# US 11,442,208 B2 · Ultra-thin, flexible thin-film filters with spatially or temporally varying optical properties and methods of making the same

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- Number: US 11,442,208 B2
- Document ID: US11442208B2
- Status: Granted
- Kind: B2
- Application number: 16/613,225
- Filed: 2018-05-16
- Published: 2020-04-09
- Granted: 2022-09-13
- Earliest claimed: 2017-05-17
- Applicants: Everix, Inc.
- Inventors: Esmaeil Banaei; Patricia Ximena Coronado Domenge; Justin Boga
- Web page: https://patentgrep.com/patent/US11442208B2

## CPC

- B29D 11/00788: {Producing optical films}
- G02B 5/20: Filters (polarising elements G02B5/30)
- B29C 55/023: {using multilayered plates or sheets}
- B29D 11/00634: {Production of filters}
- G02B 1/111: using layers comprising organic materials
- G02B 1/115: Multilayers
- G02B 5/22: Absorbing filters {(G02B5/201 - G02B5/208 take precedence)}
- B29C 48/08: flexible, e.g. films
- B29C 55/18: by squeezing between surfaces, e.g. rollers
- B29L 2011/0066: {Optical filters}
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES

## Abstract

A method of making an optical filter film with varying optical properties includes the step of drawing a multilayer polymeric preform into an optical filter and varying at least one environmental condition being a member of the group including of heat, pressure, tension, and a drawing speed, the at least one environmental condition being varied over time or over a distance, or both, and causing a variation in layer thickness within the optical filter. The preform may be drawn through a furnace subjecting the preform to a heating power that varies across a width of the furnace or over time or both across the width and over time. The preform may also be drawn through the furnace while the drawing speed varies across a width of the furnace or over time or both across the width and over time.

## Claims

### Claim 1

A method of making an optical filter film with varying optical properties, the method comprising the step of drawing a multilayer polymeric preform into an optical filter and varying at least one environmental condition being a member of the group consisting of heat, pressure, tension, and a drawing speed, the at least one environmental condition being varied over time or over a distance, or both, and causing a variation in layer thickness within the optical filter.

### Claim 2 (depends on 1)

The method of claim 1, wherein the at least one environmental condition is heat, wherein the preform is drawn through a furnace subjecting the preform to a heating power that varies across a width of the furnace or over time or both across the width and over time.

### Claim 3 (depends on 2)

The method of claim 2, further comprising the steps of:
positioning heaters on opposite sides of the preform, wherein the opposite sides of the preform extend along a drawing direction of the preform, the width of the furnace extending across the drawing direction, and
drawing the preform through the furnace in the drawing direction.

### Claim 4 (depends on 3)

The method of claim 3, wherein at least one of the heaters subjects the preform to a heating power varying along the width of the furnace.

### Claim 5 (depends on 4)

The method of claim 4, wherein the heating power is varied by positioning the at least one heater to enclose an acute angle with the preform.

### Claim 6 (depends on 4)

The method of claim 4, wherein the heating power is varied by heating the at least one heater to different temperatures along the width of the furnace.

### Claim 7 (depends on 2)

The method of claim 2, further comprising the step of changing the heating power of the furnace at least locally over time while the preform is being drawn through the furnace.

### Claim 8 (depends on 1)

The method of claim 1, wherein the at least one environmental condition is a drawing speed, wherein the preform is drawn through a furnace while the drawing speed of drawing the preform through the furnace varies across a width of the furnace or over time or both across the width and over time, thereby producing a multilayer film with thinner film layers in zones exposed to the higher drawing speed than in zones exposed to the lower drawing speed that have thicker film layers.

### Claim 9 (depends on 8)

The method of claim 8, wherein the drawing speed is greater on one side of the width of the furnace than on an opposite side.

### Claim 10 (depends on 8)

The method of claim 8, wherein the drawing speed is greater in a central portion of the width of the furnace than on lateral sides.

### Claim 11 (depends on 8)

The method of claim 8, wherein the drawing speed alternates over time between a lower drawing speed and a higher drawing speed.

### Claim 12 (depends on 8)

The method of claim 8, further comprising the step of cutting out at least one piece from the multilayer film in a border region forming a transitional area from one of the zones with the thinner film layers to one of the zones with the thicker film layers.

### Claim 13 (depends on 1)

The method of claim 1, wherein the at least one environmental condition is heat and tension, wherein the preform is drawn through a furnace subjecting the preform to a heating power to form an intermediate filter film, further comprising the step of exposing the intermediate filter film to heat in a specified location and to a tension force in at least a longitudinal or lateral direction of the intermediate filter film, and stretching the intermediate filter film until the layer thickness is permanently reduced in the specified location to form the optical filter having a locally reduced layer thickness.

### Claim 14 (depends on 13)

The method of claim 13, wherein the step of stretching the intermediate filter film is performed while the intermediate filter film is still hot after passing through the furnace.

### Claim 15 (depends on 1)

The method of claim 1, wherein the multilayer polymeric preform includes preform layers of uneven thicknesses.

### Claim 16 (depends on 1)

The method of claim 1, wherein the multilayer polymeric preform has a wedge-shaped or trapezoidal cross-section.

### Claim 17 (depends on 1)

The method of claim 1, wherein the optical filter produced by drawing the multilayer polymeric preform is an intermediate optical filter and wherein step of varying at least one environmental condition is performed after the step of drawing by placing the intermediate optical filter in a customized mold or press and by heating the filter film.

### Claim 18 (depends on 17)

The method of claim 17, comprising the further step of applying, via the mold or press, a spatially varying pressure to various parts of the intermediate optical filter and effecting a change in thickness to form a final optical filter.

### Claim 19 (depends on 17)

The method of claim 17, wherein the mold or press has curved surfaces, the method comprising the further step of applying, via the mold or press, a pressure to the intermediate optical filter and effecting a change in shape to form a bent or domed final optical filter.