Electrophoretic device having a transparent light state

Patent metadata

Field	Value
Publication number	US-10824025-B2
Application number	US-201816121074-A
Country	US
Kind code	B2
Filing date	Sep 4, 2018
Priority date	Mar 22, 2013
Publication date	Nov 3, 2020
Grant date	Nov 3, 2020

Abstract

A light attenuator comprises a cell comprising a first substrate and a second substrate spaced apart from the first substrate. A layer between the substrates contains an electrophoretic ink, a surface of the layer adjacent the second substrate comprising a monolayer of closely packed protrusions projecting into the layer. The protrusions have surfaces defining a plurality of depressions in the volumes there between. The ink includes charged particles of at least one type, the particles being responsive to an electric field applied to the cell to move between a first extreme light state, in which particles are maximally spread within the cell to lie in the path of light through the cell and to strongly attenuate light transmitted through the cell; over the surface of the protrusions, which deflect the particles from their path from the first substrate to the second substrate; to a second extreme light state in which the particles are maximally concentrated within the depressions to remove them from the path of light through the cell and to substantially transmit light through the cell.

First claim

The invention claimed is:

1. A method of manufacturing an electrophoretic device comprising:
providing a template surface having a contoured shape derived from microstructures;
in one or more moulding steps, replicating said template surface to transfer said shape to the surface of a transparent, non-planar, polymer structure on a transparent second substrate, said replicated microstructures' surfaces including walls and protrusions and said protrusions having surfaces defining a plurality of depressions in the volumes there between;
printing a light masking adhesive layer on said walls of said non-planar, polymer structure in a contact area with a first transparent substrate;
coating said non-planar surface with an electrophoretic suspension, said suspension including charged particles of at least one type in a transparent fluid; and
providing said first substrate spaced apart from said second substrate with said polymer structure disposed between and contacting the first substrate through said adhesive layer to define a volume between the polymer structure and the first substrate; and, curing said adhesive layer to bond said first substrate to said non-planar, polymer structure;
wherein said particles are movable within said volume to interact with said replicated, non-planar, polymer surface to move between a plurality of light states.

2. A method according to claim 1 wherein said template surface is polymer.

3. A method according to claim 1 wherein said moulding steps said replicating includes: transferring said template surface to a negative mould master, and using the master, moulding a replica of said surface on said second substrate; or, using the template, moulding an inverse replica of said surface on said second substrate.

4. A method according to claim 2 wherein said polymer template is a fixed-length, continuous template and is at least 2 meters long, more preferably at least 10 meters, and most preferably at least 15 meters.

5. A method according to claim 3 wherein said template surface is defined by a plurality of polymer microstructures formed by exposing a photosensitive polymer with one of a laser beam or electron beam and subsequently developing said photoresist to reveal said template surface, and transferring said template surface from a polymer surface to a hard material by inversely replicating said template surface using an electroforming process to provide an electroformed, negative mould master that has the inverse shape of the polymer surface.

6. A method according to claim 1 wherein said template surface is defined by a plurality of metal, silicon, fused silica, or calcium fluoride microstructures formed by mechanical milling, chemical etching, ion-beam milling, reactive-ion etching, or laser ablation.

7. A method according to claim 3 where said moulding steps comprise:
forming a negative mould master by coating said template surface with a prepolymer;
curing said coating to inversely replicate said shape as recesses in a polymer layer adhered to a substrate, and peeling apart the negative mould master and the template;
forming said replicated, non-planar, polymer structure by coating said negative mould master with a prepolymer and laminating said second substrate; and
curing said coating to inversely replicate the negative mould master surface as said protrusions in a polymer layer adhered to the second substrate, and peeling apart the negative mould master and the non-planar structure;
wherein the shape of the protrusions in the template is transferred to those in the replicated, non-planar, polymer structure.

8. A method according to claim 3 wherein said moulding steps comprise:
forming said replicated, non-planar, polymer structure by coating said template surface with a prepolymer and laminating said second substrate, curing said coating to inversely replicate said shape as said protrusions in a polymer layer adhered to the second substrate, and peeling apart the template and the non-planar structure;
wherein the template is the mould master and the shape of recesses in the template is transferred to those in the replicated, non-planar, polymer structure.

9. A method according to claim 4 wherein said replicating includes curing said non-planar polymer structure on said second substrate at least in part by thermal means over a time interval of at least one minute and more preferably at least one hour.

10. A method according to claim 1 where said light masking adhesive is printed on said contact area with walls, and where present cell gap spacers and pillars, and said contact area is less than 25% of said device's face-area, and preferably less than 20%, and more preferably less than 17.5%, and most preferably less than 15%.

11. A method according to claim 10 wherein said light masking adhesive has black colorant.

12. A method according to claim 10 wherein said light masking adhesive layer comprises a black polymer layer and an adhesive layer.

13. A method according to claim 1 wherein said printing comprises using an elastomer-coated roller means.

14. A method according to claim 1 wherein said walls space apart the surface of said protrusions from said first substrate, said walls on the surface of protrusions or spanning between said substrates.

Assignees

• E Ink Corp

Inventors

• O'Keeffe Donal

Classifications

• G02F1/167 Primary

  by electrophoresis · CPC title

• G02F1/13396

  Spacers having different sizes · CPC title

• G02F1/1679

  Gaskets; Spacers; Sealing of cells; Filling or closing of cells · CPC title

• G02F1/1677

  Structural association of cells with optical devices, e.g. reflectors or illuminating devices · CPC title

• G02F2203/01

  transmissive · CPC title