JP6155728B2 - Polyester film for laminated glass - Google Patents

Description

  The present invention relates to a polyester film for laminated glass. In particular, the present invention relates to a polyester film for laminated glass suitable for imparting functionality such as a heat ray shielding function.

  2. Description of the Related Art In recent years, in architectural and vehicle window glasses, functions such as ultraviolet ray shielding and infrared ray shielding (heat ray reflection) have been increasing. As a method for imparting a function to glass, a method using a laminated glass having an intermediate film provided with a functional layer between two glass plates is known. Above all, laminated glass that shields heat from the outside (heat-shielded laminated glass) suppresses the inflow of heat from the outside of the summer, especially sunlight, and reduces the temperature rise in the room and the interior of the car, thereby reducing the amount of air conditioning used. Because it can reduce and contribute to energy saving, it is attracting attention as a window glass of buildings and windows of vehicles such as automobiles and trains.

  As such a heat ray shielding laminated glass, a laminated glass in which a plurality of glasses are bonded with an intermediate film formed of a resin having a heat ray shielding function is widely used. For example, a heat ray absorbing agent is contained in the resin forming the intermediate film and the heat ray is shielded by the heat ray absorbent (for example, Patent Document 1), or a heat ray shielding layer is vacuum-deposited on a film formed of polyester or the like. There is known a method (for example, Patent Documents 2 to 4) using a laminate formed by a method, a sputtering method, a coating method, or the like as an intermediate film.

JP-A-8-217500 JP-A-56-32352 JP-A-6-191906 JP 2000-927 A

  However, in the method using a heat ray absorbent as in Patent Document 1, the glass temperature partially rises by absorbing heat rays incident from the outside, and the glass body may be damaged due to a difference from the outside air temperature. . Moreover, in the method of laminating a heat ray shielding layer on a film formed of polyester or the like as in Patent Documents 2 to 4, oligomers are precipitated from the film formed of polyester or the like due to the thermal load applied when laminating the heat ray shielding layer. However, this may impair transparency. Analysis of this oligomer gave the knowledge that the cyclic trimer is the main component. Therefore, in order to suppress the decrease in the transparency of the polyester film due to the heat load, it is necessary to suppress the precipitation of the cyclic trimer on the film surface. Moreover, when using for the laminated glass of a shape with a curved surface, a film may not follow the curved surface of glass, a wrinkle may arise and an external appearance may be impaired.

  In view of the problems of the prior art described above, the present invention maintains transparency by suppressing the precipitation of oligomers (particularly cyclic trimers) even in the step of laminating a heat ray shielding layer on a polyester film, and laminated glass. It is an object of the present invention to provide a polyester film for laminated glass having a good appearance without causing wrinkles even in the forming step.

In order to solve the above problems, the present invention has the following configuration.
(1) A polyester film composed of at least three layers, wherein both outermost polyester layers satisfy the following requirements (a), (b) and (c), and the haze of the polyester film is 2. A polyester film for laminated glass which is 0% or less and the internal haze of the polyester film is 1.0% or less.
(A) The thickness of both polyester layers of the outermost layer is 5 μm or more. (B) The cyclic trimer content of the polyester composition constituting both polyester layers of the outermost layer is the polyester of both outermost layers. 0.5% by weight or less based on the entire polyester composition constituting the layer (c) The polyester composition constituting both polyester layers of the outermost layer contains a germanium element (2) of the outermost layer The germanium element contained in the polyester composition constituting both polyester layers is 10 to 400 ppm relative to the entire polyester composition constituting both outermost polyester layers (1) Polyester film for laminated glass.
(3) The cyclic trimer content contained in the polyester composition constituting the polyester layer excluding the outermost layer is 2.0% by weight relative to the entire polyester composition constituting the polyester layer excluding the outermost layer. The polyester film for laminated glass as described in (1) or (2), which is as follows.
(4) The intrinsic viscosity of the polyester composition constituting both polyester layers of the outermost layer is 0.7 to 0.9 dl / g, and the alignment according to any one of (1) to (3) Polyester film for glass.
(5) The intrinsic viscosity of the polyester composition constituting the polyester layer excluding the outermost layer is 0.4 to 0.7 dl / g, and the alignment according to any one of (1) to (4) Polyester film for glass.
(6) The laminated glass according to any one of (1) to (5), wherein the haze change (ΔH) of the film before and after heating the polyester film at 150 ° C. for 30 minutes is 1.0% or less. Polyester film.
(7) The polyester film for laminated glass according to any one of (1) to (6), wherein the total light transmittance of the polyester film is 88% or more.
(8) The thermal shrinkage rate when the polyester film is heated at 150 ° C. for 30 minutes is 1.0% or more and 5.0% or less in both the film longitudinal direction and the width direction (1) to The polyester film for laminated glass according to any one of (7).
(9) The polyester film according to any one of (1) to (8) has a coating layer on at least one surface, the coating layer contains particles, and the average particle size of the particles is 50 nm to 500 nm. A laminated film for laminated glass, characterized in that

  According to the present invention, it is possible to provide a polyester film for laminated glass that suppresses precipitation of a cyclic trimer and maintains transparency and has a good appearance even in a step of laminating a heat ray shielding layer on a polyester film.

  Embodiments of the present invention will be described below, but the present invention is not construed as being limited to the embodiments including the following examples, and can achieve the object of the invention and depart from the gist of the invention. Various changes within the range not to be made are naturally possible.

  In the polyester film of the present invention, the polyester constituting the polyester film is produced by a polycondensation reaction between a difunctional component such as an aromatic dicarboxylic acid or an alkyl ester thereof and a glycol component, and particularly polyethylene terephthalate is mainly used. What is made into a component is preferable.

