WO2019147037A1 - Polyester film for window - Google Patents

Abstract

The present invention relates to a polyester film for a window, the film being capable of: blocking harmful ultraviolet rays from the outside or preventing glare caused by direct sunlight, and reducing thermal energy, when adhered to outer wall glass of a vehicle or a building; resolving a phenomenon in which an image is blurred or an image breaks without being clear, when an external shape is seen through glass; preventing a defect of longitudinal fine roll dragging occurring during a manufacturing process of a polyester film such that an external clear shape can be confirmed even through the polyester film; and facilitating shrinking and release even at a high temperature when a window film is constructed on the glass of a vehicle or a building while being laminated with a release film.

Description

Polyester film for windows

The present invention relates to a polyester film for a window, and more particularly, to a polyester film for a window which can improve an image blurring phenomenon, has excellent optical surface visibility and is easy to operate at the time of construction.

The polyester film for windows, which is generally referred to as a tanning film, is largely divided into automobile and architectural types depending on the use thereof, and is classified into anti-use and non-anti-use depending on the use of the evaporated film.

This window film is used as a base material of a product which has high transparency hard coat to protect the surface of the product by imparting color to the high transparent polyester film, thereby preventing harmful ultraviolet rays, preventing glare caused by direct sunlight, and reducing heat energy .

On the other hand, the market for automotive window film has grown along with customers who are looking for a product that is a little cheaper and high quality under the competitive price and quality of life due to the growth of the automobile market.

To this end, we are now producing and marketing a variety of inline coated polyester films that have improved surface adhesion through functional primer coating on the surface as well as polyester film production beyond the offline processing market, which is already in the secondary processing stage. At the same time, large-sized window makers are actively engaged in activities such as collaboration and cooperation with large companies producing polyester film.

It is necessary to reflect the market trends and to provide customers with a window film that is somewhat optically excellent and easy to operate.

However, there are problems such as phase blur and workability which have been continuously pointed out in the window polyester film market, and it is urgent to provide a uniform polyester film for windows by solving these problems.

SUMMARY OF THE INVENTION The present invention has been accomplished in order to solve the above-mentioned problems and to solve the problems of the prior art, and it is an object of the present invention to provide a method and apparatus for suppressing particle visibility of optically invisible particles, securing basic strength and elongation, It is an object of the present invention to provide a polyester film for a window which is easy to shrink and peel off even at a high temperature when a film is applied to a glass of a vehicle and a building,

These and other objects and advantages of the present invention will become more apparent from the following description of a preferred embodiment thereof.

The object is achieved by a polyester film comprising a three-layer laminated polyester film produced by a sequential biaxial stretching method and a coating layer (A) comprising an aqueous emulsion of an acrylic acid alkyl ester copolymer on at least one side of the three- The three-layer laminated polyester film is composed of an upper layer of a polyester resin layer (C) not containing fine particles and a particle layer (B, D) of a polyester resin containing an amorphous calcium carbonate compound in the lower layer, The thickness ratio of the C layer to the B layer and the D layer is 4 to 40, and the stretching ratio of the three-layer laminated polyester film satisfies the following formula (1)

(Equation 1)

1.1? Y / X? 1.5

, Wherein X is a longitudinal stretching ratio and Y is a transverse stretching ratio.

Here, the thickness ratio of the C layer to the B layer and the D layer is 10 to 20.

Preferably, the three-layer laminated polyester film has a draw ratio of 1.1 to 1.3.

Preferably, the amorphous calcium carbonate compound has an average particle diameter of 0.01 to 1.5 mu m.

Preferably, the amorphous calcium carbonate compound has an average particle diameter of 0.8 to 1.2 탆.

Preferably, the thickness of the coating layer is 5 to 20 nm.

Preferably, the thickness of the polyester film for window is 12 to 36 mu m.

Preferably, the polyester film for a window has a heat shrinkage ratio of 0 or less in the transverse direction among the numerical values of the heat shrinkage measured by being left in a thermostatic chamber at 150 캜 for 30 minutes.

According to the present invention, it is possible to prevent harmful ultraviolet rays from outside or to prevent glare caused by direct sunlight and to reduce thermal energy, when adhering to the outer wall glass of a vehicle or a building.

