Light control film and backlight unit using the same

• US 20070171654A1
• Filed: 03/02/2005
• Published: 07/26/2007
• Est. Priority Date: 03/03/2004
• Status: Active Grant

• Current Assignee: Kimoto Company Limited
• Original Assignee: Kimoto Company Limited
• Inventors: Etori, Hideki
• Granted Patent: US 7,481,564 B2
• Time in Patent Office: Days
• US Class Current: 362/351
• CPC Class Codes: G02B 5/021 the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0278 used in transmission

Abstract

A light control film enabling improvement in front luminance, having appropriate light diffusing property and free from problems of interference pattern, glare etc. is provided.

A light control film 10 having a rough surface is constituted so that, for an arbitrary cross section perpendicular to a base plane of the film, a condition that average (θ_ave, degree) of absolute values of slope with respect to the base plane of a curve along the edge of the cross section is not less than 20 degrees and not more than 75 degrees, and absolute value of skewness (JIS B0601:2001) of the profile curve is not more than 1.2 should be satisfied for substantially any profile curve.

Claims

1. A light control film having a rough surface, wherein the rough surface satisfies, for an arbitrary cross section perpendicular to a base plane of the film, a condition that average (θ

_ave, degree) of absolute values of slope with respect to the base plane of a profile curve along the edge of the cross section contoured by the rough surface is not less than 20 degrees and not more than 75 degrees, and absolute value of skewness (JIS B0601;

2001) of the profile curve is not more than 1.2 for substantially any profile curve.

9. A backlight unit comprising a light guide plate equipped with a light source for at least one end portion thereof and having a light emergent surface approximately perpendicular to the end portion, and a light control film according to claim 1 provided on the light emergent surface of the light guide plate.

10. The backlight unit according to claim 9, wherein a prism sheet is used between the light control film and the light guide plate.

11. A backlight unit comprising a light source, a light diffusive plate provided on one side of the light source and a light control film according to claim 1 provided on the side of the light diffusive plate opposite to the light source side.

2. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein the rough surface satisfies, for an arbitrary cross section perpendicular to a base plane of the film, a condition that average (θ

_ave, degree) of absolute values of slope with respect to the base plane of a profile curve along the edge of the cross section contoured by the rough surface is not less than (36−

10n) degree and not more than (86−

10n), and absolute value of skewness (JIS B0601;

2001) of the profile curve is not more than (n−

0.4) for substantially any profile curve.

12. A backlight unit comprising a light guide plate equipped with a light source for at least one end portion thereof and having a light emergent surface approximately perpendicular to the end portion, and a light control film according to claim 2 provided on the light emergent surface of the light guide plate.

3. A light control film having a rough surface, wherein the rough surface satisfies, for an arbitrary cross section perpendicular to a base plane of the film, a condition that average (θ

_ave, degree) of absolute values of slope with respect to the base plane of a profile curve along the edge of the cross section contoured by the rough surface is not less than 20 degrees and not more than 75 degrees, and kurtosis (JIS B0601;

2001) of the profile curve is not less than 1.5 and not more than 5.0 for substantially any profile curve.

13. A backlight unit comprising a light guide plate equipped with a light source for at least one end portion thereof and having a light emergent surface approximately perpendicular to the end portion, and a light control film according to claim 3 provided on the light emergent surface of the light guide plate.

4. A light control film having a rough surface formed by a patterned layer comprising a material having a predetermined refractive index of n, wherein the rough surface satisfies, for an arbitrary cross section perpendicular to a base plane of the film, a condition that average (θ

_ave, degree) of absolute values of slope with respect to the base plane of a profile curve along the edge of the cross section contoured by the rough surface is not less than (36−

10n) degree and not more than (86−

10n), and kurtosis (JIS B0601;

2001) of the profile curve is not less than 1.5 and not more than (10n−

11) for substantially any profile curve.

14. A backlight unit comprising a light guide plate equipped with a light source for at least one end portion thereof and having a light emergent surface approximately perpendicular to the end portion, and a light control film according to claim 4 provided on the light emergent surface of the light guide plate.

5. A light control film having a rough surface, wherein the rough surface satisfies, for an arbitrary cross section perpendicular to a base plane of the film, a condition that ratio (L_r=L2/L1 ) of a length (L2) of a profile curve along the edge of the cross section contoured by the rough surface to a length (L1) of a straight line defined as an intersection of the base plane and the cross section is 1.1 L_r 1.8, and absolute value of skewness (JIS B0601:

2001) of the profile curve is not more than 1.2 for substantially any cross section.

15. A backlight unit comprising a light guide plate equipped with a light source for at least one end portion thereof and having a light emergent surface approximately perpendicular to the end portion, and a light control film according to claim 5 provided on the light emergent surface of the light guide plate.

6. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein the rough surface satisfies, for an arbitrary cross section perpendicular to a base plane of the film, a condition that ratio (L_r=L2/L1) of a length (L2) of a profile curve along the edge of the cross section contoured by the rough surface to a length (L1) of a straight line defined as an intersection of the base plane and the cross section is (1.9−

0.5n) L_r 1.8, and absolute value of skewness (JIS B0601;

2001) of the profile curve is not more than (n−

0.4) for substantially any cross section.

16. A backlight unit comprising a light guide plate equipped with a light source for at least one end portion thereof and having a light emergent surface approximately perpendicular to the end portion, and a light control film according to claim 6 provided on the light emergent surface of the light guide plate.

7. A light control film having a rough surface, wherein the rough surface satisfies, for an arbitrary cross section perpendicular to a base plane of the film, a condition that ratio (L_r=L2/L1) of a length (L2) of a profile curve along the edge of the cross section contoured by the rough surface to a length (L1) of a straight line defined as an intersection of the base plane and the cross section is 1.1 L_r 1.8, and kurtosis (JIS B0601:

2001) of the profile curve is not less than 1.0 and not more than 4.5 for substantially any cross section.

17. A backlight unit comprising a light guide plate equipped with a light source for at least one end portion thereof and having a light emergent surface approximately perpendicular to the end portion, and a light control film according to claim 7 provided on the light emergent surface of the light guide plate.

8. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein the rough surface satisfies, for an arbitrary cross section perpendicular to a base plane of the film, a condition that ratio (L_r=L2/L1 ) of a length (L2) of a profile curve along the edge of the cross section contoured by the rough surface to a length (L1) of a straight line defined as an intersection of the base plane and the cross section is (1.9−

0.5n) L_r 1.8, and kurtosis (JIS B0601;

2001) of the profile curve is not less than 1.0 and not more than (10n−

11.5) for substantially any cross section.

18. A backlight unit comprising a light guide plate equipped with a light source for at least one end portion thereof and having a light emergent surface approximately perpendicular to the end portion, and a light control film according to claim 8 provided on the light emergent surface of the light guide plate.