JPH01205128A - Liquid crystal electrooptic element - Google Patents

Abstract

PURPOSE:To perform writing and erasing at high speed with a liquid crystal electrooptic element by specifying the parameter which indicates the internal distortion of the liquid crystal. CONSTITUTION:The parameter which indicates the internal distortion of liquid crystal has very strong influences on the strong property and responding properties to writing and erasing of a liquid crystal electrooptic element. Therefore, the parameter DELTAP=Pc/Ps-1 which indicates the internal distortion of the liquid crystal caused by the difference between the cell pitch Pc found from the cell thickness and twist angle specified by the orientation process of the element and the inherent pitch Ps of the liquid crystal specified by the light rotating substance added to the liquid crystal constituting material is set larger than '0'. Therefore, an electrooptic element, with which writing and erasing can be performed at high speeds, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electro-optical element that can be used as a display element, a transmitted light amount control element, and the like.

[Prior art] In manufacturing liquid crystal electro-optical devices, it is advantageous to use a simple matrix, especially when increasing capacity/area, but conventional devices are not suitable for increasing capacity due to optical response characteristics. do not have. For example, even in STN/SBE mode, it is 1/40
There has been a problem in that display quality that can be said to be practically sufficient can only be ensured at a duty of 0 or less.

Therefore, in order to improve the display quality by imparting memory properties even to a simple matrix, we utilize the fact that bistability occurs depending on the applied voltage by controlling the alignment and the liquid crystal composition with unique physical property constants (J, Appl. , Phys.
59,3087. '86, etc.) method was considered. In this specification, this method will hereinafter be abbreviated as the HTN method.

The HTN driving method generally consists of erasing prior to writing display content, selective writing, and retention of the written content.

[Problems to be solved by the invention] However, regarding this HTN method, the above-mentioned literature does not mention at all the appropriate range of conditions for cell preparation, amount of chiral dopant, etc., and only the cell thickness d and the liquid crystal. There is only a description that the ratio d/Ps of the characteristic pitch Ps is 0.75. Moreover, according to the research conducted including other documents, it seems that these appropriate conditions have not been clarified so far.

However, after considering these conditions,
A parameter ΔP that represents the internal distortion of the liquid crystal caused by the difference between the cell pitch Pc determined from the twist angle determined by the cell thickness and alignment treatment and the characteristic pitch Ps of the liquid crystal determined by the optically active substance added to the liquid crystal composition.
It has been found that P c /P s -1 has a very large effect on memory properties, writing and erasing response characteristics, and the like.

Therefore, it is an object of the present invention to provide an electro-optical element that specifies the above-mentioned ΔP and can perform writing and erasing at high speed.

[Means for Solving the Problems] The electro-optical element of the present invention has a cell pitch Pc determined from the cell thickness and the twist angle defined by the alignment process,
Parameter ΔP = P c / P s representing the internal distortion of the liquid crystal caused by the difference in the characteristic pitch Ps of the liquid crystal defined by the optically active substance added to the liquid crystal composition
-1 is set larger than 0.

Example [Example 1] As an electro-optical element, a liquid crystal panel having a size of 5 inches with 200×320 pixels and driven by the HTN method was manufactured as a prototype. As an alignment treatment, silicon oxide was obliquely vapor-deposited on a substrate with striped transparent electrodes, so that the pretilt angle of the liquid crystal was approximately 27 degrees, the rice I angle of the liquid crystal was 270 degrees, and the cell thickness was 6 μm. . A chiral dopant was added to the liquid crystal composition ZLI-1132 manufactured by Merck & Co. between the substrates, and ΔP was changed from +0.20 to -0°2.
Nine types were encapsulated, adjusted to be between 0 and 0. The polarizer is 45 mm from the initial alignment direction of liquid crystal molecules in each substrate.
A prototype liquid crystal panel was prepared by tilting the polarizers so that the polarization axes of each polarizer were perpendicular to each other.

Data voltage Vd = holding voltage Vh = 1.6 volts, selection voltage Vs = 16 volts, frame time was 200 milliseconds, and driving was performed by repeating erasing/writing/holding.

Under these driving conditions, the minimum erase time was measured with a write pulse width of 650 microseconds, and the minimum write pulse width was measured with an erase time that was 10% longer than the minimum erase time.

In the case of measurement under these conditions, there was a tendency that the larger ΔP was, the easier it was to write even if the write pulse width was shorter. There was also a tendency that the larger the ΔP, the easier it was to disappear. The same tendency was also observed when the driving conditions were changed. Table 1 shows the relationship between ΔP, minimum write pulse width Pw, and minimum erase time te.

