JPH05210100A - Manufacture of ferroelectric liquid crystal element - Google Patents

Abstract

PURPOSE:To provide the manufacture of the ferroelectric liquid crystal element which has excellent bistability. CONSTITUTION:In a process of rubbing a couple of upper and lower substrates 11a and 11b provided with stripped electrodes 12a and 12b for multiplexing driving, unevenness in orientation control force due to the difference between the ridge directions of the stripped electrodes 12a and 12b is compensated by unevenness in the extent of the rubbing to manufacture the ferroelectric liquid crystal element while a deviation in the threshold value of switching between two different optical stable states is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal element using a ferroelectric liquid crystal.

[0002]

2. Description of the Related Art A display device of a type in which transmitted light rays are controlled by utilizing a refractive anisotropy of liquid crystal molecules in combination with a polarizing element is a Clark or Lagerwall (La).
Gerwall) (US Patent No. 4)
376934, U.S. Pat. No. 4,690,089, etc.).

This display element is provided with a matrix electrode composed of scanning electrodes and signal electrodes for multiplexing driving of chiral smectic liquid crystal, to which scanning signals are sequentially applied and synchronized with the scanning signals. An information signal is applied to the signal electrode.

The chiral smectic liquid crystal used in this display device generally has a chiral smectic C phase (SmC ^* ) or H phase (SmH ^* ) in a specific temperature range.
And has a property of taking one of the first optical stable state and the second optical stable state in response to an applied electric field in this state and maintaining the state when no electric field is applied. That is, it has bistability and has a quick response to changes in the electric field, and is expected to be widely used for high-speed and memory type display elements.

[0005]

However, at present, it cannot be said that a good bistable device has been obtained. One of the causes of this is a problem in the alignment treatment for aligning the liquid crystal.

When a rubbing process is performed on a pair of upper and lower substrates having stripe-shaped steps (striped electrodes) provided for multiplexing driving, the ridge line direction of the stripe electrodes is the upper and lower substrates. Because of the difference, even if the same rubbing treatment is performed as in the conventional case, the alignment regulating force applied to the upper and lower substrates is different.

As a result, the pretilt angles formed by the liquid crystal molecules at the interfaces of the upper and lower substrates are different, and the first optically stable state and the second optically stable state are no longer in an equivalent relationship.

For this reason, the threshold values (voltage or pulse length) in switching from one optically stable state to the other optically stable state are different from each other, which causes the bistability to be destroyed. It is considered to be.

An object of the present invention was made in view of the above problems of the prior art, and it is an object of the present invention to provide a method of manufacturing a ferroelectric liquid crystal device having good bistability and having no difference in the threshold value. is there.

[0010]

According to the research conducted by the present inventors, as the ridgeline direction of the stripe electrode is changed from parallel to the direction perpendicular to the rubbing direction, a step due to the stripe electrode causes It was found that the frictional resistance with the rubbing cloth increased and the alignment regulating force applied to the substrate weakened. It was also found that when the same rubbing cloth was rubbed multiple times, the alignment regulating force gradually weakened. This is considered to be due to the deterioration of the rubbing cloth.

In view of the above contents, according to the present invention, when rubbing treatment is performed on a pair of upper and lower substrates, the order of the rubbing treatment is determined or the strength of each rubbing treatment is changed. The orientation regulation forces applied to the substrates are made equal, and thus the above-mentioned shift of the threshold value can be prevented.

