Thermal press and ultraviolet curing for display assemblies

• US 9,128,674 B2
• Filed: 07/12/2013
• Issued: 09/08/2015
• Est. Priority Date: 09/07/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Sung, Kuo-Hua, Kim, Sang Ha, Ho, Hsing Han
• Primary Examiner(s): SHENG, TOM V
• Application Number:
  US13/941,377
• Publication Number:
  US 20140071354A1
• Time in Patent Office: 788 Days
• Field of Search: 345/173, 349/12, 156/275.5, 156/295, 156/350, 156/380.9, 156/583.1
• US Class Current: 1/1
• CPC Class Codes: B32B 38/00 Ancillary operations in connection with laminating processes
• CPC Class Codes: G06F 1/1643 the display being associated to a digitizer, e.g. laptops that can be used as penpads details related to the relative motion of the display enclosure with respect to the body enclosure, e.g. to move between laptop and tablet PC configuration G06F1/1615
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means

Abstract

Methods for controlling deformation of laminated display assemblies are described. The laminated display assemblies can include flexible layers. In some embodiments, the flexible layers are sensor layers. Methods involving the use of a thermal press and ultra violet (UV) curing procedure are described. In one embodiment, a thermal press method can be performed by placing a laminated display assembly including the flexible substrate, an ink layer, an adhesive, and a cover on a temperature controlled fixture. A mechanical press can apply pressure to the top of the laminated display assembly. The mechanical press can remove any planar deformity of the flexible layer and can redistribute portions of the adhesive. Following the mechanical pressing, the laminated display assembly can be exposed to UV light to cure the adhesive and thereby fix in place the planar state of the laminated display assembly.

Claims

1. A method for planarizing a laminated display assembly, comprising:

in a non-planar state, the laminated display assembly comprises;

a substrate comprising a peripheral region and a central region,

an ink layer overlaying and in contact with at least a portion of the peripheral region, the ink layer having a thickness that creates a step between an edge of the ink layer and the central region,

an adhesive overlaying and in contact with at least a portion of the ink layer and the central region of the substrate, and

a flexible sensor layer overlaying and in contact with the adhesive, the flexible sensor layer conforming to the shape of the adhesive;

heating a portion of a thermal press to at least partially liquefy the adhesive;

applying a flattening pressure to at least the flexible sensor layer causing at least some of the at least partially liquefied adhesive to evenly redistribute between the ink layer and the central region; and

forming a planar state of the laminated display assembly by fixing in place the evenly redistributed adhesive.

2. The method as recited in claim 1, wherein the fixing in place comprises curing the adhesive subsequent to the redistribution of the at least partially liquefied adhesive.

3. The method as recited in claim 2, wherein the curing comprises:

reducing the temperature of the adhesive to a curing temperature that is less than a liquefaction temperature of the adhesive.

4. The method as recited in claim 2, wherein the curing comprises:

exposing the adhesive to ultraviolet light.

5. The method as recited in claim 1, wherein heating the adhesive comprises heating a lower portion of the thermal press.

6. The method as recited in claim 1, wherein the planar state of the laminated display assembly has less visual defects than the non-planar state of the laminated display assembly.

7. The method as recited in claim 1, wherein the substrate has a planar shape and remains in the planar shape while the flattening pressure is applied to at least the flexible sensor layer.

8. The method as recited in claim 1, wherein forming the planar state of the laminated display assembly begins before the laminated display assembly rebounds to a non-planar state.

9. A thermal press for pressing a laminated stack up, the laminated stack up comprising:

a stepped layer overlaying a portion of a substrate layer, the stepped layer having a thickness creating a step between an edge of the stepped layer and the substrate layer,

an adhesive disposed on and in contact with at least a portion of the stepped layer and the substrate layer, wherein the adhesive at least partially conforms in shape to the step when the adhesive is in an initial state,

a flexible layer disposed on and in contact with the adhesive, wherein the flexible layer comprises a bent region corresponding to the step when the laminated stack up is in the initial state,

the thermal press comprising;

a lower portion having a first flat surface arranged to accept a bottom surface of the laminated stack up placed thereon, and a heating element arranged to heat the adhesive to a temperature sufficient to transform the adhesive to at least a partially liquid state;

an upper portion having a second flat surface arranged to be placed on a top surface of the laminated stack up; and

a mechanical press arranged to apply a flattening pressure on the upper portion, wherein the flattening pressure flattens the bent region and redistributes at least a portion of the at least partially liquefied adhesive.

10. The thermal press of claim 9, further comprising:

an ultraviolet light source arranged to set a planar state of the laminated stack up by curing the adhesive while the bent region remains flattened.

11. The thermal press as recited in claim 10, wherein the thermal press is configured to cure the adhesive while the flattening pressure is applied to the laminated stack up.

12. The thermal press as recited in claim 11, wherein at least one of the upper and lower portions have an ultraviolet light transparent portion.

13. The thermal press of claim 9, wherein the upper portion comprises at least one pad to evenly distribute the flattening pressure across at least the top surface of the laminated stackup.

14. The thermal press of claim 9, further comprising at least one alignment pin arranged to maintain a position of the laminated stack up relative to the thermal press.

15. The thermal press of claim 14, wherein the at least on alignment pin is arranged to properly position the upper portion on the laminated stack up.

16. A non-transitory computer readable medium for storing computer code executed by a processor in a computer for operating a thermal press for pressing a laminated stack up,

the laminated stack up comprising a stepped layer, an adhesive and a flexible layer, the thermal press comprising:

a lower portion arranged to support the laminated stack up and comprising a heating element,

an upper portion arranged to be placed on top of the laminated stack up, and

a mechanical press arranged to apply a pressure to the upper portion toward the lower portion,

the non-transitory computer readable medium comprising;

computer code for causing the heating element to at least partially liquefy the adhesive; and

computer code for causing the mechanical press to apply the pressure to the flexible layer causing a bent portion corresponding to a step of the stepped layer to flatten and causing at least some of the at least partially liquefied adhesive to evenly redistribute between the stepped layer and the flexible layer.

17. The non-transitory computer readable medium of claim 16, wherein the thermal press further comprises:

an ultraviolet light source arranged to set a flattened shape of the flexible layer within the laminated stack up by curing the adhesive while the bent portion remains flattened.

18. A display assembly for a portable electronic device, comprising:

a rigid cover having a central viewing region and a peripheral region;

an opaque ink layer disposed on the peripheral region, wherein the opaque ink layer includes a step having a step height corresponding to a thickness of the opaque ink layer;

an adhesive disposed on at least a portion of the opaque ink layer and the central viewing region of the rigid cover; and

a flexible sensor layer disposed on the adhesive, wherein the adhesive is distributed between the flexible sensor layer and the opaque ink layer and the central viewing region of the rigid cover such that the flexible sensor layer has a substantially planar shape proximate to the step.

19. The display assembly as recited in claim 18, wherein the opaque ink layer frames the viewing region of the rigid cover.

20. The display assembly as recited in claim 18, wherein the flexible sensor layer is configured to receive touch input from a user of the portable electronic device and send electronic information corresponding to the touch input to at least one component of the portable electronic device.

21. The display assembly as recited in claim 18, wherein the flexible sensor layer comprises a flexible polymer material.

22. The display assembly as recited in claim 18, wherein the adhesive is sized and shaped to maintain the substantially planar shape of the flexible sensor layer.