Alignment layer with reactive mesogens for aligning liquid crystal molecules

• US 8,481,130 B2
• Filed: 09/13/2012
• Issued: 07/09/2013
• Est. Priority Date: 08/08/2003
• Status: Active Grant

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Harding, Richard, May, Alison Linda, Greenfield, Simon, Lub, Johan, Doornkamp, Ciska, Wegh, Rene Theodorus
• Primary Examiner(s): Hon, Sophie
• Application Number:
  US13/614,733
• Publication Number:
  US 20130012654A1
• Time in Patent Office: 299 Days
• Field of Search: 428/1.2, 428/1.26, 349/123, 349/135, 252/299.01, 252/299.4, 427/162
• US Class Current: 428/1.2
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C09K 2323/02 Alignment layer characterised by chemical composition
• CPC Class Codes: C09K 2323/027 Polyimide
• CPC Class Codes: G02F 1/133711 by organic films, e.g. polymeric films
• CPC Class Codes: G02F 1/133723 Polyimide, polyamide-imide
• CPC Class Codes: G02F 1/133726 made of a mesogenic material
• CPC Class Codes: Y10T 428/31721 Of polyimide

Abstract

The invention relates to an alignment layer with improved adhesion to liquid crystal (LC) films, to a precursor material used for the preparation of such a layer, to a laminate comprising such a layer and at least one LC polymer film, and to the use of the alignment layer and the laminate for optical, electrooptical, decorative or security uses and devices, wherein the alignment layer and the precursor material comprise at least one reactive mesogen in monomeric, oligomeric or polymeric form.

Claims

1. A method for preparing an alignment layer for aligning liquid crystal molecules, and a layer of liquid crystal molecules aligned by the alignment layer, said alignment layer comprising:

(a) a polymer film formed from a polymer or from a polymer precursor and (b) at least one reactive mesogen additive in monomeric, oligomeric or polymeric form within said polymer film, wherein said at least one reactive mesogen additive is not said polymer or said polymer precursor used to form said polymer film, and wherein, after preparation of said alignment layer, said alignment layer contains unreacted polymerizable groups in said at least one reactive mesogen additive, said method comprising;

depositing a layer of a solution onto a surface, said solution containing said polymer or polymer precursor, processing said layer of solution to form said alignment layer, and applying a layer of liquid crystal molecules onto said formed alignment layer, thereby aligning the liquid crystal molecules, wherein said at least one reactive mesogen additive is incorporated into said layer of solution before said processing, and wherein the concentration of said at least one reactive mesogen additive in said polymer or polymer precursor is 0.5 to 4% by weight.

2. A method according to claim 1, wherein said at least one reactive mesogen additive is present in monomeric or oligomeric form in the alignment layer after the preparation of said alignment layer.

3. A method according to claim 2, wherein said at least one reactive mesogen additive is present in monomeric form in the alignment layer after the preparation of said alignment layer.

4. A method according to claim 1, wherein said alignment layer is obtained from a polymer precursor comprising at least one reactive mesogen.

5. A method according to claim 1, wherein said alignment layer comprises a polyimide film and said at least one reactive mesogen additive within said polyimide film, and said alignment layer is obtained from a solution comprising a polyimide precursor and said at least one reactive mesogen additive.

6. A method according to claim 5, wherein said polyimide film has repeating units of formula A

7. A method according to claim 1, wherein said at least one reactive mesogen additive is of one of the following formulae:

8. A method according to claim 7, wherein the concentration of said at least one reactive mesogen in said polymer or polymer precursor is 1 to 2% by weight.

9. A method according to claim 1, wherein said alignment layer has a birefringence of less than 0.05.

10. A method according to claim 1, wherein said alignment layer has a birefringence of less than 0.005.

11. A method according to claim 1, wherein said at least one reactive mesogen is added to a solution of said polymer or said polymer precursor.

12. A method according to claim 1, wherein the concentration of said at least one reactive mesogen in said polymer or polymer precursor is comprises 1 to 2% by weight.

