JP6972524B2 - Polyester film - Google Patents

Description

The present invention relates to a polyester film having a near-infrared absorbing function and an ultraviolet absorbing 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 is disclosed (Patent Documents 1, 2, etc.).

It is known that the near-infrared absorbing dye contained in this near-infrared absorbing layer is generally decomposed by ultraviolet rays contained in the sun's rays, and its performance is deteriorated by long-term use. In particular, the aromatic diimmonium salt compound generally used as a near-infrared absorbing dye is liable to be altered by ultraviolet rays.

Regarding this point, in Patent Document 1, a plastic film base material is laminated on both sides of a near-infrared absorbing dye-containing layer, and an ultraviolet absorbing layer is laminated on one of the plastic film base materials to avoid deterioration due to ultraviolet rays. The technology is disclosed. Further, Patent Document 2 discloses a technique of incorporating an ultraviolet absorber into an intermediate layer of a base material having a three-layer structure of "outermost layer / intermediate layer / outermost layer".

It is known that when the ultraviolet absorber is a small molecule type, bleed-out of the ultraviolet absorber is likely to occur. Bleed-out of the ultraviolet absorber is not preferable because it causes deterioration of the quality of the film and deterioration of the adhesion with the functional layer laminated on the film.
In this regard, in Patent Document 2, an ultraviolet absorber is contained in an intermediate layer of a base material having a three-layer structure of "outermost layer / intermediate layer / outermost layer", and an ultraviolet absorber is substantially contained in both outermost layers. A technique is disclosed in which the bleed-out of an ultraviolet absorber is dramatically reduced even when a small molecule type ultraviolet absorber is used by adopting a structure that does not contain the ultraviolet absorber.

However, in the technique of Patent Document 2, as described above, both outermost layers of the base material having the three-layer structure of "outermost layer / intermediate layer / outermost layer" are configured so that the ultraviolet absorber is not substantially contained. Therefore, when used in an environment exposed to the sun's rays, deterioration is likely to proceed in the surface layer most exposed to the sun's rays, and when the surface layer deteriorates, the intermediate layer is directly exposed to ultraviolet rays, thus suppressing bleed-out. There was a problem that the effect could not be expected sufficiently.

Japanese Unexamined Patent Publication No. 2002-301785 Japanese Unexamined Patent Publication No. 2006-21935

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, bleed-out of an ultraviolet absorber can be achieved. It is to provide a film that can be avoided.

As a result of diligent studies to solve the above-mentioned problems, it was found that the above-mentioned problems can be solved by using a polyester film having a specific composition, and the following invention was completed.
The present invention provides the following [1] to [4].
[1] A polyester film containing a near-infrared absorber and an ultraviolet absorber having a reactive functional group, wherein the content A [% by weight] of the near-infrared absorber in the polyester film and the thickness T of the polyester film. A polyester film in which [μm] satisfies the following formula (1), and the content B [% by weight] of the ultraviolet absorber in the polyester film and the film thickness T [μm] satisfy the following formula (2). ..
200 ≧ T [μm] × A [weight%] ≧ 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, bleed-out of the ultraviolet absorber can be avoided even when the ultraviolet absorber is present on the outermost layer of the polyester film. Completed. According to the present invention, even when the ultraviolet absorber is present on the outermost layer of the polyester film, bleed-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 is also present in the outermost layer of the polyester film, even when the outermost layer of the polyester film is used in an environment exposed to sunlight, the sun's rays. The ultraviolet rays contained in the above are absorbed by the ultraviolet absorber, and deterioration of the near-infrared absorbing dye can be avoided.
Further, in the present invention, since the near-infrared absorber and the ultraviolet absorber are contained in the polyester film itself, as in the conventional case, a near-infrared absorbing dye-containing layer is laminated on the base material, or the base material is used. It is possible to provide a film having a near-infrared absorbing function and an ultraviolet absorbing function without going through a step of laminating an ultraviolet absorbing layer.

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

<Polyester film>
In the present invention, the polyester film means a film that is melt-extruded from an extrusion base, that is, a molten polyester sheet extruded by a so-called extrusion method is cooled and then stretched. Alternatively, it means a product extruded by a co-extrusion method in which all layers are co-melt-extruded from a base, stretched, and then heat-fixed as necessary.

