JP7151444B2 - Polyester film and curved glass composite using it - Google Patents

Description

The present invention relates to a biaxially oriented polyester film for attaching to curved glass, and can suppress warping and peeling of the film after attachment, so that the biaxially oriented polyester film has an excellent protective function for curved glass.

Thermoplastic resin films, especially biaxially oriented polyester films, have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. It is widely used as a base film in applications such as In addition, for example, for the purpose of preventing breakage of glass, a film laminated with glass (for example, Patent Document 1), or a film with improved moldability and stretchability used as a base material for decoration or the manufacturing process of resin materials (for example, , Patent Documents 2 to 4) have also been proposed.

In the case of the film seen in Patent Document 1, it is designed in consideration of the suppression of warping as a glass composite when laminated with flat glass. In the case of laminating along the , the film may warp or peel off due to the residual stress when the film is deformed, and the protective function of the curved glass may be insufficient.

In addition, the polyester films of Patent Documents 2 to 4 are designed to have higher moldability and stretchability at high temperatures than conventional polyester films, but can adhere for a long time to materials such as glass that undergo little thermal dimensional change. Such low residual stress design has not been sufficiently done, especially when laminating along curved glass, the residual stress when the film is deformed causes warping or peeling of the film side, resulting in the curved surface. In some cases, the protective function of the glass was insufficient.

JP 2017-039227 A WO2012-005097 JP 2009-029074 A JP 2014-235311 A

An object of the present invention is to provide a polyester film that eliminates the above-mentioned drawbacks and that can suppress warping and peeling of the film after being attached to curved glass.

The present invention for solving the above problems has the following configuration.
(1) A biaxially oriented polyester film to be attached to glass having a curved surface with a radius of curvature of 0.5 mm or more and 200 mm or less, wherein the 50% elongation stress at 150 ° C. is P1 (MPa), immediately after 50% elongation at 150 ° C. Therefore, when the stress after 60 seconds of holding the 50% elongation state is P2 (MPa), in the direction of the main orientation axis and in the direction perpendicular to the main orientation axis, the formulas (i) and (ii) Biaxially oriented polyester film that satisfies However, the elongation stress is a value obtained under elongation conditions of a sample length of 50 mm, a measurement width of 30 mm, and an elongation rate of 300 mm/min.
5≦P1≦80 (i)
5≦{(P1−P2)/P1×100}≦25 (ii)
(2) The biaxially oriented polyester film according to (1), wherein the difference in {(P1−P2)/P1×100} between the main orientation axis direction and the direction perpendicular to the main orientation axis direction is 0 or more and 5 or less. .
(3) the degree of curl of the trial length portion after being stretched 50% at 150° C. in the direction of the main orientation axis and in the direction perpendicular to the direction of the main orientation axis is 0.5 mm or more and 1,200 mm or less; The biaxially oriented polyester film according to (2). Here, the degree of curl refers to the radius of curvature determined from the end face of a sample cut into a sample length of 50 mm after measurement of elongation.
(4) The film according to any one of (1) to (3), which has an in-plane retardation of 50 nm or more and 750 nm or less.
(5) The film according to any one of (1) to (4), further having a coating layer on at least one side.
(6) An adhesive layer/film laminate in which the film according to any one of (1) to (5) and an adhesive layer are laminated.
(7) A curable resin layer/film laminate in which the film according to any one of (1) to (5) and a curable resin layer are laminated.
(8) Adhesive layer/film/curable resin in which an adhesive layer is laminated on one side of the film according to any one of (1) to (5) and a curable resin layer is laminated on the other side. layer laminate.
(9) The laminate according to (4) to (8), further comprising a polyester film laminated on at least one surface.
(10) The film according to (1) to ( 8 ) or a curved glass composite obtained by laminating a film laminate and a curved glass, wherein the film has a thickness tmin at the thinnest portion and a thickness tmax at the thickest portion. The ratio tmax/tmin is 1.05 or more and 5 or less, and the curvature radius of the curved surface with the smallest curvature radius among the curved surfaces covered by the film is 0.5 mm or more and 200 mm or less. , curved glass composite.

When the polyester film of the present invention is applied as a film to be attached to curved glass, it can suppress warping and peeling of the film after being attached to curved glass, so it has the effect of improving the protective function of curved glass.

The biaxially oriented polyester film of the present invention will be described in detail below.

The biaxially oriented polyester film of the present invention has a 50% elongation stress at 150 ° C. of P1 (MPa), and a stress of P2 ( MPa), it is important to satisfy the formulas (i) and (ii) in the main orientation axis direction and in the direction perpendicular to the main orientation axis direction.
5≦P1≦80 (i)
5≦{(P1−P2)/P1×100}≦25 (ii)
Here, P1 indicates formability at 150° C., and lower P1 indicates lower stress during deformation. When the P1 of the biaxially oriented polyester film of the present invention is 80 MPa or less, the stress at the time of deformation is low, and the film can follow the curved surface of the glass neatly without wrinkling. In addition, when P1 is 5 MPa or more, when an adhesive layer, a curable resin layer, etc., which will be described later, are formed by coating and drying, excessive deformation due to processing tension does not occur, and workability at high temperatures is improved. It is possible to improve the scratch resistance after laminating a curable resin layer, which will be described later.

The biaxially oriented polyester film of the present invention preferably has a P1 of 6 MPa or more, more preferably 18 MPa or more, from the viewpoint of workability and scratch resistance. Moreover, from the viewpoint of followability to curved glass, it is preferably 65 MPa or less, and more preferably 45 MPa or less.

As a method for making P1 within the range of formula (i), the polyester resin constituting the biaxially oriented polyester film may contain two or more diol components or dicarboxylic acid components, or the biaxially oriented polyester film may be produced using A method of reducing the orientation of the film by making the draw ratio lower than the general production conditions used is exemplified.
Further, in the present invention, {(P1-P2)/P1×100} indicates the stress reduction rate before and after the elongation state is maintained at 150° C. for a certain period of time, {(P1-P2)/P1×100}. A smaller value indicates a smaller reduction rate of the stress applied immediately after the elongation. When the film deforms in a short time, the mechanical energy applied during deformation is used to change the shape of the film, and the remaining part is stored in a form that is invisible from a macroscopic point of view, such as the tension of molecular chains. . The stress that occurs in the film plane when the tension of the molecular chains is relaxed and the film returns to its original direction is sometimes called residual stress. Since the force to try is increased, the film tends to warp. This residual stress gradually decreases as the arrangement of the molecular chains is gradually relaxed when the stretched state is maintained for a certain period of time. This indicates that the stress immediately after elongation is difficult to decrease, that is, the residual stress immediately after deformation of the film is small. A large {(P1−P2)/P1×100} in the present invention indicates that the stress immediately after elongation is likely to decrease, that is, the residual stress immediately after deformation of the film is large.

In the biaxially oriented polyester film of the present invention, when {(P1−P2)/P1×100} is 25 or less, the residual stress becomes small when the film is deformed, and the film adheres to a three-dimensional structure such as curved glass. It is possible to suppress warping of the film (between the curved glass and the adhesive layer or between the adhesive layer and the film) when following the layer. Further, when {(P1−P2)/P1×100} is 5 or more, excessive deformation due to processing tension occurs when the adhesive layer, the curable resin layer, etc., which will be described later, are coated and dried. It is possible to improve the workability at high temperatures, and to improve the scratch resistance after laminating a curable resin layer, which will be described later.
In the biaxially oriented polyester film of the present invention, {(P1−P2)/P1×100} is preferably 23 or less, and 18 or less, from the viewpoint of making it more difficult for the film to warp when following curved glass. more preferred.

