TWI534005B - Polyester film and transparent electrode film using thereof - Google Patents

Description

Polyester film and transparent electrode film using same

The following disclosure relates to a polyester film applied to a touch screen panel and a transparent electrode film using the same. More specifically, the following disclosure relates to a polyester film capable of blocking migration of an oligomer in a polyester film to a surface upon heating and having a low turbidity change rate after heating to thereby be used for optical use. And a transparent electrode film using the same.

Optical films have been developed in accordance with the market expansion of backlight units such as liquid crystal displays (LCDs), plasma display panels (PDPs) or the like. Recently, optical films have been used for various purposes such as touch screen panels (TSPs) or the like due to the development of mobile phones, tablet PCs or the like.

In such an optical film, a biaxially stretched polyester film having excellent mechanical properties and electrical properties is required as a base film, which requires excellent transparency and visibility. However, since the surface hardness of the biaxially stretched polyester film is low and the abrasion resistance or the scratch resistance is insufficient, when the film is used as an optical member of various displays, it may be easily caused by friction or contact with the object. Surface damage. To prevent such damage, the surface of the film is hard coated. Use the membrane afterwards. Specifically, in addition to an optical film for supplying an indium tin oxide (ITO) transparent electrode for TSP, for a transparent electrode made of an Ag nanowire, a metal mesh or the like It is indispensable for the novel optical film to be hard coated. However, in the hard coating method, it is necessary to perform an independent hard coating method on one surface or both surfaces using an optical film as a substrate, and requires independent physical properties after the hard coating method (that is, no rainbow characteristics (rainbow) Free property)), so the process wear is severe and costly.

In addition, the problem of quality deterioration of optical films associated with oligomers can generally occur in various processing processes, such as ruthenium coating, diffusion coating, annealing, and the like, and thus it is required to be able to inhibit oligomer migration. Functional film to the surface.

In order to prevent migration of the oligomer of the polyester film, a method of reducing the oligomer content at the time of polymerization of the polyester film or a method of aging the polyester film at a high temperature, or a highly heat resistant polymer such as polynaphthalene has been used. Polyethylene naphthalate (PEN) or polyimide (PI). Alternatively, a method of forming a laminate film on a polyester film to control oligomer release has been used. These efforts are to control the release of the oligomer, but not enough to completely block the release of the oligomer.

One embodiment of the present invention is directed to providing a base film for a transparent electrode capable of having an excellent performance of blocking migration of an oligomer to a surface by forming a high hardness undercoat layer.

Another embodiment of the present invention is to provide a base film for a transparent electrode, which can simplify the manufacturing process and reduce the processing cost by omitting the hard coating method due to the hardness of 2H or more than 2H, thereby significantly and simultaneously improving Machinability and physics characteristic.

In a general aspect, a polyester film comprises: a base layer made of a polyester resin; and an undercoat layer laminated on both surfaces of the base layer, wherein the hardness of the undercoat layer is 2H or more And the turbidity change rate (?H) according to the following Equation 1 is 0.1% or less.

[Equation 1] △H(%)=Hf-Hi

(In Equation 1, Hf is the film haze (%) after maintaining at 150 ° C for 60 minutes, and Hi is the film haze before heating.)

In another general aspect, the transparent electrode film comprises a transparent electrode layer formed on the polyester film as described above.

The polyester film according to the present invention can provide workability and physical properties suitable for use as an optical film comprising a film for supplying a transparent electrode for a touch panel.

Further, according to the present invention, the method of coating the hard coat layer can be omitted in the manufacturing process of the transparent conductive film, which can simplify the process and reduce the cost.

Further, according to the present invention, the problem of deterioration of transparency caused by the migration of the oligomer to the surface which occurs during the process can be substantially prevented, thereby making it possible to provide a film having better optical characteristics.

Further, according to the present invention, since the hard coating method of forming the hard coat layer having a thickness of micrometers is omitted, an optical film having a thin thickness can be manufactured, so that the touch panel may be thinned, and thus the optical film can be applied. In various industrial fields.

1‧‧‧Transparent electrode layer

2‧‧‧Undercoat

3‧‧‧ basal layer

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view showing a simulation of a transparent conductive film according to the present invention, in which an undercoat layer is laminated on both surfaces of a base film.

