JPS6314124A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To permit a simple orientation treatment without using rubbing by dispersing microregions having at lest >=2 kinds of different liquid crystal orientabilities on the same substrate surface to form one substrate and consisting the shape of at least one kind of the microregions of the uniaxially symmetrical patterns which are the same in the axial direction. CONSTITUTION:The one substrate is formed by dispersing the microregions having >=2 kinds of the different liquid crystal orientabilities on the same substrate surface. The shape of at least one kind of the microregions is constituted of the uniaxially symmetrical patterns which are the same in the axial direction. An under coat 12 consisting of SiO2, a transparent electrode 13, a layer 14 exhibiting the 1st orientation and a layer 15 exhibiting the 2nd orientation are provided on the substrate 11 consisting of glass, plastic, etc. High-polymer films such as polyimide, polyamide, polyester are used for the layer 14 and surface active agents having a fluorocarbon chain, silicate having a hydrocarbon chain, etc., are used for the layer 15. The simple uniaxial orientation treatment is thus obtd. by only the pattern shape of the microregions having >=2 kinds of the different orientabilities to be used without using the rubbing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal device, and particularly to a liquid crystal display or a liquid crystal optical modulator in which a large pretilt angle of liquid crystal molecules can be controlled in a circular manner.

[Prior Art] Conventionally, in a liquid crystal element, the orientation of liquid crystal molecules with respect to a substrate basically includes vertical orientation (homeotropic orientation) and horizontal orientation (homogeneous orientation).

Except for perfect vertical alignment and perfect horizontal alignment, liquid crystal molecules generally form a certain angle with the substrate, which is called a pretilt angle. Furthermore, uniaxial orientation in which the molecular director is projected onto the substrate surface or in a fixed direction is useful for display applications. For typical applications, two factors are controlled: the pretilt angle and the uniaxial orientation.

One of the means for imparting this -axis orientation is through the microscopic physical shape of the surface. A typical method is oblique deposition. The typical material for oblique deposition is S.
'+O is used to obtain a uniaxial orientation with an arbitrary pretilt angle from a homeotropic orientation to a homogeneous orientation depending on the angle of convergence.

As for the orientation based on the shape, there are methods such as mechanical polishing to mechanically form fine grooves in a certain direction, and furthermore, methods of obtaining a gusset ink having periodic irregularities by photo-etching or a replica.

On the other hand, as for chemical treatment, a rubbing method in which a polymer film is formed on the substrate surface and then "rubbed" in a fixed direction with cotton cloth or the like has been widely put into practical use in twisted nematic (TN) displays. This orientation method basically provides homogeneous orientation. On the other hand, homeotropic orientation can be obtained by treating the substrate surface with a surfactant or a silane coupling agent. This is generally called a vertical alignment agent.

Combinations of chemical treatment and rubbing are highly productive and practical, or only provide a rope pretilt angle of less than 5°, or a near-vertical homeotropic alignment using a vertical alignment agent. . Oblique evaporation is used to obtain an intermediate pretilt angle, but it has poor productivity, requires large equipment such as a evaporator, and is not suitable for large-area processing.

In addition, as a conventional display device in which two areas with different alignment abilities are provided on the same substrate surface, a positive dielectric anisotropic liquid crystal with a segment pattern horizontally aligned is used against a vertically aligned display background. What is known as a guest-host LCD display? However, this guest-host liquid crystal display is used as a visible area of different orientations to form a significant pattern.

[Problems to be Solved by the Invention] An object of the present invention is to solve the above-mentioned drawbacks and provide a liquid crystal element in which the pretilt angle of liquid crystal molecules can be controlled.

A further object of the present invention is to provide a liquid crystal element that has high productivity and high reliability and is capable of controlling the tilt and tilt angles. Further, the present invention is intended to be suitably used in a display device that utilizes a relatively large pretilt angle. That is, the purpose is to use a twisted nematic (TN) display with high time division drive, a supertwist birefringence effect (SUE), and a ferroelectric liquid crystal.

Further, the present invention is suitable for large area processing and aims to obtain a large area display using the above.

A further object of the present invention is to provide a liquid crystal element that is subjected to a simple alignment treatment without using rubbing.

[Means for Solving the Problems] In other words, the present invention provides a liquid crystal element in which a liquid crystal is sandwiched between two substrates each having a transparent electrode formed on its surface, in which at least one substrate has at least two substrates on the same substrate surface. This liquid crystal element is formed by dispersing the microregions having different liquid crystal alignment abilities, and is characterized in that the shape of at least one of the microregions is a one-sided symmetrical pattern with the axial direction in the same direction.