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

The polymer constituting each layer of the three-layer structure polyester film is mainly composed of polyester obtained by using aromatic dicarboxylic acid or an ester thereof and glycol as a main starting material, and 60% or more of the repeating structural units are ethylene. Refers to a polyester having a terephthalate unit or an ethylene-2,6-naphthalate unit. Then, other third components may be contained as long as the conditions do not deviate from the above range. Examples of aromatic dicarboxylic acid components include isophthalic acid, phthalic acid, adipic acid, sebacic acid, and oxycarboxylic acid (eg, p-oxyethoxy) in addition to terephthalic acid, dimethyl terephthalate, and 2,6-naphthalenedicarboxylic acid. Benzoic acid, etc.) can be used. In particular, it is preferable to use terephthalic acid or dimethyl terephthalate. As an example of the glycol component, one or more of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like can be used in addition to ethylene glycol. In particular, it is preferable to use ethylene glycol.

The ultimate viscosity of polyester is 0.64 dl / g or more, preferably 0.66 dl / g or more. When the ultimate viscosity of the polyester is 0.64 dl / g or more, a polyester film having good long-term durability and hydrolysis resistance can be obtained after the wet heat treatment. On the other hand, although there is no upper limit to the ultimate viscosity of 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 step. The method for measuring the ultimate viscosity of polyester is as described in Examples.

In the present invention, the polyester can contain inert particles or the like within a range that does not deviate from the object of the present invention, and the method thereof is not particularly limited. A method of using a master batch or the like can be adopted. A particularly preferred method is a method in which particles are directly added and mixed in an extrusion process during a film manufacturing process. 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 biaxial extruder in a different direction is preferable to a twin extruder in the same direction.

<Manufacturing method of polyester film>
Hereinafter, the method for producing a polyester film of the present invention will be specifically described, but the present invention is not particularly limited to the following examples as long as the constituent requirements of the present invention are satisfied.

The polyester film of the present invention is preferably one in which all layers are co-extruded from a base by a co-extrusion method, and the extruded film is stretched in the biaxial direction and heat-fixed. As a method of co-melt extrusion, either a feed block type or a multi-manifold type may be used. Therefore, the method for producing the polyester film of the present invention will be described in more detail.

First, a polyester containing a near-infrared absorber, an ultraviolet absorber, and, if necessary, inert particles are supplied to different melt extruders, and heated to a temperature equal to or higher than the melting point of the polymer to melt. Then, the molten polymer is joined in a laminar flow in the extrusion base and extruded from the slit-shaped die. Then, it is rapidly cooled and solidified on the rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature to obtain an unaligned sheet in a substantially amorphous state. 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, and in the present invention, the electrostatic application adhesion method and / or the liquid coating adhesion method is adopted. 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 polyester in the extruder in the extrusion process is shortened. If a twin-screw extruder is used, a vent port is provided to sufficiently dry the extruder so that the pressure is 50 ppm or less, preferably 30 ppm or less, and a reduced pressure of 40 hectopascals or less, preferably 30 hectopascals or less, more preferably 20 hectopascals or less is maintained. Adopt a method such as

It is preferable to stretch the sheet obtained by such a method in the biaxial direction to form a film. Specifically, the stretching conditions are described. The unstretched sheet is stretched 2 to 6 times in the vertical direction at 70 to 145 ° C. to form a vertically uniaxially stretched film, and then a hard coat layer or an adhesive layer is formed on at least one surface of the film. Apply a coating liquid to form such as, and dry it appropriately, or stretch it laterally at 90 to 160 ° C for 2 to 6 times and heat treat it at 150 to 250 ° C for 1 to 600 seconds. It is preferable to do. At this time, a method of relaxing by 0.1 to 20% in the vertical direction and / or the horizontal direction in the maximum temperature zone of the heat treatment and / or the cooling zone of the heat treatment outlet is preferable. It is also possible to add re-longitudinal stretching and / or re-transverse 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 meet the demand for weight reduction, which has been strongly demanded in recent years.

The polyester film of the present invention can be widely used by providing a coating layer such as a hard coat layer or an adhesive layer on the film. Since the polyester film is generally inert, it lacks easy adhesiveness, antistatic property, and mold releasability, and it is preferable to provide a coating layer in advance in order to improve the function. The coating layer may be formed on one side of the polyester film or, if necessary, on both sides. When it is formed on only one side, a coating layer different from the above-mentioned coating layer may be formed on the opposite surface, if necessary, to impart other characteristics. In addition, in order to improve the coatability and adhesiveness of the coating agent to the film, the film may be chemically treated or discharged before coating, and further, in order to improve the surface characteristics, the discharge treatment is performed after the coating layer is formed. You may give it.