As a method for making {(P1−P2)/P1×100} within the range of formula (ii), a plurality of cast drums were installed, and the temperature was repeatedly raised and lowered to form microcrystals on the unstretched sheet. Later, a method of setting the ratio of longitudinal stretching or lateral stretching to less than 3 times, or the like can be mentioned. By applying such a method, the microcrystals formed in the unstretched sheet suppress the orientation of the crystals in the in-plane direction due to stretching, and the general manufacturing conditions used when manufacturing the biaxially oriented polyester film In combination with a low draw ratio, it is possible to suppress residual stress during film deformation. In addition, since crystal growth occurs due to stretching triggered by microcrystals formed in the unstretched sheet, the advantages of biaxially oriented polyester film (mechanical properties, transparency, etc.) compared to the manufacturing process with only a simple low stretching ratio (Various characteristics) can be maintained while suppressing residual stress during film deformation.
P1 and P2 in the biaxially oriented polyester film of the present invention are determined by the formula (i) and (ii) must be satisfied. Here, the main orientation axis direction of the biaxially oriented polyester film is the direction in which the molecular chains of the polyester constituting the film are most oriented, and the maximum value of the refractive index when light is transmitted (refraction in the stretching direction) If the main component is a resin with positive birefringence characteristics where the index increases), or the minimum value (when the main component is a resin with negative birefringence characteristics where the refractive index decreases in the stretching direction) direction can be obtained. Specifically, the orientation angle (the angle of the main orientation direction) of a film sampled in an arbitrary direction is measured using a retardation measurement device such as the "KOBRA" series manufactured by Oji Scientific Instruments, and the main orientation direction can be obtained. . In addition, when the transparency of the film is low and it is difficult to measure the refractive index using a phase difference measurement device, etc., the longitudinal wave of the ultrasonic pulse is propagated through the film, and the propagation speed is the fastest or slowest. direction can be obtained.

In the biaxially oriented polyester film of the present invention, P1 and P2 are values obtained under the stretching conditions of 50 mm sample length, 30 mm measured width, and 300 mm/min stretching speed.

The biaxially oriented polyester film of the present invention is a film to be attached to glass having a curved surface with a curvature radius of 0.5 mm or more and 200 mm or less. By setting the radius of curvature of the glass to which the film is attached to be 0.5 mm or more and 200 mm or less, when used as a constituent member of an electronic device such as a smartphone, the electronic device can be made into a shape that is easy to grip with a hand, or a three-dimensional shape. Complex screen display can be made possible. From the viewpoint of improving the handling of electronic devices and enabling more complicated screen display, the radius of curvature of the glass is preferably 1 mm or more and 100 mm or less, more preferably 2 mm or more and 50 mm or less, and 3 mm or more and 30 mm or less. Especially preferred. As a method for determining the radius of curvature of the glass, for example, a laser interferometer such as Canon's "Zygo" series can be used to obtain the radius of curvature by utilizing the interference phenomenon caused by superposition of incident light and reflected light.

The biaxially oriented polyester film of the present invention is attached to glass having a curved surface with a curvature radius of 0.5 mm or more and 200 mm or less, so that it follows the curved surface shape of the glass and prevents cracking and scattering when the glass receives an impact. can be prevented.

The biaxially oriented polyester film of the present invention is a film containing more than 50% by mass of polyester resin. Here, the polyester-based resin is a resin obtained by polymerizing a diol component, which is a structural unit derived from a diol, and a dicarboxylic acid component, which is a structural unit derived from a dicarboxylic acid. Among the polyester resins used in the present invention, examples of diol components include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4- butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol , 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbide, spiroglycol and the like. Among them, ethylene glycol, neopentyl glycol, diethylene glycol, 1,4-cyclohexanedimethanol, isosorbide and spiroglycol are preferably used. These diol components may be used alone or in combination of two or more.
Examples of dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-diphenyldicarboxylic acid. acids, aromatic dicarboxylic acids such as 4,4′-diphenyletherdicarboxylic acid and 4,4′-diphenylsulfonedicarboxylic acid, aliphatic acids such as adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid Ester derivatives with dicarboxylic acids, various aromatic dicarboxylic acids, and aliphatic dicarboxylic acids are included. Among them, terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid are preferably used. These dicarboxylic acid components may be used alone or in combination of two or more.
The biaxially oriented polyester film of the present invention has a laminated structure containing two or more layers with different melting points from the viewpoint of improving the various properties described later, including warpage and peeling when the film is coated on curved glass, in a well-balanced manner. It is preferable to In the biaxially oriented polyester film of the present invention, in the case of a laminated structure including two or more layers with different melting points, the layer with a higher melting point contains more than 90% by mass of terephthalic acid with respect to 100% by mass of all dicarboxylic acid components. % by mass or less, the total amount of isophthalic acid, 1,4-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid is 0% by mass or more and 10% by mass or less, or ethylene with respect to 100% by mass of all diol components Glycol is more than 90% by mass and 100% by mass or less, and the total amount of ethylene glycol, neopentyl glycol, diethylene glycol, 1,4-cyclohexanedimethanol, isosorbide, and spiroglycol is 0% by mass or more and 10% by mass or less. is preferred. Further, in the biaxially oriented polyester film of the present invention, in the case of a laminated structure including two or more layers with different melting points, the layer with a low melting point contains more than 75% by mass of terephthalic acid with respect to 100% by mass of all dicarboxylic acid components. is 94% by mass or less, and the total amount of isophthalic acid, 1,4-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid is 6% by mass or more and 25% by mass or less, or all diol components are 100% by mass. ethylene glycol exceeds 75% by mass and 94% by mass or less, and the total amount of ethylene glycol, neopentyl glycol, diethylene glycol, 1,4-cyclohexanedimethanol, isosorbide, and spiroglycol is 6% by mass or more and 25% by mass or less. is preferably
The biaxially oriented polyester film of the present invention is stretched in two directions so that the molecular chains of the polymer constituting the film are oriented in two in-plane directions. It is important from the viewpoint of not deforming into a large shape and improving the transportability. In the biaxially oriented polyester film of the present invention, as a method for confirming the biaxially oriented state, for example, using a phase difference measuring device such as an Abbe refractometer or Oji Scientific Instruments "KOBRA" series, plane A method of confirming a state in which both the refractive index of the main orientation axis inside and the refractive index in the direction perpendicular to the main orientation axis differ from the refractive index in the thickness direction by 0.01 or more. When the main component of the biaxially oriented polyester film is a resin having positive birefringence, both the refractive index of the in-plane main orientation axis and the refractive index in the direction perpendicular to the main orientation axis are By confirming that the refractive index is 0.01 or more larger than the refractive index of , the biaxial orientation of the film can be confirmed.