Further, the present invention can solve the phenomenon that when the external shape is viewed through the glass, the phase is blurred or unclear and the phase is broken.

Further, the present invention is free from the drawbacks of the longitudinal micro-roll dragging that occurs in the production process of the polyester film, so that an externally clear shape can be confirmed through the polyester film, When the window film is applied, it has effects such as easy shrinkage and peeling at a high temperature.

However, the effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a cross-sectional view of a polyester film for a window according to a preferred embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. It will be apparent to those skilled in the art that these embodiments are provided by way of illustration only for the purpose of more particularly illustrating the present invention and that the scope of the present invention is not limited by these embodiments .

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Also, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

In describing and / or claiming the present invention, the term "copolymer" is used to refer to a polymer formed by copolymerization of two or more monomers. Such copolymers include binary copolymers, terpolymers, or higher order copolymers.

Fig. 1 is a cross-sectional view of a polyester film for window according to a preferred embodiment of the present invention, and the polyester film for window according to the present invention is a three-layer laminated polyester film produced by a sequential biaxial stretching method, (B, D) composed of a polyester resin containing an amorphous calcium carbonate compound in an upper layer and a lower layer of a polyester resin layer (C), wherein at least one side of the three-layered polyester film And a coating layer (A) comprising an aqueous emulsion of an ester copolymer.

Here, according to the present invention, it is preferable that the thickness ratio of the C layer to the B layer and the D layer is 4 to 40. If the thickness ratio thereof is controlled to be less than 4, haze increases and compatibility with the window film becomes poor. If the thickness is controlled to exceed 40, it is difficult to secure the winding stability.

More preferably, the thickness ratio of 5 to 30 is stable, but the stability in the mass production step may be low, And most preferably 10 to 20, it is possible to secure the mass production stability and the winding stability.

In the three-layered polyester film according to the present invention, the relative ratio of the transverse stretching ratio to the longitudinal stretching ratio is preferably 1.1 to 1.5.

Since the stretching ratio is related to the optical properties of the polyester film like refractive index, the longitudinal stretching is mainly performed by the rolling process of the roll and the roll, and the transverse stretching is controlled by the air float type in the oven without the roll, The higher the stretching ratio in the direction, the more friction and peeling heat between the roll and the polyester film increases, which causes the rolls to be attracted to the inside of the polyester film in the longitudinal direction to remain on the glass of the building and the vehicle The draw ratio in the longitudinal direction is as low as possible and that in the lateral direction is controlled so high that the roll pull marks are not visible to the naked eye, It is possible to control the directional heat shrinkage to be high and the lateral heat shrinkage to be low.

If the relative stretching ratio is controlled to be less than 1.1, longitudinal stretching becomes high and the roll pulling marks can be visually confirmed easily. On the other hand, when the stretching ratio is controlled to exceed 1.5, longitudinal stretching is small, And may easily tear in the oven during the transverse stretching.

In other words, the elongation ratios in the longitudinal and transverse directions are optimally designed as described above to secure the basic strength and elongation, while suppressing the longitudinal roll pull marks visible to the naked eye and optimizing the temperature in the oven, It is possible to provide the convenience of work during the construction work.

More preferably, the relative stretching ratio is set to 1.1 to 1.3 so that the mass production stability can be maintained.

In addition, it is preferable to use calcium carbonate as the inert particles capable of improving the roughness and running property of the film surface in the particle layers (B, D) according to the present invention. In general, the refractive index of the organic polymer is 1.57 and the refractive index of the silica particles is 1.40. The refractive index of calcium carbonate is 1.59, which is the most similar to the refractive index of 1.64 of the polyester film. This is because the probability of being recognized is the lowest. In other words, it is possible to reduce the visibility of the inert particles seen in the transmitted or reflected light of sunlight, fluorescent light, triple wavelength, etc., thereby reducing visibility.

The average particle diameter of calcium carbonate is preferably 0.01 to 1.5 占 퐉. When the average particle diameter of calcium carbonate is less than 0.01 占 퐉, the running property of the film deteriorates during the processing of the film to cause surface scratches (dragging marks). In the case of large particle diameters exceeding 1.5 占 퐉, The cohesion and visibility of the particles are increased internally, so that it is impossible to solve the image blur which is the ultimate goal of the present invention, and the haze of the film is increased and the possibility of use as a window film is lowered and it is difficult to secure competitiveness.

