Method of Bonding a Film to a Curved Substrate

• US 20110146893A1
• Filed: 06/07/2007
• Published: 06/23/2011
• Est. Priority Date: 06/13/2006
• Status: Active Grant

• Current Assignee: Centre National De La Recherche Scientifique, Essilor International SA
• Original Assignee: Essilor International SA
• Inventors: Marty, Antoine, Lefillastre, Paul
• Granted Patent: US 8,628,634 B2
• Time in Patent Office: Days
• US Class Current: 156/212
• CPC Class Codes: B29C 2791/006 Using vacuum
• CPC Class Codes: B29C 2791/007 Using fluid under pressure
• CPC Class Codes: B29C 51/08 Deep drawing or matched-mould forming, i.e. using mechanical means only
• CPC Class Codes: B29C 51/10 Forming by pressure difference, e.g. vacuum
• CPC Class Codes: B29C 51/14 using multilayered preforms or sheets
• CPC Class Codes: B29C 63/0073 of non-flat surfaces, e.g. curved, profiled B29C63/042 takes precedence
• CPC Class Codes: B29D 11/00903 on the surface
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2069/00 Use of PC, i.e. polycarbonates or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2079/08 PI, i.e. polyimides or derivatives thereof
• CPC Class Codes: B29L 2011/0016 Lenses
• CPC Class Codes: Y10T 156/1028 by bending, drawing or stretch forming sheet to assume shape of configured lamina while in contact therewith
• CPC Class Codes: Y10T 156/1031 with preshaping of lamina

Abstract

A method of bonding a film (2) to a curved substrate (1) comprises preforming the film by applying a pneumatic pressure difference between two sides of the film and by heating said film. An intermediate shape is then conferred on the film, which is suitable for applying the film against a curved face of the substrate. This application is carried out, on the one hand, by keeping the film m the intermediate shape by means of an adjusted pressure difference applied between the two sides of the film and, on the other hand, by pressing the substrate against the film by means of a movable support (12-14). Such a method is used to obtain a defect-free ophthalmic lens with a film bonded to it.

Claims

1. Method of bonding a film (2) having a substantially plane initial shape to a curved face of a substrate (1), the method comprising the following steps:

a) when the film is at a temperature above 40°

C., a peripheral edge of the film (2) is held firmly and a pneumatic pressure difference is applied between two sides of the film until an application face (S2) of said film becomes curved with a curvature greater than an average curvature of the face (S1) of the substrate;

b) when the temperature of the film has dropped below 40°

C., the pneumatic pressure difference applied between the two sides of the film is adjusted so that the curvature of the application face (S2) of the film becomes approximately equal to or less than the curvature of the face (S1) of the substrate; and

c) while maintaining the pneumatic pressure difference adjusted at step b), the face (S1) of the substrate is pressed against the application face (S2) of the film until complete contact is established between the film and the face of the substrate, a layer of an adhesive (3) being placed between the film (2) and the substrate (1).

2. Method according to claim 1, in which step a) is carried out while simultaneously heating the film (2), and step b) is carried out when the temperature of the film is substantially equal to the ambient temperature.

3. Method according to claim 1 or 2, in which the temperature of the film during step a) is between 80°

C. and 180°

C.

4. Method according to any one of the preceding claims, in which the pneumatic pressure difference applied in step a) between the two sides of the film is between 0.1 bar and 4.0 bar.

5. Method according to claim 4, in which the pneumatic pressure difference applied in step a) between the two sides of the film is between 0.1 bar and 1.0 bar.

6. Method according to any one of the preceding claims, in which, in step c), the face (S1) of the substrate is pressed against the application face (S2) of the film with a rate of relative movement of between 0.1 and 1.0 mm/s.

7. Method according to any one of claims 1 to 6, in which the face (S1) of the substrate is convex and in which:

in step a), the pneumatic pressure difference is applied between the two sides of the film so that the application face (S2) of the film becomes concave with a curvature greater than the curvature of the face (S1) of the substrate; and

in step b), the pneumatic pressure difference applied between the two sides of the film is reduced so that the application face (S2) of the film remains concave and the curvature of said application face becomes less than the curvature of the face (S1) of the substrate.

