1. Field of the Invention
The present invention relates to a foldable display device, and more particularly, to a foldable display device having a junction between at least two display panels connected to each other which is not visibly noticeable.
2. Description of the Related Art
As mobile multimedia broadcasting services, such as, digital multimedia broadcasting, is increasingly being provided, the necessity of enlarging a display panel of a portable display device, such as, a compact mobile device (e.g., a mobile phone) or a portable multimedia player (“PMP”), is increasing. However, the enlargement of the display panel greatly decreases the portability of the portable display device.
To solve this problem, a foldable display device including two display panels 10a and 10b which are pivotally coupled to each other so that the foldable display device may be folded while being carried has been proposed, which is illustrated in FIG. 1. However, two pixels 12a and 12b located at junction parts of the display panels 10a and 10b, respectively, are separated by about 1 mm, so that a black stripe B appears between images displayed on the two display panels 10a and 10b. In order to minimize a thickness of the black stripe B, the distance between the pixels 12a and 12b at junction parts of the display panels 10a and 10b needs to be minimized. The thicknesses of barrier walls 11a and 11b for completely shielding the pixels within the display panels 10a and 10b from the outside hinder sufficient minimization of the distance between the pixels 12a and 12b. This problem not only occurs in portable foldable display devices but also in large-sized display devices that have large screens obtained by connecting a plurality of small display panels together.
To address this problem, a technique of providing a continuous image by removing a black stripe without reducing the distance between the pixels 12a and 12b installed on the junction parts of the display panels 10a and 10b has been proposed. FIG. 2 illustrates a conventional display device having two display panels between which there are no seams. Referring to FIG. 2, the display panels 20a and 20b are coupled to each other by a junction part 21. To optically compensate for the seam between the two display panels 20a and 20b, electrodes 25 near the junction part 21 are made smaller than electrodes 24 in the other parts. To magnify the images on the smaller electrodes 25, a convex optical lens 23 is installed over the smaller electrodes 25. On the other hand, a flat glass or optical lens 22 is installed over the larger electrodes 24. Backlight units 26a and 26b for illuminating the display panels 20a and 20b, respectively, may be designed so as to provide brighter light to the smaller electrodes 25 than to the larger electrodes 24.
However, because the conventional display device of FIG. 2 requires the extra optical lens 23, the number of components thereof increases, leading to increases in the manufacturing time and costs thereof. Also, if the curvatures of the optical lens 23 is not precisely designed, an image may be distorted due to, for example, aberration. In addition, the precision design of the optical lens 23 increases the manufacturing costs greatly. Moreover, it is difficult to design the backlight units 26a and 26b for providing brighter light to a specific area, namely, to the smaller electrodes 25 than to the larger electrodes 24, and the design of the backlight units also increases the manufacturing costs. Furthermore, the backlight units 26a and 26b can hardly control the brightness of the specific area with any precision.