JPH04127126A - Ferroelectric liquid crystal device - Google Patents

Abstract

PURPOSE:To make a display with a sufficiently high contrast or perform optical switching by providing projecting surfaces on a surface contacting liquid crystal at equal intervals in the layer direction and layer normal direction of ferroelectric liquid crystal. CONSTITUTION:This device has substrates 1, electrodes 2, orienting layers 3, a sealing material 4 for holding the liquid crystal in a device, a gap holding material 5 for holding the transparent substrates at a constant interval, the projection parts 6, and the ferroelectric liquid crystal 7. On the surface contacting the liquid crystal,the projection parts 6 are provided at the equal intervals in the layer direction and layer normal direction of the ferroelectric liquid crystal 7. The ferroelectric liquid crystal 7 is a liquid crystal compound or liquid crystal composition which polarizes itself and can be inverted in polarizing direction with an external electric field and the projection parts are single- body projections or sets of close projections. Consequently, the ferroelectric liquid crystal 7 is oriented uniformly and stably in a specific orienting direction to make the high-contrast display or perform the optical switching.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal device using ferroelectric liquid crystal.

[Conventional technology]

In the field of liquid crystal display devices, it has been proposed to use ferroelectric liquid crystals that have high-speed response. As this ferroelectric liquid crystal, it is being considered to use one exhibiting a chiral smectic C phase or the like.

However, due to the characteristics of ferroelectric liquid crystals, it is difficult to align liquid crystal molecules uniformly in a predetermined alignment direction. Therefore, when conventional alignment means are applied to align ferroelectric liquid crystals, uniform alignment cannot be achieved. The problem is that it is difficult to do so. Conventional alignment methods include forming an alignment film on the inner surface of the substrate of a liquid crystal device, magnetic field alignment method (heating the liquid crystal and applying a magnetic field from the outside), and electric field alignment method (heating the liquid crystal and applying a magnetic field from the outside). and a shear force orientation method (a method in which a pair of substrates used in a liquid crystal device are shifted in opposite directions to apply shear force to the liquid crystal).

[Problem to be solved by the invention]

No matter which of the above alignment means is applied, it is difficult to uniformly and stably align the liquid crystal molecules of the ferroelectric liquid crystal in a predetermined alignment direction. In particular, the occurrence of zigzag defects in the ferroelectric liquid crystal layer could not be prevented. Therefore, conventional liquid crystal devices using ferroelectric liquid crystals have a problem in that display or optical switching cannot be performed with sufficiently high contrast.

[Means to solve the problem]

The present invention was made based on the above circumstances, and was developed as a result of intensive research with the aim of providing a liquid crystal device using ferroelectric liquid crystal that can perform display or optical switching with sufficiently high contrast. The ferroelectric liquid crystal device of the invention has been completed.

That is, the present invention comprises a ferroelectric liquid crystal layer, an electrode provided to sandwich the liquid crystal layer and enable voltage application to the side in contact with the liquid crystal layer, and a substrate provided with an alignment layer on the electrode surface. This is a ferroelectric liquid crystal device characterized in that protrusions are provided on the surface in contact with the liquid crystal at equal intervals in the layer direction and layer normal direction of the ferroelectric liquid crystal.

One embodiment of the liquid crystal device of the present invention is shown in FIG.

In FIG. 1, l is a substrate, 2 is an electrode, 3 is an alignment layer, and 4
5 is a sealing material for holding the liquid crystal in the device, 5 is a gap holding material for maintaining a constant distance between the transparent substrates, 6 is a stepped portion, and 7 is a ferroelectric liquid crystal. Hereinafter, the explanation will be given along with FIG.

Examples of the transparent substrate l include glass and plastic, but are not particularly limited thereto.

The electrode 2 may be formed by forming a film of a transparent conductor such as ITO on a transparent substrate, but is not particularly limited thereto.

