Novel sealing technology for organic EL display and lighting by means of modified surface activated bonding method

Abstract

For a sealing of organic electro luminescence displays and lightings, a room temperature bonding of polymer films without organic adhesives is required. This paper describes a new bonding technique called modified surface activated bonding (mSAB) method using nano-adhesion layer that meets the requirement. Polymer films such as PEN, PET and PI can be bonded by this method. Especially PEN and PET films are so strongly bonded that the bond interface has tolerance for bending and loci of fracture after a peeling test are located in the polymer bulk. The organic electro luminescence lighting bonded by the proposed method clears environmental tests such as high temperature and high humidity tests. IntroductionOrganic electro-luminescent display (OELD) and lighting have attracted great interest because of their advantages such as thin profile, lightweight, and low driving voltage. However moisture and oxygen that may permeate the OLED cause detachment between the organic luminescent layer and the cathode electrode, cracking of the organic materials, and oxidation of the electrodes. Therefore, the commercial OELDs are made of glass substrate and the substrates are sealed by glass frit bonding. However increasing the size of the OELD, the process of glass frit bonding will be hardly adopted because of the brittleness of the glass sealing. The other potential applications of OELD are flexible displays and lightings, which are fabricated on polymer substrates. For those applications, polymer films with high gas barrier characteristics such as polyethylene naphthalate (PEN) have been developed. However there is no suitable adhesive for good sealing agent against permeation of water and oxygen from the atmosphere. Although a thermal compression bonding method realizes bonding without organic adhesives, polymer films and components of organic electronic are easily damaged at annealing process. Therefore, a new bonding technique of polymer films at room temperature without organic adhesives is required for the application of organic electronics.Surface activated bonding (SAB) method is a promising candidate for the room temperature bonding without organic adhesive [1]-[3] . In the SAB method, contamination and native oxide layer on the material surface are removed by Ar ion beam bombardment in an ultra-high vacuum (UHV) pressure. The activated surface becomes reactive to form chemical bond even at room temperature. It is reported that various materials can be bonded by SAB method, such as various metals [4], [5] and semiconductor materials [6], [7] at room temperature.

Microwave Bonding of Thin Polymer Substrates Using Carbon Nanotubes for Flexible Interconnections

“…To apply this method to polymers, a modified SAB ( m -SAB) was introduced that utilizes an additional coating of silicon nanofilms on the polymeric substrates . To cope with the intrinsic properties of the polymer substrates, such as surface roughness and thermal damage, the selection of the intermediate coating layers and plasma conditions should be carefully adjusted. − This process, however, requires high-end processes such as nanofilm sputtering, ultrahigh vacuum, and high-voltage plasma. − …”

Direct Bonding Method for Completely Cured Polyimide by Surface Activation and Wetting

“…Chen et al [ 17 ] bonded two pieces of polyimide films by heating at 250 °C for 60 min in an oven, finding that voids inevitably existed either at the bonding interface or within the bulk films. A modified surface activated bonding (mSAB) method was proposed to bond polyimides by a thin intermediate activated metallic layer, which is promising, although the metallic layer may cause short circuit and failure when through-silicon-via technology is involved [ 18 ]. So far, it is still challenging to develop a low-temperature bonding method for ordinary polyimide to meet the requirements of low thermal budget, high throughput, and reliability.…”

Direct Bonding Method for Completely Cured Polyimide by Surface Activation and Wetting

“…Chih Chen et al [17] bonded two pieces of polyimide films by heating at 250 °C for 60 min in an oven, finding that voids inevitably existed either at the bonding interface or within the bulk films. A modified surface activated bonding (mSAB) method was proposed to bond polyimides by a thin intermediate activated metallic layer, which is promising while the metallic layer may cause short circuit and failure when through-silicon-via technology is involved [18]. So far, it is still challenging to develop a low-temperature bonding method for ordinary polyimide to meet the requirements of low thermal budget, high throughput, and reliability.…”