In the biaxially oriented polyester film of the present invention, the difference between {(P1−P2)/P1×100} in the main orientation axis direction and the direction perpendicular to the main orientation axis direction is 0 or more and 5 or less. It is preferable because it can suppress peeling of the film. Even if each of the main orientation axis direction and the direction perpendicular to the main orientation axis direction satisfies the range of formula (ii), if the difference in each direction exceeds 5, the direction of the residual stress after molding After a long period of time, a small stress in the torsional direction is generated in an attempt to reduce the difference between the two, and the film may be peeled off from the curved glass. In the biaxially oriented polyester film of the present invention, from the viewpoint of suppressing peeling of the film to curved glass, the difference between the main orientation axis direction and the direction perpendicular to the main orientation axis direction {(P1−P2)/P1×100} is more preferably 0 or more and 3 or less, and particularly preferably 0 or more and 2 or less.

As a method for making the difference between the main orientation axis direction and the direction perpendicular to the main orientation axis direction {(P1−P2)/P1×100} to be 0 or more and 5 or less, the transverse draw ratio is higher than the longitudinal draw ratio. A method of setting the relaxation rate in the heat treatment after lateral stretching to 8% or more and 20% or less, or the like.

The biaxially oriented polyester film of the present invention has a temperature of 150° C. in the direction of the main orientation axis and in the direction perpendicular to the direction of the main orientation axis, from the viewpoint of preventing warping and peeling of the film when the curved portion of glass is coated. It is preferable that the degree of curl of the test length portion after being stretched by 50% is 0.5 mm or more and 1,200 mm or less. Here, the degree of curling refers to the radius of curvature of the end surface of a sample obtained by cutting a 50 mm length portion of the sample length from the film after stretching measurement, and the smaller the value, the smaller the radius of curvature, so the degree of curling. is high. To find the radius of curvature of the end face of the sample, place the sample on a horizontal surface so that the floatation due to curling is on the upper side, and then take a picture with a digital camera or the like from the direction in which the horizontal surface appears straight. After that, the arc shape of the end face of the sample in the photographed image is extracted as coordinate data using image analysis software, and the radius of curvature of the sample can be obtained by fitting it to the equation of the circle using the least squares method. If it is not possible to determine the direction in which the floatation due to curling is on the upper side, calculate the curvature radii of both sides of the sample and adopt the smaller value (the side with the stronger curl).

The biaxially oriented polyester film of the present invention is designed so that it curls slightly after being stretched, and the curved glass is arranged on the inner surface of the curl, so that the curved shape of the glass is subjected to excessive stress. This makes it possible to wrap the film without causing any warpage or peeling of the film when the curved portion of the glass is covered. From the viewpoint of further suppressing warpage and peeling, the degree of curl is more preferably 650 mm or less. On the other hand, the degree of curl is more preferably 90 mm or more from the viewpoint of handleability during the manufacturing process. As a method for setting the degree of curl to 0.5 mm or more and 1,200 mm or less, a two-layer structure of polyester A layer / polyester B layer is formed, and the orientation state of each layer is changed, or polyester B1 layer / polyester A layer / polyester B2. A method of making the composition and structure in the thickness direction asymmetrical by, for example, making a difference in thickness between the B1 layer and the B2 layer as a three-layer structure.

The biaxially oriented polyester film of the present invention preferably has an in-plane retardation of 50 nm or more and 750 nm or less from the viewpoint of improving the authentication of various sensors when mounted on an electronic device after being attached to a curved glass. In recent years, electronic devices such as smartphones have become more sophisticated and functional, and more and more devices are equipped with face authentication functions and fingerprint authentication functions. Various optical sensors are sometimes used in these authentications, but one example of the operating principle of optical sensors is that light of a specific wavelength is emitted from the light source of a sensor installed inside an electronic device such as a smartphone. , After passing through the polarizing plate and glass members that make up the display from inside the smartphone, it passes through the display protective film in order. After being reflected by the face and fingers, the transmitted light passes through the display protection film, glass member, and polarizing plate again, and finally reaches the sensor light receiving section. When a biaxially oriented polyester film is used as a display protective film, if the in-plane retardation exceeds 750 nm, the intensity of light reaching the light-receiving part is weakened due to birefringence, and the authentication of the sensor may deteriorate. be. From the viewpoint of enhancing sensor authentication, the in-plane retardation of the biaxially oriented polyester film of the present invention is more preferably 400 nm or less, particularly preferably 250 nm or less. Moreover, from the viewpoint of film handleability, etc., the in-plane retardation of the biaxially oriented polyester film of the present invention is preferably 50 nm or more. In the present invention, the in-plane retardation refers to the product of birefringence (the difference between the refractive index in the in-plane main orientation axis direction and the refractive index in the direction perpendicular to the main orientation axis direction) and the thickness, and Abbe refraction It can be calculated from the following formula (iii) by measuring the refractive index in each direction using a meter.
In-plane retardation = |nx−ny|× film thickness (nm) (iii)
However, in formula (iii), nx is the refractive index in the main alignment axis direction, and ny is the refractive index in the direction orthogonal to the main alignment axis direction. Further, the in-plane phase difference can also be measured using a phase difference measuring device such as the "KOBRA" series manufactured by Oji Scientific Instruments Co., Ltd. In the present invention, the method of adjusting the in-plane retardation to 50 nm or more and 750 nm or less includes a method of adjusting the ratio of longitudinal stretching and transverse stretching, stretching temperature, and heat treatment temperature to make the birefringence within a specific range, and a method of adjusting the thickness. is mentioned. The biaxially oriented polyester film of the present invention preferably has a coating layer on at least one side from the viewpoint of improving adhesion to the adhesive layer, curable resin layer, and the like, which will be described later. Here, the coating layer refers to a layer obtained by dispersing a resin having various functions such as easy adhesion in a solvent to prepare a coating liquid, applying the coating liquid to a film, and drying the film. The resin used in the coating liquid is not particularly limited, but examples include acrylic resins, urethane resins, polyester resins, olefin resins, fluorine resins, vinyl resins, chlorine resins, and styrene. A resin, an epoxy resin, a silicone resin, a resin obtained by copolymerizing these resins, or a mixture of these resins can be used. When the solvent of the coating liquid is a water-based liquid, a water-soluble or water-dispersible polyester resin is preferable. Compounds containing moieties are preferably used. In addition, the coating layer may contain various cross-linking agents in order to further improve the function of the coating layer. As the cross-linking agent, melamine-based resins, epoxy-based resins, oxazoline-based resins and the like are generally used. The coating layer may contain various inorganic particles and organic particles from the viewpoint of improving lubricity and anti-blocking properties. Examples of inorganic particles include silica, alumina, kaolin, talc, mica, calcium carbonate, and titanium oxide. In addition, the inorganic particles and organic particles may be surface-treated from the viewpoint of improving the dispersibility in the coating liquid. Examples of surface treatment agents include various surfactants, silane coupling agents, titanium coupling agents and the like.

It is preferable that the biaxially oriented polyester film of the present invention is further laminated with an adhesive layer from the viewpoint of improving adhesion to glass. That is, the configuration of adhesive layer/film laminate is preferably used. Here, the adhesive layer is a layer made of a resin having adhesive properties, and can be produced by various methods such as coating, extrusion lamination, and transfer. The resin used for the adhesive layer is not particularly limited, but examples thereof include acrylic resins, polyether resins, urethane resins, and silicone resins.