More preferably, the average particle diameter of the calcium carbonate is from 0.5 to 1.5 탆, but the smaller the particle diameter, the lower the dispersibility. Thus, the stability of the calcium carbonate in the mass production step may be poor, Mu m is superior in terms of the mass production stability and the visibility of the particles is deteriorated and the phase clouding can be solved.

In addition, the polyester film for window according to an embodiment of the present invention may include a coating layer (A) comprising an aqueous emulsion of an acrylic acid alkyl ester copolymer on at least one side of a three-layer laminated polyester film. When a solvent-type acrylic acid alkyl ester copolymer is used in such a coating layer, it is very difficult to ensure the mass productivity by easily burying the solvent on the roll. Also, when a urethane or silicone type copolymer is used without using an acrylic acid alkyl ester copolymer, the utility of the dye adhesive and the hard coating agent in the window film processing is low, resulting in an increase in haze or a decrease in the degree of clearness of the film, And it is preferable to include an aqueous emulsion of the alkyl acrylate copolymer because the blocking property may be poor and the films may stick to each other.

The thickness of the coating layer according to the present invention is preferably 5 to 20 nm. When the thickness of the coating layer is less than 5 nm, adhesion of the film to the hard coating is lowered, and when the thickness of the coating layer is more than 20 nm, coating unevenness occurs and the image fogging to be solved by the high- .

The thickness of the polyester film for window according to the present invention is preferably 12 to 36 mu m.

The polyester film for a window according to the present invention preferably has a heat shrinkage ratio in the transverse direction of 0 or less among numerical values of heat shrinkage measured by allowing to stand in a thermostatic chamber at 150 캜 for 30 minutes.

Therefore, the polyester film for window according to the present invention can be produced by in-line and sequential biaxial stretching manufacturing methods with improved optical properties, mass production stability, and workability, thereby providing a large quantity of products having uniform physical properties And can also be applied very well in terms of processability and use in various use conditions.

Hereinafter, the structure and effect of the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is intended to further illustrate the present invention, and the scope of the present invention is not limited to these examples.

[ Example ]

[ Example  One]

A three-layer laminated polyester film was prepared by a sequential biaxial stretching method.

(B, D) composed of a polyester resin containing 50% by weight of an amorphous calcium carbonate compound having an average particle diameter of 1.0 mu m were formed on the upper and lower layers of the polyester resin layer (C) Layer laminate polyester film having a C layer thickness ratio of 18 for each layer and D layer was prepared. At this time, the relative ratio of the stretching ratio in the transverse direction to the stretching ratio in the longitudinal direction was set to 1.3, thereby producing a three-layer polyester film.

Specifically, polyethylene terephthalate (raw material A) containing 50% by weight of an amorphous calcium carbonate compound having an average particle size of 1.0 탆 and polyethylene terephthalate (raw material B) containing no particles and having an intrinsic viscosity of 0.62 dl / g were dried Extruded through a lamination and co-extrusion die, and cooled in a casting drum to prepare a sheet. This sheet was stretched in the longitudinal direction at a stretching ratio of 3.0 times in a temperature range of 95 占 폚 to 110 占 폚 and then stretched 3.9 times in a transverse direction at a temperature range of 110 占 폚 to 130 占 폚 to perform heat treatment at a temperature of about 230 占 폚 to obtain an average thickness And a thickness ratio of each layer (B / C / D) produced was 1: 18: 1.

Then, a coating layer having a thickness of 5 nm including an aqueous emulsion of an acrylic acid alkyl ester copolymer was formed on the B layer of the three-layer laminated polyester film to prepare a polyester film for a window.

[ Example  2]

A polyester film for windows was prepared in the same manner as in Example 1 except that the thickness of the coating layer was 10 nm.

[ Example  3]

A polyester film for windows was prepared in the same manner as in Example 1 except that the thickness of the coating layer was 20 nm.

[ Comparative Example  One]

A polyester film for windows was prepared in the same manner as in Example 1, except that the C layer thickness ratio for the B layer and the D layer was 3, respectively.

