JPH07199168A - Liquid crystal optical element - Google Patents

Abstract

PURPOSE:To provide a liquid crystal optical element which is easily and precisely controllable in electro-optic characteristics, such as transmission and scattering, and is free from defects, such as air bubbles, within a driving plate. CONSTITUTION:This liquid crystal optical element is formed by holding a liquid crystal material between two sheets of substrates with electrode layers and at l.east one substrate thereof have projections 4 which scatter orientation of the liquid crystal. These projections 4 exist on the liquid crystal material 3 side of the substrates 1 and the directors of the liquid crystal material 3 are scattered by the three-dimensional hindrances of the projections 4, by which a scattered state is obtd. when voltage is not impressed to the element. The directors of the liquid crystal material 3 are unified in one direction by an electric field and, therefore, a transparent state is obtd. when the voltage is impressed to the element. The liquid crystal optical element of a guest-host type is obtainable as well by dispersing dichromatic dyestuff materials into the liquid crystal material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal for controlling transmission / scattering of light by an electric field, which is used for a display device for displaying characters, figures and the like, a light control glass for adjusting the amount of incident light, an optical shutter and the like. Regarding optical elements.

[0002]

2. Description of the Related Art Conventionally, liquid crystal display elements of TN type or STN type using nematic liquid crystal have been put into practical use. In recent years, ferroelectric liquid crystals and anti-ferroelectric liquid crystals have been developed. However, since these liquid crystal optical elements require a polarizing plate, they have the drawback of being limited in brightness and contrast.

The method of dispersing the encapsulated liquid crystal material disclosed in Japanese Patent Publication No. 58-501631 in a polymer resin has the advantage of high light utilization efficiency because no polarizing plate is required. There is. In this polymer-dispersed liquid crystal element, by utilizing the fact that the refractive index of the liquid crystal material in the capsule changes depending on the presence or absence of an electric field, the refractive index of the capsule material is set equal to that of the liquid crystal material under voltage application. An optical element is obtained which becomes transparent when a voltage is applied and becomes opaque by scattering light when the voltage is removed. Here, polyvinyl alcohol, gelatin and the like have been proposed as the polymer substance. However, since these are manufactured by spin-coating a polymer-dispersed liquid crystal film on one substrate and then adhering the counter substrate, a large amount of liquid crystal material is required, and it is difficult to control the film thickness. There is a manufacturing defect. Further, since it is difficult to precisely control the particle size and particle size distribution of the encapsulated liquid crystal material, there is a drawback that the transmission and scattering characteristics cannot be freely controlled.

As a similar device utilizing the difference in refractive index between a polymer material and a liquid crystal material, one in which a liquid crystal material is dispersed in an ultraviolet curable compound is known. JP-A-63-2712
According to the technique disclosed in Japanese Patent No. 33, a polymer-dispersed liquid crystal device is obtained by injecting a uniform solution of a liquid crystal material and an ultraviolet curable compound between substrates having a defined gap, and then curing the ultraviolet curable compound by ultraviolet irradiation. Further, it has an advantage that the film thickness can be easily controlled and the area can be increased.
However, in this disclosed technique, there remains a problem in reliability of device characteristics due to deterioration of the liquid crystal material due to irradiation of ultraviolet rays at the time of manufacturing, remaining of an uncured ultraviolet curable compound, and the like. Furthermore, the UV-curable compound that constitutes this polymer-dispersed liquid crystal element has a low boiling point in the precursor state before UV-curing, and will evaporate when injected between substrates under reduced pressure. Therefore, the composition ratio of the liquid crystal material and the ultraviolet curable compound changes, and the characteristics deteriorate. Further, in the disclosed technique, the injection is limited to normal pressure, but the injection under normal pressure has a drawback that air bubbles cannot be avoided.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and an object of the present invention is to provide a liquid crystal optical element capable of freely and highly controlling transmission / scattering or transmission / absorption characteristics. It is to be. Further, an object of the present invention is to provide an element which can be manufactured by a simple means of injecting a liquid crystal material into an empty panel having a fixed gap under reduced pressure.

[0006]

SUMMARY OF THE INVENTION The present invention is a liquid crystal optical element in which a liquid crystal material is sandwiched between two substrates with electrode layers, at least one of the substrates having a projection. Regarding

The present invention is a transmission-scattering or transmission-absorption type liquid crystal optical element characterized in that the light control section of the substrate has a projection that disturbs the alignment of the liquid crystal.
A technique relating to a phase grating disclosed in Japanese Patent No. 41133, etc., Japanese Patent Laid-Open No. 5-107527 and Japanese Patent Laid-Open No. 5-232.
What is different from the technique relating to the partition wall of the pixel disclosed in Japanese Patent No. 452 etc. will be described below.

