JPH09197420A - Liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a multidomain structure so as to increase the angle of visual field and to decrease contamination or orientation defects in a liquid crystal by forming two pairs of small transparent electrodes perpendicular to each other on a transparent electrode of a substrate, generating electric fields parallel to the substrate and perpendicular to each other by the small transparent electrodes to form domains in the liquid crystal. SOLUTION: This element has electrodes 102, 103 on a transparent electrode film 101 to surround a liquid crystal in a pixel in such a manner that electric fields are generated parallel to the substrate 105 and perpendicular to each other. A nematic liquid crystal having positive anisotropy of the dielectric const. is injected between the substrates. When electric fields parallel to the substrate 105 are generated by the small transparent electrodes 102, 103 formed on the transparent electrode film 101, such liquid crystal domains are formed that the liquid crystal near the substrate surface is aligned along the electric field in each domain. Thereby, the liquid crystal director in the middle of the liquid crystal layer is aligned in various directions, which enables compensation for visual difference due to the double refraction and realizes a display of a wide angle of visual field. Moreover, contamination due to rubbing treatment is not caused.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal device,
In particular, it relates to a wide viewing angle liquid crystal element that does not require an alignment film.

[0002]

2. Description of the Related Art Liquid crystal displays using N (nematic) liquid crystals, such as TN (twisted nematic) type and STN (super twisted nematic) type liquid crystal displays, which are currently mainstream, are used in order to obtain good display. A liquid crystal is sandwiched between polymer alignment films that have been subjected to a rubbing treatment to obtain a monodomain liquid crystal layer.

The rubbing treatment method is inexpensive and simple, but since the surface of the alignment film is directly rubbed with a buff cloth or the like, the surface of the alignment film is often contaminated or scratched, or the element is destroyed by static electricity. Then, these cause a surface defect of the liquid crystal display, which is one of the causes of a decrease in yield.

Further, since the liquid crystal layer forms a mono domain, a difference in birefringence occurs depending on the viewing angle, and contrast and color tone have angle dependence.

With respect to such a problem, for example, Japanese Unexamined Patent Publication No. Hei 7
Japanese Patent Laid-Open No. -1140909 proposes a method of forming polymer steps or walls on the surface of a transparent electrode to form minute domains having random orientation directions in pixels. According to the description of the publication, a liquid crystal panel in which a liquid crystal layer is present between at least a pair of transparent substrates having a transparent electrode on the surface, and the liquid crystal layer is composed of liquid crystal unit cells divided by a step or a wall surface, The liquid crystal molecules are aligned substantially horizontally with respect to the substrate when there is no electric field, and are composed of liquid crystal domains having various orientations (at random orientations), and at least one polarizing plate is provided outside the transparent substrate. It is supposed that the viewing angle is widened without performing the rubbing process and the finer liquid crystal domains are stably present in the fine pixels.

[0006]

As described above, the rubbing method is inexpensive and simple, but since the surface of the alignment film is directly rubbed with a buff cloth or the like, the alignment film surface is contaminated or scratched, or the device is damaged by static electricity. Destruction is often caused. These cause defective display of the liquid crystal display, which is one of the causes of the yield reduction.

Since the liquid crystal layer forms a mono-domain, the liquid crystal director at the middle position of the liquid crystal layer faces in one direction, so that a difference in birefringence occurs depending on the viewing angle, resulting in a difference in contrast and color tone. Dependency comes out.

On the other hand, in the method of multi-domaining by the steps and walls of the polymer proposed in the above-mentioned Japanese Patent Application Laid-Open No. 7-114009, the dielectric constant of the liquid crystal as shown in the polymer dispersion type liquid crystal display. Unless the dielectric constant of the polymer is optimized, good brightness and contrast cannot be obtained, and liquid crystal injection is difficult in manufacturing. When applied to the 90 ° twist TN method, which is the current mainstream display, the cell gap is 1 at the step.
Since the / 4 helical pitch length is not obtained, there is a problem in that the electro-optical characteristics of the entire panel area become uneven, resulting in low brightness and low contrast.

