JP2018044071A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film having an infrared absorption function and an ultraviolet absorption function and capable of avoiding bleeding out of an ultraviolet absorber even when used under environment where it is exposed to solar light.SOLUTION: There is provided a polyester film containing an infrared absorber and an ultraviolet absorber having a reactive functional group, content of the infrared absorber A [wt.%] in the polyester film and thickness T [μm] of the polyester film satisfies 200≥T [μm]×A [wt.%]≥10, and content of the ultraviolet absorber B [wt.%] in the polyester film and thickness T [μm] of the polyester film satisfies 1000≥T [μm]×B [wt.%]≥100.SELECTED DRAWING: None

Description

  The present invention relates to a polyester film having a near infrared absorption function and an ultraviolet absorption function.

  As a technique for imparting a near-infrared absorbing function to a film, a technique for laminating a near-infrared absorbing dye-containing layer on a substrate has been disclosed (Patent Documents 1, 2 and the like).

  It is known that near-infrared absorbing pigments contained in this near-infrared absorbing layer are generally decomposed by ultraviolet rays contained in sunlight, and the performance thereof is deteriorated by long-term use. In particular, an aromatic diimmonium salt compound generally used as a near-infrared absorbing dye is likely to be altered by ultraviolet rays.

  In this regard, Patent Document 1 avoids alteration due to ultraviolet rays by laminating a plastic film substrate on both sides of a near infrared absorbing dye-containing layer and laminating an ultraviolet absorbing layer on one plastic film substrate. Technology is disclosed. Patent Document 2 discloses a technique in which an ultraviolet absorber is contained in an intermediate layer of a substrate having a three-layer structure of “outermost layer / intermediate layer / outermost layer”.

In addition, it is known that the ultraviolet absorber is likely to cause bleeding out of the ultraviolet absorber, particularly in the case of a low molecular type. Bleed-out of the ultraviolet absorber is not preferable because it causes a reduction in film quality and a decrease in adhesion to the functional layer laminated on the film.
In this regard, Patent Document 2 discloses that an ultraviolet absorber is contained in an intermediate layer of a substrate having a three-layer structure of “outermost layer / intermediate layer / outermost layer”, and the ultraviolet absorber is substantially contained in both outermost layers. In other words, a technology has been disclosed that drastically reduces the bleed-out of the ultraviolet absorbent even when a low molecular weight ultraviolet absorbent is used.

  However, in the technique of Patent Document 2, as described above, the outermost layer of the base material having the three-layer structure of “outermost layer / intermediate layer / outermost layer” is configured so that the ultraviolet absorber is not substantially contained. Therefore, when used in an environment that is exposed to sunlight, the surface layer that is most exposed to sunlight tends to deteriorate, and if the surface layer deteriorates, the intermediate layer is directly exposed to ultraviolet rays, thus suppressing bleeding out. There was a problem that the effect could not be expected sufficiently.

JP 2002-301785 A JP 2006-221935 A

  The present invention has been made in view of such circumstances, and has a near-infrared absorbing function and an ultraviolet absorbing function, and even when used in an environment exposed to sunlight, the ultraviolet absorbent bleed out. It is to provide a film that can be avoided.

As a result of intensive studies to solve the above problems, the inventors have found that the above problems can be solved by using a polyester film having a specific configuration, and have completed the following invention.
The present invention provides the following [1] to [4].
[1] A polyester film containing a near-infrared absorber and a UV absorber having a reactive functional group, the content A [wt%] of the near-infrared absorber in the polyester film and the thickness T of the polyester film Polyester film in which [μm] satisfies the following formula (1), and the content B [wt%] of the ultraviolet absorber in the polyester film and the film thickness T [μm] satisfy the following formula (2). .
200 ≧ T [μm] × A [wt%] ≧ 10 (1)
1000 ≧ T [μm] × B [weight%] ≧ 100 (2)
[2] The polyester film according to [1], wherein the ultraviolet absorber has 1 to 2 reactive functional groups in one molecule.
[3] The polyester film according to [1] or [2], wherein the reactive functional group is at least one selected from the group consisting of an amine group, a hydroxyl group, a thiol group, and a hydroxyalkyl group.
[4] The polyester film according to any one of [1] to [3], wherein the near-infrared absorber is a near-infrared absorber having a transition metal element.

