JP2537454B2 - Liquid crystal electro-optical device manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal electro-optical device alignment treatment.

[0002]

2. Description of the Related Art Conventionally, liquid crystals have been widely used in various electro-optical application products, and in particular, they have a wide range because they are thin as a display part of portable electric products and have very low power consumption. in use. As a liquid crystal material used for these, a material exhibiting a nematic or cholesteric smectic phase is used, and its display or the like is performed based on the dielectric alignment effect of the material.

In this case, display is carried out by utilizing the phenomenon that the directions of the major axes of the liquid crystal molecules are aligned in one direction on average due to an electric field applied from the outside due to the dielectric anisotropy of the liquid crystal material itself. ing. However, in this case, the time in which the molecular long axis of the liquid crystal material is aligned in one direction by the electric field applied from the outside, that is, the electro-optical response speed is considerably slow, which is on the order of several tens to several hundreds ms.

This can be a very serious drawback, especially when constructing a display device. That is, in the case of a large-area matrix structure, if the number of pixels to be displayed becomes very large, the response speed thereof is slow, and therefore, many devising methods are required for the liquid crystal display driving method. In that case, there are many problems such as inability to display a moving image and crosstalk between pixels.

As one of the solutions to these problems, Clarke (USP4367924) proposes a new display system using a liquid crystal of a smectic phase. A few explanations will be given below.

The smectic liquid crystal has rod-like liquid crystal molecules having a layered structure as shown in FIG. 2, and whether each molecule is perpendicular to the plane of this layer or is inclined at an angle φ. It is in the state of. In each case, the constituent liquid crystal molecules are arranged in parallel with each other.

In this liquid crystal, the light velocity in the direction perpendicular to the molecular layer is higher than the light velocity in the direction parallel to it, and the so-called molecular axis direction has a high light velocity, which shows optically positive birefringence. is there.

Clark et al. Of the optically active chiral smectic liquid crystal among the smectic liquid crystals, C phase, H
We have proposed a new display method using a liquid crystal that exhibits homoferroelectricity.

For example, a ferroelectric liquid crystal showing a chiral smectic C phase as shown in FIG. 2 generally has an electric dipole density,
Has a vector P, and the direction of this vector P is perpendicular to the direction vector N of the long axis of the liquid crystal molecule and parallel to the layer surface of the smectic layer, which is not only in the C phase but also in other phases. It is the same. Due to the presence of electric dipoles in these ferroelectric liquid crystals, these liquid crystals are
The tilting direction of the molecule is changed depending on the direction of the electric field applied from the outside.

That is, when an electric field of + E is applied to the liquid crystal from the outside to the surface of the paper shown in FIG. 2, the inclination is φ, and when an electric field of −E is applied, −φ is applied. The two states of φ and −φ that are inclined at an angle of
The response speed at which liquid crystal molecules change to two states of -φ and φ depending on the direction of the electric field applied from the outside is when the response occurs depending on the presence or absence of an external electric field due to the conventional dielectric anisotropy. Very fast compared to, several to several hundred μs
It was on the order of ec.

In order to display using such two states due to spontaneous polarization, it is necessary to uniformly align the liquid crystal molecules in the uniaxial direction in the entire liquid crystal element.

Further, this chiral smectic liquid crystal is
Since there is a strong interaction between the molecules, when an alignment treatment is applied to the surface of the plate to give an alignment regulating force to the liquid crystal molecules, the effect is exerted not only on the surface of the plate but also on molecules at a distance. It can be said that the orientation of the liquid crystal is greatly affected by the orientation treatment on the substrate surface.

Conventionally, a shearing method, a temperature gradient method, a magnetic field orientation method, a rubbing method and the like have been used as a surface orientation treatment of a substrate which gives a liquid crystal a uniaxial orientation parallel to the substrate. Among these, the rubbing method is widely used because it is easy to industrially obtain a large-area orientation.

[Problems of conventional technology]

However, by this rubbing method,
There is a limit to liquid crystals capable of obtaining uniform alignment in a large area. That is, as a series of phase transitions of the liquid crystal phase, isotropic phase-SmA-S
A liquid crystal having a region showing a smectic A phase on a higher temperature side than a temperature region showing an mC ^* or an isotropic phase -N-SmA-SmC ^* and a chiral smectic C phase is uniform and can perform good uniaxial orientation of a large area. . However, smectic liquid crystals having a phase series other than this series cannot be used in a liquid crystal electro-optical device because sufficient alignment cannot be obtained by this rubbing method and a uniform large area uniaxial alignment state cannot be obtained. It was

On the other hand, even when a liquid crystal having a good orientation is obtained by the rubbing method, the rubbing treatment exerts a very strong uniaxial orientation control force on the liquid crystal from the substrate surface, so that the electric field is actually applied from the outside. When the ferroelectric liquid crystal is inverted by applying the voltage, a difference appears in the inversion process due to the regulation force of the uniaxial orientation.

