Directional diffusing film

• US 6,505,959 B2
• Filed: 04/23/2001
• Issued: 01/14/2003
• Est. Priority Date: 04/27/2000
• Status: Active Grant

• Current Assignee: Dai Nippon Printing Company Limited
• Original Assignee: Dai Nippon Printing Company Limited
• Inventors: Arakawa, Fumihiro, Masaki, Tadahiro
• Primary Examiner(s): O'Shea, Sandra
• Assistant Examiner(s): Lee, Guiyoung
• Application Number:
  US09/839,691
• Publication Number:
  US 20010046134A1
• Time in Patent Office: 631 Days
• Field of Search: 362/26, 362/27, 362/31, 362/337, 362/339, 349/64, 349/112, 359/599, 359/621, 359/622, 359/623, 359/624, 264/467, 264/167
• US Class Current: 362/339
• CPC Class Codes: F21V 5/02 of prismatic shape F21V5/04 takes precedence
• CPC Class Codes: G02B 5/0215 the surface having a regular structure
• CPC Class Codes: G02B 5/0231 the surface having microprismatic or micropyramidal shape macroscopic prism arrays G02B5/045
• 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: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects

Abstract

A directional diffusing film of the invention includes a base film, and a plurality of convex directionality-providing elements regularly arranged on at least one surface of the base film. A section of a first directionality-providing element in a first plane including a top of the directionality-providing element has a shape of a substantially triangle, and a section of the directionality-providing element in a second plane including the top of the directionality-providing element and perpendicular to the first plane has a top of a second directionality-providing element and a shape of a continuous wave. The directional diffusing film having characteristics specified by the invention can diffuse light in proper directionally diffused light, while maintaining high light-diffusing ability. The directional diffusing film utilizes light highly efficiently as compared with conventional diffusing films.

Claims

1. A directional diffusing film comprising:

a base film, and

a plurality of convex directionality-providing elements regularly arranged on at least one surface of the base film;

wherein a section of a first directionality-providing element in a first plane including a top of the directionality-providing element has a substantially triangular shape, and

a section of the directionality-providing element in a second plane including the top of the directionality-providing element and perpendicular to the first plane has a top of a second directionality-providing element and a shape of a continuous wave.

2. A directional diffusing film according to claim 1, wherein the shape of the continuous wave is a periodic waveform having a period corresponding to each of the first and second directionality-providing elements.

3. A directional diffusing film according to claim 2, wherein the periodic waveform is a substantially sinusoidal waveform.

4. A directional diffusing film according to claim 1, wherein the shape of the continuous wave is a periodic waveform having wavy parts corresponding to the directionality-providing elements and straight parts respectively extending between the adjacent wavy parts.

5. A directional diffusing film according to claim 1, wherein the section of the first directionality-providing element in the first plane has a substantially isosceles triangular shape.

6. A directional diffusing film according to claim 1, wherein the substantially triangular shape has a vertex angle of a range of 80°

to 100°

.

7. A directional diffusing film according to claim 1, wherein the substantially triangular shape has a vertex which is rounded and/or a predetermined amount of which is cut off.

8. A directional diffusing film according to claim 1, wherein the plurality of convex directionality-providing elements are arranged on a light emitting surface of the base film so that incident light falling on the directional diffusing film at incident angles in a range of 70°

to 80°

leaves the directional diffusing film at outgoing angles including a maximum outgoing angle in a range of 25°

to 40°

.

9. A directional diffusing film according to claim 1 wherein the plurality of convex directionality-providing elements are arranged on a light emitting surface of the base film so that a haze value is in a range of 70 to 90 when light falls on a light receiving surface of the base film.

10. A surface light source unit comprising:

a light source,

a surface light emitting means having a light-emitting surface that can emit a light from the light source in a predetermined direction, and

a directional diffusing film that includes a base film, and a plurality of convex directionality-providing elements regularly arranged on at least one surface of the base film,

wherein a section of a first directionality-providing element in a first plane including a top of the directionality-providing element has a substantially triangular shape, and

a section of the directionality-providing element in a second plane including the top of the directionality-providing element and perpendicular to the first plane has a top of a second directionality-providing element and a shape of a continuous wave.

11. A liquid crystal display comprising:

a light source,

a surface light emitting means having a light-emitting surface that can emit a light from the light source in a predetermined direction,

a directional diffusing film that includes a base film, and a plurality of convex directionality-providing elements regularly arranged on at least one surface of the base film, and

a transparent liquid-crystal element arranged on a light-emitting side of the directional diffusing film,

wherein a section of a first directionality-providing element in a first plane including a top of the directionality-providing element has a substantially triangular shape, and

a section of the directionality-providing element in a second plane including the top of the directionality-providing element and perpendicular to the first plane has a top of a second directionality-providing element and a shape of a continuous wave.