  Such polyester may be a copolymer obtained by copolymerizing a small amount of the third component as long as the basic properties of the polyester film of the present invention are not impaired, or may be a mixture of these polyesters. Examples of the copolymer component include dicarboxylic acid components such as 2,6-naphthalenedicarboxylic acid and isophthalic acid, oxycarboxylic acid components such as p-oxyethoxybenzoic acid, and tetramethylene glycol, propylene glycol, neopentyl glycol, poly Examples of the diol component include oxyalkylene glycol, p-xylylene glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, and 5-sodium sulforesorzine.

  The polyester in the present invention can be obtained by a conventionally known method. For example, after obtaining a low-polymerization degree polyester directly by reaction of dicarboxylic acid and diol, a polymerization reaction is performed in the presence of a polymerization catalyst, or a lower alkyl ester of dicarboxylic acid and diol are reacted with a conventionally known transesterification catalyst. Thereafter, it can be obtained by a method of performing a polymerization reaction in the presence of a polymerization catalyst. As the polymerization catalyst, a known catalyst such as an antimony compound, a germanium compound, or a titanium compound can be used.

  The polyester may be converted into chips after solution polymerization and further solid-phase polymerization may be performed as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen.

  The polyester constituting the polyester film of the present invention includes various additives such as antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, viscosity reducers, thermal stabilizers, lubricants, infrared absorption. An agent, an ultraviolet absorber, or the like may be added.

The polyester film of the present invention is a polyester film composed of at least three layers, and both the outermost polyester layers must satisfy the following requirements (a), (b), and (c).
(A) The thickness of both polyester layers of the outermost layer is 5 μm or more. (B) The cyclic trimer content of the polyester composition constituting both polyester layers of the outermost layer is the polyester of both outermost layers. It is 0.5 weight% or less with respect to the whole polyester composition which comprises a layer. (C) The polyester composition which comprises both polyester layers of outermost layer contains a germanium element.

  The polyester film of the present invention has a polyester layer composed of a polyester composition having a low cyclic trimer content in the outermost layer, thereby suppressing precipitation of the cyclic trimer on the film surface due to heating, An increase in haze (deterioration of transparency) due to precipitation of the cyclic trimer can be suppressed. That is, the cyclic trimer content of the polyester composition constituting both polyester layers of the outermost layer is 0.5% by weight or less with respect to the entire polyester composition constituting both polyester layers of the outermost layer. is necessary. Preferably, it is 0.4 weight% or less. When the cyclic trimer content of the polyester composition constituting both polyester layers of the outermost layer exceeds 0.5% by weight, the cyclic trimer is deposited on the surface of the polyester film in the step of laminating the heat ray shielding layer. Transparency deteriorates. In the polyester film of the present invention, the polyester constituting the outermost layer on one side and the polyester constituting the other outermost layer may be the same polyester or different polyesters.

  Moreover, the polyester film of this invention WHEREIN: The cyclic | annular trimer content of the polyester composition which comprises the polyester layer except the outermost layer is 2. with respect to the whole polyester composition which comprises the polyester layer except the outermost layer. It is preferably 0% by weight or less. Preferably, they are 0.5 weight% or more and 1.5 weight% or less. When the cyclic trimer content of the polyester composition constituting the polyester layer excluding the outermost layer exceeds 2.0% by weight, the cyclic trimer content of the polyester composition constituting the outermost polyester layer is reduced. Even if it does, precipitation of the cyclic trimer from the polyester layer except the outermost layer may occur, and the precipitation of the cyclic trimer on the film surface may not be prevented. Moreover, when the cyclic trimer content of the polyester composition constituting the polyester layer excluding the outermost layer is less than 0.5% by weight, it may be difficult to improve the production capacity, When solid phase polymerization is carried out in order to reduce the content of the cyclic trimer, the intrinsic viscosity becomes high and it may be difficult to form a film stably.

  In the polyester film of the present invention, the thicknesses of both the outermost polyester layers must be 5 μm or more. Preferably it is 7 micrometers or more, More preferably, it is 10 micrometers or more. When the thickness is less than 5 μm, the cyclic trimer is deposited on the film surface from the polyester layer excluding the outermost layer due to the thermal load received in the step of making the glass into a laminated glass or the step of laminating the heat ray shielding layer. This cannot be suppressed, haze increases, and the transparency when laminated glass is impaired. The upper limit of the thickness of the outermost polyester layer is not particularly defined, but if it exceeds 30 μm, stable film formation may be difficult or productivity may be difficult to improve.

  In general, as a method for producing a polyester having a low cyclic trimer content, a polyester obtained by melt polymerization is further subjected to solid-phase polymerization at a temperature below the melting point of the polyester, A method of performing heat treatment under an active gas is known. However, after obtaining a polyester having an intrinsic viscosity of, for example, 0.45 to 0.70 dl / g by melt polymerization, solid phase polymerization is performed to obtain a polyester having a reduced cyclic trimer content. Since it becomes as high as 0.70 dl / g or more, the melt viscosity at the time of melt extrusion is high, and stable film formation may be difficult. Moreover, when melt viscosity is high, the load to an extruder becomes large and it may become difficult to raise production capacity. That is, a single-layer polyester film made of polyester having a low cyclic trimer content and a high intrinsic viscosity suppresses cyclic trimer precipitation on the film surface and maintains high transparency when subjected to a thermal load. Although it is possible, it is difficult to stably form a film, and it is difficult to improve production capacity. In order to make the intrinsic viscosity of the polyester after solid phase polymerization stable enough to form a film stably, the intrinsic viscosity of the polymer obtained by melt polymerization is lowered to, for example, 0.45 dl / g or less, and this is subjected to solid phase polymerization. Although it is possible to obtain a polyester with a low intrinsic viscosity and a low cyclic trimer, if the intrinsic viscosity after melt polymerization is low, the diameter when discharging into a strand after melt polymerization becomes unstable, and the resulting chip shape Is not stable. For example, in the case of solid-phase polymerization of polyethylene terephthalate, the polymerization rate of solid-phase polymerization is improved by removing ethylene glycol generated by the polycondensation reaction outside the system. When solid phase polymerization is used, there is a difference in the surface area of each chip, so that the degree of polymerization (inherent viscosity) varies greatly. When film formation is performed using such a polyester chip having a large degree of polymerization (intrinsic viscosity), it is difficult to break the film during film formation or to obtain a film having stable characteristics. In addition, when a film is formed using a polyester chip having a large variation in shape, it may cause a biting failure when supplied to an extruder. In addition, as a method of reducing the content of the cyclic trimer, in the method of heat treatment under an inert gas at normal pressure, solid phase polymerization does not proceed and the intrinsic viscosity does not increase, but acetaldehyde generated during heating Since the decomposition gas such as is not excluded from the system, the color tone and transparency are likely to deteriorate. Therefore, it is a polyester film consisting of at least three layers, and by forming both polyester layers of the outermost layer satisfying the requirements of (a), (b), and (c), stable film formation is possible. In addition, the load on the extruder can be reduced and the production capacity can be easily increased.