That is, the case of reversing from + φ to −φ and −
There is a difference in the response speed between the case of reversing from φ to + φ. Further, the liquid crystal molecules are tilted smaller than the original tilt angle φ of the liquid crystal.

Various problems have appeared, and many problems have been desired to be solved for application as a liquid crystal electro-optical device.

[0018]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems found in these conventional rubbing methods and to provide a liquid crystal electro-optical device having good and uniform alignment.

[0019]

In order to solve the above-mentioned problems, according to the present invention, when manufacturing a liquid crystal electro-optical device having a smectic liquid crystal between a pair of substrates, the angle and step of each slope formed on the mold are A plurality of slopes which are equal and whose ridge lines are provided at equal intervals are transferred to the inner surface of at least one of the pair of substrates by pressurizing or pressurizing and heat-treating. The pair of substrates is formed by forming a plurality of slopes on the inner surface.
The smectic liquid crystal injected between the
The layer direction and the ridgeline direction of the slope are approximately aligned
A liquid crystal electro-optical device manufacturing method characterized by be.

According to the present invention, a plurality of regularly arranged slopes having an angle θ with respect to the surface of the substrate are formed by the method described above, and the molecules of the ferroelectric liquid crystal are uniaxially oriented along the direction of the slopes. Is.

The present invention has been found experimentally as a result of diligent efforts by the inventors in order to solve the above conventional problems.

FIGS. 1A and 1B show an example of a schematic view and a sectional view of a substrate used in the liquid crystal electro-optical device according to the present invention.

As shown in FIG. 3A, slopes are formed regularly on the surface of the substrate and are aligned in one direction. Then smectic liquid crystal molecules is parallel to the inclined surface, the ridge line direction of the slope oriented by aligning the direction of the molecular long axis in a direction perpendicular.

In FIG. 1A, for the sake of explanation, it is described that only one molecule is arranged on one inclined surface, but in reality, a plurality of liquid crystal molecules are arranged such that the directions of their long axes are substantially the same. It is oriented.

[0025] At this time Sumekuchi' click solution crystal form, the layer direction of the smectic phase, since the ridge line direction of the slope formed on the substrate to approximately match, it is proposed that a uniform orientation without defects is obtained.

Further, as shown in FIG. 1 (B), the shape of the inclined surface formed on the surface of the substrate is most preferably a sawtooth shape, but substantially the inclined surface formed in one direction is substantially formed on the substrate. It should have been done.

As for this dimension, the angle θ of the slope is 3
° ≦ θ ≦ 15 ° there interval W of ridge line of slope 0.5μm
When ≦ W ≦ 2 μm and the step D on the inclined surface satisfies D ≦ 0.3 μm, a good orientation state was obtained.

That is, the angle θ of the slope is less than 3 ° or 1
If it exceeds 5 ° will not coincide with the vertical ridge line direction of the molecular long axis direction and the slope of the liquid crystal, therefore, the orientation of the liquid crystal is not coincident ridge line direction of the layer direction and the slope of the smectic layer Countless defects occur. In addition, in this case, it was found that the long axes of the liquid crystal molecules were not aligned in one direction in the entire substrate, which was in a non-aligned state.

[0029] Then if the distance W between ridge lines of slope exceeds 0.5μm or less than 2 [mu] m, similarly not function as a liquid crystal electro-optical device not uniaxial orientation can be obtained of the liquid crystal molecules in the entire substrate.

Further, when the step difference D on the slope exceeds 0.3 μm, a large number of defects occur because the degree of unevenness on the substrate surface is severe.

Conversely, if the above-mentioned θ, W, and D are satisfied, it is not necessary to have a sawtooth shape, and the same effect as the present invention can be obtained with any shape.

Examples will be shown below.

[0033]

EXAMPLE First, a glass substrate (1) having a transparent conductive film (2) is used as a substrate, and a silicon oxide film having a function of preventing elution of alkali metal or the like from the glass substrate or the conductive film is formed on the glass substrate (1). Coating solution (RnSi (OH) _4-n ) for coating to a thickness of about 0.5 μm.

