JPH04190328A - Ferroelectric liquid crystal display element and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display plate which has uniform orientation with little unevenness in orientation without after-treatment such as rubbing or the like and has good memory capability by providing an orientation control film of a specified compound and using a specified ferroelectric liquid crystal. CONSTITUTION:An orientation control film composed of a polyamide acid in which one component of a compound having the property of being expanded on the water surface to form a monomolecular film has a long-chain alkyl substitutional group is provided on a base 11 where at least an electrode layer 12 is formed, a ferroelectric liquid crystal having the spontaneous polarization of 15nc/cm<2> - 50nc/cm<2> is provided in a liquid crystal supporting plate opposed space, and a ferroelectric liquid crystal display element is subjected to a.c. filed processing. Thus, it is possible to obtain a high grade display plate easily at a low cost, in which uniform orientation with little unevenness in orientation can be obtained without after-treatment such as rubbing or the like. Further, a ferroelectric liquid crystal display element which has good memory capability can be manufactured by using a ferroelectric liquid crystal having the spontaneous polarization of 15nc/cm<2> - 50nc/cm<2> and applying a.c. field processing thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ferroelectric liquid crystal display device using an LB film as an alignment film and a method for manufacturing the same.

Conventional Technology Liquid Crystal Displays (LCDs) are used today from watches to color T-shirts.
It is being developed into a wide variety of applications, including V. Along with this, demands for improved performance have become increasingly loud and severe. Performance that will need to be improved in the future includes response speed, contrast pixel count, larger area, productivity, lower cost, and wider viewing angle.

As one means to meet these demands, there is a so-called TFT type liquid crystal display element which is fabricated directly on a glass substrate using a thin film transistor as an electrode.

Although this method provides high contrast and good response, it is very difficult to manufacture and has the disadvantage that, especially when increasing the area, the manufacturing yield drops rapidly and therefore costs increase.

On the other hand, there is a so-called super twist (S T N) type liquid crystal display element for the purpose of increasing the contrast and widening the viewing angle of the conventional twisted nematic (TN) type monocrystalline display element, but STN has a slower response speed. There was a drawback.

On the other hand, display elements using a rubbed alignment film and ferroelectric liquid crystals have extremely fast response speed of the liquid crystal itself, have memory properties, and can provide high-contrast displays. This is a promising method.

Problems to be Solved by the Invention However, this ferroelectric liquid crystal display element is more difficult to manufacture than conventional TN type liquid crystal display elements. In other words, it is difficult to obtain a good initial alignment simply by rubbing using conventional alignment film materials. The rubbing method is a simple method in which an alignment film (usually a polyimide film is used) coated on the electrode is rubbed in a fixed direction with a woven cloth, etc., so it is low cost, but it allows for a larger area and an increase in the number of pixels. As this became more desirable, defects such as insufficient display uniformity and missing pixels due to dust generated during rubbing became important problems. Furthermore, it has been extremely difficult to eliminate zigzag defects that are unique to ferroelectric liquid crystal display elements. On the other hand, as a method for aligning liquid crystal without rubbing, there is an oblique evaporation method. According to this method, it is possible to manufacture an LCD with good display performance, but it requires a large number of man-hours and leaves unresolved problems in terms of increasing the area and reducing costs.

Therefore, there has been a need for a method for efficiently obtaining good initial orientation without rubbing.

Means for Solving the Problem In order to solve this problem, the ferroelectric liquid crystal display element of the present invention has the property of being developed on a water surface to form a monomolecular film on a substrate on which at least an electrode layer is formed. An alignment control film made of a polyamic acid having a long-chain alkyl substituent as one component of the compound is provided, and the magnitude of spontaneous polarization of the liquid crystal is between 15 n c/cd and 50 n c/d during the facing distance between the liquid crystal support plates.
It is equipped with a CD ferroelectric liquid crystal, and the ferroelectric liquid crystal display element is subjected to alternating current electric field treatment.

Effect: With this configuration, without post-processing such as rubbing,
A high-quality display with uniform orientation with little unevenness can be easily obtained at low cost.

