CN106164145B

CN106164145B - Polyester film and transparent electrode film using same

Info

Publication number: CN106164145B
Application number: CN201580018159.9A
Authority: CN
Inventors: 郑斗焕; 朴载奉; 崔城兰
Original assignee: Kolon Industries Inc
Current assignee: Kolon Industries Inc
Priority date: 2014-03-31
Filing date: 2015-03-31
Publication date: 2020-05-22
Anticipated expiration: 2035-03-31
Also published as: TW201545878A; CN106164145A; JP2017514722A; WO2015152603A1; TWI534005B; KR20150113911A

Abstract

The present invention provides a polyester film for a touch screen panel and a transparent electrode film using the same, and more particularly, to a polyester film capable of blocking oligomers in the polyester film from migrating to the surface upon heating and having a low haze change rate after heating to be used for optical purposes, and a transparent electrode film using the same.

Description

Polyester film and transparent electrode film using same

Technical Field

The present invention relates to a polyester film for a touch screen panel, and a transparent electrode film using the same. More particularly, the present invention relates to a polyester film capable of blocking oligomers in the polyester film from migrating to the surface upon heating and having a low haze change rate after heating to be used for optical applications, and a transparent electrode film using the same.

Background

The optical film is developed as the market of a backlight unit (BLU) such as a Liquid Crystal Display (LCD), a Plasma Display Panel (PDP), etc. is expanded. Recently, mobile phones, tablet computers, and the like have been used for various purposes such as a Touch Screen Panel (TSP) due to the development thereof.

In such an optical film, excellent transparency and visibility are required, and a biaxially oriented polyester film having excellent mechanical and electrical properties is used as a base film. However, since the biaxially stretched polyester film has low surface hardness and insufficient abrasion resistance or scratch resistance, when the film is used as an optical member of various displays, surface damage easily occurs due to friction or contact with an object. In order to prevent such damage, a film is used after hard coating on the surface thereof. In particular, in addition to an optical film for an Indium Tin Oxide (ITO) transparent electrode coated to TSP, a novel optical film for a transparent electrode formed of Ag nanowires, metal mesh, or the like must be hard-coated. However, in the hard coating process, it is required to perform a separate hard coating process on one surface or both surfaces using an optical film as a substrate, and after the hard coating process, separate physical properties, i.e., non-color properties (a rainbow free property), are required, so that process loss is severe and cost is expensive.

In addition, the optical film often suffers from quality deterioration problems associated with oligomers during various processes such as a corner coating process (a prism coating process), a diffusion coating process, an annealing process, etc., and thus a functional film capable of suppressing migration of oligomers to the surface is required.

In order to prevent the migration of oligomers of the polyester film, a method of reducing the content of oligomers when polymerizing the polyester film, or a method of aging the polyester film at a high temperature, or a high heat-resistant polymer such as polyethylene naphthalate (PEN) or Polyimide (PI) is used. Alternatively, a method of forming a laminate film on a polyester film to control the release of the oligomer is used. These efforts are directed to controlling the release of oligomers, but are not sufficient to completely retard the release of oligomers.

Disclosure of Invention

Technical problem

An embodiment of the present invention is directed to providing a base film for a transparent electrode, which can have excellent properties of retarding migration of oligomers to the surface by forming a primer layer of high hardness.

An embodiment of the present invention is directed to providing a base film for a transparent electrode, which can simplify a manufacturing process and reduce process costs by omitting a hard coating process due to the hardness of the base film of 2H or more, thereby being capable of remarkably and simultaneously improving processability and physical properties.

Technical scheme

In one general aspect, a polyester film comprises: a base layer formed of a polyester resin; and a primer layer laminated on both surfaces of the substrate layer,

wherein the hardness of the undercoat layer is 2H or more, the haze 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 haze of the film after it is maintained at 150 ℃ for 60 minutes, Hi is the haze of the film before heating.

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

Advantageous effects

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

In addition, according to the present invention, in the process of preparing the transparent conductive film, the process of applying the hard coating layer may be omitted, and thus the process may be simplified and the cost may be reduced.