From the viewpoint of imparting scratch resistance, the biaxially oriented polyester film of the present invention preferably further has a curable resin layer. That is, a configuration of curable resin layer/film laminate is preferably used. Here, the curable resin layer is a layer made of a resin that forms cross-linking points with energy such as heat or ultraviolet rays and becomes hard. The resin constituting the curable resin layer is not particularly limited as long as it has transparency. Various resins such as vinyl acetate copolymer resins and ethylene-vinyl acetate copolymer resin copolymers are preferably used.

The biaxially oriented polyester film of the present invention has an adhesive layer on one side and a hardened layer on the other side from the viewpoint of protecting the glass from external impact by improving the adhesion to the glass and making the film itself less likely to be scratched. It preferably has a configuration in which a curable resin layer is laminated, that is, a laminate configuration of an adhesive layer/film/curable resin layer.

From the viewpoint of protecting the adhesive layer and the curable resin layer during the manufacturing process of the curved glass composite, the present invention provides an adhesive layer/film laminate, a curable resin layer/film laminate, and an adhesive layer/film/curable resin. It is preferable to further laminate a polyester film on at least one side of each laminate such as a layer laminate. For the purpose of protecting the adhesive layer and the curable resin layer, the polyester film is preferably laminated on the adhesive layer side and/or the curable resin layer side of each laminate. Since the polyester film laminated on the adhesive layer side and the curable resin layer side is adhered to the glass and peeled after molding, it is preferable to have a release layer on the side laminated with the adhesive layer or the curable resin layer. . The release layer may be formed by wet processing such as coating or by dry processing such as chemical vapor deposition, but from the viewpoint of cost, wet processing such as coating is preferable. In addition, the coating can be performed by either an in-line coating method in which coating is performed in the manufacturing process of the biaxially oriented polyester film, or an off-coating method in which the biaxially oriented polyester film once commercialized is coated with a coater. Materials used for the release layer include various silicone-based resins, fluorosilicone-based resins, modified silicone-based resins, amido-alkyd-based resins, olefin-based resins, long-chain alkyl-based resins, urethane-based resins, and combinations thereof. From the viewpoint of adhesion between the biaxially oriented polyester film and the release layer, the release layer may be composed of two or more layers, or the biaxially oriented polyester film may be subjected to various surface treatments.

The biaxially oriented polyester film of the present invention, or a laminate with a film (adhesive layer / film / curable resin layer, etc.) is a curved glass composite in which specific curved glass is laminated, so that it can be used for smartphones and car navigation systems. It can be preferably used as a constituent member of an electronic device such as a system or a home appliance, or a constituent member of a building part such as a smart window. Specifically, it is possible to make an electronic device into a shape that is easy to hold by hand, or to enable complicated screen display in a three-dimensional shape. The film constituting the curved glass composite preferably has a ratio tmax/tmin of the thickness tmin of the thinnest portion of the film to the thickness tmax of the thickest portion of the film of 1.05 or more and 5 or less. By setting tmax/tmin to 1.05 or more, the film can follow the curved surface without causing wrinkles, and the surface appearance of the glass composite on the film side is improved. Further, by setting tmax/tmin to 5 or less, the glass protective function of the film becomes uniform, and the glass composite can be made difficult to crack.

The curved glass constituting the curved glass composite of the present invention has a curvature radius of 0.5 mm or more and 200 mm or less, so that when used as a constituent member of an electronic device such as a smartphone, the electronic device has a shape that is easy to grip. or to enable complex screen display in a three-dimensional shape. From the viewpoint of improving the handling of electronic devices and enabling more complicated screen display, the radius of curvature of the glass is preferably 1 mm or more and 100 mm or less, more preferably 2 mm or more and 50 mm or less, and 3 mm or more and 30 mm or less. Especially preferred. As a method for determining the radius of curvature of the glass, for example, a laser interferometer such as Canon's "Zygo" series can be used to obtain the radius of curvature by utilizing the interference phenomenon caused by superposition of incident light and reflected light.
Next, a preferred method for producing the biaxially oriented polyester film of the present invention will be described below. The present invention should not be construed as being limited to such examples.

First, a raw material such as a polyester resin is supplied to a vented twin-screw extruder and melt-extruded. When the polyester A layer and the polyester B layer are laminated, the polyester A used for the polyester A layer and the polyester B used for the polyester B layer are supplied to separate vented twin-screw extruders and melt extruded. In the following description, a configuration in which a polyester A layer and a polyester B layer are laminated will be described. When performing melt extrusion, the extruder is circulated in a nitrogen atmosphere, the oxygen concentration is 0.7% by volume or less, and the extrusion temperature of the crystalline resin is 5°C to 40°C higher than the melting point of the resin with the highest melting point among the layers. It is preferable to set the temperature higher than 180°C to 270°C. Next, foreign substances are removed and the extrusion rate is made uniform through a filter or a gear pump. After the polyester A layer and the polyester B layer are combined, the mixture is discharged in the form of a sheet from a T-die onto a cast drum. At that time, an electrostatic application method that uses electrodes to which a high voltage is applied to make the cast drum and resin adhere to each other with static electricity, a casting method that creates a water film between the cast drum and the extruded polymer sheet, and a cast drum temperature that changes the polyester resin. A sheet-like polymer is brought into close contact with a cast drum by a method of making the polymer extruded below the glass transition point sticky, or by a method combining a plurality of these methods, and solidified by cooling to obtain an unstretched film. Among these casting methods, when polyester is used, the method of applying static electricity is preferably used from the viewpoint of productivity and flatness. In addition, by setting a plurality of cast drums and raising and lowering the temperature of each cast drum, the temperature can be repeatedly raised and lowered to form microcrystals in the unstretched sheet, and the subsequent stretching ratio can be adjusted to that of the biaxially oriented polyester film. It is possible to maintain the characteristics of the biaxially oriented polyester film (various properties such as mechanical properties and transparency) even if the conditions are lower than the general production conditions used during production.

The biaxially oriented polyester film of the present invention is important to be biaxially oriented from the viewpoint of heat resistance and dimensional stability when laminating an adhesive layer, a curable resin layer, etc., and the unstretched film is stretched in the longitudinal direction. Stretching is performed by a sequential biaxial stretching method in which the film is stretched in the width direction after stretching, or a sequential biaxial stretching method in which the film is stretched in the width direction and then in the longitudinal direction, or a simultaneous biaxial stretching method in which the film is stretched almost simultaneously in the longitudinal direction and the width direction. You can get it by doing.

The stretching ratio in the stretching method is preferably 1.4 times or more and 3.5 times or less, more preferably 1.6 times or more and 2.9 times or less in the longitudinal direction. Moreover, it is desirable that the drawing speed is 1,000%/minute or more and 200,000%/minute or less. Moreover, the stretching temperature in the longitudinal direction is preferably 80° C. or higher and 130° C. or lower. The draw ratio in the width direction is preferably 1.6 times or more and 4 times or less, more preferably 1.8 times or more and 3.2 times or less. The stretching speed in the width direction is preferably 1,000%/min or more and 200,000%/min or less.

Furthermore, the film is heat-treated after the biaxial stretching. The heat treatment can be performed by any conventionally known method such as in an oven or on heated rolls. The purpose of this heat treatment is to grow oriented crystals after biaxial orientation and improve the thermal dimensional properties. is common. Further, by narrowing the clip gap in the width direction of the film and performing the heat treatment in a relaxed state, the shrinkage that occurs during heating can be advanced in advance. From the viewpoint of improving the balance between the residual stress in the main orientation direction and the direction perpendicular to the main orientation direction, the transverse draw ratio was set higher than the longitudinal draw ratio to make the orientation in the transverse stretch direction slightly stronger. After that, heat treatment is performed with a relaxation ratio (relaxation rate) of 8% to 20% from the general manufacturing conditions of biaxially stretched polyester film, and the release and orientation of the residual stress in the heat treatment process can be balanced. preferable.

