JP5450941B2 - Biaxially stretched laminated polyester film for molding - Google Patents

Description

  The present invention relates to a biaxially stretched laminated polyester film for molding processing, and more particularly, it is useful for a base film for applications where a resin such as ink is applied to the film and the thickness of the ink is required to be precisely controlled. The present invention relates to a biaxially stretched laminated polyester film for molding process that extends uniformly over the entire film and has small thickness unevenness after molding process.

  In recent years, the emphasis is placed on the design of furniture, interior decorations, electrical appliances, automobiles, etc., and it is very important to give a design to the surface of three-dimensional resin molded parts used for these. . As a method for decorating the surface of a three-dimensional resin molded part, there are a direct printing method and a transfer method. The direct printing method is a method of directly printing on a molded part, and includes a pad printing method, a curved silk printing method, an electrostatic printing method, and the like. However, these methods are unsuitable for the production of molded parts having complicated shapes, and it is difficult to impart a high degree of design. On the other hand, the transfer method includes a thermal transfer method and a water transfer method. These methods tend to be relatively expensive.

  In order to solve these problems, a molding method such as a simultaneous molding decoration method is known as a method for imparting design properties to a three-dimensional resin molded part at a low cost. In this method, a sheet or film such as a printed polyester resin (for example, Patent Document 1), a polycarbonate resin (for example, Patent Document 2), or an acrylic resin (for example, Patent Document 3) is previously three-dimensionally formed by vacuum forming or the like. This is a method of inserting into a molding die after molding into a shape or without molding, and then injection molding a molding resin. Thereby, the design formed on the film can be imparted to the molded part, and is sometimes referred to as insert molding, injection molding, or the like. In simultaneous molding decoration, a resin sheet or film and a molding resin may be integrated, or only printing may be transferred.

In the simultaneous molding and decorating method, depending on the characteristics of the film serving as the substrate, the design of the resin molded part may not be sufficient, and an optimal substrate film is required.
For example, in the processability of the base film disclosed in Patent Document 1, sufficient designability may not be obtained unless the resin molded part has a relatively simple shape. In addition, a high load is required to mold the film, and therefore, it is necessary to reduce the resin injection speed, which may not be sufficient in terms of productivity.
In addition, when the films disclosed in Patent Document 2 and Patent Document 3 are used as a base film, they are unstretched films, and therefore do not have the same solvent resistance as biaxially stretched polyester films. May be whitened and deteriorated, and at the same time it is opaque and not economical because of the thick film. In addition, the base film obtained by these methods has poor thickness unevenness, resulting in resin thickness unevenness such as ink coated on the base film, and for example, the color shading may be uneven. In addition, if the surface of the base film is rough, the printing tends to be unclear, and when transferring, the base film roughness is transferred and the transferred appearance may be inferior.

  On the other hand, as a polyester film for insert molding, for example, Patent Document 4 discloses a film in which the design of the molded product is not distorted, is excellent in low-temperature moldability during heat molding, and the finished quality of the molded product is improved. . Such a film is a biaxially stretched film in which a printability improving layer containing an adhesion modifying resin is provided on at least one side of a copolymerized polyester film, and the base film portion made of the copolymerized polyester is a single layer film. . In such a film, since the whole film has an orientation structure, the stress at the time of stretching (for example, F100 at 100 ° C.) is high, so that the followability to the mold may not be sufficient.

  In addition, as an example of an in-mold molding polyester film having good processability and good appearance, in Patent Document 5, the elongation at break at 100 ° C. is 200 to 600%, the break stress is 3 to 30 MPa, and the stress at 100% elongation is 100%. A film having a surface roughness of 2 to 20 MPa and a surface roughness of at least one side is disclosed. On the other hand, a film having such characteristics is excellent in moldability even under conditions where the injection speed is high and injection pressure is high. However, since there are many amorphous regions, local necking phenomenon tends to occur, and resin such as ink In applications where it is required to precisely control the thickness of the ink, the thickness unevenness may not be sufficient.

JP 2001-354843 A JP 2002-234955 A JP 2002-80678 A Japanese Patent Application Laid-Open No. 2005-205881 JP 2006-281732 A

  The object of the present invention is to solve the problems of the prior art, have excellent molding processability, apply a resin such as ink on the film, and use for controlling the thickness of the ink precisely. Designed when used as a transfer foil film with a small thickness variation of resin such as ink applied when used as a base film for molding processing, and with a design for molding processing applications such as molding simultaneous decoration method An object of the present invention is to provide a biaxially stretched laminated polyester film for molding process that extends uniformly over the entire area of the film so as not to cause a shift and has a small thickness variation of the film after molding process.

  As a result of diligent studies to solve the above problems, the present inventor, from the viewpoint of improving molding processability, from a non-oriented polyester layer and an oriented polyester layer provided on both sides in contact with this layer In order to develop an elongation mechanism that stretches uniformly throughout the entire film, instead of the elongation mechanism like the necking phenomenon that stretches locally in the molding process, the elongation is 100%. The present inventors have found that the stress at the time of elongation at a predetermined elongation until reaching the above has an effect and completed the present invention.

That is, according to the present invention, an object of the present invention is a biaxially stretched laminated polyester film comprising a non-oriented polyester layer B and an oriented polyester layer A provided on both sides in contact with the layer. The main component of the polyester A constituting the polyester layer A is ethylene terephthalate, the polyester B constituting the polyester layer B is copolymerized polyethylene terephthalate containing 10 to 30 mol% of a copolymer component based on the total acid components, and The melting point of polyester A is 15 ° C. higher than the melting point of polyester B, the stress at 10% elongation at 100 ° C. in the longitudinal direction or the width direction of the laminated polyester film, and 50% elongation at 100 ° C. Relationship between stress and stress at 100% elongation at 100 ° C and fracture at 100 ° C Degrees is achieved by the forming processing biaxially oriented laminated polyester film and satisfies the following formulas (1) to (5).
7 MPa ≦ F50−F10 ≦ 30 MPa (1)
5 MPa ≦ F100−F50 ≦ 25 MPa (2)
19 MPa ≦ F100 ≦ 70 MPa (3)
100% ≦ EB ≦ 400% (4)
7 MPa ≦ F10 ≦ 17 MPa (5)
(In the above formula, F10 is 10% elongation stress at 100 ° C. (unit: MPa), F50 is 10
Stress at 50% elongation at 0 ° C (unit: MPa), F100 is 100% at 100 ° C
(Elongation stress (unit: MPa), EB represents elongation at break (unit:%) at 100 ° C.)