As the liquid crystal material used in the present invention, nematic liquid crystal and smectic liquid crystal can be used. Also,
A chiral nematic liquid crystal may be used to increase light scattering, or a dual frequency drive liquid crystal whose sign of Δε changes depending on the applied frequency may be used. A guest-host type in which a dichroic dye is mixed is also possible.

At least one of the two substrates with electrode layers used in the present invention may be one having transparency such as glass or plastic, and the other substrate also serves as a light reflecting plate or a light absorbing plate. It doesn't matter what you have. Also,
The surface of the substrate that is in contact with the liquid crystal material may be subjected to the same alignment treatment as that of the surface of the protrusion, or may be subjected to an alignment treatment different from the protrusion.

As the electrode layer, a highly transparent material such as ITO (indium-tin-oxide) can be used, but when the light reflecting material or the light absorbing material has conductivity, these are used as the electrode. You can also do it. In this case, the electrode layer is placed in close contact with the light control layer.

When a light reflecting plate is used, the light reflecting plate may be an inorganic material or an organic material as long as it is made of a material that reflects light. Further, the reflection intensity or the reflection wavelength can be arbitrarily changed according to the intended element characteristics. The structure may be such that the light reflecting material forms the entire light reflecting plate, or the light reflecting material may be coated on a substrate made of another material.

When the light absorbing plate is used, the light absorbing plate may be an inorganic material or an organic material as long as it is made of a material that absorbs light. The absorption intensity or the absorption wavelength can be arbitrarily changed according to the intended device characteristics. The structure may be such that the light absorbing material forms the entire light absorbing plate,
The light absorbing material may be coated on a substrate made of another material.

Spacers used in ordinary liquid crystal devices can be used to set the distance between the substrates,
The protrusion itself can also be used. The interval is 3μ
It is preferably about m to 50 μm.

When the liquid crystal optical element of the present invention is used as a display, not only black and white display but also color display using a color filter is possible.

As a method of driving the liquid crystal optical element of the present invention, an active matrix method using a control element such as TFT or MIM can be used in addition to the simple matrix method.

In the liquid crystal optical element of the present invention, the protrusion is located on the side of the substrate which is in contact with the liquid crystal material, and is also located on the light control section of the substrate. When no voltage is applied, the director of the liquid crystal material is disturbed by the steric hindrance of the projections, and as a result, a scattering state is obtained. When a voltage is applied, the director of the liquid crystal material is aligned in one direction by the electric field, and thus a transparent state is obtained. In the present invention, at least one of the substrates needs to have a protrusion, but two substrates may have a protrusion. At this time, the protrusions on the two substrates may be connected.
Further, the number, density, position, regularity, and irregularity of the protrusions are not particularly limited as long as they are determined so that the orientation of the director of the liquid crystal is disturbed. Further, there is no problem if the protrusion is not only in the light transmitting portion of the substrate or the driving portion of the liquid crystal material, but also in the portion where light is not transmitted or the portion where the liquid crystal material is not driven.

The shape and surface irregularities of the protrusions of the present invention can be selected arbitrarily as long as they can disturb the alignment of the liquid crystal material. As the shape, for example, a conical shape, a cylindrical shape, a cube,
There are rectangular parallelepiped, quadrangular pyramid, triangular pyramid, etc., but not limited to this.
Further, from the viewpoint of disturbing the alignment of the liquid crystal, it is preferable to use a protrusion having unevenness on the side surface, and this unevenness does not necessarily have to be periodic.

The protrusion does not necessarily have to be positioned perpendicular to the substrate, but may be tilted. The height of the protrusion is not particularly limited, and may be the same as the gap of the substrate or may be less than that. Also, the height does not have to be uniform. Although the diameter of the protrusion is not limited, it is preferably equal to or smaller than the gap of the substrate.

The material of the protrusion may be an inorganic material or an organic material, and the refractive index does not necessarily need to match the ordinary or extraordinary refractive index of the liquid crystal material. Further, it does not necessarily have to be optically transparent, and may be an insulator or a conductor. Furthermore, the protrusions may be formed of a one-component compound, and may be a composite or a layered product for the purpose of improving strength, adhesion to a substrate, and the like.

As the method of forming the protrusions, various methods such as a printing method, a vapor deposition method, a sputter method, and a molecular beam epitaxial (MBE) method can be used, but a resist method is particularly preferable. As the resist method, the dry etching resistance of the resist material may be used to process another material such as glass to form the protrusions, or the processed resist material itself may be used as the protrusions. As the resist material, any of a photoresist material, a deep UV resist material, an electron beam resist material and the like can be used, and it may be a negative type or a positive type.

