WO2010090422A1

WO2010090422A1 - Antifouling and antistatic polyester film

Info

Publication number: WO2010090422A1
Application number: PCT/KR2010/000612
Authority: WO
Inventors: Jong Ho Park; Jong Seul Lee; Jin Hwan Kim; Dae Gi Ryu
Original assignee: SKC Co Ltd
Current assignee: SKC Co Ltd
Priority date: 2009-02-03
Filing date: 2010-02-02
Publication date: 2010-08-12
Anticipated expiration: 2011-08-03
Also published as: KR101048893B1; KR20100089357A

Abstract

The present invention provides a polythiophene-based conductive polymer composition prepared by mixing an aqueous polythiophene-based conductive polymer solution, a binder, a fluorine-based antifouling compound, water and an aprotic highly-dipolar solvent at a predetermined component ratio, and an antifouling and antistatic polyester film formed using the composition, which has a surface resistance of 1 X 106 - 1 X 109 ?/sq and a water contact angle of 90º or more, the temporal change in the surface resistance of which at room temperature is small, and which has high moisture resistance, and a method of manufacturing the polyester film.

Description

ANTIFOULING AND ANTISTATIC POLYESTER FILM

The present invention relates to a polythiophene-based conductive polymer composition prepared by mixing an aqueous polythiophene-based conductive polymer solution, a binder, a fluorine-based antifouling compound, water and an aprotic highly-dipolar solvent at a predetermined component ratio, and an antifouling and antistatic polyester film formed using the same.

Currently, polyaniline (PAN), polypyrrol (PPy), polythiophene (PT) and the like are widely used as conductive polymer compounds.

It has been proposed that electrodes for secondary batteries, materials for blocking electromagnetic waves, flexible electrodes, antistatic materials, coating materials for anticorrosion, etc., can be prepared using the electrical characteristics of such conductive polymer compounds. However, they are not commercially available yet due to problems and difficulties in workability, thermal and atmospheric stability, moisture resistance, price, etc.

However, these conductive polymer compounds have lately attracted considerable attention as coating materials for the prevention of dust-sticking and static charge. Moreover, they have lately attracted considerable attention as coating materials for blocking electromagnetic waves in various electronic appliances by strictly controlling the standards for blocking electromagnetic waves.

In particular, as disclosed in U.S. Pat. Nos. 5,035,926 and 5,391,472, conductive polymers began to attract considerable attention as conductive coating materials for glass of cathode ray tubes (CRTs) from the time that polyethylene dioxythiophene (PEDT), which is a polythiophene-based conductive polymer, became highlighted. These conductive polymers have excellent transparency compared to other conductive polymers, such as polyaniline-based conductive polymers, polypyrrol-based conductive polymers, polythiophene-based conductive polymers, etc.

Conventionally, in order to improve the conductivity of polyethylene dioxythiophene (PEDT), polyethylene dioxythiophene (PEDT) was formed into a water-dispersible coating solution using a polymer acid salt, such as polystyrene sulfonate, as a doping material. This water-dispersible polyethylene dioxythiophene coating solution has been variously used as coating materials for glass of cathode ray tubes (CRTs), plastic film and the like because it is easily mixed with alcohol solvents and has excellent workability.

As a typical example of this water-dispersible polyethylene dioxythiophene, there is Baytron P which is manufactured by Bayer Corp. However, since this Baytron P is water dispersion and contains a SO₃ ^- group, it is weak to water even after it is formed into a polymer film. Therefore, its commercialization was not easy due to the great change in electrical characteristics of the polymer film when it was left alone for a long period of time or was exposed to high-humidity environmental conditions.

Referring to related conventional technologies, Korean Patent Application Publication No. 2000-10221 discloses a conductive polymer composition containing polyethylene dioxythiophene, an alcohol solvent, an amide solvent, a polyester resin binder, etc., and Korean Patent Application Publication No. 2005-66209 discloses a coating composition for a conductive light-diffusing film, containing polyethylene dioxythiophene, an alcohol solvent, an amide solvent, a silane coupling agent, etc.