The present inventor has found that by using an ultraviolet absorber having a reactive functional group, bleeding out of the ultraviolet absorber can be avoided even when the ultraviolet absorber is present in the outermost layer of the polyester film. Completed. According to the present invention, even when the ultraviolet absorber is present in the outermost layer of the polyester film, bleeding out of the ultraviolet absorber can be avoided.
Further, in the present invention, since the ultraviolet absorber is contained in the polyester film itself and also exists in the outermost layer of the polyester film, even when used in an environment where the outermost layer of the polyester film is exposed to sunlight, The ultraviolet rays contained in are absorbed by the ultraviolet absorber, and the alteration of the near-infrared absorbing dye can be avoided.
Furthermore, in the present invention, since the near-infrared absorber and the ultraviolet absorber are contained in the polyester film itself, a near-infrared-absorbing dye-containing layer is laminated on the substrate as in the past, or A film having a near-infrared absorbing function and an ultraviolet absorbing function can be provided without going through the step of laminating the ultraviolet absorbing layer.

  Hereinafter, the polyester film in one embodiment of the present invention will be described in detail.

<Polyester film>
In the present invention, the polyester film means a film stretched after cooling a melted polyester sheet extruded by a so-called extrusion method, which is melt-extruded from an extrusion die. Or it means what was heat-fixed as needed after extending | stretching what was extruded by the coextrusion method by which all the layers are co-melt-extruded from a nozzle | cap | die.

  Hereinafter, a film having a three-layer structure will be described as the polyester film. However, the polyester film in the present invention may have a single-layer structure or a multilayer structure as long as the purpose is satisfied.

  The polymer constituting each layer of the polyester film having a three-layer structure is mainly a polyester obtained using aromatic dicarboxylic acid or its ester and glycol as main starting materials, and 60% or more of the repeating structural units are ethylene. It refers to a polyester having terephthalate units or ethylene-2,6-naphthalate units. And if it is the conditions which do not deviate from said range, the other 3rd component may be contained. Examples of the aromatic dicarboxylic acid component include terephthalic acid, dimethyl terephthalate, and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxy) Benzoic acid etc.) can be used. In particular, terephthalic acid or dimethyl terephthalate is preferably used. As an example of a glycol component, 1 type, or 2 or more types, such as diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol other than ethylene glycol, can be used, for example. In particular, it is preferable to use ethylene glycol.

  The intrinsic viscosity of the polyester is 0.64 dl / g or more, preferably 0.66 dl / g or more. When the intrinsic viscosity of the polyester is 0.64 dl / g or more, a polyester film having good long-term durability and hydrolysis resistance after wet heat treatment can be obtained. On the other hand, although there is no upper limit of the intrinsic viscosity of the polyester, it is about 0.90 dl / g from the viewpoint of the efficiency of the polycondensation reaction and the prevention of pressure increase in the melt extrusion process. The method for measuring the intrinsic viscosity of the polyester is as described in the examples.

  In the present invention, the polyester can contain inert particles and the like within a range not departing from the object of the present invention, and the method is not particularly limited, but the method of adding in the polymerization step, the particles are kneaded in advance using an extruder, The method etc. which are set as a masterbatch can be employ | adopted. A particularly preferable method is a method in which particles are directly added and mixed in the extrusion step during the film production step. As the extruder at that time, a twin screw extruder with a vent is preferable. Further, in order to improve the dispersion of particles, a different-direction twin-screw extruder is preferable to a same-direction twin-screw extruder.

<Production method of polyester film>
Hereinafter, although the manufacturing method of the polyester film of this invention is demonstrated concretely, as long as the structural requirements of this invention are satisfied, this invention is not specifically limited to the following illustrations.

  The polyester film of the present invention is preferably one in which all the layers are stretched in the biaxial direction and heat-set by a co-extrusion method in which all layers are co-melt extruded from the die. As a method for co-melt extrusion, either a feed block type or a multi-manifold type may be used. Then, the manufacturing method of the polyester film of this invention is demonstrated more concretely.

  First, a near-infrared absorber, an ultraviolet absorber, and, if necessary, polyester containing inert particles are supplied to separate melt-extrusion apparatuses, heated to a temperature equal to or higher than the melting point of the polymer, and melted. Next, the molten polymer is joined in a laminar flow in an extrusion die and extruded from a slit die. And it cools and solidifies so that it may become the temperature below a glass transition temperature on a rotary cooling drum, and the non-oriented sheet of a substantially amorphous state is obtained. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is employed. Even in the melt extrusion process, the amount of terminal carboxyl groups increases depending on the conditions. Therefore, in the present invention, the residence time of the polyester in the extruder in the extrusion process is shortened. When using a twin screw extruder, provide a vent port and maintain a reduced pressure of 40 hectopascals or less, preferably 30 hectopascals or less, more preferably 20 hectopascals or less. The method of doing etc. is adopted.