Moreover, as for the biaxially stretched laminated polyester film for molding processing of the present invention, as a preferred embodiment, the copolymer component constituting the polyester B is isophthalic acid, naphthalenedicarboxylic acid, neopentyl glycol, 1,4-cyclohexanedimethanol and diethylene glycol. At least one selected from the group consisting of :
The thing which comprises is also included.
Further, the present invention provides a polyester layer B composed of polyester B and a polyester layer composed of polyester A provided on both sides in contact with this layer when producing the above-described biaxially stretched laminated polyester film for molding. A production method is included in which a laminated polyester film composed of A is subjected to a heat setting treatment at a temperature lower than the melting point of polyester A and a melting point of polyester B from Tm−3 ° C. to Tm + 8 ° C.

  According to the present invention, the biaxially stretched laminated polyester film of the present invention extends uniformly over the entire film and has a small thickness unevenness after molding. Therefore, a resin such as ink is applied on the film, and the ink When used as a base film for molding processes such as applications where precise thickness control is required, the thickness variation of resin such as ink applied is small, and in molding applications such as the simultaneous molding method When used as a transfer foil film having a design, it has a feature that does not cause a design shift, and can be suitably used as a base film for such a molding process.

Hereinafter, the present invention will be described in detail.
[Polyester layer A]
The polyester layer A is an oriented structure layer, the main component of the polyester A constituting the polyester layer A is ethylene terephthalate, and the melting point of the polyester A is required to be 15 ° C. higher than the melting point of the polyester B. “Oriented structure” in the present invention means that the polyester layer A partially has a crystal structure, and specifically, a polarizing microscope with respect to a cross section in the TD direction (sometimes referred to as a width direction or a transverse direction) of the film. It means that the birefringence of the polyester layer A when measured using is 0.05 or more. Such birefringence is more preferably 0.07 or more, and still more preferably 0.08 or more.

  Specifically, the polyester A is a polyester in which the main dicarboxylic acid unit is a terephthalic acid unit and the main glycol unit is an ethylene glycol unit. Here, “main” refers to 80 mol% or more and 100 mol% or less based on the total acid component of polyester A, and in accordance with the melting point of polyester B, the amount of copolymer component may be relatively determined within this range. it can. Specific examples of polyester A include polyethylene terephthalate containing no copolymer component and polyethylene terephthalate obtained by copolymerizing a small amount of the third component.

  Examples of copolymer components include isophthalic acid, orthophthalic acid; naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid; 4,4′-biphenyldicarboxylic acid, 2 , 2-biphenyldicarboxylic acid and other bicarboxylic dicarboxylic acids, succinic acid, adipic acid, azelaic acid, sebacic acid and other carboxylic acid units may be contained, for example, diethylene glycol, propylene glycol, 1,4- It may contain other glycol units such as butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, polytetramethylene glycol and the like. . Among these copolymer components, preferably, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and diethylene glycol are exemplified, and not only one type but also two or more types may be used.

  The melting point of the polyester A of the present invention is preferably 205 to 255 ° C., and within this range, the melting point of the polyester B needs to be 15 ° C. or higher. The lower limit of the melting point of the polyester A is more preferably 230 ° C. or higher, and particularly preferably 235 ° C. or higher. The range of the melting point of the polyester A is achieved by a polyethylene terephthalate homopolymer or a polyethylene terephthalate obtained by copolymerizing a small amount of the above-described copolymer component.

The melting point of the polyester A constituting the polyester layer A needs to be at least 15 ° C. higher than the melting point of the polyester B constituting the polyester layer B, but is preferably 18 ° C. or more, particularly preferably 25 ° C. or more.
If the melting point difference is less than 15 ° C., it is difficult to optimize the temperature at which the heat treatment for making the polyester layer B non-oriented. That is, when the heat treatment temperature is lower than the melting point of the polyester B of the polyester layer B by a certain temperature or more, the polyester B is not sufficiently melted, so that the change to the non-oriented structure due to the heat treatment after stretching becomes insufficient. On the other hand, if the heat treatment temperature is too close to the melting point of the polyester A of the polyester layer A, the polyester A begins to melt in part, so that the orientation structure of the polyester layer A is destroyed and the polyester layer A extends over the entire film. In addition, since it does not have a uniform orientation structure, a local necking phenomenon occurs at the time of stretching, and the thickness unevenness of the film after molding processing is impaired, or the solvent resistance is impaired. Moreover, at the time of film manufacture, a film may become easy to cut | disconnect, and the film wound up in roll shape may melt | fuse.

The intrinsic viscosity of the polyester A of the present invention is preferably 0.60 to 1.00 dL / g. The lower limit of the intrinsic viscosity is more preferably 0.64 dL / g, and the upper limit is more preferably 0.90 dL / g. When the intrinsic viscosity of the polyester A is less than the lower limit, the film may be cut or a film thickness unevenness may occur in the molding process. On the other hand, when the intrinsic viscosity of the polyester A exceeds the upper limit, it becomes difficult to extrude the molten resin when forming a film, and as a result, productivity may be inferior, for example, by reducing the film forming speed.
The glass transition temperature of polyester A is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, from the viewpoint of dimensional stability, deformation resistance, and curl resistance of the film and its processed product.

The melting point of polyester A in the present invention means the melting endothermic peak temperature when polyester A is once melted, then rapidly cooled and solidified, and the temperature is raised at a rate of 20 ° C./min with a differential calorimeter. .
The glass transition temperature of polyester A in the present invention is the structural change (specific heat change) when polyester A is once melted, then rapidly cooled and solidified, and the sample is heated at a rate of 20 ° C./min with a differential calorimeter. ) Temperature.

