JPH03288131A - Formation of oriented film and production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To prevent the destruction of the circuits on an element surface and the sticking of dust by printing the high-polymer liquid crystal thin film on a printing roll onto a substrate. CONSTITUTION:The high-polymer film is printed in a liquid crystal state onto the substrate 2 by the printing roll 1 formed with the high-polymer film of a lyotropic liquid crystal. Shearing stresses are applied on the thin film simultaneously with the roll printing and the orientability is imparted to the high- polymer liquid crystal thin film. The liquid crystal high polymer which attains the liquid crystal state having flowability at the time of coating and solidifies at room temp. after coating is used. The liquid crystal state refers to the state in the which the regularity of the position relating to centroid is lost and the orientability of the molecules remain. The problem of the static electricity generated by rubbing is eliminated in this way and the possibility of the destruction of the circuits on the element surface and the sticking of the dust is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming an alignment film and a method for manufacturing a liquid crystal display element using the same.

[Prior Art] Conventionally, as a liquid crystal display element such as a twisted nematic (TN) type liquid crystal display element, a super twist (STN) type liquid crystal display element 5, a ferroelectric liquid crystal display element or an active matrix element having an alignment film, an alignment film is used. When forming polyimide, polyimide-isoindoquinazoline.

Generally used methods include forming an organic polymer film such as polyimide benzimidazene on a substrate and rubbing it in one direction with a rubbing cloth, and obliquely vapor depositing SiO or the like.

[Problems to be Solved by the Invention] However, when using an organic polymer film such as polyimide, the surface is rubbed with a rubbing cloth as a method for -axis orientation, which induces the generation of static electricity and damages the element surface. There are problems such as destruction of circuits and adhesion of dust, etc. On the other hand, the method of diagonally vapor depositing SiO etc. is expensive (also, productivity is low because it uses a vacuum system, and it is difficult to manufacture large liquid crystal display elements). It is unsuitable for mass production.As a way to compensate for these drawbacks of conventional alignment films, it has been proposed to use a thin film of liquid crystalline polymer that exhibits fluidity and is then applied onto a substrate and then imparted with alignment properties. (Unexamined Japanese Patent Publication No. 1-28072)
No. 3.

JP-A No. 1-251015, etc.). It has been found that such polymeric liquid crystalline thin films are oriented by various stresses such as shear stress and by external fields such as magnetic fields.

However, such a method cannot form a patterned alignment film. Further, the alignment direction needs to be adjusted in various directions as viewed from the viewing position on the substrate, but such adjustment is difficult because the coating direction and the alignment direction cannot be changed. Furthermore, since the shear stress applied to the liquid crystal polymer thin film, that is, the orientation, is mainly controlled by the speed in the spreading direction, it is difficult to independently and arbitrarily control the film thickness, the uniformity of the film thickness, and the orientation force. Ta.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and uses a printing roll with a lyotropic liquid crystal polymer film formed on the surface to print the polymer film on a substrate in a liquid crystal state. The present invention provides a method for forming an alignment film, characterized in that printing is performed on an alignment film, and a liquid crystal display device using the same.

As the liquid crystal polymer used in the present invention, various compounds can be used as long as they take a fluid liquid crystal state during coating and solidify at room temperature after coating. Here, the liquid crystal state refers to a state in which the regularity of the position with respect to the center of gravity is lost and the orientation of molecules remains. Among such liquid crystal polymers, lyotropic polymer liquid crystals that can be coated at room temperature can be broadly classified into aramid-based, polypeptide-based, cellulose-based, and the like.

Poly p-phenylene terephthalamide, a type of aramid, exhibits a nematic phase above a certain concentration of sulfuric acid or dimethylacetamide-lithium chloride.

Poly-gamma-benzylic monoglutamate (PBLG), a type of polypeptide, exhibits a cholesteric phase at a concentration of about 10% or more, depending on the molecular weight.

Examples of cellulose include hydroxypropyl cellulose and acetyl cellulose.

Nematic, smectic, and cholesteric phases can be used as the polymer liquid crystal phase.
A preferred liquid crystal phase is a uniaxial nematic without a layered structure.

In addition, since it is used as an alignment film for a liquid crystal element, it is desirable to have heat resistance of 250° C. or higher.

The method for forming an alignment film according to the present invention is characterized by printing a polymer liquid crystal thin film, typified by the above-mentioned example, on a printing roll onto a substrate. That is, in order to impart alignment ability to a polymer liquid crystal thin film without rubbing, it is necessary to apply an external force such as shear stress to the polymer film having liquid crystal properties, but in the present invention, such an external force such as shear stress is applied at the same time as roll printing. By applying significant shear stress, it is possible to impart alignment ability to the polymer liquid crystal thin film. Therefore, alignment film formation without the need for rubbing can be realized with extremely high mass productivity. Furthermore, if a plate is formed on a printing roll, a patterned alignment film can also be formed.

In a preferred embodiment of the present invention, grooves forming a constant angle with respect to the printing direction can be formed on the surface of the printing roll. By doing so, it becomes possible to provide the alignment film with orientation in a direction different from the printing direction. Furthermore, by partially changing the direction of the grooves on the printing roll, it is possible to obtain an alignment film in which the orientation direction partially changes.