As the resist material, commercially available products can be used. For example, negative photoresists include polymethylisopropenyl ketone + bisazide, polyvinylphenol + bisazide, and the like, and negative photoresists include polychlorostyrene and poly (4).
-Acetoxymethylstyrene-co-vinylphenol) + onium salt and the like are used as negative electron beam resists such as polyglycidyl methacrylate and poly (diallyl-
o-phthalate), poly (2,3-dichloropropyl acrylate), etc.
-Quinonediazide + novolak, positive-type deep resist, polymethylmethacrylate, polymethylisopropenylketone, poly-t-butylisopropenylketone, etc., positive-type electron beam resist, poly (hexafluorobutylacrylate), Examples include poly (ethyl α-cyanoacrylate) and poly (α-methylstyrene).

The light control section of the present invention refers to a portion of the substrate that contributes to optical characteristics such as transmission and scattering and transmission and absorption, and more specifically, refers to an electrode portion to which an electric field is applied to the liquid crystal material.
For example, there is a transparent electrode portion such as ITO. In addition, the light shielding portion such as the black matrix used in the TFT is different from the light control portion.

In the present invention, a liquid crystal optical element having excellent scattering characteristics and improved contrast can be obtained by subjecting the projections to an alignment treatment, and the type of the aligning agent is arbitrarily selected in consideration of the characteristics of the elements. it can. The orientation direction can be arbitrarily selected depending on the dielectric anisotropy of the liquid crystal material used, the shape of the protrusions, or the like. Treatment processes include solution coating, plasma polymerization, sputtering and the like. The aligning agent is roughly classified into a vertical aligning agent and a horizontal aligning agent. For example, as the vertical alignment agent, lecithin, stearic acid, hexadecyltrimethylammonium bromide, octadecylamine hydrochloride, chromium myristate complex, chromium perfluorononanoate complex, hexamethyldisiloxane,
Perfluorodimethyldicyclohexane, tetrafluoroethylene, polytetrafluoroethylene, etc., as the horizontal aligning agent, carbon, polyoxyethylene, polyvinyl alcohol, polyimide, chromium brassylic acid complex,
There is acetylene. Further, as the aligning agent, in addition to the above-mentioned ones, those generally commercially available can be used as they are.

[0024]

According to the liquid crystal optical element of the present invention, the characteristics such as transmission scattering or transmission absorption can be controlled freely and highly. Further, in the liquid crystal optical element of the present invention, since the liquid crystal material can be injected under reduced pressure, it is possible to easily manufacture a uniform element having no defects such as bubbles.

[0025]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 On a glass substrate with indium-tin-oxide (ITO), a solution of polymethylisopropenyl ketone and 2,6-di- (4'azidobenzal) cyclohexanone in ethylcellosolve acetate (concentration 1
0%) was spin-coated to obtain a film having a thickness of 5 μm. Photolithography was performed using a deep UV exposure machine (PLA-501F manufactured by Canon). The mask is a 2 μmφ pattern and a 5 μm pitch chromium mask is used.
Methyl ethyl ketone was used as the developing solution. From the electron micrograph, it was confirmed that the obtained protrusions were cylindrical bodies in which the mask pattern was copied. The counter substrate was also manufactured by the same method. The two substrates thus produced are bonded together via a 12 μm spacer to produce an empty cell, and the 20 mmT
Nematic liquid crystal material TL205 (manufactured by Merck & Co., Inc .: ordinary light refractive index = 1.52) having a positive dielectric anisotropy under a reduced pressure of orr.
7, extraordinary light refractive index = 1.744, NI transition point = 87.
4 ° C.) was injected. No bubbles were observed in the driving surface of the device.

The electro-optical characteristics of the produced liquid crystal optical element are as follows.
The measurement was carried out using a He-Ne laser as a light source and a photodiode as a detector. The F value of the measurement system was 15. A rectangular alternating voltage (frequency 1 kHz) was applied to the element. The driving voltage at 25 ° C. was 6.5 V, and the hysteresis was 0.1 V. Light transmittance is 1% when no voltage is applied,
When the voltage is applied, the saturated transmittance is 80% and the contrast is 80.
Met. The response time when the voltage is on (10V) is 15ms
Then, it was 20 ms when the voltage was OFF. The charge retention rate of the device was 95%.