Further, according to the present invention, since the problem of deterioration of transparency due to migration of oligomers to the surface during the process can be substantially avoided, a film having more excellent optical properties can be provided.

Further, according to the present invention, since a hard coating process of forming a hard coating layer having a thickness of a micrometer unit is omitted, an optical film having a thin thickness can be prepared, and thus a touch panel can be thinned, and thus, the optical film can be applied to various industrial fields.

Drawings

Fig. 1 is a simulation diagram showing a transparent conductive film in which a primer layer according to the present invention is laminated on both surfaces of a base film;

fig. 2 shows the degree of retardation when evaluating retardation.

Reference numerals

1: transparent electrode layer

2: base coat

3: base layer

Detailed Description

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

According to one aspect of the present invention, a polyester film comprises: a substrate layer formed of a polyester resin and a primer layer laminated on both surfaces of the substrate layer.

As shown in fig. 1, according to another aspect of the present invention, a transparent electrode film includes a transparent electrode layer 1 formed on a polyester film including a base layer 3 and primer layers 2 laminated on both surfaces of the base layer.

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

In one aspect of the present invention, the "primer layer" refers to a coating layer formed in a stretching process in a process of preparing a polyester film, or coated before the stretching process so as to be formed through the stretching process.

In addition, in one aspect of the present invention, the "transparent electrode film" refers to a laminate including a polyester film provided with 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 be preferably 25 to 250 μm. More preferably, the thickness may be 50 to 188 μm. When the thickness of the base layer is less than 25 μm, mechanical properties suitable for the optical thin film cannot be realized, and when the thickness is more than 250 μm, the thickness of the thin film becomes excessively thick, not suitable for thinning of the display device, and optical properties may be deteriorated.

Preferably, the base layer formed of the polyester resin is formed of only polyethylene terephthalate (PET) resin. At this time, the intrinsic viscosity of the polyethylene terephthalate resin used is preferably 0.5 to 1.0dl/g, more preferably 0.60 to 0.80 dl/g. When the intrinsic viscosity of the polyethylene terephthalate resin of the base layer is less than 0.5dl/g, heat resistance may be reduced, and when the intrinsic viscosity is more than 1.0dl/g, it is not easy to process raw materials, and thus processability may be reduced.

The base layer may contain any one or at least two inorganic particles selected from silica, kaolin, zeolite, and may be contained in a range of 10 to 1000ppm based on the weight of the entire polyester resin.

The present invention includes primer layers on both surfaces of the polyester film, wherein the primer layers can prevent quality degradation due to precipitation of oligomers, which must occur when PET is polymerized, in addition to improving adhesion to other substrates as in the optical film of the related art, and function as hard coatings preventing the occurrence of phenomena such as surface scratches during the processing process. Therefore, in order to function as the hard coat layer as described above, the surface hardness of the undercoat layer needs to be adjusted.

The hard coating layer for controlling surface scratches occurring during the process is formed to have a micrometer (μm) unit, and in general, the hard coating layer is formed on the primer layer of the polyester film through a separate process, thereby achieving its properties. At this time, since a separate process is performed, in addition to an increase in production cost, cost may increase due to a decrease in yield, etc., thereby forming an expensive product group. However, according to the present invention, a product that increases the hardness of the undercoat layer is developed, thereby developing a polyester film that can serve as a hard coat layer without performing a process of forming a separate hard coat layer. The polyester film can be used as a substrate for a transparent electrode.

In more detail, the hardness of the undercoat layer is preferably 2H or more, and the haze 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 haze (%) of the film after it is maintained at 150 ℃ for 60 minutes, and Hi is the haze of the film before heating.

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

The haze change rate is a physical property relating to the migration of the oligomer, and when the haze of the film is 0.1% or less after being maintained at 150 ℃ for 60 minutes, it is judged that the migration of the oligomer is almost retarded.

