Liquid crystal display device having an optimized ridged layer to improve luminosity

• US 5,550,657 A
• Filed: 09/10/1993
• Issued: 08/27/1996
• Est. Priority Date: 09/14/1992
• Status: Expired due to Term

• Current Assignee: Fujitsu Kasei Ltd. (Fujitsu Limited), Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Tanaka, Akira, Mesaki, Yoshinori, Sotokawa, Akio, Tomatsu, Masahiro, Kaiwa, Kazumasa
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Parker, Kenneth
• Application Number:
  US08/118,816
• Time in Patent Office: 1,082 Days
• Field of Search: 359/48, 359/49, 359/50, 359/42, 359/599, 359/69, 359/461, 362/26, 362/31, 362/330, 362/339, 40/546
• US Class Current: 349/62
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

A planar illumination unit includes an optical guide layer for guiding light therethrough and emitting the light from a top surface, a light source fixture provided so as to face a side wall of the optical guide layer for injecting a light into the optical guide layer, an optical scattering layer disposed above the top surface of the optical guide layer for causing a scattering in the light that has been received from the optical guide layer, and a reflector provided on a bottom surface of the optical guide layer for reflecting the light incident to the optical guide layer, wherein the light source fixture includes a reflector for reflecting the light that has been produced by a light source in a direction primarily offset from the light source.

Claims

1. A planar illumination unit, comprising:

an optical guide layer having first and second, mutually opposing principal surfaces, said optical guide layer being laterally defined by a side wall and guiding a light incident thereto at said side wall, said optical guide layer emitting said light from said first principal surface;

light source means, facing said side wall of said optical guide layer for injecting said light into said optical guide layer through said side wall, said light source means including first reflection means for reflecting said light produced by said light source means toward said side wall of said optical guide layer;

an optical scattering layer having first and second, mutually opposing principal surfaces, said optical scattering layer being disposed such that said second principal surface of said optical scattering layer faces said first principal surface of said optical guide layer thereby for receiving said light emitted from said first principal surface of said optical guide layer, said optical scattering layer causing scattering in said light that has been received from said optical guide layer and emitting said light from said first principal surface;

second reflection means, provided on said second principal surface of said optical guide layer, for reflecting a light incident to said second principal surface of said optical guide layer; and

directivity means having first and second opposing principal surfaces and provided on said first principal surface of said optical guide layer such that said second principal surface of said directivity means faces said first principal surface of said optical guide layer, said directivity means being disposed such that said first principal surface of said directivity means faces said second principal surface of said optical scattering layer, said directivity means carrying a plurality of ridges on said first principal surface so as to extend in parallel with each other, each of said plurality of ridges having an apex angle such that said plurality of ridges transmit an optical beam incident at any arbitrary angle to said second principal surface of said directivity means.

2. A planar illumination unit as claimed in claim 1, wherein said directivity means comprises a transparent film having first and second principal surfaces coincident to said first and second principal surfaces of said directivity means, respectively, said transparent film carrying, on said first principal surface thereof, said plurality of ridges extending parallel with each other.

3. A planar illumination unit as claimed in claim 2, wherein each of said plurality of ridges has an isosceles-triangular cross section, with said apex angle set to approximately 96°

.

4. A planar illumination unit comprising:

an optical guide layer having first and second, mutually opposing principal surfaces, said optical guide layer being laterally defined by a side wall and guiding a light incident thereto at said side wall, said optical guide layer emitting said light from said first principal surface;

light source means, facing said side wall of said optical guide layer for injecting said light into said optical guide layer through said side wall, said light source means including first reflection means for reflecting said light produced by said light source means toward said side wall of said optical guide layer;

an optical scattering layer having first and second, mutually opposing principal surfaces, said optical scattering layer being disposed such that said second principal surface of said optical scattering layer faces said first principal surface of said optical guide layer thereby for receiving said light emitted from said first principal surface of said optical guide layer, said optical scattering layer causing scattering in said light that has been received from said optical guide layer and emitting said light from said first principal surface;

second reflection means, provided on said second principal surface of said optical guide layer, for reflecting a light incident to said second principal surface of said optical guide layer; and

directivity means having first and second opposing principal surfaces and provided on said first principal surface of said optical guide layer such that said second principal surface of said directivity means faces said first principal surface of said optical guide layer, said directivity means being disposed such that said first principal surface of said directivity means faces said second principal surface of said optical scattering layer, said directivity means carrying a plurality of ridges on said first principal surface so as to extend in parallel with each other, said directivity means including a transparent film having first and second principal surfaces coincident to said first and second principal surfaces of said directivity means, respectively, said transparent film carrying, on said first principal surface thereof, said plurality of ridges extending parallel with each other, each of said plurality of ridges having a sawtooth cross section, with an apex angle set to approximately 48°

.

5. A liquid display panel, comprising:

a liquid crystal cell panel having first and second, mutually opposing surfaces, said liquid crystal cell panel including liquid crystal molecules therein; and

a planar illumination unit having first and second, mutually opposing principal surfaces and being disposed such that said first principal surface of said planar illumination unit faces said second principal surface of said liquid crystal cell panel, said planar illumination unit comprising;

an optical guide layer having first and second, mutually opposing principal surfaces, said optical guide layer being laterally defined by a side wall and guiding a light incident thereto at said side wall, said optical guide layer emitting said light from said first principal surface;

light source means, facing said side wall of said optical guide layer, for injecting said light into said optical guide layer through said side wall, said light source means including first reflection means for reflecting said light produced by said light source means toward said side wall of said optical guide layer;

an optical scattering layer having first and second, mutually opposing principal surfaces, said optical scattering layer being disposed such that said second principal surface of said optical scattering layer faces said first principal surface of said optical guide layer thereby for receiving said light emitted from said first principal surface of said optical guide layer, said optical scattering layer causing scattering in said light received from said optical guide layer and emitting said light from said first principal surface;

second reflection means, provided on said second principal surface of said optical guide layer, for reflecting a light incident to said second principal surface of said optical guide layer; and

directivity means having first and second opposing principal surfaces and provided on said first principal surface of said optical guide layer such that said second principal surface of said directivity means faces said first principal surface of said optical guide layer, said directivity means being disposed such that said first principal surface of said directivity means faces said second principal surface of said optical scattering means, said directivity means carrying a plurality of ridges on said first principal surface so as to extend in parallel with each other, each of said plurality of ridges having an apex angle such that said plurality of ridges transmit an optical beam incident at any arbitrary angle to said second principal surface of said directivity means.