That is, the present invention firstly manufactures a ferroelectric liquid crystal device comprising a pair of substrates provided with stripe-shaped electrodes for multiplexing driving, and a ferroelectric liquid crystal disposed between the substrates. In the method, during the rubbing treatment of the pair of substrates, the ridge line direction of the stripe electrode is perpendicular to the rubbing direction or the substrate closer to the vertical direction is first rubbed, and then the ridge line direction of the stripe electrode is parallel. Alternatively, it is a method of manufacturing a ferroelectric liquid crystal device, characterized in that the substrate closer to parallel is subjected to a rubbing treatment, preferably, the rubbing treatment of the pair of substrates,
A method for manufacturing a ferroelectric liquid crystal device as described above, which is characterized by being repeatedly performed. Second, a pair of substrates provided with stripe-shaped electrodes for multiplexing driving, and a ferroelectric liquid crystal between the substrates. In the method for manufacturing a ferroelectric liquid crystal element, the substrates are rubbed with different strengths during the rubbing treatment of the pair of substrates.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view schematically showing an example of a liquid crystal element according to the present invention, and FIG. 2 is a sectional view taken along the line AA 'in FIG. As shown in FIG. 2, this liquid crystal element includes a pair of upper substrate 11a and lower substrate 11b arranged in parallel, and a thickness of, for example, about 4 which is wired on each substrate.
It has stripe-shaped transparent electrodes 12a and 12b of 00 to 2,000Å. A ferroelectric liquid crystal, preferably a non-helical ferroelectric smectic liquid crystal 15 having at least two optically stable states is arranged between 11a and 11b.

Further, 14a and 14b are alignment control films, and the alignment control films 14a and 14b and the transparent electrodes 12a and 12 are provided.
insulation 200Å~3,000Å is, for example, a thickness between the b layer _{13a, 13b (SiO 2, TiO} 2, Ta etc. ₂ O ₅ film) may be arranged. The space between the upper and lower substrates 11a and 11b is held by silica beads 16 having an average particle diameter of about 1.5 μm (generally 0.1 to 3.5 μm) dispersed in the ferroelectric smectic liquid crystal 15.

The orientation control films 14a and 14b are subjected to a rubbing treatment for orienting the smectic liquid crystal. In the first aspect of the present invention, the rubbing treatment step for a pair of upper and lower substrates is shown in FIG. As described above, the rubbing process is performed first on the substrate whose ridgeline direction of the stripe electrode is vertical or closer to the vertical with respect to the rubbing direction.
As shown in FIG. 3B, the ridgeline direction of the stripe electrode is
Rubbing is performed on the substrates that are parallel or closer to parallel. More preferably, the rubbing treatment is repeated a plurality of times in the above order.

In the above rubbing treatment method, the strength of the alignment control force caused by the relationship between the rubbing direction and the direction of the step due to the stripe electrode and the strength of the alignment control force due to the deterioration of the rubbing cloth are mutually compensated.

Further, in the second aspect of the present invention, in the rubbing process of a pair of upper and lower substrates, the strength of the alignment regulating force caused by the size of the step due to the stripe electrodes and the relationship between the rubbing direction and the direction of the step due to the stripe electrodes is controlled for each substrate. Is compensated by rubbing with different intensities.

The present invention will be described in detail below with reference to examples and comparative examples.

[0020]

EXAMPLE This example will be described with reference to FIG. 2. First, I was formed on the glass substrates 11a and 11b having a thickness of 1.1 ⁺ mm.
The TO stripe electrodes 12a and 12b were formed. I
The thickness of TO was 2,000Å. Further, as the short-circuit prevention insulator films 13a and 13b of the upper and lower electrodes, SiO
₂ was formed by the sputtering method at 1,000 Å. A polyimide forming liquid was applied thereon, and heated and baked to form polyimide alignment films 14a and 14b.

Next, a pair of upper and lower substrates prepared as described above is rubbed with nylon pile threads. First, one substrate is rubbed in a direction perpendicular to the ridgeline direction of the stripe electrode. Next, the other substrate was rubbed in a direction parallel to the ridgeline direction of the stripe electrode. A total of 10 sets of upper and lower substrates were rubbed by the same method. Next, 1.5 on one of the substrates to be bonded.
Disperse silica beads of μm, print an epoxy resin adhesive sealant on the other substrate, and bond them so that the rubbing directions are parallel (the stripe electrodes are orthogonal to each other on the upper and lower substrates), and 10 sets of panels (Panels No. 1 to 10 were formed in the order of rubbing treatment). A mixed ferroelectric liquid crystal containing phenylpyrimidine as a main component was injected into these panels.

