In recent years, there has been significant technological progress in the field of displays. In particular, the needs of the market have stimulated tremendous progress in the technology directed to increasing resolution and thinning displays.
In the next phase of this field, focus is placed on commercialization of flexible displays having a curved display area, and a variety of proposals have been made to increase the flexibility of displays (for example, see Patent Document 1). In addition, light-emitting devices using a flexible substrate can be lightweight compared to those using a substrate of usual thickness which is formed of glass or the like.
As methods for manufacturing a light-emitting device using a flexible substrate, the following proposals have been made: a method in which a light-emitting element and other elements are directly provided over a flexible substrate; a method in which a light-emitting element is formed over a glass substrate of usual thickness and then the substrate is subjected to polishing treatment or the like, so that the substrate is thinned to have flexibility or the substrate is removed and the light-emitting element is attached to a flexible substrate; a method in which a light-emitting element and other elements are formed over a glass substrate of usual thickness and then a layer having the light-emitting element and the other elements is separated from the substrate and transferred to a flexible substrate; and the like.
Nevertheless, over a substrate having sufficient flexibility, a light-emitting element and other elements are not easy to form with high precision. Therefore, over such a substrate, it is difficult to form light-emitting elements for their respective colors or to provide a color filter, much less to form a semiconductor element. Further, a light-emitting device using a thinned glass substrate can be said to lack sufficient flexibility. Even if a light-emitting device is formed by removal of a glass substrate, such a light-emitting device has a problem of low productivity. In contrast, the method for manufacturing a light-emitting device in which a separation step and a transfer step are utilized is relatively simple and easy and facilitates fabrication of a semiconductor element or formation of light-emitting elements for their respective colors. This method can also ensure sufficient flexibility, which shows great promise.