  In the polyester film of the present invention, the intrinsic viscosity of the polyester composition constituting both the outermost polyester layers is preferably 0.7 to 0.9 dl / g. Moreover, it is preferable that the intrinsic viscosity of the polyester composition which comprises the polyester layer except an outermost layer is 0.4-0.7 dl / g. By setting the intrinsic viscosity of the polyester composition within the above range, stable film formation can be achieved, and the load on the extruder can be reduced to easily increase the production capacity.

  The thickness of the polyester film of the present invention is not particularly limited as long as it can be formed as a film, but is usually 38 to 300 μm, preferably 50 to 125 μm. When the film thickness is thinner than 38 μm, it is difficult to process the laminated glass. On the other hand, when the film thickness is thicker than 300 μm, it is not preferable because the film surface is likely to be scratched in the film forming process, and defects may increase.

  The polyester film of the present invention needs to have an internal haze of 1.0% or less. In the present invention, the internal haze is a value obtained by a measurement method described later, and excludes the influence of the film surface shape (protrusions, irregularities, etc.) caused by foreign matter or particles inside the film, and the transparency of the film. It is an index representing Preferably it is 0.8% or less, More preferably, it is 0.5% or less. When a laminated glass is formed using a polyester film having an internal haze exceeding 1.0%, transparency is impaired and visibility is deteriorated. In order to set the internal haze to the above range, a method of reducing the particles contained in the polyester constituting the polyester film, a method of reducing the cyclic trimer contained in the polyester constituting the polyester film, and a polyester film are constituted. Examples thereof include using a polyester obtained by using a catalyst (for example, germanium) that hardly generates foreign matters as the polyester.

Furthermore, the polyester film of the present invention needs to have a haze of 2.0% or less. In the present invention, the haze is a value obtained by a measurement method described later, and is an index representing transparency like the internal haze, but not only the haze caused by foreign matter or particles inside the film, but also the film surface. It also includes the influence of the shape (projections and irregularities). Preferably it is 1.5% or less. When producing laminated glass, a heat ray shielding layer and an intermediate film are laminated on the polyester film, so the decrease in transparency due to the shape of the polyester film surface (projections, irregularities, etc.) is partially canceled by the layer laminated on the polyester film ( Although the deterioration of transparency is improved), if the haze of the polyester film is larger than 2.0%, the decrease in transparency due to the shape of the polyester film surface (protrusions, unevenness, etc.) is canceled (improvement of transparency is improved) It cannot be squeezed, and transparency is impaired when a laminated glass is used. In order to make the haze in the above range, a method of reducing the particles contained in the polyester constituting the outermost layer of the polyester film, a method of reducing the cyclic trimer contained in the polyester constituting the outermost layer of the polyester film, Examples include using a polyester obtained by using a catalyst (for example, germanium) that does not easily generate foreign substances as the polyester constituting the outermost layer of the polyester film. The polyester film of the present invention has a total light transmittance of 88%. The above is preferable. More preferably, it is 90% or more. When the total light transmittance is less than 88%, a film obtained by laminating a heat ray shielding layer or the like on a polyester film has a low light transmittance and may deteriorate visibility. On the other hand, when the heat ray shielding component is reduced in order to prevent deterioration in visibility, the target heat ray shielding performance may not be achieved.

  The polyester film of this invention needs to contain a germanium element in the polyester composition which comprises both the polyester layers of outermost layer. By containing germanium element in the polyester composition constituting both polyester layers of the outermost layer, an increase in cyclic trimer content in the film forming process is suppressed, and a heat ray shielding layer is laminated on the polyester film. It is possible to suppress the precipitation of the cyclic trimer on the film surface due to the heat load. The reason is estimated as follows. As a polymerization catalyst for polyester, an antimony compound, a germanium compound, a titanium compound, or the like is generally known. However, a germanium compound has a lower thermal decomposition activity than an antimony compound or a titanium compound. Therefore, the polyester obtained using a germanium compound as a polymerization catalyst is considered to be able to suppress the progress of thermal decomposition even under conditions where a thermal load is applied, and to suppress the formation of a cyclic trimer. . Moreover, since the polyester obtained by performing polycondensation reaction using a germanium compound has few foreign materials, transparency is favorable and it can make an internal haze and a haze small. From the viewpoint of suppressing the formation of the cyclic trimer and the precipitation of the cyclic trimer on the film surface, and from the viewpoint of making the internal haze of the polyester film a preferable range, in the polyester composition constituting the outermost polyester layer It is preferable that the germanium element contained in is 10 to 400 ppm with respect to the entire polyester composition constituting the outermost polyester layer.

  The polyester film of the present invention preferably has a haze change (ΔH) of 1.0% or less before and after heating at 150 ° C. for 30 minutes. Preferably it is 0.7% or less, More preferably, it is 0.5% or less. In particular, since the polyester film of the present invention is used for laminated glass, when a heat ray shielding layer or the like is laminated on the polyester film, when ΔH is larger than 1.0%, the heat ray shielding layer is laminated on the polyester film. The haze of the film rises due to the heat load that is received, and the transparency may be lowered when it is made into laminated glass.

