JPH0718997B2 - Method for manufacturing ferroelectric liquid crystal device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a crystal element using a ferroelectric liquid crystal, and more particularly to a method for aligning a ferroelectric liquid crystal.

(Prior Art) Liquid crystal elements have been extensively researched and developed as direct-view display elements, and are now widely used. The liquid crystal material used in conventional liquid crystal elements is nematic liquid crystal TN
Liquid crystal, STN liquid crystal. However, the response time of TN liquid crystal and the like was long and the application range was limited.

In recent years, a ferroelectric liquid crystal has been developed as a liquid crystal having a short response time, and its speed has been increased. Here, the operation of the ferroelectric liquid crystal will be described. The fast response behavior of ferroelectric liquid crystals was confirmed by Noel A. Clark and Sven T. Lagerwall (Appl. Phys.Let
t.36 (1980) 899)). That is, a chiral smectic liquid crystal exhibiting ferroelectricity has spontaneous polarization as shown in FIG.
The liquid crystal molecule 22 having 21 has a layered structure and a spiral structure. In this state, the spontaneous polarization 21 is evenly distributed around the spiral axis 23 to cancel each other out. However, such a liquid crystal is sandwiched between the substrates 31 and 32 that have been subjected to two alignment treatments parallel to the spiral axis 23. And, if the distance, that is, the thickness of the liquid crystal is reduced to at least the pitch length of the spiral structure or less,
The liquid crystal molecules 22 are forcibly aligned in one of two alignment states in which the spontaneous polarization 23 is perpendicular to the substrate. FIG. 3 is a diagram showing the situation, and the region A is the spontaneous polarization.
The region 21 is in a state in which it faces the lower substrate, and the region B is in a state in which the spontaneous polarization 21 faces in the upper substrate. FIG. 4 is a view as seen from the upper surface of the substrate, in which the liquid crystal molecules in the regions A and B have different alignment states as indicated by 41 and 42. For example, when such a state is sandwiched between two polarizing plates whose polarization directions are orthogonal to each other and the polarization direction 43 of one polarizing plate is aligned with the direction of liquid crystal molecules, the region A looks dark and the region B looks bright. In this way, when a chiral smectic liquid crystal exhibiting ferroelectricity is sandwiched between two substrates having a narrow interval, the liquid crystal molecules come to one of two optically distinguishable alignment states. Moreover, the spontaneous polarization of the ferroelectric liquid crystal is oriented in direct response to the external electric field. Therefore, by applying a DC electric field in the direction perpendicular to the substrate from the outside,
When the direction is reversed, the direction of spontaneous polarization is reversed accordingly. That is, the area A and the area B in FIG. 4 are electrically switched, and this can be easily realized by forming transparent electrodes or the like inside the two substrates. Furthermore, since this electrical switching phenomenon is due to a direct response between spontaneous polarization and an external electric field, it is extremely fast, and the above-mentioned paper confirms a response time in the microsecond range.

Further, even after the voltage is removed, the alignment state when the voltage is applied is
Ferroelectric liquid crystals have the property of being retained. This is commonly called bistability.

As a method for aligning ferroelectric liquid crystals, a rubbing method and an oblique evaporation method used in TN liquid crystals have been proposed.

(Problems to be Solved by the Invention) In a liquid crystal element using the above-mentioned rubbing method as an alignment treatment, it is difficult to form uniform grooves on the surface of the alignment film. Due to the homogeneity, sufficient optical response characteristics, especially bistability, cannot be obtained over the entire liquid crystal element. Also, in oblique vapor deposition, it is necessary to use a large-scale device to create a large-area and uniform liquid crystal element,
Furthermore, there is a problem in mass productivity.

The object of the present invention is to eliminate the above-mentioned drawbacks, stack a film with good uniformity on the substrate, and form uniform unevenness, thereby providing a high-speed response and bistable operation characteristic of a ferroelectric liquid crystal. It is an object of the present invention to provide a method for manufacturing a ferroelectric liquid crystal device, which can realize the device with a large area.

(Means for Solving the Problems) The present invention relates to a method for manufacturing a ferroelectric liquid crystal device having a structure in which a ferroelectric liquid crystal is sandwiched between two substrates with electrodes on which electrodes are formed. At least one layer of a photosensitive organic substance developed on the water surface is laminated on the substrate, and then exposed and developed to partially remove the organic substance to form irregularities on the substrate surface. It is characterized in that a ferroelectric liquid crystal is laminated on top of it.

(Function) The alignment mechanism of the ferroelectric liquid crystal has not been clarified yet. However, when we devise the rubbing method and the oblique deposition method, which have been able to achieve some effect,
The reason why the ferroelectric liquid crystal is aligned can be estimated to some extent. The rubbing method is a method in which a polymer film such as polyimide is coated on a substrate and then the surface is unidirectionally rubbed with a cotton cloth or the like. Further, the oblique vapor deposition method is a method in which the substrate is inclined with respect to a vapor deposition source such as SiO 2 to perform vapor deposition. In either case, it can be inferred that the ferroelectric liquid crystal is aligned by forming some physical shape on the substrate surface with uniaxiality.

