Liquid Crystal Display Device
A liquid crystal display device is provided with a liquid crystal display panel ( 1 ) composed of a liquid crystal display part having no color filter, and a backlight unit having a light source which can emit light of a plurality of colors. The liquid crystal display device is also provided with a first driving circuit ( 2 ), which permits the light source to successively emit light of a plurality of colors in a prescribed cycle, and applies a driving voltage to the liquid crystal of each pixel of the liquid crystal display part, in synchronization with the emission timing so as to perform color display; a second driving circuit ( 3 ), which stops emission from the light source or permits the light source to emit only light of one wavelength, applies a driving voltage to the liquid crystal of each pixel of the liquid crystal display part in a longer cycle than the prescribed cycle for black-and-white display or monocolor display; and a drive selecting means ( 4 ), which selects to operate either the first driving circuit ( 2 ) or the second driving circuit ( 3 ). The absolute value of the driving voltage of the second driving circuit ( 3 ) is permitted to be smaller than the driving voltage of the first driving circuit ( 2 ).
1 . A liquid crystal display device for forming a predetermined image on one screen by sequentially selecting a plurality of scanning lines and applying a voltage to a liquid crystal,
wherein the frequency for selecting the scanning line comprises at least two frequencies, said frequencies being a high frequency and a frequency lower than the high frequency, and
wherein a voltage applied to the liquid crystal at the low frequency is made lower than a voltage applied to the liquid crystal at the high frequency.
2 . The liquid crystal display device according to claim 1 ,
wherein both of a first drive and a second drive are selectable, the first drive performing color display by applying driving voltages to the liquid crystal in synchronization with light emission timings of light source for sequentially emitting a plurality of light with different wavelengths in a predetermined cycle, and the second drive performing display by stopping the light emission by the light source or permitting the light source to emit only light of one wavelength to apply a driving voltage to the liquid crystal in a predetermined cycle, and wherein the first drive is at the high frequency and the second drive is at the low frequency.
3 . A liquid crystal display device, comprising:
a liquid crystal display panel comprising a liquid crystal display part provided with no color filter and a backlight unit having light source capable of emitting light of a plurality of colors with different wavelengths;
a first driving circuit for performing color display by permitting the light source of the liquid crystal display panel to sequentially emit the light of the plurality of colors with different wavelengths in a predetermined cycle, and applying a driving voltage to a liquid crystal of each pixel of the liquid crystal display part in synchronization with the light emission timings;
a second driving circuit for performing black-and-white display or monocolor display by stopping the light emission by the light source or permitting the light source to emit only light of one wavelength to apply a driving voltage to the liquid crystal in each pixel of the liquid crystal display part in a cycle longer than the predetermined cycle; and
a drive selecting means for selecting and operating any one of the first driving circuit and the second driving circuit,
wherein the driving voltage by the second driving circuit is made smaller in absolute value than the driving voltage by the first driving circuit.
4 . The liquid crystal display device according to claim 3 ,
wherein the first driving circuit is a circuit for performing field sequential color drive.
5 . The liquid crystal display device according to claim 4 ,
wherein the time of application of the driving voltage to each pixel of the liquid crystal display part by the second driving circuit is made longer than the time of application of the driving voltage to each pixel of the liquid crystal display part by the first driving circuit.
6 . The liquid crystal display device according to claim 4 ,
wherein during the field sequential color drive by the first driving circuit, one field of display by the liquid crystal display panel is divided at least into subfields corresponding to the number of colors of light emitted by the light source, and driving voltages according to display data for different colors are sequentially applied to each pixel of the liquid crystal display part for each of the subfields, and
wherein during the drive by the second driving circuit, a driving voltage according to display data is applied to each pixel of the liquid crystal display part only during a period corresponding to one subfield of the subfields to increase the cycle of application of the driving voltage or the application cycle and application time.
7 . The liquid crystal display device according to claim 4 ,
wherein during the field sequential color drive by the first driving circuit, one field of display by the liquid crystal display panel is divided at least into subfields corresponding to the number of colors of light emitted by the light source, and each of the subfields is further divided into a write period to write display data into the liquid crystal display part, a response waiting period to wait for response by the liquid crystal display part, and a lighting period to permit the light source to emit light of a color corresponding to each subfield, and driving voltages according to display data for different colors are sequentially applied to each pixel of the liquid crystal display part only during each said write period for each said subfield, and
wherein during the drive by the second driving circuit, a driving voltage according to display data is applied to each pixel of the liquid crystal display part only during a period corresponding to the write period of one subfield of the subfields to increase the cycle of application of the driving voltage.