13. A method according to claim 1, wherein, after said alignment layer is processed from said layer of solution, said at least one reactive mesogen is physically trapped within said polymer of said polymer film.

14. A method according to claim 13, wherein said alignment layer is obtained by applying to a substrate a solution of said polymer of said polymer film, and said solution further contains said at least one reactive mesogen, said solution being applied to said substrate, and processing of said alignment layer comprises heating said solution to remove excess solvent.

15. A method according to claim 1, wherein said alignment layer is obtained by applying to a substrate a solution comprising said at least one reactive mesogen and a polymer precursor for forming said polymer film, and processing of said alignment layer comprises subjecting said polymer precursor to polymerization.

16. A method according to claim 1, wherein the material of said alignment layer or precursor material thereof, before addition of said at least one reactive mesogen, is non-mesogenic and has a birefringence Δ

n of <

0.01.

17. A method of preparing an optical, electrooptical, information storage, decorative or security device, said device having a layer of liquid crystal molecules, said method comprising:

providing said device with an alignment layer for aligning the layer of liquid crystal molecules, wherein said alignment layer is prepared according to claim 1.

18. A method of preparing an optical component or device, said component or device having a layer of liquid crystal molecules, said method comprising:

providing said component or device with at least one alignment layer for aligning the layer of liquid crystal molecules, wherein said at least one alignment layer is prepared according to claim 1.

19. A method of preparing liquid crystal display, said display having a layer of liquid crystal molecules, said method comprising:

providing said display with at least one alignment layer for aligning the layer of liquid crystal molecules, wherein said at least one alignment layer is prepared according to claim 1.

20. A solution for preparing an alignment layer for aligning a layer of liquid crystal molecules, said alignment layer comprising:

(a) a polymer film formed from a polymer or a polymer precursor and (b) at least one reactive mesogen additive in monomeric, oligomeric or polymeric form within said polymer film, wherein said at least one reactive mesogen additive is not said polymer or said polymer precursor used to form said polymer film, said solution comprising;

a solvent, said at least one reactive mesogen additive, and a polymer or a polymer precursor, said polymer or polymer precursor comprising;

a polyimide polymer or a precursor of said polyimide polymer,

wherein in said solution the concentration of said at least one reactive mesogen relative to said polymer or polymer precursor before forming said film is 0.5 to 4% by weight, and said at least one reactive mesogen additive is miscible with said polymer film formed from said polymer or polymer precursor, wherein said at least one reactive mesogen additive is one of the following formulae;

21. A solution according to claim 20, wherein said polymer or polymer precursor forms an alignment layer having a birefringence of less than 0.05.

22. A solution according to claim 20, wherein said polymer or polymer precursor forms an alignment layer having birefringence of less than 0.005.

23. A solution according to claim 20, wherein said polymer or polymer precursor comprises 1 to 2% by weight of said at least one reactive mesogen.

24. A method for preparing an alignment layer for aligning liquid crystal molecules, and a layer of liquid crystal molecules aligned by the alignment layer, said alignment layer comprising:

(a) a polymer film formed from a polymer or from a polymer precursor and (b) at least one reactive mesogen additive in monomeric, oligomeric or polymeric form within said polymer film, wherein said at least one reactive mesogen additive is not said polymer or polymer precursor used to form said polymer film, and wherein, after preparation of said alignment layer, said alignment layer contains unreacted polymerizable groups in said at least one reactive mesogen additive, said method comprising;

depositing a layer of a solution onto a surface, said solution containing said polymer or polymer precursor, processing said layer of solution to form said alignment layer, and applying a layer of liquid crystal molecules onto said formed alignment layer, thereby aligning the liquid crystal molecules, wherein said at least one reactive mesogen additive is incorporated into said layer of solution before said processing, the concentration of said at least one reactive mesogen additive in said polymer or polymer precursor is 0.5 to 4% by weight, and said at least one reactive mesogen additive is miscible with said polymer film formed from said polymer or polymer precursor.