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

<Near infrared absorber>
The near-infrared absorber used in the present invention is an inorganic tungsten cesium oxide, hexaborohydride, copper compound, tungsten compound, indium tin oxide, antimony trioxide, because of its coloring property, infrared absorption ability, and bleed-out suppression. Itterbium phosphate and mixtures thereof, nickel complex compounds, antimony trioxide, etc. are preferable, but other organic phthalocyanine compounds, naphthalocyanine compounds, indiananiline compounds, benzopyran compounds, quinoline compounds, anthraquinone compounds, etc. are also adopted. May be. The type of the near-infrared absorber is not particularly limited, and may be used alone or in combination of two or more.
Since the transition metal element has a large amount of free electrons and the absorption energy of the electron transition is near the near infrared ray, a near infrared ray absorber having the transition metal element is desirable.

Regarding the content of the near-infrared absorber in the polyester film, the product X of the film thickness T [μm] and the amount of the near-infrared absorber A [% by weight] in the film X is preferably 10 or more and 200 or less, more preferably 15. The above 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 having good visibility can be obtained.

<UV absorber>
The ultraviolet absorber used in the present invention is incorporated into the polyester chain by transesterification of the polyester in the extruder during film molding from the viewpoint of suppressing bleeding out from the outermost layer of the polyester film, and thus is a reactive functional group. It is important to have 1 or 2 reactive functional groups in one molecule from the viewpoint of moldability such as kneading and extrusion. As a typical reactive functional group, an amine group, a hydroxyl group, a thiol group, a hydroxyalkyl group and the like can be considered, but a hydroxyalkyl group is preferable from the viewpoint of workability and the environment. The type of the reactive functional group and the type of the ultraviolet absorber are not particularly limited, and may be used alone or in combination of two or more.

As the basic skeleton, for example, as an organic ultraviolet absorber, benzoxazine type, triazine type, benzotriazole type, cyanoacrylate type, benzophenone type, salicylate ester type, paraaminobenzoic acid type, cyclic iminoester type, silicic acid type. As an inorganic ultraviolet class agent such as an ultraviolet absorber, various types such as titanium oxide, zinc oxide, and fine particle iron oxide can be adopted. Further, a light stabilizer (HALS) such as a hindered amine type can also be adopted as a radical catching agent in combination with an ultraviolet absorber.

Among them, typical types of reactive UV absorbers include, for example, 2,2'-methylenebis [6- (2H-benzotriazole-2-yl) -4- (2-yl) having the following structure (Chemical formula 1). Hydroxyethyl) Phenol] CAS 196516-61-7 can be used.

Regarding 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 [% by weight] in the film is preferably 100 or more, 1000 or less, more preferably 150 or more. It is 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, it is possible to avoid the problem that the film formation of the polyester film becomes difficult due to the decrease in the molecular weight of the polyester.

<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 step, coating step, vapor deposition step 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. And the precipitated particles obtained by granulating the catalyst residue can be mentioned, but the present invention is not limited thereto. Among these particles, porous silica particles, which are aggregate particles of temporary particles, are particularly preferable. Porous silica particles have a feature of improving the transparency of the film because voids are less likely to be generated around the particles when the film is stretched.

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 crushing at the slurry stage, which may form aggregates and cause an increase in foreign matter, while the primary particles of the primary particles have an average particle size of less than 0.001 μm. If the average particle size exceeds 0.1 μm, the porosity of the particles may be lost, and as a result, the feature of less void generation may be lost.

Further, 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. If the pore volume is less than 0.5 ml / g, the porosity of the particles is lost, voids are likely to occur, and the transparency of the film tends to decrease. If 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 of adding the 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 in which polyester is produced, but is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or at the stage after the completion of the transesterification reaction and before the start of the polycondensation reaction. The condensation reaction may proceed. Further, a method of blending a slurry of particles dispersed in ethylene glycol or water with a polyester raw material using a kneaded extruder with a vent, or a method of blending dried particles with a polyester raw material using a kneading extruder. It is done by the method.

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, if necessary.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples as long as the gist of the present invention is not exceeded. The methods for measuring and evaluating various physical properties of the film are shown below.

<Ultimate viscosity (dl / g)>
When sampling polyester chips, crush them, and when sampling polyester films, cut the required amount in advance with a cutter or scissors. The obtained sample is finely weighed and added to phenol / tetrachloroethane = 50/50 (weight ratio) so as to be 1.0 g / dl. After dissolving at 120 ° C. for 10 minutes, the mixture was gradually cooled to room temperature. The flow time of the solution and the flow time of the solvent alone were measured using a capillary viscometer, and the ultimate viscosity was calculated from these time ratios using the Huggins formula. At that time, the Huggins constant was assumed to be 0.33.