The ferroelectric liquid crystal 7 is a liquid crystal compound or liquid crystal composition that has spontaneous polarization and whose direction can be reversed by an external electric field, and the liquid crystal compound is 4-decyloxybenzylidene-
4-Amino-2-methylbutylcinnamate (DOBA
MBC), 4-hexyloxybenzylidene-4-amino-2-chloropropylcinnamate (HOBACPC)
) etc. When a liquid crystal compound is used alone, there are problems such as a narrow temperature range in which it exhibits ferroelectricity, high viscosity, and short pitch length. Therefore, the ferroelectric liquid crystal is
It is preferable to use a liquid crystal composition in which two or more species are mixed or a smectic liquid crystal or a chiral nematic liquid crystal is mixed.

As the material for the alignment layer 3, materials conventionally used for alignment of ferroelectric liquid crystals can be used. Examples include inorganic substances such as SiO, and organic substances such as polyimide, polyamide, polyvinyl alcohol, and organic silane compounds.
It is not limited to this.

Examples of the shape of the protrusion 6 of the present invention viewed from a direction perpendicular to the transparent substrate are shown in FIGS. 2 to 5. The protrusion of the present invention is
Refers to a single protrusion or multiple protrusions in close proximity.

Figures 2 to 4 show a protrusion consisting of a single protrusion;
The figure shows a protrusion consisting of a set of four protrusions.

Examples of the arrangement of the protrusions are shown in FIGS. 6-8. A square in FIGS. 6 to 8 indicates one protrusion. In Figure 8, for example, the straight line connecting a and b is the layer direction of the ferroelectric liquid crystal, and b and C
Assuming that the straight line connecting them is in the layer normal direction, in this case, the distance between the protrusions in the layer direction means the distance between a and b, and the distance in the layer normal direction means the distance between b and C. means.

The size and shape of the protrusion are not particularly limited, but 0.01
~400 square μ sheath, and the length ratio between the layer direction of the ferroelectric liquid crystal and the layer normal direction is 1:10 to 10:1 when the protrusion is viewed from a direction perpendicular to the transparent substrate. is preferable from the viewpoint of effectiveness. In this case, the size and shape of the protrusion mean the size and shape of the smallest convex closed curve that includes all of the protrusion inside.

When the liquid crystal device of the present invention is applied to display, the difference in the thickness of the liquid crystal layer between the protrusions and the non-protrusions causes a difference in display density and display color tone, so an optical mask is used to cover the protrusions. Preferably, the means prevents the light passing through the protrusion from being observed externally. Therefore, when the liquid crystal device of the present invention is particularly applied to display,
It is preferable to appropriately design the relationship between the total area of the protrusion and the area of the liquid crystal device involved in display so that sufficient light can pass through the liquid crystal device. Although the ratio of the protrusions to the total area of the device does not essentially affect the effect of the present invention, from the above point of view, when the liquid crystal device of the present invention is applied to displays in particular, the area of the protrusions is 50 for the total area of
% or less, more preferably 20% or less, most preferably 10% or less.

The number of protrusions is 5 to 500 in the normal direction of the ferroelectric liquid crystal layer.
The effects of the present invention can be obtained if the layers are provided at ptn intervals of 5 to 1000 μm in the layer direction. This interval is more preferably 10 to 200 pm in both the layer normal direction and the layer direction from the viewpoint of the effects of the present invention. Furthermore, when the liquid crystal device of the present invention is particularly applied to display, the above-mentioned consideration is required, and the spacing between the protrusions is adjusted so that the relationship between the total area of the protrusions and the area of the liquid crystal device involved in display is appropriate. It is preferable to design

The height of the protruding portion from the surface of the alignment layer is 0.00 mm of the cell gap.
If the content is in the range of 5 to 100%, the present invention will have significant effects. However, the cell gap is the thickness of the liquid crystal layer in the liquid crystal device. When the height of the protrusion is equal to the cell gap, the protrusion may also serve as a gap retainer for keeping the cell gap constant over the entire liquid crystal device.

To form a protrusion on the surface in contact with the liquid crystal, there are a method of forming the substrate, an electrode, or an alignment layer into a protrusion shape, and a method of forming the protrusion on the electrode or the alignment layer using another material.