Moreover, the spontaneous polarization is I 5 n c /ci! ~50
By using a ferroelectric liquid crystal of n c /d and subjecting it to alternating current electric field treatment, a ferroelectric liquid crystal display element having good memory properties can be manufactured.

EXAMPLE Hereinafter, a ferroelectric liquid crystal device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic structure of a liquid crystal display element of the present invention.

As shown in FIG. 1, a transparent electrode layer 12, an insulating film 13, and an alignment control film 14 are formed on the surfaces of a pair of substrates 11, respectively, and the pair of substrates 11 are bonded together with a sealing resin 15, leaving a gap. The liquid crystal layer 16 is formed by injecting liquid crystal into the liquid crystal layer.

As a method of transferring a monomolecular film onto a substrate, the Langmuir project (Lang+muir-Bl) has traditionally been used.
The method (hereinafter abbreviated as LB method) is used for boat fishing, and the film obtained by this LB method is called LB film. FIG. 2 shows an outline of film formation by the LB method.

As shown in FIG. 2, the monomolecular film 24 developed on the surface of water 25 is pulled up in the pulling direction 23 of the glass substrate 21, and the monomolecular film 22 is transferred from the water surface to the surface of the glass substrate. The method for forming the monomolecular film 22 is as follows: First, a compound capable of forming a monomolecular film is dissolved in an organic solvent, and this is dropped onto the water surface to spread the compound on the water surface. Then,
The monomolecular film 24 spread out on the water surface is compressed until it reaches a certain surface pressure, and becomes a so-called solid film state.

Further, while keeping the surface pressure of the monomolecular film 24 spread on the water surface constant so as not to destroy the solid film state, the indium film 24 is spread in a predetermined pattern across the monomolecular film 24 spread on the water surface. - Raise and lower the glass substrate 21 on which a transparent electrode (ITO electrode) made of a stannic acid compound is formed,
The monolayer was transferred onto a substrate. By varying the number of crossings of the water surface, the desired number of monolayers was accumulated.

FIG. 3 shows the structure of a film accumulated on a substrate by the LB method. As shown in Figure 3, pull up the glass substrate in direction 3.
By pulling up in three directions, an unaccumulated portion 31 and an accumulated portion 32 are formed. Note that an unaccumulated portion 31 was left at one end of the transparent electrode to ensure conductivity. Alternatively, an insulating thin film such as a silicon oxide film may be formed in advance on the TO transparent electrode, and an LB film may be accumulated thereon. Two glass substrates on which LB films were formed as alignment control films by this method were held with the LB film surfaces facing each other,
I glued this.

FIG. 4 shows the structure of a ferroelectric liquid crystal cell obtained by the present invention. As shown in FIG. 4, an upper substrate 41 and a lower substrate 4 are shown.
Alignment films are formed on the substrates 2 and 2 by pulling them in opposite directions, and are bonded with a sealing resin 45. Upper substrate pulling direction 43. The alignment film is pulled up in the pulling direction 44 of the lower substrate. That is, as shown in FIG. 4, an acid anhydride-curable epoxy resin composition in which spherical spacers of a constant diameter are dispersed is printed as a sealing resin 45 on four sides, including a portion of two sides of a glass substrate. The resin was temporarily cured by heating at 70° C. for 4 hours under pressure, and then heated at 140° C. for 4 hours to harden the resin, and the two glass plates were bonded together. The two glass plates thus bonded together are called a cell, and liquid crystal was injected under reduced pressure through the opening of this cell. After injection, the opening was sealed with an acid anhydride-curable epoxy resin to complete the liquid crystal cell. The compounds with the ability to form a monomolecular film here are so-called amphiphilic substances that have both a hydrophilic group and a hydrophilic group in their molecules. An alcohol having a long chain alkyl group having 16 to 22 carbon atoms, such as a metal salt.

Carboxylic acids and their metal salts, and derivatives thereof,
Or JP-A No. 62-61673.

Polyamides having long-chain alkyl substituents as disclosed in JP-A-62-129317 can be used alone or in combination.