In these conventional technologies, although the conductive polymer composition and the coating composition have a low surface resistance of 1 ㏀/㎡ or less and high transparency, adhesivity and durability, they cannot also be easily commercially used due to the great change in electrical characteristics of the conductive polymer film with the passage of time and the great change in electrical characteristics thereof under the condition of hot and humid environment.

Recently, a polyester film has been used as various base materials for displays or protective films because it has excellent durability and transparency. However, the polyester film has problems that it is easily contaminated by dust, foreign matters, etc. Therefore, in order to impart antistatic and antifouling properties to the polyester film, the following methods have been used.

Japanese Patent Application Publication No. H11-25615 discloses a method of forming an antistatic layer on a polyester film and then forming an antifouling layer on the antistatic layer, and Korean Patent Application Publication No. 2007-0071992 discloses a method of integrally forming an antistatic layer and an antifouling layer on a polyester film. In these methods, an antistatic agent dispersed in an organic solvent by an off-line coating process using a biaxially-stretched polyester film is used.

Further, Japanese Patent Application Publication No. 2000-026817 discloses a method of forming an antistatic layer using an antistatic agent used in a process of stretching a polyester film and then an antifouling layer by an off-line coating process, and Korean Patent Application Publication No. 2008-0055266 discloses a method of forming only an antistatic layer using polyaniline as a conductive polymer in a process of stretching a polyester film.

The methods of forming an antistatic layer and an antifouling layer on a biaxially-stretched polyester film by an off-line coating process has disadvantages that it is not environment-friendly due to the use of an organic solvent, it is not easily processed because both antistatic coating and antifouling coating must be performed, antistatic performance rapidly decreases with time when an antistatic layer and an antifouling layer are integrally formed, and an antistatic property changes depending on humidity and migrates to the surface of the polyester film when polymer salts are used.

Further, Korean Patent No. 813179 by the present inventors discloses an antifouling and antistatic polyester film formed using a coating composition including a polyester-based urethane resin, conductive polymer, an antifouling agent and a slipping agent. However, this antifouling and antistatic polyester film has a problem that its antistatic property deteriorates at room temperature and its appearance cannot be optically used.

Therefore, the present inventors have made efforts to solve the above-mentioned problems of the changes in material properties of an antistatic layer formed on a polyester film depending on environment, an off-line coating process which is not environment-friendly, a process that is inconvenient and requiring high costs. As a result, they found that, in a polythiophene-based conductive polymer composition prepared by mixing an aqueous polythiophene-based conductive polymer solution, a binder, a fluorine-based antifouling compound, water and an aprotic highly-dipolar solvent at a predetermined component ratio, the aprotic highly-dipolar solvent partially re-melts the polymer groups of the aqueous polythiophene-based conductive polymer solution to improve the connectivity and dispersity between polythiophene-based conductive polymers, and the binder increases the binding force between the composition and a polyurethane resin, so that an antistatic layer and an antifouling layer can be integrally formed in a process of biaxially stretching a polyester film, thereby realizing a polyester film having excellent durability. Based on these findings, the present invention was completed.

Accordingly, an object of the present invention is to provide a water-dispersible coating composition containing a conductive polymer, which can be used in a process of stretching a polyester film, and an antistatic film formed using the coating composition, which can exhibits excellent antistatic and antifouling properties regardless of the change in humidity and post-treatment.

The present invention provides a water-dispersible polythiophene-based conductive polymer composition having antifouling and antistatic properties, including: 1 - 30 wt% of an aqueous polythiophene-based conductive polymer solution; 1 - 30 wt% of two or more binders selected from the group consisting of a polyester resin, a polyurethane resin, isocyanate and alkxoysilane; 10 - 60 wt% of a fluorine-based antifouling compound; 30 - 65 wt% of water; and 1 - 20 wt% of an aprotic highly-dipolar solvent, and a polyester film formed using the same.

