Optical film having a liquid crystal layer including twisted nematic liquid crystal compounds

Patent metadata

Field	Value
Publication number	US-10989850-B2
Application number	US-201414902959-A
Country	US
Kind code	B2
Filing date	Sep 29, 2014
Priority date	Sep 27, 2013
Publication date	Apr 27, 2021
Grant date	Apr 27, 2021

Abstract

The present application relates to an optical film and a use thereof. In the present application, through control of an alignment state of a liquid crystal compound in a liquid crystal layer, the liquid crystal layer may exhibit so-called reverse-wavelength dispersion while forming a single thin layer. An optical film including the liquid crystal layer may show optical modulation in a display device such as a liquid crystal display (LCD), organic light emitting device (OLED), or the like, or may be used in various applications, for example, as an optical element capable of improving light utilization efficiency, an element for implementation of a stereoscopic image and quality improvement thereof, and so forth.

First claim

What is claimed is:

1. An optical film comprising a twisted nematic (TN) liquid crystal layer, the TN liquid crystal layer comprising:
nematic liquid crystal compounds twisted along a virtual helical axis aligned in the TN liquid crystal layer and polymerized in a TN aligned state such that the helical axis is parallel to a thickness direction of the TN liquid crystal layer, and of the following Formula 1, and an angle between an optical axis of the nematic liquid crystal compounds present in the lowermost part of the TN layer and an optical axis of the nematic liquid crystal compounds present in the uppermost part of the TN layer is in a range from 50 to 300 degrees, and the layer does not include any cholesteric liquid crystal compounds having a twist angle of 360 degrees; and
a chiral agent forming a concentration gradient along a thickness direction of the liquid crystal layer, wherein a rotation angle of the liquid crystal compound variably changes in the thickness direction so that a change of an angle between the optical axis of the liquid crystal compound at the lowermost part of the TN liquid crystal layer and the optical axis of the liquid crystal compound according to a thickness is not constant,
wherein:
the liquid crystal layer exhibits a reverse-wavelength dispersion and satisfies the following Expression 1:
Expression 1
R(650)/R(550)>R(550)/R(550)>R(450)/R(550)

where R(650) is an in-plane retardation value of the TN liquid crystal layer with respect to light with a wavelength of 650 nm, R(550) is an in-plane retardation value of the TN liquid crystal layer with respect to light with a wavelength of 550 nm, and R(450) is an in-plane retardation value of the TN liquid crystal layer with respect to light with a wavelength of 450 nm,

wherein in Formula 1, A is a single bond, —COO—, or —OCO—, and R 1 to R 10 are independently hydrogen, a halogen, an alkyl group, an alkoxy group, a cyano group, a nitro group, —O-Q-P, or a substituent of the following Formula 2, respectively, and at least one of R 1 to R 10 is —O-Q-P or a substituent of the following Formula 2, where Q is an alkylene group or an alkylidene group, and P is an alkenyl group, an epoxy group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group,

wherein in Formula 2, B is a single bond, —COO—, or —OCO—, and R 11 to R 15 are each independently hydrogen, a halogen, an alkyl group, an alkoxy group, a cyano group, a nitro group, or —O-Q-P, and at least one of R 11 to R 15 is —O-Q-P, where Q is an alkylene group or an alkylidene group, and P is an alkenyl group, an epoxy group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group.

2. The optical film of claim 1 , wherein the R(650)/R(550) is in a range from 1.01 to 1.19, and the R(450)/R(550) is in a range from 0.81 to 0.99.

3. The optical film of claim 1 , wherein the in-plane retardation of the TN liquid crystal layer with respect to light with a wavelength of 550 nm is in a range of 110 to 220 nm, or in a range of 240 to 350 nm.

4. The optical film of claim 1 , wherein the TN liquid crystal layer has a thickness in a range of 0.1 to 10 μm.

5. An optical laminate comprising a polarizing layer and the optical film of claim 1 arranged on one surface of the polarizing layer.