  The sheet obtained by such a method is preferably stretched in a biaxial direction to form a film. Specifically describing the stretching conditions, the unstretched sheet is stretched 2 to 6 times in the longitudinal direction at 70 to 145 ° C. to form a longitudinally uniaxially stretched film, and then a hard coat layer or an adhesive layer is formed on at least one side of the film. Apply a coating solution for forming a film, etc., and perform moderate drying or undried, stretch 2-6 times at 90-160 ° C. in the transverse direction, and heat-treat at 150-250 ° C. for 1-600 seconds. It is preferable to carry out. At this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Moreover, it is also possible to add re-longitudinal stretching and / or re-lateral stretching as needed.

  The total thickness T [μm] of the polyester film is usually 20 μm to 250 μm. By setting the total thickness of the film to 20 μm or more, sufficient near infrared and ultraviolet absorption ability can be provided. By setting the total thickness of the film to 250 μm or less, it is possible to satisfy the demand for weight reduction that has been demanded in recent years.

  The polyester film of the present invention can be expanded in application by providing a coating layer such as a hard coat layer or an adhesive layer on the film. In general, since a polyester film is inactive, it is poor in easy adhesion, antistatic properties and releasability, and it is preferable to provide a coating layer in advance for improving the function. You may form an application layer in the single side | surface of a polyester film, or both surfaces as needed. When formed only on one side, other characteristics can be imparted by forming a coating layer different from the above-mentioned coating layer on the opposite surface as necessary. In addition, in order to improve the coating property and adhesiveness of the coating agent to the film, the film may be subjected to chemical treatment or electric discharge treatment before coating, and furthermore, to improve the surface characteristics, the electric discharge treatment is performed after forming the coating layer. You may give it.

  As a method for forming the coating layer, a so-called in-line coating method in which coating is performed before the tenter entrance (before completion of orientation crystallization) and drying in the tenter is preferable. At this time, the application may be performed on one side or both sides.

<Near-infrared absorber>
Near-infrared absorbers used in the present invention include inorganic tungsten cesium oxide, lanthanum hexaboride, copper compounds, tungsten compounds, indium tin oxide, antimony tin oxide, coloring properties and infrared absorption ability, and suppression of bleed-out. Preference is given to ytterbium phosphate and mixtures thereof, nickel complex compounds, antimony trioxide, etc., but also organic phthalocyanine compounds, naphthalocyanine compounds, indoaniline compounds, benzopyran compounds, quinoline compounds, anthraquinone compounds, etc. are also adopted. May be. The type of near-infrared absorber is not particularly limited, and may be used alone or in combination of two or more in some cases.
Since the transition metal element has a large amount of free electrons and the absorption energy of electron transition is in the vicinity of the near infrared, a near infrared absorber having a transition metal element is desirable.

  As for the content of the near infrared absorber in the polyester film, the product X of the film thickness T [μm] and the near infrared absorber amount A [wt%] in the film is preferably 10 or more and 200 or less, more preferably 15 Above, it is 150 or less. By setting X to 10 or more, a sufficient near infrared absorption function can be provided. By setting X to 200 or less, coloring of the film can be suppressed and a film with good visibility can be obtained.

<Ultraviolet absorber>
Since the ultraviolet absorber used in the present invention is incorporated into the polyester chain by transesterification of the polyester in the extruder at the time of film molding from the viewpoint of suppressing bleed out from the outermost layer of the polyester film, the reactive functional group From the viewpoint of moldability such as kneading and extrusion, it is preferable to have 1 to 2 reactive functional groups in one molecule. As typical reactive functional groups, amine groups, hydroxyl groups, thiol groups, hydroxyalkyl groups, and the like can be considered. From the viewpoints of workability and environment, hydroxyalkyl groups are desirable. The type of reactive functional group and the type of ultraviolet absorber are not particularly limited, and may be used alone or in combination of two or more in some cases.

  As the basic skeleton, for example, as an organic ultraviolet absorber, benzoxazine, triazine, benzotriazole, cyanoacrylate, benzophenone, salicylate, paraaminobenzoate, cyclic iminoester, cinnamic acid Various types of inorganic ultraviolet grades such as ultraviolet absorbers, such as titanium oxide, zinc oxide, and fine iron oxide can be used. In addition, a light stabilizer (HALS) such as a hindered amine type can also be employed as a radical scavenger in combination with an ultraviolet absorber.