Hereinafter, the present invention will be described in detail.

The present invention provides a polythiophene-based conductive polymer composition prepared by mixing an aqueous polythiophene-based conductive polymer solution, a binder, a fluorine-based antifouling compound, water and an aprotic highly-dipolar solvent at a predetermined component ratio, a antifouling and antistatic polyester film formed using the composition through a biaxial stretching process, and a method of manufacturing the polyester film.

Concretely, the present invention provides a polythiophene-based conductive polymer composition, which does not require the use of a sulfonic acid group stabilizer for connecting polythiophene-based conductive polymers, whose surface resistance can be constantly maintained regardless of changes in external environment, which has an excellent antifouling property, high moisture resistance, strong adhesivity, excellent durability, high film uniformity and excellent stability to liquid, which has good physical appearance even after coating, and which can ensure material properties, because the composition is prepared by selectively mixing an aqueous polythiophene-based conductive polymer solution, a binder, a fluorine-based copolymer resin, water and an aprotic highly-dipolar solvent at a predetermined component ratio, wherein the aprotic highly-dipolar solvent partially re-melts the polymer groups of the aqueous polythiophene-based conductive polymer solution to improve the connectivity and dispersity between polythiophene-based conductive polymers, the fluorine-based antifouling compound containing fluorine in its side chains, and the binder is used to improve the binding force between the composition and a polyester substrate and the durability of a conductive film and is selected from the group consisting of a polyester resin, a polyurethane resin, isocyanate and alkoxysilane.

The antifouling and antistatic polyester film manufactured by applying the polythiophene-based conductive polymer composition onto one side or both sides of a polyester-based substrate and then laterally-stretching the polyester-based substrate coated with the composition and then thermally fixing the stretched polyester-based substrate coated with the composition has a surface resistance of 1 X 10⁶ - 1 X 10⁹ Ω/sq, an optical transmittance of 89% or more and a water contact angle of 90º or more, and the temporal change in the surface resistance thereof at room temperature and the change in the surface resistance thereof at constant temperature and humidity is maintained within a 10 fold difference. The total thickness of the polyester film may be 25 - 250 ㎛, and the coating thickness thereof may be 20 - 200 nm.

The components constituting the polythiophene-based conductive polymer composition of the present invention will be described in more detail as follows.

First, the aqueous polythiophene-based conductive polymer solution is not particularly limited as long as it is commonly used in a related field, but, in the present invention, polyethylenedioxythiophene (PEDT) (Baytron P, manufactured by Bayer Corp.) is used. Since the PEDT, which is a stabilizer (dopant), is doped with polystyrene sulfonate (PSS), it can be easily dissolved in water and has excellent thermal stability and atmospheric stability. Further, in order to optimally disperse the PEDT in water, the solid content of PEDT and PSS is adjusted in a range of 1.0 - 1.5 wt%. Due to the addition of the PEDT, the composition is easily mixed with water, alcohol or a solvent having a high dielectric constant, so that the composition can be easily applied on a substrate by diluting it with such a solvent, and the coating film formed using this composition exhibits excellent transparency compared to other conductive polymers, such as polyaniline, polypyrrol and the like.

The aqueous polythiophene-based conductive polymer solution is used in an amount of 1 - 30 wt%, preferably, 2 - 20 wt% based on the total amount of the conductive polymer composition.

In the present invention, it is preferred that a resin be used in the state of an aqueous solution as a binder for imparting moisture resistance, substrate adhesivity and durability because the PEDT conductive polymer solution itself is a water dispersion. Concretely, the binder for improving adhesivity and durability may be two or more selected from the group consisting of a polyester resin, a polyurethane resin, isocyanate and alkoxysilane. Further, since a polyester film is formed by coating a polyester substrate with a coating composition and laterally-stretching the polyester substrate coated with the coating composition 3 - 6 folds, it is preferred that a polyester resin and a polyurethane resin having a stretching ratio of 200 - 700%, more preferably, 350 - 550%. When the stretching ratio of the binder is less than 200%, the polyester film is cut during a stretching process, thus resulting in poor appearance. When the stretching ratio of the binder is more than 700%, the difference in stretching ratio between the binder and the polyester substrate is increased, thus being unable to improve the adhesivity and durability of the polyester film.

