BACKGROUND OF THE INVENTION

Field of the Invention

Embodiments in accordance with the present invention relate generally to a single component mass polymerizable polycycloolefin monomer compositions in combination with a latent organo-ruthenium compound, a photosensitizer, a pyridine compound and a compound capable of blocking the ultraviolet light. The compositions of this invention exhibit long storage stability at temperatures ranging from ambient temperature to 80° C. especially when stored in inert and dark atmosphere, and undergo mass polymerization only when subjected to suitable actinic radiation to form transparent optical layers having utility in a variety of opto-electronic applications including as 3D printing materials, encapsulants, coatings, and fillers. More specifically, this invention relates to single component stable compositions encompassing norbornene (NB) based olefinic monomers, which have high optical transparency and exhibit desirable properties for fabricating devices, such as optical sensors, light emitting diodes (LEDs), organic light emitting diodes (OLED), 3D printing materials, among other devices.

Description of the Art

Organic light emitting diodes (OLEDs) are gaining importance in a variety of applications, including flat panel televisions and other flexible displays, among other applications. However, conventional OLEDs, particularly, bottom emitting OLEDs suffer from a drawback in that only about half of the generated photons are emitted into the glass substrate out of which 25% are extracted into air. The other half of the photons are wave-guided and dissipated in the OLED stack. This loss of photons is primarily attributed to the refractive index (n) mismatch between the organic layers (n=1.7-1.9) and the glass substrate (n=1.5). By matching the refractive index of the substrate (n=1.8) and organic layers and augmenting the distance of the emission zone to the cathode to suppress plasmonic losses light extraction into the substrate can be increased to 80-90%. See, for example, G. Gaertner et al., Proc. Of SPIE, Vol. 6999, 69992T pp 1-12 (2008).

In addition, OLEDs also pose other challenges; in that OLEDs being organic materials, they are generally sensitive to moisture, oxygen, temperature, and other harsh conditions. Thus, it is imperative that OLEDs are protected from such harsh atmospheric conditions. See for example, U. S. Patent Application Publication No. US2012/0009393 A1.

In order to address some of the issues faced by the art, U.S. Pat. No. 8,263,235 discloses use of a light emitting layer formed from at least one organic light emitting material and an aliphatic compound not having an aromatic ring, and a refractive index of the light emitting from 1.4 to 1.6. The aliphatic compounds described therein are generally a variety of polyalkyl ethers, and the like, which are known to be unstable at high temperatures, see for example, Rodriguez et al., I & EC Product Research and Development, Vol. 1, No. 3, 206-210 (1962).

U.S. Pat. No. 9,944,818 discloses a two component mass polymerizable composition which is capable of tailoring to the desirable refractive index and is suitable as a filler and a protective coating material, thus potentially useful in the fabrication of a variety of OLED devices. Although this approach may provide certain advantages it still suffers from the drawback of being two component system and in addition organic polymers alone may not be able to provide required high refractive index for the OLED applications. Furthermore, there is also a need for mass polymerizable compositions which are stable at temperatures ranging from room temperatures up to 80° C. for several days such that the compositions can be stored at various operating conditions such as for example, vat 3D printing, where liquid compositions are stored in a 3D printer as well as OLED fabrication conditions, and yet the liquid composition polymerizes instantly when subjected to suitable photolytic conditions and/or higher temperatures. In addition, it has been observed that especially under 3D printing conditions the compositions stored in the vat may prematurely polymerize either due to air and/or exposure to light.

Accordingly, there is still a need for filler materials that complement the refractive index of OLEDs and yet exhibit high transparency and good thermal properties, among other desirable properties. In addition, it is desirable that such organic filler materials readily form a permanent protective coatings and are available as a single component composition for dispensing with such OLED layers or in a vat 3D printing operations.

Thus, it is an object of this invention to provide compositions that overcome the gaps faced by the art. More specifically, it is an object of this invention to provide a single component composition that will mass polymerize under the conditions of the fabrications of 3D printing and/or fabrications of an OLED device. It is further an object of this invention to provide stable single component mass polymerizable composition with no change in viscosity at or below normal storage conditions, including up to a temperature of about 80° C. but which undergoes mass polymerization only under the process conditions in which the 3D object or an OLED device is finally fabricated, such as for example by the use of radiation.

Other objects and further scope of the applicability of the present invention will become apparent from the detailed description that follows.

SUMMARY OF THE INVENTION

Surprisingly, it has now been found that by employing a single component composition, it is now possible to fabricate a 3D object or an OLED device having a transparent optical layer which features hitherto unachievable properties, i.e., refractive index in the range of 1.4 to 1.8 or higher, high colorless optical transparency, desirable film thickness of the filler layer typically in the range of 10 to 20 μm but can be tailored to lower or higher film thickness depending upon the intended application, compatible with the OLED stack, particularly the cathode layer (a very thin layer on the top of the OLED stack), compatible with polymerization of the formulation on the OLED stack, including fast polymerization time and can be photolytically treated, adhesion to both OLED stack and glass cover, and the like. It is also important to note that the compositions of this invention are expected to exhibit good uniform leveling across the OLED layer which typically requires a low viscosity. Further, compositions of this invention are also expected to exhibit low shrinkage due to their rigid polycycloolefinic structure. In addition, as the components of this invention undergo fast mass polymerization upon application they do not leave behind any fugitive small molecules which can damage the OLED stack. Generally, no other small molecule additives need to be employed thus offering additional advantages. Most importantly, the compositions of this invention are stable (i. e., no change in viscosity) at ambient atmospheric conditions including up to 80° C. for several hours to several days, especially when kept under inert conditions, and undergo mass polymerization only upon UV exposure. Most importantly, the compositions of this invention exhibit excellent shelf life stability in that the compositions of this invention retain their initial viscosity for several days, at least five to ten days.

Advantageously, the compositions of this invention are also compatible with a “one drop fill” (commonly known as “ODF”). In a typical ODF process, which is commonly used to fabricate a top emission OLED device, a special optical fluid is applied to enhance the transmission of light from the device to the top cover glass, and the fluid is dispensed by an ODF method. Although the method is known as ODF which can be misleading because several drops or lines of material are generally dispensed inside the seal lines. After applying the fluid, the fluid spreads out as the top glass is laminated, analogous to die-attach epoxy. This process is generally carried out under vacuum to prevent air entrapment. The present invention allows for a material of low viscosity which readily and uniformly coats the substrate with rapid flow in a short period of time. Even more advantageously, the present invention overcomes the deficiencies faced by the prior art in that a single component composition is much more convenient than employing a two component system especially in an ODF method. Furthermore the composition of the invention when used in accordance with the process conditions as provided herein provides more transparent 3D objects having good mechanical and thermal properties.

