Optical unit and liquid crystal display module

• US 20080123028A1
• Filed: 06/25/2007
• Published: 05/29/2008
• Est. Priority Date: 06/26/2006
• Status: Active Grant

• Current Assignee: KEIWA, Inc.
• Original Assignee: KEIWA, Inc.
• Inventors: Harada, Kenichi
• Granted Patent: US 8,928,843 B2
• Time in Patent Office: Days
• US Class Current: 349/96
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation

Abstract

An object of the present invention is to provide an optical unit and a backlight unit which can markedly enhance utilization efficiency of rays of light and dramatically increase luminance, and which are suited for immediate beneath type liquid crystal display modules and the like. The optical unit of the present invention is a rectangular layered structural member having a reflection polarizing plate, an optical sheet superposed on the back face side of the reflection polarizing plate, and a transparent media layer filled between the reflection polarizing plate and the optical sheet. This optical sheet includes a resin substrate film having an optical anisotropy, and the absolute value of the angle of the crystal orientation of the substrate film with respect to the transmission axial orientation of the reflection polarizing plate is π/8 or greater and 3π/8 or less. The retardation value of the substrate film is preferably 70 nm or greater and 320 nm or less. The optical sheet preferably has an optical layer laminated on one face of the substrate film. The liquid crystal display module of the present invention has a liquid crystal display element, the optical unit, and an immediate beneath type backlight.

Claims

1. An optical unit comprising a rectangular layered structural member having a reflection polarizing plate that splits reflected beams and transmitted beams on the basis of polarization characteristics, and an optical sheet superposed on the back face side of the reflection polarizing plate,

wherein the optical sheet includes a resin substrate film having an optical anisotropy, and

the absolute value of the angle of the crystal orientation of the substrate film with respect to the transmission axial orientation of the reflection polarizing plate is π

/8 or greater and 3π

/8 or less.

2. The optical unit according to claim 1 further comprising a transparent media layer filled between the reflection polarizing plate and the optical sheet.

3. The optical unit according to claim 1 wherein the retardation value of the substrate film is 70 nm or greater and 320 nm or less.

4. The optical unit according to claim 1 wherein polyethylene terephthalate or polycarbonate is used as a matrix resin constituting the substrate film.

5. The optical unit according to claim 1 wherein the optical sheet has an optical layer laminated on one face of the substrate film.

6. The optical unit according to claim 5 wherein the optical layer comprises multiple particles of a light diffusing agent and a binder therefor.

7. The optical unit according to claim 5 wherein the optical layer has a shape with micro recessions and protrusions having refractivity.

8. The optical unit according to claim 1 wherein the optical sheet has on another face of the substrate film a sticking preventive layer that includes beads dispersed in a binder.

9. A rectangular liquid crystal display module which comprises:

a liquid crystal display element in which a liquid crystal cell is sandwiched between a pair of polarizing plates;

the optical unit according to claim 1 overlaid on the back face side of the liquid crystal display element, and

a surface illuminant backlight of immediate beneath type or opposed edge light type overlaid on the back face side of the optical unit.

10. The liquid crystal display module according to claim 9 wherein the reflection polarizing plate of the optical unit is a back face side-polarizing plate of the liquid crystal display element.

11. The liquid crystal display module according to claim 9 wherein other optical sheet is provided between the liquid crystal display element and the backlight, and

a low-retardation film is used as the substrate film of the other optical sheet.