In addition, in order to improve the adhesion with the adhesive layer and the curable resin layer, at least one side of the biaxially oriented polyester film is subjected to surface treatment such as corona treatment, and the coating layer is applied to the biaxially oriented polyester film. It may be coated during the process. As a coating method during the manufacturing process, a coating liquid in which a resin is dispersed in water or an organic solvent is uniformly applied to a film that has been stretched at least uniaxially using a metering bar or a gravure roll, and then stretched. A method of drying the coating liquid while drying is preferably used. At that time, the thickness of the coating is preferably 0.01 μm or more and 1 μm or less. In addition, various additives, such as antioxidants, heat stabilizers, ultraviolet absorbers, infrared absorbers, pigments, dyes, organic or inorganic particles, antistatic agents, may be added to the coating layer to the extent that the desired functions are not impaired. , a nucleating agent and the like may be added.

Next, a method for producing a laminate of adhesive layer/film/curable resin layer using a biaxially oriented polyester film will be described below.

A coating material prepared by dispersing the adhesive layer composition in water or an organic solvent is applied to a biaxially oriented polyester film by an off-coating method or the like, and dried to form an adhesive layer. After the adhesive layer is formed, if necessary, a release film is laminated on the adhesive layer to protect the adhesive layer. can be suppressed. Next, in the obtained adhesive layer/film laminate, a coating agent in which a composition constituting a curable resin layer is dispersed in water or an organic solvent is applied to the surface on which the adhesive layer is not laminated by an off-coating method or the like. It is applied and dried to form a curable resin layer. After forming the curable resin layer, if necessary, a release film to protect the curable resin layer can be attached on the curable resin layer to prevent scratches during the process of the curable resin layer, which is soft before curing. It is possible to suppress sticking and denting. The order of processing the adhesive layer and the curable resin layer can be changed from the above, but if the curable resin layer is made of a thermosetting resin, the progress of curing due to heat during drying of the adhesive layer can be suppressed and the curved surface can be formed. From the viewpoint of improving moldability when molding into a glass shape, it is preferable to process the adhesive layer first. As the off-coating method, specifically, a coating agent in which a resin is dispersed in water or an organic solvent is applied to a film by a dip coating method, a roller coating method, a wire bar coating method, a gravure coating method, a die coating method, or the like. is mentioned. In addition, since the solvent is completely removed by drying the applied liquid film, the drying process preferably accompanies heating of the liquid film. Heat transfer (hot air), radiant heat transfer (infrared), others (microwave, induction heating), and the like. Among these methods, a method using convective heat transfer or radiant heat transfer is preferable because it is necessary to precisely uniform the drying rate even in the width direction. As a release film that protects the adhesive layer and the curable resin layer, a biaxially oriented polyester film coated with a highly releasable resin and provided with a release layer is used. , various silicone-based resins, fluorosilicone-based resins, modified silicone-based resins, amido-alkyd-based resins, polyolefin-based resins, long-chain alkyl-based resins, polyurethane-based resins, and combinations thereof. In addition, from the viewpoint of improving the adhesion between the biaxially oriented polyester film and the adhesive layer or curable resin layer, a coating layer having functions such as easy adhesion is laminated on the biaxially oriented polyester film, and the adhesive layer is placed on the coating layer. A configuration in which layers and curable resin layers are laminated is preferable.

Next, a method for manufacturing a curved glass composite will be described below. The structure obtained by laminating the release film on both sides of the laminate of the adhesive layer / film / curable resin layer obtained as described above is combined with the curved glass while the release film is still laminated. A preform is obtained by hot pressing using a mold of the same shape. The heat press temperature is preferably higher than the temperature above the glass transition temperature of the biaxially oriented polyester film obtained from dynamic viscoelasticity from the viewpoint of moldability, and the melting point of the biaxially oriented polyester or lower is the flatness of the film. preferred from When the biaxially oriented polyester film contains polyethylene terephthalate as a main component, the temperature is preferably in the range of 120° C. or higher and 200° C. or lower. After peeling off the release film on the adhesive layer side of the obtained preform, the curved glass and the adhesive layer of the preform are adhered manually or by using a vacuum laminator, and then heat-treated as necessary. After curing of the curable resin layer is advanced by UV irradiation treatment or the like, the release film on the curable resin layer side is peeled off to obtain a curved glass composite. The release film on the curable resin layer side may be peeled off before the curable resin layer is cured, or may be peeled off after the curable resin layer is cured. If necessary, the edge of the preform may be trimmed after the preform is molded or after the adhesive layer of the preform is brought into close contact with the curved glass.

As the curved glass used in the present invention, a method of press-molding a raw glass sheet near the softening temperature to form it into a predetermined shape, and a down-draw method (a method of drawing molten glass downward through a slit in the bottom of a furnace). , a method of forming a curved surface on the glass by creating a peripheral speed difference between rolls arranged on both sides of the glass film when slowly cooling the glass film, and the like.

Methods for measuring properties and evaluating effects in the present invention are as follows.

(1) Polyester composition A polyester resin or film was dissolved in hexafluoroisopropanol (HFIP), and the content of each monomer residue component and by-product diethylene glycol was quantified using ¹ H-NMR and ¹³ C-NMR. In the case of the laminated film, each layer of the film was scraped off according to the thickness of the laminated film, and the components constituting each layer alone were sampled and evaluated. The composition of the film of the present invention was calculated from the mixing ratio at the time of film production.

(2) Intrinsic viscosity of polyester The intrinsic viscosity of a polyester resin or film was measured by dissolving the polyester resin or film in orthochlorophenol and using an Ostwald viscometer at 25°C. In the case of the laminated film, the intrinsic viscosity of each layer was evaluated by scraping off each layer of the film according to the laminated thickness.

(3) Film Thickness, Layer Thickness A film was embedded in an epoxy resin, and a section of the film was cut out with a microtome. The cross section was observed with a transmission electron microscope (TEM H7100, manufactured by Hitachi, Ltd.) at a magnification of 5000 times to determine the film thickness and the polyester layer thickness.

(4) Using a melting point differential scanning calorimeter (manufactured by Seiko Electronics, RDC220), measurement and analysis were performed according to JIS K-7121-1987 and JIS K-7122-1987. Using 5 mg of polyester film as a sample, the temperature at the top of the endothermic peak obtained from the DSC curve when the temperature was raised from 25° C. to 300° C. at 20° C./min was taken as the melting point. In the case of a laminated film, the melting point of each layer was measured by scraping off each layer of the film, and when multiple melting points were observed, the endothermic peak with the largest area was adopted as the melting point of the layer.