Note that, from the viewpoint of stability of the heat-resistant two-layer film, it is preferable to use a polymeric compound as the main component. In this way, LB
A ferroelectric liquid crystal display element using wA as an alignment film exhibits the property that the liquid crystal is aligned without a rubbing treatment, and can also exhibit good display quality with little alignment unevenness. Figures 5(a) and 5(b) show a ferroelectric liquid crystal display device using a ferroelectric liquid crystal (trade name: ZL13654, manufactured by Merck & Co., Ltd.) exhibiting a spontaneous polarization of 29 nc/cd, and subjected to alternating current electric field treatment. In the diagram, O is the maximum relative brightness when a voltage is applied and represents the bulk response, and × is the relative brightness after scanning a series of measurement waveforms for 1000 lines. , which represents a memory response, and it can be seen from this figure that it exhibits a steep threshold and good memory performance.

Although the ferroelectric liquid crystal to be used is not limited to this, it is considered appropriate that the magnitude of its spontaneous polarization is 15 to 50 nc/cij or more.

Hereinafter, the present invention will be explained in more detail using specific examples.

Example 1 A polyimide precursor (PIF) obtained by reacting the acid chloride of pyromellitic acid distearyl ester with 4,4'-diaminodiphenyl ether and a polyamide (
PA) was dissolved in a mixed solvent of dimethylacetamide and chloroform at a molar ratio of 1:1, and used to prepare a glass plate (75
Five layers of a mixed LBWA of PIF and PA were accumulated on the cabinet (X25m) using the method described above. PIF having an alkyl substituent having 14 carbon atoms was used. Two glass substrates of the same treatment are prepared, and as shown in FIG.
4 are in opposite directions to each other, and the lower substrate 4
As a sealing resin 45 on the surface on which the transparent electrode layer of No. 2 is formed,
After printing acid anhydride-curing epoxy resin in which plastic beads with a diameter of 2.0 μm are dispersed, leaving 5 stripes in the center of the two sides and 1 strip on the entire other circumference, as shown in Figure 1. The transparent electrode layers 12 were pressed while facing each other, and heated at 70° C. for 4 hours and at 140° C. for 4 hours to cure and bond. After adhesion, ferroelectric liquid crystal (trade name ZL13654, manufactured by Merck & Co., spontaneous polarization 29 n c /d) was injected from the opening under reduced pressure. After injection, the opening was fixed with a commercially available acid anhydride-curable epoxy resin to seal the liquid crystal and complete a ferroelectric liquid crystal cell. By heating the completed ferroelectric liquid crystal cell to 100° C. and then gradually cooling it for initial alignment, a cell in a good alignment state with little alignment unevenness was obtained. By subjecting this ferroelectric liquid crystal cell to an alternating current electric field treatment of 30 V and 10 Hz, good memory properties as shown in FIGS. 5(a) and 5(b) were obtained.

Example 2 The ferroelectric liquid crystal to be press-fitted was made by Chinso Co., Ltd., product name C5.
-1022 (spontaneous polarization 26.4 n c /c+a), and a ferroelectric liquid crystal cell using C5-1022 was produced in the same manner as in Example 1. By heating the completed ferroelectric liquid crystal cell to 100° C. and then gradually cooling it for initial alignment, a cell in a good alignment state with little alignment unevenness was obtained.

Good memory properties were obtained by subjecting this ferroelectric liquid crystal cell to a 30 V, 107 AC electric field treatment.

Example 3 The ferroelectric liquid crystal to be injected was manufactured by Chisso Corporation, trade name C5.
-1019 (spontaneous polarization 16.5 n c /cd), and a ferroelectric liquid crystal cell using C5-1019 was produced in the same manner as in Example 1. By heating the completed ferroelectric liquid crystal cell to 100° C. and then gradually cooling it for initial alignment, a cell in a good alignment state with little alignment unevenness was obtained.

Good memory properties were obtained by subjecting this ferroelectric liquid crystal cell to an AC electric field treatment of 30 V and 10 Hz.

Comparative Example 1 The ferroelectric liquid crystal to be injected was manufactured by Merck & Co., trade name: ZLI34.
88 (spontaneous polarization of 9.7 n c /c ()), and a ferroelectric liquid crystal cell containing ZLI3488 was prepared in the same manner as in Example 1. The completed ferroelectric liquid crystal cell was once
By heating to 00'C and then gradually cooling to achieve initial orientation, a cell with good orientation with little alignment unevenness was obtained. Stable memory performance could not be obtained.

