WO2006080639A1

WO2006080639A1 - Uv curing type composition having high conductivity and superior anti-scratching

Info

Publication number: WO2006080639A1
Application number: PCT/KR2005/003171
Authority: WO
Inventors: Dong-Kyu Bae; I-Suk Cho; Koknara Bae
Original assignee: Dong-Kyu Bae; I-Suk Cho; Koknara Bae
Priority date: 2004-11-25
Filing date: 2005-09-23
Publication date: 2006-08-03
Also published as: KR100512687B1

Abstract

Disclosed herein is a composition for preparing conductive and scratch-resistant molded sheets, the composition comprising a polythiophene-based conductive polymer, a UV-oligomer and/or monomer, an organic solvent, a photoinitiator and a scratch-resistant additive. More particularly, the composition comprises 4-5.9% by weight of the polythiophene-based conductive polymer, 7-9.9% by weight of the UV-oligomer and/or monomer, 82-89% by weight of the organic solvent, 0.4-0.8% by weight of the photoinitiator, and 0.03-0.05% by weight of the scratch-resistant additive.

Description

UV CURING TYPE COMPOSITION HAVING HIGH CONDUCTIVITY AND SUPERIOR ANTI-SCRATCHING

Technical Field

The present invention relates to a UV-curable

composition which, when coated on a transparent plastic

polymer material , has high electrical conductivity, high

transparency and excellent scratch resistance . More

particularly, the present invention relates to a UV-curable

composition which comprises a polythiophene-based polymer

solution, a small amount of a UV-oligomer and/or monomer, an

organic solvent and ethoxylated silicone as a scratch-

resistant additive , and when formed into a coating film, has

a visible light transmittance of more than 96% , high

electrical conductivity corresponding to a surface resistance

of less than 10⁷ Ω/D, and excellent scratch resistance .

Background Art

Recently started to receive attention as an electrically conductive coating material on the glass surface

of cathode ray tubes is polyethylene dioxythiophene ( PEDT ) , a

polythiophene-based conductive polymer, as disclosed in US

patent Nos . 5 , 035 , 926 and 5, 391 , 472.

This conductive polymer has a characteristic in that it

shows excellent transparency as compared to other conductive

polymers, such as polyanilines , polypyrroles and

polythiophenes . This PEDT also has a characteristic in that

it is excellent in processability because it can use a

polymeric salt (e . g . , polystyrene sulfonate ) as a doping

material to prepare a water-dispersible coating solution .

Because of this water dispersibility, it is also excellent in

a mixing property with an organic solvent, and thus , can be

used as a coating material in various applications, including

cathode ray tube (CRT) glass and plastic film surfaces .

Furthermore, because it uses ether or alcohol as an organic

solvent , it is very advantageous in terms of environment .

A typical example of this water-dispersible PEDT is

BAYTRON PH commercially available from Bayer Corporation .

However, it is di fficult to achieve a surface

resistance of less than 10⁷ Ω/D by a general method, because a substrate is coated with a low concentration of PEDT in

order to maintain a high transparency of 96% although the

PEDT conductive polymer has excellent transparency.

Also, silicone oil or mineral oil is used as a scratch-

resistant material to increase film hardness, but its use

results in a reduction in conductivity, thus making it

further impossible to prepare a conductive film having a

surface resistance of less than 10⁷ Ω/D. For this reason, in

the prior art , it is used only in lower grade antistatic

coating materials requiring low conductivity .

Because of such disadvantages , it was impossible for

the prior art to realize an electromagnetic wave-shielding

material or high-performance antistatic coating material

which is commercially valuable and has a transmittance of

more than 96% , a surface resistance of less than 10⁷ Ω/D and

excellent scratch resistance .

Disclosure of Invention

Technical Problem

Accordingly, it is an obj ect of the present invention

to develop a composition for the preparation of PEDT conductive polymer thin films , which, when coated on a

plastic film, shows high electrical conductivity

corresponding to a surface resistance of less than 10⁷ Ω/O, a

high transmittance of more than 96% , and excellent scratch

resistance .

Another obj ect of the present invention is to determine

composition components satisfying said desired properties so

as to provide composition components and their composition

ratio, which reproducibly express the desired properties .