According to the present invention, in order to provide a polyester film satisfying the above physical properties, the primer layer may be adjusted to a dry coating thickness of 20 to 150 nm. At this time, the dry coating thickness refers to the thickness of the undercoat layer in a state where the undercoat layer is completely dried after the formation of the undercoat layer. When the dry coating thickness is less than 20nm, the oligomer blocking performance may not be sufficiently realized, and thus even if the surface hardness is 2H or more, damage such as scratching may occur at the level of HB, F of the base film hardness. In addition, when the dry coating thickness is more than 150nm, coating spots are shown, and the possibility of occurrence of a blocking phenomenon (blocking phenomenon) in which primer layers adhere to each other after winding the film is increased. The coating mottle causes interference of light to hinder the transmission of light, and the blocking phenomenon may cause a surface tearing phenomenon or a film tearing defect of the product, but when the dry coating thickness of the primer layer satisfies the above range, the problems as described above may be solved. That is, in view of achieving the object of the present invention, it is more preferable to include an arrangement that satisfies a combination of ranges of both hardness of the undercoat layer and dry coating thickness in addition to the haze change rate.

In addition, the primer layer for satisfying the above physical properties may be formed by coating and drying the acrylic water dispersion resin composition.

The water-dispersed resin composition may contain any one or at least two inorganic particles selected from silica, kaolin, zeolite, as needed, and the content of the inorganic particles used may preferably be 0.1 to 4.0 wt%, more preferably 2.0 to 3.0 wt%, based on the entire undercoat layer composition. When the size of the inorganic particles is less than 2.0 μm, the winding property may be reduced due to the protrusion of the particles, and when the size is more than 4.0 μm, the transparency may be reduced due to the size effect, and thus the haze of the product may be increased.

In one aspect of the present invention, the polyester film is prepared without limitation, but the polyester film may be obtained by melt-extruding a PET sheet in a melt extruder, and then casting and biaxially stretching the extruded PET. In more detail, after simultaneously melt-extruding the polyester with additives such as inorganic particles (e.g., silica, kaolin, and zeolite) using a single extruder, casting, cooling, and then sequentially biaxial stretching are performed.

In one aspect of the present invention, the water dispersible resin composition may be coated by an inline coating method in a process of preparing a polyester film. That is, in preparing the polyester-based film, the undercoat layer may be prepared as follows: the water-dispersed resin composition is coated by an inline coating method before a stretching process or between a primary stretching and a secondary stretching process, and then the coated composition is stretched and water is evaporated by heating during a secondary stretching and heat-setting process, whereby an undercoat layer may be formed. The coating method is not limited as long as the method is known.

An index matching layer (index matching layer) and a transparent electrode layer may be formed on an upper portion of the polyester film according to the present invention, and an adhesive layer and a protective film layer may be formed on a lower portion of the polyester film. The transparent electrode layer may be made of a material selected from Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), zinc oxide (ZnO), tin dioxide (SnO)₂) And carbon nanotubes, silver nanowires, and metal meshes. After these functional coatings are formed, the release of oligomers can be retarded even when the polyester film is heated, so that the optical properties can be maintained, andand the hardness of the polyester film is more than 2H, so the polyester film can be used as a hard coating. Therefore, the polyester film according to the present invention can be suitably used as a film for a transparent electrode.

Hereinafter, examples are provided for describing the present invention in more detail. However, the present invention is not limited to the following examples.

Hereinafter, the physical properties were measured by the following measurement methods.

1) Fog degree change rate (△ H)

The film was placed in a box having an upper opening and a height of 3cm, a length of 21cm and a width of 27cm, and the oligomer was transferred to the surface of the film by heat treatment at 150 ℃ for 60 minutes. Then, the film was left to stand for 5 minutes, and the haze value was measured using a haze meter (Nippon Denshoku, Model NDH 5000) in accordance with JIS K715.

The haze change rate is calculated according to the following equation 1.