8. Method according to claim 7, in which the pneumatic pressure difference applied between the two sides of the film after step b) is between 0.05 bar and 0.3 bar.

9. Method according to any one of claims 1 to 6, in which, in step a), the pneumatic pressure difference is applied between the two sides of the film so that the application face (S2) of the film becomes concave with a curvature greater than the curvature of the face (S1) of the substrate and in which step b) comprises the following two substeps:

b1) when the temperature of the film has dropped below 40°

C., the pneumatic pressure difference applied between the two sides of the film is reduced so that the application face (S2) of the film remains concave and the curvature of said application face becomes substantially equal to the curvature of the face (S1) of the substrate; and

then

b2) the pneumatic pressure difference is modified by reversing the sign of said pneumatic pressure difference between the two sides of the film so that the application face (S2) of the film becomes convex.

10. Method according to claim 9, in which the face (S1) of the substrate is convex and in which the application face (S2) of the film becomes concave again when said face of the substrate is progressively pressed against said application face of the film in step c).

11. Method according to claim 9 or 10, in which the pneumatic pressure difference applied between the two sides of the film after step b1) is between 0.05 bar and 0.3 bar.

12. Method according to any one of claims 9 to 11, in which the pneumatic pressure difference applied between the two sides of the film after step b2) is between 0.05 bar and 0.5 bar in absolute value.

13. Method according to any one of the preceding claims, in which, after step c), the substrate (1) is held pressed against the film (2) for a time of between 0.5 seconds and 2 minutes.

14. Method according to any one of the preceding claims, in which the layer of adhesive (3) is arranged on the application face (S2) of the film before step c).

15. Method according to any one of the preceding claims, in which the layer of adhesive (3) comprises a pressure-sensitive adhesive or a UV-curable or heat-curable adhesive.

16. Method according to any one of the preceding claims, in which the substrate (1) comprises an optical lens.

17. Method according to claim 16, in which the substrate (1) comprises an ophthalmic lens.

18. Method according to any one of the preceding claims, in which the film (2) comprises a material based on polyethylene terephthalate, cellulose triacetate, polyvinyl alcohol, a polyimide, polyethylene naphthalate or polycarbonate.

19. Method according to any one of the preceding claims, in which the film (2) includes a functional coating (4) on an external face (S3) of said film opposite from the application face (S2).

20. Method according to claim 19, in which the functional coating (4) comprises an anti-reflection coating, an anti-soiling coating, an anti-scratch coating, a hydrophobic coating or a combination of some of said coatings.

21. Method according to any one of the preceding claims, in which the film (2) includes an array of cells (20) juxtaposed parallel to one face of said film, neighbouring cells of said array being separated by walls (21) substantially perpendicular to said face of the film.

22. Method according to any one of the preceding claims, in which steps a) to c) are carried out using a device comprising:

a sealed chamber (10) provided with a system (11) for fastening the peripheral edge of the film (1) so as to hermetically seal said chamber with said film;

means (16) for heating the film fastened to the chamber and means for controlling the temperature of the film fastened to the chamber;

means (15) for varying the pneumatic pressure inside the chamber and means for controlling said pneumatic pressure relative to the pressure outside the chamber;

a substrate support (12) placed in the chamber; and

means (13, 14) for moving the substrate support inside the chamber, which are designed to press the substrate against the film,

in which steps a) and b) are carried out by actuating the means (15) for varying and controlling the pneumatic pressure inside the chamber and step c) is carried out by actuating the means for moving the substrate support (13, 14).

23. Device comprising:

a sealed chamber (10) provided with a system (11) for fastening a peripheral edge of a film so as to hermetically seal said chamber with said film;

means (16) for heating the film when fastened to the chamber;

means (15) for varying a pneumatic pressure inside the chamber and means for controlling said pneumatic pressure relative to a pressure outside the chamber;

a substrate support (12) placed in the chamber; and

means (13, 14) for moving the substrate support inside the chamber, which are designed to press the substrate against the film,

the device being adapted for implementing a method according to any one of claims 1 to 22.

24. Device according to claim 23, which further includes an automatic control system designed to control the means (15) for varying and controlling the pneumatic pressure inside the chamber, the means for varying and controlling the heating of the film and the means (13, 14) for moving the substrate support.