  The increase in haze due to heating is thought to be due to the precipitation of cyclic trimers on the film surface. In order to make ΔH within the above range, the cyclic trimer content of the polyester constituting both polyester layers of the outermost layer is reduced, or the polyester constituting both polyester layers of the outermost layer is subjected to heat load. There is a method using a polyester in which the amount of cyclic trimer precipitated is small.

  The polyester film of the present invention preferably has a heat shrinkage rate of not less than 1.0% and not more than 5.0% in the film longitudinal direction and the width direction when heat-treated at 150 ° C. for 30 minutes. Preferably they are 1.5% or more and 4.0% or less. If the heat shrinkage ratio is less than 1.0%, the film may not follow the shape of the laminated glass when processed into a laminated glass, which may cause an appearance defect. Wrinkles that occur when processing into laminated glass are more likely to occur as the curved surface of the laminated glass is curved. Therefore, by limiting the heat shrinkage rate to the above range, the shape of applicable laminated glass is limited. Disappears. On the other hand, if the thermal shrinkage rate is larger than 5.0%, a dimensional change occurs due to a thermal load applied when a heat ray shielding layer or the like is laminated on the polyester film, which causes a reduction in width or deterioration of flatness. There is. The thermal shrinkage rate can be set to the above range by controlling the film forming conditions (particularly the heat treatment conditions). For example, when the film of the present invention is a film made of polyethylene terephthalate, the heat shrinkage rate can be set to the above range by setting the heat treatment temperature after the stretching step to a range of 180 to 240 ° C.

  Moreover, since the polyester film of this invention is used for a laminated glass use, when laminating | stacking a heat ray shielding layer, it is preferable that it is a laminated | multilayer film which has an application layer on the at least single side | surface of a polyester film. The coating layer can be formed by applying a coating liquid containing the resin composition forming the coating layer to the film and then drying the coating liquid. Examples of the method for forming the coating layer on the polyester film include an in-line coating method in which coating is performed in the film manufacturing process, and an off-line coating method in which coating is performed in a process separate from the film manufacturing process. Among them, the in-line coating method in which coating is performed in the film forming process has advantages in manufacturing cost because the film formation of the polyester film and the formation of the coating layer can be performed simultaneously, and the film is stretched after coating. This is preferable because it is easy to reduce the thickness of the coating layer. As the solvent of the coating liquid, either an aqueous system or a solvent system is used in the case of the offline coating method, but an aqueous system is preferable in the case of the in-line coating method.

  As a resin composition which forms the coating layer of the polyester film of this invention, what consists of a combination of a crosslinking agent and various binder resin is preferable. The binder resin preferably contains at least one polymer selected from polyester, acrylic and polyurethane from the viewpoint of adhesiveness. Each of the above polymers shall contain their derivatives. The derivative here refers to a polymer obtained by reacting a reactive compound with a copolymer or a functional group with another polymer.

  In addition to the above resins and crosslinking agents, the additives constituting the coating layer include various additives such as surfactants, solvents, antioxidants, heat stabilizers, weathering stabilizers, ultraviolet absorbers, Organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, and the like may be blended within a range that does not impair optical properties. In particular, those containing particles in the coating layer are more preferable because the slipperiness and blocking resistance are improved. In this case, inorganic particles are preferable as the contained particles, and silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, and the like can be used.

  In the present invention, the resin constituting the coating layer contains particles, and the average particle size of the particles obtained by the measurement method described later is 50 nm or more and 500 nm or less, while having high transparency, a laminated film It is preferable because it can provide easy slipperiness. The upper limit of the average particle size of the particles contained in the resin constituting the coating layer is preferably 400 nm or less, more preferably 300 nm or less. When the average particle size of the particles is larger than 500 nm, light may be scattered on the surface of the particles and the transparency of the laminated glass may deteriorate. When the average particle size of the particles is less than 50 nm, the formed protrusions are small, so that the slipping property of the film is deteriorated and wrinkles may be generated when the film is wound. In addition, the amount of particles added can be determined by aggregating particles when the mixing ratio of the resin composition in the coating liquid containing the resin composition forming the coating layer is 0.05 to 5% by weight in terms of solid content. This is preferable because it can suppress the formation of coarse protrusions and the deterioration of transparency. More preferably, it is 0.1 to 3% by weight. When the amount of particles to be added is more than 5% by weight, transparency may deteriorate due to an increase in the number of irregularities on the surface of the laminated film. On the other hand, when the amount of added particles is less than 0.05% by weight, the number of protrusions on the surface of the laminated film is reduced, so that the slipping property is deteriorated and wrinkles may be generated in the laminated glass forming step.

  Next, although the detail of the manufacturing method of the polyester film of this invention is demonstrated using the polyethylene terephthalate film as the example, this invention is limited to only the thing obtained by this example, and is not interpreted.

  The polyethylene terephthalate chip is dried, then supplied to two extruders, melted at 280 to 300 ° C., laminated using a three-layer feed block, and discharged from the die. The discharged sheet is extruded onto a cooling body such as a casting drum, and is cooled and solidified to obtain a casting film. At this time, using a wire-like, tape-like, needle-like or knife-like electrode, it is brought into close contact with a cooling body such as a casting drum by electrostatic force and rapidly cooled and solidified, or from a slit-like, spot-like, or planar device. A method in which air is blown out and brought into close contact with a cooling body such as a casting drum to rapidly cool and solidify is preferable.

  The casting film thus obtained is stretched within a range of 2.5 to 4.5 times in the longitudinal direction with a roll heated to 75 to 110 ° C. to obtain a uniaxially stretched film.