As means for providing the protrusions of the present invention on the electrode or alignment layer, there may be used a substance that causes a chemical reaction with energy rays such as ultraviolet rays, electron beams, or chi-rays, lithography means, or mechanical compression means using a metal stamper. Can be mentioned. Photolithography is preferred from the viewpoint of ease of formation and processing accuracy.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 40mm x 3 with 0.07μm of indium tin oxide deposited
Photosensitive polyimide precursor (manufactured by Asahi Kasei Corporation, product name: PIMELTMG) on a glass plate of 7.5 mm and thickness IM
-503C) was spin-coated and then dried at 70°C for 30 minutes. This was exposed to light for 10 seconds using an ultra-high-pressure mercury lamp through the mask shown in Figure 9, developed, and heated in air at 180°C for 2 hours. A protrusion of ×10DI11 was created.

A silane coupling material was spin-coated on both this glass plate (1) and a glass plate (2) of the same size on the side on which indium tin oxide was vapor-deposited, and then baked in air at 150°C for 5 minutes. The glass plates (1) and (2) were rubbed with a polyester cloth (referred to as rubbing treatment) to align the ferroelectric liquid crystal. At this time, the relationship between the rubbing direction of the glass plate (2) and the arrangement of the protrusion patterns is shown in FIG. 1O. The glass plates 1 and 2 were stacked facing each other so that the rubbing directions were opposite to each other, and the periphery was sealed with epoxy adhesive, leaving a portion for liquid crystal injection. Ferroelectric liquid crystal mixture [manufactured by Chisso ■, product name:
A ferroelectric liquid crystal cell was created by injecting C5-1024:l and cooling it to room temperature at a rate of 1"C per minute. When this cell was observed with a polarizing microscope, a -like liquid crystal alignment with no zigzag defects was obtained. This cell was placed between two polarizers arranged in orthogonal Nicols, and the 11th
When a pulse voltage having the waveform shown in the figure was applied and the transmitted light intensity of helium-neon laser light (632.8 nm) was observed, the result was as shown in FIG. 12. As a result, the light intensity ratio (contrast) between the light transmitting state and the light blocking state of this cell was 80.

Example 2 A ferroelectric liquid crystal cell was produced in the same manner as in Example 1, but polyvinyl alcohol was used instead of the silane coupling material as the material for the alignment film. Both the glass plate (2) with projections and the glass plate (2) without projections were rubbed with polyester cloth to align the ferroelectric liquid crystal. The glass plate ■ was rubbed as shown in Figure 10. The glass plates (■) and (2) were stacked facing each other so that the rubbing directions were the same, and the periphery was sealed with an epoxy adhesive, leaving a portion for liquid crystal injection. Ferroelectric liquid crystal mixture [manufactured by Chisso ■, product name: c] at a temperature of 100°C from the injection port
s-10243 was injected and cooled to room temperature at 1°C per minute to create a ferroelectric liquid crystal cell. When this cell was observed with a polarizing microscope, it was found that a -like liquid crystal alignment with no zigzag defects was obtained. This cell was placed between two polarizers arranged in orthogonal Nicols, and a pulse voltage of the waveform shown in Fig. 11 was applied to observe the transmitted light intensity of helium-neon laser light (632,8 nm). As a result, the contrast of this cell was 70.

Example 3 5 parts by weight of polyvinyl alcohol, 7.5 parts by weight of acrylate having a structure represented by the following structural formula (1), and 0.15 parts by weight of benzyl dimethyl ketal were mixed with 100 parts by weight of N,N-dimethylformamide. It was dissolved in a mixed solvent with 100 parts by weight of water.

This solution was spin-coated onto a glass plate (2) on which indium tin oxide had been vapor-deposited, and then allowed to stand in an oven at 70°C for 30 minutes to dry, yielding a coating film with a thickness of 2.2 μm.