  You may make the polyester layer A of this invention contain an additive in the range which does not impair the objective of this invention. For example, components such as an elastomer resin such as polybutylene terephthalate-polytetramethylene glycol block copolymer, a pigment, a dye, a heat stabilizer, a flame retardant, a foaming agent, and an ultraviolet absorber may be included as necessary.

[Polyester layer B]
The polyester layer B is a layer having a non-oriented structure, and the polyester B constituting the polyester layer B is a copolymerized polyethylene terephthalate containing 10 to 30 mol% of a copolymer component based on the total acid component, and the melting point of the polyester B Is required to be 15 ° C. or more lower than the melting point of polyester A. The “non-oriented structure” in the present invention means that the polyester layer B does not have a crystal structure but has an amorphous structure. Specifically, the cross section in the TD direction of the film is measured using a polarizing microscope. In this case, the birefringence of the polyester layer B is less than 0.05. Such birefringence is more preferably 0.04 or less, and still more preferably 0.03 or less.

  The non-oriented structure may be one in which the non-oriented structure is expressed by applying a heat treatment at a temperature close to the melting point of the polyester layer B after the oriented structure is once formed in the film stretching process. It may be a case where it has a non-oriented structure without being crystallized. That is, the polyester B constituting the polyester layer B may be a polyester capable of forming an oriented structure of the polymer by a stretching treatment, and any of the polyesters in which the polymer maintains a non-oriented structure even after the stretching treatment. It may be.

  Specifically, the polyester B is a polyester in which the main dicarboxylic acid unit is a terephthalic acid unit and the main glycol unit is an ethylene glycol unit. Here, “main” means 70 mol% or more and 100 mol% or less based on the total acid components of polyester B, and within such a range, the relative coexistence is satisfied so as to satisfy the melting point relationship between polyester A and B. The amount of polymerization component can be determined. Examples of copolymer components constituting polyester B include isophthalic acid, orthophthalic acid; naphthalenedicarboxylic acid such as 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid; 4,4′- It may contain other carboxylic acid units such as biphenyl dicarboxylic acid, biphenyl dicarboxylic acid such as 2,2-biphenyl dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, and diethylene glycol, propylene glycol, etc. Contains other glycol units such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, polytetramethylene glycol Even if There. Among these copolymer components, at least one selected from the group consisting of isophthalic acid, naphthalene dicarboxylic acid, neopentyl glycol, 1,4-cyclohexanedimethanol and diethylene glycol is particularly preferable, and isophthalic acid and naphthalene dicarboxylic are particularly preferable. It is preferably at least one selected from the group consisting of an acid, 1,4-cyclohexanedimethanol and diethylene glycol. As a specific embodiment of the copolymerization component of the polyester B of the present invention, the dicarboxylic acid component is any one of two types of isophthalic acid, naphthalene dicarboxylic acid, isophthalic acid and naphthalene dicarboxylic acid, and glycol copolymerization. The aspect which does not contain a component or is diethylene glycol is mentioned. In such a case, the total of dicarboxylic acid copolymerization components is preferably 8 to 30 mol%, and the total of glycol copolymerization components is 0 to 10 mol%. Further, as another specific embodiment of the copolymerization component of polyester B, the glycol component is one of 1,4-cyclohexanedimethanol, one of two types of 1,4-cyclohexanedimethanol and diethylene glycol, and dicarboxylic acid Examples include no copolymerization component or at least one of isophthalic acid and naphthalenedicarboxylic acid. In such a case, the glycol copolymerization component is preferably 8 to 30 mol% in total, and the dicarboxylic acid copolymerization component is 0 to 10 mol% in total.

  The melting point of the polyester B of the present invention is preferably 190 to 240 ° C., and needs to be 15 ° C. or more lower than the melting point of the polyester A within such a range. The lower limit of the melting point of the polyester B is more preferably 200 ° C. or higher, and particularly preferably 210 ° C. or higher. On the other hand, the upper limit of the melting point of polyester B is more preferably 230 ° C. or less, and particularly preferably 225 ° C. or less. The range of the melting point of the polyester B is achieved by copolymerized polyethylene terephthalate containing 10 to 30 mol% of the above-described copolymer component.

The melting point of the polyester B constituting the polyester layer B needs to be 15 ° C. or more lower than the melting point of the polyester A constituting the polyester layer B, but is preferably 18 ° C. or more, particularly preferably 25 ° C. or more.
The intrinsic viscosity of the polyester B of the present invention is preferably 0.60 to 1.00 dL / g. The lower limit of the intrinsic viscosity is more preferably 0.64 dL / g, and the upper limit is more preferably 0.90 dL / g. When the intrinsic viscosity of the polyester B is less than the lower limit, the film may be cut or a film thickness unevenness may occur in the molding process. On the other hand, when the intrinsic viscosity of polyester B exceeds the upper limit, it becomes difficult to extrude the molten resin when forming a film, and as a result, productivity may be inferior, for example, by reducing the film forming speed.

  The glass transition temperature of polyester B is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, from the viewpoint of dimensional stability, deformation resistance, and curl resistance of the film and its processed product. The difference between the glass transition temperature of the polyester A and the glass transition temperature of the polyester B is preferably 20 ° C. or less, more preferably 10 ° C. or less, and particularly preferably 5 ° C. or less in order to improve the thickness unevenness of the film. .

The melting point of polyester B in the present invention means the melting endothermic peak temperature when polyester B is once melted, then rapidly cooled and solidified, and the temperature is raised at a rate of 20 ° C./min with a differential calorimeter. .
The glass transition temperature of polyester B in the present invention is a change in structure (specific heat) when polyester B is once melted, then rapidly cooled and solidified, and the sample is heated at a rate of 20 ° C./min with a differential calorimeter. Change) refers to temperature.

  You may make the polyester layer B of this invention contain an additive in the range which does not impair the objective of this invention. For example, components such as an elastomer resin such as polybutylene terephthalate-polytetramethylene glycol block copolymer, a pigment, a dye, a heat stabilizer, a flame retardant, a foaming agent, and an ultraviolet absorber may be included as necessary.