  The uniaxially stretched film thus obtained is subjected to surface treatment such as corona treatment, flame treatment, and plasma treatment as necessary, and then functions such as slipperiness, easy adhesion, and antistatic properties are provided. In order to apply, a coating solution is applied to one side or both sides by a coating method. Next, both ends of the film are held with clips and stretched in the range of 2.5 to 5.0 times in the width direction at 90 to 150 ° C., followed by heat treatment at a temperature of 180 to 240 ° C. During the heat treatment step, a relaxation treatment of 0.5 to 5% may be performed in the width direction as necessary.

  The polyester film of the present invention obtained as described above is used for laminated glass. For example, a laminated glass excellent in transparency can be obtained by using a film in which a polyvinyl butyral layer is laminated on at least one side of the polyester film of the present invention as an intermediate layer and sandwiching two glass plates on both sides of the intermediate layer. Can do. The polyvinyl butyral layer may contain various functional agents that are usually added. The glass plate is not particularly limited as long as it is of a type used for automobile window glass, building window glass, and the like. As a laminated structure of a polyester film, a polyvinyl butyral layer, and two glass plates, for example, the structure of a glass plate / polyvinyl butyral layer / polyester film / polyvinyl butyral layer / glass plate is exemplified, but it is not limited to such an embodiment. Absent. Moreover, it is preferable to use what provided the functionality by providing a heat ray shielding layer etc. on the surface of the polyester film, since a highly functional laminated glass can be provided.

  The following examples further illustrate the invention. However, the present invention is not limited to the following examples without departing from the gist thereof. In addition, the evaluation method of the physical property in a following example and a comparative example is as follows.

(1) Haze and total light transmittance Three points (three pieces) of a square polyester film sample having a side of 5 cm are prepared. The sample is then allowed to stand for 40 hours in a normal state (23 ° C., relative humidity 50%). For each sample, a turbidity watch “NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd. is used. The haze measurement is JIS “How to determine the haze of a transparent material” (K7136 2000 version), and the total light transmittance measurement is JIS “ The test is carried out by a method in accordance with “Test method for total light transmittance of transparent plastic material” (K7361-1, 1997 edition). The haze and total light transmittance of each of the three points (three) are averaged to obtain the haze and total light transmittance of the polyester film.

(2) Haze change (ΔH)
First, the haze is measured in the same manner as (1) to determine the haze before processing. Next, a polyester film sample having a length of 30 cm and a width of 20 cm was prepared and suspended in a hot air oven “HIGH-TEMP-OVEN PHH-200” manufactured by ESPEC CORP. Set to 150 ° C. (air flow gauge “7”). Heat for 30 minutes. Thereafter, the polyester film sample was allowed to stand for 1 hour by air cooling. After that, 3 points (3 pieces) of a square-shaped polyester film sample having a side of 5 cm are cut out from the polyester film sample, the haze is measured in the same manner as (1), and the values of 3 points (3 pieces) are averaged and processed. Of haze. The haze change (ΔH) was determined by the following formula.

Haze change (ΔH) = (Haze after treatment) − (Haze before treatment)
(3) Internal haze Internal haze was measured using fully automatic direct reading haze computer “HGM-2DP” manufactured by Suga Test Instruments Co., Ltd. The polyester film was immersed in a tetralin solution, and the internal haze was determined from the following formula from the diffuse transmittance and the total light transmittance.

Internal haze (%) = diffuse transmittance / total light transmittance × 100
(4) Measurement of layer thickness A polyester film was cut into an ultrathin film section, and the section was observed with a transmission electron microscope (TEM) by RuO ₄ staining, OsO ₄ staining, or a staining ultrathin section method by double staining of both. I took a photo. The layer thickness of the polyester layer was measured from the cross-sectional photograph.

(5) Intrinsic viscosity The value calculated from the following formula from the solution viscosity measured at 25 ° C in orthochlorophenol was used. That is, ηsp / C = [η] + K [η] ² · C
Here, ηsp = (solution viscosity / solvent viscosity) −1, C is the weight of dissolved polymer per 100 m of solvent (g / 100 ml, usually 1.2), and K is the Huggins constant (assuming 0.343). The solution viscosity and solvent viscosity were measured using an Ostwald viscometer.

  If there is insoluble matter such as inorganic particles in the solution in which the polyester composition is dissolved, the solution is filtered and weighed, and the value obtained by subtracting the weight of the filtrate from the weight of the measured sample is taken as the measured sample weight. Correction was performed.

(6) Cyclic trimer content 20 mg of the polyester composition is dissolved in OCP (o-chlorophenol) at 150 ° C. for 30 minutes and cooled at room temperature. Thereafter, 1,4-diphenylbenzene was added as an internal standard, 2 ml of methanol was added and the polymer was separated using a high-speed centrifuge, and the liquid layer portion was then analyzed using a high-speed liquid chromatograph LC-10ADvp manufactured by Shimadzu Corporation. It was measured.

  In the case of measuring the cyclic trimer content of the polyester composition constituting the outermost polyester layer of the polyester film, the polyester composition constituting the polyester layer is cut out from the outermost layer of the polyester film. .

  Moreover, after measuring the ratio of the layer thickness of each layer of a polyester film by the method of (4), when measuring cyclic trimer content of the polyester composition which comprises the polyester layer except the outermost layer of the polyester film. The cyclic trimer content of the entire polyester film is measured in the same manner as described above, and the cyclic trimer content of the polyester composition constituting the polyester layer excluding the outermost layer is determined by weight proportional distribution.

  If there is insoluble matter such as inorganic particles in the solution in which the polyester composition is dissolved, the solution is filtered and weighed, and the value obtained by subtracting the weight of the filtrate from the weight of the measured sample is taken as the measured sample weight. Correction was performed.