Among them, as a representative type of reactive ultraviolet absorber, for example, 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (2- Hydroxyethyl) phenol] CAS 196516-61-7 can be used.

  As for the content of the UV absorber in the polyester film, the product Y of the film thickness T [μm] and the UV absorber amount B [wt%] in the film is preferably 100 or more and 1000 or less, more preferably 150 or more, 750 or less. By setting Y to 100 or more, the ability as an ultraviolet absorber can be satisfied. By setting Y to 1000 or less, the problem of difficulty in forming a polyester film due to a decrease in the molecular weight of the polyester can be avoided.

<Fine particles>
It is desirable that the polyester film of the present invention contains fine particles in order to improve workability in the film winding process, coating process, vapor deposition process, and the like. The fine particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, lithium phosphate, magnesium phosphate, calcium phosphate, lithium fluoride, aluminum oxide, and kaolin, and organic particles such as acrylic resin and guanamine resin. Examples thereof include, but are not limited to, precipitated particles obtained by forming catalyst residues into particles. Among these particles, porous silica particles that are aggregate particles of temporary particles are particularly preferable. Since the porous silica particles are less likely to generate voids around the film when the film is stretched, the porous silica particles have the feature of improving the transparency of the film.

  The average particle size of the primary particles constituting the porous silica particles is preferably in the range of 0.001 μm to 0.1 μm. If the average particle size of the primary particles is less than 0.001 μm, ultrafine particles are generated by pulverization in the slurry stage, which may cause agglomerates and increase in foreign matters. When the average particle diameter exceeds 0.1 μm, the porosity of the particles is lost, and as a result, there is a possibility that the feature with less generation of voids may be lost.

  Furthermore, the pore volume of the aggregated particles is in the range of 0.5 ml / g to 2.0 ml / g, preferably 0.6 ml / g to 1.8 ml / g. When the pore volume is less than 0.5 ml / g, the porosity of the particles is lost, voids are easily generated, and the transparency of the film tends to be lowered. When the pore volume is larger than 2.0 ml / g, crushing and aggregation are likely to occur, and it may be difficult to adjust the particle size.

  The method for adding particles to the polyester film is not particularly limited, and a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction. The condensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water and a polyester raw material using a kneading extruder with a vent, or a blend of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, heat stabilizers, lubricants, antistatic agents, dyes, and the like can be added to the polyester film of the present invention as necessary.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded. In addition, the measurement and evaluation method of various physical properties of a film are shown below.

<Intrinsic viscosity (dl / g)>
When a polyester chip is sampled, it is pulverized, and when a polyester film is sampled, a necessary amount is appropriately cut with a cutter or scissors. The obtained sample is precisely weighed and added to phenol / tetrachloroethane = 50/50 (weight ratio) to 1.0 g / dl. After dissolving at 120 ° C. for 10 minutes, the mixture was gradually cooled to room temperature. Using a capillary viscometer, the flow time of the solution and the flow time of the solvent alone were measured, and the intrinsic viscosity was calculated from the time ratio using the Huggins equation. At that time, the Huggins constant was assumed to be 0.33.

<Sunlight shielding coefficient>
Of the incident solar heat, the amount of heat flowing into the room through a float plate glass (transparent) with a thickness of 1.5 mm is 1, and the amount of heat flowing into the room when 20 films (75 μm) are stacked is shown. The thing was evaluated as a solar radiation shielding coefficient (Kyoto Electronics Industry Co., Ltd. heat flow meter HFM-201). A smaller solar shading coefficient indicates more heat shielding.

<Transmission density (OD)>
A single film was measured, the transmission density (OD) under the G filter was measured, and it was used as an index of colorability (concealment degree). After the displayed value was stabilized, reading was performed (Macbeth densitometer TD-904 type). . The smaller the transmission density (OD), the lower the colorability (concealment degree).

