Ball spacers for LCD

At the outset of this project we identified a huge market for spacer technology in the production of Liquid Crystal Displays (LCDs). Every one of these devices from a mobile phone display to the latest 50 inch TV contain two glass sheets that must be accurately held parallel with one another at a distance of typically 4 micro meters. In this project we have developed a technology for placing very well defined polymer particles with precisely designed mechanical properties at locations on the glass screen that do not interfere with the passage of light through the screen. We have used a modification of inkjet printing to place the particles accurately and in an environmentally friendly process. Technically the project is successful. However, during the project we have however, discovered that spacer particle technology has several application areas that are closer to commercialization. Without leaving the original marketing concept, we have focused on other applications with less requirements for positioning accuracy. The result is that we have developed a concept for a leading spacer particle for use along the edge of the screen to define the thickness of the seal between the two glass sheets. The spacer particles we have developed are small (usually less than 4 microns in diameter), but have a complicated construction. They are built up of a core consisting of a polymer or metal, covered with one or several layers of polymer materials with different mechanical properties. We have patented this type of particle, as the same concept (with modified properties) is useful also as a component in the anisotropic conductive film.

The LCD industry is expecting a strong growth in the years to come. One critical element in the LCD manufacturing is the technology to provide a very uniform and controlled gap between the two glass plates in the display. Gap variations of less than 0.1 m icron across the display are enough to cause degradation of the optical quality. At the same time, it is important to avoid spacers in the optically active areas, as this will reduce the effective contrast ratio of the display. Today, a costly photo proce ss is used, utilizing large volumes of expensive photo-imaginable materials as well as costly equipment. Nevertheless, the gap variation obtained with this old technology do have an adverse effect on the optical performance of the display. In this project , Conpart is teaming up with some of the major industrial and R&D partners in the world. R&D challenges and activities will include modeling of the spacer particles in the display, development and characterization of the spacer particles, surface modific ations of the particles to comply with LCD requirements and microfluidic flow in the application process.