Comparison 2 The ferroelectric liquid crystal to be injected was manufactured by Chisso Corporation, product name C5.
-1023 (spontaneous component N 13.4 n c /d), and a ferroelectric liquid crystal cell using C5-1023 was produced in the same manner as in Example 1. By heating the completed ferroelectric liquid crystal cell to 100'C and then gradually cooling it for initial alignment, a cell with good alignment with little alignment unevenness was obtained. Even after the treatment, stable memory performance could not be obtained.

In this example, PIF having 14 carbon atoms was used, but similar results were obtained even if PIFs having varying carbon numbers in the range of 14 to 20 were used.

In this example, a vertical dipping method was used as a method for forming the LB film, but a rotating cylinder method or a horizontal deposition method known for boat fishing may also be used.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, one component of a compound that has the property of spreading on a water surface to form a monomolecular film is placed on a substrate on which an electrode layer is formed. By providing an alignment control film made of polyamide containing long-chain alkyl substituents, it is possible to obtain a liquid crystal display panel with uniform alignment with little alignment unevenness without post-treatment such as rubbing. Furthermore, the magnitude of spontaneous polarization is 15 to 50 n c
By using a ferroelectric liquid crystal of /cd or higher and subjecting it to alternating current electric field treatment, a ferroelectric liquid crystal display element having a high-quality display and good memory properties can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a ferroelectric liquid crystal display element according to an embodiment of the present invention, FIG. 2 is a diagram showing an outline of the LB method, and FIG.
The figure is a plan view showing a film accumulated on a substrate by the LB method.
FIG. 4 is a plan view showing a ferroelectric liquid crystal display cell obtained according to an embodiment of the present invention, FIG. 5(a) and FIG. 51)
is a graph showing the electro-optical characteristics of the same ferroelectric liquid crystal display cell, and FIGS. 6(a) and 6-) are graphs showing the electro-optic characteristics of the ferroelectric liquid crystal display cell of the comparative example. 11...Substrate, 12...Transparent electrode layer,
13... Insulating layer, 14... Orientation side ms
, 15... Sealing resin, 16... Liquid crystal layer, 21... Glass substrate, 22... Transferred monomolecular film, 23... ...Lifting direction, 2
4... Monomolecular film spread on the water surface, 25...
...Wednesday, 31...Unaccumulated part, 32...
- Accumulation part, 33... Pulling direction, 41...
...Top board, 42...Bottom board, 43...
...Lifting direction of the upper board. Name of agent: Patent attorney Haruaki Kobuki Two idiots 1s4 Figure 5 ((L') (filial) Seal, 11c+t IE cV
rp Nofro 1-His Ball Knee (vn Figure 6 (It) (6)

Claims (3)

[Claims] (1) An alignment control film formed of a monomolecular film mainly composed of a compound that is developed on a water surface to form a monomolecular film is provided on a substrate on which at least an electrode layer is formed, and a pair of liquid crystal support plates are connected to each other. The membranes are kept facing each other, exhibit ferroelectricity during the gap between the membranes, and have a spontaneous polarization of 15 nc/cm^2~5.
A ferroelectric liquid crystal display element in which 0 nc/cm^2 liquid crystal is injected and held. (2) The ferroelectric liquid crystal display element according to claim 1, wherein one of the components of the compound having the property of forming a monomolecular film is a polyamide having a long-chain alkyl substituent. (3) An alignment control film formed of a monomolecular film mainly composed of a compound that is developed on a water surface to form a monomolecular film is provided on a substrate on which at least an electrode layer is formed, and a pair of liquid crystal support plates are connected to each other. A ferroelectric liquid crystal display element in which alternating current electric field treatment is applied to a ferroelectric liquid crystal display element in which liquid crystal is held facing each other and exhibits ferroelectricity during the film facing interval, and whose spontaneous polarization is 15 nc/cm^2 or more is injected and held. Manufacturing method for liquid crystal display elements.