printing on the film, it was heated at 80°C for 5 seconds and then press-molded at a mold temperature of 80°C with a pressure holding time of 5 seconds. ABS resin was poured into the molding material at 210°C (injection molding) to produce a 3.0 mm high key top whose surface was covered with a film. The print misalignment at this time was measured, and the molding state was visually observed and ranked according to the following criteria. ◎ and ○ were considered acceptable, and × was considered unacceptable. ◎: The print misalignment was 0.1 mm or less, and the appearance was extremely good. ○: The print misalignment was 0.1 mm to 0.2 mm, and some wrinkles were observed, but this was at a level that was not problematic for practical use. ×: The print misalignment exceeded 0.2 mm. Alternatively, breaks were observed in the film. Alternatively, large wrinkles were observed, resulting in a significantly poor appearance.

[0078] (11) High-Temperature Formability After printing on the film, it was heated at 130°C for 5 seconds, and then press-molded at a mold temperature of 80°C with a pressure holding time of 5 seconds. ABS resin was poured into the molding material at 210°C (injection molding) to produce a 3.0 mm high keytop whose surface was covered with a film. The print misalignment at this time was measured, and the molding state was visually observed and ranked according to the following criteria. ◎ and ○ were considered acceptable, and × was considered unacceptable. ◎: The print misalignment was 0.1 mm or less, and the appearance was extremely good. ○: The print misalignment was 0.1 mm to 0.2 mm, and some wrinkles were observed, but this was at a level that was not problematic for practical use. ×: The print misalignment exceeded 0.2 mm. Alternatively, breaks were observed in the film. Alternatively, large wrinkles were observed, resulting in a significantly poor appearance.

[0079] (12) Solvent Resistance A sample was immersed in toluene adjusted to 25°C for 30 minutes, and the change in appearance before and after immersion was judged according to the following criteria, with ○ being considered as passing. The haze value was measured by the method described above. ○: Almost no change in appearance, and the change in haze value was less than 1%. ×: A change in appearance was observed, or the change in haze value was 1% or more.

[0080] (13) Heat Resistance The biaxially stretched film was heated at 100°C for 10 hours, and the tensile breaking strengths in the machine direction and width direction of the obtained sample were measured and ranked according to the following criteria. ◯ was evaluated as pass, and × was evaluated as fail. ◯: The value obtained by subtracting the sum of the tensile breaking strengths in the machine direction and width direction after heating from the sum of the tensile breaking strengths in the machine direction and width direction before heating was less than 70 MPa. ×: The value obtained by subtracting the sum of the tensile breaking strengths in the machine direction and width direction after heating from the sum of the tensile breaking strengths in the machine direction and width direction before heating was 70 MPa or more.

[0081] (14) Tensile Breaking Strength A sample was cut into a strip shape with a length of 180 mm and a width of 15 mm in the biaxially stretched machine direction and the width direction, respectively, using a single-edged razor. Next, the strip-shaped sample was pulled using a tensile tester (manufactured by Instron Corporation), and the breaking strength (MPa) in each direction was determined from the obtained load-strain curve. The measurement was carried out in an atmosphere of 25°C, with a chuck distance of 100 mm and a pulling speed of 200 mm / min. This measurement was carried out 10 times, and the average value was used.

[0082] Example 1: Chips (A) of a copolymer polyester having an intrinsic viscosity of 0.68 dL / g, which is composed of 100 mol% terephthalic acid units as an aromatic dicarboxylic acid component and 78 mol% ethylene glycol units and 22 mol% diethylene glycol units as diol components, chips (B) of polyethylene terephthalate having an intrinsic viscosity of 0.62 dL / g, and chips (C) of polyethylene terephthalate having an intrinsic viscosity of 0.62 dL / g and containing 2.7 mass% amorphous silica having an average particle size (SEM method) of 1.3 μm were dried. Furthermore, chips (A), chips (B), and chips (C) were mixed in a mass ratio of 77.3:22.5:0.2 (Mixed Raw Material 1). Furthermore, chips (A), chips (B), and chips (C) were mixed in a mass ratio of 77.3:19.9:2.8 (Mixed Raw Material 2). Next, mixed raw material 1 was melt-extruded at 270°C through a slit in a T-die using separate extruders so that mixed raw material 1 would form a 92% by mass base layer and mixed raw material 2 would form surface layers of 4% by mass on each of both surfaces of the base layer (a two-kind, three-layer structure of surface layer X / base layer Y / surface layer X), and the extruded material was rapidly cooled and solidified on a chill roll with a surface temperature of 20°C. At the same time, an amorphous, unstretched sheet was obtained by adhering the extruded material to the chill roll using an electrostatic application method.

