Front light, reflective liquid crystal display device and personal digital assistant

A reflective liquid crystal display device having a front light on a front side facing a viewer, said front light including

• a main optical guide plate;
• a second optical guide plate having a longitudinal direction extending along a widthwise direction of and at an end of said main optical guide plate, said second optical guide plate having a first end surface facing said main optical guide plate and a second end surface opposite the first end surface, the second end surface including a plurality of grooves extending in a depth direction, and lying along the longitudinal direction, respective prisms being formed by surfaces of said second optical guide plate located between each adjacent pair of said grooves;
• a point light source arranged at a longitudinal end of said second optical guide plate;
• and
• a reflective film coating a surface of said grooves.

A personal digital assistant provided with a reflective liquid crystal display device including a front light, said front light including

• a main optical guide plate;
• a second optical guide plate having a longitudinal direction extending along a widthwise direction of and at an end of said main optical guide plate, said second optical guide plate having a first end surface facing said main optical guide plate and a second end surface opposite the first end surface, the second end surface including a plurality of grooves extending in a depth direction, and lying along the longitudinal direction, respective prisms being formed by surfaces of said second optical guide plate located between each adjacent pair of said grooves;
• a point light source arranged at a longitudinal end of said second optical guide plate;
• and
• a reflective film coating a surface of said grooves.

An illumination device for a display device, the illumination device comprising:

• a display element;
• a main optical guide plate radiating light incident on said display element;
• a second optical guide plate having a longitudinal direction extending along a widthwise direction of and at an end of said main optical guide plate, said second optical guide plate having a longitudinal length no longer than 100 mm, having a first end surface facing said main optical guide plate, and a second end surface, the second end surface including a plurality of prism-shaped grooves extending in a depth direction and lying along the longitudinal direction;
• a point light source at a longitudinal end of said second optical guide plate;
• and
• a reflective film coating a surface of said grooves.

A front light arranged in front of a display device, comprising:

• a main optical guide plate;
• a second optical guide plate having a longitudinal direction extending along a widthwise direction of and at an end of said main optical guide plate, said second optical guide plate having a longitudinal direction no longer than 100 mm, having a first end surface facing said main optical guide plate, and a second end surface, the second end surface including a plurality of prism-shaped grooves extending in a depth direction and lying along the longitudinal direction;
• a point light source at a longitudinal end of said second optical guide plate;
• and
• a reflective film coating a surface of said grooves.