[ Comparative Example  2]

A polyester film for a window was prepared in the same manner as in Example 1 except that the C layer thickness ratio for the B layer and the D layer was 41, respectively.

[ Comparative Example  3]

A polyester film for windows was prepared in the same manner as in Example 1 except that an amorphous calcium carbonate compound having an average particle diameter of 0.005 μm was used.

[ Comparative Example  4]

A polyester film for windows was prepared in the same manner as in Example 1 except that an amorphous calcium carbonate compound having an average particle diameter of 1.6 탆 was used.

[ Comparative Example  5]

A polyester film for a window was prepared in the same manner as in Example 1, except that the relative ratio of the stretching ratio in the transverse direction to the stretching ratio in the longitudinal direction of the three-layer laminated polyester film was 1.0.

[ Comparative Example  6]

A polyester film for window was produced in the same manner as in Example 1, except that the relative ratio of the stretching ratio in the transverse direction to the stretching ratio in the longitudinal direction of the three-layer laminated polyester film was 1.6.

[ Comparative Example  7]

A polyester film for windows was prepared in the same manner as in Example 1, except that a solvent-type acrylic acid alkyl ester copolymer was used in place of the aqueous emulsion of the acrylic acid alkyl ester copolymer.

[ Comparative Example  8]

A polyester film for windows was prepared in the same manner as in Example 1, except that an aqueous emulsion of a urethane copolymer was used in place of the aqueous emulsion of an alkyl acrylate copolymer.

[ Comparative Example  9]

A polyester film for windows was prepared in the same manner as in Example 1, except that an aqueous emulsion of a silicone copolymer was used in place of the aqueous emulsion of an alkyl acrylate copolymer.

[ Comparative Example  10]

A polyester film for windows was prepared in the same manner as in Example 1 except that the thickness of the coating layer was 1 nm.

[ Comparative Example  11]

A polyester film for windows was prepared in the same manner as in Example 1 except that the thickness of the coating layer was 4 nm.

[ Comparative Example  12]

A polyester film for window was prepared in the same manner as in Example 1 except that the thickness of the coating layer was 21 nm.

[ Comparative Example  13]

A polyester film for windows was prepared in the same manner as in Example 1 except that the thickness of the coating layer was 30 nm.

[ Comparative Example  14]

A polyester film for a window was prepared in the same manner as in Example 1, except that silica, which is an amorphous silicon oxide, was used instead of the amorphous calcium carbonate compound.

The polyester films for windows according to Examples 1 to 3 and Comparative Examples 1 to 14 were evaluated through the following experimental examples and the results are shown in the following Tables 1 to 3.

[ Experimental Example ]

1. Mass production stability

In the film forming process of the polyester film according to the examples and the comparative example, evaluation was made as follows according to the percentage of yields of the acceptable products resulting from the film breakage or roll pull marks.

61% or more: ◎

56 ~ 60%: ○

51 to 55%: △

46 to 50%: X

45% or less: XX

2. Construction workability

When the polyester film according to the examples and the comparative example was applied with the heat gun on the rear side of the vehicle (the size of the rear film was about 3.0 m ² in area), evaluation was performed as follows according to the completion of a single operation within a few minutes.

Within 30 minutes: ◎

Within 31 ~ 1 hour: ○

Within 1 hour ~ 2 hours: △

Over 2 hours: X

No work: XX

Here, the case where the construction work is performed more than two hours includes the case where the construction work is required twice or more, and the case where the construction work is difficult or the work is required three times or more is included.

3. Phase Cloudiness

After completion of the construction with the heat gun on the rear side of the vehicle using the polyester film according to the embodiment and the comparative example, the temperature was about 30 ° C and the relative humidity was about 40 to 60% at about 12 to 15 hours in a clear afternoon without a cloud. RH, the vehicle license plate was read through the vehicle window and the film at a certain interval.

Interval of 31m or more: ◎

21 ~ 30m Interval: ○

16 ~ 20m interval: △

11 to 15m Interval: X

Spacing less than 10m: XX

4. Roll Trail

When a surface of about 1.6 m wide film was observed with a Polarion at intervals of 3 m, it was judged to what extent a scratch of 1 mm or more was in a period of 2 to 3 m of the stretching roll, and evaluated as follows.

