Brightness enhancement article

• US 6,280,063 B1
• Filed: 05/09/1997
• Issued: 08/28/2001
• Est. Priority Date: 05/09/1997
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Cobb, Sanford Jr., Miller, Richard A., Kretman, Wade D., Williams, Todd R., Kotchick, Keith M., Fong, Bettie C., Toyooka, Kazuhiko
• Primary Examiner(s): CARIASO, ALAN B
• Application Number:
  US08/853,261
• Time in Patent Office: 1,572 Days
• Field of Search: 349/57, 349/62-65, 349/112, 359/599, 359/837, 359/452-457, 359/460, 362/278, 362/330-333, 362/336, 362/337, 362/339, 362/26, 362/31, 362/268
• US Class Current: 362/333
• CPC Class Codes: G02B 5/045 Prism arrays

Abstract

A brightness enhancement article that includes: (a) a transparent, flexible substrate; (b) a first major surface having an array of prisms with blunted or rounded peaks characterized by a chord width, cross-sectional pitch width, and radius of curvature in which the chord width is equal to about 20-40% of the cross-sectional pitch width and the radius of curvature is equal to about 20-50% of the cross-sectional pitch width; and (c) a second major surface characterized by a plurality of light scattering protrusions. The article has a haze value between about 20-60% and a transmission value no greater than about 94% when measured under conditions in which the first surface has a substantially planar topography.

Claims

1. A brightness enhancement article comprising:

(a) a transparent, flexible substrate;

(b) a first major surface comprising an array of linear prisms having blunted or rounded peaks characterized by a chord width, cross-sectional pitch width, and radius of curvature in which the chord width is equal to about 20-40% of the cross-sectional pitch width and the radius of curvature is equal to about 20-50% of the cross-sectional pitch width; and

(c) a second major surface characterized by a plurality of light scattering protrusions,

said article having a haze value between about 20-60% and a transmission value no greater than about 94% when measured under conditions in which said first surface has a substantially planar topography.

2. A brightness enhancement article according to claim 1 wherein said prisms are characterized by a root angle ranging from about 70°

to about 110°

.

3. A brightness enhancement article according to claim 1 wherein said prisms are characterized by a root angle ranging from about 85°

to about 95°

.

4. A brightness enhancement article according to claim 1 wherein said prisms are characterized by a root angle of about 90°

.

5. A brightness enhancement article according to claim 1 wherein said second major surface is integral with said substrate.

6. A brightness enhancement article according to claim 1 wherein said second major surface is defined by a layer comprising a resin provided on said substrate.

7. A brightness enhancement article according to claim 6 wherein said light scattering protrusions comprise particles dispersed in said resin.

8. A brightness enhancement article according to claim 6 wherein said light scattering protrusions are integral with said resin layer.

9. A brightness enhancement article according to claim 1 wherein said first major surface is integral with said substrate.

10. A brightness enhancement article according to claim 1 wherein said first major surface is defined by a layer comprising a resin provided with said prisms.

11. A brightness enhancement article comprising:

(a) a transparent, flexible substrate;

(b) a first major surface defined by a layer comprising a resin provided on said substrate,

said first major surface comprising an array of prisms having blunted or rounded peaks characterized by a chord width, cross-sectional pitch width, and radius of curvature in which the chord width is equal to about 20-40% of the cross-sectional pitch width and the radius of curvature is equal to about 20-50% of the cross-sectional pitch width; and

(c) a second major surface defined by a layer comprising a resin provided on said substrate,

said second major surface comprising a plurality of light scattering protrusions,

said article having a haze value between about 20-60% and a transmission value no greater than about 94% when measured under conditions in which said first surface has a substantially planar topography.

12. A brightness enhancement article according to claim 11 wherein said prisms are characterized by a root angle ranging from about 70°

to about 110°

.

13. A brightness enhancement article according to claim 11 wherein said prisms are characterized by a root angle ranging from about 85°

to about 95°

.

14. A brightness enhancement article according to claim 11 wherein said prisms are characterized by a root angle of about 90°

.

15. A method of enhancing the brightness of a uniform, diffusely-emitting, lighting device having a light-emitting surface,

said method comprising placing a brightness enhancement article substantially parallel to said light-emitting surface,

said article comprising:

(a) a transparent, flexible substrate;

(b) a first major surface comprising an array of prisms having blunted or rounded peaks,

said peaks being characterized by a chord width, cross-sectional pitch width, and radius of curvature in which the chord width is equal to about 20-40% of the cross-sectional pitch width and the radius of curvature is equal to about 20-50% of the cross-sectional pitch width; and

(c) a second major surface characterized by a plurality of light scattering protrusions,

said article having a haze value between about 20-60% and a transmission value no greater than about 94% when measured under conditions in which said first surface has a substantially planar topography.

16. A method according to claim 15 comprising placing said brightness enhancement article substantially parallel to the light-emitting surface of a back-lit display device.

17. A method according to claim 15 comprising placing said brightness enhancement article substantially parallel to the light-emitting surface of a back-lit liquid crystal display device.

18. A device comprising:

(a) a uniform, diffusely-emitting, lighting device having a light-emitting surface; and

(b) a brightness enhancement article placed substantially parallel to said light-emitting surface,

said brightness enhancement article comprising;

(i) a transparent, flexible substrate;

(ii) a first major surface comprising an array of prisms having blunted or rounded peaks characterized by a chord width, cross-sectional pitch width, and radius of curvature in which the chord width is equal to about 20-40% of the cross-sectional pitch width and the radius of curvature is equal to about 20-50% of the cross-sectional pitch width; and

(iii) a second major surface characterized by a plurality of light scattering protrusions,

said article having a haze value between about 20-60% and a transmission value no greater than about 94% when measured under conditions in which said first surface has a substantially planar topography.

19. A device according to claim 18 wherein said lighting device is in the form of a back-lit display device.

20. A device according to claim 18 wherein said lighting device is in the form of a back-lit liquid crystal display device.