[Inert particles]
The laminated polyester film for molding according to the present invention preferably contains at least two kinds of inert particles, and these inert particles are preferably contained in the polyester layer A on the surface. As the inert particles, inorganic fine particles such as silica, alumina, titanium oxide, calcium carbonate and kaolin, precipitated fine particles of catalyst residue, organic fine particles such as silicone, polystyrene cross-linked product and acrylic cross-linked product can be used.
As the inert particles, it is preferable to use two types of spherical particles, that is, spherical particles having an average particle size of 1.0 to 2.0 μm and spherical particles having an average particle size of 0.05 to 0.5 μm. By using these spherical particles in combination, the slipperiness, that is, the winding property and the handling property can be improved efficiently while maintaining the transparency of the film. By containing these inert particles only in the polyester layer A on the surface, very high transparency can be expressed.

[Stress at elongation and elongation at break at 100 ° C.]
The laminated polyester film for molding according to the present invention has a 10% elongation stress at 100 ° C, a 50% elongation stress at 100 ° C, and a 100% elongation at 100 ° C in at least one of the longitudinal direction and the width direction. It is necessary that the relationship between time stress and elongation at break at 100 ° C. satisfy the following formulas (1) to (4).
7 MPa ≦ F50−F10 ≦ 30 MPa (1)
5 MPa ≦ F100−F50 ≦ 25 MPa (2)
15 MPa ≦ F100 ≦ 70 MPa (3)
100% ≦ EB ≦ 400% (4)
(In the above formula, F10 is a stress at 10% elongation at 100 ° C. (unit: MPa), F50 is a stress at 50% elongation at 100 ° C. (unit: MPa), and F100 is a stress at 100% elongation at 100 ° C. (unit: MPa). MPa), EB represents the elongation at break at 100 ° C. (unit:%))

  Each elongation stress represented by F10, F50, and F100 was measured using a tensile tester in which the chuck portion was covered with a heating chamber. The inside of the heating chamber was kept at 100 ° C., the distance between chucks was 50 mm, and the tensile speed was 50 mm / min. 10%, 50%, and 100% of the load elongation curve are read at each elongation, and the tensile stress at the time of elongation (F10) (unit: MPa) is calculated by dividing by the sample cross-sectional area before tension. It is obtained by calculating the stress at 50% elongation (F50) (unit: MPa) and the stress at 100% elongation (F100) (unit: MPa). Further, the elongation at break at 100 ° C. can be obtained by reading the elongation at break of the load elongation curve.

The lower limit of the stress difference between F50 and F10 represented by the formula (1) is preferably 9 MPa or more, more preferably 10 MPa or more. Moreover, the upper limit of the stress difference of F50 and F10 represented by Formula (1) is 25 MPa or less.
Further, the stress difference between F100 and F50 represented by the formula (2) is preferably 6 MPa or more and 20 MPa or less.
When the relationship between F10, F50 and F100 is less than the lower limit represented by the formula (1) and the formula (2), the orientation of the polyester layer A constituting both outer layers of the laminated film is not sufficient, and the film is uniform. As a result, thickness unevenness occurs in the film after being processed without being stretched, resulting in poor thickness unevenness of resin such as ink applied on the film, resulting in color shading. On the other hand, when the relationship between F10, F50 and F100 exceeds the upper limit represented by the formulas (1) and (2), the polyester layer B constituting the core layer of the laminated film is oriented and stretched as a laminated film. Since the stress becomes too high, a high stress is required to deform the film in the molding process, resulting in poor moldability.

  The lower limit of the stress at 100% elongation (F100) at 100 ° C. of the laminated polyester film for molding according to the present invention is preferably 19 MPa or more, more preferably 30 MPa or more. On the other hand, the upper limit of the stress at 100% elongation (F100) at 100 ° C. of the laminated polyester film for molding is preferably 60 MPa or less. When F100 is less than the lower limit, the orientation of the polyester layer A constituting both outer layers of the laminated film is not sufficient, and the film after being formed and processed without being stretched uniformly results in thickness spots on the film. The thickness unevenness of the resin such as the coated ink is deteriorated, and color shading is generated. On the other hand, when F100 exceeds the upper limit, in the process of forming the film, very high stress is required to deform the film, resulting in inferior forming processability.

  The lower limit of the breaking elongation at 100 ° C. of the laminated polyester film for molding is preferably 150% or more. When the elongation at break at 100 ° C. is less than the lower limit, it means that the moldability is low, and the film may be broken when forming a complex shape or a deep shape. On the other hand, the higher elongation at break at 100 ° C. is preferred, but the biaxially stretched laminated polyester film of the present invention is represented by the formulas (1) to (3) for the purpose of uniformly stretching the entire film. Since the orientation of the polyester layer A is controlled so as to have such elongation stress, the upper limit of the elongation at break is 400%, further 300%.

  The relationship between each elongation stress and breaking elongation at 100 ° C. represented by the above formulas (1) to (4) is referred to as the longitudinal direction of the biaxially stretched laminated polyester film (film continuous film-forming direction, longitudinal direction or MD direction). May be satisfied in at least one of the width direction (sometimes referred to as a horizontal direction or a TD direction), but it is preferable to satisfy the relationships of the expressions (1) to (4) in the width direction.

  In order to bring the relationship between the stresses at the time of elongation into the above-mentioned range, a polyester layer B made of polyester B with an unoriented structure and an oriented structure polyester layer made of polyester A provided on both sides in contact with this layer A biaxially stretched laminated polyester film comprising A is used, and the laminated polyester film is biaxially stretched at a stretch ratio of 3.4 times to 4.1 times, preferably 3.7 times to 4.1 times in at least one direction. After film formation, the layer B is melted and heat setting is performed to such an extent that the layer A is not excessively crystallized. The heat setting temperature is at least 15 ° C. lower than the melting point of the polyester A and near the melting point of the polyester B. That is, the melting point of polyester B is from Tm−3 ° C. to Tm + 8 ° C., preferably the melting point of polyester B is from Tm to Tm + 5 ° C. Can.

