JPH05150242A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To provide a liq. crystal orienting film having uniform liq. crystal orienting property almost free from defects and capable imparting a desired pretilt angle to a liq. crystal without adopting diagonal vapor deposition or rubbing. CONSTITUTION:When a liq. crystal element is composed essentially of a pair of substrates 1 with electrode layers 12 and a liq. crystal 2 sealed between the substrates 1, a thin film 13 for bringing the liq. crystal 2 into homogeneous (homeotropic) orientation is formed on each of the substrates 1 and a liq. crystal orienting film 14 is further formed on the thin film 13 by laminating one or more layers of an amphipatic substance for bringing the liq. crystal 2 into homeotropic (homogeneous) orientation by the Langmuir-Blodgett's method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device having a novel liquid crystal alignment film.

[0002]

2. Description of the Related Art Conventionally, flat displays using liquid crystals have been widely used in watches and televisions. In the liquid crystal display element used for this liquid crystal display, the alignment formed by the oblique vapor deposition method of SiO, Au, etc., or by applying a polyimide-based polymer resin on the substrate and then rubbing it in a certain direction with a cloth etc. A liquid crystal is orientated in a specified direction using a film.

However, the oblique evaporation method is very advantageous for giving a predetermined pretilt angle to the liquid crystal, but since it is vacuum evaporation, it requires a high vacuum of about 10 μTorr.
In addition, it has a drawback that mass productivity is poor because the substrate must be inclined.

Further, the rubbing method has drawbacks such as deterioration of productivity and quality due to dust and static electricity generated during rubbing.

Therefore, there has been a demand for an aligning means capable of aligning liquid crystals without using such a conventional technique.

We have previously proposed a new liquid crystal alignment film using a Langmuir-Blodgett (LB) film, which does not require rubbing treatment, as disclosed in Japanese Patent Laid-Open No. 63-23131. However, the angle (pretilt angle) formed by the glass substrate on which the liquid crystal molecules and the alignment film are formed is larger than 0 degree and must be set to an arbitrary value within the range of several degrees to several tens of degrees. It has been found that it is difficult to give a pretilt angle when the film is used as a liquid crystal alignment film.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art and the problems of the LB film previously proposed by us, and is based on the oblique vapor deposition method and the rubbing method. It is an object of the present invention to provide a liquid crystal alignment film which has a uniform liquid crystal alignment with almost no defects and which can impart a desired pretilt angle to liquid crystals.

[0008]

A first aspect of the liquid crystal element of the present invention
Is a liquid crystal element comprising a pair of bases on which at least an electrode layer is formed and a liquid crystal enclosed between the bases, wherein a thin film for homogeneously aligning the liquid crystal is formed on the base, and further on the thin film. Further, it is characterized in that a liquid crystal alignment film is formed by laminating one or more layers of an amphipathic substance for homeotropically aligning liquid crystals by the Langmuir-Blodgett method.

A second aspect of the liquid crystal element of the present invention is a liquid crystal element comprising at least a pair of bases on which electrode layers are formed and a liquid crystal enclosed between the bases, wherein the liquid crystal is homeomeric on the base. A thin film for tropic alignment is formed, and a liquid crystal alignment film is further formed on the thin film by laminating at least one layer of an amphipathic substance for homogeneously aligning liquid crystals by the Langmuir-Blodgett method.

In the present invention, the thin film formed on the electrode layer is preferably a thin film formed by the Langmuir-Blodgett method.

Further, in the present invention, the film thickness of the thin film formed by the Langmuir-Blodgett method formed on the outermost surface in contact with the liquid crystal is preferably 10Å to 100Å.

[0012]

According to the research conducted by the present inventors, the pretilt angle can be imparted to the liquid crystal by combining the liquid crystal alignment film for homogeneously aligning the liquid crystal (pretilt angle is 0 degree) with the liquid crystal alignment film for homeotropic alignment. It turns out to be possible. However, at that time, if a liquid crystal alignment film forming method such as a spin coating method is used, a film thickness of several hundred Å or more can be obtained, so that the alignment of the liquid crystal is determined only by the properties of the alignment film surface in contact with the liquid crystal. There is.

Therefore, as a result of further research on this point, the present inventors found that the property of imparting a pretilt angle to the liquid crystal depends on the portion of 10 Å to 100 Å on the surface of the alignment film in contact with the liquid crystal, particularly the portion of 10 Å to 50 Å. I found that it was decided.

Further, it was also found that it is possible to sequentially change the contribution of the liquid crystal on the surface of the alignment film to the pretilt angle by changing the film thickness of the surface of the alignment film within the above range, and complete the present invention. Came to. That is, the alignment film forming means employed in the present invention must be capable of controlling the film thickness to a desired thickness. This point, L
Method B is the most suitable means for realizing the present invention, because the film thickness can be changed by the monomolecular film thickness. As an LB film for homogeneously aligning liquid crystals, a polyimide LB film proposed by the applicant of the present application in JP-A-63-23131 was proposed.
You can raise the membrane. Examples of the LB film for homeotropically aligning the liquid crystal include a polyimide precursor LB film and a fatty acid such as stearic acid.

