Electrically-actuated variable transmission film having very low haze and a visible grid in a clear state

Patent metadata

Field	Value
Publication number	US-11520210-B2
Application number	US-202017034998-A
Country	US
Kind code	B2
Filing date	Sep 28, 2020
Priority date	Sep 30, 2019
Publication date	Dec 6, 2022
Grant date	Dec 6, 2022

Abstract

A light attenuator that provides transparent light states and absorbing dark states for use in selectively controlling light, especially for smart glass applications. The light attenuator includes abutting areas of attenuation and transparency that form a repeat pattern or a quasi-repeat pattern. The attenuating areas are visible when the light attenuator is in the light state, but the repeat pattern is sufficiently large that a viewer looks through the attenuator and sees no haze.

First claim

The invention claimed is:

1. A light attenuator ( 200 , 203 , 204 ) comprising a cell ( 300 , 303 , 304 ) having a first transparent substrate ( 190 ) and a second transparent substrate ( 190 ) defining respective viewing faces ( 150 , 153 , 154 ) and with opposite major surfaces having transparent electrodes ( 160 ) and spaced apart ( 5 ) to provide a volume there between, said volume containing a transparent polymer structure ( 100 , 103 , 104 ) and electrophoretic ink ( 1 , 2 , 3 ), said electrophoretic ink comprising charged particles ( 10 , 11 , 12 ) dispersed in a transparent fluid ( 15 , 16 , 17 ),
wherein said charged particles are responsive to an electric field applied to said electrodes and move between: a first extreme light state in which said charged particles are maximally spread within said cell to lie in a path of sunlight through the cell, thereby attenuating the sunlight, and a second extreme light state in which said charged particles are maximally concentrated within the cell in locations ( 130 , 133 , 134 ) defined by said polymer structure thereby removing said charged particles from the path of sunlight through the cell, transmitting the sunlight, and providing visual access,
wherein in said second light state, a viewing face of said light attenuator has a visible pattern of attenuating areas ( 20 , 24 ) abutting on transparent areas ( 30 , 34 ) defined by a presence and an absence, respectively, of concentrated charged particles, and
wherein a repeating unit of said visible pattern consists of an attenuating area and a transparent area, and wherein said repeating unit has a dimension ( 50 , 55 and 60 , 65 ) between 0.3 mm and 3 cm, while a centre-to-centre distance ( 40 , 41 ) of adjacent attenuating areas or a centre-to-centre distance ( 45 , 46 ) of adjacent transparent areas is between 0.6 mm and 6 cm.

2. A light attenuator as claimed in claim 1 , wherein each of said areas in said visible pattern subtends an angle ( 80 , 90 ) of more than two arc minutes at a distance of 0.5M from said viewing face and said abutted areas subtend an angle ( 70 ) of more than four arc minutes.

3. A light attenuator as claimed in claim 1 , wherein the visible pattern is a repeating pattern, and said centre-to-centre distances ( 40 , 45 ) are the same as a pitch ( 1041 ).

4. A light attenuator as claimed in claim 3 , wherein said repeating pattern is a switchable grid that is visible in said second light state and indistinguishable in said first light state, and the switchable grid is a colour of said charged particles.

5. A light attenuator as claimed in claim 3 , wherein the centre-to-centre distance of said transparent areas ( 61 ) is 75% or more of said pitch ( 1041 ) and the centre-to-centre distance of the attenuating areas ( 51 ) is 25% or less.

6. A light attenuator as claimed in claim 1 , wherein the transparent area in a face view is 60% or more of a total active (i.e., switchable) area in the face view, preferably 62% or more, more preferably 65% or more, and most preferably 70% or more, and said visible pattern is perceivable as a pattern of attenuating areas.

7. A light attenuator as claimed in claim 6 , wherein the visible pattern is superposed on said visual access.

8. A light attenuator as claimed in claim 1 , wherein a shape of said attenuating and transparent areas is selected to minimize moiré patterns.

9. A light attenuator as claimed in claim 1 , wherein said centre-to-centre distance of adjacent attenuating areas and said centre-to-centre distance of adjacent transparent areas is 0.6 mm or more.

10. A light attenuator as claimed in claim 1 , wherein the centre-to-centre distance of the adjacent attenuating areas and the centre-to-centre distance of the adjacent transparent areas is in order of preference: 0.62 mm to 5.8 cms, 0.65 mm to 5.5 cms, 0.7 mm to 5.14 cms, 0.8 mm to 4.5 cms, 1.0 mm to 3.6 cms, and most preferably 1.25 mm to 3 cms, and wherein the abutting attenuating areas and transparent areas each have one or more dimensions that are in order of preference: 0.31 mm to 2.9 cms, 0.325 mm to 2.75 cms, 0.35 mm to 2.57 cms, 0.4 mm to 2.25 cms, 0.5 mm to 1.8 cms, and most preferably 0.625 mm to 1.5 cms.

11. A light attenuator as claimed in claim 1 , wherein the polymer structure spaces apart said first and second substrates and divides said volume into a monolayer of discrete cavities having polymer walls and filled with said electrophoretic ink, and preferably said polymer structure includes a sealing layer sealing the ink within the cavities.

12. A light attenuator as claimed in claim 11 , wherein a colour layer is selectively applied to said polymer walls so that in said viewing face a colour of the polymer walls match a colour of said attenuating areas.

13. A light attenuator as claimed in claim 11 , wherein said locations of said concentrated charged particles are at said polymer walls.

14. A light attenuator as claimed in claim 11 , wherein said locations of said concentrated charged particles are in discrete reservoirs in said polymer structure and the locations do not coincide with said polymer walls.

15. A light attenuator as claimed in claim 11 , wherein said locations of said concentrated charged particles are in depressions or channels between protrusions in said polymer structure and the locations may or may not coincide with said polymer walls.

16. A light attenuator as claimed in claim 1 , wherein a colour mask is selectively applied to a surface of said substrates or electrodes defined by said locations, and in said viewing face on a same side as the colour mask, a colour of the locations is different from a colour of said charged particles, and wherein the colour mask masks said concentrated charged particles in said second light state and forms areas corresponding to said attenuating areas.

17. A light attenuator as claimed in claim 1 , wherein said electrophoretic ink has two or more charged particle types selected from the group including: positively charged, negatively charged, differing electrophoretic mobility, and different colours.

18. A light attenuator as claimed in claim 17 , wherein said electrophoretic ink has two charged particles types each having a different electrophoretic mobility and a different colour from each other, but the two charged particle types have a same charge polarity, wherein in the second light state, said two charged particle types segregate as they concentrate at said locations with one charged particle type masking the other with respect to one of said viewing faces.

19. A light attenuator as claimed in claim 1 wherein said charged particles move between said first and second light states to provide at least one light state intermediate said first and second light states.

20. A light attenuator as claimed in claim 1 , wherein an embodiment includes one of: a window, a mirror, a light shutter, a light modulator, a variable light transmittance sheet, a variable light absorbance sheet, a variable light reflectance sheet, an electrophoretic sun visor for a vehicle, or a see-through display, incorporating the light attenuator.

Assignees

• E Ink Corp

Inventors

• O'Keeffe Donal Martin
• O'Keeffe Timothy

Classifications

• G02F1/1677 Primary

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

• G02F2203/01

  transmissive · CPC title

• E06B2009/2405

  Areas of differing opacity for light transmission control · CPC title

• G09G3/344

  based on particles moving in a fluid or in a gas, e.g. electrophoretic devices (electrophoretic devices per se G02F1/167) · CPC title

• G02F1/167 Primary

  by electrophoresis · CPC title