JPH02208626A - Method for driving liquid crystal device - Google Patents

Abstract

PURPOSE:To obtain the easiest-to-see display state at all times by varying the effective value of a voltage which is impressed to the liquid crystal layer of a 1st liquid crystal cell when switching a state wherein a voltage is impressed to a 2nd liquid crystal cell and a state wherein the voltage is not impressed. CONSTITUTION:Multiplex driving wherein >=3 values can be selected as the voltage impressed to the liquid crystal layer is applied to the 1st liquid crystal cell 1 and static driving is applied to the 2nd liquid crystal cell 2. Then the effective value of the voltage impressed to the 1st liquid crystal cell 1 is varied when the state wherein the voltage is impressed to the 2nd liquid crystal cell and the state wherein the voltage is not impressed. Consequently, the easiest- to-see display state is obtained at all times without reference to whether or not the 2nd liquid crystal cell 2 is driven.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for driving a liquid crystal device.

[Conventional technology] The conventional super twisted nematic liquid crystal device has 1
For example, as in JP-A-60-50511, when the twist angle of the liquid crystal molecules is 180 degrees or more, the product Δn-d of the optical anisotropy of the liquid crystal and the liquid crystal layer thickness d is from 0.7 μm to 1.1 μm. Met.

Therefore, coloration occurs due to birefringence, and when a non-selective voltage is applied, the color becomes yellow, and when a selective voltage is applied, it becomes blue, resulting in poor appearance. Also, if you use coloring by 5 birefringence to display multi-colors, you can see Jrii! When an intermediate voltage between the selection voltage and the selection voltage is applied, the display ranges from yellow to slightly bluish-green to blue, and other colors cannot be obtained, making it impossible to obtain a sufficient multicolor display.

Previously, the present applicant set the twist angle of the liquid crystal in the range of 180 degrees to 360 degrees as a solution to such problems,
The product Δn-d of the optical anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d is 1
．． We have proposed a liquid crystal device that is capable of multicolor display by driving a single gradation display using a liquid crystal cell with a thickness of 1 μm or more. In addition, by adding a second liquid crystal cell that has electrodes on its inner surface as an optical compensation cell to this liquid crystal cell, it is possible to display black and white gradation when the second liquid crystal cell is not driven, and to display multicolor when it is driven. It became.

[Problems to be Solved by the Invention] However, in such a liquid crystal device, when the second liquid crystal cell is in a non-driven state and displays black and white gradation, the display becomes most visible when the first liquid crystal cell Driving conditions and second
The display is most visible when the first liquid crystal cell is in the driven state and is performing multi-color display.Because the driving conditions of the first liquid crystal cell are different, when the second liquid crystal cell is switched between the driven state and the non-driven state, 1 display becomes difficult to see.

The present invention was proposed in view of such problems, and is the second invention.
An object of the present invention is to provide a method for driving a liquid crystal device that can always provide the most easily viewable display state regardless of whether the liquid crystal cell is in a driven or non-driven state.

[Means for Solving the Problems] A method for driving a liquid crystal device of the present invention includes sandwiching twisted oriented nematic liquid crystal between a substrate having a scanning electrode and a substrate having a signal electrode, and the twist angle of the nematic liquid crystal is 180.
In the range of 360 degrees.