[Layer structure of film]
The laminated polyester film for molding according to the present invention has a laminated structure comprising a polyester layer B and a polyester layer A provided on both sides in contact with this layer, and A / B / A (where / is the layer A three-layer structure of the type shown) is shown as the smallest unit. The laminated polyester film for molding according to the present invention may have a structure in which B / A is further provided as long as it includes a three-layer structure of A / B / A. For example, a five-layer configuration of A / B / A / B / A type, and a seven-layer, nine-layer, and 2n + 1 (n is a natural number) configuration in these order may be used. Moreover, when making the polyester layer A into two or more layers, one or more layers can be comprised with a different polymer as needed. The same applies when the polyester layer B has two or more layers. For example, when the polyester layer A is composed of two types of polymers (A1, A2) and the polyester layer B is composed of two types of polymers (B1, B2), a three-layer configuration of A1 / B1 / A2 type, A1 / B1 / A2 / A B2 / A1 type five-layer structure may be adopted. Among these layer configurations, a three-layer configuration and a five-layer configuration are preferable, and a three-layer configuration is particularly preferable.

  In any layer configuration, it is necessary that the polyester layer A having an orientation structure biaxially stretched constitutes the outermost layer. When the polyester layer B having a non-oriented structure constitutes the outermost layer, there is a problem that the film tends to stick to various rolls in the process during film production.

[Film thickness]
The total thickness of the laminated polyester film for molding according to the present invention is preferably 30 to 300 μm, more preferably 40 to 200 μm, and particularly preferably 50 to 100 μm. If the total thickness of the film is less than the lower limit, the film is weak, and in the process of injecting the resin at the time of molding, problems such as breakage of the film due to the pressure of the injection resin easily occur. Further, in this step, problems that the film is wrinkled are likely to occur, and at the same time, these problems may cause a defect of resin such as ink coated on the film. On the other hand, if the total thickness of the film exceeds the upper limit, the stiffness of the film is too strong and the load required during molding processing increases, so it is necessary to increase the extrusion pressure of the injection resin or slow down the injection speed. As a result, productivity may be inferior.

Moreover, it is preferable that the total thickness ratio (a / b) of the polyester layer A and the polyester layer B which comprises the laminated polyester film for shaping | molding of this invention is the range represented by following formula (1).
0.01 ≦ total thickness ratio (a / b) ≦ 1 (1)
(In the above formula, a represents the total thickness (μm) of the polyester layer A, and b represents the total thickness (μm) of the polyester layer B.)

  The lower limit of the total thickness ratio (a / b) of the polyester layer A and the polyester layer B is more preferably 0.03 or more, still more preferably 0.05 or more, and particularly preferably 0.10 or more. The upper limit of the total thickness ratio (a / b) of the polyester layer A and the polyester layer B is more preferably 0.67 or less, further preferably 0.43 or less, and particularly preferably 0.20. When the total thickness ratio (a / b) of the polyester layer A and the polyester layer B is less than the lower limit, the thickness ratio at the time of film production may be difficult because the ratio of the polyester layer A is small. Stability may be insufficient. On the other hand, when the total thickness ratio (a / b) of the polyester layer A and the polyester layer B exceeds the upper limit, the workability of the film may be insufficient due to a small proportion of the polyester layer B having an amorphous structure. .

[Film thickness unevenness]
In the laminated polyester film for molding according to the present invention, the thickness unevenness of the film is preferably 7.0% or less, more preferably 6.0% or less in both the film longitudinal direction and the width direction. When the thickness unevenness of the film exceeds the upper limit, the thickness unevenness of the resin such as the ink applied on the film is bad, and in the case of the ink, it becomes unevenness of color. On the other hand, the thickness unevenness of the film is preferably smaller within such a range, but in order to make the thickness unevenness of the film smaller, it is necessary to stretch the film at a higher stretch ratio, and the stress at the time of stretching becomes too high to be formed. Since workability may be reduced, the lower limit is preferably 2.0% or more.
Here, the thickness unevenness of the film refers to the thickness unevenness of the film after biaxially stretching and heat-setting the unstretched laminated film, and using a dot-type thickness measuring device, the film length direction is 2 m, and the film width direction is 3 m. Thickness was measured by measuring the thickness at 100 points for each direction, the average value for each direction being the film thickness (unit: μm), and the difference between the maximum value and the minimum value divided by the film thickness. ).

Due to the range of thickness variations in the longitudinal and width directions of the laminated polyester film for molding, the molding processability is high, and the thickness variation after molding using the biaxially stretched laminated polyester film of the present invention is very Becomes smaller.
In order to obtain a laminated polyester film having such a film thickness unevenness, a non-oriented polyester layer B made of polyester B and an oriented polyester layer made of polyester A provided on both sides in contact with this layer A biaxially stretched laminated polyester film comprising A is used, and the laminated polyester film is biaxially stretched at a stretch ratio of 3.4 times to 4.1 times, preferably 3.7 times to 4.1 times in at least one direction. After film formation, the layer B is melted and heat setting is performed to such an extent that the layer A is not excessively crystallized. The heat setting temperature is at least 15 ° C. lower than the melting point of the polyester A and near the melting point of the polyester B. That is, the melting point of the polyester B is Tm-3 ° C to Tm + 8 ° C, preferably the melting point of the polyester B is Tm to Tm + 5 ° C. It is achieved by the.

[Center average surface roughness]
In the laminated polyester film for molding according to the present invention, it is preferable that the center line average surface roughness (Ra) of at least one surface is 0 nm or more and 20 nm or less. If the center line average surface roughness (Ra) of the film exceeds the upper limit, the roughness of the film surface is transferred to a resin such as ink coated on the film and the surface of the ink layer becomes rough. Inferior properties, and high quality printing may be difficult to obtain.
When the coating layer is coated on the polyester film, the upper limit of the center line average surface roughness including the coating layer is preferably 20 nm or less.

[Other film properties]
The initial haze of the laminated polyester film for molding according to the present invention is preferably 0% or more and 5% or less. Here, the initial haze refers to haze in a state where no additional heat treatment or the like is applied to the obtained film. The upper limit of the initial haze of the polyester film is more preferably 3% or less, and particularly preferably 2% or less. If the haze exceeds the upper limit, the design may become unclear when the film forms a layer on the outer side than the printed layer in an application in which the printed film and the molding resin are integrated. The haze of the polyester film itself is achieved by the type and amount of lubricant.