[ equation 1]

△H(％)＝Hf-Hi

2) Surface hardness of the primer layer

After the base film coated with the coating composition was cut into a size of 10cm × 10cm (length × width), hardness was measured using a pencil hardness meter (model SB-191, electric pencil hardness meter) according to JIS K-5600 standard. In more detail, after the base film was adhered to the bracket, the surface hardness of the film was judged from the degree of damage of the film surface by applying a load of a pencil specified in KS G2603 at an angle of 45 degrees to the film surface and moving while pressing the film with a load of 1kgf to scratch the surface. As the pencil, 16 kinds of special pencils in total from 6B to 8H were used.

Pencil hardness order: (hard) 8H 7H 6H 5H 4H 3H 2 HFHB 2B 3B 4B 5B 6B (Soft)

3) Thickness of the primer layer

On the entire surface of the film coated with the coating composition, 5 points were designated at intervals of 1m in The Direction (TD) perpendicular to the longitudinal direction, the cross section thereof was measured using a scanning electron microscope (SEM, S-4300), the designated portion was enlarged at a magnification of 50000 times, the thickness of 30 points within the portion was measured, and the average value thereof was calculated.

4) Adhesion (blocking)

After laminating the films at four preset temperatures for 1 minute under a pressure condition of 0.4MPa using a thermal gradiometer (TOYOSEIKI), the press plates were removed, and the degree of lamination was confirmed. The difference in degree of pressing was evaluated according to fig. 2.

-evaluation under constant humidity: the test is carried out in a constant temperature and humidity chamber with the temperature of 20-25 ℃ and the Relative Humidity (RH) of 40-50%.

-evaluation under humidification: the test was performed on the film using an ultrasonic humidifier at a Relative Humidity (RH) of 100%.

5) Adhesion (crosscut)

After preparing an optical film on which an undercoat layer varying with each composition was formed, an AgNW composition was coated on one surface thereof. Then, the adhesive force at room temperature was evaluated by the following method: an adhesive force test tape (Nichbann No.405) was adhered thereto by marking a 1cm X1 cm film at 1mm intervals with a grid cutter (YCC-230/1), and the adhered tape was peeled off and measured three times.

6) Scratch and mar

After preparing an optical film on which an undercoat layer varying with each composition was formed, the optical film was subjected to a coating process of coating one surface thereof with an AgNW composition. When the optical film was subjected to the coating process, a searchlight (CP-35NP1, palaion Corp.) was used to confirm whether scratching with the guide roll due to the performance of the process occurred in the undercoat layer on the back side of the uncoated AgNW composition.

7) Smut in undercoats

After preparing the optical films on which the primer layers varied depending on the respective compositions were formed, after cutting the respective films into a size of 1m × 1m (length × width), it was confirmed whether or not stains were generated on the surfaces using a searchlight (CP-35NP1, polar Corp.).

[ example 1]High hardness polyester with excellent oligomer blocking propertiesPreparation of films

A sheet was prepared by melt-extruding and casting polyethylene terephthalate chips having an inherent viscosity of 0.65dl/g and 50ppm (based on the weight of the whole polyethylene terephthalate) of silica particles having an average particle diameter of 2.7 μm. Then, after coating the acrylic water dispersible resin composition on both surfaces of the sheet by a bar coating method (surface hardness after drying is 2H), the temperature was raised to 110 to 150 ℃ at a rate of 1 ℃/sec, and the coated sheet was stretched 3.5 times in the Transverse Direction (TD) by preheating and drying. Then, heat treatment was performed in a 5-stage tenter (5-stage stretcher) at 230 ℃, and the heat-treated film was heat-set at 200 ℃ with 10% relaxation in the longitudinal and transverse directions, thereby preparing a biaxially stretched film having a thickness of 125 μm and both surfaces coated with an undercoat layer having a thickness of 20 nm.

