Uniform light directing film and method of making same

Patent metadata

Field	Value
Publication number	US-9164220-B2
Application number	US-201113813572-A
Country	US
Kind code	B2
Filing date	Aug 1, 2011
Priority date	Aug 2, 2010
Publication date	Oct 20, 2015
Grant date	Oct 20, 2015

Abstract

Light directing film ( 100 ) is disclosed. The light directing film includes a structured major surface ( 110 ) that includes a plurality of microstructures ( 150 ) extending along a first direction ( 142 ) and a plurality of elevated portions ( 160 ) disposed on the plurality of microstructures. The number density of the elevated portions across the light directing film is D. Each elevated portion includes a leading edge ( 162 ) and a trailing edge ( 164 ) along the first direction. The light directing film can be divided into a plurality of same size and shape grid cells that form a continuous two-dimensional grid. The area of each grid cell is approximately 1/D. Each of at least 70% of the grid cells includes a single leading edge ( 162 ) of an elevated portion ( 160 ).

First claim

What is claimed is:

1. A light directing film comprising a structured major surface comprising a plurality of microstructures extending along a first direction, each microstructure comprising a plurality of elevated portions and a plurality of non-elevated portions, the elevated portions of the plurality of microstructures having an average length, each elevated portion comprising a leading edge and a trailing edge along the first direction, wherein the light directing film can be divided into a plurality of same size and shape grid cells forming a continuous two-dimensional grid, each of at least 90% of the grid cells comprising either a single leading edge of an elevated portion, or a portion of an elevated portion where the elevated portion has a length that is greater than the average length of the elevated portions.

2. The light directing film of claim 1 , wherein each grid cell comprises either a single leading edge of an elevated portion, or a portion of an elevated portion where the elevated portion has a length that is greater than the average length of the elevated portions.

3. The light directing film of claim 1 , wherein at least some of the microstructures have prismatic cross-sectional profiles.

4. The light directing film of claim 1 , wherein at least some of the microstructures have curvilinear cross-sectional profiles.

5. The light directing film of claim 1 , wherein at least some of the microstructures have rectilinear cross-sectional profiles.

6. The light directing film of claim 1 , wherein the non-elevated portions of the microstructures in the plurality of microstructures have a same constant peak height along the first direction.

7. The light directing film of claim 1 , wherein the elevated portions of the microstructures in the plurality of microstructures have a same maximum peak height.

8. The light directing film of claim 1 , wherein the grid cells are rectangular.

9. The light directing film of claim 1 , wherein the grid cells are square.

10. The light directing film of claim 1 , wherein each grid cell includes only one microstructure peak.

11. The light directing film of claim 1 , wherein each grid cell includes peaks of at least three adjacent microstructures.

12. The light directing film of claim 1 , wherein each of at least 90% of the grid cells comprises a single leading edge of an elevated portion.

13. The light directing film of claim 1 , wherein each of less than about 20% of the grid cells does not include a leading edge of an elevated portion and includes a portion of an elevated portion, the elevated portion having a length that is greater than the average length of the elevated portions.

14. The light directing film of claim 1 , wherein at least 90% of the elevated portions have substantially a same length.

15. The light directing film of claim 1 , wherein the elevated portions of each microstructure cover at least about 10% of the microstructure along the first direction.

16. A light directing film comprising a structured major surface comprising a plurality of microstructures extending along a first direction, each microstructure comprising a plurality of elevated portions and a plurality of non-elevated portions, a lateral cross-section of a microstructure in a region of an elevated portion and in a region of a non-elevated portion having a same shape, wherein a diameter of a largest circle that can be overlaid on the structured major surface of the light directing film without including at least a portion of an elevated portion is not greater than about 0.5 mm.

17. A method of distributing a plurality of protrusions on a light directing film, the method comprising the steps of:
(a) providing a light directing film comprising a plurality of microstructures extending along a first direction, each microstructure comprising a peak extending along the first direction;
(b) overlaying a continuous grid on the light directing film, the grid comprising a plurality of same size and shape grid cells, such that each grid cell includes a same number of microstructure peaks;
(c) dividing each grid cell into a same number of sub-cells such that each sub-cell comprises a single microstructure peak;
(d) randomly choosing a single sub-cell in each grid cell; and
(e) placing a leading edge of a protrusion on the single microstructure peak in each randomly chosen sub-cell.

18. The method of claim 17 , wherein each protrusion comprises a trailing edge opposite the leading edge of the protrusion, and wherein carrying out step (e) results in the leading edges of the protrusions being on a same side of the protrusions and the trailing edges of the protrusions being on an opposite side of the protrusions.

19. The method of claim 17 , wherein steps (a) through (e) are carried out sequentially.

Assignees

• Hunt Bryan V
• Emmons Robert M
• Balts Corey D
• 3M Innovative Properties Co

Inventors

• Hunt Bryan V
• Emmons Robert M
• Balts Corey D

Classifications

• G02B5/045

  Prism arrays · CPC title

• G02B6/0053 Primary

  Prismatic sheet or layer; Brightness enhancement element, sheet or layer · CPC title

• G02B6/0001

  specially adapted for lighting devices or systems (lighting or signalling on vehicles using light guides B60Q1/00; lighting devices for vehicle dashboards B60Q3/10; lighting devices for vehicle interior using light guides B60Q3/62; lighting devices mounted on the vehicle rear part using light guides F21S43/235; measuring arrangements having light conducting pointers G01D13/265; illumination of liquid crystal displays G02F1/1336; illuminated signs G09F13/00) · CPC title

• G02B5/04

  Prisms · CPC title

• G02B6/10 Primary

  of the optical waveguide type (G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00) · CPC title