Driving method for polymer stabilized and polymer free liquid crystal displays

Claim 1

A method of operating a liquid crystal display device having a first substrate having a plurality of substantially parallel address lines disposed thereon, and a second substrate having a plurality of substantially parallel address lines disposed thereon, said first and second substrates operatively disposed in facing, parallel relationship so that said address lines on said first substrate are disposed at an angle with respect to the address lines of said second substrate to form a plurality of crossover points therewith, each crossover point defining a picture element, said method comprising the steps of: providing a layer of a liquid crystal material having a periodic modulated optical structure that reflects light, disposed between said first and second substrates, said material being switchable between a transparent state in which said material is substantially transparent, and a reflecting state which reflects light, wherein said liquid crystal material is in the reflecting state when driven by a first AC voltage level and is in the transparent state when driven by a second AC voltage level; applying a first AC voltage to at least one address line on said first substrate, said first AC voltage being between the first AC voltage level and the second AC voltage level; and applying a second AC voltage to at least one address line on said second substrate, said second AC voltage being sufficient in amplitude when applied out of phase with said first AC voltage to switch said liquid crystal material into said reflecting state, and when applied in phase with said first AC voltage to switch said liquid crystal material to said transparent state, said second AC voltage being less than a threshold voltage, said threshold voltage being an AC voltage where any voltage potential, including a zero voltage potential, applied to the liquid crystal material below the threshold voltage will not change the liquid crystal material from either the transparent state or the reflecting state.

Claim 2

A method of operating a liquid crystal display device having a first substrate having a plurality of substantially parallel address lines disposed thereon, and a second substrate having a plurality of substantially parallel address lines disposed thereon, said first and second substrates operatively disposed in facing, parallel relationship so that said address lines on said first substrate are disposed at an angle with respect to the address lines of said second substrate to form a plurality of crossover points therewith, each crossover point defining a picture element, said method comprising the steps of: providing a layer of a liquid crystal material having a periodic modulated optical structure that reflects light, disposed between said first and second substrates, said material being switchable between a transparent state in which said material is substantially transparent, and a reflecting state which reflects light, wherein said liquid crystal material is in the reflecting state when driven by a first AC voltage level and is in the transparent state when driven by a second AC voltage level; applying a first AC voltage to at least one address line on said first substrate, said first AC voltage being between the first AC voltage level and the second AC voltage level; and applying a second AC voltage to at least one address line on said second substrate, said second AC voltage being sufficient in amplitude when applied out of phase with said first AC voltage to switch said liquid crystal material into said reflecting state, and when applied in phase with said first AC voltage to switch said liquid crystal material to said transparent state, said second AC voltage being less than a threshold voltage, said threshold voltage being an AC voltage where any voltage potential, including a zero voltage potential, applied to the liquid crystal material below the threshold voltage will not change the liquid crystal material from either the transparent state or the reflecting state.

Claim 18

A method of operating a cholesteric liquid crystal display device having a first substrate having a plurality of substantially parallel address lines disposed thereon, and a second substrate having a plurality of substantially parallel address lines disposed thereon, said first and second substrates operatively disposed in facing, parallel relationship so that said address lines on said first substrate are disposed at an angle with respect to the address lines of said second substrate to form a plurality of crossover points therewith, each crossover point defining a picture element, said method comprising the steps of: providing a layer of a cholesteric liquid crystal material having periodic modulated optical structure that reflects light, disposed between said first and second substrates, said material being switchable between a transparent state in which said material is substantially transparent, and a reflecting state which reflects light, wherein said liquid crystal material reflects light due to the application of a first AC voltage level, and is transparent due the application of a second AC voltage level; said material having a first AC threshold voltage, V 1 , for beginning transition from said reflecting state to said transparent state; a first saturation voltage, V 2 , for driving of said display from said reflecting state to said transparent state; a second AC threshold voltage, V 3 , for beginning transition from said transparent state to said reflecting state and a second AC saturation voltage, V 4 , for driving said display to said reflecting state and wherein V 1 <V 2 <V 3 <V 4 ; applying a first AC voltage to at least one address line on said first substrate; said first AC voltage being between said second AC voltage level and said first AC voltage level; and applying a second AC voltage to at least one address line on said second substrate, said second AC voltage being sufficient in amplitude when applied out of phase with said first AC voltage to switch said liquid crystal material into said reflecting state, and when applied in phase with said first AC voltage to switch said liquid crystal material to said transparent state, said second AC voltage being less than the second AC threshold voltage so as to prevent the liquid crystal material from changing from either the transparent state or the reflecting state and said second AC voltage being greater than V 4 -V 3 /2 and wherein V 1 >V 4 -V 3 /2 whereby the effective range of useable address line voltage is expanded.

Claim 19

A method of operating a cholesteric liquid crystal display device having a first substrate having a plurality of substantially parallel address lines disposed thereon, and a second substrate having a plurality of substantially parallel address lines disposed thereon, said first and second substrates operatively disposed in facing, parallel relationship so that said address lines on said first substrate are disposed at an angle with respect to the address lines of said second substrate to form a plurality of crossover points therewith, each crossover point defining a picture element, said method comprising the steps of: providing a layer of a cholesteric liquid crystal material having periodic modulated optical structure that reflects light, disposed between said first and second substrates, said material being switchable between a transparent state in which said material is substantially transparent, and a reflecting state which reflects light, wherein said liquid crystal material reflects light due to the application of a first AC voltage level, and is transparent due the application of a second AC voltage level; said material having a first AC threshold voltage, V 1 , for beginning transition from said reflecting state to said transparent state; a first saturation voltage, V 2 , for driving of said display from said reflecting state to said transparent state; a second AC threshold voltage, V 3 , for beginning transition from said transparent state to said reflecting state and a second AC saturation voltage, V 4 , for driving said display to said reflecting state and wherein V 1 <V 2 <V 3 <V 4 ; applying a first AC voltage to at least one address line on said first substrate; said first AC voltage being between said second AC voltage level and said first AC voltage level; and applying a second AC voltage to at least one address line on said second substrate, said second AC voltage being sufficient in amplitude when applied out of phase with said first AC voltage to switch said liquid crystal material into said reflecting state, and when applied in phase with said first AC voltage to switch said liquid crystal material to said transparent state, said second AC voltage being less than the second AC threshold voltage so as to prevent the liquid crystal material from changing from either the transparent state or the reflecting state and said second AC voltage being greater than V 4 -V 3 /2 and wherein V 1 >V 4 -V 3 /2 whereby the effective range of useable address line voltage is expanded.