(7) Heat shrinkage rate Two lines are drawn on the surface of the polyester film so that the width is 10 mm and the measurement length is about 100 mm, and the distance between the two lines is measured at 23 ° C., which is defined as L0. This polyester film sample was left in a hot air oven “HIGH-TEMP-OVEN PHH-200” manufactured by ESPEC CORP. Set at 150 ° C. (air flow gauge “7”) for 30 minutes under a load of 3 g, and then again 2 The distance between the lines of the book was measured at 23 ° C., and this was taken as L1, and the heat shrinkage rate was determined by the following equation. The measurement was carried out by 5 samples in the longitudinal direction and in the width direction, and the average value was evaluated.
Thermal contraction rate (%) = (L0−L1) / L0 × 100
When analyzing the film, if the longitudinal direction or the width direction of the film is not known, the direction having the maximum refractive index in the film is regarded as the width direction, and the direction orthogonal thereto is regarded as the longitudinal direction. The direction of the maximum refractive index in the film may be obtained by measuring the refractive index in all directions of the film with an Abbe refractometer. For example, the direction of the slow axis with a phase difference measuring device (birefringence measuring device) It may be obtained by determining.

(8) Metal content in the polyester composition constituting the film The metal content in the polyester composition constituting the film was measured using a fluorescent X-ray analyzer (model number: 3270) manufactured by Rigaku Corporation. The content (ppm) of the polyester composition constituting the polyester film was determined by line measurement. The quantification was performed using a calibration curve of the strength and each element amount prepared using a sample with a known metal amount quantified in advance using an atomic absorption method or the like.
In addition, when measuring metal content in the polyester composition which comprises the outermost layer of a polyester film, the sample was extract | collected by shaving off a polyester composition from the outermost layer of a polyester film, and the measurement was performed.

(9) Average particle diameter of particles in coating layer A laminated film obtained by laminating a coating layer on a polyester film is cut into ultra-thin sections, and the cross section is stained with RuO ₄ staining, OsO ₄ staining, or double staining of both. According to the method, a TEM (transmission electron microscope) was used for observation at a magnification of 200,000 times, and a photograph was taken. The particle diameter (equivalent sphere diameter) in the coating layer was measured from the cross-sectional photograph, the particle diameters of the particles observed in 100 fields of view were determined, and the average value was taken as the average particle diameter.

(10) Appearance of laminated glass The appearance of the laminated glass obtained by using the obtained film was visually evaluated and evaluated according to the following criteria.
(Double-circle): When neither a wrinkle nor cloudiness is visible on the film (intermediate film) inside the laminated glass. Appearance is good.
○: When the film (intermediate film) inside the laminated glass does not appear cloudy but slightly wrinkles are visible. Appearance normal.
Δ: When the film (intermediate film) inside the laminated glass is slightly cloudy and no wrinkles are visible, or when it is slightly cloudy and the wrinkles are slightly visible. Appearance is slightly inferior.
X: When the film (intermediate film) inside the laminated glass appears to be cloudy or slightly cloudy and has many wrinkles. Poor appearance.
(Production Example 1-Polyester A1)
An ester in which about 123 parts by weight of bis (hydroxyethyl) terephthalate was previously charged in a slurry of 45 parts by weight of ethylene glycol with respect to 100 parts by weight of high-purity terephthalic acid and maintained at a temperature of 250 ° C. and a pressure of 1.2 × 10 ⁵ Pa. The esterification reaction layer was sequentially supplied over 4 hours, and after the completion of the supply, the esterification reaction was further performed over 1 hour, and the esterification reaction product was transferred to a polycondensation tank. Subsequently, 0.01 parts by weight of ethyl diethylphosphonoacetate was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, and 0.04 parts by weight of magnesium acetate tetrahydrate was further added as a polymerization catalyst. It added so that it might become 0.04 weight part in conversion of an antimony atom with respect to polyester which can obtain an antimony trioxide. Thereafter, while stirring the low polymer at 30 rpm, the reaction system was heated from 250 ° C. to 285 ° C. over 60 minutes and the pressure was reduced to 40 Pa. The time to reach the final pressure was 60 minutes. When the predetermined stirring torque is reached, the reaction system is purged with nitrogen, returned to normal pressure, the polycondensation reaction is stopped, discharged into cold water at a temperature of 20 ° C. in a strand form, and immediately cut to obtain polyester A1 pellets. It was. The time from the start of decompression to the arrival of the predetermined stirring torque was 3 hours. The obtained polyester A1 had an intrinsic viscosity of 0.65 dl / g and a cyclic trimer content of 1.05% by weight.
(Production Example 2-Polyester A2)
Polyester A2 was obtained in the same manner as for polyester A1, except that in the method for producing polyester A1, the amount of antimony trioxide added was changed to 0.02 parts by weight in terms of antimony atoms. Polyester A2 obtained had an intrinsic viscosity of 0.58 dl / g and a cyclic trimer content of 0.90% by weight.
(Production Example 3-Polyester B1)
A slurry of 60 parts by weight of ethylene glycol with 100 parts by weight of dimethyl terephthalate is charged with about 123 parts by weight of bis (hydroxyethyl) terephthalate in advance together with 0.06 parts by weight of magnesium acetate tetrahydrate, a temperature of 250 ° C., a pressure of 1 .Sequentially supplied to the esterification reaction layer held at 2 × 10 ⁵ Pa over 4 hours, and after completion of the supply, the esterification reaction is carried out over another 1 hour, and this esterification reaction product is transferred to the polycondensation tank did. Subsequently, 0.026 part by weight of trimethyl phosphate is added to the polycondensation reaction tank to which the esterification reaction product has been transferred, and 0.02 weight of germanium dioxide dissolved finely in ethylene glycol as a polymerization catalyst. A solution of parts in tetraethylammonium hydroxide was added. Thereafter, while stirring the low polymer at 30 rpm, the reaction system was heated from 250 ° C. to 285 ° C. over 60 minutes and the pressure was reduced to 40 Pa. The time to reach the final pressure was 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen, returned to normal pressure, the polycondensation reaction was stopped, discharged into cold water at a temperature of 20 ° C. in a strand form, and immediately cut to obtain polyester pellets. The time from the start of decompression to the arrival of the predetermined stirring torque was 3 hours. The obtained polymer had an intrinsic viscosity of 0.64 dl / g and a cyclic trimer content of 1.03% by weight.

