# US 11,028,291 B2 · Film comprising a strippable sacrificial layer for reduction of surface defects in a substrate

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- Number: US 11,028,291 B2
- Document ID: US11028291B2
- Status: Granted
- Kind: B2
- Application number: 16/129,222
- Filed: 2018-09-12
- Published: 2019-03-21
- Granted: 2021-06-08
- Earliest claimed: 2011-03-17
- Assignees: DuPont Teijin Films U.S. Limited Partnership
- Applicants: DuPont Teijin Films U.S. Limited Partnership
- Inventors: Robert Eveson; Karl Rakos; Damian Peter Tuffin; Dominic Hoy
- Web page: https://patentgrep.com/patent/US11028291B2

## CPC

- C09J 7/405: {characterised by the substrate of the release liner}
- B32B 7/06: permitting easy separation
- B32B 27/308: {comprising acrylic (co)polymers}
- B32B 27/36: comprising polyesters
- B32B 7/04: Interconnection of layers
- B32B 27/08: of synthetic resin
- B32B 27/30: comprising vinyl {(co)polymers; comprising acrylic (co)polymers}
- B32B 37/15: with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state
- B32B 37/153: {at least one layer is extruded and immediately laminated while in semi-molten state}
- B32B 38/10: Removing layers, or parts of layers, mechanically or chemically
- B32B 2250/02: 2 layers
- B32B 2250/03: 3 layers
- B32B 2250/24: All layers being polymeric
- B32B 2250/40: Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
- B32B 2307/308: Heat stability
- B32B 2307/40: having particular optical properties
- B32B 2307/412: Transparent
- B32B 2307/518: bi-axially
- B32B 2307/538: Roughness
- B32B 2307/734: Dimensional stability
- B32B 2307/748: Releasability
- B32B 2333/00: Polymers of unsaturated acids or derivatives thereof
- B32B 2367/00: Polyesters, e.g. PET, i.e. polyethylene terephthalate
- B32B 2457/00: Electrical equipment
- B32B 2457/12: Photovoltaic modules
- B32B 2457/14: Semiconductor wafers
- B32B 2457/20: Displays, e.g. liquid crystal displays, plasma displays
- C08F 20/04: Acids, Metal salts or ammonium salts thereof
- C08F 20/06: Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
- C08F 22/02: Acids; Metal salts or ammonium salts thereof {, e.g. maleic acid or itaconic acid}
- C08L 33/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- C09K 2323/06: Substrate layer characterised by chemical composition
- G02B 1/10: Optical coatings produced by application to, or surface treatment of, optical elements (G02B1/08 takes precedence)
- Y10T 156/1195: Delaminating from release surface
- Y10T 428/24355: Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
- Y10T 428/265: 1 mil or less
- Y10T 428/266: of base or substrate
- Y10T 428/31681: Next to polyester, polyamide or polyimide [e.g., alkyd, glue, or nylon, etc.]
- Y10T 428/31786: Of polyester [e.g., alkyd, etc.]
- Y10T 428/31797: Next to addition polymer from unsaturated monomers
- C09J: ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES (preparation of glue or gelatine C09H)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A coextruded biaxially oriented composite film comprising a polyester substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer, wherein said strippable sacrificial layer comprises an ethylene-methacrylic acid (EMAA) copolymer.

## Claims

### Claim 1

A coextruded biaxially oriented composite film comprising a polyethylene terephthalate (PET) substrate layer and disposed on one or both surfaces thereof an ethylene-methacrylic acid (EMAA) copolymer strippable sacrificial layer, wherein the strippable sacrificial layer has a thickness in the range of from 2 to 200 μm, and the EMAA copolymer has a melt flow index of 0.5 to about 50 g/10 min, and wherein the EMAA copolymer is not an ionomer and does not contain metal ions.

### Claim 2 (depends on 1)

The film according to claim 1 wherein the methacrylic acid is present in the EMAA copolymer in the range of from about 2 to about 15 wt % of the copolymer.

### Claim 3 (depends on 1)

The film according to claim 1 wherein a thickness of the PET substrate layer is in the range of from about 5 to about 500 μm.

### Claim 4 (depends on 1)

The film according to claim 1 wherein the adhesive strength of the strippable sacrificial layer to the PET substrate is such that the peel force is in the range of from about 20 to about 250 gF.

### Claim 5 (depends on 1)

The film according to claim 1 wherein the PET substrate has a haze of no more than 15% and/or a total luminous transmission (TLT) for light in the visible region (400 nm to 700 nm) of at least 80%.

### Claim 6 (depends on 1)

The film according to claim 1 wherein the PET substrate exhibits a shrinkage of no more than 3% at 150° C. over 30 minutes.

### Claim 7 (depends on 1)

The film according to claim 1 wherein the PET substrate exhibits an Ra of less than 10 nm upon removal of the strippable sacrificial layer(s).

### Claim 8 (depends on 1)

A method of protecting a surface of a substrate from damage and/or contamination and/or debris during transport and/or storage, said method comprising the steps of:
(i) providing a coextruded composite film comprising a polyethylene terephthalate (PET) substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer according to claim 1; and
(ii) removing said strippable sacrificial layer from said PET substrate prior to use or further processing of said substrate.

### Claim 9 (depends on 1)

A method of reducing defects in a functional layer applied to a substrate, said method comprising the steps of:
(i) providing a coextruded composite film comprising a polyethylene terephthalate (PET) substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer according to claim 1;
(ii) removing said strippable sacrificial layer from said PET substrate; and
(iii) applying said functional layer to said PET substrate.