8 . The liquid crystal display device according to claim 5 ,
wherein during the field sequential color drive by the first driving circuit, one field of display by the liquid crystal display panel is divided into subfields corresponding to the number of colors of light emitted by the light source, and driving voltages according to display data for different colors are sequentially applied to each pixel of the liquid crystal display part for each of the subfields, and
wherein during the drive by the second driving circuit, a driving voltage according to display data is applied to each pixel of the liquid crystal display part over a plurality of the divided subfield periods to increase the cycle and time of application of the driving voltage.
9 . The liquid crystal display device according to claim 4 ,
wherein the display data generating the driving voltage during the drive by the second driving circuit is data corresponding to the most significant bit of the color corresponding to the selected subfield or a specific color.
10 . The liquid crystal display device according to claim 9 ,
wherein the color corresponding to the selected subfield or the specific color is green.
11 . The liquid crystal display device according to claim,
wherein the first driving circuit is provided with a multi-gradation signal generating circuit for three gradations or more, and during the field sequential color drive, the driving voltage generated by the multi-gradation signal generating circuit according to display data is applied to each pixel of the liquid crystal display part, and
wherein the second driving circuit is provided with a two-gradation signal generating circuit, and during the drive by the second driving circuit, the multi-gradation signal generating circuit is stopped, and the driving voltage generated by the two-gradation signal generating circuit is applied to each pixel of the liquid crystal display part.
12 . The liquid crystal display device according to claim 11 ,
wherein the driving voltage generated by the two-gradation signal generating circuit is smaller in absolute value of voltage than the driving voltage generated by the multi-gradation signal generating circuit.
13 . The liquid crystal display device according to claim 12 ,
wherein a color driving voltage generating part and a black-and-white driving voltage generating part are provided so that an output voltage of the color driving voltage generating part is supplied to the multi-gradation signal generating circuit, and an output voltage of the black-and-white driving voltage generating part is supplied to the two-gradation signal generating circuit, and wherein the output voltage of the black-and-white driving voltage generating part is set smaller in absolute value than the output voltage of the color driving voltage generating part.
14 . The liquid crystal display device according to claim 3 ,
wherein the driving voltage by the second driving circuit is made smaller by 15% to 70% in absolute value than the driving voltage by the first driving circuit.
15 . The liquid crystal display device according to claim 5 ,
wherein during the field sequential color drive by the first driving circuit, one field of display by the liquid crystal display panel is divided at least into subfields corresponding to the number of colors of light emitted by the light source, and driving voltages according to display data for different colors are sequentially applied to each pixel of the liquid crystal display part for each of the subfields, and
wherein during the drive by the second driving circuit, a driving voltage according to display data is applied to each pixel of the liquid crystal display part only during a period corresponding to one subfield of the subfields to increase the cycle of application of the driving voltage or the application cycle and application time.
16 . The liquid crystal display device according to claim 5 ,
wherein during the field sequential color drive by the first driving circuit, one field of display by the liquid crystal display panel is divided at least into subfields corresponding to the number of colors of light emitted by the light source, and each of the subfields is further divided into a write period to write display data into the liquid crystal display part, a response waiting period to wait for response by the liquid crystal display part, and a lighting period to permit the light source to emit light of a color corresponding to each subfield, and driving voltages according to display data for different colors are sequentially applied to each pixel of the liquid crystal display part only during each said write period for each said subfield, and
wherein during the drive by the second driving circuit, a driving voltage according to display data is applied to each pixel of the liquid crystal display part only during a period corresponding to the write period of one subfield of the subfields to increase the cycle of application of the driving voltage.
17 . The liquid crystal display device according to claim 5 ,
wherein the display data generating the driving voltage during the drive by the second driving circuit is data corresponding to the most significant bit of the color corresponding to the selected subfield or a specific color.
18 . The liquid crystal display device according to claim 5 ,
wherein the first driving circuit is provided with a multi-gradation signal generating circuit for three gradations or more, and during the field sequential color drive, the driving voltage generated by the multi-gradation signal generating circuit according to display data is applied to each pixel of the liquid crystal display part, and
wherein the second driving circuit is provided with a two-gradation signal generating circuit, and during the drive by the second driving circuit, the multi-gradation signal generating circuit is stopped, and the driving voltage generated by the two-gradation signal generating circuit is applied to each pixel of the liquid crystal display part.
19 . The liquid crystal display device according to claim 18 ,
wherein a color driving voltage generating part and a black-and-white driving voltage generating part are provided so that an output voltage of the color driving voltage generating part is supplied to the multi-gradation signal generating circuit, and an output voltage of the black-and-white driving voltage generating part is supplied to the two-gradation signal generating circuit, and wherein the output voltage of the black-and-white driving voltage generating part is set smaller in absolute value than the output voltage of the color driving voltage generating part.
20 . The liquid crystal display device according to claim 4 ,
wherein the driving voltage by the second driving circuit is made smaller by 15% to 70% in absolute value than the driving voltage by the first driving circuit.