Figure 2 shows the degree of blockage when evaluating blocking.

In the following, embodiments of the invention will be provided to describe the invention in more detail. However, the invention is not limited to the following embodiments.

According to an aspect of the invention, the polyester film comprises a base layer made of a polyester resin and an undercoat layer laminated on both surfaces of the base layer.

According to another aspect of the present invention, as illustrated in FIG. 1, the transparent electrode film comprises a transparent electrode layer 1 formed on a polyester film, the polyester film comprising a base layer 3 and two laminated on the base layer The undercoat layer 2 on the surface.

According to another aspect of the present invention, although not illustrated, the transparent electrode film includes a transparent electrode layer formed on the polyester film, the polyester film including the base layer 3 and laminated on both surfaces of the base layer The undercoat layer 2; and an adhesive layer and a protective film layer which are sequentially laminated on the surface opposite to the surface on which the transparent electrode layer 1 is formed.

In one aspect of the invention, "primer layer" means formed during the stretching process in the manufacturing process of the polyester film or coated prior to the stretching process to thereby form a stretched process. Coating.

Further, in one aspect of the invention, "transparent electrode film" means a laminate comprising a polyester film having an undercoat layer and a transparent electrode formed on one surface thereof.

The thickness of the polyester base layer is not particularly limited, but may preferably be 25 μm to 250 microns. More preferably, the thickness may range from 50 microns to 188 microns. In the case where the thickness of the base layer is less than 25 μm, it is impossible to carry out mechanical properties suitable for the optical film, and in the case where the thickness is more than 250 μm, the thickness of the film becomes too thick (not suitable for the thinness of the display device) And the optical characteristics may deteriorate.

Preferably, the base layer made of a polyester resin is made only of polyethylene terephthalate (PET) resin. In this case, the intrinsic viscosity of the polyethylene terephthalate resin used may preferably be from 0.5 deciliter/gram to 1.0 deciliter/gram, more preferably from 0.60 deciliter/gram to 0.80 deciliter/ Gram. In the case where the intrinsic viscosity of the polyethylene terephthalate resin of the base layer is less than 0.5 deciliter/g, the heat resistance may be deteriorated, and in the case where the intrinsic viscosity is more than 1.0 deciliter/g, the raw material is not easily processed. Therefore, workability may be lowered.

The base layer may contain any one or at least two inorganic particles selected from the group consisting of ceria, kaolin, and zeolite, and may be contained in an amount ranging from 10 ppm to 1000 ppm by weight of the entire polyester resin.

The present invention comprises an undercoat layer on both surfaces of a polyester film, wherein the undercoat layer prevents deterioration of quality due to precipitation of an oligomer substantially in a post-treatment process (transparent electrode lamination) Produced in the process of polymerizing PET in a process or the like, and in addition to improving the adhesion to other substrates in the optical film according to the related art, acting as a hard coat layer to prevent surface scratches such as those generated during a processing process or the like. phenomenon. Therefore, in order to function as a hard coat layer as described above, it is necessary to adjust the surface hardness of the undercoat layer.

The hard coat layer for controlling the surface scratches generated during the process is formed in a unit thickness of micrometer (μm), and in general, the hard coat layer is formed on the undercoat layer of the polyester film by a separate process to perform its performance. . In this case, due to the implementation of the independent process, Therefore, in addition to the increase in product cost, the cost may increase due to a decrease in production or the like, resulting in an expensive product group. However, according to the present invention, the improved hardness of the undercoat layer has been developed so that the polyester film can function as a hard coat without developing a method of forming a separate hard coat layer. The polyester film can be coated as a substrate for a transparent electrode.

More specifically, preferably, the hardness of the undercoat layer is 2H or more, and the turbidity change rate (?H) according to the following Equation 1 is 0.1% or less.

[Equation 1] △H(%)=Hf-Hi

(In Equation 1, Hf is the film haze (%) after maintaining at 150 ° C for 60 minutes, and Hi is the film haze before heating.)

In the range where the hardness of the undercoat layer is 2H or more, the scratches generated during the post-processing process can be controlled without forming a separate hard coat layer.

The turbidity change rate is a physical property related to the migration of the oligomer, and when the film turbidity change rate after maintaining at 150 ° C for 60 minutes is 0.1% or less, it is judged that the migration of the oligomer is almost blocked.

