Two-layer transparent electrostatic charge dissipating coating

• US 20090074973A1
• Filed: 02/11/2008
• Published: 03/19/2009
• Est. Priority Date: 02/12/2007
• Status: Active Grant

• Current Assignee: Brewer Science Inc., Lumimove, Inc.
• Original Assignee: Brewer Science Inc., Lumimove, Inc.
• Inventors: Flaim, Tony D., Kinlen, Patrick J., Graham, Charles R.
• Granted Patent: US 7,749,603 B2
• Time in Patent Office: Days
• US Class Current: 427/331
• CPC Class Codes: H05K 9/0067 Devices for protecting against damage from electrostatic discharge
• CPC Class Codes: Y10T 428/265 1 mil or less
• CPC Class Codes: Y10T 428/31504 Composite [nonstructural laminate]
• CPC Class Codes: Y10T 428/31511 Of epoxy ether
• CPC Class Codes: Y10T 428/31551 Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]
• CPC Class Codes: Y10T 428/31855 Of addition polymer from unsaturated monomers

Abstract

A transparent two-layer electrostatic dissipating coating includes a first layer comprising a transparent first binder polymer and a first intrinsically conducting polymer (ICP) in an amount sufficient to provide the first layer with a surface resistance of from about 10³ to about 10⁵Ω/□; and a second layer in direct contact with the first layer and comprising a transparent second binder polymer and a second ICP in an amount sufficient to provide the second layer with a surface resistance of from about 10⁶ to about 10¹⁰Ω/□, wherein the coating has a light transmission of at least about 70% at a wavelength of 600 nm. Methods of making and using the coating are also described.

Claims

1. A transparent two-layer electrostatic dissipating coating comprising:

a first layer comprising a transparent first binder polymer and a first intrinsically conducting polymer (ICP) in an amount sufficient to provide the first layer with a surface resistance of from about 10³ to about 10⁵Ω

/□

; and

a second layer in direct contact with the first layer and comprising a transparent second binder polymer and a second ICP in an amount sufficient to provide the second layer with a surface resistance of from about 10⁶ to about 10¹⁰Ω

/□

,

wherein the coating has a light transmission of at least about 70% at a wavelength of 600 nm.

2. The coating according to claim 1, wherein the first binder polymer and the second binder polymer are water soluble or water dispersible prior to curing.

3. The coating according to claim 1, wherein the first layer has a thickness of from about 0.5 to about 2 microns.

4. The coating according to claim 1, wherein the first intrinsically conducting polymer comprises a polymer selected from the group consisting of polyaniline, polypyrrole, and polythiophene.

5. The coating according to claim 1, wherein the first intrinsically conducting polymer comprises poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate).

6. The coating according to claim 1, wherein the first binder is selected from a group consisting of a thermally cured polymer and a radiation cured polymer.

7. The coating according to claim 6, wherein the first binder polymer comprises a thermally cured self-crosslinking acrylic.

8. The coating according to claim 1, wherein the second layer has a thickness of from about 2 to about 10 microns.

9. The coating according to claim 1, wherein the second intrinsically conducting polymer comprises a polymer selected from the group consisting of polyaniline, polypyrrole, and polythiophene.

10. The coating according to claim 1, wherein the second intrinsically conducting polymer comprises poly(3,4-ethylened ioxythiophene) poly(styrene sulfonate).

11. The coating according to claim 4, wherein the second binder polymer comprises a material selected from the group consisting of UV-curable vinyl ether/cycloaliphatic epoxides and self-crosslinking acrylic resins.

12. The coating according to claim 1, wherein the second layer comprises a self-crosslinking acrylic resin, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), an acrylic polyurethane, and an ethoxylated trimethylolpropane triacrylate.

13. The coating according to claim 1, wherein the coating has a light transmission of at least about 85% at a wavelength of 600 nm.

14. The coating according to claim 1, wherein the thickness of the first layer plus the thickness of the second layer is between about 3 microns and 12 microns.

