JPH07104513B2 - Liquid crystal cell - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal cell using a ferroelectric liquid crystal having a high-speed response and a memory property and having a long life.

(B) Prior art The use of a ferroelectric liquid crystal for a high-speed shutter or a large matrix in a liquid crystal is described in, for example, Japanese Patent Application Laid-Open No. 60-57821. When sandwiched between smaller gaps and the sandwiched body is subjected to orientation treatment, as shown in Fig. 5, due to the azimuth of the molecular axis and the peculiarity of polarization (P _s ), the molecular axis depends on the presence or absence of an electric field. The orientation of can be controlled to two positions. The previous publication describes that rubbing is applied to PUA, Teflon, polyimide, silane, etc., but it is difficult to obtain uniform alignment (monodomain) over the entire effective display surface, and alignment is performed when no electric field is applied. It was inconvenient because patterns were often observed due to defects.

Therefore, it was considered to sandwich the ferroelectric liquid crystal between the film that acts on the spontaneous polarization and the film that acts on the orientation of the molecular axis. Figure 4 is a characteristic diagram of the experiments based on this idea, 15V _oF, 10
The response of orientation to a pulsed applied voltage (a) of 0 μsec is detected as the amount of light transmission between orthogonal Nicols. (B) is the response of the monodomain by the shear alignment method, and after sandwiching the chiral smectic liquid crystal between clean substrates that have not been newly aligned on the surface, the liquid crystal molecules are slightly displaced by separating both substrates. This alignment method based on the arrangement has a very small effect of restricting the alignment by the substrate surface, and the molecular position is easily changed by the electric field. On the other hand, (c) is a film in which a chiral smectic liquid crystal is sandwiched between a film having an active group that acts on spontaneous polarization and a rubbed uniaxial alignment film for twisted nematic liquid crystal, and the initial alignment surely forms a monodomain. However, it was found that the influence was too strong, the response by the electric field was slow, and the memory property was not exhibited.

In other words, in this idea, one substrate was used to control the polarization direction and the other substrate was used to control the molecular direction, so that the uniformity of orientation was obtained reliably and easily, but the influence of the electric field worked effectively on the one substrate surface. No, in other words, it was considered that the alignment regulating force on the substrate surface was too strong.

(C) Problems to be Solved by the Invention The present invention has been made by the above research, and provides a liquid crystal cell in which the ferroelectric liquid crystal can be uniformly and stably aligned and has a good response and a memory property. is there.

D) Means for Solving the Problems The present invention provides a surface of one substrate which is in contact with the ferroelectric liquid crystal with 5000
One or more fluoroalkyl chains per atom (C _n F _{2n + 1} ).
Is further provided with a polymer film containing, and more preferably the polymer film is subjected to alignment treatment, the other substrate is provided with a homogeneous alignment film without alignment treatment, more preferably fluoroalkyl of the polymer film. The n in the chain is between 1 and 3.

(E) Action As a result, the liquid crystal is uniformly and stably aligned, and the response is fast and the memory property is provided.

Example) FIG. 1 is a sectional view of a liquid crystal cell according to an example of the present invention.
(2) is a substrate for a liquid crystal cell in which a ferroelectric liquid crystal (3) such as a chiral nematic C phase is sandwiched, and electrodes (4) (4) ... It has a polymer film (6), and the films (5) and (6) are provided so as to be in contact with the liquid crystal (3). The films (5) and (6) will be described more specifically below.

First, a polyimide horizontal alignment agent (PIX-5400 manufactured by Hitachi Chemical Co., Ltd.) is applied on a glass base having a transparent electrode and dried to form a thin film (organic polymer film (6)) of about 1000 Å on a substrate. (1) was obtained.

On the other hand, one hydrogen atom of ε-caprolactam was replaced with CF ₃ on another glass substrate.

