Light control film and backlight unit using the same

• US 20070182882A1
• Filed: 03/02/2005
• Published: 08/09/2007
• 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 7,926,998 B2
• Time in Patent Office: Days
• US Class Current: 349/64
• CPC Class Codes: G02B 5/02 Diffusing elements; Afocal elements
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members

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 a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ_nv (degree)) of the rough surface with respect to a base plane of the film should be not less than 27 degrees and not more than 70 degrees at substantially any position on the light control film.

Claims

1. A light control film having a rough surface, wherein, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ

_nv (degree)) of the rough surface with respect to a base plane of the film is not less than 27 degrees and not more than 70 degrees at substantially any position on the light control film.

13. The light control film according to claim 1, wherein absolute value of average (φ

_ave) of angles (φ

, −

180 degrees<

φ

180 degrees) between orthogonal projections of normals of the curved surface of the rough surface projected on the base plane and one side of the approximately square region is not more than 5 degrees irrespective of the direction along which the approximately square region is defined in the rough surface.

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

15. The backlight unit according to claim 14, wherein a prism sheet is used between the light control film and the light guide plate.

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

2. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ

_nv (degree)) of the rough surface with respect to a base plane of the film is not less than (59-20 n) degrees and not more than 70 degrees at any position on the light control film.

3. A light control film having a rough surface, wherein, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ

_nv (degree)) of the rough surface with respect to a base plane of the film and a ratio of an area of the approximately square region (A1) and a surface area of the approximated curved surface of the rough surface (A2) (A_r=A2/A1) satisfy the following equation (1) or (2) at substantially any position on the light control film.

θ

_nv÷

A_r22 

 

(1)
30θ

_nv×

A_r140 

 

(2)

4. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ

_nv (degree)) of the rough surface with respect to a base plane of the film and a ratio of an area of the approximately square region (A1) and a surface area of the approximated curved surface of the rough surface (A2) (A_r=A2/A1) satisfy the following equation (3) or (4) at substantially any position on the light control film.

θ

_nv÷

A_r×

n²35 

 

(3)
60θ

_nv×

A_r×

n²350 

 

(4)

5. A light control film having a rough surface, wherein a condition that, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ

_nv (degree)) of the rough surface with respect to a base plane of the film is not less than 27 degrees and not more than 70 degrees, and an absolute value of a numerical value (A_sk) calculated in accordance with the equation (5) by using all the height data of the rough surface is not more than 1.2 is satisfied at substantially any position on the light control film.

$\begin{array}{cc}\left[\mathrm{\#1}\right]& \text{\hspace{1em}<br><br>}\\ \text{\hspace{1em}<br><br>}<br><br>A_{\mathrm{sk}}=\frac{\underset{i=1}{\overset{m}{\sum <br><br>}}<br><br>z_i^3}{m}/{\sqrt{\frac{\underset{i=1}{\overset{m}{\sum <br><br>}}<br><br>z_i^2}{m}}}^3& \left(5\right)\end{array}$

[In the equation (5), z_i represents a value obtained by subtracting a height of average plane of the rough surface from a measured surface height, and m represents a number of measurement points.]

6. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein a condition that, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ

_nv (degree)) of the rough surface with respect to a base plane of the film is not less than (59-20 n) degrees and not more than 70 degrees, and an absolute value of a numerical value (A_sk) calculated in accordance with the equation (5) by using all the height data of the rough surface is not more than 1.2 is satisfied at substantially any position on the light control film.

$\begin{array}{cc}\left[\mathrm{\#2}\right]& \text{\hspace{1em}<br><br>}\\ \text{\hspace{1em}<br><br>}<br><br>A_{\mathrm{sk}}=\frac{\underset{i=1}{\overset{m}{\sum <br><br>}}<br><br>z_i^3}{m}/{\sqrt{\frac{\underset{i=1}{\overset{m}{\sum <br><br>}}<br><br>z_i^2}{m}}}^3& \left(5\right)\end{array}$

[In the equation (5), z_i represents a value obtained by subtracting a height of average plane of the rough surface from a measured surface height, and m represents a number of measurement points.]

7. A light control film having a rough surface, wherein a condition that, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ

_nv (degree)) of the rough surface with respect to a base plane of the film is not less than 27 degrees and not more than 70 degrees, and a numerical value (A_ku) calculated in accordance with the equation (6) by using all the height data of the rough surface is not less than 1.5 and not more than 5.0 is satisfied at substantially any position on the light control film.