### Claim 10 (depends on 9)

The method according to claim 9 wherein said functional layer is a conductive layer or barrier layer.

### Claim 11 (depends on 1)

A method of using an ethylene-methacrylic acid (EMAA) copolymer layer as a strippable sacrificial layer in a coextruded biaxially oriented composite film further comprising a polyethylene terephthalate (PET) substrate layer, as defined in claim 1, wherein said EMAA copolymer layer is disposed on one or both surfaces of said polyester substrate layer, said method consisting of stripping the EMAA copolymer layer from the PET substrate layer, and wherein the EMAA copolymer is not an ionomer and does not contain metal ions.

### Claim 12 (depends on 1)

The film according to claim 1, wherein said one or both surfaces exhibit(s) a number (NGS) of gel-like defects with a peak height of greater than about 0.25 μm and less than about 30 μm of no more than 10 per 31×33 cm area of film surface upon removal of the strippable sacrificial layer, and/or
wherein the improvement (Δ-NGS) in the parameter (NGS), relative to a control PET substrate manufactured without the strippable sacrificial layer, is at least 2, wherein Δ-NGS is defined as:
[NGS of said control PET substrate]/[(NGS) of surface of said PET substrate layer upon removal of said strippable sacrificial layer].

### Claim 13 (depends on 1)

The film according to claim 1, wherein said one or both surfaces exhibit(s) a number (NDT) of defects with a vertical amplitude, orthogonal to the film plane, of greater than about 0.25 μm and less than about 30 μm above and/or below the mean surface of no more than 1000 per 31×33 cm area of film surface upon removal of the strippable sacrificial layer, and/or
wherein the improvement (Δ-NDT) in the parameter (NDT), relative to a control PET substrate manufactured without the strippable sacrificial layer, is at least 2, wherein Δ-NDT is defined as:
[NDT of said control PET substrate]/[(NDT) of surface of said PET substrate layer upon removal of said strippable sacrificial layer].

### Claim 14 (depends on 1)

The film according to claim 1, wherein said one or both surfaces exhibit(s) a number (NPP) of pinch-point peaks with a peak height of greater than about 0.25 μm and less than about 30 μm of no more than 100 per 31×33 cm area of film surface upon removal of the strippable sacrificial layer, and/or
wherein the improvement (Δ-NPP) in the parameter (NPP), relative to a control PET substrate manufactured without the strippable sacrificial layer, is at least 2, wherein Δ-NPP is defined as:
[NPP of said control PET substrate]/[(NPP) of surface of said PET substrate layer upon removal of said strippable sacrificial layer].

### Claim 15 (depends on 1)

An electronic or opto-electronic device, optical film, medical device or decorative film derived from a coextruded biaxially oriented composite film as defined in claim 1 from which said strippable sacrificial layer has been removed.

### Claim 16 (depends on 15)

The electronic or opto-electronic device according to claim 15 comprising a polyethylene terephthalate (PET) substrate layer derived from the coextruded composite film comprising said PET substrate layer and disposed on one or both surfaces thereof a strippable sacrificial layer, wherein said strippable sacrificial layer is removed from said composite film prior to or during incorporation into or manufacture of said electronic or opto-electronic device.

### Claim 17 (depends on 15)

The electronic or opto-electronic device according to claim 15, further comprising a barrier or conductive layer, wherein said barrier or conductive layer is disposed on said PET substrate in said electronic or opto-electronic device.

### Claim 18 (depends on 15)

The electronic or opto-electronic device according to claim 15, selected from electroluminescent (EL) display devices, electrophoretic display devices, photovoltaic cells and semiconductor devices.

### Claim 19 (depends on 15)

The device according to claim 15, wherein said one or both surfaces exhibit(s) a number (NGS) of gel-like defects with a peak height of greater than about 0.25 μm and less than about 30 μm of no more than 10 per 31×33 cm area of film surface upon removal of the strippable sacrificial layer, and/or
wherein the improvement (Δ-NGS) in the parameter (NGS), relative to a control PET substrate manufactured without the strippable sacrificial layer, is at least 2, wherein Δ-NGS is defined as:
[NGS of said control PET substrate]/[(NGS) of surface of said PET substrate layer upon removal of said strippable sacrificial layer].

### Claim 20 (depends on 15)

The device according to claim 15, wherein said one or both surfaces exhibit(s) a number (NDT) of defects with a vertical amplitude, orthogonal to the film plane, of greater than about 0.25 μm and less than about 30 μm above and/or below the mean surface of no more than 1000 per 31×33 cm area of film surface upon removal of the strippable sacrificial layer, and/or
wherein the improvement (Δ-NDT) in the parameter (NDT), relative to a control PET substrate manufactured without the strippable sacrificial layer, is at least 2, wherein Δ-NDT is defined as:
[NDT of said control PET substrate]/[(NDT) of surface of said PET substrate layer upon removal of said strippable sacrificial layer].

### Claim 21 (depends on 15)

The device according to claim 15, wherein said one or both surfaces exhibit(s) a number (NPP) of pinch-point peaks with a peak height of greater than about 0.25 μm and less than about 30 μm of no more than 100 per 31×33 cm area of film surface upon removal of the strippable sacrificial layer, and/or
wherein the improvement (Δ-NPP) in the parameter (NPP), relative to a control PET substrate manufactured without the strippable sacrificial layer, is at least 2, wherein Δ-NPP is defined as:
[NPP of said control PET substrate]/[(NPP) of surface of said PET substrate layer upon removal of said strippable sacrificial layer].