JPH07253599A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To realize an initially oriented state of uniform monodomains and to improve display characteristics by subjecting one substrate to a uniaxial orientation treatment and providing the other substrate with plural insulating stripe-shaped projectors and not subjecting this substrate to the uniaxial orientation treatment. CONSTITUTION:The glass substrate 11a wired with transparent electrodes 12a and the glass substrate 11b wired with the transparent electrodes 12b formed to a stripe shape are arranged to face each other. The striped transparent electrodes 12a and 12b intersect orthogonally with each other. Chiral smectic phase or preferably lost-spiral chiral smectic liquid crystals 14 is injected between these glass substrates 11a and 11b. The glass substrate 11a is subjected to the uniaxial orientation treatment, such as rubbing treatment, in a direction 13 parallel with the ridge lines 15 of the striped transparent electrodes 12a which are the members having a difference in level from such liquid crystals 14. The substrate 11b on one side is provided with the striped electrodes 12b intersected orthogonally with the electrodes 12a and spacers 21 are arranged over the entire part between the electrodes. The rubbing treatment of the one side substrate 11 may be omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a liquid crystal display device and a liquid crystal display.
The present invention relates to a liquid crystal element such as an optical shutter array, and more particularly, to a liquid crystal element having improved display and drive characteristics by improving the initial alignment state of liquid crystal molecules.

[0002]

2. Description of the Related Art Up to now, a ferroelectric liquid crystal device has been disclosed in US Pat. No. 4,367,924 by Clark et al. In order for the ferroelectric liquid crystal element to exhibit a predetermined driving characteristic, the ferroelectric liquid crystal arranged between the pair of parallel substrates is kept between the two stable states regardless of the electric field application state. It is necessary to be in a molecular arrangement state in which the exchange of γ is effectively performed. For example, in a ferroelectric liquid crystal having a chiral smectic phase, a liquid crystal molecular layer of the chiral smectic phase is perpendicular to the substrate surface, and thus a region (monodomain) in which the liquid crystal molecular axes are aligned substantially parallel to the substrate surface is formed. Need to

As a method for orienting such a chiral smectic liquid crystal, a physical flaw (groove) is formed on the substrate surface in the liquid crystal cell by a rubbing method or an oblique evaporation method, as in the conventional TN type liquid crystal display device. A method has been proposed in which an organic thin film or an inorganic vapor deposition film with a mark is formed to give the orientation of molecules. For example, in the rubbing method, after forming a transparent electrode on a glass substrate, an organic polymer film is formed and rubbed in one direction with a cloth such as velvet, and liquid crystal molecules are aligned by fine scratches on the film surface. It is a thing.

[0004]

The rubbing method is an industrially effective alignment method from the viewpoint of productivity and the like, but a ferroelectric liquid crystal using a liquid crystal cell having a plurality of stripe-shaped transparent electrodes is used. When it is attempted to align the liquid crystal molecules, it is not possible to obtain a sufficient alignment state over a wide area, and a portion (defect) in which the alignment of liquid crystal molecules is disturbed often occurs.

In particular, when the matrix electrodes formed on the substrate are wired at a high density as described below, the electrode wires are relatively thick (for example, 800Å to 30) to reduce the resistance of the electrode wires.
Since the film thickness is 00 Å), a large step of 800 Å or more is formed between the surface of the substrate itself and the electrode surface, and this step causes an alignment defect with respect to the ferroelectric liquid crystal. It became clear by the inventor's experiment.

Therefore, an object of the present invention is to improve display and driving characteristics by realizing a uniform initial alignment state of a monodomain in which the generation of alignment defects is suppressed in a liquid crystal device using a chiral smectic liquid crystal. It is to provide a liquid crystal element.

[0007]

The present invention provides a liquid crystal device having a pair of substrates each provided with an electrode and a chiral smectic liquid crystal disposed between the pair of substrates. The liquid crystal element is characterized in that the substrate is subjected to uniaxial alignment treatment, the other substrate is provided with a plurality of insulating stripe-shaped projections, and the uniaxial alignment treatment is not performed.

Embodiments of the present invention will be described below with reference to the drawings.

