Alignment material baking

The phase separation producing opalescence and photosensitivity are production-created. That is, during the production of the glass, the phase separation occurs. The phase separation that occurs with pyroceramic material and Vycor requires baking the glass at high temperatures for an extended time. This elevated temperature provides the time for the molecules to align and/or separate themselves in a crystalline pattern. 

Japan Synthetic Rubber Corporation (JSR) was established for the domestic production of synthetic rubber in 1957, but entered the diversified businesses that utilize rubber raw materials fi-om around 1969. The first step was the development of a photosensitive material for semiconductors, and in search of new business, the LCD applications began to surface. Then the discussion started if it could be that new materials need to be synthesized for digital clocks, for example. LCDs at the time were TN-type monochrome displays, in which the alignment layer had to be heated to a high baking temperature of over 300 °C in order to transform the wholly aromatic polyamic acid precursor into polyimide. 

Wholly aromatic polyimide alignment films at that time needed a baking temperature of over 300 °C, but for color LCD applications it was necessary to make polydmide materials that can be cured at temperatures as low as 200 °C. hi response to this request, we in JSR started research and development of new alignment film materials from 1980. It was supposed that a soluble polyimide could be made a polydmide alignment film can be obtained by simply removing the solvent. 

First we needed to trace down if wholly aromatic polyimides existed that could be baked at lower temperatures. In the patent literature, the most used solvents to dissolve polyamic acids were cresols. By using certain cresol derivatives it was possible to form soluble polyimides from polyamic acids, and soluble polyimides were thus obtained and introduced to several LCD manufacturers that use these materials up to today. As a result (it will be regarded as obvious by now), the production of a prototype LCD, let alone the mass production of LCDs, would not have been possible without the disinfectant-like smell of cresol. The concept and the application to use soluble polyimide materials for low-temperature bakeable alignment films was not by mistake, but their research and development hit a big waU. 

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