An insulated glazing unit (1) comprising a base (13), a cross member (15) placed above the base (13), two upright members (14) for connection between the cross member (15) and the base (13), at least two at least partially transparent panes that are applied to the frame (12), wherein the at least two panes and the frame (12) define a closed volume (18), a light ray shielding device (2) placed in the closed volume (18), and comprising a plurality of slats (21) connected to each other and to a bottom member (22), support means attached to the cross member (15) and operably associated with the light ray shielding device (2) for support thereof, first guide means (24) located at the base (13) of the frame (12), second guide means (25) located on the bottom member (22) of the light ray shielding device (2). The insulated glass unit is characterized in that the bottom member (22) is configured to alternate between a first configuration in which the bottom member (22) is able to slide toward/away from the base (13) and a second configuration in which the bottom member (22) is placed proximate to the base (13) and is tilted with respect to a slide direction (X), the first (24) and the second guide means (25) are configured to contact each other when the light ray shielding device (2) is in the deployed position and to alternate the bottom member (22) from the first configuration to the second configuration thereby affording guided rotation of the bottom.