[0009]

1 is a perspective view showing an outline of a liquid crystal element of the present invention. The liquid crystal element shown in FIG.
0Å vinegar and transparent electrode 12a (IT
A glass substrate 11a in which an O film and a tin oxide film are wired and a transparent substrate 12b in which a stripe-shaped transparent electrode 12b (ITO film, tin oxide film) is wired are arranged to face each other, and a transparent stripe The electrodes 12a and 12b are orthogonal to each other. These glass substrates 11a and 11b
In between, a chiral smectic phase, preferably a chiral smectic liquid crystal 14 that has disappeared from the helix, is injected. The glass substrate 11a is subjected to a uniaxial orientation process such as a rubbing process on the liquid crystal 14 in a direction 13 parallel to the ridgeline 15 of the stripe-shaped transparent electrode 12a which is a step body.

In a preferred embodiment of the present invention, as the glass substrate 11b which is the substrate on one side, a substrate in which a step body which causes a step with respect to the liquid crystal layer film is eliminated can be used.

FIG. 2 shows the preferred one-sided substrate 11b described above.
3 shows a liquid crystal element using the same. The one side substrate 11b has a stripe transparent electrode 1 orthogonal to the stripe transparent electrode 12a formed on the substrate 11a.
2b is provided, and the spacer member 21 is arranged between the respective electrodes. By disposing such spacers 21 between the electrodes as a whole, it is possible to eliminate the step difference with respect to the liquid crystal layer film caused by the provision of the electrodes. Therefore, in the one-sided substrate 11b, the vertical direction 22 (the substrate 1
Even if a uniaxial alignment axis is formed by rubbing treatment (parallel to the uniaxial alignment axis 13 of 1a), since there is no step difference with respect to the liquid crystal layer film on the substrate 11b, no alignment defect occurs in this portion. Absent.

Further, according to the present invention, the one-sided substrate 11 shown in FIG.
Since it is possible to obtain a good alignment state without necessarily subjecting b to the rubbing treatment, the rubbing treatment applied to the one-sided substrate 11b can be omitted. In addition, as the uniaxial alignment treatment 22 applied to the substrate 11b on one side, the substrate 11b
It is also possible to form the uniaxial orientation treatment axis 22 that intersects the uniaxial orientation treatment axis 13 applied to a at an angle of 90 degrees or less (for example, an angle of 10 degrees to 60 degrees).

In a preferred embodiment of the present invention, various alignment control films (not shown) are provided on the substrate (for example, the substrate 11a) to be subjected to the uniaxial alignment treatment, and the alignment control film is subjected to uniaxial alignment such as rubbing treatment. It can be treated. Examples of the material used for the orientation control film include polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, and cellulose resin. Resins such as melamine resin, urea resin, acrylic resin, or photosensitive polyimide, photosensitive polyamide, cyclized rubber photoresist, phenol novolac photoresist or electron beam photoresist (polymethylmethacrylate, epoxidized-1,4) -Polybutadiene, etc.) and the like, and those formed with a film are preferable.

Further, in producing the liquid crystal element of the present invention, it is necessary to control the distance between the substrates 11a and 11b.
In particular, it is necessary to make the spacing sufficient to eliminate the helical structure of the chiral smectic phase. Substrates 11a and 11b
An appropriate spacer member 21 is disposed between the two, so that the distance can be made uniform over the entire surface. At this time, it is preferable that the substrate 11b is provided with a stripe-shaped spacer member 21 that covers between the stripe-shaped transparent electrodes 12b, as shown in FIGS. Since the film thickness of the spacer member 21 can determine the film thickness of the chiral smectic liquid crystal 14, therefore, it varies depending on the type of liquid crystal material, the required response speed, etc., but generally 0.2 μ to 20 μ. It is preferably set in the range of 0.5 μ to 10 μ. Further, in another embodiment of the present invention, as the spacer member, glass fiber, alumina beads, or the like can be used in addition to the above-mentioned striped spacer.

In the liquid crystal element of the present invention, when an alternating current is applied to the chiral smectic liquid crystal 14 which is orientated in advance under bistability before actual driving, there is no alignment defect and before the application of the alternating current. It is possible to drive the display under an improved contrast. The applied alternating current used at this time is a voltage of 10 to 100 V and a frequency of 10 to 1
Alternating current is applied at 00 Hz for several seconds to several minutes.

As the chiral smectic liquid crystal used in the present invention, various kinds are applied, but liquid crystal having a cholesteric phase at a temperature higher than the chiral smectic phase is particularly suitable. Specifically, the following can be mentioned.