It is preferred that the alkoxysilane be methyltrimethoxysilane or tetraethoxysilane.

The binder is used in an amount of 1 - 30 wt%, preferably, 5 - 20 wt%. When the amount of the binder is less than 1 wt%, the adhesive force between the composition and the polyester substrate and the durability of a conductive film is deteriorated. When the amount thereof is more than 30 wt%, the conductivity of the polyester film is deteriorated.

The fluorine-based antifouling compound used in the present invention is used to prevent the adhering of pollutants and to easily remove the pollutants. The fluorine-based compound is not particularly limited but it includes those antifouling compounds commonly used in the related field. More specifically, the fluorine-based compound may be one or more selected from the group consisting of fluorine-based hydrocarbon compounds and fluorosilane coupling agents. The fluorine-based hydrocarbon compounds may include fluorine-containing acrylate resin copolymers. The fluorosilane coupling agents may be selected from the group consisting of trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, heptafluoropropyltrimethoxysilane, heptafluoropropylmethyldimethoxysilane. Further, because the conductive polymer is used in the state of water dispersion in the present invention, it is preferred that a water-dispersible fluorine-based compound be used. The fluorine-based copolymer resin is used in an amount of 10 - 60 wt% based on the total conductive polymer composition, preferably, 15 - 50 wt%. When the amount of the fluorine-based copolymer resin is less than 10 wt%, the contact angle is decreased. When the amount thereof is more than 60 wt%, stability to liquid is decreased, and surface resistance is increased.

The water used in the present invention may be used in an amount of 30 - 65 wt% based on the total conductive polymer composition. In the present invention, an aprotic highly-dipolar solvent is used together with water, thus improving the connectivity between conductive polymers and the dispersibility of PEDOT. That is, the aprotic highly-dipolar solvent, which is a polar solvent having hydrogen ions at end groups thereof, is directly bonded with SO₃ ^-of the PEDOT water dispersion without forming H₃O⁺when it is dissolved in water, so that the dispersibility of PEDOT is improved, thereby increasing conductivity.

The aprotic highly-dipolar (AHD) solvent may be selected from the group consisting of dimethylsulfoxide (DMSO), propylene carbonate (PC), ethylenglycol (EG) and the like. The aprotic highly-dipolar (AHD) solvent may be used in an amount of 1 - 20 wt%, preferably 4 - 18 wt%. When the amount of the aprotic highly-dipolar (AHD) solvent is less than 4 wt%, conductivity cannot be obtained. When the amount thereof is more than 18 wt%, boiling point is increased, and thus high-temperature calcination must be performed.

In addition, in order to prevent the blocking of the coated surface of the polyester film and improve the slipping thereof, an additive for improving slipping and leveling may be added in an amount of 0.05 - 5 parts by weight based on 100 parts by weight of the conductive polymer composition.

Meanwhile, methods of manufacturing the polyester film are not particularly limited. A biaxially-stretched polyester film is manufactured by applying the conductive polymer composition onto one side or both sides of a polyester-based substrate which was not primer-treated, laterally-stretching the polyester-based substrate coated with the conductive polymer composition 3 - 6 folds at 100 - 140℃ and then thermally-fixing the laterally-stretched polyester-based substrate coated with the conductive polymer composition at 220 - 240℃.