The polymer was dried under reduced pressure at 150 ° C., and then solid state polymerization was performed at a temperature of 240 ° C. for 8 hours under reduced pressure (133 Pa or less). The polymer was taken out and washed with water to obtain polyester B1 pellets. It was. The obtained polyester B1 had an intrinsic viscosity of 0.78 dl / g and a cyclic trimer content of 0.28% by weight.
(Production Example 4-Polyester B2)
A polyester B2 was obtained in the same manner as the polyester B1, except that the solid-state polymerization temperature was 220 ° C. in the production method of the polyester B1. The obtained polyester B2 had an intrinsic viscosity of 0.72 dl / g and a cyclic trimer content of 0.38% by weight.

(Production Example 5-Polyester A3)
In the production method of polyester A1, the same as polyester A1, except that after adding antimony trioxide, silicon dioxide having an average particle size of 2.1 μm was added to 0.1% by weight based on the polyester. Thus, polyester A3 was obtained. Polyester A2 obtained had an intrinsic viscosity of 0.64 dl / g and a cyclic trimer content of 1.08% by weight.

(Production Example 6—Polyester A4)
The polymer of polyester A1 is dried under reduced pressure of 150 ° C., then subjected to solid phase polymerization for 8 hours at a temperature of 240 ° C. under reduced pressure (133 Pa or less), taken out, washed with water, and pellets of polyester A4 Got. The obtained polyester A4 had an intrinsic viscosity of 0.78 dl / g and a cyclic trimer content of 0.35% by weight.

(Production Example 7-Polyester B3)
In the production method of polyester B1, polyester B3 was obtained in the same manner as polyester B1, except that solid phase polymerization was not performed. The obtained polymer had an intrinsic viscosity of 0.64 dl / g and a cyclic trimer content of 1.03% by weight.

( Reference Example 1)
After drying polyester A1 and polyester B1 under reduced pressure (1 Torr) for 6 hours at 150 ° C., polyester B1 is used as a raw material for the outermost polyester layer (B layer), and polyester A1 is removed from the outermost layer (A layer) Were fed to two extruders, and each was melted at 285 ° C. It is laminated in 3 layers of B layer / A layer / B layer by a feed block, extruded into a sheet form from a die, wound around a casting drum cooled to 20 ° C. using an electrostatic application method, cooled and solidified, and unstretched film Was made.

  The obtained unstretched film was heated to 95 ° C. with a heated roll group and an infrared heater and stretched 3.3 times in the longitudinal direction to obtain a uniaxially stretched polyester film. Next, the film was stretched 3.6 times in the width direction at 110 ° C. and heat-treated at 215 ° C. At this time, in the heat treatment step, a relaxation treatment of 2.5% was performed in the width direction. Thereby, a polyester film having a thickness of 100 μm was obtained. The breakdown of the layer thickness of the polyester layer (A layer) excluding the outermost layer of the polyester film and the outermost polyester layer (B layer) was B layer / A layer / B layer = 7 μm / 86 μm / 7 μm.

  This polyester film has a total light transmittance of 89.0%, a haze of 0.4%, an internal haze of 0.2%, and a cyclic trimer of a polyester composition constituting the outermost polyester layer (B layer). The content was 0.43% by weight, and the cyclic trimer content of the polyester composition constituting the polyester layer excluding the outermost layer was 1.18% by weight. Further, the haze change ΔH of the film before and after being heated at 150 ° C. for 30 minutes was 0.4%, and the heat shrinkage ratio was as good as 1.5% in the longitudinal direction and 1.4% in the width direction.

The obtained polyester film and polyvinyl butyral film were inserted between two watch glasses (made of ordinary glass) having a diameter of 120 mm, a thickness of 2 mm, and a depth of 9 mm, as described below.
First interlayer film: polyvinyl butyral film (Sekisui Chemical Co., Ltd., “S-LEC” (registered trademark) Film thickness 0.76 mm)
Second intermediate film: Polyester film (thickness 0.1 mm) formed as described above
Third interlayer film: polyvinyl butyral film (Sekisui Chemical Co., Ltd., “S-LEC” (registered trademark) Film thickness 0.76 mm)
Next, the two sheets of glass sandwiched between the intermediate films are held at 100 ° C. for 20 minutes, and then placed in an autoclave apparatus. The glass is processed by pressurizing and heating at a pressure of about 10 to 14 kg / cm ² and a temperature of 140 ° C. for 20 minutes. The laminated glass was obtained. About the obtained laminated glass, when the external appearance was evaluated visually, the interlayer film was free from wrinkles and cloudiness and had a good external appearance.

(Example 2)
The lamination ratio of the polyester layer (A layer) excluding the outermost layer and the polyester layer (B layer) of the outermost layer was changed, B layer / A layer / B layer = 5 μm / 90 μm / 5 μm, and the heat treatment temperature was 208 ° C. A polyester film was obtained in the same manner as in Example 1 except that.

(Example 3)
A polyester film was obtained in the same manner as in Example 2 except that polyester A2 was used as a raw material for the polyester layer (A layer) excluding the outermost layer.

Example 4
The lamination ratio of the polyester layer (A layer) excluding the outermost layer and the outermost polyester layer (B layer) was changed to B layer / A layer / B layer = 10 μm / 80 μm / 10 μm, and the heat treatment temperature was 200 ° C. A polyester film was obtained in the same manner as in Example 1 except that.

(Example 5)
A polyester film was obtained in the same manner as in Example 4 except that polyester B2 was used as a raw material for the outermost polyester layer (B layer).

( Reference Example 6)
A polyester film was obtained in the same manner as in Example 1 except that the heat treatment temperature was 230 ° C.

