This invention relates to a functional film obtained by laminating a plurality of layers and a method of manufacturing a functional film.
Gas barrier films obtained by forming a film with a gas barrier property on a base film such as a polyethylene terephthalate (PET) film are used as packaging materials for packaging portions or constituent parts, which require a moisture-proof property, in various kinds of devices such as optical devices, display devices including liquid crystal display devices or organic EL display devices, semiconductor devices, and thin-film solar cells, food, clothing, electronic components, and the like.
Films formed of various kinds of inorganic materials (inorganic compound), such as silicon nitride, silicon oxide, and aluminium oxide, are known as films with a gas barrier property formed in such a gas barrier film.
In addition, a laminated gas barrier film (gas barrier laminate) formed by laminating a plurality of layers, such as an organic layer (organic compound layer) and an inorganic layer (inorganic compound layer), in order to obtain the better gas barrier property is also known.
For example, JP 2009-269193 A discloses a method of manufacturing a laminate in which a coated layer is formed by applying application liquid containing a monomer or an oligomer on a base, a process of forming an organic layer by curing the coated layer is repeated, a lower layer including two or more organic layers is formed, and an inorganic layer is formed on the lower layer using a vacuum deposition method.
In the method disclosed in JP 2009-269193 A, the lower layer including two or more organic layers is formed on the surface of the substrate. Accordingly, since irregularities caused by foreign matter adhering to the substrate surface can be covered, the surface of the lower layer can be made smooth. As a result, since the occurrence of a defect in the inorganic layer formed on the lower layer is suppressed, it is possible to realize a gas barrier film with an excellent gas barrier property.
Moreover, in the gas barrier film in which an organic layer and an inorganic layer are laminated, the inorganic layer showing the gas barrier property is protected mainly by forming the organic layer on the inorganic layer. In addition, a plurality of organic layers and a plurality of inorganic layers may be laminated in order to obtain the better gas barrier property. That is, another organic layer may be further formed on the inorganic layer formed on the organic layer and another inorganic layer may be formed on the organic layer in order to obtain the better gas barrier property.
Here, functional films used in optical devices, display devices including liquid crystal display devices or organic EL display devices, and the like are required to have not only a gas barrier property but also an excellent light transmittance.
In the gas barrier film in which an organic layer and an inorganic layer are laminated, however, organic layers other than the organic layer formed on the base are formed with an inorganic layer as a base. Since there is a difference between the refractive index of an inorganic layer formed to obtain a gas barrier property and the refractive index of an organic layer, the reflectance at the interface between the inorganic layer and the organic layer increases and the light transmittance decreases accordingly.
In order to improve the gas barrier property, it is preferable to improve the smoothness by making an organic layer as a base of an inorganic film thick. However, if the organic layer is formed too thick, cracking or the like occur.