Backlight unit with linearly reduced divergence

• US 20070081110A1
• Filed: 10/10/2005
• Published: 04/12/2007
• Est. Priority Date: 10/10/2005
• Status: Active Grant

• Current Assignee: SKC Haas Display Films Co., Ltd. (Dow, Inc.)
• Original Assignee: Eastman Kodak Company
• Inventors: Lee, Junwon
• Granted Patent: US 7,663,712 B2
• Time in Patent Office: Days
• US Class Current: 349/61
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

This invention relates to a display apparatus comprising: a) a light source; b) a light guiding plate for transmitting light from the light source outward from a two-dimensional light-providing surface, one dimension of the light-providing surface defined in a width direction orthogonal to the path of incident light from the light source and the other dimension of the light-providing surface defined in a length direction, orthogonal to the width direction; c) a linear divergence reduction surface for reducing the divergence of light from the light providing surface predominantly with respect to the width direction, to provide a linearly divergence-reduced illumination, whereby divergence along the width direction at full-width half-maximum is less than about 50% of divergence at full-width half-maximum along the length direction; d) a liquid crystal display component for modulating the linearly divergence-reduced light to form a modulated light according to image data, and, e) a diffusing surface in the path of the modulated light.

Claims

1. A display apparatus comprising:

a) a light source;

b) a light guiding plate for transmitting light from the light source outward from a two-dimensional light-providing surface, one dimension of the light-providing surface defined in a width direction orthogonal to the path of incident light from the light source and the other dimension of the light-providing surface defined in a length direction, orthogonal to the width direction;

c) a linear divergence reduction surface for reducing the divergence of light from the light providing surface predominantly with respect to the width direction, to provide a linearly divergence-reduced illumination,

whereby divergence along the width direction at full-width half-maximum is less than about 50% of divergence at full-width half-maximum along the length direction;

d) a liquid crystal display component for modulating the linearly divergence-reduced light to form a modulated light according to image data, and,

e) a diffusing surface in the path of the modulated light.

2. An apparatus according to claim 1 wherein the linear divergence reduction surface comprises a film substrate featured with a plurality of light divergence reduction structures, wherein each light divergence reduction structure is longitudinally extended in the length direction along the light-providing surface, each light divergence reduction structure comprising:

(a) an input aperture optically coupled to the light-providing surface;

(b) an output aperture distal from said input aperture, wherein the output aperture has a surface area that is larger than the surface area of the input aperture; and

,

(c) a pair of curved side walls between the output aperture and the input aperture and extending along the length direction;

wherein, in a cross section taken orthogonally with respect to the width direction, the curved side walls approximate a parabolic curvature.

3. An apparatus according to claim 1 wherein the length direction is substantially parallel to the axis of a light bulb that provides source illumination.

4. An apparatus according to claim 1 wherein the light guiding plate and the linear divergence reduction surface are of the same material.

5. An apparatus according to claim 2 wherein the width of the output aperture varies over the length of the light divergence reduction structure.

6. An apparatus according to claim 2 wherein the pitch between adjacent light divergence reduction structures is substantially equal.

7. An apparatus according to claim 2 wherein the pitch between adjacent light divergence reduction structures is varied.

8. An apparatus according to claim 1 wherein the liquid crystal display component employs in-plane switching.

9. An apparatus according to claim 1 wherein the liquid crystal display component is an optically compensated birefringence type component.

10. An apparatus according to claim 1 wherein the linear divergence reduction surface is molded into the two-dimensional light-providing surface.

11. An apparatus according to claim 1 wherein the modulated light exhibits image contrast of better than about 150:

1 without the use of a compensator article.

12. An apparatus according to claim 1 wherein the liquid crystal display component exhibits an asymmetric response to incident light, such that, for light at normal incidence, the luminance of modulated light from the liquid crystal display component with respect to the width direction of the linear divergence reduction surface differs from the luminance of modulated light of the liquid crystal display component with respect to the length direction of the linear divergence reduction surface by more than 10 degrees at full-width half maximum.