Light diffusing plate and lighting device using it

• US 7,878,690 B2
• Filed: 06/21/2006
• Issued: 02/01/2011
• Est. Priority Date: 06/24/2005
• Status: Expired due to Fees

• Current Assignee: Idemitsu Kosan Company Limited
• Original Assignee: Idemitsu Kosan Company Limited
• Inventors: Kogure, Masami, Kawato, Hiroshi
• Primary Examiner(s): Alavi; Ali
• Application Number:
  US11/993,500
• Publication Number:
  US 20100165619A1
• Time in Patent Office: 1,686 Days
• Field of Search: 362/97.1, 362/97.4, 362/217.02, 362/249.02, 362331-334
• US Class Current: 362/332
• CPC Class Codes: F21V 3/00 Globes; Bowls; Cover glasses with refracting properties F21V5/00; with reflecting properties F21V7/00; characterised by cooling arrangements F21V29/506
• CPC Class Codes: G02B 5/0215 the surface having a regular structure
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0268 characterized by the fabrication or manufacturing method
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity

Abstract

A light diffusing plate integrally formed with an optical element array on the front and rear surfaces thereof, and a direct lighting device having this light diffusing plate installed on a light reflection plate having a box type shape and provided therein with a light source, whereby a light diffusing plate and a thin direct lighting device are provided which eliminate luminance non-uniformity among a number of light sources (inter-light-sources distance) at a practical level (making luminance uniform), and realize higher luminance (delivering luminance equal to that when conventional prism sheets are laminated).

Claims

1. A light diffusing plate, comprising:

an optical element array integrally formed on front and rear surfaces of a light diffusing plate substrate to be mounted onto a direct lighting device,

wherein the optical element array comprises a microlens array which includes a lenticular lens array,

an arc at an end of the lenticular lens array formed on the front surface of the light diffusing plate substrate comprises ⅓

to ½

of a circle and an arc at the end of the lenticular lens array formed on the rear surface of the light diffusing plate substrate comprises 1/10 to ⅓

of a circle, and

a material constituting the light diffusing plate substrate comprises a transparent resin or a light diffusing resin composition having a total light transmittance of 75 to 96%.

2. A direct lighting device, wherein the light diffusing plate of claim 1 is mounted on a light reflecting plate having a box-like shape and incorporating light sources inside thereof.

3. The direct lighting device according to claim 2, wherein one or two or more of optical films are formed on the light diffusing plate.

4. The direct lighting device according to claim 3, wherein the optical film formed on the light diffusing plate comprises a light diffusing film having a total light transmittance of 80% or higher.

5. The direct lighting device according to claim 2, wherein the light reflecting plate has a wavy or parabolic cross-section.