By the way, a homogeneous organic thin film can be formed on a substrate by spreading an organic substance on the water surface and attaching the organic film to the substrate. The film formed by this method is usually called an LB (Langmuir-Brodget) film. This LB film can be laminated in any number of layers, and the thickness of the film on the substrate can be freely changed. In particular, by using an LB film made of an organic substance containing a photosensitive functional group, desired unevenness can be formed simply by exposing and developing through a mask while maintaining the above characteristics.

By forming a pattern, for example, in a stripe pattern on the LB film on the substrate described above, unevenness having uniaxiality can be formed on the substrate surface. A ferroelectric liquid crystal element is obtained by forming a liquid crystal element using this substrate and injecting a ferroelectric liquid crystal. In this device, since uniform irregularities are formed on the surface of the substrate, the ferroelectric liquid crystal molecules are aligned. Further, by sandwiching the element between polarizing plates, the ferroelectric liquid crystal can be switched to be used as a light modulation liquid crystal element.

(Examples) Hereinafter, examples of the present invention will be described in detail.

A ferroelectric liquid crystal element as shown in FIG. 1 was produced by the method as described below. Polyamic acid synthesized from pyromellitic anhydride and diaminodiphenyl ether and 4- (17-octadecenyl) pyridine mixture (1: 2) were dissolved in benzene and dimethylacetamide mixed solution (1: 1) to give 1.7 mM and 3.3 mM concentrations, respectively. A sample solution was prepared. Next, ITO (indium oxide, tin) was patterned on the surface as the transparent electrode 1 to form it on the glass substrate 2. By deploying the sample solution on the water surface of a water tank with a feedback mechanism for keeping the surface pressure constant, and keeping the surface pressure at 25 mN / m by the feedback mechanism, moving the glass substrate 2 up and down across the water surface, On the glass substrate 2, 10 layers of LB film, that is, polyimide film 3 composed of a mixture of polyamic acid and 4- (17-octadecenyl) pyridine (1: 2) were laminated. Then, Deep UV exposure was performed using a line-and-space 0.5 μm stripe-shaped mask, and development was performed for 5 minutes with a 1: 1 mixture of benzene and dimethylacetamide to pattern the LB film. Using this substrate, a liquid crystal element was created to have a gap of 2 μm, CS-1015 (manufactured by Chisso), which was a ferroelectric liquid crystal 4, was injected, and the alignment state was observed using a polarization microscope. Was confirmed. When the contrast ratio was measured as the optical response characteristic of the liquid crystal element, 30 was obtained. Also, good bistability behavior was confirmed.

Although CS-1015 was used as the ferroelectric liquid crystal in the above embodiments, various other liquid crystals such as ZLI-3489 (manufactured by Merck) and
It can be applied to CS-1011 (made by Chisso).

In this method, the liquid crystal material used is different compared to the rubbing method, and the physical constants such as the molecular structure and the spontaneous polarization of the liquid crystal are different.
Even if the alignment conditions are different, it is easy to change the type of film to be laminated, the number of layers to be laminated, and the pitch of the concavities and convexities, so that it is possible to easily realize a surface state that matches the alignment condition of the liquid crystal material used. . Further, since a uniform film is formed, no alignment failure occurs in the liquid crystal element. Moreover, it is easy to deal with a large area as compared with the oblique deposition.

(Effects of the Invention) As described above, according to the manufacturing method of the present invention, since a liquid crystal element having a good orientation can be obtained, the optical response characteristics are excellent and it is easy to deal with a large area.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a ferroelectric liquid crystal device showing an embodiment of the present invention, FIG. 2 is a schematic view showing a state of spiral alignment of ferroelectric liquid crystal molecules, and FIGS. 3 and 4 are between substrates. FIG. 3 is a side view and a plan view schematically showing an alignment state of ferroelectric liquid crystal molecules. 1 ... Transparent electrode, 2 ... Glass substrate 3 ... LB film, 4 ... Ferroelectric liquid crystal 21 ... Spontaneous polarization, 22, 41, 42 ... Liquid crystal molecule 23 ... Spiral axis, 31, 32 ... Substrate 43 ... Polarization axis

Continuation of the front page (56) Reference JP 62-291620 (JP, A) JP 57-81234 (JP, A) JP 60-21026 (JP, A) JP 60-60624 (JP , A) JP-A-61-109025 (JP, A) JP-A-61-249046 (JP, A)

Claims (1)

[Claims] 1. In a method of manufacturing a ferroelectric liquid crystal device having a structure in which a ferroelectric liquid crystal is sandwiched between two substrates with electrodes formed with electrodes, polyamic acid and the following structural formula are provided on the substrate. A step of laminating one or more layers of organic monomolecular films made of a mixture of the organic substances shown, a step of forming irregularities on the surface of the substrate by removing a part of the organic substance thereafter, And a step of laminating a ferroelectric liquid crystal thereon.