Methods and apparatus for vacuum thin film deposition

• US 20040011288A1
• Filed: 02/25/2003
• Published: 01/22/2004
• Est. Priority Date: 02/26/2002
• Status: Active Grant

• Current Assignee: Sion Power Corporation
• Original Assignee: Moltech Corporation
• Inventors: Affinito, John D.
• Granted Patent: US 7,112,351 B2
• Time in Patent Office: Days
• US Class Current: 118/718
• CPC Class Codes: B05D 1/60 Deposition of organic layers from vapour phase vapour phase deposition in general C23C14/00, C23C16/00
• CPC Class Codes: B05D 2252/02 of indefinite length
• CPC Class Codes: B05D 3/0493 using vacuum
• CPC Class Codes: B05D 3/067 Curing or cross-linking the coating
• CPC Class Codes: B05D 3/068 using ionising radiations (gamma, X, electrons)
• CPC Class Codes: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/366 as layered products
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The present invention provides a polymer coating method. In the method, in a vacuum chamber, a low temperature monomer evaporation chamber is used to heat a liquid monomer and a cooled substrate at a temperature lower than the liquid monomer reservoir or vapor. The liquid monomer is allowed to condense on the cooled substrate surface where it is polymerized by a radiation source. The process depends on the vapor pressure difference between liquid in the monomer source and liquid condensed on the surface of the cooled substrate. The film thickness is dependent on the temperature difference between the monomer reservoir and the substrate, and the time that is required to move the coated substrate from the evaporation chamber to the cure station. The method is suitable for forming very thin, uniform, pinhole-free, polymer coatings from a variety of monomers, having at least two olefinic groups per molecule, on a variety of substrates.

Claims

1. A method of forming a polymer coating on a surface of a substrate in a vacuum chamber evacuated to a pressure of less than about 10⁻

2 Torr, wherein the method comprises;

(a) heating a liquid monomer to form a vapor at a temperature below that at which thermal polymerization is initiated, wherein the monomer has two or more olefinic groups per molecule, and a vapor pressure in the range of 10<sup>−

6</sup> to 10<sup>−

1</sup> Torr at standard temperature and pressure;

(b) allowing the vapor to flow to the surface of the substrate, the surface at a temperature below the temperature of the liquid monomer or vapor;

(c) condensing the vapor on the surface of the substrate to deposit a monomer layer on the surface of the substrate; and

(d) polymerizing the monomer layer formed in step (c) to form the polymer coating on the surface of the substrate.

2. The method of claim 1, wherein step (a) further comprises forming the vapor in a heated chamber, the heated chamber comprising parallel sides and a gated aperture, the gated aperture adjustable to provide a cross-sectional area from 0 to 30% of the surface area of the liquid monomer in the heated chamber.

3. The method of claim 1, wherein step (a) further comprises heating the monomer to a temperature of less than about 80°

C. to form the vapor.

4. The method of claim 1, wherein the surface of the substrate is at a temperature of less than about 30°

C.

5. The method of claim 1, wherein the surface of the substrate is at a temperature of less than about 20°

C.

6. The method of claim 1, wherein the substrate is a web.

7. The method of claim 1, wherein the polymerization is induced by a radiation source.

8. The method of claim 7, wherein the radiation source comprising one or more of the group consisting of e-beam and ultraviolet radiation.

9. The method of claim 1, wherein the vapor pressure of the liquid monomer is from about 10⁻

2 to about 10<sup>−

4</sup> Torr at standard temperature and pressure.

10. The method of claim 1, wherein the molecular weight of the monomer is from about 150 to 800.

11. The method of claim 1, wherein the liquid monomer comprises one or more of the group consisting of glycol acrylates, polyglycol acrylates, and polyol polyacrylates.

12. The method of claim 1, wherein the liquid monomer is selected from the group consisting of hexanediol diacrylate, trimethylolpropane triacrylate, and tripropyleneglycol diacrylate.

13. The method of claim 1, wherein the coating formed in step (d) is from about 0.005 μ

m to about 10 μ

m in thickness.

14. The method of claim 1, wherein the coating formed in step (d) is from about 0.01 μ

m to about 1 μ

m in thickness.

15. The method of claim 7, wherein the substrate is a web moving past the radiation source.

16. A system for depositing a polymer coating onto a surface of a substrate in a vacuum chamber comprising:

an evaporation chamber operable to heat a liquid monomer contained within the evaporation chamber to a temperature below that at which thermal polymerization is initiated to generate a monomer vapor, the monomer vapor depositing on the surface of the substrate to form a deposited layer; and

a curing station coupled to the evaporation chamber, the curing station operable to expose the deposited layer to a source of radiation to induce polymerization to form the polymer coating on the substrate.

17. The system of claim 16 wherein the evaporation chamber comprises a gated aperture that can be adjusted to control the deposition of the monomer vapor onto the surface of the substrate.