( Reference Example 7)
A polyester film was obtained in the same manner as in Example 1 except that polyester B2 was used as a raw material for the polyester layer (A layer) excluding the outermost layer.

( Reference Example 8)
In the same manner as in Example 1, a uniaxially stretched polyester film was obtained. Next, the coating liquid was applied to both sides of the film by a bar coating method. The composition of the coating solution was as follows: polyester resin having a glass transition point of 81 ° C., polyester resin having a glass transition point of 110 ° C., melamine-based crosslinking agent, oxazoline-based crosslinking agent, colloidal silica having an average particle size of 140 nm (JGC Catalysts & Chemicals Co., Ltd.) Manufactured by “Spherica” (registered trademark) 140) and colloidal silica having an average particle size of 300 nm (“Seahoster” (registered trademark) KE-W30 manufactured by Nippon Shokubai Co., Ltd.) and having a solid content concentration of 8.0% by weight. The weight ratio of the solid content of each component is 44/19/30/5 / 1.5 / 0.5.

  After coating the coating solution, the film was stretched 3.6 times in the width direction at 110 ° C. and heat-treated at 215 ° C. At this time, in the heat treatment step, a relaxation treatment of 2.5% was performed in the width direction. As a result, a polyester film having a thickness of 100 μm in which a coating film of 125 nm on one side was formed on both sides was obtained. The breakdown of the layer thickness of the polyester layer (A layer) excluding the outermost layer of the polyester film and the outermost polyester layer (B layer) was B layer / A layer / B layer = 7 μm / 86 μm / 7 μm.

(Comparative Example 1)
Example 1 except that the lamination ratio of the polyester layer (A layer) excluding the outermost layer and the outermost polyester layer (B layer) was changed to B layer / A layer / B layer = 3 μm / 94 μm / 3 μm. A polyester film was obtained in the same manner as above.

(Comparative Example 2)
A polyester film was obtained in the same manner as in Example 1 except that polyester A1 was used for the outermost polyester layer (B layer).

(Comparative Example 3)
A polyester film was obtained in the same manner as in Example 1 except that polyester A3 was used for the polyester layer (A layer) excluding the outermost layer.

(Comparative Example 4)
A polyester film was obtained in the same manner as in Example 1 except that the polyester A3 was used for the outermost polyester layer (B layer).

(Comparative Example 5)
A polyester film was obtained in the same manner as in Example 1 except that polyester A4 was used for the outermost polyester layer (B layer).

(Comparative Example 6)
A polyester film was obtained in the same manner as in Example 1 except that polyester B1 and polyester A1 were used and a two-layer laminated film having the thickness described in the table was used.
(In the table, “A1:” and “B1” in the terms of the amount of cyclic trimer contained in the polyester composition constituting the outermost polyester layer and the metal content contained in the polyester composition constituting the outermost polyester layer) : "Represents the cyclic trimer and metal content contained in the polyester constituting the layer formed using polyester A1 and polyester B1, respectively.)
(Comparative Example 7)
A polyester film was obtained in the same manner as in Example 1 except that a single film using only polyester B2 was used. In this case, although a polyester film could be obtained, the load on the extruder became high, and the discharge amount from the extruder had to be lowered, resulting in poor productivity. Furthermore, by reducing the discharge amount, the residence time in the melted state in the extruder became longer, and the cyclic trimer content of the polyester film also increased.
The results are shown in Table 1.

  The polyester film of the present invention suppresses the precipitation of the cyclic trimer even in the step of laminating the heat ray shielding layer on the polyester film, and maintains transparency and does not cause wrinkles in the laminated vitrification step. It can be suitably used as a laminated glass film for windows of automobiles and the like.

Claims (9)

A polyester film comprising at least three layers,
Both polyester layers of the outermost layer satisfy the following requirements (a), (b) and (c), the haze of the polyester film is 2.0% or less, and the internal haze of the polyester film is 1 0.0% or less, and the thermal shrinkage rate when the polyester film is heated at 150 ° C. for 30 minutes is 2.1% or more and 5.0% or less in the film longitudinal direction, and 2.0% or more in the film width direction. A polyester film for laminated glass that is 5.0% or less .
(A) The thickness of both polyester layers of the outermost layer is 5 μm or more. (B) The cyclic trimer content of the polyester composition constituting both polyester layers of the outermost layer is the polyester of both outermost layers. 0.5% by weight or less based on the entire polyester composition constituting the layer (c) The polyester composition constituting both outermost polyester layers contains a germanium element The germanium element contained in the polyester composition constituting both polyester layers of the outermost layer is 10 to 400 ppm relative to the entire polyester composition constituting both polyester layers of the outermost layer. The polyester film for laminated glass according to 1. The cyclic trimer content contained in the polyester composition constituting the polyester layer excluding the outermost layer is 2.0% by weight or less based on the entire polyester composition constituting the polyester layer excluding the outermost layer. The polyester film for laminated glass according to claim 1 or 2, wherein: The polyester film for laminated glass according to any one of claims 1 to 3, wherein the polyester composition constituting both polyester layers of the outermost layer has an intrinsic viscosity of 0.7 to 0.9 dl / g. The polyester film for laminated glass according to any one of claims 1 to 4, wherein the intrinsic viscosity of the polyester composition constituting the polyester layer excluding the outermost layer is 0.4 to 0.7 dl / g. The polyester film for laminated glass according to any one of claims 1 to 5, wherein the haze change (ΔH) of the film before and after the polyester film is heated at 150 ° C for 30 minutes is 1.0% or less. The polyester film for laminated glass according to any one of claims 1 to 6, wherein the total light transmittance of the polyester film is 88% or more. It is used for the laminated glass of the shape with a curved surface, The polyester film for laminated glasses in any one of Claims 1-7 characterized by the above-mentioned. The polyester film according to any one of claims 1 to 8 has a coating layer on at least one surface, the resin constituting the coating layer contains particles, and the average particle size of the particles is 50 nm to 500 nm. There is a laminated film for laminated glass.