According to the present invention, the polyester film formed by coating a substrate with a polythiophene-based conductive polymer composition and then laterally-stretching the substrate coated with composition exhibits excellent antistatic and antifouling properties. Further, this polyester film has surface resistance which slightly changes with time at room temperature, is transparent, and has electrical characteristics which do not change at high temperature and high humidity. Therefore, this polyester film, which is used in the display industry, suppresses static electricity to prevent dust from adhering thereto, and has a high antifouling property to easily remove pollutants therefrom, so that the productivity and processibility of display materials can be improved, and can be practically used in various fields requiring transparency and antistatic and antifouling properties.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Example 1

6 wt% of a water-dispersible PEDOT (3,4-polyethylenedioxythiophene) solution as a conductive polymer, 3 wt% of a polyurethane resin having a stretching ratio of 400% and 6 wt% of isocyanate as a binder, and 20 wt% of a fluorine-based copolymer resin as an antifouling agent were mixed to form a mixture, and then 55 wt% of water and 10 wt% of ethyleneglycol were added to the mixture to prepare a water-dispersible coating composition having a solid content of 3 wt%.

The prepared coating composition was applied on a polyester sheet formed by melt extrusion, and then the polyester sheet coated with the composition was laterally stretched four folds, dried, cured and then thermally fixed at a temperature of 230 ℃ to manufacture an antistatic and antifouling polyester film having a total thickness of 188 ㎛.

Example 2

An antistatic and antifouling polyester film was manufactured in the same manner as in Example 1, except that 13 wt% of alkoxysilane was used as a binder.

Example 3

An antistatic and antifouling polyester film was manufactured in the same manner as in Example 1, except that 3 wt% of a polyester resin having a stretching ratio of 450 - 550% was used instead of the polyurethane resin having a stretching ratio of 400%.

Comparative Examples 1 - 3

Polyester films were manufactured in the same manner as in Example 1 according to the components and contents given in Table 1 below.

Comparative Example 4

A polyester film was manufactured in the same manner as in Korean Patent No. 813179.

Classification		Ex. 1	Ex. 2	Ex. 3	Comp. Ex. 1	Comp. Ex. 2	Comp. Ex. 3
Aqueous PEDOT solution ¹⁾		6	6	6	6	6	6
Binder	polyurethane resin ²⁾	3	3	-	-	3	3
	polyester resin ³⁾	-	-	3	-	-	-
	isocyanate	6	6	6	6	-	6
	alkoxysilane ⁴⁾	-	13	-	-	13	-
Antifouling agent	fluorine-based copolymer resin ⁵⁾	20	20	20	-	20	-
Antifouling agent	polysiloxane	-	-	-	20	-	20
Water		55	42	55	58	48	55
N-methylpyrrolidone		-	-	-	-	10	10
Aprotic highly-dipolar solvent	ethyleneglycol	10	10	10	10	-	-
Total		100	100	100	100	100	100
1) Baytron P, manufactured by Bayer Corp.2) R986, manufactured by DSM Corp.3) PU36, manufactured by Lamberti Corp.4) A-187, manufactured by Deku Corp.5) Modifier F600, manufactured by Nippon Oil&Fat Co., Ltd.

Test Example

[Evaluation method of material properties]

(1) Optical properties

The haze (%) and optical transmittance of the polyester film were measured using an XL 211 hazemeter manufactured by Gardener Corp.

(2) Surface resistance

The surface resistance (Ω/sq) of the polyester film was measured using a surface resistance meter (model name: 19782) manufactured by DESCO Corp. in U.S. under the conditions of a temperature of 23 ℃, a relative humidity of 30% and an applied voltage of 500 V.

(3) Water contact angle

Water drops were dropped onto the surfaces of the antistatic and antifouling polyester films manufactured in Examples and Comparative Examples at a room temperature and a relative humidity of 50%. After l minute, the contact angles of the polyester films to distilled water were measured using a contact angle meter (Phobnix 300, manufactured by SEO Corp.).

(4) Temporal change in surface resistance at room temperature

The antistatic and antifouling polyester films manufactured in Examples and Comparative Examples were left alone at room temperature, and then the changes in the surface resistance thereof were measured using the surface resistance meter (model name: 19782) manufactured by DESCO Corp. in U. S. according to the passage of time.

