Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2002-07-11
2004-08-31
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S090000, C522S096000, C522S081000, C522S109000, C522S110000, C522S113000, C522S114000, C522S120000, C522S181000, C427S508000, C427S510000, C427S512000
Reexamination Certificate
active
06784223
ABSTRACT:
TECHNICAL FIELD
The present invention relates to ultraviolet light (UV) curable compositions capable of producing a transparent conductive coating.
BACKGROUND OF THE INVENTION
UV radiation curable transparent conductive compositions are applied to a substrate through spraying, screen printing, dipping or brushing, thus forming a transparent conducting film or coating. Transparent conductive coatings transmit visible light while possessing electrical conductivity. Accordingly such coatings find application in automobiles, airplanes, etc. as electrodes for liquid crystal devices, exothermic resistors, and photosemiconductors.
UV curable conductive films offer advantages over typical heat curable films typically produced by chemical vapor deposition, sputtering, and sol-gelling. Heat curable compositions used for example in the sol-gel process require the use of organic solvents that contain a significant amount of volatile organic compounds (VOCs). These VOCs escape into the atmosphere while the heat curable composition dries. Such solvent based systems are undesirable because of the hazards and expenses associated with VOCs. The hazards include water and air pollution and the expenses include the cost of complying with strict government regulation on solvent emission levels. In contrast, UV curable compositions contain reactive monomers instead of solvents; thus eliminating the detrimental effects of the VOCs.
The use of heat curable compositions not only raises environmental concerns but other disadvantages exist with their use as well. Heat curable compositions suffer from slow cure times which lead to decreased productivity. These compositions require high energy for curing due to energy loss as well as the energy required to heat the substrate. Additionally, many heat curable compositions yield poor film properties that result in decreased value of the end product.
Although UV curable compositions exhibit superior properties and performance over their heat curable counterparts, UV curable compositions themselves suffer from certain disadvantages. Generally, UV compositions have high molecular weights and a substantial degree of cross linkage due to the highly reactive nature of the composition. As a result, many of these compositions suffer from low durability and resin shrinkage. With the use of many such compositions, an inordinately high amount of UV light is required to cure. With some compositions, suspended solids fall out of solution after a period of one to two days. This dispersion adversely affects the gloss and clarity of the finished product.
Accordingly, there exists a need to provide environmentally safe UV curable transparent conductive compositions which exhibit improved appearance and workability. Additionally, there is a need to provide a method of applying an improved composition which furthers the goal of improved performance.
SUMMARY OF INVENTION
It is an object of the present invention to provide an improved composition that upon curing by ultraviolet light produces a transparent conductive coating.
It is another object of the present invention to provide an improved composition suitable for use in touch screens, membrane switches, TV screens, and VCRs.
It is another object of the present invention to provide an improved composition suitable for coating a suitable substrate that can be applied by spraying, screen printing, dipping, and brushing.
It is still another object of the present invention to provide an improved composition that does not contain any significant amount of volatile organic solvents that do not become incorporated in the active layer after curing.
The present invention discloses an ultraviolet light curable transparent conductive composition and method for making such a composition that may be used to produce a transparent conductive coating on a suitable substrate. The disclosed composition does not contain any significant amount of volatile organic solvents that do not become incorporated in the active layer after curing. Specifically, the transparent conductive composition contains 5% or less volatile organic solvents by weight.
In accordance with one aspect of the invention, an ultraviolet light curable transparent conductive composition is provided. The transparent conductive composition comprises at least one aliphatic acrylated oligomer, an electrically conductive powder, and a photoinitiator. The aliphatic acrylated oligomer is present in an amount of about 10% to 40% of the total weight of the transparent conductive composition, the electrically conductive powder is present in an amount of about 20% to 50% of the transparent conductive composition, and the photoinitiator is present in an amount of 2% to 10% of the total weight of the transparent conductive composition. All percentages of the transparent conductive composition as expressed in this document refer to the mass percentage of the stated component to the total mass of the transparent conductive composition in its fluid state at standard temperature and pressure.
The transparent conductive composition preferably further comprises an acrylated epoxy oligomer in an amount of about 3% to 11%, an isobornyl acrylate monomer in an amount of about 10% to 40% of the transparent conductive composition, and a flow promoting agent in an amount of about 0.1% to 8% of the transparent conductive composition.
In accordance with yet another aspect of the invention, a method is provided for depositing a transparent conductive coating on a substrate. The method comprises a first step of applying to the substrate a transparent conductive fluid-phase composition (“transparent conductive composition”). The transparent conductive composition comprises a mixture of one or more aliphatic acrylated oligomers, an electrically conductive powder, and a photoinitiator. Preferably, the aliphatic acrylated oligomer is present in an amount of about 10% to 40% of the total weight of the transparent conductive composition, the electrically conductive powder is present in an amount of about 20% to 50% of the total weight of the transparent conductive composition, and the photoinitiator is present in an amount of about 2% to 10% of the total weight of the transparent conductive composition. The transparent conductive composition preferably further comprises an acrylated epoxy oligomer in an amount of about 3% to 11% of the total weight of the transparent conductive composition, an isobornyl acrylate monomer in an amount of about 10% to 40% of the total weight of the transparent conductive composition, and a flow promoting agent in an amount of about 0.1% to 8% of the total weight of the transparent conductive composition.
The method also includes a second step of illuminating the transparent conductive composition on the substrate with an ultraviolet light to cause the transparent conductive composition to cure into the transparent conductive coating.
In accordance with this method, the transparent conductive composition can be selectively deposited on the substrate at specific locations where transparent conductive plating is desired. It need not be applied to the entire substrate.
BEST MODE FOR CARRYING OUT THE INVENTION
Transparent Conductive Compositions
Reference will now be made in detail to presently preferred compositions or embodiments and methods of the invention, which constitute the best modes of practicing the invention presently known to the inventor.
In accordance with one aspect of the invention, a presently preferred ultraviolet light curable transparent conductive composition (“transparent conductive composition”) is provided. In this preferred embodiment, the transparent conductive composition includes a mixture of one or more aliphatic acrylated oligomers. The aliphatic acrylated oligomer mixture is present in an amount of about 10% to 40% of the total weight of the transparent conductive composition. The aliphatic acrylated oligomer mixture is more preferably present in an amount of about 20% to 30% of the total weight of the transparent conductive composition, and most prefera
Allied PhotoChemical, Inc.
Brooks & Kushman P.C.
McClendon Sanza L.
Seidleck James J.
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