Patent ID: 8429936

Claim:
A method for manufacturing a glass substrate with reduced compaction comprising: flowing a molten glass over converging forming surfaces to form a glass ribbon, the forming surfaces converging adjacent a lower apex; cooling the glass ribbon at a first rate such that an average rate R of viscosity change with distance is equal to or greater than 6.0 meter −1 , where R is given by: R =(log 10 (μ final thickness /poise)−log 10 (μ apex /poise))/ D where: (a) μ apex is the viscosity in poise at a centerline of the glass ribbon at the lower apex, (b) μ final thickness is the viscosity in poise at the centerline where the glass ribbon has reached a final thickness, (c) D is the distance along the centerline between said two viscosities; cooling the glass ribbon at a second rate such that as the viscosity at the centerline of the glass sheet increases from 10 11 poise to 10 16 poise, an average rate R 11-16 of viscosity change with distance is less than or equal to 4.0 meter −1 , where R 11-16 is given by: R 11-16 =5 /D 11-16 and where D 11-16 is the distance along the centerline between said two viscosities; and separating the glass substrate from the glass ribbon at a score line.