  The heat shrinkage ratio of the laminated polyester film for molding according to the present invention is preferably 0.0 to 3.0% at 150 ° C. for 30 minutes. If the heat shrinkage rate deviates from the range, the polyester film will be deformed when it is heated and molded, and if the design property is given by applying resin such as ink on the film, the position of the design May shift, or the resin such as coated ink may be peeled off or deformed.

[Production method]
Hereinafter, the manufacturing method of the laminated polyester film for simultaneous decorating of the present invention will be described by taking a laminated film having a three-layer structure of A / B / A as an example.
In the present invention, the polyester A constituting the polyester layer A and the polyester B itself constituting the polyester layer B can be produced by a known method. Specific examples include a method of reacting one or more dicarboxylic acid ester-forming derivatives with one or more glycols in the reaction step of polyester production. In the case of a copolyester, Examples thereof include a method of melt-mixing two or more kinds of polyesters using a single screw or twin screw extruder and transesterifying them (redistribution reaction). In these steps, various additives such as particles may be included in the polyester as necessary.

  The laminated film can be produced by a coextrusion film forming method. First, polyester A pellets prepared for the polyester layer A are dried and melted. In parallel with this, the pellets of polyester B prepared for the polyester layer B are dried and melted. Subsequently, these molten polymers are laminated in three layers inside the die. For example, the molten polymer is laminated in three layers inside the die provided with a feed block, and then cast on a cooling drum to form an unstretched multilayer film. Is biaxially stretched in the longitudinal and transverse directions to obtain a laminated biaxially stretched film in which at least the polyester layer A has a biaxially stretched orientation structure. In the case of 5 layers or more, it can be produced in the same manner.

  Next, a stretching treatment is performed. At that time, at least one of the longitudinal direction and the transverse direction is stretched in a range of 3.4 to 4.1 times, preferably in a range of 3.7 to 4.1 times. Do. As an example, when producing a film having the elongation stress and elongation at break according to the present invention in the width direction, the longitudinal stretching treatment is performed from Tg (glass transition temperature) −30 ° C. to Tg + 5 ° C. of the polyester A constituting the polyester layer A. After preheating at a temperature, the polyester A is stretched 2.7 to 3.3 times, preferably 2.9 to 3.1 times in the machine direction at a temperature of Tg-10 ° C to Tg + 50 ° C. Next, preheating is again performed at a temperature of Tg to Tg + 30 ° C. of polyester A, and the polyester A is stretched by 3.4 to 4.1 times in the transverse direction at a temperature of Tg + 30 to Tg + 70 ° C., preferably 3.7 to 4.1. Double. Thereby, the thickness unevenness of a film and a moldability can be made favorable simultaneously.

  It is necessary to subject the biaxially stretched laminated film thus obtained to a heat setting treatment. This heat setting treatment is performed at a temperature lower than the melting point of the polyester A and close to the melting point of the polyester B. The specific heat setting temperature is 15 ° C. or more lower than the melting point of the polyester A, the melting point of the polyester B is Tm−3 ° C. to Tm + 8 ° C., and more preferably the melting point of the polyester B is Tm to Tm + 5 ° C.

  Since the polyester layer B is in a temporarily melted state in the heat setting treatment step, even if a stretch orientation structure exists in the polyester layer B in the drawing step before the heat setting treatment, the polyester layer B has a substantially non-oriented structure. . Moreover, the polyester layer A can be crystallized to such an extent that the stress at the time of elongation of the present invention can be obtained without excessively crystallizing the polyester layer A by this heat setting treatment.

As the heat setting treatment method, for example, a method of performing heat treatment in the process immediately after stretching during film production, or a method of performing heat treatment after winding the film into a roll after completion of film production can be used, and the former is preferable. In the former method, the temperature during the heat setting treatment after the stretching treatment in the coextrusion film forming method may be set to the above heat treatment temperature.
By such a method, the biaxially stretched laminated polyester film for molding process of the present invention can be obtained.

(1) Birefringence index The birefringence is measured by the following method as an index for confirming the oriented structure and non-oriented structure of each film layer. That is, after embedding the cross section in the TD direction of the film sample in an epoxy resin, the epoxy resin was cured, and then the cross section was sliced to about 4 μm with a microtome, and the birefringence (Δn) was measured with a polarizing microscope. The orientation structure and non-orientation structure of each layer were determined based on the index.
A: 0.00 <Δn <0.03
B: 0.03 ≦ Δn <0.05
C: 0.05 ≦ Δn <0.07
D: 0.07 ≦ Δn <0.12

(2) Intrinsic viscosity Intrinsic viscosity ([η]) (unit: dL / g) was measured with an o-chlorophenol solution at 35 ° C. The intrinsic viscosity of the raw material is a measured value of the polyester raw material pellet, and the intrinsic viscosity of the polyester A and the polyester B constituting the polyester layer A and the polyester layer B is extruded from the die during the film forming process. Each resin was sampled individually and the measured value was used. The intrinsic viscosities of polyester A and polyester B may be measured by collecting each layer of the obtained laminated film. The intrinsic viscosity of the laminated polyester film is a measured value obtained by cutting a predetermined amount of the obtained laminated film.

(3) Copolymerization component amount It calculated | required from the < ¹ > H-NMR measurement about each layer of the film sample.

(4) Glass transition temperature, melting point, and crystallization energy (4-1) Polyester resin (Polyester A, Polyester B)
About 10 mg of each pellet sample of polyester A and polyester B is sealed in an aluminum pan for measurement and attached to a differential calorimeter (trade name “DSC2920 Modulated” manufactured by TA Instruments), and 25 ° C. to 20 ° C./min. The temperature was raised to 290 ° C. at a speed, held at 290 ° C. for 3 minutes, then taken out, immediately transferred onto ice and rapidly cooled. The pan was again attached to the differential calorimeter, and the temperature was raised from 25 ° C. to 20 ° C./min, and each glass transition temperature Tg (unit: ° C.) and melting point Tm (unit: ° C.) was measured.
In addition, about 10 mg of each sample may be collected from the polyester layer A and the polyester layer B, and Tg, Tm, and crystallization energy may be obtained under the same conditions.