[ example 2]Preparation of high-hardness polyester film having excellent oligomer retardation

A sheet was prepared by melt-extruding and casting polyethylene terephthalate chips having an inherent viscosity of 0.65dl/g and 50ppm (based on the weight of the whole polyethylene terephthalate) of silica particles having an average particle diameter of 2.7 μm. Then, after coating the acrylic water dispersible resin composition on both surfaces of the sheet by a bar coating method (surface hardness after drying is 2H), the temperature was raised to 110 to 150 ℃ at a rate of 1 ℃/sec, and the coated sheet was stretched 3.5 times in the Transverse Direction (TD) by preheating and drying. Then, heat treatment was performed in a 5-stage tenter at 230 ℃, and the heat-treated film was heat-set at 200 ℃ with 10% relaxation in the longitudinal and transverse directions, thereby preparing a biaxially stretched film having a thickness of 125 μm and both surfaces coated with an undercoat layer having a thickness of 80 nm.

[ example 3]Preparation of high-hardness polyester film having excellent oligomer retardation

A sheet was prepared by melt-extruding and casting polyethylene terephthalate chips having an inherent viscosity of 0.65dl/g and 50ppm (based on the weight of the whole polyethylene terephthalate) of silica particles having an average particle diameter of 2.7 μm. Then, after coating the acrylic water dispersible resin composition on both surfaces of the sheet by a bar coating method (surface hardness after drying is 2H), the temperature was raised to 110 to 150 ℃ at a rate of 1 ℃/sec, and the coated sheet was stretched 3.5 times in the Transverse Direction (TD) by preheating and drying. Then, heat treatment was performed in a 5-stage tenter at 230 ℃, and the heat-treated film was heat-set at 200 ℃ with 10% relaxation in the longitudinal and transverse directions, thereby preparing a biaxially stretched film having a thickness of 125 μm and both surfaces coated with a primer layer having a thickness of 150 nm.

Comparative example 1

A sheet was prepared by melt-extruding and casting polyethylene terephthalate chips having an inherent viscosity of 0.65dl/g and 50ppm (based on the weight of the whole polyethylene terephthalate) of silica particles having an average particle diameter of 2.7 μm. Then, after coating the acrylic water dispersible resin composition on both surfaces of the sheet by a bar coating method (surface hardness after drying is 2H), the temperature was raised to 110 to 150 ℃ at a rate of 1 ℃/sec, and the coated sheet was stretched 3.5 times in the Transverse Direction (TD) by preheating and drying. Then, heat treatment was performed in a 5-stage tenter at 230 ℃, and the heat-treated film was heat-set at 200 ℃ with 10% relaxation in the longitudinal and transverse directions, thereby preparing a biaxially stretched film having a thickness of 125 μm and both surfaces coated with a primer layer having a thickness of 10 nm.

Comparative example 2

A sheet was prepared by melt-extruding and casting polyethylene terephthalate chips having an inherent viscosity of 0.65dl/g and 50ppm (based on the weight of the whole polyethylene terephthalate) of silica particles having an average particle diameter of 2.7 μm. Then, after coating the acrylic water dispersible resin composition on both surfaces of the sheet by a bar coating method (surface hardness after drying is 2H), the temperature was raised to 110 to 150 ℃ at a rate of 1 ℃/sec, and the coated sheet was stretched 3.5 times in the Transverse Direction (TD) by preheating and drying. Then, heat treatment was performed in a 5-stage tenter at 230 ℃, and the heat-treated film was heat-set at 200 ℃ with 10% relaxation in the longitudinal and transverse directions, thereby preparing a biaxially stretched film having a thickness of 125 μm and both surfaces coated with a primer layer having a thickness of 300 nm.

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 were used.

2 wt% (solid content) of a binder and 0.3 wt% of a silicone-based wetting agent (BYK348, BYK CHEMIECCorp.) were added to water and stirred for 2 hours, thereby preparing a water-dispersible resin composition having a total solid content of 2.3 wt%.

Using the same method as in example 1, a biaxially oriented film having a thickness of 125 μm and both surfaces coated with an undercoat layer having a surface hardness of F was prepared using the prepared water-dispersed resin composition. The primer layer formed from the composition had a dry coating thickness of 80 nm.