[0034] Then the mold was created as the interval W = 1 [mu] m ridge line of slope angle theta = 10 ° slope through the releasing member into contact with said coating to transfer the uneven shape.

Before or during this transfer step, a temperature (for example, 100 ° C.) at which the solvent in the coating film can be evaporated.
It was effective because the unevenness transferred was sharper.

After that, the entire substrate was heated to about 400 ° C. to cure the coating film to complete the coating film (3) having an uneven shape.

In the present embodiment, the uneven shape was transferred from the mold to the silicon oxide film coated on the glass substrate, but other than the silicon oxide film, for example, a polyimide film or a PVA film may be used. Further, the uneven shape may be transferred to the glass substrate itself or the transparent conductive film itself.

[0038] Next, the two substrates which this unevenness formed, the surface unevenness is formed on the inside, parallel ridges lines slope, the outer peripheral superposed as slopes each other is parallel to the seal The liquid crystal container was formed.

Next, a chiral smectic liquid crystal was injected into the container in an isotropic phase state by a conventionally known liquid crystal injection method. The liquid crystal injected at this time did not show a difference in the degree of orientation due to the difference in the molecular structure of the material, but a slight difference in the orientation in the smectic C phase was observed due to the difference in the phase series of the liquid crystal material.

That is, from the phase sequence of isotropic phase-SmA phase-SmC phase, isotropic phase-nematic phase-SmA phase-Sm
It was possible to obtain a uniform alignment over a large area in the smectic C phase without defects in the phase series having the C phase.

The present invention is not limited to the manufacturing method of this embodiment, and it is possible to obtain the same effect as the present invention by using other materials and shapes.

[0042]

INDUSTRIAL APPLICABILITY According to the present invention, in a device that uses a chiral smectic liquid crystal to display by utilizing the liquid crystal electro-optical effect, a uniform alignment state of liquid crystal having a large area and without defects can be easily realized in the smectic C phase. It became possible to do.

Further, as in the conventional rubbing method, the alignment film is scratched and the molecules of the liquid crystal are forcibly arranged in the direction of the scratch, so that the liquid crystal material is inferior to the characteristics possessed by the liquid crystal material itself in displaying. In the present invention, since the liquid crystals are not forcibly arranged, the original characteristics of the liquid crystal material itself can be sufficiently exerted, and particularly the response speed and the contrast ratio are remarkably improved. In addition, since dust generated during rubbing does not occur at all in the structure of the present invention, the production yield of liquid crystal containers is improved.

[Brief description of drawings]

FIG. 1 shows a schematic view and a sectional view of a substrate surface of a liquid crystal electro-optical device of the present invention.

FIG. 2 shows a schematic view of a layer structure of a smectic liquid crystal.

[Explanation of symbols]

Step distance D slopes of the alignment film quadrangular line angle W slopes of the liquid crystal molecules θ ramp with a first substrate 2 transparent conductive film 3 irregularities

Claims (6)

(57) [Claims] 1. When manufacturing a liquid crystal electro-optical device having a smectic liquid crystal between a pair of substrates, the angles and steps of the slopes formed on the mold are equal, and the ridges of the slopes are provided at equal intervals. A plurality of slanted surfaces are transferred to the inner surface of at least one of the pair of substrates by pressurizing or pressurizing and heat-treating to form a plurality of slanting surfaces on the inner surface. The smectic liquid crystal injected between the pair of substrates
Between the layer direction formed by the liquid crystal and the ridgeline direction of the slope.
A method for manufacturing a liquid crystal electro-optical device, characterized in that the liquid crystal electro-optical device is aligned substantially in alignment . 2. The method for manufacturing a liquid crystal electro-optical device according to claim 1, wherein the inner surface of the substrate is the substrate material itself. 3. The method for manufacturing a liquid crystal electro-optical device according to claim 1, wherein the inner surface of the substrate is made of a conductive film material. 4. The method for manufacturing a liquid crystal electro-optical device according to claim 1, wherein the inner surface of the substrate is made of an insulating film material. 5. The method of manufacturing a liquid crystal electro-optical device according to claim 1, wherein the interval between the ridgelines of each of the plurality of slopes is 0.5 μm to 2 μm. 6. The method of manufacturing a liquid crystal electro-optical device according to claim 1, wherein an angle of each of the plurality of slopes is 3 ° to 15 °.