[0083] The resulting unstretched sheet was stretched 3.45 times in the machine direction between a heating roll and a cooling roll at 115°C. The uniaxially stretched film was then introduced into a tenter, preheated at 105°C for 16 seconds, and transversely stretched 3.4 times at 120°C. The film was then heat-treated at 203°C and relaxed 5% in the transverse direction to obtain a biaxially stretched polyester film having a thickness of 25 µm.

[0084] Example 2 In Example 1, a biaxially oriented polyester film was obtained in the same manner as in Example 1, except that mixed raw material 1 was a mixture of chips (A), chips (B), and chips (C) in a mass ratio of 90.9:8.9:0.2, and mixed raw material 2 was a mixture of chips (A), chips (B), and chips (C) in a mass ratio of 90.9:6.3:2.8.

[0085] Comparative Example 1 In Example 1, mixed raw material 1 was prepared by mixing chips (A), chips (B), and chips (C) in a mass ratio of 95.5:4.3:0.2, and mixed raw material 2 was prepared by mixing chips (A), chips (B), and chips (C) in a mass ratio of 95.5:1.7:2.8. Biaxially oriented polyester films were obtained in the same manner as in Example 1, except that the heat treatment temperature of the film after tenter stretching was 190°C.

[0086] Comparative Example 2 In Example 1, a biaxially oriented polyester film was obtained in the same manner as in Example 1, except that mixed raw material 1 was prepared by mixing chips (A), chips (B), and chips (C) in a mass ratio of 59.1:40.7:0.2, and mixed raw material 2 was prepared by mixing chips (A), chips (B), and chips (C) in a mass ratio of 59.1:38.1:2.8.

[0087] Comparative Example 3 In Example 1, a biaxially oriented polyester film was obtained in the same manner as in Example 1, except that mixed raw material 1 was prepared by mixing chips (A), chips (B), and chips (C) in a mass ratio of 40.9:58.9:0.2, and mixed raw material 2 was prepared by mixing chips (A), chips (B), and chips (C) in a mass ratio of 40.9:56.3:2.8.

[0088] Comparative Example 4 A biaxially stretched polyester film was obtained in the same manner as in Example 2, except that the heat treatment temperature of the film after tenter stretching was 180°C.

[0089] Example 3 Chips (A), (B), and (C) were each dried. Furthermore, chips (A), chips (B), and chips (C) were mixed in a mass ratio of 63.6:35.9:0.5 (mixed raw material 1). Furthermore, chips (A), chips (B), and chips (C) were mixed in a mass ratio of 63.6:33.6:2.8 (mixed raw material 2). Next, mixed raw material 1 was melt-extruded at 270 ° C. through a T-die slit by an extruder so that 84 mass % of the mixed raw material was used as a base layer, and mixed raw material 2 was used as a surface layer on both surfaces of the base layer, each of which accounted for 8 mass % (A / B / A structure). The mixture was rapidly solidified on a chill roll at a surface temperature of 20 ° C., and simultaneously adhered to the chill roll using an electrostatic application method to obtain an amorphous unstretched sheet.

[0090] The resulting unstretched sheet was stretched 3.45 times in the machine direction between a heating roll and a cooling roll at 115°C. The uniaxially stretched film was then introduced into a tenter, preheated at 105°C for 16 seconds, and transversely stretched 3.4 times at 120°C. The film was then heat-treated at 203°C and relaxed 5% in the transverse direction to obtain a biaxially stretched polyester film having a thickness of 12 µm.

[0091] Example 4 Chips (A), (B), and (C) were each dried. Furthermore, chips (A), chips (B), and chips (C) were mixed in a mass ratio of 63.6:36.2:0.2 (mixed raw material 1). Furthermore, chips (A), chips (B), and chips (C) were mixed in a mass ratio of 63.6:33.6:2.8 (mixed raw material 2). Next, mixed raw material 1 was melt-extruded at 270 ° C. through a T-die slit by an extruder so that 92 mass % of the mixed raw material was used as a base layer, and mixed raw material 2 was used as a surface layer on both surfaces of the base layer, each of which accounted for 4 mass % (A / B / A structure). The mixture was rapidly solidified on a chill roll at a surface temperature of 20 ° C., and simultaneously adhered to the chill roll using an electrostatic application method to obtain an amorphous unstretched sheet.

