Surface light source device and asymmetrical prism sheet

A surface light source device comprising:

• a directional emission guide plate;
• a primary light-source to supply light to an incidence surface located at a side end of said guide plate;
• and
• an asymmetric prism sheet disposed along a front surface of said guide plate,
• wherein said asymmetric prism sheet has a prismatic inner face provided with a plurality of prism element rows running generally parallel to said incidence surface and an uneven outer face,
• the prism element rows of said prismatic inner face have an alternating first slope facing to said incidence surface and second slope facing opposite to said incidence surface,
• said first slope and said second slope have inclinations selected so that a main ray emitted from said guide plate is led into said asymmetric prism sheet through said first slope to be deflected toward a first generally frontal direction by way of internal reflection of said second slope while a secondary ray, which has been emitted from said guide plate with an emission angle greater than that of the main ray, is led into said asymmetric prism sheet through said first slope to be deflected toward a second generally frontal direction by way of internal reflection of said first slope following after internal reflection of the second slope, and
• an additional prism sheet is disposed outside of said asymmetric prism sheet and has an outer face and an inner face, with the outer face being provided with a plurality of prism element rows running generally perpendicular to said incidence surface, and the inner face being provided with a non-glare-processed face.

A surface light source device comprising:

• a directional emission guide plate;
• a primary light source to supply light to an incidence surface located at a side end of said guide plate;
• and
• an asymmetric prism sheet disposed along a front surface of said guide plate,
• wherein said asymmetric prism sheet has a prismatic inner face provided with a plurality of prism element rows running generally parallel to said incidence surface and an uneven outer face,
• the prism element rows of said prismatic inner face have an alternating first slope facing to said incidence surface and second slope facing opposite to said incidence surface,
• said first slope and said second slope have inclinations selected so that a main ray emitted from said guide plate is led into said asymmetric prism sheet through said first slope to be deflected toward a first generally frontal direction by way of internal reflection of said second slope while a secondary ray, which has been emitted from said guide plate with an emission angle greater than that of the main ray, is led into said asymmetric prism sheet through said first slope to be deflected toward a second generally frontal direction by way of internal reflection of said first slope following after internal reflection of the second slope, and
• a lens sheet is disposed outside of said asymmetric prism sheet and has an outer face and an inner face, with the outer face being provided with a plurality of lens element rows running generally perpendicular to said incidence surface, and the inner face being provided with a non-glare-processed face.

A surface light source device, comprising:

• a directional emission guide plate;
• a primary light source to supply light to an incidence surface located at a side end of said guide plate;
• and
• an asymmetric prism sheet disposed along a front surface of said guide plate,
• wherein said asymmetric prism sheet has a prismatic inner face provided with a plurality of prism element rows running generally parallel to said incidence surface and an uneven outer face,
• the prism element rows of said prismatic inner face is have an alternating first slope facing to said incidence surface and second slope facing opposite to said incidence surfaced,
• said first slope and said second slope have inclinations selected so that a main ray emitted from said guide plate is led into said asymmetric prism sheet through said first slope to be deflected toward a first generally frontal direction by way of internal reflection of said second slope while a secondary ray, which has been emitted from said guide plate with an emission angle greater than that of the main ray, is led into said asymmetric prism sheet through said first slope to be deflected toward a second generally frontal direction by way of internal reflection of said first slope following after internal reflection of the second slope, and
• a film is disposed outside of said asymmetric prism sheet, with at at least one face of the film having a mat face.