Examples of the thin film formed on the electrode used in the present invention and not in contact with the liquid crystal include the LB film described above and the rubbing film used in the prior art.
There is no particular limitation. Furthermore, they may not be particularly capable of uniaxially aligning liquid crystals.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the accompanying drawings, but the present invention is not limited to such embodiments.

FIG. 1 is a schematic view of an embodiment of the liquid crystal element of the present invention, and FIG. 2 is a structural view of the essential parts of the liquid crystal element of the present invention. In the figure, 1 is a substrate, 2 is a liquid crystal, 3 is a seal, 11 is a transparent substrate, 12 is a transparent conductive film, 13 is a base layer thin film, 14 is a surface layer thin film, and the base layer thin film 13 and the surface layer thin film are shown. 1
4 together form an alignment film.

The underlayer thin film 13 is made of an organic polymer such as polyvinyl alcohol or polyimide, or an inorganic material such as SiO ₂ or Al ₂ O ₃ , and is formed by spin coating, dipping,
It is formed by a printing method, an LB method, or a vacuum evaporation method. The film thickness is not particularly limited, but a film thickness of 1 μm or less is preferable in order to effectively apply a voltage to the liquid crystal 2 in the liquid crystal element. It is also possible to form the underlayer thin film 13 by directly subjecting the surfaces of the substrate 11 and the transparent conductive film 12 to silane coupling treatment or DMOAP treatment.

The surface layer thin film 14 is made of an organic polymer such as polyimide or polyamide or a known amphipathic material for LB film such as stearic acid, and is formed by a film forming method capable of forming a thin film of 100 Å or less. The LB method is one of the most preferable examples of this film forming method. The film thickness is 100 Å in order to leave the influence of the underlayer thin film 13 on the pretilt of the liquid crystal 2.
Hereinafter, it may be in the range of 10 Å or more, but in order to effectively use the influence of both the underlayer thin film 13 and the surface layer thin film 14 on the liquid crystal pretilt, 50 Å or less and 10 Å
It is preferably within the above range.

The other structure is the same as that of the conventional liquid crystal element, and therefore the detailed description of the structure is omitted.

Next, the present invention will be described in more detail based on more specific examples.

Example 1 A liquid crystal 2 having a repeating unit represented by Chemical Formula 1 having a thickness of 1000Å and a viscosity η _inh of 0.85 dl / g on a glass substrate 11 having an ITO electrode layer 12 formed thereon. The polyimide thin film (underlying layer thin film 13) for homogeneously orienting is spin-coated under a spin coating condition of 1000 RPM.
Formed under.

[0023]

[Chemical 1]

Further, it has a repeating unit represented by the chemical formula 2 obtained by reacting acid chloride of pyromellitic acid distearyl ester with paraphenylenediamine on the underlayer thin film 13, and has a number average molecular weight of about 5,000. A certain polyimide precursor was prepared by the Langmuir-Blodgett method (L
One layer was accumulated by the method B). The thickness of the obtained LB film (surface layer thin film 14) was about 20Å.

[0025]

[Chemical 2]

Two substrates 1 of the same treatment are prepared and a liquid crystal cell is constructed so that the pulling-up directions of the two substrates 1 when forming the LB film are antiparallel to each other.
As the sealing resin 3 on the surface on which the transparent electrode layer 12 is formed, an acid anhydride-curable epoxy resin in which plastic beads having a diameter of 20 μm are dispersed is used, and only one side is 5 mm in the center of the side.
After printing with a width of 1 mm on all other circumferences with the length left, pressure was applied in a state where the transparent electrodes 12 were opposed to each other, and heating was performed at 140 ° C. for 3 hours for curing and adhesion. After the adhesion, nematic liquid crystal (ZLI1565 (trade name) manufactured by Merck & Co., Inc.) was injected from the opening under reduced pressure. After the injection, the opening was fixed with a commercially available acid anhydride-curable epoxy resin and the liquid crystal 2 was sealed to complete an anti-parallel type liquid crystal cell. The completed liquid crystal cell was once heated to 100 ° C. and then gradually cooled to be initially aligned, whereby a uniform, defect-free, and excellent alignment liquid crystal cell was obtained.

Further, as a result of measuring the pretilt angle of the liquid crystal 2 by the crystal rotation method, it was about 2 degrees.

Example 2 An anti-parallel type liquid crystal cell was produced in the same manner as in Example 1 except that the number of LB film layers was three. As a result of measuring the pretilt angle of the liquid crystal 2 in the cell by the crystal rotation method, it was about 20 degrees.