And ε-caprolactam were subjected to ring-opening copolymerization at a molar ratio of 1: 1 to form a thin film having an average molecular weight of about 10,000 atoms, and the surface was unidirectionally rubbed. The polymer film (5) thus obtained has a thickness of about 1000Å. Substrates (1) and (2) obtained by these are stuck together to form a layer thickness of 3 μm.
, A strong dielectric liquid crystal (CS-1011, manufactured by Chisso Corp.) was filled and the temperature was changed to obtain a chiral smectic C phase (S _m C ^* ). A uniform monodomain could be observed within the effective display surface of 180 × 220 mm. Figure 2 shows such a liquid crystal cell with 15V _OP , 10
The response when a pulse (a) of 0 μsec is given is shown, and a steep response as shown by the curve (A) is exhibited and a good memory property is exhibited.

As the organic polymer film (6), the polyimideamide resin polyvinyl alcohol and the polyamide resin were also tested, but a uniform monodomain was observed in some cases, and the response characteristics were generally quick response as shown in FIGS. 2B, 2C and 2D. , Showed stable memory property. As described above, the organic polymer film (6) showed almost the same result as long as it was a horizontal alignment film which was not subjected to alignment treatment such as rubbing. Therefore, the following description will be made by using a polyimide horizontal alignment agent.

For the above polymer film (5), ε-caprolactam and CF
Ring-opening copolymerization with _3- substituted ε-caprolactam in various molar ratios to form various liquid crystal cells, 15V _OP , 100μsec
The positive and negative alternating pulses were continuously energized. Figure 3 shows 15
V _OP, 100 .mu.sec, after the application of the positive and negative alternating pulse of 30Hz at 1000 hours at room temperature, while indicating the total area of the defective domain generated in the effective display area 180 × 220 mm, CF ₃ per unit number atoms It is shown that the abundance is related to the stability of the monodomain.

Further in the above example, as a substitution for ε-caprolactam,
Experiments using C ₂ F ₅ or C ₃ F ₇ instead of CF ₃ gave similar results. However, regarding C _n F _{2n + 1} (n> 4),
Since the phenomenon of vertical alignment was observed depending on the conditions, it was found that it is necessary to study the compatibility between such long-chain fluoroalkyl chains and the liquid crystal material in order to ensure stable alignment.

G) Effect of the invention In the above examples, since the fluoroalkyl chain acts on the spontaneous polarization of the ferroelectric liquid crystal, if alignment treatment such as rubbing is performed on it, synergistic effects due to the van der Waals force and the volume exclusion effect are obtained. In opposition to the effect, the alignment control force is considerably weaker than when the alignment treatment is performed on the horizontal alignment film, so that the ease of alignment and the uniformity can be obtained, but the movement of the molecules is not prevented. In addition, the positive and negative repeating pulses tend to grow undesired domains due to non-uniformity of the surface and minute changes in the electric field distribution, but there is a predetermined amount or more of fluoroalkyl chains in the polymer such as polyimide, polyamide, or polyimideamide. For example, it stops the growth of this unwanted domain and prolongs its life.

Therefore, it was possible to obtain a liquid crystal cell having uniform and stable orientation, excellent characteristics such as high-speed response and memory property and long life.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal cell according to an embodiment of the present invention, FIGS. 2 and 3 are characteristic diagrams of the liquid crystal cell according to the present invention, and FIG. 4 is a characteristic diagram of liquid crystal cells according to conventional and research examples, and FIG. Is a schematic view of a ferroelectric liquid crystal. (1) (2) ... Substrate, (3) ... Liquid crystal, (5) ... Polymer film, (6) ... Organic polymer film.

Continuation of front page (56) Reference JP-A-61-236523 (JP, A) JP-A-61-286816 (JP, A) JP-A-62-8126 (JP, A) JP-A-62-28713 (JP , A) JP 62-175712 (JP, A) JP-B 6-54368 (JP, B2)

Claims (1)

[Claims] 1. In a liquid crystal cell having two substrates and a ferroelectric liquid crystal sandwiched between the substrates, a spontaneous polarization of the ferroelectric liquid crystal is present on a surface of one substrate in contact with the liquid crystal. Per 5,000 atoms more than one fluoroalkyl chain (C _n
A liquid crystal cell comprising a polymer film containing F _{2n + 1} ), and an organic alignment film for horizontal alignment, which is not subjected to alignment treatment, is provided on the surface of the other substrate in contact with the liquid crystal.