6. An optical laminate comprising:
the optical film of claim 1 ; and
a retardation film positioned at one side of the optical film.

7. The optical laminate of claim 6 , wherein an angle between a slow axis of the retardation film and an optical axis of the nematic liquid crystal compound positioned most adjacent to the retardation film in the liquid crystal layer is in a range of 5 to 90 degrees.

8. The optical laminate of claim 6 , further comprising a polarizing layer.

9. The optical laminate of claim 6 , sequentially comprising the polarizing layer, the retardation film, and the optical film, wherein an angle between a light absorbance axis of the polarizing layer and a slow axis of the retardation film is in a range of 10 to 20 degrees, and an angle between a slow axis of the retardation film and an optical axis of the nematic liquid crystal compound positioned most adjacent to the retardation film in the liquid crystal layer of the optical film is in a range of 8 to 16 degrees.

10. The optical laminate of claim 9 , wherein a twist angle of the liquid crystal layer is in a range of 36 to 50 degrees.

11. The optical laminate of claim 6 , sequentially comprising the polarizing layer, the retardation film, and the optical film, wherein a slow axis of the retardation film and a light absorbance axis of the polarizing layer are perpendicular to each other, and an optical axis of the liquid crystal compound most adjacent to the retardation film in the liquid crystal layer of the optical film is in a range of 50 to 70 degrees.

12. The optical laminate of claim 11 , wherein a twist angle of the liquid crystal layer is in a range of 10 to 30 degrees.

13. The optical laminate of claim 6 , sequentially comprising the polarizing layer, the retardation film, and the optical film, wherein a slow axis of the retardation film and a light absorbance axis of the polarizing layer are parallel to each other, and an angle between an optical axis of the liquid crystal compound most adjacent to the retardation film in the liquid crystal layer of the optical film and a slow axis of the retardation film is in a range of 15 to 35 degrees.

14. The optical laminate of claim 13 , wherein a twist angle of the liquid crystal layer is in a range of 60 to 85 degrees.

15. A method of producing the optical film of claim 1 , comprising:
inducing a variable change in concentration according to a thickness of a coating layer of the chiral agent with respect to a liquid crystal coating layer comprising a nematic liquid crystal compound, a chiral agent, and a polymerization initiator; and
polymerizing the nematic liquid crystal compound while the change in concentration of the chiral agent is induced resulting in a non-linear change of angle between the optical axis of the liquid crystal compound at the lowermost part of the liquid crystal coating layer and the optical axis of the liquid crystal compound according to a thickness.

16. The method of producing the optical film of claim 15 , wherein steps of inducing a change in concentration and polymerizing the liquid crystal compound comprise a process of irradiating a liquid crystal coating layer with ultraviolet rays of an ultraviolet ray A area at an intensity of radiation of 10 to 500 mJ/cm 2 at 40 to 80° C.; and a process of irradiating a liquid crystal coating layer having a change in concentration of the chiral agent with ultraviolet rays.

17. A display device comprising the optical film of claim 1 .

18. The optical film of claim 1 , wherein a graph in which an x-axis is a thickness of the TN liquid crystal layer, and a y-axis is an angle between an optical axis of the TN liquid crystal compound present in the corresponding thickness and an optical axis of the liquid crystal compound present in the lowermost part of the TN liquid crystal layer (the position where the x is 0) is nonlinear as shown in FIG. 2B .

19. The optical film of claim 18 , wherein the graph

Assignees

• Lg Chemical Ltd

Inventors

• Lee Dae Hee
• Chang Jun Won
• Kim Young Jin
• Park Moon Soo
• Belyaev Sergey

Classifications

• G02B5/3083

  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 title

• G02B5/3016 Primary

  involving passive liquid crystal elements (optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528) · CPC title

• G02F1/1397

  the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells · CPC title

• G02F1/13363

  Birefringent elements, e.g. for optical compensation · CPC title

• G02F1/133636

  with twisted orientation, e.g. comprising helically oriented LC-molecules or a plurality of twisted birefringent sublayers · CPC title