(5) A sample with a size of 100 mm × 100 mm was cut out at an arbitrary point of the film in the direction of the main orientation axis or in a direction perpendicular to the direction of the main orientation axis, and a microwave molecular orientation meter MOA-2001A manufactured by KS Systems (now Oji Scientific Instruments) was used. (frequency 4 GHz), the in-plane main orientation axis direction of the polyester film was obtained. Further, based on the obtained main orientation axis direction, the direction perpendicular to the main orientation axis direction was also obtained.
(6) P1, P2
After determining the main orientation axis direction and the direction perpendicular to the main orientation axis direction by the method of (5), a rectangle of 150 mm × 30 mm (main orientation axis direction × direction perpendicular to the main orientation axis direction) was cut out and used as a sample. did. Set the sample in a tensile tester (Tensilon UCT-100 made by Orientec) so that the test length (initial tensile chuck distance) is 50 mm, and set the sample at a tensile speed of 300 mm / min so that the chuck distance is 75 mm (initial test length The tensile test was performed until the state reached 50% elongation when set to 100%). After that, the tensile test was stopped when the chuck-to-chuck distance reached 75 mm, and the sample was held for 60 seconds. In addition, the measurement was performed in a constant temperature bath previously set at 150° C., and the tensile test was performed after preheating for 60 seconds. When the tensile test was performed under the above conditions, the stress immediately after stretching to 75 mm was measured 10 times, and the average value was obtained as P1 (MPa) in the main orientation axis direction. In addition, the stress after stretching to 75 mm was completed and held at 150° C. for 60 seconds, the average value of 10 measurements was obtained as P2 (MPa) in the direction of the main orientation axis. A sample was prepared by cutting a rectangle of 150 mm × 30 mm (direction perpendicular to the main orientation axis direction × main orientation axis direction), and P1 (MPa) and P2 (MPa) in the direction perpendicular to the main orientation axis direction were also measured in the same manner. asked.

(7) {(P1−P2)/P1×100}
After obtaining P1 and P2 by the method of (6), they were obtained by calculation according to the formula.

(8) Degree of curl A rectangular sample (150 mm × 30 mm (main orientation axis direction × direction perpendicular to the main orientation axis direction)) is set in a tensile tester in the same manner as in (6) so that the test length is 50 mm. After that, the position of the boundary sandwiched by the chuck was marked in the direction of the main orientation axis with an oil-based pen. After that, a tensile test was performed at a tensile speed of 300 mm/min until the distance between chucks reached 75 mm (50% stretched state when the initial test length was taken as 100%), and the tensile test was stopped when the distance reached 75 mm. sample was removed. In addition, the measurement was performed in a constant temperature bath previously set at 150° C., and the tensile test was performed after preheating for 60 seconds. Both ends of the sample were cut off from the taken-out sample along the marks written with a permanent marker to prepare a sample for measuring the degree of curl. The obtained sample was placed on a horizontal surface so that the floatation due to curling was on the upper side, and then photographed with a digital camera or the like from the direction in which the horizontal surface appears straight. For the obtained photographed image, the arc shape of the sample end surface is extracted as coordinate data by image analysis software, and the radius of curvature of the sample is obtained by fitting to the equation of the circle using the least squares method. The average value of the measurements was taken as the degree of curl in the main orientation direction. When the direction of lifting due to curling could not be determined visually, the average value of the curvature radii of 10 times on both sides of the sample was calculated, and the smaller value (the side with stronger curling) was adopted. A sample was prepared by cutting a rectangle of 150 mm×30 mm (direction perpendicular to the main orientation axis direction×main orientation axis direction), and the degree of curl in the direction perpendicular to the main orientation axis direction was similarly determined.

(9) Curvature radius of glass Using a Canon non-contact scanning interferometer (Zygo, New View 7300), the shape of the glass member is subjected to a three-dimensional optical profile, and the point with the lowest curvature radius is obtained. is the radius of curvature of

(10) Warp of film After cutting the biaxially oriented polyester film into a size of A4, the adhesive layer composition described later is applied to the film surface using an applicator, and dried at 130 ° C. for 5 minutes to form a 10 μm adhesive layer. formed. Next, a release-treated biaxially oriented polyester film ("Therapeel HP2" (thickness: 50 µm) manufactured by Toray Advanced Film Co., Ltd.) was placed on the adhesive layer and pressed with a hand roller to adhere. Subsequently, the surface of the biaxially oriented polyester film on which the adhesive layer was not formed was coated with a curable resin layer composition described later, and dried at 80° C. for 5 minutes to form a 10 μm curable resin layer. After that, a biaxially oriented polyester film ("Therapeal HP2" (thickness 50 μm) manufactured by Toray Advanced Film Co., Ltd.) that has been subjected to mold release treatment is layered on the curable resin layer, and pressure is applied with a hand roller to adhere to the adhesive layer. A structure was prepared by sandwiching a laminate of "/film/curable resin layer" with release films on both sides. The resulting structure was attached to a curved glass (size: 100 mm × 50 mm, thickness: 20 mm, curvature radius of four corners on one side: 7 mm, other side: flat). A preform was obtained by hot pressing using a mold having the same shape as the surface having four corners with a radius of curvature of 7 mm. The heat press treatment was performed under the conditions of a mold temperature of 170° C. and a heat press time of 10 seconds. After peeling off the release film on the adhesive layer side of the obtained preform, the curved glass and the adhesive layer of the preform are brought into close contact manually, and then the release film on the curable resin layer side is peeled off. Finally, a curved glass composite was obtained by trimming the portion of the preform that was not in close contact with the glass. For the resulting curved glass composite, the flat side not covered with the film was placed on a horizontal surface, and the average height of the four corners (four points) of the float on the end face of the film at the lowest part of the curved surface at the four corners was measured. Evaluation was made according to the following criteria.
S: less than 1 mm.
A: 1 mm or more and less than 1.5 mm.
B: 1.5 mm or more and less than 2 mm.
C: 2 mm or more and less than 3 mm.
D: 3 mm or more and less than 4 mm.
E: 4 mm or more.

(11) Film peeling A curved glass composite prepared in the same manner as in (10) was stored in a constant temperature and humidity chamber at 85 ° C.-85% RH for 24 hours and subjected to an environmental test. The adhesion state of the film at the four corners (four places) was visually confirmed and evaluated according to the following criteria.
A: Peeling is not observed in any case.
B: Slight peeling (longer diameter less than 3 mm) is observed at one location, but large peeling (longer diameter 3 mm or more) is not observed at any location.
C: Slight peeling (longer diameter less than 3 mm) is observed at two or more locations, but large peeling (longer diameter 3 mm or more) is not observed at any location.
D: Large peeling (longer diameter of 3 mm or more) is observed at one or more locations.

(12) Scratch resistance of curable resin layer A curved glass composite produced in the same manner as in (10) was evaluated for wear resistance with steel wool. In the evaluation, steel wool #0000 (manufactured by Nippon Steel Wool Co., Ltd.) was used, and the load was 250 g/cm ² , the speed was 60 mm/sec, and the reciprocation distance was 120 mm, and the sample was reciprocated 1000 times. The test environment is a temperature of 23° C. and a relative humidity of 55%. A Gakushin type fastness to rubbing tester (“AB-301” manufactured by Tester Sangyo Co., Ltd.) was used as an abrasion tester. After that, a black tape was attached to the flat side (the side on which the film was not laminated) of the curved glass composite, and the occurrence of scratches on the surface of the UV-curable resin layer was visually observed under a fluorescent lamp (illuminance of 600 lux). , was evaluated according to the following criteria. The wound was observed by three males in their twenties with a visual acuity of 1.2 to 1.5 (including corrected visual acuity), and the average value of the three persons was adopted and evaluated according to the following criteria.
A: The number of scratches is 10 or less.
B: The number of scratches is 11 or more and 19 or less.
C: The number of scratches is 20 or more and 29 or less.
D: The number of scratches is 30 or more and 39 or less.
E: The number of scratches is 40 or more.