15. The coating according to claim 1, wherein the amount of the first ICP and the thickness of the first layer and the amount of the second ICP and the thickness of the second layer are designed to provide the coating with an ESD decay time of less than about 2 seconds.

16. The coating according to claim 15, comprising a first layer having a thickness of from about 0.2 microns to about 5 micron which includes from about 8% to about 20% of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) by weight in a polyurethane polyacrylate cobinder polymer;

and a second layer having a thickness of from about 2 microns to about 10 microns which includes from about 2% to about 12% of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) by weight in a polyurethane polyacrylate cobinder polymer.

17. The coating according to claim 15, comprising a first layer having a thickness of from about 0.5 microns to about 1 micron which includes from about 8% to about 12% of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) by weight in a polyurethane polyacrylate cobinder polymer;

and a second layer having a thickness of from about 5 microns to about 8 microns which includes from about 3% to about 5% of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) by weight in a polyurethane polyacrylate cobinder polymer.

18. The coating according to claim 17, wherein the light transmission at 800 nm of the coating is at least about 85%.

19. A method of making a transparent two-layer electrostatic dissipating coating on a surface of a substrate comprising:

forming on the surface a first layer comprising a transparent first binder polymer and a first intrinsically conducting polymer (ICP) in an amount sufficient to provide the first layer with a surface resistance of from about 10³ to about 10⁵Ω

/□

; and

forming a second layer on the first layer and in direct contact with the first layer and comprising a transparent second binder polymer and a second ICP in an amount sufficient to provide the second layer with a surface resistance of from about 10⁶ to about 10¹⁰Ω

/□

,

wherein the coating has a light transmission of at least about 70% at a wavelength of 600 nm.

20. The method according to claim 19, wherein the step of forming the first layer comprises

providing a first layer formulation comprising an aqueous dispersion of poly(ethylenedioxythiophene) poly(styrene sulfonate) and a transparent first binder polymer;

applying a continuous film of the first layer formulation to the surface; and

curing the first layer formulation to form a first layer having a thickness of from about 0.5 microns to about 1 micron and in which the poly(ethylenedioxythiophene) poly(styrene sulfonate) is present in an amount of between about 9% to about 15% by weight of the cured layer.

21. The method according to claim 19, wherein the step of forming the second layer comprises

providing a second layer formulation comprising an aqueous dispersion of poly(ethylenedioxythiophene) poly(styrene sulfonate) and a transparent second binder polymer;

applying a continuous film of the second layer formulation over the first layer; and

curing the second layer formulation to form a second layer having a thickness of from about 3 microns to about 5 microns and in which the poly(ethylenedioxythiophene) poly(styrene sulfonate) is present in an amount of between about 3% to about 10% by weight of the cured layer.

22. A method of dissipating electrostatic charge from a transparent substrate, the method comprising applying to a surface of the substrate a transparent two-layer electrostatic dissipating coating comprising:

a first layer comprising a transparent first binder polymer and a first intrinsically conducting polymer (ICP) in an amount sufficient to provide the first layer with a surface resistance of from about 10³ to about 10⁵Ω

/□

; and

a second layer in direct contact with the first layer and comprising a transparent second binder polymer and a second ICP in an amount sufficient to provide the second layer with a surface resistance of from about 10⁶ to about 10¹⁰Ω

/□

,

wherein the coating has a light transmission of at least about 70% at a wavelength of 600 nm.

23. A transparent substrate having protection against accumulation of electrostatic charge, comprising:

a surface of the substrate, to which is adhered a coating comprising;

a first layer comprising a transparent first binder polymer and a first intrinsically conducting polymer (ICP) in an amount sufficient to provide the first layer with a surface resistance of from about 10³ to about 10⁵Ω

/□

; and

a second layer in direct contact with the first layer and comprising a transparent second binder polymer and a second ICP in an amount sufficient to provide the second layer with a surface resistance of from about 10⁶ to about 10¹⁰Ω

/□

,

wherein the coating has a light transmission of at least about 70% at a wavelength of 600 nm.

24. The substrate according to claim 23, wherein the substrate is an aircraft canopy.