18. The system of claim 16 wherein the substrate is a web and the system further comprising a rotating cooling drum, the rotating cooling drum transporting the substrate from the evaporation chamber to the curing system.

19. The system of claim 18 wherein the rotating cooling drum holds the substrate above a temperature below which the mobility of the deposited vapor monomer is too low to permit polymerization.

20. The system of claim 16 wherein the radiation source comprises one or more of an e-beam, ultraviolet radiation and x-ray radiation.

21. The system of claim 16 wherein the substrate is a web and supplied by a supply spool to a cooling drum that moves the substrate from the evaporation chamber to the curing station to a take-up reel.

22. The system of claim 16 wherein the evaporation chamber comprising parallel sides and a gated aperture, the gated aperture adjustable to provide a cross-sectional area from 0 to 30% of the surface area of the liquid monomer in the heated chamber.

23. The system of claim 16, wherein the liquid monomer is heated to a temperature of less than about 80°

C. to form the monomer vapor.

24. The system of claim 16 wherein the surface of the substrate is at a temperature of less than about 30°

C.

25. The system of claim 16 wherein the surface of the substrate is at a temperature of less than about 20°

C.

26. The system of claim 16 wherein the liquid monomer has a vapor pressure from about 10⁻

6 to about 10<sup>−

1</sup> Torr at standard temperature and pressure.

27. The system of claim 16 wherein a molecular weight of the liquid monomer is from about 150 to 800.

28. The system of claim 16 wherein the liquid monomer comprises one or more of the group consisting of glycol acrylates, polyglycol acrylates, and polyol polyacrylates.

29. The system of claim 16 wherein the liquid monomer is selected from the group consisting of hexanediol diacrylate, trimethylolpropane triacrylate, and tripropyleneglycol diacrylate.

30. The system of claim 16 wherein the coating is from about 0.005 μ

m to about 10 μ

m in thickness.

31. The system of claim 16 wherein a second evaporation chamber and a second curing station are provided such that am additional polymer layer is deposited on the substrate.

32. A polymer coated substrate comprising:

a substrate having a first exposed surface,

a polymer coating formed on the first surface by;

(a) exposing the substrate to a vapor formed by heating a liquid monomer at a temperature below that at which thermal polymerization is initiated, wherein the liquid monomer has two or more olefinic groups per molecule, and a vapor pressure in the range of 10<sup>−

6</sup> to 10<sup>−

1</sup> Torr at standard temperature and pressure;

(b) allowing the vapor to flow to the surface of the substrate, the surface at a temperature below the temperature of the liquid monomer or vapor;

(c) condensing the vapor on the surface of the substrate to deposit a monomer layer on the surface of the substrate; and

(d) polymerizing the monomer layer formed in step (c) to form the polymer coating on the surface of the substrate.

33. The substrate of claim 32, wherein step (a) further comprises forming the vapor in a heated chamber, the heated chamber comprising parallel sides and a gated aperture, the gated aperture adjustable to provide a cross-sectional area from 0 to 30% of the surface area of the liquid monomer in the heated chamber.

34. The substrate of claim 32, wherein step (a) further comprises heating the monomer to a temperature of less than about 80°

C. to form the vapor.

35. The substrate of claim 32, wherein the surface of the substrate is at a temperature of less than about 30°

C.

36. The substrate of claim 32, wherein the surface of the substrate is at a temperature of less than about 20°

C.

37. The substrate of claim 32, wherein the substrate is a web.

38. The substrate of claim 32, wherein the polymerization is induced by a radiation source.

39. The substrate of claim 38, wherein the radiation source comprising one or more of the group consisting of e-beam and ultraviolet radiation.

40. The substrate of claim 32, wherein the vapor pressure of the liquid monomer is from about 10⁻

2 to about 10<sup>−

4</sup> Torr at standard temperature and pressure.

41. The substrate of claim 32, wherein the molecular weight of the monomer is from about 150 to 800.

42. The substrate of claim 32, wherein the liquid monomer comprises one or more of the group consisting of glycol acrylates, polyglycol acrylates, and polyol polyacrylates.

43. The substrate of claim 32, wherein the liquid monomer is selected from the group consisting of hexanediol diacrylate, trimethylolpropane triacrylate, and tripropyleneglycol diacrylate.

44. The substrate of claim 32, wherein the coating formed in step (d) is from about 0.005 μ

m to about 10 μ

m in thickness.

45. The substrate of claim 32, wherein the coating formed in step (d) is from about 0.01 μ

m to about 1 μ

m in thickness.

