Method for forming liquid crystal display cell walls using a patterned electric field

• US 5,929,960 A
• Filed: 10/17/1997
• Issued: 07/27/1999
• Est. Priority Date: 10/17/1997
• Status: Expired due to Term

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: West, John L., Ji, Yimin, Rouberol, Marc, Francl, James J.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Hollingshead, Robert J.
• Application Number:
  US08/953,596
• Time in Patent Office: 648 Days
• Field of Search: 349/156, 349/155
• US Class Current: 349/156
• CPC Class Codes: G02F 1/133377 Cells with plural compartments or having plurality of liquid crystal microcells partitioned by walls, e.g. one microcell per pixel
• CPC Class Codes: G02F 1/13394 spacers regularly patterned on the cell subtrate, e.g. walls, pillars G02F1/133377 takes precedence

Abstract

A method for forming walls (8) between substrates (11, 12) in a liquid crystal cell (10) includes the step of forming a cell with a liquid crystal-monomer mixture (50). The cell (10) is then exposed to ultraviolet light (70) causing the monomer to be selectively polymerized to form walls (8) between substrates (11, 12) of the cell. The monomer is selectively polymerized by applying an electric field across the cell through a patterned conductive coating (31, 32) on each substrate (11, 12) to separate the dispersed monomer to the low field, interpixel regions (72). The cell (10) is then exposed to ultraviolet light (70) to polymerize the separated monomer to form the walls (8) in the low field regions (72).

Claims

1. A method for forming walls in situ in a liquid crystal display cell comprising the steps of:

providing a liquid crystal display cell having a liquid crystal-monomer mixture disposed between patterned electrically conductive coatings on opposed substrates, wherein an intersection of the patterned electrically conductive coatings forms a pixel region;

applying a voltage across the cell to form a high-field region between the substrates in said pixel region and a low field region elsewhere such that the monomer separates into said low field region; and

exposing the cell to ultraviolet light until polymer walls form in the low-field regions between the substrates.

2. A method according to claim 1, wherein the step of providing a liquid crystal cell comprises the steps of:

providing upper and lower substrates;

applying a patterned electrically conductive coating to each substrate;

adding a liquid crystal monomer mixture to one of the substrates; and

forming the cell by placing one of the substrates over the other substrate.

3. A method according to claim 2, further comprising the step of offsetting one substrate to form a pair of ledges.

4. A method according to claim 3, further comprising the step of attaching a conductive tape to the ledge such that the tape forms an electrical connection with the conductive coating.

5. A method according to claim 2, further comprising the step of sealing the edges of the cell.

6. A method according to claim 1, further comprising the step of heating the cell to substantially 65 degrees celsius.

7. A method according to claim 1, further comprising the step of applying 50 volts AC to the cell.

8. A method for forming walls in situ in a liquid crystal display cell comprising the steps of:

providing upper and lower substrates;

forming patterned, electrically conductive coatings on each of the substrates, wherein an intersection of the patterned electrically conductive coatings forms a pixel region;

adding a liquid crystal-monomer mixture to one of the substrates over the coating;

positioning the other substrate over the mixture such that the coating contacts the mixture;

applying a voltage across the mixture to form a high field region between the substrates in said pixel region and a low field region elsewhere such that the monomer separates into said low field region; and

exposing the mixture to ultraviolet light until walls form in the low-field regions between the substrates.

9. A method according to claim 8, further comprising the step of dispersing ball spacers on the substrates before the mixture is added.

10. A method according to claim 8, further comprising the steps of:

forming a row pattern of conductive coating on one of the substrates and a column pattern of conductive coating on the other substrate; and

assembling the substrates so that the row pattern and column pattern cooperate to form a grid pattern.

11. A method for forming walls in situ in a liquid crystal cell comprising the steps of:

providing upper and lower substrates;

forming patterned, electrically conductive coatings on each of the substrates, wherein an intersection of the patterned electrically conductive coatings forms a pixel region;

adding a liquid crystal-thermoplastic mixture to one of the substrates over the coating;

positioning the other substrate over the mixture such that the coating contacts the mixture;

heating the mixture;

applying an electric field across the mixture to form a high field region between the substrates in said pixel region and a low field region elsewhere such that the thermoplastic separates into said low field region; and

cooling the mixture until the thermoplastic hardens in the low field regions to form walls between the substrates.