The alignment film used in LCDs such as STN is generally oriented at an angle of 0 to 90 degrees other than 0 degrees or 90 degrees with respect to the sides of the substrate. Orientation at such an angle can be achieved by printing on a printing roll plate with grooves formed at an angle between 0 and 90 degrees. Groove pitch is 1 mm or less 1 Normally 10
0 tron to 10 micron. The depth of the grooves, the shape of the ridges, etc. can be designed with reference to the halftone dot shape design method in the field of gravure printing. Additionally, orientation can be imparted to the polymer liquid crystal thin film when the polymer liquid crystal thin film on the printing roll is printed on the substrate, or it can be done at the time when the polymer liquid crystal thin film is provided on the printing roll. It is also possible to set it to a state where it is already oriented.

In order to impart orientation to the polymer liquid crystal thin film on the printing roll, examples include a method of kneading with three rolls for orientation, a method of orientation by squeezing with a blade, and the like. Furthermore, the shear stress can be adjusted by varying the printing speed and the rotational speed of the rolls.

Thin films on printed substrates can be torn off by shear stress, causing misalignment. Such disturbances can be prevented by varying the printing speed and the rotational speed of the rolls and adjusting the shear stress as described above. Specifically, the substrate feeding speed may be adjusted to be different from the roll circumferential speed, or the feeding direction may be reversed.

The method for forming an alignment film of the present invention can be particularly preferably applied to a method for manufacturing a liquid crystal display element. The aspect of such a liquid crystal display cell will be explained below.

The liquid crystal display cell of the present invention includes forming electrodes, color filters, etc. on a substrate, further providing an alignment film by the manufacturing method of the present invention, making the alignment film surfaces face each other, and sealing the peripheral part with a sealing material. It has a liquid crystal sealed inside, and is usually used with polarizing films placed on both sides of the cell and means for applying voltage to the electrodes.

As this substrate, a transparent substrate such as glass or plastic can be used, and its surface is coated with indium tin oxide (ITO).
, SnO□, or other transparent electrodes are formed. of course,
This transparent electrode may be provided with a low-resistance metal lead, or may have an insulating film formed thereon. In the example described above, the color filter is placed above the electrode, but it is also possible to place it below the electrode.

The sealing material is a normal sealing material such as epoxy resin or silicone resin (normally, an opening is formed in a part of the sealing material, and after forming a cell, liquid crystal is injected through the opening, and the liquid crystal is injected through the opening. All you have to do is seal it.

The polarization axes of the pair of polarizing films may be arranged approximately parallel to each other as in the case of a normal negative-tone display liquid crystal display element, or substantially perpendicular to each other as in the case of a normal positive-tone display liquid crystal display element. It may be arranged to do so.

As the driving means for applying a voltage to the electrodes, a driving means used in ordinary liquid crystal display devices can be used, and a driving means that can supply an alternating current voltage higher than a threshold value is usually used.

[Example 1] Poly γ-pendylue Gretamate [Sigma p-51
36 molecular weight (small angle scattering method) 249,700), N
, N-dimethylformamide (DMF) to give a solution with a solid content of 16%. Observe this with a polarizing microscope,
It was confirmed that it was in a nematic phase liquid crystal state.

A mirror-finished roll with a diameter of 50 mm was finely scratched with sandpaper at an angle of 45° from the axial direction. This roll was installed as a platen roll as shown in the conceptual side view of FIG. A small amount of the above solution is supplied to the surface of this roll 1 from the supply port 5, the excess is removed using a doctor knife 6, and the glass substrate 2 having a patterned electrode on the surface is sandwiched between it and the opposing rubber roll 4, and the conveyor is conveyed. The rolls 1 were rotated independently at different speeds while being fed on the glass substrate 2, and the surface of the glass substrate 2 was printed and dried at 100° C. for 30 minutes. Create another similar board and install LCD ZL
1-2140 (Merck & Co.) and seal the surrounding area.
A liquid crystal cell was created. A liquid crystal cell with uniform liquid crystal alignment was obtained.

(Example 2) In Example 1, only a 100 mm square portion of the stainless steel roll was surface-treated with sandpaper. A substrate and a liquid crystal cell with a patterned alignment film forming an angle of 45° with the roll axis direction on a 100 mm square portion were obtained.

[Effect of the invention] Since the liquid crystal alignment film of the present invention does not require a rubbing process,
There is no problem of static electricity generated by rubbing (there is no risk of destroying circuits on the element surface or adhesion of dust), and there is no fear of various display irregularities induced by non-uniform rubbing.

The present invention has great practical value because it stabilizes the alignment film manufacturing process and improves the image quality of liquid crystal displays. Further, the present invention allows partial film formation, and has great practical value.

[Brief explanation of drawings]

FIG. 1 is a side view showing one embodiment of the present invention. 1: Roll 2 Glass substrate

Claims (5)

[Claims] (1) A method for forming an alignment film, which comprises printing on a substrate with the polymer coating in a liquid crystal state using a printing roll on which a lyotropic liquid crystal polymer coating is formed. (2) The method for forming an alignment film according to claim 1, wherein grooves forming a constant angle with the printing direction are formed on the surface of the printing roll. (3) The method for forming an alignment film according to claim 1 or 2, wherein a plate corresponding to a desired pattern is provided on the surface of the printing roll. (4) The method for forming an alignment film according to any one of claims 1 to 3, characterized in that the printing speed and the roll rotation speed are made different. (5) Form an electrode on a pair of substrates, and claim 1 above.
A method for manufacturing a liquid crystal display cell, comprising forming an alignment film by the method described in any one of items 4 to 4, making the surfaces of the alignment film face each other, sealing the peripheral portion with a sealing material, and sealing liquid crystal inside. .