According to the present invention, in order to provide a polyester film which satisfies the physical properties mentioned above, the undercoat layer may be adjusted so as to have a dry coating thickness of from 20 nm to 150 nm. In this case, the dry coating thickness means the thickness of the undercoat layer in the state of the final dried undercoat layer after the formation of the undercoat layer. In the case where the dry coating thickness is less than 20 nm, the oligomer blocking property may not be sufficiently achieved, so that in the case where the hardness of the base film is HB level or F level, although the surface hardness is 2H or more, it is possible Damage is caused, such as scratches or the like. Further, in the case where the dry coating thickness is more than 150 nm, coating spots may be exhibited, and the possibility of blocking phenomenon in which the undercoat layers adhere to each other after film bending is increased may be improved. Coating spots cause light interference and block light Transmission, and the barrier phenomenon may cause a surface picking phenomenon of the product or a defect of the film breakage, but in the case where the dry coating thickness of the undercoat layer satisfies the range mentioned above, as described above The problem can be solved. That is, it is preferable to include a combined configuration that simultaneously satisfies the hardness other than the turbidity change rate and the dry coating thickness range of the undercoat layer, which is more preferable in carrying out the object of the present invention.

Further, the undercoat layer satisfying the physical properties mentioned above may be formed of a coated and dried acrylic water-dispersible resin composition.

The acrylic water-dispersible resin composition may contain any one or at least two kinds of inorganic particles selected from cerium oxide, kaolin, and zeolite, and the content of the inorganic particles used may preferably be the entire primer. The coating composition is from 0.1% by weight to 4.0% by weight, more preferably from 2.0% by weight to 3.0% by weight. In the case where the inorganic particle size is less than 2.0 μm, the bending property may be deteriorated by the protrusion of the particles, and in the case where the size is larger than 4.0 μm, the transparency may be deteriorated due to the influence of the size, and thus the turbidity of the product may be increased.

In one aspect of the invention, the polyester film is produced without limitation, but the polyester film can be melt extruded from the PET sheet in a melt extruder, followed by casting and biaxially stretching the extruded PET. Come to get. More specifically, a single extruder is used for simultaneous melt extrusion, casting, cooling, and then sequentially biaxially stretching polyester and additives such as inorganic particles, such as ceria, kaolin, and zeolite or analog.

In one aspect of the invention, the water-dispersible resin composition can be applied by an in-line coating method during the manufacturing process of the polyester film. That is, in the production of the polyester base film, the undercoat layer can be produced by applying water dispersibility by an in-line coating method before the stretching process or between the first stretching process and the second stretching process. a resin composition, and then stretching the applied composition, and during the second stretching and heat setting process The heating causes the water to vaporize, so that an undercoat layer can be formed. The coating method is not limited as long as the method is known in the art.

The index matching layer and the transparent electrode layer may be formed on the upper portion of the polyester film according to the present invention, and an adhesive layer and a protective film layer may be formed under the polyester film. The transparent electrode layer may be made of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), tin oxide (SnO ₂ ), carbon nanotubes. Any one of the silver nanowires and the metal grid. After the formation of these functional coatings, the release of the oligomer can be blocked even in the case of heating the polyester film, so that the optical properties can be maintained, and the hardness of the polyester film is 2H or more, so that the polyester The film can act as a hard coat. Therefore, the polyester film according to the present invention can be suitably used as a film for a transparent electrode.

In the following, examples will be provided to describe the invention in more detail. However, the invention is not limited to the following examples.

In the following, physical properties are measured by the following measurement methods.

1) Turbidity change rate (△H)

The film was placed in an upper open box having a height of 3 cm, a length of 21 cm and a width of 27 cm, and heat-treated at 150 ° C for 60 minutes to allow the oligomer to migrate to the surface of the film. Subsequently, the film was allowed to stand for 5 minutes, and the turbidity value was measured using a turbidity meter (Nippon Denshoku, model NDH 5000) according to JIS K 715 standard.

The turbidity change rate was calculated according to the following Equation 1.

[Equation 1] △H(%)=Hf-Hi

(In Equation 1, Hf is the film haze (%) after maintaining at 150 ° C for 60 minutes, and Hi is the film haze before heating.)