The present invention will be explained in detail below.

The liquid crystal element according to the present invention is formed by distributing micro regions having at least two or more different types of liquid crystal alignment layers on the same substrate surface, at least one of the micro regions having a uniaxially symmetrical pattern, and The axial directions of the two are in the same direction.

In the present invention, the two or more different liquid crystal alignment abilities typically include one in which one has homeotropic alignment and the other has homocyanic alignment;
Any material exhibiting the ability to align with any pretilt angle in the range of .degree. can be arbitrarily selected.

The microregions used in the present invention may be within a range that does not form domains due to the orientation treatment, and a preferred example is one of the maximum lines of patterns showing different orientation abilities [distributed arrangement within a range where the opening does not exceed the cell gap]. is used. However, this maximum line width depends on whether the difference in orientation ability between the selected orientation treatments is large or small. If the difference is small, this line width can be made large; conversely, in the case of a combination of almost completely homeotropic and homogeneous alignment materials, the regions of both need to be subdivided.

In the present invention, the shape of the microregions with different orientations is characterized in that the pattern of the microregions with at least one orientation ability is uniaxially symmetrical, and the axes of symmetry are aligned in the same direction. It is something.

The present invention is characterized in that uniaxial alignment of the liquid crystal is achieved by aligning the axial directions. Therefore, it is preferable that the shape of the micro region be relatively simple and easy to design and manufacture. For example, one layer with an alignment film is used as a base, and a pattern designed in advance in a predetermined shape is formed on the surface of the layer using another material having alignment ability.

As mentioned above, the size of this shape is such that the alignment region of one alignment film does not form a clear domain with respect to the other alignment film, and with the cell thickness of a normal TN display, the circular area is preferably about 10 pm. The upper limit is about 6JLm.

On the other hand, there is no particular lower limit; rather, any numerical value range that can be used for processing and production control is sufficient, and values up to about 0.1 μm are effectively used. Even when configuring thin line or mesh patterns, it is desirable that the maximum line width of each line does not exceed 6 to 10 I.

Examples of different alignment films include polymer films used for horizontal alignment treatment, such as polyimide, polyamide, polyester, polycarbonate, polystyrene, polyvinyl chloride, polyvinyl alcohol, and the like. On the other hand, for vertical alignment treatment, surfactants with fluorocarbon chains (Daikin FS 150), silicate esters with fluorocarbon chains (Daikin FS 116), quaternary ammonium salt surfactants (DMOAP), Examples include lecithin and hexadecylamine. Depending on the ground surface condition and the liquid crystal used, inorganic coatings such as Sin□, Tie, 2r203, In2
O, silicon nitride, etc. A fully flexible coating can also be used as a material close to this category.

Next, an example of the alignment treatment forming method used in the present invention will be described.

Transparent substrates are used for ordinary light modulators and displays. In particular, a transparent glass or transparent plastic substrate can be used, and a substrate on which a transparent electrode is formed for the purpose of electro-optical modulation can be used. An undercoat for the purpose of preventing elution of alkali ions and an overcoat for the purpose of protecting the electrodes may be provided on the base side of the transparent electrode of the substrate, if necessary. This is SiO□ and Ai'20:
+Other commonly used transparent insulation materials can be used.

In the most typical configuration used in the present invention, a polymer film exhibiting homocyanic orientation is formed on the surface of the substrate as described above, and then a vertical alignment agent is patterned on this surface in a predetermined shape by printing or photolithography. Examples include things that can be obtained by means.

FIG. 1 is a schematic diagram showing a cross section of a substrate in the present invention showing this configuration. 11 is a substrate made of glass, plastic, etc., and 12 is an undercoat of, for example, SiO□. This may be provided as necessary. Next, a transparent electrode 13 is provided when performing light modulation or display. Although not shown in the figure, an insulating film may be further formed thereon for purposes such as protection.

The above-mentioned electrode substrates 11 to 13 are often used for display and the like. Reference numeral 14 denotes a layer exhibiting the first orientation, that is, an alignment film exhibiting a single run of one orientation according to the present invention, and is a polymer film made of polyimide, porvinyl alcohol, or the like. To form this film, methods such as spinner coating, spraying, dipping, roll coating, and printing can be used. 15 is a second orientation layer, i.e. another orientation material, for example a vertical orientation agent formed by printing, which is similar to the FSISO or FS
116, DMOAP, etc. can be used.