Namely, the present inventors have found that a reduction in

the content of binder solids in a composition led to a

visible light transmittance of more than 96% , the use of a

high concentration of PEDT conductive polymer and small

amounts of ethoxylated silicone and UV-oligomer and monomer

led to high electrical conductivity corresponding to a

surface resistance of less than 10⁷ Ω/D, and the addition of

a small amount of ethoxylated silicone resulted in an

increase in scratch resistance, thereby completing the

present invention .

Still another obj ect of the present invention is to

provide general molded sheet materials , such as films , panels and sheets .

Technical Solution

To achieve the above obj ects , the present invention

provides an electrically conductive and scratch-resistant UV-

curable composition, which comprises 4-5.9% by weight of a

polythiophene-based conductive polymer solution, 7-9.9% by

weight of a UV-oligomer and/or monomer, 82-88% by weight of a

solvent , 0.4-0.8% by weight of a photoinitiator and 0.02-

0.05% by weight of a scratch-resistant additive, and when

formed into a coating film, has a surface resistance of less

than 10⁷ Ω/D, a transmittance of more than 96% and a pencil

hardness of 4H or more .

For use, the inventive composition is coated on a

transparent film or sheet made of a plastic material, such as

polymethylmethacrylate, polycarbonate, polyethylene

terephthalate, amorphous polyethylene terephthalate,

polyethersulfone , polyvinyl chloride, MS resin ( copolymer of

MMA and SM) , or triacetate cellulose .

When the solution composition according to the present

invention is coated on a transparent substrate, such as glass or a synthetic resin film, a highly conductive and highly

transparent hard coating film will be obtained which has a

conductivity of less than 1 x 10⁶ to 9 x 10⁶ Ω/D, a

transmittance of more than 96% , and a hardness of 4H or more .

An example of the conductive polymer used in the

present invention is PEDT ( commercially available under the

trade name "BAYTRON PH" from Bayer Corporation) which is

doped with polystyrene sulfonate ( PSS) as a dopant so that it

shows good water solubility and is very excellent in thermal

and atmospheric stabilities . Also, to maintain the optimum

dispersibility of PEDT in water, the concentration of PSS

solids in PEDT is adj usted to 1.3% . Because PEDT is well

mixed with water, alcohol or a solvent with high dielectric

constant, it can be easily coated after dilution with this

solvent , and when formed into a coating film, shows excellent

transparency as compared to other conductive polymers, such

as polyanilines and polypyrroles .

The PEDT conductive polymer solution is preferably used

in an amount of 4-5.9% by weight . If it is used in an amount

of less than 4% by weight , it will be difficult to realize a

high conductivity of less than 10⁷ Ω/D because the amount of the conductive polymer to achieve conductivity will become

too low when the amounts of the organic solvent and the UV-

oligomer or monomer, which are additionally added, are fixed.

On the other hand, it is added in an amount of more than 5.9%

by weight , the transparency of the resulting composition will

decrease to less than 96% due to an increase in the amount of

the conductive polymer with coloring ability.

As the organic solvent for the PEDT conductive polymer

in the present invention, n-propyl alcohol , methyl cellosolve

(MCS ) , propyleneglycol methylether ( PM) and diacetone alcohol

( DAA) can be used alone or in a mixture of two or more

thereof . However, the most preferred organic solvent

allowing the maximum conductivity of the PEDT conductive

polymer to be exhibited is methyl cellosolve (MCS ) or

propyleneglycol methylether ( PM) , which is an organic solvent

having a methyl group .

It is not preferable in the present invention to use

methanol , ethanol , butyl acetate (BA) , ethyl acetate (EA) ,

isopropyl alcohol ( IPA) and ethyl cellosolve, conventional

solvents used in UV-curable resin compositions , because these

solvents very adversely affects the conductivity of the PEDT conductive polymer .

The organic solvent is preferably used in an amount of

82-88% by weight . If it is used in an amount of less than

82% by weight, it will lead to an increase in the amount of

other components in the resulting coating solution, i . e . , the

conductive polymer and the UV-oligomer and monomer, resulting

in a reduction in visible light transmittance and the

formation of high resistance . On the other hand, if it is

used in an amount of more than 88% , the visible light

transmittance of the resulting composition will be greatly

increased but the scratch resistance will not reach the

standard to be achieved by the present invention .