<Spectral light transmittance (%)>
With a spectrophotometer (UV3100PC manufactured by Shimadzu Corporation), the light transmittance was continuously measured with respect to the polyester film using a halogen lamp light source at a low scanning speed, a sampling pitch of 1 nm, and a light wavelength of 300 to 800 nm. From the measurement results, the light transmittance (Tuv) at a light wavelength of 380 nm was read and evaluated according to the following criteria.
○: Tuv ≦ 40%
×: Tuv> 40%

<Bleed resistance>
The polyester film was treated in a high-temperature environment of 150 ° C. × 60 min, and the haze difference before and after the treatment (ΔHz, N = 3 average calculation with NDH-2000, Nippon Denshoku Industries Co., Ltd.) Was measured and evaluated according to the following criteria.
○: ΔHz ≦ + 2.0%
×: ΔHz> + 2.0%

<Film forming properties>
When the amorphous sheet was longitudinally stretched after being longitudinally stretched, the following criteria evaluated the situation in which the film breaks during stretching in a lateral stretching machine (tenter).
○: When the film does not break during stretching and the productivity is good ×: When the film breaks occasionally or always, and the productivity is inferior or not at all

<X, Y>
In Tables 1 and 2 below, X is the product of the near-infrared absorber content A [wt%] in the polyester film and the thickness T [μm] of the polyester film (= T [μm] × A [wt%]). Y represents the product (= T [μm] × B [wt%]) of the ultraviolet absorber content B [wt%] in the polyester film and the film thickness T [μm].
As described above, in the present invention, the content of the near-infrared absorber and the content of the ultraviolet absorber are respectively defined in the following ranges.
200 ≧ X (= T [μm] × A [wt%]) ≧ 10
1000 ≧ Y (= T [μm] × B [wt%]) ≧ 100

Next, the polyester raw material used in the following examples will be described.
<Method for producing polyester (a)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.02 part of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the reaction is gradually carried out as methanol is distilled off. The temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.03 part of ethyl acid phosphate to this reaction mixture, it moved to the polycondensation tank, added 0.04 part of antimony trioxide, and performed polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 dl / g due to a change in the stirring power of the reaction tank, the polymer was discharged under nitrogen pressure, extracted into a strand, cooled with water, and then cut with a cutter. Polyester resin pellets (prepolymer). Using the polyester resin pellets (prepolymer) as a starting material, solid phase polymerization was performed at 220 ° C. under vacuum to obtain pellets of polyester (a). The intrinsic viscosity of the obtained polyester was 0.85 dl / g.

<Method for producing polyester (b)>
In the production of a prepolymer of polyester (a) (intrinsic viscosity 0.66 dl / g), polyester (a) except that after completion of transesterification, 3.5 parts by weight of silica particles having an average particle size of 4.10 μm are blended. A polyester (b) was obtained in the same manner as in the prepolymer. The viscosity of the obtained polyester was 0.66.

<Method for producing polyester (c)>
Starting from 100 parts by weight of dimethyl terephthalate, 54 parts by weight of ethylene glycol, and 25 parts by weight of 1,4-cyclohexanedimethanol, 0.0110 ppm by weight of tetrabutyl titanate and 81 ppm by weight of phosphoric acid as a catalyst were taken in the reactor. The reaction start temperature was 150 ° C., and the reaction temperature was gradually increased as methanol was distilled off. After 1 hour, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 dl / g due to a change in the stirring power of the reaction tank, the polymer was discharged under nitrogen pressure, extracted into a strand, cooled with water, and then cut with a cutter. Thus, polyester (c) in a pellet state was produced. The intrinsic viscosity of the obtained polyester was 0.6 dl / g3.

<Ultraviolet absorber (d)>
A reactive ultraviolet absorber (d) manufactured by Daiwa Kasei Co., Ltd., which has DAINSORB T-33 (2,2′-methylenebis [6- (2H-benzotriazole-2-) having the following structure (Chemical Formula 2) Yl) -4- (2-hydroxyethyl) phenol]).

<Ultraviolet absorber (e)>
Non-reactive ultraviolet absorber (e) manufactured by Chemipro Kasei Co., Ltd., which has 2,2′-p-phenylenebis (4H-3,1-benzoxazin-4-one) having the following structure (Chemical Formula 3) )It was used.

<Production method of near-infrared absorber master batch (MB) (f)>
10% by weight of KHDS-06 (containing LaB6 (lanthanum hexaboride)) and 90% by weight of polyester (a), which are near-infrared absorbers manufactured by Sumitomo Metal Mining Co., Ltd., are kneaded and extruded using a twin-screw kneader. A master batch (f) was obtained.