2) Surface hardness of the undercoat layer

After the base film coated with the coating composition was cut at a size of 10 meters × 10 meters (length × width), a pencil hardness meter (model SB-191, an electric pencil hardness) was used according to JIS K-5600 standard. Measure the hardness. More specifically, after the base film is attached to the sled, the lead of the pencil specified in the KS G2603 is placed on the surface of the film at an angle of 45 degrees, and the film is moved while being pressed by a load of 1 kg to borrow This scratches the surface, and thus the surface hardness of the film is judged from the degree of damage of the film surface. As for the pencil, a total of 16 special pencils were applied from 6B to 8H.

Pencil hardness order: (hard) 8H 7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B (soft)

3) Thickness of the undercoat layer

In the monolithic film coated with the coating composition, five points at intervals of 1 m were specified in a direction perpendicular to the machine direction (TD), and scanning electron microscopy (SEM) was used (Hitachi) The S-4300 (Hitachi S-4300)) measures its cross section. Further, the specified cross section was enlarged at a magnification of 50,000×, the thickness of 30 points was measured in the cross section, and the average value thereof was calculated.

4) Block

After pressing the film for 1 minute at a predetermined temperature using a thermal gradient tester (TOYOSEIKI) at a pressure of 0.4 MPa, the platen was removed, and Confirm the degree of compression. The difference in the degree of compression is evaluated based on FIG.

Evaluation under constant humidity: Tested in a constant temperature and humidity chamber (temperature between 20 ° C and 25 ° C and relative humidity (RH) of 40% to 50%).

Evaluation under increased humidity: The membrane was tested at 100% relative humidity (RH) using an ultrasonic humidifier.

5) Adhesion (cross cut)

After the optical film on which the undercoat layer of each composition was formed was formed, the AgNW composition was applied onto one surface thereof. Subsequently, the adhesion test tape (Nichban) was made by marking the line at a spacing of 1 mm on a film of 1 cm × 1 cm using a cross hatch cutter (YCC-230/1). No. 405) adhered to it and evaluated the adhesion at room temperature by separating the adhesive tape three times.

6) Scratches

After the optical film on which the undercoat layer of each composition is formed is formed, the optical film is subjected to a coating method of applying an AgNW composition to one surface thereof. When the optical film was coated, a searchlight (CP-35NP1, POLARION Corp.) was used to confirm whether or not the method was caused by the method on the surface after the uncoated AgNW composition of the undercoat layer. Scratches caused by friction with the guide rolls.

7) Spots in the undercoat

Forming an optical film on which an undercoat layer according to each composition is formed Thereafter, the corresponding film was cut in a size of 1 m × 1 m (length × width), and a spotlight was confirmed on the surface using a searchlight (CP-35NP1, Prairie).

[Example 1] Production of a high-hardness polyester film having excellent oligomer blocking properties

The polyethylene terephthalate flake having an intrinsic viscosity of 0.65 dl/g and 50 ppm of cerium oxide particles having an average particle size of 2.7 μm by weight of the total polyethylene terephthalate are melt-squeezed and Casting to make a sheet. Subsequently, after the acrylic water-dispersible resin composition (surface hardness after drying: 2H) was applied onto both surfaces of the sheet by a bar coating method, the temperature was raised to 110 at a rate of 1 ° C/sec. °C to 150 ° C, and the coated sheet was stretched 3.5 times in the transverse direction (TD) by preheating and dried. Subsequently, heat treatment was carried out in a 5-stage tenter at 230 ° C to relax the heat-treated film by 10% in the machine direction and the transverse direction to heat set at 200 ° C to thereby produce a thickness of 125 μm and two surface coatings. A biaxially stretched film having a primer layer having a thickness of 20 nm was applied.

[Example 2] Production of a high-hardness polyester film having excellent oligomer blocking properties

The polyethylene terephthalate flake having an intrinsic viscosity of 0.65 dl/g and 50 ppm of cerium oxide particles having an average particle size of 2.7 μm by weight of the total polyethylene terephthalate are melt-squeezed and Casting to make a sheet. Subsequently, after the acrylic water-dispersible resin composition (surface hardness after drying: 2H) was applied onto both surfaces of the sheet by a bar coating method, the temperature was raised to 110 at a rate of 1 ° C/sec. °C to 150 ° C, and the coated sheet was stretched 3.5 times in the transverse direction (TD) by preheating and dried. Subsequently, at a temperature of 230 ° C in a 5-stage tenter The heat treatment was performed to relax the heat-treated film by 10% in the machine direction and the transverse direction to heat set at 200 ° C to produce a primer having a thickness of 125 μm and both surfaces coated with a thickness of 80 nm. Biaxially stretched film.

