1. Field of the Invention
The invention generally relates to a photosensitive polysiloxane composition, a protecting film and an element having such protecting film, and more particularly, to a photosensitive polysiloxane composition used to form a protecting film with favorable cross-section shape and heat resistance, a protecting film with favorable cross-section shape and heat resistance, and an element having such protecting film.
2. Description of Related Art
In recent year, convention technology utilizes a method of increasing aperture ratio for enhancing finesses and resolutions of liquid crystal display (LCD) and organic electro-luminescence display (OELD). This method uses a transparent planarization film disposed on top of a thin-film transistor (TFT) as a protecting film, so as to enable data lines and pixel electrodes to overlap with each other, thereby achieving an aperture ratio higher than that of the traditional technology.
In general, a material of the planarization film must have high heat resistance, high transparency and high dielectric constant. Japanese Patent Publication No. 7-98502 discloses a composition containing novolac resin and quinone diazide compound. Japanese Patent Publication No. 10-153854 and Japanese Patent Publication No. 2001-281853 disclose a composition containing acrylic resins and quinone diazide compound. However, heat resistances of these materials are insufficient, and as the cured film is colored due to a high temperature treatment on the substrate, problems in transparency reduction would occur.
On the other hand, the conventional technology utilizes siloxane polymer as the material having high heat resistance, high transparency and high dielectric constant. In order to provide the siloxane polymer with photosensitivity, the quinone diazide compound is combined thereto. For instance, U.S. Patent Application Publication No. 2003-211407 discloses a composition combining siloxane polymer containing a phenolic hydroxyl group at one end with quinone diazide compound; Japanese Patent Publication No. 3-59667 discloses a composition combining siloxane polymer, which contains a phenolic hydroxyl group or a carboxyl group via a cycloaddition reaction, with quinone diazide compound. However, these compositions, due to having large amount of the quinone diazide compound or having the phenolic hydroxyl group in the siloxane polymer, are easily prone to problems such as coated film clouding or coloring during thermal curing. Moreover, it is to be noted that, these conventional compositions all face a problem of having poor cross-section shape, and thus are not conducive to the application.
It is desirable to develop a photosensitive composition capable of forming a protecting film with a favorable cross-section shape.