From Table 1, the minimum time for erasing and writing together is 175 milliseconds when ΔP=-0, 20, and 145 milliseconds when ΔP=+0.05.
It can be seen that there is an improvement in response of 5% or more.

Table 1 [Example 2] A liquid crystal composition manufactured by Merck was placed between the substrates prepared in the same manner as in Example 1! By adding a chiral dopant to 91ZLI-3187, ΔP was +0 as in Example 1.
．． 15 to -0,20 was inserted to create a liquid crystal panel.

When this liquid crystal composition is used, the memory property is lower than that of ZLI-1132, so the holding voltage range becomes narrower.

The measurement was performed with data voltage Vd = holding voltage Vh = 2° 15 volts, selection voltage Vs = 17.2 volts, ■ frame time driving condition of 120 milliseconds, and erase/write/
It was driven by repeated holding.

The minimum erase time is determined by increasing the write pulse width by 3 under these driving conditions.
After measuring as 50 microseconds, the minimum erasure time is 1
The minimum write pulse width was measured with a 0% increase. Table 2 shows the relationship between ΔP, minimum write pulse width Pw, and minimum erase time te in ZL Any 187.

From Table 2, the minimum time for erasing and writing together is 87 milliseconds when ΔP=-0, 20, and 69 milliseconds when ΔP=+0.05. Therefore, by making ΔP smaller than 0, the response is improved as in Example 1, and in this case, 2
It can be seen that it is 0% or more.

In addition, other Merck liquid crystal compositions ZLI-3238, Z
LI-3239, ZLI-1840, ZLI-2861
, ZLI-3449/100. ZLI-3201100
0, ZLI-3201/100, ZLI-1694, Z
LI-1691, ZLI-18001000, ZLI-
1565, ZLI-30211000, ZLI-302
The results of studies using 1/100, ZLI-2411, etc. also show that when the selection voltage vS, holding voltage vh, etc. are set to appropriate conditions for each liquid crystal composition, and the optical response time is measured, the ZLI -3,187, ΔP is 0
It was found that when the value is increased, the erasing and writing times are improved, and in both cases, erasing and writing can be performed at a speed of 10% or more compared to when ΔP=-0 and 20.

Table 2 [Example 3 Based on the results of at least 3 examples, 112
We prototyped a 12-inch liquid crystal panel with 0x750 pixels.

The alignment treatment was performed in the same manner as in Example 1, and the pretilt angle of the liquid crystal was about 27 degrees, the twist angle of the liquid crystal was 270 degrees, and the cell thickness was 6 μm.

A liquid crystal composition ZLany 318 manufactured by Merck & Co., Ltd. was placed between the substrates.
7 was filled with a chiral dopant to give a ΔP of 10.05, and a prototype liquid crystal panel was prepared. Also, for comparison, ΔP was −0,
20 was also sealed to create a liquid crystal panel.

Erase time te = 20 ms, write pulse width 260
In microseconds, the total erasing and writing time for one frame is 215 milliseconds. Therefore, the frame time is set to 270 milliseconds, and data voltage Vd = holding voltage Vh
= 2.15 volts, selection voltage Vs = 17.2 volts, and when driving was performed in the same manner as in Example 2, in which continuous erasing/writing/holding was repeated, ΔP was +0.05. Although the prototype liquid crystal panel exhibited optical response, those with ΔP of -0 and 20 were insufficient in both erasing and writing. To make this Δp=-Q, 20 optically responsive,
Erase time is 25 ms or more, write pulse width is 310
It needed to be more than microseconds.

From the above three examples, it can be seen that the response speed can be improved by at least making ΔP larger than ±0.

Although the embodiments have been described above, the present invention is not limited to the above-mentioned embodiments, but can also be realized by changing the liquid crystal composition, alignment treatment method, cell conditions, cell manufacturing method, etc.

[Effects of the Invention] As described above, according to the present invention, the cell pitch 'Pc determined from the cell thickness of the liquid crystal electro-optical element and the twist angle defined by the alignment treatment, and the optically active substance added to the liquid crystal composition. Parameter ΔP(
=Pc/Ps-1), it is possible to provide an electro-optical element that can perform writing and erasing at high speed.

Claims (1)

[Claims] In a liquid crystal electro-optical element that erases, writes, and retains written content by applying a bias voltage, the cell pitch Pc determined from the cell thickness and the twist angle defined by the alignment process, and the optically active substance added to the liquid crystal composition. The parameter ΔP= represents the internal distortion of the liquid crystal caused by the difference in the characteristic pitch Ps of the liquid crystal defined by
A liquid crystal electro-optical element characterized in that Pc/Ps-1 is set larger than 0.