Further, the product Δn−d of the optical anisotropy Δn of the nematic liquid crystal and the liquid crystal layer thickness d (μm) of the nematic liquid crystal is 1.
a first liquid crystal cell having a thickness of 1 μm or more, a second liquid crystal cell having a nematic liquid crystal sandwiched between a pair of substrates having an IF layer disposed opposite to each other, the first liquid crystal cell, and the second liquid crystal cell. For a liquid crystal device having a pair of polarizing plates arranged on both sides of the liquid crystal layer, the first liquid crystal cell is driven by a multiplex drive that allows selection of three or more voltage values to be applied to the liquid crystal layer, and the second liquid crystal cell is In a method for statically driving a liquid crystal device, when switching between a state where a voltage is applied to the second liquid crystal cell and a state where no voltage is applied, the voltage is applied to the liquid crystal layer of the first liquid crystal cell. It is characterized by changing the effective value of voltage.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Example 1 FIG. 1 is a cross-sectional view of a liquid crystal device used in this example.
l is the first liquid crystal cell, the liquid crystal layer thickness is 8.61 m, the birefringence Δn of the liquid crystal used is 0.185, the twist angle of the liquid crystal molecules between the upper and lower substrates is 220 degrees, and the number of scanning electrodes is 200. 1/200 duty with 640 9 electrodes
It was driven. 2 is a second liquid crystal cell, and the liquid crystal layer thickness is 8.
6 μm, and the birefringence Δn of the liquid crystal used is 0.185, which is the same as that of the first liquid crystal cell, but the liquid crystal molecules between the upper and lower substrates are twisted 220 degrees in the opposite direction to that of the first liquid crystal cell.

FIG. 2 is a diagram showing the relationship between the rubbing direction (the direction of the molecular axis of the liquid crystal molecules close to the electrode substrate) and the absorption axis of the polarizing plate in the liquid crystal device of FIG.

In the figure, R11 and R12 are the rubbing directions 1., . . . of the lower electrode substrate 11 and the upper electrode substrate 12 of the first liquid crystal cell l, respectively. θ is the rubbing direction R12 of the upper electrode substrate 12 of the first liquid crystal cell and the lower electrode substrate 21 of the second liquid crystal cell.
TI is the angle formed with the rubbing direction R21 of Twisting direction and angle of liquid crystal molecules in a liquid crystal cell, PL-
P2 is the direction of the absorption axis of the upper polarizing plate 31 and the lower polarizing plate 32, respectively, and θl is the direction PI of the absorption axis of the lower polarizing plate 32.
and the rubbing direction R11 of the lower electrode substrate 11 of the first liquid crystal cell l.

θ2 represents the angle between the direction P2 of the polarization axis of the upper polarizing plate 31 and the rubbing direction R22 of the upper electrode base @22 of the second liquid crystal cell 2, T1=72=220 degrees, θ1=02=4
5 degrees, and θ=90 degrees.

FIG. 3 is a diagram showing the driving waveform of the first liquid crystal cell, (
(a) is a voltage waveform applied to the signal electrode, (b) is a voltage waveform applied to the scan electrode, and (c) is a composite waveform of the voltage waveform applied to the signal electrode and the scan electrode. Kokote, VO
-V l =V 1-V2=V3-V4=V4-V5=
(V2-V3)/9. When the first liquid crystal cell was used to display 8 gray levels at a temperature of about 20° C. without driving the second liquid crystal cell, VO-V5=25. The gradation display is the easiest to see with IV. In addition, when the second liquid crystal cell was statically driven at an effective value of 12 V and a frequency of 1 kHz in this state, the display became a multicolor display, but the first display was << VO-V5. = 24, OV, the multi-color display was the easiest to see (so a circuit like the one shown in Figure 4 was set up to synchronize the second liquid crystal cell with switching between the drive state and the non-drive state). ,VO-V
5 was set to switch between 24, OV and 25.1V, it became possible to always obtain the most legible display regardless of the state of the second liquid crystal cell.

Example 2 In Example 1, the VO-V5 condition was set at a temperature of 20°C, but this condition varies depending on the temperature, for example, at 0°C.
When the second liquid crystal cell is in the driving state, VO-V5=24
．． 7V, and in the non-driving state, the display became most visible at VO-V5=26.0V. Further, when the temperature is 40°C, when the second liquid crystal cell is in the driving state, VO-V5=22. When the TV was not being driven, the display was most visible at 23.2V. In other words, the difference in voltage between the driven state and the non-driven state of the second liquid crystal cell at which the display becomes most visible is 1.3 V at 0°C, and 20 V at 0°C.
The voltage decreases as the temperature increases, from 1.1 V at 40° C. to 0.5 V at 40° C. Therefore, by installing a temperature sensor in the liquid crystal device to compensate for this voltage difference depending on the temperature, it became possible to switch between gradation display and multicolor display, which is always the most legible state regardless of the temperature. .

