Polymer dispersed liquid crystal cell

• US 6,306,469 B1
• Filed: 01/26/1998
• Issued: 10/23/2001
• Est. Priority Date: 01/28/1997
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Serbutoviez, Christoph, Touwslager, Fredericus J., Kloosterboer, Johan G.
• Primary Examiner(s): Ahmad, Nasser
• Application Number:
  US09/013,546
• Time in Patent Office: 1,366 Days
• Field of Search: 349/187, 349/86, 349/88, 349/92, 349/93, 428/1.1
• US Class Current: 428/1.1
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals

Abstract

The invention provides a method of filling a PDLC cell, a polymerizable mixture suitable for this purpose as well as a display device provided with such a PDLC cell. The mixture in accordance with the invention comprises two types of non-volatile reactive monomers, the first type of monomer being readily miscible with liquid crystalline material and the second type of monomer being poorly miscible with the liquid crystalline material. Such mixtures prove to be very stable. In addition, when such mixtures are used in cells, problems regarding compositional drift do not occur. Cells in which the inventive mixture is used demonstrate a relatively low hysteresis as well as a relatively low switching voltage. By virtue thereof, it is very attractive to use these cells in a display device.

Claims

1. A method of manufacturing a polymer-dispersed liquid crystal cell, in which method a mixture, which predominantly comprises a non-reactive liquid crystalline material as well as reactive monomers and a photoinitiator, comprising:

sandwiching the mixture between two substrates, which are provided with an electrode layer, and

polymerizing the mixture under the influence of radiation, characterized in that the mixture comprises first and second types of non-volatile, reactive monomers, the first type of monomer being readily miscible with the liquid crystalline material and the second type of monomer being poorly miscible with said liquid crystalline material, and

wherein the second type of monomer is an alkyl acrylate whose alkyl group comprises at least 8 and maximally 18 C-atoms.

2. A method as claimed in claim 1, characterized in that the first type of monomer is an ethoxylated alkyl-phenolacrylate whose alkyl group comprises at least five C-atoms.

3. A method as claimed in claim 1, characterized in that the quantity of each of the first and second types of monomers is at least 20% by weight, calculated with respect to the overall quantity of both types of monomers.

4. A method as claimed in claim 1, characterized in that the mixture is introduced into the cell under the influence of a reduced pressure.