[0092] The resulting unstretched sheet was stretched 3.45 times in the machine direction between a heating roll and a cooling roll at 115°C. The uniaxially stretched film was then introduced into a tenter, preheated at 105°C for 16 seconds, and transversely stretched 3.4 times at 120°C. The film was then heat-treated at 203°C and relaxed 5% in the transverse direction to obtain a biaxially stretched polyester film having a thickness of 25 µm.

[0093] Example 5 Chips (A), (B), and (C) were each dried. Furthermore, chips (A) and chips (B) were mixed in a mass ratio of 63.6:36.4 (mixed raw material 1). Furthermore, chips (A), chips (B), and chips (C) were mixed in a mass ratio of 63.6:33.6:2.8 (mixed raw material 2). Next, mixed raw material 1 was melt-extruded at 270 ° C. through a T-die slit by an extruder so that 99% by mass of the base layer and mixed raw material 2 were formed into 0.5% by mass of each surface layer on both surfaces of the base layer (a two-type, three-layer structure of A / B / A configuration), and then rapidly cooled and solidified on a chill roll at a surface temperature of 20 ° C. At the same time, an amorphous unstretched sheet was obtained by adhering the mixture to the chill roll using an electrostatic application method.

[0094] The resulting unstretched sheet was stretched 3.45 times in the machine direction between a heating roll and a cooling roll at 115°C. The uniaxially stretched film was then introduced into a tenter, preheated at 105°C for 16 seconds, and transversely stretched 3.4 times at 120°C. The film was then heat-treated at 203°C and relaxed 5% in the transverse direction to obtain a biaxially stretched polyester film having a thickness of 188 µm.

[0095] Example 6 A biaxially stretched polyester film was obtained in the same manner as in Example 4, except that the transverse stretching ratio was 3.2 times.

[0096] Comparative Example 5 A biaxially stretched polyester film was obtained in the same manner as in Example 4, except that the transverse stretching ratio was 3.0 times.

[0097] Comparative Example 6 A biaxially stretched polyester film was obtained in the same manner as in Example 4, except that the transverse stretching ratio was 3.7 times.

[0098] Example 7 A biaxially stretched polyester film was obtained in the same manner as in Example 4, except that the longitudinal stretching ratio was 3.9 times.

[0099] Example 8 A biaxially stretched polyester film was obtained in the same manner as in Example 4, except that the longitudinal stretching ratio was 4.1 times.

[0100] Comparative Example 7 A biaxially stretched polyester film was obtained in the same manner as in Example 4, except that the longitudinal stretching ratio was 3.2 times.

[0101] Comparative Example 8 A biaxially stretched polyester film was obtained in the same manner as in Example 4, except that the longitudinal stretching ratio was 4.3 times.

[0102] The results of evaluations of the biaxially stretched polyester films obtained in the above Examples and Comparative Examples, together with the production conditions, are shown in Table 1. The molar ratio of diethylene glycol in Table 1 is a value calculated as the molar ratio (mol %) of diethylene glycol when the total diol components constituting the entire polyester, including the copolymerized polyester, contained in the base layer and the surface layer is taken as 100 mol %.

[0103]

[0104] As shown in Table 1, in each Example, good results were obtained in the evaluations of low-temperature moldability, high-temperature moldability, solvent resistance, heat resistance, volume reduction property, and the like.

[0105] In Comparative Example 1, the molar ratio of diethylene glycol was increased compared to Example 2, resulting in Nx and Ny values ​​of less than 1.570, which resulted in no stress being generated at the mold corners during high-temperature molding, resulting in poor uniform moldability. Furthermore, in Comparative Example 1, ΔCp exceeded 0.20 J / (g ° C), the shrinkage rate over time increased, and wrinkles were observed in the film roll over time.

[0106] In Comparative Example 2, the molar ratio of diethylene glycol was reduced compared to Example 4, resulting in a storage modulus of more than 700 MPa and poor low-temperature moldability.