(4-2) Laminated Polyester Film Approximately 20 mg of a sample of the entire laminated film is sealed in an aluminum pan for measurement and attached to a differential calorimeter (trade name “DSC2920 Modulated” manufactured by TA Instruments), and the temperature is from 25 ° C. to 20 ° C. The crystallization energy (unit: J / g) was measured by raising the temperature at a rate of ° C./min.

(5) Tensile stress at 100 ° C. and elongation at break 10%, 50%, and 100% elongation stress at 100 ° C. and elongation at break were measured by a tensile tester with the chuck portion covered with a heating chamber as a measuring device ( Measurement was performed using Toyo Baldwin, trade name “Tensilon”). From the obtained polyester film, samples of 100 mm in the longitudinal direction and 10 mm in the width direction were taken in the longitudinal direction (MD) and the transverse direction (TD), respectively, and fixed by being sandwiched between chucks set at an interval of 50 mm. At that time, the atmosphere in which the sample exists was kept at 100 ° C. by a heating chamber installed in the chuck portion of the tensile tester. Pulling was performed at a speed of 50 mm / min, and the load was measured with a load cell attached to the testing machine. Read 10%, 50%, and 100% of the load elongation curve at the time of elongation, and divide by the sample cross-sectional area before tension to obtain 10% elongation stress (F10) (unit: MPa), 50% elongation stress ( F50) (unit: MPa) and 100% elongation stress (F100) (unit: MPa) were calculated. Further, the elongation at break at 100 ° C. was obtained by reading the elongation at break.

(6) Film thickness and thickness unevenness
Using a dot-type thickness measuring instrument (manufactured by Anritsu Co., Ltd.), the thickness in the machine direction (MD) and the transverse direction (TD) of the film is measured under the following conditions, and the average value of each is measured for the film thickness (unit). : Μm), and a value obtained by dividing the difference between the maximum value and the minimum value by the film thickness was defined as thickness unevenness (unit:%) in each direction. Moreover, the film thickness of Table 1 showed the value which averaged the film thickness average value of the film vertical direction, and the film thickness average value of the film horizontal direction.
Sample length: Longitudinal direction (MD) 2 m, Lateral direction (TD) 3 m
Number of measurement points: 100 points each

(7) Thickness spots after molding
A sample of 10 cm × 10 cm was taken from the obtained biaxially stretched laminated polyester film, and the longitudinal direction (MD) was set to 1.0 in a 100 ° C. atmosphere using a film biaxial stretching device (manufactured by Imoto Seisakusho Co., Ltd.). While being fixed at double, it was stretched 1.5 times in the transverse direction (TD) to obtain a sample after molding. The film thickness of the obtained sample was measured using a dot-type thickness measuring instrument (manufactured by Anritsu Co., Ltd.), and a total of 100 points of data were obtained. Among the obtained data, the maximum thickness and the minimum thickness were obtained, and the difference was defined as the thickness unevenness (μm) after the molding process.

(8) Thickness of each layer The thicknesses of the polyester layer A and the polyester layer B are obtained by embedding a small piece of film in an epoxy resin (trade name “Epomount” manufactured by Refine Tech Co., Ltd.), and manufactured by Reichert-Jung. The embedded resin was sliced to a thickness of 50 nm using a Microtome 2050, and measured with an accelerating voltage of 100 KV using a transmission electron microscope (LEM-2000).

(9) Initial haze of film Using film sample, according to JIS K7105, using a haze measuring machine (Nippon Denshoku Industries Co., Ltd., product name "NDH-2000"), total light transmittance Tt (unit) :%) And the scattered light transmittance Td (unit:%) were measured, and the initial haze (unit:%) was calculated from the following equation.
Haze (%) = (Td / Tt) × 100

(10) Heat shrinkage rate In a hot air circulation type oven having an internal temperature of 150 ° C., a film sample with a rating of a fixed interval (about 30 cm) in the measurement direction was placed. The distance between the scores of the sample taken out after 30 minutes was measured, and the shrinkage rate was calculated by the following formula.
S = 100 × (L−L ₀ ) / L ₀
(S: heat shrinkage rate (unit:%), L: interval between scores after heat treatment (unit: mm), L ₀ : interval between scores before heat treatment (unit: mm))

なお、転写箔とする際は意匠を塗設する表面の中心線平均表面粗さを測定し、測定値とした。 (11) Centerline average surface roughness (Ra)
In accordance with JIS B0601, using a high-precision surface roughness meter SE-3FAT manufactured by Kosaka Laboratory, under the conditions of a needle radius of 2 μm, load of 30 mg, magnification of 200,000 times, and cutoff of 0.08 mm A chart is drawn, and the portion of the measurement length L is extracted from the surface roughness curve in the direction of the center line. The center line of the extracted portion is the X axis, the direction of the vertical magnification and the Y axis, and the roughness curve is Y = f When expressed by (x), the value given by the following formula (5) was expressed in nm. In this measurement, four pieces were measured with a reference length of 1.25 mm and expressed as an average value.

In addition, when setting it as transfer foil, the centerline average surface roughness of the surface which coats a design was measured, and it was set as the measured value.

<Making polyester pellets>
Using dimethyl terephthalate and ethylene glycol as starting materials, a transesterification reaction and a polycondensation reaction were carried out by a conventional method, and the resulting polymer was discharged from a reaction kettle and cooled to pellets of polyethylene terephthalate (hereinafter referred to as “PET”). Abbreviated). The obtained PET had a glass transition temperature of 80 ° C., a melting point of 256 ° C., and an intrinsic viscosity of 0.65 dL / g.

  Transesterification and polycondensation in the same manner as PET except that 85 mol% dimethyl terephthalate (based on the total acid component) and 15 mol% dimethyl isophthalate (based on the total acid component) and ethylene glycol are used as starting materials. The reaction was carried out, and the resulting polymer was discharged from a reaction kettle and cooled to obtain copolymer polyethylene terephthalate pellets (hereinafter abbreviated as “IA-PET”). The obtained IA-PET had a glass transition temperature of 65 ° C., a melting point of 223 ° C., and an intrinsic viscosity of 0.70 dL / g.