(5) Evaluation of surface resistance at constant temperature and humidity

The antistatic and antifouling polyester films manufactured in Examples and Comparative Examples were left alone at a temperature of 60℃ and a relative humidity of 90%, and then the changes in the surface resistance thereof were measured.

The results thereof are given in Table 2 below.

Classifi-cation	Optical transmittance (%)	Haze (%)	Contact angle (º)	Temporal change in surface resistance at room temperature (Ω/sq)		Change in surface resistance at constant temperature and humidity (RH 90%, 60℃)
Classifi-cation	Optical transmittance (%)	Haze (%)	Contact angle (º)	initial	440 hr	initial	440 hr
Ex. 1	89.93	2.66	100.6	6 X 10⁷	1.5 X 10⁸	3 X 10⁷	5 X 10⁷
Ex. 2	89.87	1.57	102.8	4 X 10⁷	8 X 10⁷	3.6 X 10⁷	4 X 10⁷
Ex. 3	89.78	1.50	94.6	1.5 X 10⁷	6 X 10⁷	2 X 10⁷	5 X 10⁷
Comp. Ex. 1	88.45	5.38	70.6	2 X 10¹⁰	5 X 10¹³	4 X 10¹⁰	6 X 10¹¹
Comp. Ex. 2	88.58	2.50	81.3	4 X 10⁹	6 X 10¹¹	4 X 10⁹	3 X 10¹⁰
Comp. Ex. 3	88.65	1.50	74.2	1 X 10⁹	9 X 10¹⁰	2 X 10⁹	1 X 10¹⁰
Comp. Ex. 4	88.90	3.40	95.0	2 X 10⁸	2 X 10¹¹	2.5 X 10⁸	5 X 10⁸

As given in Table 2, it can be seen that the antistatic and antifouling polyester films manufactured in Examples and Comparative Examples has a surface resistance of about 10⁷and a water contact angle of 90° or more, and, particularly, that their surface resistances hardly change at room temperature or at constant temperature and relative humidity according to the passage of time.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

A water-dispersible polythiophene-based conductive polymer composition having antifouling and antistatic properties, comprising:1 - 30 wt% of an aqueous polythiophene-based conductive polymer solution;1 - 30 wt% of two or more binders selected from the group consisting of a polyester resin, a polyurethane resin, isocyanate and alkxoysilane;10 - 60 wt% of a fluorine-based antifouling compound;30 - 65 wt% of water; and1 - 20 wt% of an aprotic highly-dipolar solvent.
The composition according to claim 1, wherein the alkoxysilane is methyltrimethoxysilane or tetraethoxysilane.
The composition according to claim 1, wherein the fluorine-based antifouling compound is one or more selected from the group consisting of fluorine-based hydrocarbon compounds and fluorine-based silane coupling agents.
The composition according to claim 1, wherein the aprotic highly-dipolar solvent is one or more selected from the group consisting of ethyleneglycol, dimethylsulfoxide and propylene carbonate.
An antifouling and antistatic polyester film formed using the composition of any one of claims 1 to 4.
The polyester film according to claim 5, wherein the polyester film has a surface resistance of 1 X 10⁶ - 1 X 10⁹ Ω/sq and a water contact angle of 90º or more, and the temporal change in the surface resistance thereof at room temperature and the change in the surface resistance thereof at constant temperature and humidity is maintained within a 10 fold difference.
The polyester film according to claim 5, wherein the polyester film has a total thickness of 25 - 250 ㎛.
The polyester film according to claim 5, wherein the polyester film has a coating thickness of 20 - 200 nm.
A method of manufacturing an antifouling and antistatic polyester film, comprising:applying the composition of any one of claims 1 to 4 onto one side or both sides of a polyester-based substrate which was not primer-treated; andlaterally-stretching the polyester-based substrate coated with the composition.