[Example 3] Production of a high-hardness polyester film having excellent oligomer blocking properties

The polyethylene terephthalate flake having an intrinsic viscosity of 0.65 dl/g and 50 ppm of cerium oxide particles having an average particle size of 2.7 μm by weight of the total polyethylene terephthalate are melt-squeezed and Casting to make a sheet. Subsequently, after the acrylic water-dispersible resin composition (surface hardness after drying: 2H) was applied onto both surfaces of the sheet by a bar coating method, the temperature was raised to 110 at a rate of 1 ° C/sec. °C to 150 ° C, and the coated sheet was stretched 3.5 times in the transverse direction (TD) by preheating and dried. Subsequently, heat treatment was carried out in a 5-stage tenter at 230 ° C to relax the heat-treated film by 10% in the machine direction and the transverse direction to heat set at 200 ° C to thereby produce a thickness of 125 μm and two surface coatings. A biaxially stretched film having a primer layer having a thickness of 150 nm was provided.

[Comparative Example 1]

The polyethylene terephthalate flake having an intrinsic viscosity of 0.65 dl/g and 50 ppm of cerium oxide particles having an average particle size of 2.7 μm by weight of the total polyethylene terephthalate are melt-squeezed and Casting to make a sheet. Subsequently, after the acrylic water-dispersible resin composition (surface hardness after drying: 2H) was applied onto both surfaces of the sheet by a bar coating method, the temperature was raised to 110 at a rate of 1 ° C/sec. °C to 150 ° C, and the coated sheet was stretched 3.5 times in the transverse direction (TD) by preheating and dried. Subsequently, at a temperature of 230 ° C in a 5-stage tenter The heat treatment is performed to relax the heat-treated film by 10% in the machine direction and the transverse direction to heat-set at 200 ° C to produce a primer having a thickness of 125 μm and both surfaces coated with a thickness of 10 nm. Biaxially stretched film.

[Comparative Example 2]

The polyethylene terephthalate flake having an intrinsic viscosity of 0.65 dl/g and 50 ppm of cerium oxide particles having an average particle size of 2.7 μm by weight of the total polyethylene terephthalate are melt-squeezed and Casting to make a sheet. Subsequently, after the acrylic water-dispersible resin composition (surface hardness after drying: 2H) was applied onto both surfaces of the sheet by a bar coating method, the temperature was raised to 110 at a rate of 1 ° C/sec. °C to 150 ° C, and the coated sheet was stretched 3.5 times in the transverse direction (TD) by preheating and dried. Subsequently, heat treatment was carried out in a 5-stage tenter at 230 ° C to relax the heat-treated film by 10% in the machine direction and the transverse direction to heat set at 200 ° C to thereby produce a thickness of 125 μm and two surface coatings. A biaxially stretched film having an undercoat layer having a thickness of 300 nm was provided.

[Comparative Example 3]

A binder (P3208, Rohm & Haas Company) containing 40% by weight of methyl methacrylate and 40% by weight of ethyl acrylate and 20% by weight of melamine was used.

2% by weight (solid content) of a binder and 0.3% by weight of a hydrazine-based wetting agent (BYK 348, BYK CHEMIE Corp.) were added to water and stirred for 2 hours to prepare a total solid content of 2.3% by weight. A water-dispersible resin composition.

Using the water-dispersible resin composition prepared by the same method as in Example 1, a biaxially stretched film having a thickness of 125 μm and both surfaces coated with an undercoat layer having a surface hardness of F was produced. The dried coating of the undercoat layer made of the composition had a thickness of 80 nm.

[Comparative Example 4]

By making 9% by weight of a polyester polyol (polyethylene adipatediol having a weight average molecular weight of 1000), 10% by weight of hexamethylene diisocyanate, and 1% by weight of an ionic group Reactive emulsifier (Asahi Denka, Adecaria Soap, also known as polyoxyethylene allyl glycidyl decyl phenyl ether sulfonate (SETM)) and 80 The % by weight water was reacted with each other to prepare an aqueous polyurethane binder having a solid content of 20% by weight.