Therefore, the present invention has been made in view of the above problems, and a large number of different electric field regions are formed in a pixel, thereby forming a multi-domain in a liquid crystal layer to realize a wide viewing angle. In addition, it is an object of the present invention to provide a liquid crystal element that reduces contamination due to rubbing treatment and liquid crystal alignment failure by not using a rubbing alignment film.

[0010]

In order to achieve the above object, the present invention provides a liquid crystal device having a liquid crystal phase sandwiched between a transparent substrate having a transparent electrode film on its surface, wherein An electrode formed to surround the liquid crystal inside the pixel so that electric fields that are horizontal and orthogonal to each other are applied to the substrate, and the orientation of the liquid crystal is obtained by the electric field applied to the electrode. A liquid crystal device is provided.

The present invention does not use a polymer thin film that has been rubbed on the transparent electrode on the surface of the substrate to align the liquid crystal molecules, and the minute transparent electrodes that are perpendicular to each other on the transparent electrode on either substrate. Two pairs of electrodes are provided, and liquid crystal domains are formed by electric fields that are horizontal and perpendicular to each other and applied to the substrate by the respective minute transparent electrodes.

[0012]

According to the liquid crystal element of the present invention having the above structure, the nematic liquid crystal having a positive dielectric anisotropy is injected, and the substrate is formed by the minute transparent electrodes formed on the transparent electrodes of the pixels on one of the substrates. When a horizontal voltage is applied to the liquid crystal domain, liquid crystal domains in which liquid crystals near the substrate surface are oriented in respective electric field directions are obtained. As a result, the liquid crystal director in the middle position of the liquid crystal layer is oriented in multiple directions, so that it is possible to compensate for the difference in birefringence due to vision, and a display with a wide viewing angle can be realized.

Further, according to the present invention, since the alignment film is not provided, contamination due to rubbing treatment of the alignment film does not occur.

[0014]

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

FIG. 1 is a plan view (see FIG. 1A) and a cross-sectional view (see FIG. 1B) showing a schematic structure of a liquid crystal element according to an embodiment of the present invention. The liquid crystal element shown in FIG. 1 is a simple matrix driving element having dimensions of about 3 cm × 4 cm.

The sectional structure of the pixel will be described with reference to the sectional view of FIG. An ITO (indium tin oxide) transparent electrode is provided as the pixel transparent electrode 101 on the surface of the substrate 105, and after the insulating film 107 is formed, the second minute electrode 103 is formed on the ITO.
Was patterned as a material.

Further, after performing insulation protection, IT
The first microelectrode 102 is formed using O as a material, and the insulating film 10 is formed.
7'formed. Similarly to the upper substrate 105, the ITO transparent electrode, the insulating film, the first and second minute electrodes, and the like are formed on the lower substrate 104.

Next, the planar structure of the pixel will be described with reference to the plan view of FIG.

The size (dimension) of the lower substrate 104 and the upper substrate 105 is 3 cm × 4 cm, the size (dimension) of the pixel transparent electrode 101 is 100 μm × 300 μm, and the width a of the first microelectrode 102 is 1 μm. The second microelectrode 103 has a size of 1 μm × 3 μm (b = 3 μm, c = 1 μm) and is the first microelectrode.
The distance d between the second microelectrode 103 and the second microelectrode 103 was 1 μm, and the vertical distance between the adjacent second microelectrodes 103 was 5 μm.

A spacer (not shown) of 5.4 μm was sandwiched between the two substrates 104 and 105, the substrates were bonded together with an epoxy adhesive, and a liquid crystal injection port was provided to form a liquid crystal cell.

Liquid crystal was injected into this liquid crystal cell, and the liquid crystal injection port was sealed with an ultraviolet curable resin. The liquid crystal is 5CB (4-cyano-
4'-pentyl biphenyl) was used.