The UV-oligomer used in the present invention is a

urethane (meth) acrylate oligomer with a molecular weight of

less than 2 , 400. Oligomers with a molecular weight of more

than 2 , 400 are not preferred because they have poor

solubility and dispersibility. The urethane (meth) acrylate

oligomer is a conventional condensation product of isocynate

and diol , and any urethane (meth) acrylate oligomer can be

used in the present invention if it has a molecular weight of

less than 2 , 400. Among urethane (meth) acrylate oligomers with a molecular weight of more than 2 , 400 , a compound (U-

DPPA) of the following formula 1 , synthesized by the reaction

of dipentaerythritolpentaacrylate ( DPPA) of the following

formula 3 with an isocyanate trimer (general name : H-MDI ;

manufactured by Nippon Polyurethanes Co . ; product name :

CORONATE HX) of the following formula 2 , shows more excellent

physical properties . Also, the use of a mixture of U-DPPA

with a dipentaerythritolhexaacrylate monomer has a very good

result because it shows the remarkable effect of reducing

resistance value to 0.5 order .

NCO-(CH₂)6._NΛ_N,(CH₂)6-NCO

(CH₂)₆-NCO

1

Examples of the UV-curable monomer used in the present

invention include monofunctional and difunctional or higher

acrylate monomers and a mixture thereof . Examples of the

polyfunctional acrylate monomers include acrylate monomers of

polyol pentaerythritol and dipentaerythritol , such as

dipentaerythritolhexaacrylate ( DPHA) , and

hydroxyalkylacrylate, such as 2-hydroxyethylmethacrylate

(HEMA) . Examples of the monofunctional methacrylate monomers

include Ci-20 alkylester (meth) acrylates, such as

(meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate,

butyl (meth) acrylate, hexyl (meth) acrylate, octyl

(meth) acrylate and 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate,

and C₂-₄ hydroxyalkylester (meth) acrylates , such as 2-

hydroxyethyl (meth) acrylate and 2-hydroxypropyl

(meth) acrylate . These copolymerizable monomers can be used

alone or in a mixture of two or more thereof .

The UV-oligomer and/or monomer are preferably used in

an amount of 7-9.9% by weight . If they are used in an amount

of less than 7 % by weight , the resulting composition will

have weak hardness which leads to the occurrence of surface

scratches , and if they are used in an amount of more than

9.9% by weight , the surface resistance of the resulting

composition will increase to more than 10⁷ Ω/D.

Preferred examples of the photoinitiator used in the

present invention include α-hydroxycyclohexylphenylmethanone

(commercially available under the trade name "iRgAcure #184"

from Ciba Geigy) , l-hydroxycyclohexylphenylketone, 2-hydroxy-

2-methyl-l-phenyl propanone, hydroxymethylacetophenone and

benzophenone . More preferred is iRgAcure #184 because its

use allows resistance value to be reduced to 0.5 order as

compared to other photoinitiators .

The photoinitiator is used in an amount of 0.4-0.8% by weight . If it is used in an amount of less than 0.4% by

weight , the photopolymerization of the resulting composition

will become slow, and if it is used in an amount of more than

0.8 , the reaction rate will become fast but the surface

properties will deteriorate .

The scratch-resistant additive used in the present

invention is ethoxylated silicone ( commercially available

under the trade name "SiLWET" from GE SiLiCONES ) which does

not reduce the conductivity of the conductive polymer . Also,

in order to maintain surface resistance value at a level of

10⁶ Ω/D, the silicone additive must be added in the minimum

amount . When general silicone oil or mineral oil is used as

the scratch-resistant additive, the surface resistance of the

resulting composition will be lowered and cannot reach the

desired value . For this reason, the ethoxylated silicone

compound must be used in the present invention, and the use

of this compound will not result in a reduction in surface

resistance and will show a very excellent effect as compared

to other scratch-resistant additives .

The scratch-resistant additive is preferably used in an

amount of 0.02-0.05% by weight . If it is used in an amount of less than 0.02% by weight, it will lead to a reduction in

scratch resistance, and if it is used in an amount of more

than 0.05% by weight, it will cause a reduction in

conductivity.