  Esters are similar to PET except that 85 mol% dimethyl terephthalate (based on total acid components) and 15 mol% dimethyl 2,6-naphthalenedicarboxylate (based on total acid components) and ethylene glycol are used as starting materials. The exchange reaction and the polycondensation reaction were carried out, and the resulting polymer was discharged from the reaction kettle and cooled to obtain copolymerized polyethylene terephthalate pellets (hereinafter abbreviated as “NDC-PET”). The obtained NDC-PET had a glass transition temperature of 82 ° C., a melting point of 223 ° C., and an intrinsic viscosity of 0.72 dL / g.

[Example 1]
A mixture obtained by mixing the PET obtained above and IA-PET so as to be (PET) / (IA-PET) = 67/33 wt% was used alone as polyester A, while IA-PET and NDC-PET were used. (IA-PET) / (NDC-PET) = single screw extruder which was dried separately using polyester B as a mixture mixed so as to be 50/50% by weight and set to the melt extrusion temperature shown in Table 1. After melting in the mold, the molten polymer is laminated in three layers of (PET and IA-PET mixture) | (IA-PET and NDC-PET mixture) | (PET and IA-PET mixture) inside the die and cooled in this state The film was cast on a drum to obtain an unstretched laminated film. The polyester layer A contained 100 ppm of true spherical silicone having an average particle diameter of 1.2 μm and 600 ppm of true spherical silica having an average particle diameter of 0.1 μm as a lubricant based on the weight of the layer A.

  Subsequently, the unstretched laminated film was stretched 3.0 times in the longitudinal direction at 110 ° C., and then brought into contact with a 25 ° C. metal roll and cooled. Next, it was put into a stenter and stretched 4.0 times in the transverse direction in a stretching zone to which a temperature gradient of 120 to 140 ° C. was applied, and then heat-set at 225 ° C. to obtain polyester layer A / polyester layer B / polyester layer A A biaxially stretched laminated film having a three-layer structure was obtained. Regarding the thickness structure of this biaxially stretched laminated film, the polyester layer A was 3.8 μm, the polyester layer B was 67.4 μm, and the total film thickness was 75 μm. Table 1 shows the structure and properties of the obtained biaxially stretched laminated film.

[Examples 2 to 4]
A biaxially stretched laminated film having a three-layer structure was obtained in the same manner as in Example 1 except that the stretching ratio and the heat setting temperature were changed as shown in Table 1. Table 1 shows the structure and properties of the obtained biaxially stretched laminated film.
The films obtained in Examples 1 to 4 have good moldability because the breaking elongation at 100 ° C. exceeds 100%, and at the same time, the film thickness unevenness is good because the stress at elongation is in a predetermined relationship. The film thickness unevenness after the molding process was also good.

[Comparative Examples 1-3]
A biaxially stretched laminated film having a three-layer structure was obtained in the same manner as in Example 1 except that the stretching ratio and the heat setting temperature were changed as shown in Table 1. Table 1 shows the structure and properties of the obtained biaxially stretched laminated film.
The film obtained in Comparative Example 1 had a heat setting temperature of 10 ° C. higher than the melting point of polyester B and at the same time the transverse draw ratio was too high, so that the elongation at break at 100 ° C. was less than 100% and the moldability was poor. It was a thing.
The film obtained in Comparative Example 2 had a low transverse draw ratio, and was inferior to the film thickness unevenness. Further, the difference between F50 and F10 and the difference between F100 and F50 were small, and the thickness unevenness after the molding process was inferior.
The film obtained in Comparative Example 3 was a film because the heat setting temperature was too high and the transverse stretch ratio was too low with respect to the melting point of the polyester constituting the polyester layer A and the melting point of the polyester constituting the polyester layer B. It was inferior to the thickness unevenness. Further, the difference between F50 and F10 and the difference between F100 and F50 were small, and the thickness unevenness after the molding process was inferior.

  In the present invention, a base film for a molding process such as an application where a resin such as an ink is coated on a film and the thickness of the ink is required to be precisely controlled, and a molding process such as a simultaneous molding method It can be used as a transfer foil film with a design in use, etc., and it can be used to give a design to a member that constitutes the surface of a three-dimensional resin molded part used in furniture, interior decorations, electrical appliances, automobiles, etc. It can be used as a film.

Claims (3)

A biaxially stretched laminated polyester film comprising a polyester layer B having a non-oriented structure and a polyester layer A having an oriented structure provided on both sides in contact with this layer, wherein the main component of the polyester A constituting the polyester layer A is Ethylene terephthalate, polyester B constituting polyester layer B is a copolymerized polyethylene terephthalate containing a copolymer component of 10 to 30 mol% based on the total acid components, and the melting point of polyester A is 15 ° C. or higher than the melting point of polyester B The relationship between the stress at 10% elongation at 100 ° C., the stress at 50% elongation at 100 ° C., and the stress at 100% elongation at 100 ° C. in the longitudinal direction or the width direction of the laminated polyester film is high. And the elongation at break at 100 ° C. satisfies the following formulas (1) to (5): Molding biaxially oriented laminated polyester film according to symptoms.
7 MPa ≦ F50−F10 ≦ 30 MPa (1)
5 MPa ≦ F100−F50 ≦ 25 MPa (2)
19 MPa ≦ F100 ≦ 70 MPa (3)
100% ≦ EB ≦ 400% (4)
7 MPa ≦ F10 ≦ 17 MPa (5)
(In the above formula, F10 is a stress at 10% elongation at 100 ° C. (unit: MPa), F50 is a stress at 50% elongation at 100 ° C. (unit: MPa), and F100 is a stress at 100% elongation at 100 ° C. (unit: MPa). MPa), EB represents the elongation at break at 100 ° C. (unit:%))   The molding component according to claim 1, wherein the copolymer component constituting the polyester B is at least one selected from the group consisting of isophthalic acid, naphthalenedicarboxylic acid, neopentyl glycol, 1,4-cyclohexanedimethanol and diethylene glycol. Biaxially stretched laminated polyester film. In producing the biaxially stretched laminated polyester film for molding according to claim 1,
A laminated polyester film composed of a polyester layer B composed of polyester B and a polyester layer A composed of polyester A provided on both sides in contact with this layer,
A production method in which heat setting is performed at a temperature lower than the melting point of polyester A and a melting point of polyester B from Tm-3 ° C to Tm + 8 ° C.