Foldable display device

A foldable display device, comprising:

• a shell having an expanding state and a folding state, the shell comprising a first shell, a second shell and a third shell, the second shell pivoting on the first shell and being capable of rotating around a rotating axis relative to the first shell so as to have an expanding position and a folding position state, the third shell slidably coupled to the first shell and movably assembled with the first shell and having an approach position and an extension position;
• when the shell is located at the expanding state, the second shell is located at the expanding position, and the third shell is located at the extension position;
• when the shell is located at the folding state, the second shell is located at the folding position, and the third shell is located at the approach position;
• wherein, a first direction and a second direction are defined to be orthogonal, wherein the rotating axis is paralleling to the second direction;
• when the shell is at the expanding state, the shell has a first length L1 along the first direction and a second length L2 along the second direction, the ratio of the first length L1 to the second length L2 is between 1.3 and 2;
• when the shell is at the folding state, the shell has a third length L3 along the second direction and a fourth length L4 along the first direction, and the ratio of the third length L3 to the fourth length L4 is also between 1.3 and 2;
• and
• a flexible display having a main body section and an expandable section which are connected to each other, wherein the main body section is assembled with the second shell, the expandable section is movably assembled with the third shell, the third shell has an accommodating slot, wherein when the second shell is located at the folding position, the expandable section is disposed to the accommodating slot, when the second shell is located at the expanding position, the flexible display is stretched by the third shell and the second shell so as to drive the expandable section to move outward from the accommodating slot.