Example 1:
A mixed raw material in which the polyesters (a), (b) and the ultraviolet absorber (d) described above were mixed at a ratio of 81.8%, 16.0%, and 2.2%, respectively, was used as the raw material for the (A) layer (sub-extrusion) Machine), and mixed raw materials in which polyester (c), ultraviolet absorber (d), and near infrared absorber MB (f) are mixed in proportions of 95.8%, 2.2%, and 2.0%, respectively (B ) As the raw material of the layer (main extruder), each is supplied to two vent type twin screw extruders and melted at 285 ° C., respectively, (A) layer is the outermost layer (surface layer), (B) layer is the middle Coextruded in a layer configuration of two types and three layers (A / B / A) to form a layer, extruded from a die, cooled and solidified on a cooling roll set at a surface temperature of 40 ° C. using an electrostatic application adhesion method, and unstretched A sheet was obtained. Next, the film was stretched 3.0 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.1 times at 120 ° C. in the transverse direction, and heat-treated at 225 ° C. Thereafter, it was relaxed by 2% in the transverse direction, and a laminated polyester film having a thickness of 75 μm and a thickness of each layer of 2.6 / 69.8 / 2.6 μm was obtained. The evaluation results are shown in Table 1.

Comparative Examples 1-2:
A biaxially stretched polyester film was obtained in the same manner as in Example 1 with respect to the raw material blending ratio and film thickness shown in Table 2 below. The evaluation results are also shown in Table 2.
Comparative Example 1 is an example in which the blending amount of the near-infrared absorber and the film thickness of the film are adjusted so that X (= T [μm] × A [wt%]) is less than 10. In Comparative Example 1, the solar radiation shielding coefficient was increased, and a sufficient near infrared absorption function could not be obtained.
Comparative Example 2 is an example in which the blending amount of the near-infrared absorber and the film thickness of the film are adjusted so that X (= T [μm] × A [wt%]) exceeds 200. In Comparative Example 2, it was confirmed that the transmission density was increased, the color of the film was large, and the visibility was inferior.

Comparative Example 3:
A biaxially stretched polyester film was obtained in the same manner as in Example 1 with respect to the raw material blending ratio and film thickness shown in Table 2 below. The evaluation results are also shown in Table 2.
Comparative Example 3 is a prescription in which a large amount of the reactive ultraviolet absorber (d) is blended. In the melt extrusion process, it also acts as a catalyst for the dissociation of the PET molecular chain, so that film formation is difficult due to extreme IV drop. It became.

Comparative Example 4:
A biaxially stretched polyester film was obtained in the same manner as in Example 1 with respect to the raw material blending ratio and film thickness shown in Table 2 below. The evaluation results are also shown in Table 2.
Comparative Example 4 was a formulation in which the reactive ultraviolet absorber (d) was blended in a small amount, and the light transmittance cut in the ultraviolet region was insufficient.

Comparative Examples 5-6:
A biaxially stretched polyester film was obtained in the same manner as in Example 1 with respect to the raw material blending ratio and film thickness shown in Table 2 below. The evaluation results are also shown in Table 2.
Comparative Examples Comparative Examples 5 to 6 are formulations in which the non-reactive ultraviolet absorber (e) is blended, and when the ultraviolet absorber is blended in the (A) layer and the (B) layer, only in the (B) layer. Regardless of the case where the ultraviolet absorber was blended, sufficient bleeding resistance could not be obtained.

  The polyester film of the present invention has a near-infrared absorbing function and an ultraviolet absorbing function, and even when used in an environment exposed to sunlight, it can avoid bleeding out of the ultraviolet absorber, It can be suitably used for windows for houses, windows for vehicles such as trains and cars, arcades, greenhouses, etc., for infrared remote control malfunction prevention in plasma displays, for protection of solar panels, sunglasses, and general glasses , Protective glasses, contact lenses and the like.

Claims (4)

A polyester film containing a near-infrared absorber and an ultraviolet absorber having a reactive functional group,
The content A [wt%] of the near infrared absorber in the polyester film and the thickness T [μm] of the polyester film satisfy the following formula (1), and the content of the ultraviolet absorber in the polyester film A polyester film in which B [% by weight] and film thickness T [μm] satisfy the following formula (2).
200 ≧ T [μm] × A [wt%] ≧ 10 (1)
1000 ≧ T [μm] × B [weight%] ≧ 100 (2)   The polyester film according to claim 1, wherein the ultraviolet absorber has 1 to 2 reactive functional groups in one molecule.   The polyester film according to claim 1 or 2, wherein the reactive functional group is at least one selected from the group consisting of an amine group, a hydroxyl group, a thiol group, and a hydroxyalkyl group.   The polyester film according to claim 1, wherein the near-infrared absorber is a near-infrared absorber having a transition metal element.