None: ◎

2 / A4 or less: ○

3 to 5 / A4: △

6 to 10 / A4: X

11 / A4 or more: XX

5. Adhesion

The evaluation liquid (pink lacquer) was applied to a film sample of A4 size # 18 by Meyer bar and dried in a hot-air dryer set at 90 to 105 ° C for 1 minute. Next, 100 specimens perpendicular to each other in the TD and MD directions were prepared using a 1 mm cross cutter on a sample taken out from the dryer, and then 3M tapes were attached to the samples. And evaluated as follows.

None: ◎

1 to 5: ○

6 to 10: △

More than 10: X

6. Blocking

A sample of A4 sample was prepared by superimposing 20 pieces, then weighing 500 g, storing in an oven at 50 ° C for 24 hours, and taking out. The blocking was evaluated according to the sticking degree of the A4 sample as follows.

None: ◎

1-2 chapters: ○

Chapters 3-5: △

More than 5: X

Item	Example 1	Example 2	Example 3
Film thickness	23 탆	23 탆	23 탆
C layer thickness / B (D) layer thickness	18	18	18
Coating layer thickness	5 nm	10 nm	20 nm
Average particle diameter	1.0 탆	1.0 탆	1.0 탆
Transverse / longitudinal draw ratio	1.3	1.3	1.3
Hayes	○	○	○
Phase cloudiness	◎	◎	◎
Roll pull marks	◎	◎	◎
Mass production stability	◎	◎	◎
Construction workability	○	○	○
Adhesion	○	◎	◎
blocking	○	◎	○

Item	Comparative Example 1	Comparative Example 2	Comparative Example 3	Comparative Example 4	Comparative Example 5	Comparative Example 6	Comparative Example 7
Film thickness	23 탆	23 탆	23 탆	23 탆	23 탆	23 탆	23 탆
C layer thickness / B (D) layer thickness	3	41	18	18	18	18	18
Coating layer thickness	5 nm	5 nm	5 nm	5 nm	5 nm	5 nm	5 nm
Average particle diameter	1.0 탆	1.0 탆	0.005 탆	1.6 탆	1.0 탆	1.0 탆	1.0 탆
Transverse / longitudinal draw ratio	1.3	1.3	1.3	1.3	1.0	1.6	1.3
Hayes	XX	◎	○	○	○	○	○
Phase cloudiness	X	◎	◎	X	○	△	◎
Roll pull marks	◎	○	X	◎	XX	◎	X
Mass production stability	△	X	X	○	○	XX	XX
Construction workability	○	△	○	○	X	○	○
blocking	○	○	○	○	○	○	○

Item	Comparative Example 8	Comparative Example 9	Comparative Example 10	Comparative Example 11	Comparative Example 12	Comparative Example 13	Comparative Example 14
Film thickness	23 탆	23 탆	23 탆	23 탆	23 탆	23 탆	23 탆
C layer thickness / B (D) layer thickness	18	18	18	18	18	18	18
Coating layer thickness	5 nm	5 nm	1 nm	4 nm	21 nm	30 nm	5 nm
Average particle diameter	1.0 탆	1.0 탆	1.0 탆	1.0 탆	1.0 탆	1.0 탆	1.0 탆
Transverse / longitudinal draw ratio	1.3	1.3	1.3	1.3	1.3	1.3	1.3
Hayes	△	○	○	○	○	○	○
Phase cloudiness	△	△	◎	◎	△	X	X
Roll pull marks	◎	◎	◎	◎	◎	◎	◎
Mass production stability	◎	◎	◎	◎	◎	◎	◎
Construction workability	○	○	○	○	○	○	○
Adhesion	○	○	X	△	◎	◎	○
blocking	X	○	○	○	○	○	○

As can be seen from Tables 1 to 3, the polyester film for window according to one embodiment of the present invention disclosed in Examples 1 to 3 has excellent haze, greatly improves the image fogging property, the roll attracting property and the mass production stability It can be confirmed that the workability is excellent, and the adhesive strength and blocking resistance are also excellent. Therefore, when the polyester film for window according to the present invention is attached to the outer wall glass of a vehicle or a building, it is possible to prevent harmful ultraviolet rays from outside or to prevent glare from direct sunlight and to reduce thermal energy, It is possible to solve the phenomenon in which the image is blurred or unclear and the image is broken. In addition, since there is no drawback of the longitudinal micro-roll dragging that occurs in the manufacturing process of the polyester film, the clear exterior shape can be confirmed through the polyester film and the window film can be attached to the glass of the vehicle or the building, It is easy to shrink even in construction, so it can provide convenience to customers.