[0107] In Comparative Example 3, the molar ratio of diethylene glycol was reduced compared to Comparative Example 2. As a result, Ny exceeded 1.650, Nx / Ny was less than 0.995, and molding spots occurred during low-temperature and high-temperature molding. In addition, ΔCp was less than 0.12, shrinkage stress was high, and peeling was observed at the edge of the molded product.

[0108] In Comparative Example 4, the heat setting temperature was lower than in Example 2, and as a result, the heat shrinkage rate at 150°C exceeded 3.0%, and printing misalignment during high-temperature molding became significant.

[0109] In Comparative Example 5, the transverse draw ratio was lower than in Example 6, and as a result, Nx / Ny exceeded 1.005, and molding unevenness occurred in both the longitudinal and transverse directions during low-temperature and high-temperature molding.

[0110] In Comparative Example 6, the transverse draw ratio was increased compared to Example 4, resulting in an Nx / Ny ratio of less than 0.995, and molding unevenness occurred in both the longitudinal and transverse directions during low-temperature and high-temperature molding.

[0111] In Comparative Example 7, the longitudinal stretching ratio was lower than in Example 4, resulting in an Nx / Ny ratio of less than 0.995, and molding unevenness occurred in both the longitudinal and transverse directions during low-temperature and high-temperature molding.

[0112] In Comparative Example 8, the longitudinal draw ratio was increased compared to Example 8, resulting in Nx of 1.65 or more, a storage modulus of more than 700 MPa, and poor low-temperature and high-temperature moldability.

[0113] The polyester film for molding of the present invention has excellent moldability during heat molding at low temperatures and pressures, even though it is thin, and is therefore applicable to a wide range of molding methods. When used as a molded product at room temperature, it has excellent elasticity and heat shrinkage properties, as well as excellent solvent resistance and heat resistance, and is environmentally friendly. Furthermore, because of its high transparency, it is suitable for three-dimensional decoration methods in which a printability-improving layer of the film is provided with a design such as a printed layer or a pattern layer by various printing and decoration methods such as letterpress printing, intaglio printing, lithographic printing, screen printing, offset printing, gravure printing, inkjet printing, and flexographic printing, or by decorative methods such as textile printing, transfer printing, coating, painting, vapor deposition, sputtering, CVD, and lamination, and then molded by various molding methods such as mold molding, compressed air molding, and vacuum molding. Furthermore, it has excellent in-mold moldability and embossing moldability. Therefore, the material is suitable for use as housings or components for portable devices such as mobile phones, audio equipment, portable players / recorders, IC recorders, car navigation systems, and PDAs, as well as for notebook PCs, nameplate components for home appliances and automobiles, and building materials, and is making a great contribution to industry.

Claims

1. A polyester film for molding having a base layer and a surface layer on one or both sides of the base layer, which satisfies the following (1) to (5): (1) The storage modulus (E') in both the machine direction and the width direction is 10 to 700 MPa at 100°C, (2) The refractive index Nx in the machine direction and the refractive index Ny in the width direction are both 1.650 to 1.570, and Nx / Ny satisfies the relationship 0.995≦Nx / Ny≦1.005, and (3) The density is 1.365 to 1.385 g / cm ３ (4) The thermal shrinkage rate at 150°C in the machine direction and width direction is 0.01 to 3.0%. (5) The specific heat difference ΔCp at the glass transition temperature in temperature modulated DSC is 0.12 to 0.20 J / (g °C).

2. The polyester film for molding according to claim 1, which has a haze of 0.1 to 3.0%.

3. The polyester film for molding according to claim 1, wherein at least one of the base layer and the surface layer contains a copolymerized polyester, the dicarboxylic acid component constituting the copolymerized polyester is an aromatic dicarboxylic acid, and the diol component contains only ethylene glycol and diethylene glycol.

4. The polyester film for molding according to claim 3, wherein the base layer and the surface layer contain the copolymerized polyester, and diethylene glycol accounts for 14 to 20 mol % when the total diol component constituting the entire polyester, including the copolymerized polyester, contained in the base layer and the surface layer is taken as 100 mol %.

5. The polyester film for molding according to claim 1, wherein the thickness of the surface layer is 0.01 to 3 μm.

6. The polyester film for molding according to claim 1, wherein the surface layer contains particles, the average particle size of the particles is 0.01 to 6 μm, and the particle content in the surface layer is 0.01 to 25 mass %.

7. A method for producing a molded product, comprising molding a film-like or block-like molded product using the polyester film for molding according to any one of claims 1 to 6.

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