[0017]

[Outer 1] (C phase: crystalline phase, S _C ^* : chiral smectic C phase,
S _A : Smectic A phase, S _B : Smectic B phase, S
_E : smectic E phase, Ch: cholesteric phase, I:
Isotropic phase)

FIG. 4 is a schematic drawing of an example of a cell for explaining the operation of the ferroelectric chiral smectic liquid crystal used in the present invention. 31a and 31b are In ₂ O ₂ , SnO ₂ or IT which forms a step with respect to the liquid crystal layer film.
O (Indium-Tin-Oxide) thin film (8
It is a substrate (glass plate) covered with a transparent electrode composed of 00 Å to 3000 Å), in which the SmC ^* phase (chiral smectic C phase) or SmH ^* (chiral) in which the liquid crystal molecular layer 32 is oriented perpendicular to the glass surface. Liquid crystal of smectic H phase) is enclosed. Line 33 shown in bold
Represents a liquid crystal molecule, and the liquid crystal molecule 33 has a dipole moment (P⊥) 34 in a direction orthogonal to the molecule. When a voltage of a certain threshold value or more is applied between the electrodes on the substrates 31a and 31b, the helical structure of the liquid crystal molecules 33 is unwound, and the dipole moment (P⊥) 34 is entirely oriented in the electric field direction. Can be changed. The liquid crystal molecules 33 have an elongated shape and exhibit refractive index anisotropy in the major axis direction and the minor axis direction thereof. It can be easily understood that the liquid crystal optical modulation element changes its optical characteristics depending on the situation.

The liquid crystal cell preferably used in the liquid crystal element of the present invention has a sufficiently thin thickness (for example, 10 μm or less).
can do. As shown in FIG. 5, as the liquid crystal layer becomes thinner, the helical structure of the liquid crystal molecules unravels even when no electric field is applied, resulting in a non-helical structure.
Its dipole moment Pa or Pb is upward (44
Either a) or downward (44b). As shown in FIG. 5, electric fields Ea or Eb having different polarities, which are equal to or more than a certain threshold value, are applied to such cells as voltage application means 41a and 41b.
, The dipole moment is changed to the upward direction 44a or the downward direction 44b in accordance with the electric field vector of the electric field Ea or Eb, and the liquid crystal molecule is accordingly changed to the first stable state 43a or the second stable state 43a. It is oriented in any one of the states 43b.

As described above, there are two advantages of using such ferroelectricity as a liquid crystal element. The first is
The response speed is extremely fast, and the second is that the alignment of the liquid crystal molecules has bistability. The second point will be further described with reference to FIG. 5, for example. When an electric field E is applied, the liquid crystal molecules are aligned in the first stable state 43a, but this state is stable even when the electric field is cut off. When an electric field Eb in the opposite direction is applied, the liquid crystal molecules are oriented in the second stable state 43b to change the orientation of the molecules, but they remain in this state even when the electric field is turned off. Further, as long as the applied electric field E does not exceed a certain threshold value, the respective alignment states are still maintained. In order to effectively realize such a high response speed and bistability, it is preferable that the cell is as thin as possible.

Example 1 A film having a thickness of 1500Å and a line width of 50 μ has a pitch of 12.5.
ITO stripe electrode pattern (16
(polyimide forming liquid (“PIQ” manufactured by Hitachi Chemical Co., Ltd .; nonvolatile concentration 1
4.5 wt%) was applied to a thickness of 2 μm to form a polyimide film.

Next, a positive type resist solution ("AZ135" manufactured by Shipley Co., Ltd.) is applied on the polyimide film to form a resist layer, and then a mask width of 12 is applied so that the mask is located on the entire surface between the ITO electrodes. Exposure was performed using a stripe-shaped mask having a pitch of 50 μ in the mask portion of 0.5 μ.
Then, the resist film and the polyimide film in the exposed area are removed by developing with a developer "MF312" containing tetramethylammonium hydroxide, and then the resist mask is removed and heat-cured under the curing conditions of the polyimide, and ITO After forming a spacer member having a shape that completely covered between the stripe electrode lines, a rubbing treatment was performed in parallel with the ridge direction of the ITO stripe electrode lines (A electrode plate).

Next, it has a film thickness of 1500Å and a line width of 5
On a glass substrate having an ITO stripe electrode pattern in which 0 μ is formed with a pitch of 12.5 μ, the same P
A 800 Å polyimide film was formed using IQ. Then, the above-mentioned polyimide film was rubbed in a direction parallel to the ridgeline of the ITO stripe electrode line (B electrode plate).

The two electrode plates were laminated so that the ITO stripe patterns were orthogonal to each other and the rubbing directions were parallel to each other, and the periphery was sealed with an epoxy adhesive, and then a chiral smectic phase was introduced from the injection port. The liquid crystal (1) in the isotropic phase shown is injected and slowly cooled (0.5 ° C).
/ Hour) to generate a chiral smectic C phase in the cell.