FIG. 2 is a partial plan view of this alignment-treated surface, showing a region ts' exhibiting a second orientation having a streamlined vertical alignment ability and a region 14' exhibiting a first orientation having a horizontal alignment ability. The uniaxial symmetry axis of the streamline shape in FIG. 2 is aligned in the X direction in the figure. The shape of the region 15' exhibiting the second orientation is required to be of a size that does not form a domain that can be distinguished from the surroundings, but the present invention is possible by appropriately selecting the size and distribution density within a certain size. Determine the pretilt angle.

Patterns with uniaxial symmetry are not particularly limited, but for example, Fig. 3 (a), (b), (c)
It is preferable to use a pattern that is relatively simple and easy to design, as shown in FIG. The size forming the independent domain mentioned above is the width ω0 in the figure. ω2. It is required that the width of the minute region indicated by ω3 be smaller than the cell thickness, while f! ,,
! ! 2. A relatively large value is allowed for the length of the minute region indicated by i'.

FIG. 4(a) is an explanatory diagram showing an example of the alignment state of a liquid crystal element according to the present invention. A layer 14 exhibiting a first orientation is a homogeneously oriented surface formed on the substrate, and a homeotropically oriented region partially covering this surface is represented by a layer 15 exhibiting a second orientation. The enlarged plan view showing the planar shape at this time is shown in the fourth figure.
In Figure (b), 16 is a liquid crystal molecule, and indicates which direction the main axis of the liquid crystal molecule is oriented. In the interface region a, the microscopic alignment is dominated by minute regions having different alignment abilities, but it is in the bulk region b that the liquid crystal exhibits optical behavior as a cell. This region has a cell gap d
is sufficiently large compared to the area of the domain-forming portion of the layer 15 exhibiting the second orientation, the difference in orientation ability at the interface no longer resolves within the bulk region. Although the decomposition does not occur, the orientation of the molecules in the bulk region is as if the different pretilt angles at each interface region are averaged, and the interface becomes the first one.
．． The orientation ability of layer 14 showing the orientation and the layer 1 showing the second orientation
The second crystal with an area spread in the axial direction
In the pattern of the layer 15 showing the orientation, the liquid crystal molecules 16 have a pretilt angle as shown by θ in the figure, and by aligning these axial directions, uniaxiality is maintained. Conventionally speaking, this imparting of -axiality corresponds to the deposition direction of rubbing or oblique evaporation, but the present invention has the feature that it can be achieved only by pattern formation.

In the example explained above, a micro region with homeotropic alignment ability was provided on the base exhibiting homogeneous alignment.
They may be formed in a homeotropic manner, or in which a homeotropic orientation is applied to a base and a homogeneous orientation is performed thereon, or in a region where both are separated in advance.

Furthermore, in the present invention, it is also possible to combine two or more types of alignment ability, for example, it is also possible to partially include a material that is not specifically used as an alignment agent. It may be formed by dispersing materials, insulating materials, semiconductor materials, colored materials, etc. as minute regions.

In the present invention, the liquid crystal operation mode to which such alignment treatment can be applied is twisted nematic cell (T
N cells), guest-host cells with or without twist, etc., but it is particularly effective when used in cells using the super-twist birefringence effect and ferroelectric liquid crystals that require a large tilt angle.

[Function] In the liquid crystal element of the present invention, at least one of the substrates is formed by dispersing at least two or more types of microregions having different liquid crystal alignment abilities on the same substrate surface, and the shape of at least one of the microregions is Since the structure consists of a liquid crystal sandwiched between two substrates with a uniaxially symmetric pattern with the same axis direction, the alignment of liquid crystal molecules is controlled by two or more different liquid crystal alignment abilities in the interface region of the substrate surface. However, in the bulk region in the middle, the orientation of liquid crystal molecules is such that the different pretilt angles due to the control of the different microregions are averaged, and each microregion shows a balanced pretilt angle, and the -axis It is presumed that the gender will be preserved.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Vertical 300! Ill, width 300m■, thickness 1.1
1,000 SiO□ films were applied to the blue plate glass surface of m-.
On a substrate on which 300 to 500 transparent conductive films containing 2O as the main component and 300 to 800 polyimide films as a first region are successively laminated, octadecyl ethoxy as a second region is laminated using flexographic printing. Silane 0.5wt%
The isopropyl alcohol solution was prepared in the shape shown in FIG. 3(a), j) 1 m3 pot layer, ω, = 1. Printing was carried out at a design value of 30% of the area ratio to the OIL film and polyimide film. After printing, the substrate was heated at t o ''c for 1 hour to obtain a substrate on which a uniaxially symmetrical pattern was formed.

