On the whole, inorganic materials have active applications in various fields including structural materials, coating materials for protection, and sealing (packaging) materials such as shielding and blocking films. This is, thanks to their excellent physical properties, inter alia, corrosion resistance, chemical resistance, wear resistance, heat resistance, hardness, and water and gas barrier properties. There is a strong need for expanding the application range of inorganic materials with such properties to electrical materials, electronic materials, information and energy materials, thus active research is ongoing.
Generally, inorganic materials require high-temperature and dry processes, which are high in unit cost, and are difficult to apply to the formation of thick films because of brittleness, and thus inorganic materials have many limitations in wet process applications. Further, the films to which the inorganic materials manufactured by a dry process are applied suffer from the disadvantage of having degraded packaging properties because of the presence of defects, such as pinholes, therein. In order to overcome the above limitations, research has recently been directed towards inorganic nano-sol in a colloidal phase, which allows for a wet process, and towards the dispersion of inorganic materials for use as wet materials.
A conventional inorganic nanosol, used as a structural material, has been used in binder mixture for the formation of films in a wet-coating process, with the aim of improving the films in terms of mechanical, thermal and chemical properties. However, the inorganic nanosol used as a structural material is too poor in purity to have applications in electrical, electronic, or information and energy fields. There is, therefore, a need for research into the development of inorganic nanosols of high purity while retaining the inorganic material's advantages, that is, high mechanical, thermal and chemical properties.
According to such a requirement, many methods for improving the purity of an inorganic nanosol have been proposed. Particularly, technologies for manufacturing a high-purity inorganic nanosol using metal alkoxide as a starting material have recently been developed.
The inorganic nanosol with high purity manufactured by these methods, can be used as electric and electronic, information, and energy materials, enjoying the advantage of allowing for a wet process because of its liquid phase. However, since it contains a solvent in a significant amount, a film coated with the nanosol may be prone to shrinkage during a drying and curing reaction, leading to degradation in dimensional stability, reproducibility and reliability. Thus, conventional inorganic nanosols are not suitable for use in passivation, molding, and terminal treatment, which require a wet material.
Further, in order to improve water and gas barrier capability which is an important physical property necessary for passivation, molding, terminal treatment or the like, it is required to control the shape, size and content of nanoparticles used in a coating film, and thus further research therefor is necessary.