Illuminator apparatus

• US 6,700,632 B2
• Filed: 01/18/2001
• Issued: 03/02/2004
• Est. Priority Date: 06/29/2000
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd., Nitto Denko Corporation
• Original Assignee: Hitachi, Ltd., Nitto Denko Corporation
• Inventors: Umemoto, Seiji, Ariyoshi, Toshihiko, Taniguchi, Hitoshi, Hira, Yasuo
• Primary Examiner(s): Chowdhury, Tarifur R.
• Assistant Examiner(s): AKKAPEDDI, PRASAD R
• Application Number:
  US09/761,733
• Publication Number:
  US 20020021384A1
• Time in Patent Office: 1,139 Days
• Field of Search: 349/61, 349/63, 361/26, 361/31, 361/330, 359/49, 359/63, 385/146, 385/901, 362/31, 362/26, 362/330
• US Class Current: 349/65
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

To provide a reflection type liquid-crystal display device having an illuminator in front of the liquid-crystal display device, the illuminator having a light guide plate superior in light utilization efficiency, dots constituted by a plurality of small recess or protrusion portions for reflecting the light incident on the light guide plate toward the liquid-crystal display device are formed in or on a surface of the light guide plate which does not face the liquid-crystal display device. Each of the dots is set to have a substantially V-shape in section, the sectional inclination angle of the V-shape is set in a range of from 35 to 43°, and the sectional vertex angle of the V-shape is in a range of 70.6±2.5°.

Claims

1. A front-lighting illuminator, comprising:

a front light guide plate; and

a light source disposed on one of side surfaces of said front light guide plate;

wherein said front light guide plate includes an incidence surface on which light from said light source is incident, and two light transmission surfaces, said incident light being made to exit from one of said two transmission surfaces thereof and to enter a liquid-crystal cell through a front surface thereof which is disposed behind said front light guide plate; and

wherein a plurality of dots each constituted by a small recess or protrusion portion for reflecting said light from said incidence surface toward said one light transmission surface are formed in or on another surface of said two light transmission surfaces of said front light guide plate opposite to said one light transmission surface, each of said dots being substantially rectangular in plan view and being substantially V-shape in section with a vertex angle of about 70.6°

±

2.5°

, and an inclination angle of said section being in a range of from 35°

to 43°

so as to enable an increase of light quantity exiting from said front light guide plate and entering said liquid crystal cell.

3. A front-lighting illuminator according to claim 1, wherein:

each of said dots has a short-side length in a range of from 0.002 to 0.05 mm and a long-side length in a range of from 0.002 to 0.2 mm.

4. A front-lighting illuminator according to claim 1, wherein:

said dots are disposed at random in or on the other surface of said light guide plate opposite to said light transmission surface.

2. A front-lighting illuminator disposed on a front surface of a liquid-crystal cell, comprising:

a front light guide plate; and

a light source disposed on one of side surfaces of said front light guide plate;

wherein said front light guide plate includes an incidence surface on which light from said light source is incident, and two light transmission surfaces, said incident light being made to exit from one of said two transmission surfaces of said front light guide plate and to enter said liquid-crystal cell through the front surface thereof; and

wherein a plurality of dots each constituted by a small recess or protrusion portion for reflecting said light from said incidence surface toward said one light transmission surface are formed in or on another surface of said two transmission surfaces of said light guide plate opposite to said one light transmission surface, each of said dots being substantially rectangular in plan view and being substantially V-shape in section with a vertex angle of about 70.6°

±

2.5°

, an inclination angle of said section being in a range of from 35°

to 43°

, an area not smaller than 95% of a whole area of the surface where said dots are formed is sectioned into 0.25 to 1 mm² square areas, and said dots are disposed in each of said square areas so that a function G(R) which is obtained by taking a weighted average of a radial distribution function g(R) obtained for each of said dots in accordance with an arrangement relationship of said dots and which is obtained by approximating said weighted average by a least squares method satisfies a relation of 0<

S₁/S₂<

0.2 in a range of R/R₀ =3 to 6 so as to enable an increase of light quantity exiting from said front light guide plate entering said liquid-crystal cell;

provided that R designates a distance from a central position of one dot to a central position of another dot;

R₀, a value obtained by dividing a length of one side of said square area by a square root of the number of said dots existing in said square area;

S₁, a value obtained by integrating a difference between G(R) and an average value of G(R) with R/R0 which is in a range of from 3 to 6; and

S₂, a value obtained by integrating said average value of G(R) with R/R₀ which is in a range of from 3 to 6.

5. A front-lighting illuminator according to claim 2, wherein:

each of said dots is disposed so that said function G(R) is substantially 0 in a range of R<

(short-side length of said dot)X2, at least two peaks exist in said function G(R), and said two peaks each of which said two peaks is at least twice as large as said average value of said function G(R) exist in a range of R/R₀ =3 to 6.