$\begin{array}{cc}\left[\mathrm{\#3}\right]& \text{\hspace{1em}<br><br>}\\ \text{\hspace{1em}<br><br>}<br><br>A_{\mathrm{ku}}=\frac{\underset{i=1}{\overset{m}{\sum <br><br>}}<br><br>z_i^4}{m}/{\sqrt{\frac{\underset{i=1}{\overset{m}{\sum <br><br>}}<br><br>z_i^2}{m}}}^4& \left(6\right)\end{array}$

[In the equation (6), z_i represents a value obtained by subtracting a height of average plane of the rough surface from a measured surface height, and m represents a number of measurement points.]

8. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein a condition that, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, an average of slopes of the curved surface (θ

_nv (degree)) of the rough surface with respect to a base plane of the film is not less than (59-20 n) degrees and not more than 70 degrees, and a numerical value (A_ku) calculated in accordance with the equation (6) by using all the height data of the rough surface is not less than 1.5 and not more than 5.0 is satisfied at substantially any position on the light control film.

$\begin{array}{cc}\left[\mathrm{\#4}\right]& \text{\hspace{1em}<br><br>}\\ \text{\hspace{1em}<br><br>}<br><br>A_{\mathrm{ku}}=\frac{\underset{i=1}{\overset{m}{\sum <br><br>}}<br><br>z_i^4}{m}/{\sqrt{\frac{\underset{i=1}{\overset{m}{\sum <br><br>}}<br><br>z_i^2}{m}}}^4& \left(6\right)\end{array}$

[In the equation (6), z_i represents a value obtained by subtracting a height of average plane of the rough surface from a measured surface height, and m represents a number of measurement points.]

9. A light control film having a rough surface, wherein a condition that, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, a ratio of an area of the approximately square region (A1) and a surface area of the approximated curved surface of the rough surface (A2) (A_r=A2/A1) is not less than 1.2 and not more than 2.5, and absolute value of a numerical value (A_sk) calculated in accordance with the equation (5) by using all the height data of the rough surface is not more than 1.2 is satisfied at substantially any position on the light control film.

$\begin{array}{cc}\left[\mathrm{\#5}\right]& \end{array}$

A sk = ∑

i = 1 m ⁢

z i 3 m / ∑

i = 1 m ⁢

z i 2 m 3 ( 5 )

[In the equation (5), z_i represents a value obtained by subtracting a height of average plane of the rough surface from a measured surface height, and m represents a number of measurement points.]

10. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein a condition that, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, a ratio of an area of the approximately square region (A1) and a surface area of the approximated curved surface of the rough surface (A2) (A_r=A2/A1) is not less than (2-0.5 n) and not more than 2.5, and absolute value of a numerical value (A_sk) calculated in accordance with the equation (5) by using all the height data of the rough surface is not more than 1.2 is satisfied at substantially any position on the light control film.

$\begin{array}{cc}\left[\mathrm{\#6}\right]& \end{array}$

A sk = ∑

i = 1 m ⁢

z i 3 m / ∑

i = 1 m ⁢

z i 2 m 3 ( 5 )

[In the equation (5), z_i represents a value obtained by subtracting a height of average plane of the rough surface from a measured surface height, and m represents a number of measurement points.]

11. A light control film having a rough surface, wherein a condition that, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, a ratio of an area of the approximately square region (A1) and a surface area of the approximated curved surface of the rough surface (A2) (A_r=A2/A1) is not less than 1.2 and not more than 2.5, and a numerical value A_ku calculated in accordance with the equation (6) by using all the surface height data is not less than 1.5 and not more than 5.0 is satisfied at substantially any position on the light control film.

$\begin{array}{cc}\left[\mathrm{\#7}\right]& \end{array}$

A ku = ∑

i = 1 m ⁢

z i 4 m / ∑

i = 1 m ⁢

z i 2 m 4 ( 6 )

[In the equation (6), z_i represents a value obtained by subtracting a height of average plane of the rough surface from a measured surface height, and m represents a number of measurement points.]

12. A light control film having a rough surface formed by a patterned layer comprising a material having a refractive index n, wherein, for a curved surface of the rough surface approximated in an approximately square region having an area of 1 mm² or larger defined at an arbitrary position on the rough surface by using height data of the rough surface measured with predetermined intervals for the longitudinal and transverse directions in the approximately square region, a ratio of an area of the approximately square region (A1) and a surface area of the approximated curved surface of the rough surface (A2) (A_r=A2/A1) is not less than (2-0.5 n) and not more than 2.5, and a numerical value A_ku calculated in accordance with the equation (6) by using all the surface height data is not less than 1.5 and not more than 5.0 at substantially any position on the light control film.

$\begin{array}{cc}\left[\mathrm{\#8}\right]& \end{array}$

A ku = ∑

i = 1 m ⁢

z i 4 m / ∑

i = 1 m ⁢

z i 2 m 4 ( 6 )

[In the equation (6), z_i represents a value obtained by subtracting a height of average plane of the rough surface from a measured surface height, and m represents a number of measurement points.]