(13) Handleability In the same manner as in (10), a structure was produced in which both sides of the adhesive layer/film/curable resin layer laminate were sandwiched between release films. The radius of curvature of the resulting structure was obtained in the same manner as in (8) and evaluated according to the following criteria. The larger the radius of curvature of the structure, the weaker the curl of the structure. indicates that
A: Curvature radius is 2500 mm or more.
B: Curvature radius is 1800 mm or more and less than 2500 mm.
C: Curvature radius is 1300 mm or more and less than 1800 mm.
D: Curvature radius is less than 1300 mm.

(14) Visibility curved glass (size 100 mm × 50 mm, thickness 20 mm, only the four corners on one side are curved, and the other side is flat), except for changing the radius of curvature of the four corners ( A curved glass composite was produced in the same manner as in 10). On top of the LED backlight panel (GT-GG-W manufactured by Kyodo Lighting Co., Ltd.), put a transparent film printed with 8pt size characters with black ink, and then put a curved glass composite on top of it to make a curved glass composite. The visibility of characters was confirmed from the four corners of the body, and evaluated according to the following criteria. Note that characters were observed by 10 men in their twenties with a visual acuity of 1.2 to 1.5 (including corrected visual acuity), and the most frequent evaluation criteria were adopted. In addition, when evaluations by the same number of people were aligned, the better evaluation was adopted.
A: Characters were clearly visible.
B: The characters looked slightly distorted, but could be distinguished.
C: Letters appear large and distorted, but they are barely discernible.
D: Characters could not be distinguished.
(15) tmax/tmin
Of the curved glass composite produced in the same manner as in (14), the thickest part of the film (in-plane center position of the curved glass composite) and the thinnest part of the film (four corners of the curved shape) were cut using a cutter. A cut was made, and a sample piece of about 10 mm square was peeled off and collected. When the adhesion between the glass and the adhesive layer was strong, an organic solvent such as acetone was impregnated through the slit of the cutter to reduce the adhesion of the adhesive layer, and then the adhesive layer was peeled off. For the obtained sample piece, the film thickness is obtained in the same manner as in (4), the thickest part is tmax (μm), the thinnest part of the four corners is tmin (μm), and then tmax is divided by tmin. and asked.

(16) After determining the main orientation axis direction and the direction perpendicular to the main orientation axis direction by the method of (5) in-plane retardation, 150 mm × 30 mm (main orientation axis direction × direction perpendicular to the main orientation axis direction) It was cut into a rectangular shape and used as a sample. Then, using a sodium D line (wavelength 589 nm) as a light source, using methylene iodide as a mounting liquid, and using an Abbe refractometer at 25° C., the main orientation axis direction (X direction) and the direction perpendicular to the main orientation axis direction were measured. Refractive indices (nx, ny) in the (Y direction) were obtained, and the in-plane retardation was calculated from the following formula (iii).
In-plane retardation = |nx−ny|× film thickness (nm) (iii)
(17) Authenticability For the curved glass composite produced in the same manner as in (14), the flat side (the side on which the film is not laminated) of the curved glass composite is attached to a commercially available polarizing plate (polarization degree 99.9%). In addition, a reflective photosensor was installed from the polarizing plate side to simulate an electronic component. That is, the reflective photosensor, the polarizing plate, and the curved glass composite were arranged in this order. After such arrangement, a finger was placed on the light beam of the photosensor to confirm whether or not the reflected light was recognized by the light receiving portion of the sensor. The reflective photosensor "UR1616" (manufactured by Unitech, emission wavelength 624 nm) was used, and the direction of the polarizing plate was changed at random to check 100 times, and the authentication rate was evaluated as follows.
A: The authentication rate was 100%.
B: The authentication rate was 95% or more and 99% or less.
C: The authentication rate was 90% or more and 94% or less.
D: The authentication rate was 89% or less.
The following resins were used in the production of the biaxially oriented polyester film of the present invention.

(PET)
A polyethylene terephthalate resin (intrinsic viscosity of 0.63) containing 100 mol % of terephthalic acid as a dicarboxylic acid component and 100 mol % of ethylene glycol as a glycol component.

(PET-I)
An isophthalic acid-copolymerized polyethylene terephthalate resin (intrinsic viscosity: 0.7, melting point: 240°C) containing 94 mol% of terephthalic acid component and 6 mol% of isophthalic acid component as dicarboxylic acid components, and 100 mol% of ethylene glycol component as glycol component. .

(PBT-I)
An isophthalic acid-copolymerized polyethylene terephthalate resin (intrinsic viscosity: 1.0, mp 205°C).
(PET-G)
Cyclohexanedimethanol copolymerized polyethylene terephthalate resin (intrinsic viscosity 0.8, melting point 200°C) containing 100 mol% of terephthalic acid as a dicarboxylic acid component, 75 mol% of ethylene glycol as a glycol component, and 25 mol% of cyclohexanedimethanol ).
(PET-N)
Copolymerized polyethylene terephthalate resin (intrinsic viscosity: 0.75, melting point: 230°C).
(Coating layer composition AD-1)
The following materials were mixed to obtain a coating layer composition.
Coating agent A: water-dispersible acrylic resin Coating agent B: methylolated melamine (diluent: isopropanol/water)
Coating agent C: colloidal silica (average particle size: 80 nm)
Coating agent D: fluorosurfactant (diluent: water).
(Composition for adhesive layer)
The following materials were mixed to obtain an adhesive layer composition.
"EG654" (manufactured by Toyochem, acrylic adhesive) 84.7 parts by mass "BXX6460" (manufactured by Toyochem, isocyanate curing agent) 10.1 parts by mass "BXX4805" (manufactured by Toyochem, aluminum chelating agent) 5.1 parts by mass "BXX6342" (manufactured by Toyochem, silane coupling agent) 0.1 parts by mass (composition for curable resin layer)
The following materials were mixed to obtain a curable resin composition.
"KRM8655" (manufactured by Daicel Ornex, multifunctional urethane acrylate) 20 parts by mass "PET30" (manufactured by Nippon Kayaku, pentaerythritol triacrylate mixture) 20 parts by mass "EBECRYL1360" (manufactured by Daicel Ornex, multifunctional silicone acrylate) 1 Parts by weight "Irgacure 184" (manufactured by Ciba Specialty Chemicals, photopolymerization initiator) 2 parts by weight Toluene 30 parts by weight Methyl ethyl ketone 27 parts by weight (Example 1)
With the composition as shown in the table, the raw materials were fed to separate vented co-rotating twin screw extruders (oxygen concentration 0.2% by volume), the A layer extruder cylinder temperature was 270 ° C., and the B layer extruder cylinder temperature was 280 ° C. and melted in the feed block to form a three-layer structure of B1 layer / A layer / B2 layer (both B1 layer and B2 layer are the same raw material extruded from the B layer extruder). At a tube temperature of 275°C and a mouthpiece temperature of 280°C, a sheet was discharged onto a first cast drum (25°C) temperature-controlled at 25°C from a T-die. At that time, static electricity was applied using a wire-shaped electrode with a diameter of 0.1 mm, and the contact time with the cooling drum was 10 seconds. The cooled sheet was then passed through a second casting drum (67° C.) for 10 seconds and a third casting drum (25° C.) for 5 seconds to obtain an unstretched sheet. Next, the film was stretched 2.85 times in the longitudinal direction at a stretching temperature of 85°C and immediately cooled to 40°C with metal rolls. Next, the coating layer resin composition AD-1 was applied to both sides of the uniaxially stretched film with a wire bar so that the solid content thickness was 300 nm. Next, the film was preheated at a preheating temperature of 85°C for 1.5 seconds in a tenter-type transverse stretching machine, stretched 3.1 times in the width direction at a stretching temperature of 110°C, and then heat-treated at 235°C in the tenter. Finally, heat treatment was performed under heat treatment conditions at 235° C. with 10% relaxation in the width direction to obtain a biaxially oriented polyester film with a film thickness of 100 μm. In addition, about visibility evaluation, it implemented using curved-surface glass with a curvature radius of 7 mm.