Observation (photographing) of the thus-prepared ferroelectric liquid crystal element with a polarization microscope under crossed Nicols confirmed formation of monodomain SmC ^* as shown in FIG. In this liquid crystal element, there was no alignment defect even though there was a step formed by the 1500 Å ITO film. In FIG. 6, 51 is a monodomain chiral smectic C phase, 52 is a spacer member formed in a stripe shape, and 53 is a transparent electrode interval.

Comparative Example 1 The same procedure as in Example 1 was carried out except that a B ′ electrode plate was used instead of the B electrode used when the ferroelectric liquid crystal device of Example 1 was prepared. A dielectric liquid crystal element was created. At this time, in the B'electrode plate, the rubbing direction was perpendicular to the longitudinal direction of the ITO stripe pattern, and
It was prepared by the same method as the method for preparing the electrode plate.

When this comparative element was photographed in the same manner as in Example 1, it was as sketched in FIG. That is, as shown in FIG. 7, the alignment mismatching portion 61 which is considered to be based on the alignment defect is seen.

Example 2 An electrode plate was prepared by the same method except that a polyvinyl alcohol film was used instead of the polyimide film used when the B electrode plate of Example 1 was prepared, and the same experiment was repeated. ,
The same result as in Example 1 was obtained.

Example 3 An electrode plate having 1500 Å ITO transparent electrodes formed on the entire glass substrate was prepared, and the PIQ used in Example 1 was 800 Å over the entire surface of the electrode plate. The film thickness is provided. Next, this PIQ film surface was rubbed in one direction by velvet (C electrode plate).

Alumina beads having an average particle size of 1.5 μm were dispersed on the C electrode plate, the B electrode plate was polymerized so that the rubbing directions were parallel to each other, and the periphery thereof was sealed with an epoxy adhesive. After that, the liquid crystal (1) was injected into the cell. When this cell was observed by the same method as in Example 1, no alignment defect was generated.

Comparative Example 2 A cell was prepared in the same manner as in Example 3 except that the B'electrode plate described above was used in place of the B electrode plate used in Example 3, and the cell was prepared in the same manner as in Example 1. As a result of observation by the above method, the alignment misalignment portion which is considered to be based on the alignment defect as shown in FIG. 6 was also generated.

[0032]

According to the present invention, it is possible to provide a ferroelectric chiral smectic liquid crystal device having a good initial alignment state in which alignment defects are not generated, and moreover, prior to the display drive, the applied AC is bistable in advance. By providing the lower ferroelectric chiral smectic liquid crystal, display with improved contrast can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view of a ferroelectric chiral smectic liquid crystal device of the present invention.

FIG. 2 is a sectional view of a one-sided substrate used in the liquid crystal element of the present invention.

FIG. 3 is a cross-sectional view of a liquid crystal element.

FIG. 4 is a perspective view schematically showing an embodiment of a ferroelectric chiral smectic liquid crystal device of the present invention.

FIG. 5 is a perspective view schematically showing an embodiment of a ferroelectric chiral smectic liquid crystal device of the present invention.

FIG. 6 is a sketch drawing of a photomicrograph of the ferroelectric chiral smectic liquid crystal device prepared in Example 1.

FIG. 7 is a sketch drawing of a micrograph of a ferroelectric chiral smectic liquid crystal device prepared in Comparative Example 1.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hisashi Shindo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hirofumi Shibata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (6)

[Claims] 1. A liquid crystal device having a pair of substrates each provided with an electrode and a chiral smectic liquid crystal disposed between the pair of substrates, wherein one of the pair of substrates is uniaxially aligned. A liquid crystal element, wherein a plurality of insulating stripe-shaped projections are provided on the other substrate and are not subjected to uniaxial alignment treatment. 2. The liquid crystal device according to claim 1, wherein the uniaxial alignment treatment is a rubbing treatment. 3. The plurality of insulative st
The liquid crystal element according to claim 1, wherein the stripe projections are arranged at regular intervals. 4. The liquid crystal device according to claim 1, wherein the distance between the pair of substrates is set to be small enough to suppress the formation of a helical structure of chiral smectic liquid crystals. 5. The liquid crystal element according to claim 1, wherein an alignment control film is provided on the substrate on which the uniaxial alignment treatment is performed. 6. The alignment control film comprises polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylelline, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin. The liquid crystal device according to claim 5, wherein the liquid crystal device is formed of a film having at least one substance selected from the group consisting of urea resin and acrylic resin.