Comparative Example 1 A glass substrate having an ITO electrode layer formed thereon had a thickness of 100.
A polyimide precursor thin film having a repeating unit represented by Chemical Formula 3 of Å and having a number average molecular weight of about 5000 was formed by the LB method.

[0030]

[Chemical 3]

An antiparallel type liquid crystal cell was prepared by using two sheets of the same treated substrate as described above. The liquid crystal in the cell did not have a pretilt angle and was homeotropically aligned.

Example 3 A substrate 100 having an ITO electrode layer 12 formed thereon had a thickness of 100.
An underlayer thin film 13 having a repeating unit represented by Chemical Formula 4 of Å and having a viscosity η _inh of 0.85 dl / g was formed by the LB method.

[0033]

[Chemical 4]

Further, it has a repeating unit represented by the chemical formula 5 obtained by reacting acid chloride of pyromellitic acid distearyl ester and paraphenylenediamine on the underlayer thin film 13, and has a number average molecular weight of about 5,000. One layer of a certain polyimide precursor was accumulated by the LB method. The thickness of the obtained LB film (surface layer thin film 14) was about 20Å.

[0035]

[Chemical 5]

An anti-parallel type liquid crystal cell was produced by using the same two substrates 1 to be treated. The pretilt angle of the liquid crystal 2 in the cell was measured by the crystal rotation method, and it was about 2 degrees.

Example 4 On the substrate 11 on which the ITO electrode layer 12 was formed, a DMOAP treatment was carried out for homeotropic alignment of the liquid crystal 2 to form an underlayer thin film 13.

Further, the underlayer thin film 13 has a repeating unit represented by the chemical formula 6 obtained by reacting acid chloride of pyromellitic acid distearyl ester with paraphenylenediamine, and has a number average molecular weight of about 5,000. Five layers of a certain polyimide precursor are accumulated by the LB method, and the temperature is 400 ° C.
And heat treated for 1 hour. Obtained LB film (surface layer thin film 1
The film thickness of 4) was 25Å.

[0039]

[Chemical 6]

An anti-parallel type liquid crystal cell was prepared using the same two treated substrates 1. The pretilt angle of the liquid crystal 2 in the cell was measured by the crystal rotation method, and it was about 5 degrees.

As is clear from the comparison between Examples 1 to 4 and Comparative Example 1 described above, in the present invention, the underlayer thin film for controlling the pretilt of the liquid crystal and the surface layer portion giving a pretilt angle different from that of the underlayer thin film. Since the alignment film is formed in combination with the thin film, it can be seen that the alignment film capable of imparting a desired pretilt angle to the liquid crystal can be formed on the substrate.

In the present specification, the present invention has been described based on the preferred embodiments, but the liquid crystal and liquid crystal element types to which the present invention can be applied are not particularly limited, and TN type using nematic liquid crystal other than ZLI1565 is used. A liquid crystal element, a guest-host type liquid crystal element, an STN type liquid crystal element, or a ferroelectric liquid crystal element can be preferably used. Further, the method for forming the alignment film and the material for the alignment film are not particularly limited as long as the film thickness and the force of imparting pretilt to the liquid crystal satisfy the requirements of the present invention.

[0043]

As described above, according to the present invention,
A liquid crystal element having uniform alignment of liquid crystal and a desired pretilt angle can be obtained without rubbing an alignment film in contact with the liquid crystal.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of a liquid crystal element of the present invention.

FIG. 2 is a structural diagram of a main part of a liquid crystal element of the present invention.

[Explanation of symbols]

 1 Base 2 Liquid Crystal 3 Seal 11 Substrate 12 Transparent Conductive Film 13 Underlayer Thin Film 14 Surface Layer Thin Film

Claims (4)

[Claims] 1. A liquid crystal element comprising a pair of bases on which at least electrode layers are formed and a liquid crystal enclosed between the bases, wherein a thin film for homogeneously aligning the liquid crystal is formed on the base, and the thin film is further formed. A liquid crystal device comprising a liquid crystal alignment film formed by laminating one or more layers of an amphipathic substance for homeotropically aligning liquid crystal by a Langmuir-Blodgett method thereon. 2. A liquid crystal device comprising a pair of bases having at least electrode layers formed thereon and liquid crystals enclosed between the bases, wherein a thin film for homeotropically aligning the liquid crystal is formed on the bases, and further comprising: A liquid crystal device comprising a thin film and a liquid crystal alignment film formed by laminating one or more layers of an amphipathic substance for homogeneously aligning liquid crystal by a Langmuir-Blodgett method. 3. The liquid crystal device according to claim 1, wherein the thin film formed on the electrode layer is a thin film formed by the Langmuir-Blodgett method. 4. The liquid crystal according to claim 1, 2 or 3, wherein the thin film formed by the Langmuir-Blodgett method on the outermost surface in contact with the liquid crystal has a film thickness of 10Å to 100Å. element.