Optical sheet forming device and optical sheet forming method

An optical sheet forming device configured to form a light guide panel comprising a light entering portion and a surface emitting portion, upper surfaces of the respective light entering portion and surface emitting portion formed as flat surfaces arranged parallel to each other, an inclined surface formed between the upper surfaces, a lower surface of the light guide panel formed as a continuous flat surface opposed parallel to both the upper surfaces, the light entering portion formed as a thick portion, the surface emitting portion formed as a thin portion,

• the device comprising:
• an extruding unit including a T-die in which an ejecting slit configured to eject sheet-shaped molten resin is provided;
• and
• a forming roll unit including a main roll having a diameter, a pushing roll having a diameter equal to the diameter of the main roll, and a feed roll having a diameter equal to the diameter of the main roll, each of the main roll, the pushing roll, and the feed roll being configured to carry the ejected molten resin in an extrusion direction while solidifying the molten resin, the main roll and the pushing roll each respectively comprising a cylindrical transfer surface,
• the main roll including a thick portion forming groove provided to be continuously recessed in a circumferential direction on the transfer surface and to form the thick portion,
• the T-die including:
• a movable lip with a first lip provided at a distal end of the movable lip and a first slit surface on an opposed surface of the movable lip, the first slit surface including a recessed portion set to correspond to the thick portion forming groove,
• a fixed lip with a second lip provided at a distal end of the fixed lip and a second slit surface on an opposed surface of the fixed lip, wherein the first slit surface and the second slit surface are opposed parallel to each other to form the ejecting slit, and
• a lip gap adjusting mechanism provided at the movable lip and including lip adjusting bolts configured to adjust a lip gap between the first lip and the second lip, wherein one of the lip adjusting bolts is located at a position where the recessed portion is divided in half in a width direction of the ejecting slit, and
• the thick portion forming groove being formed in the center in the width direction of the main roll to simultaneously form two light guide plates or being formed on a side in the width direction of the main roll to form the light guide plate.