<Insolation shielding coefficient>
Of the incident solar heat, the amount of heat that flows into the room through the float plate glass (transparent) with a thickness of 1.5 mm is set to 1, and the amount of heat that flows into the room when 20 films (75 μm) are stacked is shown. It was evaluated as a solar radiation shielding coefficient (Kyoto Denshi Kogyo Co., Ltd. heat flow meter HFM-201). The smaller the solar radiation shielding coefficient, the more heat is shielded.

<Permeation concentration (OD)>
The film was measured as a single sheet, the transmission density (OD) under the G filter was measured, used as an index of colorability (concealment degree), and read after the displayed value became stable (Macbeth densitometer TD-904 type). .. The smaller the transmission concentration (OD), the lower the coloring property (concealment degree).

<Spectroscopic light transmittance (%)>
A spectrophotometer (UV3100PC manufactured by Shimadzu Corporation) was used to continuously measure the light transmittance of a polyester film in a low scanning speed, a sampling pitch of 1 nm, and a light wavelength region of 300 to 800 nm using a halogen lamp light source. From the measurement result, 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 is treated in a high temperature environment of 150 ° C. × 60 min, and the haze difference before and after the treatment (ΔHz, average calculation of N = 3 measurement with Haze Meter NDH-2000 manufactured by Nippon Denshoku Kogyo Co., Ltd.) Was measured and evaluated according to the following criteria.
◯: ΔHz ≤ + 2.0%
×: ΔHz> + 2.0%

<Film film forming property>
When the amorphous sheet was longitudinally stretched and then laterally stretched, the situation in which the film was broken during stretching was evaluated by the following criteria in a transverse stretching machine (tenter).
◯: When the film does not break during stretching and the productivity is good ×: When the film breaks occasionally or constantly and the productivity is inferior or not at all

<X, Y>
In Tables 1 and 2 below, X is the product of the content A [% by weight] of the near-infrared absorber in the polyester film and the thickness T [μm] of the polyester film (= T [μm] × A [% by weight]. ), And Y means the product (= T [μm] × B [% by weight]) of the content B [% by weight] of the ultraviolet absorber 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 defined in the following ranges, respectively.
200 ≧ X (= T [μm] × A [weight%]) ≧ 10
1000 ≧ Y (= T [μm] × B [weight%]) ≧ 100

Next, the polyester raw material used in the following example will be described.
<Manufacturing method of 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 was taken in a reactor as a catalyst, the reaction start temperature was set to 150 ° C., and the reaction was gradually carried out with the distillation of methanol. The temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After 0.03 part of ethyl acid phosphate was added to this reaction mixture, the mixture was transferred to a polycondensation tank, 0.04 part of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually increased from 230 ° C to 280 ° C. On the other hand, the pressure was gradually reduced from the normal pressure to finally reach 0.3 mmHg. After the reaction was started, the reaction was stopped at the point corresponding to the ultimate viscosity of 0.63 dl / g due to the change in the stirring power of the reaction tank, the polymer under nitrogen pressure was discharged, extracted into strands, cooled with water, and then cut with a cutter. To produce polyester resin pellets (prepolymer). Using the polyester resin pellet (prepolymer) as a starting material, solid-phase polymerization was carried out at 220 ° C. under vacuum to obtain a polyester (a) in a pellet state. The ultimate viscosity of the obtained polyester was 0.85 dl / g.

<Manufacturing method of polyester (b)>
In the production of the polyester (a) prepolymer (extreme viscosity 0.66 dl / g), the polyester (a) except that 3.5 parts by weight of silica particles having an average particle size of 4.10 μm are added after the transesterification is completed. Polyester (b) was obtained in the same manner as the prepolymer of. The viscosity of the obtained polyester was 0.66.

<Manufacturing method of polyester (c)>
Using 100 parts by weight of dimethyl terephthalate, 54 parts by weight of ethylene glycol and 25 parts by weight of 1,4-cyclohexanedimethanol as starting materials, 0.0110% by weight ppm of tetrabutyl titanate and 81 parts by weight of phosphoric acid were used as catalysts in a reactor. The reaction start temperature was set to 150 ° C., and the reaction temperature was gradually increased with the distillation of methanol to 230 ° C. after 3 hours. After 1 hour, the temperature was gradually increased from 230 ° C to 280 ° C. On the other hand, the pressure was gradually reduced from the normal pressure to finally reach 0.3 mmHg. After the reaction was started, the reaction was stopped at the point corresponding to the ultimate viscosity of 0.63 dl / g due to the change in the stirring power of the reaction tank, the polymer under nitrogen pressure was discharged, extracted into strands, cooled with water, and then cut with a cutter. Then, the polyester (c) in a pellet state was produced. The ultimate viscosity of the obtained polyester was 0.6 dl / g 3.