4% by weight (solid content) of a binder and 0.3% by weight of a hydrazine-based wetting agent (BYK 348, BYK Chemical Co., Ltd.) were added to water and stirred for 2 hours to prepare a water-dispersible resin having a total solid content of 4.3% by weight. Things.

Using the water-dispersible resin composition prepared by the same method as in Example 1, a biaxially stretched film having a thickness of 125 μm and both surfaces coated with an undercoat layer having a surface hardness of F was produced. The dried coating of the undercoat layer made of the composition had a thickness of 80 nm.

[Comparative Example 5]

By making 9 wt% polyester polyol (polyethylene glycol adipate having a weight average molecular weight of 1000), 10 wt% hexamethylene diisocyanate, 1 wt% A reactive emulsifier having an ionic group (Japan Asahi Kasei, Adcaglia soap, that is, polyoxyethylene allyl glycidyl decyl phenyl ether sulfonate (SETM)) and 80% by weight of water Reacting with each other, an aqueous polyurethane binder having a solid content of 20% by weight was prepared.

4% by weight (solid content) of a binder and 0.3% by weight of a hydrazine-based wetting agent (BYK 348, BYK Chemical Co., Ltd.) were added to water and stirred for 2 hours to prepare a water-dispersible resin having a total solid content of 4.3% by weight. Things.

Using the water-dispersible resin composition prepared by the same method as in Example 1, a biaxially stretched film having a thickness of 125 μm and both surfaces coated with an undercoat layer was produced. The dried coating of the undercoat layer made of the composition had a thickness of 80 nm. A hard coat layer having a surface hardness of 2H and a thickness of 3 μm after drying was formed on both surfaces of the polyester film obtained as described above by a UV curing method, thereby producing a double-sided hard coat film.

[Evaluation 1] Evaluation of pencil hardness and oligomer blocking efficiency (turbidity change rate)

The pencil surface hardness (JIS K-5600 standard) of the polyester film produced in the measurement examples and the comparative examples was measured. Further, the polyester film was heat-treated at 150 ° C for 60 minutes and allowed to stand for 5 minutes, and the haze value before and after the heat treatment was measured using a turbidity meter (Nippon Electric Co., model NDH 5000).

As shown in Table 1, in the films of Examples 1 to 3 according to the present invention, the thickness of the undercoat layer was in the range of 20 nm to 150 nm, and the surface hardness was ensured to be 2H. Therefore, it was confirmed from the results of the film according to the present invention that it is not necessary to form a separate hard coat layer. Further, the film satisfies the desired physical properties in terms of turbidity change rate (0.1% or less). This result means that the transparency is not deteriorated by the migration of the remaining oligomer in the PET film, which is the substrate, to the surface during the post-processing process (including heat treatment).

However, in Comparative Example 1 in which the thickness of the undercoat layer was 10 nm, it was confirmed that it was difficult to secure the surface hardness of the desired layer. Further, in Comparative Example 2 in which the thickness of the undercoat layer was 300 nm, it was confirmed that the surface hardness and the turbidity change rate of the desired level were ensured, but it was impossible to mass-produce the product because the coating spots and the blocking phenomenon were generated. The coating spot is an important processing item in the processing item of the appearance of the product due to the interference of the light transmitted from the backlight unit (BLU) due to the occurrence of the coating spot and hindering the light transmission in the visual field of the user. In addition, the phenomenon of blocking is that the undercoat layers on the two surfaces of the product adhere to each other, and the surface peeling phenomenon or film breakage may occur when the product is unfolded, so that the blocking effect is an important treatment in consideration of the processing performance of the user. One of the projects.

Further, in Comparative Example 3 corresponding to the acrylic adhesive product generally used, physical properties such as a turbidity change rate of 0.1% or less were ensured, and thus oligomer blocking performance was ensured. However, it is difficult to ensure that the pencil hardness of the desired level is generated during the post-processing process, and thus scratches or the like are generated, thus requiring a separate hard coat layer.

