Process for laminating thin glass laminates
A process for producing glass laminates including at least one sheet of glass having a thickness not exceeding 1.0 mm with reduced optical distortion and shape consistency. A pre-laminate stack of two glass sheets and a polymer interlayer are stacked between two buffer plates that are formed nominally to the desired shape of the laminate mold. The pre-laminate stack is held between the buffer plates while a vacuum is applied to the edges of the pre-laminate stack and the stack is heated to a temperature somewhat above the softening temperature of the interlayer to de-air and tack the interlayer to the two glass sheets forming the desired shaped laminate with reduced optical distortion.
1. A process of forming a glass laminate characterized by the steps of:
providing a first buffer plate having a first forming surface, the first forming surface having a shape that conforms to a desired final shape of the glass laminate;
providing a second buffer plate having a second forming surface, the second forming surface having a shape that conforms to the desired final shape of the glass laminate;
providing a first glass sheet, a second glass sheet and a polymer interlayer, wherein at least one of the first glass sheet and the second glass sheet has a thickness not exceeding 1 mm;
stacking the first glass sheet on the first forming surface of the first buffer plate such that a first surface of the first glass sheet is in direct contact with the first forming surface;
stacking the interlayer on a second surface of the first glass sheet, wherein the second surface is opposite the first surface of the first glass sheet;
stacking the second glass sheet on the interlayer opposite the first glass sheet;
stacking the second buffer plate on the second glass sheet such that the second forming surface is in direct contact with a surface of the second glass sheet, wherein the surface of the second glass sheet is opposite the interlayer, forming an assembled stack;
clamping a vacuum ring to at least a portion of at least one peripheral edge of the assembled stack;
applying a vacuum to the peripheral edge of the assembled stack through the vacuum ring;
heating the assembled stack with the vacuum ring attached thereto in an oven to a soak temperature at or above the softening temperature of the interlayer;
maintaining the vacuum and the soak temperature for a period of time (a soak time) sufficient to de-air the interlayer, tack the interlayer to the first glass sheet and the second glass sheet, and form the first and second glass sheets and the interlayer to the first and second forming surfaces;
removing the assembled stack from the oven; and
removing the buffer plates from the glass laminate, wherein the glass laminate has the desired final shape.
2. The process of claim 1 , wherein both the first glass sheet and the second glass sheet have a thickness not exceeding 1 mm.
3. The process of claim 1 , wherein both the first glass sheet and the second glass sheet are chemically strengthened glass sheets.
4. The process of claim 1 , wherein the interlayer is formed of a polymer selected from the group consisting of standard polyvinyl butyral (PVB), acoustic PVB, ethylene vinyl acetate (EVA), thermoplastic polyurethane (TPU), and an ionomer.
5. The process of claim 1 , wherein maintaining the vacuum through the vacuum ring and the soak temperature for the soak time comprises placing the assembled stack with the vacuum ring clamped thereto in an autoclave at a pressure not exceeding 180 psi during the soak time.
6. The process of claim 1 , wherein the soak temperature does not exceed about 150° C.
7. The process of claim 1 , wherein the soak temperature does not exceed about 125° C.
8. The process of claim 1 , wherein the soak temperature is in a range from about 100° C. to about 150° C.
9. The process of claim 1 , wherein the vacuum applied to the peripheral edge of the assembled stack does not exceed about −0.9 bar.
10. The process of claim 9 , wherein the vacuum applied to the peripheral edge of the assembled stack does not exceed about −0.7 bar.
11. The process of claim 10 , wherein the vacuum applied to the peripheral edge of the assembled stack does not exceed about −0.6 bar.
12. The process of claim 10 , wherein the vacuum applied to the peripheral edge of the assembled stack is in a range from about −0.2 to about −0.6 bar.
13. The process of claim 1 , wherein heating comprises heating the assembled stack to a soak temperature not exceeding 150° C.
14. The process of claim 1 , further comprising:
placing the assembled stack with the vacuum ring clamped thereto in an autoclave after maintaining the vacuum and the soak temperature for the soak time; and
maintaining a pressure within the autoclave in a range of from about 70 psi to about 180 psi during a second soak time.
15. The process of claim 1 , wherein:
the first forming surface has a shape nominally matching a desired shape of the glass laminate to form the assembled stack; and
the second forming surface has a having shape nominally matching a desired shape of the glass laminate to form the assembled stack.
16. The process of claim 15 , wherein at least one of the first buffer plate and the second buffer plate are formed of a sheet of soda lime glass having a thickness of about 4 mm to about 6 mm.
17. The process of claim 1 , wherein at least one of the first buffer plate and the second buffer plate are formed of a sheet of soda lime glass.
18. The process of claim 1 , wherein at least one of the steps of providing a first buffer plate and providing a second buffer plate comprises the steps of:
providing a glass sheet;
bending the glass sheet prior to stacking the glass sheet such that the glass sheet has a surface having a shape nominally matching the desired final shape of the glass laminate.
19. The process of claim 18 , wherein the at least one of the first buffer plate and the second buffer plate are formed of a soda lime glass sheet having a thickness of about 4 mm to about 6 mm.
20. The process of claim 1 , wherein the desired final shape is a curved shape.