JPS6363888B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an accumulation type liquid crystal display cell with a short image fixing time.

Liquid crystal display cells that utilize the electro-optic effect of liquid crystals have features such as low power consumption, light-receiving type, and thinness, and are widely used for numeric displays, character displays, graphic displays, etc. Most of the electro-optical effects of liquid crystals that have been applied so far are DS mode and FE mode, but the CNT mode described below has a memory function and is particularly effective when used in character displays and graphic displays. A liquid crystal cell using a cholesteric liquid crystal with positive dielectric constant anisotropy as a liquid crystal material is provided with a layer of an alignment agent that has the effect of aligning the nematic liquid crystal perpendicularly to the substrate on the inner surface of the electrode substrate of the liquid crystal cell. Showing the electro-optic effect of CNT mode.
That is, in the initial state where no voltage is applied, the liquid crystal forms a cholesteric phase spiral structure, and in this state the cell appears almost transparent. Next, when a voltage is gradually applied, the liquid crystal, after passing through a light scattering state, forms a nematic phase homeotropic structure at a voltage V equal to or higher than a certain threshold value _VH , and the cell becomes completely transparent. When the applied voltage is reduced from this state by V/2 (V/2<V _H ), the cell gradually shifts to a light scattering state while maintaining a transparent state for a sufficiently long time. However, once the applied voltage is set to zero and then set to a voltage of V/2, in this case the cell quickly transitions to a light scattering state, and thereafter the light scattering state continues to accumulate even if the applied voltage is removed. . In other words, let the voltage change be V→V/2 or V→0→V/2
Depending on the conditions, two states, transparent and light-scattering (cloudy), can be created, and even if the applied voltage is then zero, the state once formed will be stored for a considerable period of time. This is the electro-optical effect of the CNT mode, and it can be used to function as a memory (image storage).
A liquid crystal display cell having the following can be realized. However, in the electro-optic effect of the CNT mode mentioned above,
In the step of reducing the applied voltage to zero in order to accumulate an image, the transparent state exhibits light scattering for a short time τ _rp and then shifts to the original transparent state and is accumulated. In other words, during the time τ _rp , the applied voltage is (V→V/2)
In both the cases where →0 and (V→0→V/2)→0, light scattering occurs, and the displayed image temporarily disappears during this time. For this reason, τ _rp is called the image fixation time, and the existence of τ _rp
This is considered to be a drawback of the electro-optic effect of CNT mode.
For this reason, research is being actively conducted to find liquid crystal materials with a short τ _rp , but at present no satisfactory material has yet been found. However, the inventor has determined that τ _rp in the electro-optic effect of CNT mode
However, the inventors discovered that the method greatly depends not only on the liquid crystal material but also on the substance forming the alignment agent layer provided on the inner surface of the electrode substrate, leading to the present invention.

An object of the present invention is to provide a liquid crystal cell having an image storage function using the electro-optic effect of the CNT mode, in which the image fixing time τ _rp is extremely short.

According to the present invention, in a liquid crystal cell in which a cholesteric liquid crystal exhibiting positive dielectric constant anisotropy is filled in the gap between two opposing electrode substrates, the inner surface of the electrode substrates has a carbon number of 12 to 16. A liquid crystal cell with a short τ _rp can be obtained by providing an alignment agent layer of an amine having a straight hydrocarbon chain.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a liquid crystal cell of the present invention. 1 is a set of transparent electrode substrates in which indium oxide is vapor-deposited on a glass plate; 2 is a layer of an alignment treatment agent; the transparent electrode substrates 1 are held at a constant interval by Teflon film spacers 3, and are bonded with epoxy It is bonded by adhesive 4. 5 is a liquid crystal substance.

The effects of the present invention will be explained below with reference to specific examples.