Example 3 In Example 1 and Example 2 above, VO-V1 is linked to switching between the driving state and non-driving state of the second liquid crystal cell.
=V1-V2=V3-V4=V4-V5= (V2-V
3) VO-V5 was changed without changing the condition of /9, but with VO-V5 fixed, Vo-V l =V
1-V2=V3-V4=V4-V5 and V2-V3 (7)
Exactly the same effect was obtained by changing the ratio.

Example 4 In Examples 1 to 3 described above, frameless gradation was performed, but similar effects were obtained when pulse gradation was performed.

Furthermore, it has been found that similar effects can be obtained not only with 4-gradation display but also with 3-64 gradation display.

[Effects of the Invention] As described above, the present invention includes a twisted oriented nematic liquid crystal sandwiched between a substrate having a scanning electrode and a substrate having a signal electrode, and the twist angle of the nematic liquid crystal is in the range of 180 degrees to 360 degrees. and the optical anisotropy Δn of the nematic liquid crystal and the liquid crystal layer thickness d (μm
), the product Δn-d is 1.11 m or more, a second liquid crystal cell in which a nematic liquid crystal is sandwiched between a pair of substrates having 1f poles arranged opposite to each other, and the first liquid crystal cell.
For a liquid crystal device having a liquid crystal cell and a pair of polarizing plates disposed on both sides with the second liquid crystal cell in between,
In the method of driving a liquid crystal device, the liquid crystal cell is driven by multiplex driving in which three or more voltages can be selected from the voltage applied to the liquid crystal layer, and the second liquid crystal cell is statically driven, wherein a voltage is applied to the second liquid crystal cell. When switching between a state in which a voltage is applied and a state in which no voltage is applied, the second liquid crystal cell is switched between a driven state and a non-driven state by changing the effective value of the voltage applied to the liquid crystal layer of the first liquid crystal cell. This has the effect that the most easily viewable display state can always be obtained regardless of the situation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a liquid crystal device used in an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the rubbing direction and the polarization axis in the liquid crystal device of FIG. 1. FIG. 3 is a diagram showing driving waveforms of the first liquid crystal cell. FIG. 4 is a diagram showing a circuit that switches the value of VO-V5 in conjunction with switching between the drive state and non-drive state of the second liquid crystal cell. First liquid crystal cell Second liquid crystal cell Lower substrate Upper substrate Spacer Liquid crystal layer Transparent electrode of upper substrate Alignment film of upper substrate Alignment film of lower substrate Transparent electrode of lower substrate Lower substrate 22 ・ 23 ・ 24 ・ 25・ 26 ・ 27 ・ 2B ・ 3 l ・ 32 ・ Upper substrate Spacer Liquid crystal layer plate Transparent electrode of upper substrate Alignment film of upper substrate Alignment film of very lower substrate I! Transparent electrode on the very bottom substrate Upper polarizing plate Lower polarizing plate

Claims (1)

[Claims] A twisted oriented nematic liquid crystal is sandwiched between a substrate having a scanning electrode and a substrate having a signal electrode, the twist angle of the nematic liquid crystal is in the range of 180 degrees to 360 degrees, and
The product Δn·d of the optical anisotropy Δn of the nematic liquid crystal and the liquid crystal layer thickness d (μm) of the nematic liquid crystal is 1.1 μm.
The above-described first liquid crystal cell, a second liquid crystal cell in which a nematic liquid crystal is sandwiched between a pair of substrates having electrodes arranged facing each other, the first liquid crystal cell, and the second liquid crystal cell. For a liquid crystal device having a pair of polarizing plates placed on both sides, the first liquid crystal cell is driven by a multiplex drive that allows selection of three or more voltage values to be applied to the liquid crystal layer, and the second liquid crystal cell is driven by a static drive. In the method for driving a liquid crystal device, an effective value of the voltage applied to the first liquid crystal cell when switching between a state where a voltage is applied to the second liquid crystal cell and a state where no voltage is applied. A method for driving a liquid crystal device characterized by changing the .