The inventive composition with high conductivity and

high transparency, which contains the polythiophene

conductive polymer solution, is prepared by placing the PEDT

conductive polymer solution in a mixer, and adding the

organic solvent , the UV-oligomer and/or monomer, the

photoinitiator and the scratch-resistant additive at an

interval of about 1 minute with intense stirring, and

uniformly mixing these materials for 2-4 hours . The prepared

solution composition is poured on a transparent film made of

a plastic material , such as polymethylmethacrylate,

polycarbonate, polyethylene terephthalate, amorphous

polyethylene terephthalate, polyethersulfone, polyvinyl

chloride, or MS resin, and uniformly coated by bar coating,

spin coating, flow coating or dip coating, and then

maintained in a drying area having a transfer chain at a

temperature of about 60-90 ⁰C for 1-5 minutes so as to

completely evaporate water and solvent existing in the coating layer . Then, the resulting acrylic sheet is

irradiated with a UV dose of 400-1050 mJ/cm² so as to prepare

a transparent, highly conductive polymer film.

Best Mode for Carrying Out the Invention

Hereinafter, the present invention will be described in

more detail by examples and comparative examples . It is to

be understood, however, that these examples are given for

illustrative purpose only and are not construed to limit the

scope of the present invention . In the following examples ,

all percentages are by weight unless otherwise stated.

Examples

A coating film to be evaluated for physical properties

was prepared in the following manner . A mixed solution

prepared in each of Examples was flow-coated on the surface

of an acrylic sheet washed with alcohol . The coating film

was completely dried in an oven at about 70 ⁰C for 3 minutes

and cured by irradiation with a UV dose of 1000 mJ/cm² from a

UV lamp . The dried coating films all had a thickness of less

than 10 μm. The evaluation of physical properties for the highly

conductive acrylic sheets prepared as described above was

performed in the following manner .

Conductivity was evaluated by measuring surface

resistance using MONROE ELECTRONICS MODEL 292 , an ohm meter,

by the test method of ASTM D257.

Visible light transmittance was measured using a UV-

visible light spectrophotometer by the test method of ASTM

D1003.

Hardness was measured with a pencil hardness tester by

the method of ASTM D3502.

Scratch resistance was measured by the test method of

STEEL WOOL #0000 after running a load of 1 kg/cm² 100 times .

Scratches were rated on a scale of 1 to 5 , with "5" being no

occurrence of scratches and "1" being the occurrence of an

excessive amount of scratches .

Adhesion was measured by the method of ASTM D3359.

Compositions and property evaluation results for

Examples 1 to 4 (conductive polymer solution compositions

according to the present invention) and Comparative Examples

1 to 5 (polymer solution compositions out of the inventive composition range ) are shown Tables 1 and 2 below,

respectively .

(Table 1 )

^rl : ethoxylated silicone (commercially available under the trade name SILWET from GE SILICONES )

*2 : Irgacure #184

*3 : U-DPPA (commercially available under the trade name

"Oligo U-15HA" from New Nakamura, Japan)

As shown in Table 1 , compositions according to Examples

1 to 4 of the present invention and compositions according to

Comparative Examples 1 to 3 contain 5.9% by weight of a 1.3-

wt% PEDT aqueous solution (hereinafter, referred to as " PEDT

aqueous solution" ) , 0.75% by weight of iRgaACURE #184 as a

photoinitiator, and 0.02% by weight of ethoxylated silicone

as a scratch-resistant additive, and the component or content

of an UV-curable oligomer is contained in the inventive

polymer composition . In Examples 1 to 4 , as organic solvents ,

methyl cellosolve (MCS ) , PM, n-propylalcohol and DAA were

used alone or in a mixture of two or more thereof, and in

Comparative Examples 1 to 3 , a mixed solvent of EC and IPA

was used . Compositions of Comparative Examples 4 and 5

contain no scratch-resistant additive and are out of the

inventive composition range . Evaluation results for the

physical properties of coating films formed of the compositions of Examples 1 to 4 and Comparative Examples 1 to

5 are shown in Table 2 below .

(Table 2 )

As can be seen in Table 2 , Comparative Examples 1 to 3

with the use of a mixed solvent of EC and iPA, conventionally

used organic solvents , showed much higher resistance values

than those of Examples 1 to 4 with the use of MCS, PM, n-

propylalcohol , DAA (diacetone ethanol ) or a mixture thereof .

Also, Comparative Examples 4 and 5 having compositions out of

the inventive composition range showed significant reductions in conductivity, pencil hardness, scratch resistance and

transparency as compared to the inventive compositions of

Examples 1 to 4. Particularly in the case of Comparative

Example 4 , DPPA and U-DPPA as oligomers were used in an

amount of 20% by weight which is larger than that in the

inventive composition, and the conductive polymer was used in

an amount of 15% by weight which is much larger than that in

the inventive composition, but the composition of Comparative

Example 4 showed a much lower visible light transmittance

than that of the inventive compositions of Examples 1 to 4.