Example 2 On a glass substrate with indium-tin-oxide (ITO), a solution of polymethylmethacrylate and 2,6-di- (4'azidobenzal) cyclohexanone in ethylcellosolve acetate (concentration 10%).
Was spin-coated to obtain a film having a thickness of 5 μm. Deep U
Photolithography was performed using a V exposure machine (PLA-501F made by Canon). The mask used was a chromium mask having a pattern of 2 μm square and a pitch of 5 μm, and a mixed solution of methyl isobutyl ketone and isopropanol was used as a developing solution. From the electron micrograph, it was confirmed that the obtained protrusion was a rectangular parallelepiped in which the mask pattern was copied. The counter substrate was also manufactured by the same method. A nematic liquid crystal material RDP71120-1 having a positive dielectric anisotropy under a reduced pressure of 20 mmTorr is produced by adhering the two produced substrates together via a 12 μm spacer.
(Manufactured by Rodick: ordinary light refractive index = 1.511, extraordinary light refractive index = 1.725, NI transition point = 90.4 ° C.) was injected. No bubbles were observed in the driving surface of the manufactured device.

The electro-optical characteristics of the produced liquid crystal optical element were measured by the same measurement system as in Example 1. The driving voltage at 25 ° C. was 5V, and the hysteresis was 0.07V. The light transmittance when no voltage was applied was 2%, the saturated transmittance when a voltage was applied was 78%, and the contrast was 39. When voltage is on (7
V application) has a response time of 25 ms and 20 m when the voltage is off.
It was s. The charge retention of the device was 90%.

(Example 3) A substrate having a protrusion was produced in the same manner as in Example 2 except that an aluminum plate was used for one substrate. Next, lecithin, which is a vertical aligning agent, was applied to the surfaces of the two substrates (the surfaces having the protrusions). These two substrates were bonded together via a 12 μm spacer to form an empty cell, and a nematic liquid crystal material TL202 (manufactured by Merck: ordinary light refractive index = 1.511) having a positive dielectric anisotropy under a reduced pressure of 20 mmTorr. Extraordinary light refractive index = 1.72
5, a mixture of 98 wt% of N-I transition point = 90.4 ° C.) and 2 wt% of dichroic dye S344 (manufactured by Mitsui Toatsu) was injected. No bubbles were observed in the driving surface of the manufactured device.

The reflection characteristics of the produced liquid crystal optical element were measured using a D light source as a light source and a BM-5 luminance meter as a detector. Rectangular AC voltage (frequency 1kHz)
z) was applied. The driving voltage at 25 ° C. was 10V. The light reflectance when no voltage is applied is 1% (barium sulfate standard white plate is 100%), and the light reflectance when voltage is applied is 1
The contrast was 15 at 5%. The hysteresis was 0.10V. . The response time when the voltage was on (12 V applied) was 30 ms, and when the voltage was off, it was 25 ms.
The charge retention of the device was 93%.

Example 4 A substrate having projections was prepared in the same manner as in Example 2 except that the height of the projections was 6 μm. The two substrates thus prepared are bonded together via a 12 μm spacer to form an empty cell, and the empty cell is prepared at 20 mmTorr.
Chiral nematic liquid crystal material having positive dielectric anisotropy under reduced pressure (GR-63 (manufactured by Chisso Corporation: ordinary light refractive index = 1.5
25, extraordinary light refractive index = 1.748), a mixture of chiral dopant CM-33 (manufactured by Chisso Corporation). (Dopant concentration 5%). No bubbles were observed in the driving surface of the manufactured device.

The electro-optical characteristics of the produced liquid crystal optical element were measured by the same measurement system as in Example 1. The driving voltage at 25 ° C. was 12V, and the hysteresis was 0.25V. The light transmittance when no voltage was applied was 0.3%, the saturated transmittance when voltage was applied was 55%, and the contrast was 183. The response time when the voltage was on (15 V applied) was 25 ms, and when the voltage was off, it was 20 ms.

(Comparative Example 1) A liquid crystal optical element similar to that of Example 1 was prepared except that there were no protrusions, and the electro-optical characteristics were measured. As a result, the scattering intensity in the voltage-off state was weak and the contrast was 2 or less.

[0035]

As described above, according to the present invention,
Properties such as transmission scattering and transmission absorption can be controlled highly and freely. Furthermore, since the liquid crystal material can be injected under reduced pressure, a uniform element without bubbles can be manufactured.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal optical element of the present invention.

FIG. 2 is a graph of light transmittance of the liquid crystal optical element according to Example 1 of the present invention.

[Explanation of symbols]

 1 Substrate 2 Electrode Layer 3 Liquid Crystal Material 4 Projection 5 Spacer

Claims (4)

[Claims] 1. A liquid crystal optical element in which a liquid crystal material is sandwiched between two substrates with electrode layers, wherein at least one substrate has a protrusion that disturbs the alignment of liquid crystals. 2. The liquid crystal optical element according to claim 1, wherein the protrusion is provided on the light control section of the substrate. 3. The liquid crystal optical element according to claim 1, wherein the protrusions are oriented. 4. The liquid crystal optical element according to claim 1, wherein at least one of the substrates with electrode layers is subjected to alignment treatment.