Thin glass substrate, method and apparatus for its production

A method for producing a glass substrate, comprising:

• melting a glass;
• forming the glass into the glass substrate;
• and
• adjusting a viscosity of the glass prior to fully forming the glass into the glass substrate so that:
• the viscosity of the glass η immediately upstream of a flow rate control component has a maximum viscosity deviation (Δlg η/dPa·s) equal to at most 0.1;
• and
• the viscosity of the glass η1 downstream of the flow rate control component at a distance y1 that is ≤1.5 m from a location immediately downstream of the flow rate control component has a maximum viscosity deviation (Δlg η1/dPa·s) equal to at most 0.2 and the following equation applies:
• lg η1(y1)/dPa·s=(lg η01/dPa·s+a1(y1))
• where η01 is a value of glass viscosity at y=0 m and lg η01 is a logarithm of the glass viscosity η1 at y=0 m,
• 0 m≤y1≤1.5 m being a distance of a location immediately downstream of the flow rate control component that is located at y=0 m,
• 3.75≤lg η01/dPa·s≤4.5 being a range of viscosities to be adjusted at y=0 m, and
• a1(y1)=1.00/m*y1 being a positive change in the range of viscosities to be adjusted over 0 m≤y1≤1.5 m.