Comparative example 4

An aqueous polyurethane adhesive having a solid content of 20 wt% was prepared by reacting 9 wt% of polyester-based polyol (polyethylene adipatediol having a weight average molecular weight of 1000), 10 wt% of hexamethylene diisocyanate, 1 wt% of a reactive emulsifier having an ionic group (Asahi Denka, adecia Soap, i.e., sulfonate of allyl glycidyl nonylphenol polyoxyethylene ether (SETM)), and 80 wt% of water with each other.

4 wt% (as a solid content) of the binder, 0.3 wt% of a silicone based wetting agent (BYK348, BYK CHEMIE Corp.) were added to water and stirred for 2 hours, thereby preparing a water dispersible resin composition having a total solid content of 4.3 wt%.

A biaxially oriented film having a thickness of 125 μm and both surfaces coated with an undercoat layer having a surface hardness of F was prepared by the same method as in example 1 using the prepared water-dispersed resin composition. The primer layer formed from the composition had a dry coating thickness of 80 nm.

Comparative example 5

4 wt% (as a solid content) of the binder, 0.3 wt% of a silicone-based wetting agent (BYK348, BYKCHEMIE Corp.) were added to water and stirred for 2 hours, thereby preparing a water-dispersed resin composition having a total solid content of 4.3 wt%.

A biaxially oriented film having a thickness of 125 μm and both surfaces coated with an undercoat layer having a surface hardness of F was prepared by the same method as in example 1 using the prepared water-dispersed resin composition. The primer layer formed from the composition had a dry coating thickness of 80 nm. Hard coatings having a surface hardness of 2H and a dried thickness of 3 μm were formed on both surfaces of the polyester film obtained as described above by an ultraviolet curing process, thereby preparing a double-sided hard coating film.

[ evaluation 1] evaluation of Pencil hardness and oligomer retardation Performance (haze Change ratio)

The pencil surface hardness of the polyester films prepared in examples and comparative examples was measured (JIS K-5600 standard). Further, after the polyester film was heat-treated at 150 ℃ for 60 minutes and left to stand for 5 minutes, haze values before and after the heat treatment were measured using a haze meter (Nippon Denshoku, Model NDH 5000).

[ Table 1]

As shown in table 1, in the films according to examples 1 to 3 of the present invention, the thickness of the undercoat layer was in the range of 20 to 150nm, and the surface hardness was secured at a 2H level. Therefore, it was confirmed from the results of the thin film according to the present invention that a separate hard coating layer was not required to be formed. In addition, the film satisfies desirable physical properties in terms of haze change rate (0.1% or less). This result means that the transparency is not deteriorated due to the migration of oligomers remaining in the PET film (substrate) to the surface during the post-processing process, including the heat treatment.

However, it was confirmed that in comparative example 1 (thickness of the undercoat layer is 10nm), it was difficult to secure a desired level of surface hardness. Further, it was confirmed that in comparative example 2 (the thickness of the undercoat layer was 300nm), desirable levels of surface hardness and haze change rate were secured, but the product could not be mass-produced due to the occurrence of coating stain and blocking phenomena. The generation of coating stains, which are very important control items among appearance control items of products, causes interference of light transmitted from the backlight unit to obstruct the transmission of light within the visual range of consumers. In addition, the blocking phenomenon (a phenomenon in which the primer layers on both surfaces of the product adhere to each other) occurs at the time of unwinding of the product, and thus the blocking phenomenon is one of important control items of consumers in terms of processability.

In addition, in comparative example 3 corresponding to a commonly used acrylic adhesive product, physical properties such as a haze change rate of 0.1% or less were secured, whereby an oligomer retardation property could be secured. However, it is difficult to secure a desired level of pencil hardness, and therefore, scratches and the like occur during a post-processing process, and thus a separate hard coating layer is required.

