Liquid crystal display having triangular ridges or elliptic projections for guiding light to a reflective film

• US 6,104,453 A
• Filed: 09/23/1998
• Issued: 08/15/2000
• Est. Priority Date: 09/30/1997
• Status: Expired due to Fees

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Watanabe, Tomoyuki
• Primary Examiner(s): MALINOWSKI, WALTER J
• Application Number:
  US09/159,250
• Time in Patent Office: 692 Days
• Field of Search: 349/64, 349/112, 349/63, 349/65, 349/113, 349/61, 362/26, 362/27, 362/31
• US Class Current: 349/61
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 2203/02 reflective

Abstract

A liquid crystal display has s a liquid crystal cell having a front surface serving as a viewing-side surface and a back surface, a reflecting film is attached to the back surface of the liquid crystal cell, and a light guide panel having a first major surface provided with minute irregularities and a second major surface finished in a smooth flat plane is disposed on the front surface of the liquid crystal cell with the second major surface thereof finished in a smooth flat plane in contact with the front surface of the liquid crystal cell. A light source is disposed beside a side surface of the light guide panel. When the liquid crystal display is used in a dim environment, the light source is turned on. Light emitted by the light source is guided and scattered toward the reflecting film by the light guide panel, so that the light can be transmitted efficiently by the light guide panel and the liquid crystal cell to the reflecting film.

Claims

1. A liquid crystal display comprising:

a liquid crystal cell having a front surface serving as a viewing-side surface, and a back surface;

a light guide panel having a first major surface provided with minute irregularities and a second major surface finished in a smooth flat plane, and disposed on the front surface of the liquid crystal cell with the second major surface thereof in contact with the front surface of the liquid crystal cell;

a light source disposed near the light guide panel such that light emitted from the light source is incident on the side surface of the light guide panel; and

a reflecting film attached to the back surface of the liquid crystal cell;

wherein the irregularities are ridges extended along lines substantially parallel to the side surface of the light guide panel and have a scalene triangular cross section in which a first interior angle, defined by a first side of the triangle disposed more proximate to the light source and a plane parallel to the second major surface of the light guide panel, is smaller than a second interior angle, defined by a second side of the triangle disposed distal to the light source and the lines; and

incident light from the light source is guided into the liquid crystal cell by the ridges, reflected by the reflecting film, travels though the light guide panel, and emerges outside the liquid crystal display.

2. The liquid crystal display according to claim 1, wherein the light source is disposed beside the side surface of the light guide panel, and the irregularities of the light guide panel are formed at a pitch in the range of 1 to 100 μ

m.

3. The liquid crystal display according to claim 1, wherein flat surfaces are formed between the adjacent ridges, respectively.

4. A liquid crystal display according to claim 1 wherein the first interior angle is between 2.5°

and 8° and

the second interior angle is between 45° and

50°

.

5. A liquid crystal display according to claim 1 wherein a height of the ridges gradually increases with distance from a ridge disposed closest to the light source.

6. A liquid crystal display comprising:

a liquid crystal cell having a front surface serving as a viewing-side surface, and a back surface;

a light guide panel having a first major surface provided with minute irregularities and a second major surface, and disposed on the front surface of the liquid crystal cell with the second major surface thereof finished in a smooth flat plane in contact with the front surface of the liquid crystal cell;

a light source disposed near the light guide panel such that light emitted from the light source is incident on the side surface of the light guide panel; and

a reflecting film attached to the back surface of the liquid crystal cell;

wherein the irregularities are elliptic projections having major axes and continuously connected along lines substantially parallel to the side surface of the light guide panel; and

incident light from the light source is guided into the liquid crystal cell by the elliptic projections, reflected by the reflecting film, travels though the light guide panel, and emerges outside the liquid crystal cell.

7. The liquid crystal display according to claim 6, wherein the elliptic projections are arranged with their major axes aligned with lines substantially parallel to the side surface of the light guide panel, and the length of the major axes of the elliptic projections is in the range of 1 to 100 μ

m.