A liquid crystal cell with a cell gap of 8 μI was prepared using two of the substrates, and liquid crystal agent ROTN manufactured by Hoffmann U. Roche was used.
403 was injected. When the pretilt angle of this cell was measured by a magnetic field potential method, a uniaxially oriented cell of approximately 15° was obtained.

Example 2 Photoresist AZ-1:150J (manufactured by Spree) or 0F was applied to the same polyimide substrate as in Example 1.
A positive type resist such as PR-77 (manufactured by Tokyo Ohka) was applied by spin coating, heated at 80°C for 10 minutes, and then applied as shown in Figure 3 (
In the shape shown in b), β2=5琲1. Exposure using a mask pattern with a design value of ρ = 1.5μ and an area ratio of 25% to the polyimide film, baking, and developing with a prescribed developer.
After dry-smoking, this surface was dip-coated with a 0.5 wt% Tyflon solution of FS-115, and dried at 100°C for 20 minutes.

After this, the photoresist part that was cut off was dissolved and removed using acetone, MEK, etc. together with FS-116, and then
The substrate was heated with 2GO'C for 1 hour and baked to obtain a substrate having a uniaxially symmetrical pattern. When a cell similar to that of Example 1 was produced using this substrate, a uniaxially oriented cell with a pretilt angle of 12'' was obtained.

[Effects of the Invention] As explained above, the liquid crystal element of the present invention has a configuration in which two or more microregions having different alignment abilities are formed in a uniaxially symmetrical shape and formed on a substrate surface with the axis of symmetry in a fixed direction. Therefore, there are the following effects.

A simple uniaxial alignment process that does not require rubbing can be obtained by using only the pattern shape of the micro regions having two or more different alignment abilities. Compared to oblique evaporation, this method uses simple equipment, high-speed processing, and can easily obtain a large area.

A greater effect is that while this is a fast and simple alignment process, it does not require rubbing, so there is no dust adhesion during rubbing and no mechanical contact, making it particularly effective for liquid crystal cells, which are becoming more precise. In other words, 5g which does not like the inclusion of minute dust
This is advantageous for ferroelectric liquid crystal cells having a cell gap of m or less.

In addition, the absence of mechanical rubbing avoids the defect generation process in TPT cells, etc., which have a large number of thin film transistors1.
Is it effective in improving yield?

Moreover, uniaxial orientation can be obtained only by shape design, which is more resistant to external disturbances than rubbing or oblique vapor deposition, and has the effect of being particularly strong against alcohol cleaning after orientation treatment. Furthermore, the pattern shape is not easily affected by the microscopic morphology of the shape, and the quality of the shape and distribution is greater than that of normal pattern formation.

Because it is easy to design and manufacture, it can be used as an application field.
TN, SBE, ferroelectric liquid crystal, guest host cell,
It can be easily applied to TFT liquid crystal cells or other optical modulators.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cross section of the substrate in the present invention, and FIG.
The figure is a partial plan view of the orientation-treated surface of the substrate, FIG. 3(a),
(b) and (c) are explanatory diagrams showing an example of the shape of an alignment pattern having −axis symmetry, and FIGS. 4(a) and (b) are explanatory diagrams showing an example of the alignment state of a liquid crystal element according to the present invention. It is. 11... Substrate 12... Undercoat 13... Transparent electrode 14... Layer showing first orientation 14'... Region showing first orientation 15... Showing second orientation Layer 15'...Regions showing second orientation 16.16', 16''...Liquid crystal molecules a...Interface region b...Bulk region 1'+, !!2.I!,...・Minute region length ω], ω2.ωko...Minute region width d...Cell gap

Claims (1)

[Claims] In a liquid crystal element in which a liquid crystal is sandwiched between two substrates each having a transparent electrode formed on its surface, at least one of the substrates has at least two types of microregions having different liquid crystal alignment abilities dispersed on the same substrate surface. 1. A liquid crystal element, wherein the shape of at least one microregion is formed in a uniaxially symmetrical pattern with the axial directions in the same direction.