Finally, the polarizing plates 106 and 106 'are attached to the upper and lower substrates 10.
They were attached to 5 and 104 so that the deflection directions were perpendicular to each other. On the lower substrate 104, the deflection direction 108 is set to be parallel to the first microelectrode 102, and on the upper substrate 105, the deflection direction 109 is set to the second direction.
It was arranged to be parallel to the microelectrode 103 of.

The first and second microelectrodes 10 of the above liquid crystal element
When voltage is applied to 2 and 103 so that the potential between adjacent electrodes is 5 V, as shown in FIG. 2, the directors of the liquid crystal surrounded by the minute electrodes have an angle of 90 ° in the adjacent regions. Orientation is approximately 5 μm x 5 μm
Liquid crystal domains having different orientations can be obtained for each region.

FIG. 3 shows the results of measuring the transmittance-driving voltage characteristics when a voltage was applied between the pixel transparent electrodes of this liquid crystal element using the He--Ne laser light of 633 nm. At this time, the transmittance is 1 when no driving voltage is applied.
00%. As shown in FIG. 3, when the voltage between the pixel transparent electrodes of the liquid crystal element is about 1.59 V or less, the transmittance is 90% or more,
Greater than 2.78V and less than 10%.

Further, in FIG. 4, a driving voltage 2 is applied to this liquid crystal element.
The transmittance-viewing angle characteristics of He—Ne laser light in the horizontal direction (see FIG. 4A) and the vertical direction (see FIG. 4B) when V is applied are shown. Good viewing angle characteristics up to 70 ° were obtained in both the horizontal and vertical directions.

[0026]

As described above, the liquid crystal device according to the present invention can obtain a multi-domain of liquid crystal by a horizontal electric field on a substrate and can obtain a wide viewing angle display.

Further, according to the present invention, since the rubbing treatment is not carried out, it is possible to reduce the occurrence of defects in the process such as contamination due to rubbing and uneven alignment of the liquid crystal.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a liquid crystal element according to an embodiment of the present invention, (A) is a diagram schematically showing a planar structure, and (B) is a diagram schematically showing a cross-sectional structure. It is a figure.

FIG. 2 is a diagram schematically showing an alignment direction of liquid crystals of a liquid crystal element according to an embodiment of the present invention.

FIG. 3 shows the transmittance of the liquid crystal device according to the embodiment of the present invention.
It is a figure which shows a drive voltage characteristic.

FIG. 4 is a diagram showing the viewing angle dependence of the transmittance in the horizontal direction and the vertical direction of the liquid crystal element according to the embodiment of the present invention.

[Explanation of symbols]

 101 Pixel transparent electrode 102 First transparent electrode 103 Second transparent electrode 104 Substrate (lower substrate) 105 Substrate (upper substrate) 106, 106 'Polarizing plate 107 Insulating film 108 Polarizing direction of lower substrate 109 Polarizing direction of upper substrate 201 First transparent electrode 202 Second transparent electrode 203 Liquid crystal director 204 Polarization direction of lower substrate 205 Polarization direction of upper substrate

Claims (3)

[Claims] 1. A liquid crystal element having a liquid crystal phase sandwiched between a transparent substrate having a transparent electrode film on the surface thereof, wherein electric fields horizontal to the substrate and perpendicular to each other are applied to the surface of the transparent electrode film. A liquid crystal device comprising an electrode formed so as to surround a liquid crystal inside a pixel, and an orientation of the liquid crystal is obtained by an electric field applied to the electrode. 2. A liquid crystal domain having various orientations by an applied electric field horizontal to the substrate.
The liquid crystal element according to the above. 3. A liquid crystal element having a liquid crystal layer sandwiched between transparent substrates having a transparent electrode on the surface thereof, wherein a first microelectrode is provided on a transparent electrode of any one transparent substrate via an insulating film. And a second microelectrode electrically insulated from the first microelectrode in a direction orthogonal to the first microelectrode, and a predetermined microelectrode is provided between adjacent microelectrodes for each microelectrode. A liquid crystal characterized in that a potential is applied and the directors of the liquid crystal surrounded by the respective microelectrodes are aligned so as to have a predetermined angle in adjacent regions to obtain liquid crystal domains having different alignments. element.