Coatings with low permeation of gases and vapors
A multilayer structure has barrier properties for gases and vapors, for example oxygen and water vapor; the structure comprises: an organic substrate layer, and a multilayer permeation barrier thereon; the barrier comprises: a) a first inorganic coating contacting a surface of the substrate layer, and b) a first organic coating contacting a surface of the inorganic coating; the structure may be employed in a variety of articles where barrier properties are important especially in electronic articles such as organic light emitting diode devices where superior barrier characteristics over the life of the device are required.
1. An organic light emitting or photovoltaic device in which organic semi-conductors are encased in a barrier envelope, said envelope comprising a multilayer structure comprising:
i) an organic self-supporting substrate layer having a thickness of 50 μm to 5,000 μm, and
ii) a multilayer permeation barrier thereon, said barrier comprising:
a) a first inorganic coating contacting a surface of said substrate layer, said inorganic coating being impermeable to gases, when formed as a continuous coating but exhibiting discontinuity-controlled permeability through inadvertent discontinuities in the inorganic coating, said first inorganic coating having a thickness of 45 nm to 350 nm, and
b) a first organic coating contacting a surface of said first inorganic coating, said organic coating exhibiting diffusion controlled permeation of water vapor and oxygen.
2. A device according to claim 1 wherein said coatings a) and b) form a first permeation barrier of said mutilayer permeation barrier, and said multilayer permeation barrier further comprises at least one inorganic coating and at least one organic coating, in alternating relationship with said coatings of said first permeation barrier.
3. A device according to claim 1 wherein said coatings a) and b) form a first permeation barrier of said mutilayer permeation barrier, and said multilayer permeation barrier further comprises a first plurality of inorganic coatings and a second plurality of organic coatings, in alternating relationship, with an inorganic coating of said first plurality contacting coating b).
4. A device according to claim 1 wherein said organic coating has a thickness of 5 nm to 10 μm.
5. A device according to claim 1 wherein said organic coating has a thickness of 20 to 500 nm.
6. A device according to claim 2 , wherein each inorganic coating has a thickness of 45 to 350 nm.
7. A device according to claim 3 , wherein each organic coating has a thickness of 20 to 500 nm.
8. A multilayer structure according to claim 2 , wherein each organic coating has a thickness of 20 to 500 nm, and at least one organic coating of said second permeation barrier has a thickness greater than 1 μm up to 10 μm.
9. A device according to claim 1 , wherein said organic substrate has a thickness of 50 to 300 μm.
10. A device according to claim 9 , wherein the substrate is selected from the group consisting of:
a) single, multi-layer or coextruded plastic films;
b) plastic films having the surface modified by at least one of the following techniques: corona discharge treatment, low or atmospheric pressure glow discharge, flame treatment and heat treatment, and a radiation treatment wherein the radiation is selected from the group consisting of UV, VUV, X-rays, gamma-rays, and particle radiation;
c) plastic films having a surface coated with a functional coating selected from a hard-coating, an anti-scratch coating, an anti-abrasion coating, an anti-reflective coating, an anti-glare coating, a chemically-active coating, an oxygen scavenger coating, a desiccant coating, a UV-protective coating, and a colour-adjustment coating.
11. A device according to claim 10 wherein the or each inorganic coating is completely or essentially made of an inorganic material which is selected from the group consisting of SiO 2 , SiO x , SiO x C y , Si 3 N 4 , Si x N y C z , SiO x N y , TiO 2 , TiO x , ZrO 2 , ZrO x , Al 2 O 3 , SnO 2 , In 2 O 3 , ITO, PbO, PbO 2 , B 2 O 3 , P 2 O 5 , tantalum oxide, yttrium oxide, barium oxide, magnesium oxide, amorphous carbon, sulphur, selenium, magnesium fluoride, calcium fluoride, calcium oxide, mixtures thereof, or their alloys or compounds; wherein x represents an integer ranging from 1 to 3, y represents a number ranging from 0.01 to 5 and z represents a number ranging from 0.01 to 5.
12. A device according to claim 11 , wherein the or each organic coating is completely or essentially made of an organic material which is selected from the group consisting of plasma-deposited coatings obtained from mixtures containing at least one organic substance, gas or vapor at normal pressure, with or without contribution of inert or reactive gases, said organic substance being selected from: hydrocarbons, organic compounds containing one or more heteroatoms, alcohols, ethers, esters, or their combinations, organosilicon compounds, and organometallic compounds.
13. A device according to claim 1 , wherein the substrate is rigid.
14. A device according to claim 1 , wherein the substrate is flexible.
15. A device according to claim 1 , wherein the multilayer structure is transparent.
16. A device according to claim 1 , having an oxygen permeation, measured by ASTM methods F1927 and D3985 which is lower than 2 cm 3 /m 2 day.
17. A device according to claim 1 , having an oxygen permeation, measured by ASTM methods F1927 and D3985 which is lower than 0.01 cm 3 /m 2 day.
18. A device according to claim 1 , wherein said multilayer barrier has hardness of less than 2 GPa.
19. A device according to claim 1 , wherein said substrate has a smooth, flat surface in direct contact with said first inorganic coating.
20. An organic light emitting device in which light emitting diodes are encased in said barrier envelope, as defined in claim 1 .
21. A process for producing an organic light emitting or photovoltaic device comprising preparing a multilayer permeation barrier structure by:
i) depositing an inorganic material on an organic self-supporting substrate to form an inorganic coating in contact with a surface of said organic substrate, said substrate having a thickness of 50 μm to 5,000 μm, said formed inorganic coating having a thickness of 45 nm to 350 nm, said formed inorganic coating having inadvertent discontinuities such that said inorganic coating exhibits discontinuity-controlled permeability;
ii) depositing an organic coating on said inorganic coating, said organic coating exhibiting diffusion controlled permeation of water vapor and oxygen, and
iii) enveloping an organic semi-conductor for said device in an envelope which comprises said barrier structure.
22. A process according to claim 21 , wherein said depositing in i) is by PECVD, CVD, PVD, evaporation, reactive evaporation, sputtering, reactive sputtering, cathodic or anodic arc evaporation or wet chemical, in partial vacuum, or at or above atmospheric pressure; and said depositing in ii) is in partial vacuum, or at or above atmospheric pressure, using dip coating, spray coating, cast coating, sputtering, reactive sputtering, evaporation, reactive evaporation, PECVD, pyrolysis/condensation or pyrolysis/polymerization methods.
23. A process according to claim 21 , wherein the depositing of inorganic material is carried out by using PECVD or PVD, in partial vacuum; and the depositing of organic material is carried out using PECVD or pyrolysis/polymerisation method in partial vacuum.