On the other hand, in the case of Comparative Example 1 in which the thickness ratio of the C layer to the B layer and the D layer was 3, not only the image fogging was observed but also the haze was extremely poor and in the case of Comparative Example 2 in which the thickness ratio was 41, And in Comparative Example 3 in which the average particle size of the amorphous calcium carbonate compound was 0.005 μm, the particle size of the calcium carbonate compound was too small to lower the surface roughness of the film, and the scratches during running Roll drag), and in the case of Comparative Example 4 in which the average particle diameter of calcium carbonate is 1.6 탆, the phase fogging property can be confirmed, and it is confirmed that the longitudinal and transverse stretching ratios are 1.0 and 1.6, respectively In the case of Example 5 and Comparative Example 6, it can be seen that the roll drag marks and the construction workability are very disadvantageous in terms of mass production stability.

In the case of Comparative Example 7 in which a solvent type acrylic acid alkyl ester copolymer was used in place of the aqueous emulsion of the alkyl acrylate copolymer, the solvent stained the process rolls, causing scratches, resulting in inferior mass production stability, , Comparative Example 9 using an aqueous emulsion of a silicone copolymer showed low haze and poor image fogging due to the low haze of the film. This has the problem of getting worse.

In Comparative Example 10 and Comparative Example 11, in which the thicknesses of the coating layers are 1 nm and 4 nm, respectively, the thickness of the coating layer is less than 5 nm, and the adhesive force is low and the adhesion with the hard coating is insufficient. In Comparative Example 12 and Comparative Example 13 in which the thicknesses of the coating layers were 21 nm and 30 nm, respectively, the thickness of the coating layer exceeded 20 nm, resulting in coating unevenness and deterioration of image fogging.

Finally, in Comparative Example 14 in which silica, which is amorphous silicon oxide, was used instead of the amorphous calcium carbonate, the refractive index of the silica particles was 1.40 and the difference between the refractive index of the silica particles and the refractive index of 1.57 was large. .

It is to be understood that the present invention is not limited to the above embodiments and various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims (8)

1. A three-layer laminated polyester film produced by a sequential biaxial stretching method and a coating layer (A) comprising an aqueous emulsion of an acrylic acid alkyl ester copolymer on at least one side of the three-layer laminated polyester film,

   The three-layer laminated polyester film is composed of an upper layer of a polyester resin layer (C) not containing fine particles and a particle layer (B, D) of a polyester resin containing an amorphous calcium carbonate compound in the lower layer,

   The thickness ratio of the C layer to the B layer and the D layer is 4 to 40,

   The stretching ratio of the three-layer laminated polyester film satisfies the following formula (1)

   (Equation 1)

   1.1? Y / X? 1.5

   , Wherein X is the longitudinal stretching ratio and Y is the transverse stretching ratio.
2. The method according to claim 1,

   And the thickness ratio of the C layer to the B layer and the D layer is 10 to 20. The polyester film for window according to claim 1,
3. The method according to claim 1,

   Wherein the stretching ratio of the three-layer laminated polyester film is 1.1 to 1.3.
4. The method according to claim 1,

   Wherein the amorphous calcium carbonate compound has an average particle diameter of 0.01 to 1.5 占 퐉.
5. 5. The method of claim 4,

   Wherein the amorphous calcium carbonate compound has an average particle diameter of 0.8 to 1.2 占 퐉.
6. The method according to claim 1,

   Wherein the coating layer has a thickness of 5 to 20 nm.
7. 7. The method according to any one of claims 1 to 6,

   Wherein the polyester film for window has a thickness of 12 to 36 占 퐉.
8. 7. The method according to any one of claims 1 to 6,

   Wherein the polyester film for window has a heat shrinkage ratio in the transverse direction of not more than 0 in a numerical value of heat shrinkage measured by being left in a thermostatic chamber at 150 캜 for 30 minutes.

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