Next, a rectangular wave of 20 V is applied to each panel under crossed Nicols while changing the pulse width, and the threshold value (pulse width) of white → black is measured. Was applied while changing the voltage, and the threshold value of black → white was measured.
The results are shown in Table 1.

[0023]

[Table 1] As described above, no difference was observed in the threshold values of white → black and black → white in all the panels.

[0024]

[Comparative Example] Ten sets of substrates were prepared by the same method as in this example, subjected to rubbing treatment, made into cells by the same method, and liquid crystal was injected. However, in the rubbing process, of the pair of upper and lower substrates, first, one substrate is subjected to rubbing treatment in a direction parallel to the ridgeline direction of the stripe electrode, and then the other substrate is rubbed in the ridgeline direction of the stripe electrode. Rubbing treatment was applied in the vertical direction.

In this order, 10 sets of upper and lower substrates were rubbed and No. The panel was 1'to 10 '. Next, the threshold values (pulse width) of white → black and black → white were measured by the same method as in this example. The results are shown in Table 2.

[0026]

[Table 2] As described above, in any panel, white → black, black →
There was a large difference in the white threshold.

From the above-mentioned Examples and Comparative Examples, it is understood that the threshold deviation largely changes by changing the order of the rubbing process for a pair of upper and lower electrodes having stripe-shaped steps. In the present embodiment using the first rubbing processing method of the present invention, the deviation of the threshold value is eliminated.

Also, when the second rubbing method of the present invention was used, the deviation of the threshold value could be made approximately the same as in this embodiment.

[0029]

As described above, in the method of manufacturing a ferroelectric liquid crystal device, during the rubbing process step, first, the rubbing process is performed on a pair of upper and lower substrates having stripe electrodes. It is possible to equalize the alignment regulating force applied to each substrate by setting the value or, secondly, changing the strength of the rubbing process.

That is, in the first method, it is possible to compensate the strength of the alignment control force caused by the relationship between the rubbing direction and the direction of the step due to the stripe electrode and the strength of the alignment control force due to the deterioration of the rubbing cloth. In the method of
It was possible to compensate the strength of the alignment control force generated by the size of the step due to the stripe electrode and the relationship between the rubbing direction and the direction of the step due to the stripe electrode by rubbing each substrate with different strengths.

In this way, by making the alignment regulating forces of the upper and lower substrates equal, there is no shift in the threshold value during switching between two different optically stable states, and a ferroelectric liquid crystal of good bistability. It becomes an element.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing an example of a liquid crystal element according to the present invention.

FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.

FIG. 3 is a schematic diagram showing a relationship between a rubbing direction and a stripe electrode substrate in the present invention.

[Explanation of symbols]

 11a, 11b Upper and lower substrates 12a, 12b Striped electrodes 13a, 13b Insulating films 14a, 14b Alignment control film 15 Ferroelectric smectic liquid crystal 16 Silica beads

Claims (3)

[Claims] 1. A method of manufacturing a ferroelectric liquid crystal device, comprising: a pair of substrates provided with stripe electrodes for multiplexing driving; and a ferroelectric liquid crystal disposed between the substrates. When rubbing the substrate, the ridgeline direction of the striped electrode is perpendicular to the rubbing direction, or the substrate closer to the vertical is rubbed first, and then the ridgeline direction of the striped electrode is parallel or parallel. A method of manufacturing a ferroelectric liquid crystal device, characterized by subjecting a substrate closer to the substrate to a rubbing treatment. 2. The method of manufacturing a ferroelectric liquid crystal device according to claim 1, wherein the rubbing treatment of the pair of substrates is repeated. 3. A method of manufacturing a ferroelectric liquid crystal device, comprising: a pair of substrates provided with stripe-shaped electrodes for multiplexing driving; and a ferroelectric liquid crystal disposed between the substrates. A method of manufacturing a ferroelectric liquid crystal device, wherein each substrate is rubbed with different strength during a rubbing treatment of the substrate.