In comparative example 4, a general polyurethane base adhesive was used, which is advantageous for the adhesive force (tack) of the product, but the haze change value was raised to about 7%, and thus the transparency was deteriorated due to the oligomer, and the stability to heat and moisture was weak, similar to the polyurethane base adhesive according to the prior art, in view of blocking. The reason is that the oligomer migration retarding property cannot be achieved in the post-processing process, so the quality is continuously deteriorated due to the whitening phenomenon, and quality problems such as diamond patterns are generated during the cutting process.

Meanwhile, in comparative example 5 corresponding to a hard coat film prepared by forming hard coats on both surfaces of a double-sided base coated film, physical properties such as surface hardness, haze change rate, surface properties, and the like were satisfied. Therefore, when comparing the present invention with comparative example 5 in which a hard coating layer is formed, it can be confirmed that, according to the present invention, it is possible to simplify the process and achieve and improve the oligomer retardation performance structurally achieved in the method according to the prior art.

[ evaluation 2] evaluation of Performance by applying silver nanowire coating Process

A silver nanowire transparent electrode layer was coated on one surface of the polyester films prepared in examples and comparative examples, and adhesion between the undercoat layer and the transparent electrode layer and processability such as occurrence of scratch were verified.

[ Table 2]

As shown in table 2, it was confirmed that, in the films according to examples 1 to 3 of the present invention, the adhesive force with the transparent electrode layer was excellent, there was no problem in the occurrence of scratches, and thus the films were useful as novel base films for transparent electrodes. In addition, when comparing the present invention with comparative example 5 including a hard coating layer prepared by a method according to the prior art, there is no difference in the degree of occurrence of adhesion and scratch. Therefore, it was confirmed that all physical properties sufficiently 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 10nm, since the surface hardness was at the F level, it was difficult to control scratches in the nano silver coating process. In addition, in comparative example 3, it was confirmed that even if the haze change rate was appropriate, since the surface hardness of the existing undercoat layer was at the F level, it was difficult to control scratches in the production process, and thus the film could not be used as a base film for a transparent electrode. Therefore, it was confirmed that in the group of the commonly used acrylic adhesive products, it was difficult to achieve the required adhesive force of the substrate for the transparent electrode.

The exemplary embodiments of the present invention are described above, but the present invention may include various changes, modifications, and equivalents. It is to be understood that the present invention may be similarly applied by appropriately modifying the exemplary embodiments. Accordingly, the above summary is not intended to limit the invention, which is defined by the claims.

Claims

1. A polyester film comprising:

a base layer formed of a polyester resin; and

a primer layer laminated on both surfaces of the base layer and having a surface hardness of 2H or more,

wherein in the undercoat layer, the hardness is 2H or more, and the haze change rate (△ H) according to the following equation 1 is 0.1% or less,

wherein the film cut into a length x width of 1m x 1m is examined with a searchlight of CP-35NP1, POLARION Corp. to confirm whether or not stains are generated on the surface,

wherein the primer layer has a dry coating thickness of 20 to 150nm,

[ equation 1]

△H(％)＝Hf-Hi

In equation 1, Hf is the haze of the film after it is maintained at 150 ℃ for 60 minutes, Hi is the haze of the film before it is heated,

wherein the primer layer is formed by coating and drying an acrylic water dispersion resin composition,

wherein the base layer is formed of polyethylene terephthalate having an intrinsic viscosity of 0.5 to 1.0dl/g,

wherein the base layer contains any one or at least two inorganic particles selected from the group consisting of silica, kaolin and zeolite, and is contained in a range of 10ppm to 1000ppm based on the weight of the entire polyester resin.

2. The polyester film according to claim 1, wherein the primer layer is formed by an in-line coating method.

3. A transparent electrode film comprising a transparent electrode layer formed on the polyester film according to any one of claims 1 to 2.

4. The transparent electrode film according to claim 3, wherein the transparent electrode layer is made of a material selected from Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), zinc oxide (ZnO), and tin dioxide (SnO)₂) And a carbon nanotube, a silver nanowire, and a metal mesh.

5. The transparent electrode film according to claim 3, 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.