In Comparative Example 4, a commonly used urethane base adhesive was used, It is advantageous for the adhesion (adhesion) of the product, but the value of the turbidity change rate is increased to about 7%, so that the transparency is deteriorated by the oligomer, and it is fragile against the stability of heat and moisture in view of blocking. It is similar to the urethane base adhesive according to the related art. The reason is that it is impossible to carry out the oligomer migration blocking effect during the post-processing process, so the quality is continuously deteriorated due to the whitening phenomenon, and quality problems such as diamond marks or the like are generated during the cutting process.

Meanwhile, in Comparative Example 5 corresponding to a hard coat film produced by forming a hard coat layer on both surfaces of the double-sided primer coating film, such as surface hardness, turbidity change rate, surface characteristics, and the like were satisfied. Physical characteristics. Therefore, in comparing the present invention with Comparative Example 5 in which a hard coat layer was formed, it was confirmed that the process can be simplified according to the present invention, and the oligomer blocking effect which is structurally realized in the method according to the related art can be realized and improved.

[Evaluation 2] Evaluate the effectiveness of coating by silver nanowire coating

The silver nanowire transparent electrode layer was coated on one surface of the polyester film produced in the examples and the comparative examples, and the adhesion between the undercoat layer and the transparent electrode layer and the workability such as scratches or the like were confirmed. The production of things.

As shown in Table 2, it was confirmed that in the films of Examples 1 to 3 according to the present invention, the adhesion with the transparent electrode layer was excellent, and there was no problem in the generation of scratches, so the film could be used as A novel base film application for transparent electrodes. another Further, in comparing the present invention with Comparative Example 5 which was produced by the related art to thereby include a hard coat layer, there was no difference in the degree of adhesion and scratch generation. Therefore, it can be confirmed that all the physical characteristics fully realized in the method according to the related art can be realized even if the process is simplified.

In contrast, in Comparative Example 1 in which the thickness of the undercoat layer was 10 nm, it was difficult to control the scratch in the silver nanowire coating method because the surface hardness was F level. Further, in Comparative Example 3, it was confirmed that even if the turbidity change rate is suitable, since the surface hardness of the conventional undercoat layer is F-level and it is difficult to control scratches in the manufacturing process, it is impossible to use the film as a coating. Base film application of transparent electrodes. Therefore, it has been confirmed that it is difficult to achieve the adhesive force required for the substrate for the transparent electrode in the case of the acrylic adhesive product group which is generally used.

The exemplary embodiments of the invention are described above, but the invention may include various modifications, modifications, and equivalents. It will be appreciated that the present invention is similarly applicable by suitably modifying the exemplary embodiments. Therefore, the above-mentioned contents do not limit the invention as defined by the accompanying claims.

1‧‧‧Transparent electrode layer

2‧‧‧Undercoat

3‧‧‧ basal layer

Claims (8)

A polyester film comprising: a base layer made of a polyester resin; and an undercoat layer laminated on both surfaces of the base layer, the undercoat layer having a dry coating thickness of 20 nm to 150 nm, wherein in the undercoat layer, the hardness is 2H or more than 2H, and the turbidity change rate (ΔH) according to the following Equation 1 is 0.1% or less: [Equation 1] ΔH (%)=Hf-Hi (In Equation 1, Hf is the haze (%) of the film after maintaining at 150 ° C for 60 minutes, and Hi is the turbidity of the film before heating). The polyester film of claim 1, wherein the undercoat layer is formed by an in-line coating method. The polyester film according to claim 1, wherein the undercoat layer is formed by coating and drying an acrylic water-dispersible resin composition. The polyester film of claim 1, wherein the base layer contains any one or at least two inorganic particles selected from the group consisting of ceria, kaolin, and zeolite. The polyester film of claim 1, wherein the base layer is made of polyethylene terephthalate having an intrinsic viscosity of from 0.5 dl/g to 1.0 dl/g. A transparent electrode film comprising a transparent electrode layer formed on the polyester film according to any one of claims 1 to 5. The transparent electrode film according to claim 6, wherein the transparent electrode layer is made of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (zinc oxide; Any one selected from the group consisting of ZnO), tin oxide (SnO ₂ ), carbon nanotubes, silver nanowires, and metal mesh. The transparent electrode film according to claim 6, further comprising an adhesive layer and a protective film layer formed on a surface opposite to a surface on which the transparent electrode layer is formed.