(Example 2)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the A layer extruder cylinder temperature was 230 ° C., the B layer extruder cylinder was 270 ° C., and the composition and production conditions were as shown in the table. An evaluation was carried out.

(Example 3)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the composition and production conditions were as shown in the table, and various evaluations were carried out.

(Example 4)
A biaxially oriented polyester film was obtained and subjected to various evaluations in the same manner as in Example 1, except that the A-layer extruder cylinder temperature was 280° C. and the composition and production conditions were as shown in the table.

(Example 5)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the A layer extruder cylinder temperature was 270 ° C., the B layer extruder cylinder temperature was 260 ° C., and the composition and production conditions were as shown in the table. An evaluation was carried out.

(Example 6)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the A layer extruder cylinder temperature was 270 ° C., the B layer extruder cylinder temperature was 260 ° C., and the composition and production conditions were as shown in the table. An evaluation was carried out.

(Example 7)
A biaxially oriented polyester film was obtained in the same manner as in Example 6 except that the lamination ratio was as shown in the table, and various evaluations were performed.

(Example 8)
A biaxially oriented polyester film was obtained in the same manner as in Example 6 except that the lamination ratio was as shown in the table, and various evaluations were performed.

(Example 9)
A biaxially oriented polyester film was obtained in the same manner as in Example 8 except that the production conditions were as shown in the table, and various evaluations were performed.

(Example 10)
A biaxially oriented polyester film was obtained in the same manner as in Example 8, except that the layer structure was a two-layer structure of B1 layer/A layer, and various evaluations were performed.

(Example 11)
A biaxially oriented polyester film was obtained in the same manner as in Example 10 except that the production conditions were as shown in the table, and various evaluations were carried out.

(Example 12)
A biaxially oriented polyester film was obtained and various evaluations were performed in the same manner as in Example 8, except that the radius of curvature of the curved glass used for visibility evaluation was as shown in the table.
(Example 13)
A biaxially oriented polyester film was obtained and various evaluations were performed in the same manner as in Example 8, except that the radius of curvature of the curved glass used for visibility evaluation was as shown in the table.

(Example 14)
A biaxially oriented polyester film was obtained and various evaluations were performed in the same manner as in Example 8, except that the radius of curvature of the curved glass used for visibility evaluation was as shown in the table.

(Example 15)
A biaxially oriented polyester film was obtained and various evaluations were performed in the same manner as in Example 8, except that the radius of curvature of the curved glass used for visibility evaluation was as shown in the table.

(Example 16)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the production conditions were as shown in the table, and various evaluations were carried out.

(Example 17)
A biaxially oriented polyester film was obtained in the same manner as in Example 8 except that the thickness of each layer was as shown in the table, and various evaluations were performed.

(Example 18)
A biaxially oriented polyester film was obtained in the same manner as in Example 8 except that the thickness of each layer was as shown in the table, and various evaluations were performed.

(Comparative example 1)
A biaxially oriented polyester film was obtained and various evaluations were carried out in the same manner as in Example 1, except that the A-layer extruder cylinder temperature was 280° C. and the production conditions were as shown in the table.

(Comparative example 2)
A biaxially oriented polyester film was obtained in the same manner as in Comparative Example 1 except that the production conditions were as shown in the table, and various evaluations were performed.

(Comparative Example 3)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the A layer extruder cylinder temperature was 270 ° C., the B layer extruder cylinder temperature was 260 ° C., and the composition and production conditions were as shown in the table. An evaluation was carried out.
(Comparative Example 4)
A biaxially oriented polyester film was obtained and subjected to various evaluations in the same manner as in Example 1, except that the A-layer extruder cylinder temperature was 270° C. and the composition and production conditions were as shown in the table.
(Comparative Example 5)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the A layer extruder cylinder and the B layer extruder cylinder were each set to 270° C., and the composition and production conditions were as shown in the table, and various evaluations were performed. .

The polyester film of the present invention is preferably used as a film to be attached to curved glass because it can suppress warping and peeling of the film after being attached to curved glass.

Claims (10)

A biaxially oriented polyester film for attaching to glass having a curved surface with a radius of curvature of 0.5 mm or more and 200 mm or less, wherein the 50% elongation stress at 150 ° C. is P1 (MPa), and immediately after 50% elongation at 150 ° C., 50 When the stress after 60 seconds of holding the % elongation state is P2 (MPa), two Axially oriented polyester film. However, the elongation stress is a value obtained under elongation conditions of a sample length of 50 mm, a measurement width of 30 mm, and an elongation rate of 300 mm/min.
5≦P1≦80 (i)
5≦{(P1−P2)/P1×100}≦25 (ii) 2. The biaxially oriented polyester film according to claim 1, wherein the difference of {(P1−P2)/P1×100} between the main orientation axis direction and the direction perpendicular to the main orientation axis direction is 0 or more and 5 or less. 3. According to claim 1 or 2, the degree of curl of the sample length after being stretched by 50% at 150° C. in the direction of the main orientation axis and in the direction perpendicular to the direction of the main orientation axis is 0.5 mm or more and 1,200 mm or less. biaxially oriented polyester film. Here, the degree of curl refers to the radius of curvature determined from the end face of a sample cut into a sample length of 50 mm after measurement of elongation. 4. The film according to any one of claims 1 to 3, which has an in-plane retardation of 50 nm or more and 750 nm or less. The film according to any one of claims 1 to 4, further comprising a coating layer on at least one side. An adhesive layer/film laminate in which the film according to any one of claims 1 to 5 and an adhesive layer are laminated. A curable resin layer/film laminate in which the film according to any one of claims 1 to 5 and a curable resin layer are laminated. An adhesive layer/film/curable resin layer laminate, wherein an adhesive layer is laminated on one side of the film according to any one of claims 1 to 5, and a curable resin layer is laminated on the other side. The laminate according to any one of claims 5 to 8, further comprising a polyester film laminated on at least one surface. 9. The film according to any one of claims 1 to 8 , or a curved glass composite obtained by laminating a film laminate and a curved glass, wherein the film has a thickness tmin at the thinnest portion and a thickness tmax at the thickest portion, tmax/tmin 1.05 or more and 5 or less, and the curved glass has a curvature radius of 0.5 mm or more and 200 mm or less of the curved surface with the smallest curvature radius among the curved surfaces covered by the film. .