Method of forming leveraged poromeric polishing pad
The invention provides a method of forming porous polyurethane polishing pad that includes feeding liquid polyurethane onto a web sheet with a doctor blade while back tensioning the web. Coagulating liquid polyurethane onto the web sheet forms a two-layer substrate. The two-layer substrate has a porous matrix wherein the porous matrix has large pores extending upward from a base surface and open to an upper surface. Spring-arm sections connect lower and upper sections of the large pores.
1. A method of forming a porous polyurethane polishing pad comprising:
feeding liquid polyurethane onto a web sheet with a doctor blade while back tensioning the web with compression into the web sheet to prevent the liquid polyurethane from leaking opposite of a web direction;
coagulating liquid polyurethane onto the web sheet to form a two-layer substrate, the two-layer substrate being a porous body on the web sheet, the porous body having a porous matrix, wherein the porous matrix has large pores extending upward from a base surface and open to an upper surface, the large pores being interconnected with tertiary pores, a portion of the large pores being open to a top polishing surface;
pulling the two layer substrate over a touch roll to compress the porous body and pull the porous body forming to deform the porous matrix in a shear zone, after passing the shear zone, at least a portion of the large pores extending to the top polishing surface have a lower and upper sections with a vertical orientation, vertical direction being a direction orthogonal to the web sheet and spring-arm sections connecting the lower and upper sections, the spring-arm sections all being in the web direction and having an angle from an upward vertical between 15 and 90 degrees wherein the spring-arm sections combine to increase compressibility and contact area of the polishing pad;
curing the two layer substrate to cure the porous body and lock the porous body with the spring-arm-sections connecting the lower and upper sections; and
forming the cured porous body into the polishing pad, the polishing pad containing the spring-arm-sections connecting the lower and upper sections.
2. The method of claim 1 including the additional steps of buffing the porous body to increase size of large pores open at a polishing surface of the polishing pad and embossing the porous body to create a groove pattern.
3. The method of claim 2 wherein the shear zone elongates the large pores in a non-vertical direction to decrease a diameter of the spring-arm sections.
4. The method of claim 2 wherein the shear zone forms the spring-arm sections having an angle between 25 and 80 degrees as measured from an upward vertical direction.
5. The method of claim 1 wherein the back blade pushes the web against a rotating roll to apply back tension with the web and a knife blade regulates thickness of the porous body without applying significant back tensioning of the porous body.
6. A method of forming a porous polyurethane polishing pad comprising:
feeding liquid polyurethane onto a web sheet with a doctor blade while back tensioning the web with compression into the web sheet to prevent the liquid polyurethane from leaking opposite of a web direction;
coagulating liquid polyurethane onto the web sheet to form a two-layer substrate, the two-layer substrate being a porous body on the web sheet, the porous body having a porous matrix, wherein the porous matrix has large pores extending upward from a base surface and open to an upper surface, the large pores being interconnected with tertiary pores, a portion of the large pores being open to a top polishing surface;
pulling the two layer substrate over a touch roll to compress the porous body and pull the porous body forming to deform the porous matrix in a shear zone, after passing the shear zone, at least a portion of the large pores extending to the top polishing surface have a lower and upper sections with a vertical orientation, vertical direction being a direction orthogonal to the web sheet and spring-arm sections connecting the lower and upper sections, the spring-arm sections all being in the web direction and having an angle from an upward vertical between 15 and 90 degrees wherein the spring-arm sections combine to increase compressibility and contact area of the polishing pad;
forming middle-sized pores having a vertical orientation adjacent the spring-arm sections of the large pores and small pores between the middle-sized pores;
curing the two layer substrate to cure the porous body and lock the porous body with the spring-arm-sections connecting the lower and upper sections; and
forming the cured porous body into the polishing pad, the polishing pad containing the spring-arm-sections connecting the lower and upper sections.
7. The method of claim 6 including the additional steps of buffing the porous body to increase size of large pores open at a polishing surface of the polishing pad and embossing the porous body to create a groove pattern.
8. The method of claim 7 wherein the shear zone elongates the large pores in a non-vertical direction to decrease a diameter of the spring-arm sections.
9. The method of claim 7 wherein the shear zone forms the spring-arm sections having an angle between 25 and 80 degrees as measured from an upward vertical direction.
10. The method of claim 6 wherein the back blade pushes the web against a rotating roll to apply back tension with the web and a knife blade regulates thickness of the porous body without applying significant back tensioning of the porous body.