Light diffusing sheet having a layer incorporated with light diffusing material and a layer with a corrugated surface

• US 6,002,464 A
• Filed: 05/07/1997
• Issued: 12/14/1999
• Est. Priority Date: 05/13/1996
• Status: Expired due to Term

• Current Assignee: Kuraray Company Limited
• Original Assignee: Kuraray Company Limited
• Inventors: Hayashi, Katsuhiko, Fujisawa, Katsuya, Watanabe, Rikuji, Ohnishi, Ikuo
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Horney, Kari M.
• Application Number:
  US08/853,179
• Time in Patent Office: 951 Days
• Field of Search: 349/112, 349/64, 359/453, 359/500, 359/599
• US Class Current: 349/112
• CPC Class Codes: G02B 5/0221 the surface having an irregular structure G02B5/0226 takes precedence
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• 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: G03B 21/60 characterised by the nature of the surface

Abstract

A light diffusing sheet including a clear film (#1) and two light diffusing layers (#2 and #3) formed consecutively thereon. The diffusing sheet is characterized in that the first light diffusing layer (#2) is a film of clear resin incorporated with a light-diffusing material, and the second light diffusing layer (#3) is a film of clear resin having a corrugated surface structure. The first light diffusing layer (#2) has a thickness of 10 μm to 500 μm and the light diffusing material has a weight concentration of less than 3%. The difference in refractive index between the clear resin and light diffusing material is 0.01 ≦ Δn ≦ 0.12, and the average particle diameter of the light diffusing material is between 4 μm to 30 μm.

Claims

1. A light-diffusing sheet, comprising:

a clear film;

a first light-diffusing layer formed on said clear film; and

a second light-diffusing layer formed on said first light-diffusing layer;

wherein the first light-diffusing layer is a film of clear resin having a light-diffusing material dispersed therein, the second light-diffusing layer is a film of clear resin having a corrugated surface configured to diffuse light in a single direction, said second light-diffusing layer being formed on said first light-diffusing layer, and

space="preserve" listing-type="equation">10 μ

m ≦

t ≦

500 μ

m

space="preserve" listing-type="equation">0.01 ≦

Δ

n ≦

0.12

space="preserve" listing-type="equation">3 wt % ≦

c

space="preserve" listing-type="equation">4 μ

m ≦

d ≦

30 μ

m

where t denotes the thickness of the first light-diffusing layer;

Δ

n denotes the difference between the refractive index of the light-diffusing material in the first light-diffusing layer and the refractive index of the clear resin of the first light-diffusing layer;

c denotes the concentration (by weight) of the light-diffusing material in the first light-diffusing layer; and

d denotes the average particle diameter of the light-diffusing material in the first light-diffusing layer.