Example 1 In a liquid crystal cell having the structure shown in FIG. 1, MBBA (p-
methoxybenzylidene−p′−butylaniline),
BBCA (p-butoxybenzylidene-p'-
A mixed cholesteric liquid crystal with positive dielectric constant anisotropy containing cyanoaniline) and CC (cholesteryl chloride) in a weight ratio of 68:20:12 was used, and n-dodecylamine (n-dodecylamine) was used as a second alignment agent layer. A layer of C ₁₂ H ₂₅ NH ₂ ) was formed. The method for forming the n-dodecylamine layer is as follows. First, 0.03 mol/n-dodecylamine is dissolved in ethanol, the electrode substrate is immersed in this solution, and ultrasonic waves are applied for 10 minutes. Thereafter, the electrode substrate is gently pulled up and dried to form a layer of n-dodecylamine on the electrode substrate. The electrode-substrate spacing of the cell of this example is 12.0 μm. When this cell τ _rp was measured, it was τ _rp =6.9 seconds.

Example 2 A cell with the same configuration as Example 1 was created, except that the alignment agent layer was a n-tetradecylamine (C ₁₄ H ₂₉ NH ₂ ) layer and the electrode substrate spacing was 6.6 μm. When τ _rp was measured, it was τ _rp =0.69 seconds.

Example 3 Except that the alignment agent layer was a n-tetradecylamine layer and the electrode substrate spacing was 12.3 μm,
When a cell with the same configuration as in Example 1 was prepared and τ _rp was measured, τ _rp =8.2 seconds.

In order to clearly understand the effects of the present invention, examples in which an alignment agent layer having a carbon number other than 12 to 16 is used will be shown as a reference.

Example 4 The alignment agent layer was made of normal octylamine (n-
octylamine, C ₈ H ₁₇ NH ₂ ), and the cell has the same configuration as in Example 1, except that the electrode-substrate spacing is 13.5 μm. When τ _rp was measured, τ _rp =
It took 45.3 seconds.

Example 5 The alignment treatment agent layer was made of n-hexylamine (n-
Hexylamine, C ₆ H ₁₃ NH ₂ ) layer, and a cell with the same configuration as in Example 1 except that the electrode-substrate spacing was 12.1 μm, and τ _rp was measured. τ _rp =
It took 38.8 seconds.

The results of the above-mentioned examples and many other examples conducted by the present inventor are shown in FIG. Figure 2 shows τ _rp and electrode substrate spacing d in a liquid crystal cell with a layer of n-alkylamine having a linear hydrocarbon chain with 6 to 18 carbon atoms.
This is a graph showing the relationship between In order to clearly demonstrate the effect of the present invention, the value of τ _rp in the case of d = 10 μm is read in FIG. When plotted against this, it becomes as shown in Figure 3. As is clear from Figure 3, the number of carbon atoms n is
It can be seen that in the case of 12 to 16, τ _rp becomes extremely short, and the effect of the present invention is large. Furthermore, as an alignment agent layer, measurements were made using n-alkyl trimethyl ammonium chloride instead of normal alkyl amine and changing the number of carbon atoms in the hydrocarbon straight chain. In the range of 16, τ _rp showed a small value. As a result, it was revealed that high-quality storage-type image display with short image fixing time is possible by using the liquid crystal cell of the present invention.

As described above, according to the present invention, an accumulation type liquid crystal display cell with a short image fixing time can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of a liquid crystal cell according to the present invention, in which 1 is an electrode substrate, 2 is an alignment agent layer, 3 is a spacer, 4 is an adhesive, and 5 is a liquid crystal material. Figures 2 and 3 are diagrams showing the effects of the present invention. Figure 2 is a diagram showing the relationship between image fixing time and electrode substrate spacing, and Figure 3 is a diagram showing the relationship between image fixing time and hydrocarbon directivity of the alignment agent. FIG. 3 is a diagram showing the relationship with the number of carbon atoms in the chain.

Claims (1)

[Claims] 1. In a liquid crystal cell formed by filling the gap between two opposing electrode substrates with cholesteric liquid crystal exhibiting positive dielectric constant anisotropy, a hydrocarbon linear chain having 12 to 16 carbon atoms is formed on the inner surface of the electrode substrates. 1. A liquid crystal cell, comprising: an alignment treatment agent layer containing an amine.