It was exposed for 60 seconds to an ultra-high pressure mercury lamp through the mask shown in FIG. This sample was then placed in an oven at 180°C for 1 hour.
When the film was allowed to stand for a while, the film thickness in the unexposed area became 1.48 μm. When the surface shape of the sample was measured using a stylus type surface roughness measuring device, the exposed area was raised from the unexposed surface.
The height of the exposed area from the unexposed surface was 1.00 μ-. This glass plate ■ is rubbed as shown in Figure 10, and a glass plate with an indium tin oxide film ■ coated with polyvinyl alcohol by rotation is rubbed in the same direction and overlapped, leaving the liquid crystal injection port and surrounding it with epoxy adhesive. It was sealed with.

A ferroelectric liquid crystal mixture (manufactured by Chisso ■, trade name: CS-1018) was injected at a temperature of 90°C from the inlet, and the flow rate was 1 min.
A ferroelectric liquid crystal cell was prepared by cooling the cell at ℃ to room temperature. When this cell was observed with a polarizing microscope, it was found that a -like liquid crystal alignment with no zigzag defects was obtained. This cell was placed between two polarizers arranged in orthogonal Nicols, and a pulse voltage of the waveform shown in Fig. 11 was applied to observe the transmitted light intensity of helium-neon laser light (632,8 nm). As a result, it was found that the contrast of this cell was 40.

Comparative Example 1 40 mm with 0.07 μm of indium tin oxide deposited
Polyvinyl alcohol was spin-coated on glass plates (1) and (2), each measuring 37.5 mm x 37.5 mm and 1 m thick, and then dried at 70°C for 30 minutes. The glass plates (■) and (■) were rubbed with a polyester cloth to align the ferroelectric liquid crystal.

After spraying glass beads with a diameter of 2.0μ on the glass plate ■, stack the glass plates ■ and glass plates ■ facing each other so that the rubbing direction is the same, and use a part for liquid crystal injection. The surrounding area was sealed with epoxy adhesive.

Ferroelectric liquid crystal mixture [
A ferroelectric liquid crystal cell was prepared by injecting CS-10181 manufactured by Chisso ■ and cooling it to room temperature at 1°C per minute. When this cell was observed using a polarizing microscope, many zigzag defects were observed. This cell was placed between two polarizers arranged in orthogonal Nicols, and a pulse voltage having the waveform shown in FIG. 11 was applied to helium-neon laser light (632
, 8n+11), it was found that the contrast of this cell was 10.

〔Effect of the invention〕

The liquid crystal device of the present invention uniformly and stably aligns ferroelectric liquid crystal in a predetermined orientation direction, and can perform display or optical switching with high contrast.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the liquid crystal device of the present invention. 1 is a transparent substrate, 2 is a transparent conductive film, 3 is an alignment layer, 4 is a sealing material, 5 is a cell gap maintaining material, 6 is a projection, and 7 is a liquid crystal layer. 2.3.4 and 5 are plan views showing examples of the shape of the protrusion, and FIG. 5 is a plan view of an example in which the protrusion is formed by a set of protrusions. 6.7 and 8 are plan views showing examples of the arrangement of protrusions. The rectangle in the figure indicates the protrusion, and the 2.3.
This shows that protrusions as shown in Figures 4 and 5 are formed. FIG. 9 shows a photomask, and numeral 8 indicates a portion through which light passes. FIG. 10 shows the rubbing direction of the alignment film provided with protrusions. FIG. 11 shows the waveform of the voltage applied to the ferroelectric liquid crystal cell. FIG. 12 shows the waveform of the voltage applied to the ferroelectric liquid crystal cell and the optical response of the cell due to the voltage.

Claims (1)

[Claims] a ferroelectric liquid crystal layer, an electrode provided to sandwich the liquid crystal layer and to enable voltage application to the side in contact with the liquid crystal layer;
A ferroelectric liquid crystal device comprising a substrate provided with an alignment layer on an electrode surface, characterized in that protrusions are provided on the surface in contact with the liquid crystal at equal intervals in the layer direction and layer normal direction of the ferroelectric liquid crystal. Device.