Optical member comprising a polarizing plate and a low-refractive index layer having a porous layer

• US 10,678,083 B2
• Filed: 08/22/2017
• Issued: 06/09/2020
• Est. Priority Date: 09/02/2016
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Nakamura, Kozo, Hattori, Daisuke, Hosokawa, Kazuhito
• Primary Examiner(s): Lee, Paul C
• Application Number:
  US15/682,805
• Publication Number:
  US 20180067250A1
• Time in Patent Office: 1,022 Days
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 5/3041 comprising multiple thin layers, e.g. multilayer stacks
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• 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 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133507 Films for enhancing the luminance
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence

Abstract

There is provided an optical member capable of causing, when used for a liquid crystal display apparatus, light output from a light source to enter a liquid crystal display panel with high efficiency. An optical member according to an embodiment of the present invention includes: a polarizing plate; a reflective polarizer; a λ/4 plate; and a prism layer, the polarizing plate, the reflective polarizer, the λ/4 plate, and the prism layer being integrated in the stated order.

Claims

1. An optical member, comprising:

a polarizing plate;

a reflective polarizer;

a λ

/4 plate; and

a prism layer that comprises a prism portion and a substrate portion, the prism portion comprising a plurality of prisms that are convex in a direction away from the reflective polarizer,

the polarizing plate, the reflective polarizer, the λ

/4 plate, the substrate portion of the prism layer, and the prism portion of the prism layer being integrated in the stated order,

wherein the optical member further comprises a low-refractive index layer integrated at one of a position between the reflective polarizer and the substrate portion of the prism layer, and a position on an opposite side of the reflective polarizer to the prism layer,

wherein the low-refractive index layer has a refractive index of 1.30 or less, and

wherein the low-refractive index layer at least partially has a porous layer.

2. The optical member according to claim 1, wherein the λ

/4 plate has an in-plane retardation Re(550) of from 80 nm to 200 nm, where Re(550) represents an in-plane retardation measured with light having a wavelength of 550 nm at 23°

C.

3. The optical member according to claim 1, wherein an angle formed between a slow axis of the λ

/4 plate and a reflection axis of the reflective polarizer is from 30°

to 60°

.

4. The optical member according to claim 1, wherein the λ

/4 plate comprises an alignment fixed layer of a liquid crystal compound.

5. The optical member according to claim 1, wherein the reflective polarizer comprises a linearly polarized light separation-type reflective polarizer.

6. The optical member according to claim 1, wherein the porous layer comprises a pulverized gel material.

7. The optical member according to claim 1, further comprising a light diffusing layer integrated with the other layers of the optical member,

wherein a distance between the prism portion of the prism layer and the light diffusing layer is from 75 μ

m and 250 μ

m.

8. The optical member according to claim 1, wherein the prism layer is bonded to an adjacent layer via an adhesion layer.

9. The optical member according to claim 1, wherein each of the polarizing plate, the reflective polarizer, the λ

/4 plate, the prism layer, and the low-refractive index layer is in direct contact with an adjacent layer.

10. The optical member according to claim 1, wherein an absorption axis of the polarizing plate is substantially parallel to a reflection axis of the reflective polarizer, and the absorption axis of the polarizing plate is substantially parallel to an edge line direction of the prism layer, the edge line direction of the prism layer being oriented in a longitudinal direction of the prism layer.

11. The optical member according to claim 1, wherein the reflective polarizer comprises at least one first layer having birefringence and at least one second layer that is substantially free of birefringence, and a difference between a refractive index of the first layer and a refractive index of the second layer is from 0.2 to 0.3.