46. The substrate of claim 38, wherein the substrate is a web moving past the radiation source.

47. A method of forming a two-part coating on a substrate:

(a) sputtering a first layer on to the substrate;

(b) forming a second layer by;

(i) exposing the substrate to a vapor formed by heating a liquid monomer at a temperature below that at which thermal polymerization is initiated, wherein the liquid monomer has two or more olefinic groups per molecule, and a vapor pressure in the range of 10<sup>−

6</sup> to 10<sup>−

1</sup> Torr at standard temperature and pressure;

(ii) allowing the vapor to flow to the surface of the substrate, the surface at a temperature below the temperature of the liquid monomer or vapor;

(iii) condensing the vapor on the surface of the substrate to deposit a monomer layer on the surface of the substrate; and

(iv) polymerizing the monomer layer formed in step (c) to form the polymer coating on the surface of the substrate.

48. The method of claim 47 wherein steps (b) is performed prior to step (a).

49. The method of claim 47 wherein the first layer is a metal or metal oxide layer.

50. An anode for use in an electrochemical cell comprising:

(a) a polymer film layer having an exposed surface;

(b) a protective crosslinked polymer layer formed on the surface of the polymer film layer, the protective crosslinked polymer layer formed by;

(i) exposing the polymer film layer to a vapor formed by heating a liquid monomer at a temperature below that at which thermal polymerization is initiated, wherein the liquid monomer has two or more olefinic groups per molecule, and a vapor pressure in the range of 10<sup>−

6</sup> to 10<sup>−

1</sup> Torr at standard temperature and pressure;

(ii) allowing the vapor to flow to the surface of the polymer film layer, the surface at a temperature below the temperature of the liquid monomer or vapor;

(iii) condensing the vapor on the surface of the polymer film layer to deposit a monomer layer on the surface of the polymer film layer; and

(iv) polymerizing the monomer layer formed in step (c) to form the polymer coating on the surface of the polymer film layer, and

(c) an anode active layer formed over the protective crosslinked polymer layer, the anode active layer comprising lithium.

51. A battery comprising:

(a) a casing;

(b) one or more electrochemical cells in the casing, the electrochemical cells comprising;

(i) a cathode comprising a cathode active material;

(ii) an anode; and

(iii) a non-aqueous electrolyte interposed between the anode and the cathode, wherein the anode comprises;

(A) a polymer film layer having an exposed surface;

(B) a protective crosslinked polymer layer formed on the surface of the polymer film layer, the protective crosslinked polymer layer formed by;

(1) exposing the polymer film layer to a vapor formed by heating a liquid monomer at a temperature below that at which thermal polymerization is initiated, wherein the liquid monomer has two or more olefinic groups per molecule, and a vapor pressure in the range of 10<sup>−

6</sup> to 10<sup>−

1</sup> Torr at standard temperature and pressure;

(2) allowing the vapor to flow to the surface of the polymer film layer, the surface at a temperature below the temperature of the liquid monomer or vapor;

(3) condensing the vapor on the surface of the polymer film layer to deposit a monomer layer on the surface of the polymer film layer; and

(4) polymerizing the monomer layer formed in step (c) to form the polymer coating on the surface of the polymer film layer, and

(C) an anode active layer formed over the protective crosslinked polymer layer, the anode active layer comprising lithium.

52. An anode for use in an electrochemical cell comprising:

(a) an anode active layer comprising lithium metal;

(b) one or more polymer layers formed on a surface of the anode active layer, each polymer layer formed by;

(i) exposing the anode active layer to a vapor formed by heating a liquid monomer at a temperature below that at which thermal polymerization is initiated, wherein the liquid monomer has two or more olefinic groups per molecule, and a vapor pressure in the range of 10<sup>−

6</sup> to 10<sup>−

1</sup> Torr at standard temperature and pressure;

(ii) allowing the vapor to flow to the surface of the anode active layer, the surface at a temperature below the temperature of the liquid monomer or vapor;

(iii) condensing the vapor on the surface of the anode active layer to deposit a monomer layer on the surface of the polymer film layer; and

(iv) polymerizing the monomer layer formed in step (c) to form the polymer coating on the surface of the anode active layer.

53. A battery comprising:

(a) a casing;

(b) one or more electrochemical cells in the casing the electrochemical cells comprising;

(i) a cathode comprising a cathode active material;

(ii) an anode; and

(iii) a non-aqueous electrolyte interposed between the anode and the cathode, wherein the anode comprises;

(A) an anode active layer comprising lithium metal;

(B) one or more polymer layers formed on a surface of the anode active layer, each polymer layer formed by;

(1) exposing the anode active layer to a vapor formed by heating a liquid monomer at a temperature below that at which thermal polymerization is initiated, wherein the liquid monomer has two or more olefinic groups per molecule, and a vapor pressure in the range of 10<sup>−

6</sup> to 10<sup>−

1</sup> Torr at standard temperature and pressure;

(2) allowing the vapor to flow to the surface of the anode active layer, the surface at a temperature below the temperature of the liquid monomer or vapor;

(3) condensing the vapor on the surface of the anode active layer to deposit a monomer layer on the surface of the anode active layer; and

(4) polymerizing the monomer layer formed in step (c) to form the polymer coating on the surface of the anode active layer.