<Ultraviolet absorber (d)>
DAINSORB T-33 (2,2'-methylenebis [6- (2H-benzotriazole-2-), which is a reactive ultraviolet absorber (d) manufactured by Daiwa Kasei Co., Ltd. and has the following structure (Chemical formula 2). Il) -4- (2-hydroxyethyl) phenol]) was used.

<Ultraviolet absorber (e)>
2,2'-p-phenylenebis (4H-3,1-benzoxazine-4-one), which is a non-reactive ultraviolet absorber (e) manufactured by Chemipro Kasei Co., Ltd. and has the following structure (chemical 3). )It was used.

<Manufacturing method of near-infrared absorber masterbatch (MB) (f)>
KHDS-06 (containing LaB6 (6 lanthanum hexaboride)) 10% by weight and polyester (a) 90% by weight, which are near-infrared absorbers manufactured by Sumitomo Metal Mining Co., Ltd., are kneaded and extruded by a twin-screw kneader to make polyester. A masterbatch (f) was obtained.

Example 1:
A mixed raw material (sub-extruded) in which the above-mentioned polyesters (a) and (b) and the ultraviolet absorber (d) are mixed at a ratio of 81.8%, 16.0% and 2.2%, respectively, is used as a raw material for the layer (A). A mixed raw material in which polyester (c), ultraviolet absorber (d), and near-infrared absorber MB (f) were mixed at a ratio of 95.8%, 2.2%, and 2.0%, respectively, was used as (B). ) As the raw material (main extruder) of the layer, each is supplied to two vent type twin-screw extruders, each of which is melted at 285 ° C., the layer (A) is the outermost layer (surface layer), and the layer (B) is in the middle. It is co-extruded with a layer structure of 2 types and 3 layers (A / B / A) as layers, extruded from the base, cooled and solidified on a cooling roll whose surface temperature is set to 40 ° C. using the electrostatic application adhesion method, and unstretched. I got a sheet. Then, using the difference in roll peripheral speed, the film was stretched 3.0 times in the vertical direction at a film temperature of 85 ° C., guided to a tenter, stretched 4.1 times at 120 ° C. in the horizontal direction, and heat-treated at 225 ° C. After that, it was relaxed by 2% in the lateral direction to obtain a laminated polyester film having a thickness of 75 μm and a thickness of each layer of 2.6 / 69.8 / 2.6 μm. 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 compounding ratio and the 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 [% by weight]) is less than 10. In Comparative Example 1, the solar shading coefficient became large, 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 [% by weight]) exceeds 200. In Comparative Example 2, it was confirmed that the transmission density was high, the coloration of the film was large, and the visibility was poor.

Comparative Example 3:
A biaxially stretched polyester film was obtained in the same manner as in Example 1 with respect to the raw material compounding ratio and the film thickness shown in Table 2 below. The evaluation results are also shown in Table 2.
Comparative Example 3 is a formulation containing a large amount of the reactive ultraviolet absorber (d) and also acts as a catalyst for dissociation of PET molecular chains in the melt extrusion process, so that it is difficult to form a film 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 compounding ratio and the film thickness shown in Table 2 below. The evaluation results are also shown in Table 2.
Comparative Example 4 was a formulation in which a small amount of the reactive ultraviolet absorber (d) was blended, 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 compounding ratio and the 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 containing the non-reactive UV absorber (e), and when the UV absorber is blended in the (A) layer and the (B) layer, only the (B) layer is used. Sufficient bleeding resistance could not be obtained regardless of the case where the ultraviolet absorber was blended.

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

Claims (1)

A polyester film containing a near-infrared absorber and an ultraviolet absorber having a reactive functional group.
The near-infrared absorber is selected from the group consisting of cesium oxide, lanthanum hexaboride, copper compound, tungsten compound, indium tin oxide, antimony oxide tin, ytterbium phosphate and mixtures thereof, nickel complex compounds, and antimony trioxide. Is more than one kind
The content A [% by weight] 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. B [% by weight] and film thickness T [μm] satisfy the following formula (2) .
The ultraviolet absorber is, to have a 1-2 hydroxyalkyl groups per molecule, a polyester film.
200 ≧ T [μm] × A [weight%] ≧ 10 ... (1)
1000 ≧ T [μm] × B [weight%] ≧ 100 ... (2)