Accordingly, it could be seen that the inventive

conductive polymer solution compositions of Examples 1 to 4

maintained a transmittance of more than 96% , a hardness of 4H

or more and excellent scratch resistance and at the same time,

had high conductivity corresponding to a surface resistance

of less than 9 x 10⁶ Ω/D. On the other hand, in the

compositions of Comparative Examples 1 to 5 , which are out of

the inventive composition range, at least one property of

conductivity, transparency and scratch resistance was out of

a property range to be achieved by the present invention .

This indicates that the overall physical properties of Comparative Examples 1 to 5 are very inferior to those of the

inventive compositions .

Industrial Applicability

As described above, the conductive curable composition

according to the present invention contains the DHPA and U-

DPPA oligomers , the conductive polymer and the like . Thus ,

the inventive composition has an advantage in that it has

high hardness , high conductivity corresponding to a surface

resistance of less than 10⁷ Ω/D, and excellent scratch

resistance . Also, the inventive composition has an advantage

in that it can achieve high visible light transmittance

because the amount of use of binder solids is reduced,

leading to a reduction in the amount of the conductive

polymer .

Claims

What Is Claimed Is :

1. An electrically conductive and scratch-resistant UV-

curable composition comprising 4-5.9% by weight of a

polythiophene-based conductive polymer aqueous solution

having 1.3% by weight of solids , 7-9.9% by weight of a UV-

oligomer, 82-88% by weight of an organic solvent, 0.4-0.8 % by

weight of a photoinitiator and 0.02-0.05% by weight of a

scratch-resistant additive,

wherein the organic solvent is at least one selected

from the group consisting of n-propylalcohol, methyl

cellosolve, propyleneglycolmethylether, and diacetonealcohol ,

wherein the photoinitiator is at least one selected

from the group consisting of α-

hydroxycyclehexylphenylmethanone, 1-

hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenyl

propanone, hydroxymethylacetophenone, benzophenone and

benzoin, and

wherein the scratch-resistant additive is ethoxylated

silicone, and

wherein when formed into a coating film, the UV-curable composition has a hardness of 4H or more, a surface

resistance of less than 10⁷ Ω/D and a visible light

transmittance of more than 96% .

2. The UV-curable composition of Claim 1 , wherein the

UV-oligomer further contains a UV-curable monomer .

3. The UV-curable composition of Claim 2 , wherein the

UV-oligomer is selected from U-DPPA (an urethane

(meth) acrylate oligomer with a molecular weight of less than

2 , 400 ) , or a mixture of U-DPPA and DPHA.

4. The UV-curable composition of Claim 3 , wherein the

UV-oligomer is a mixture of U-DPPA and DPHA.

5. The UV-curable composition of Claim 1 , wherein the

photoinitiator is α-hydroxycyclehexylphenylmethanone .

6. The UV-curable composition of Claim 1 , wherein the

polythiophene-based polymer is doped with polystyrene

sulfonate ( PSS ) as a dopant .

7. An antistatic and scratch-resistant molded sheet

material prepared using a UV-curable composition as set forth

in any one of Claims 1 to 6.

8. An electrically conductive and scratch-resistant UV-

curable composition with conductivity and scratch resistance,

which comprises 4-5.9% by weight of a polythiophene-based

conductive polymer aqueous solution containing 1.3% by weight

of solids doped with polystyrene sulfonate, 7-9.9% by weight

of a mixture of U-DPPA and DPHA, 82-88% by weight of an

organic solvent, 0.4-0.8% by weight of α-

hydroxycyclehexylphenylmethanone as a photoinitiator, and

0.02-0.05% by weight of ethoxylated silicone as a scratch-

resistant additive, and when formed into a coating film, has

a hardness of 4H or more, a surface resistance of less than

10⁷ Ω/D and a visible light transmittance of more than 96% .

9. The UV-curable composition of Claim 8 , wherein the

organic solvent is selected from the group consisting of n-

propylalcohol , methyl cellosolve , propyleneglycolmethylether and diacetonealcohol .

10. An antistatic and scratch-resistant molded sheet

material prepared using a UV-curable composition as set forth

in Claim 8 or 9.