JPH0611694A - Liquid crystal optical element and its production - Google Patents

Abstract

PURPOSE:To increase the light scattering intensity of a polymer-dispersion liq. crystal element to the theoretical maximum and to provide the element capable of easily realizing a reverse mode. CONSTITUTION:A soln. consisting of a photosetting high molecular compd. precursor 4 and a liq. crystal material 3 is held by two substrates 1, an electric field or a magnetic field is impressed to orient the material 3 in the specified manner, the soln. is irradiated with light, and the precursor is cured to form a dimmer layer. Even if the material 3 is extracted from the dimmer layer and another liq. crystal material is injected, the material is oriented in the same way when an electric field is not impressed. Consequently, the precursor is cured by using a liq. crystal material having negative permittivity anisotropy, then a liq. crystal material having positive permittivity anisotropy is injected, and an element having a high scattering intensity is obtained. When the precursor is cured by using a liq. crystal material having positive permittivity anisotropy and a liq. crystal material having negative permittivity anisotropy is injected, a reverse-mode element is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / scattering type liquid crystal optical element in which the orientation of a liquid crystal material-photocurable compound interface is controlled, and a method for producing the same. , Display devices for displaying figures, dimming glass for controlling transmission / blocking of incident light, optical shutters, etc.

[0002]

2. Description of the Related Art Liquid crystal display devices of the TN type and the STN type using nematic liquid crystals have been put into practical use. However, since these require polarizing plates, they have the drawback of being limited in brightness and contrast. On the other hand, as an element that does not require a polarizing plate
Japanese Patent Publication No. 01631 discloses an element in which a liquid crystal material is encapsulated and dispersed in a polymer. In this polymer-dispersed liquid crystal element, the refractive index of either the major axis direction or the minor axis direction of the liquid crystal molecule is made equal to the refractive index of the polymer substance, and the transparent-scattering state is obtained by changing the direction of the liquid crystal. Are in control. Further, as a similar device utilizing the change of the refractive index of the liquid crystal material, there is known one in which a liquid crystal material is dispersed in a photocurable compound (Japanese Patent Laid-Open No. 62-2231). In this polymer-dispersed liquid crystal element, a substrate coated with a transparent conductive film such as ITO is combined so that the transparent conductive film is on the inside, and a photocurable compound in which liquid crystal droplets are dispersed is sandwiched between the substrates. ing. This liquid crystal element
It is prepared by injecting a mixed solution of a photocurable compound and a liquid crystal material having a positive dielectric anisotropy between two substrates and irradiating with light. When irradiated with light, the liquid crystal material is spherically separated when the photocurable compound is cured. The average molecular direction of this liquid crystal element is an arbitrary direction without applying a voltage.
In this state, since the photocurable polymer and the liquid crystal droplet have different refractive indexes, incident light from the outside is scattered. On the other hand, when a voltage is applied to this liquid crystal element, since the dielectric anisotropy of the liquid crystal material is positive, the average molecules of the liquid crystal are aligned so as to be perpendicular to the substrate when a voltage is applied. If the refractive index of the liquid crystal material in the long axis direction is set to be equal to the refractive index of the photocurable polymer, light incident from the outside when a voltage is applied is transmitted without being scattered. Further, it has been reported that when a voltage is applied and the liquid crystal material is aligned while being irradiated with light to be cured, the state in which the voltage is applied is maintained even when the voltage is turned off (Japanese Patent Laid-Open No. 63-301922).

[0003]

[Problems to be Solved by the Invention] Tokushusho Sho-50-5016
If it is desired to maximize the light scattering intensity in the polymer-dispersed liquid crystal device disclosed in JP-A-31-31, the difference between the refractive index of the liquid crystal material and the refractive index of the photocurable compound may be maximized. That is, the average molecular direction of the liquid crystal material may be horizontal to the substrate. However, the directions of the liquid crystal molecules when the voltage is removed are random, and when the liquid crystal element is macroscopically observed, the refractive index of the liquid crystal droplets depends on the refractive index in the major axis direction and the refractive index in the minor axis direction of the liquid crystal material. Takes between the refractive index. Therefore, there is a problem that the difference in refractive index between the liquid crystal material and the photocurable compound is smaller than the refractive index anisotropy of the liquid crystal material, and the light scattering state deteriorates. Further, in the polymer-dispersed liquid crystal element described in JP-A-63-301922, the directions of the liquid crystal molecules are not random even when the voltage is turned off, and the alignment state during curing is maintained. However, normally, the alignment state at the time of curing is not changed, and the alignment state is kept constant. When changing the alignment state, it is only possible to change the liquid crystal molecules which are aligned at an angle to the substrate surface in a direction perpendicular to the substrate. Also in this case,
Similar to the above, there is a problem that the difference in refractive index between the liquid crystal material and the polymer substance is smaller than the refractive index anisotropy of the liquid crystal material. An object of the present invention is to solve the above problems and to theoretically maximize the ratio of the light transmission state and the light scattering state. Another object of the present invention is to provide a liquid crystal optical element that can easily realize a reverse mode.

[0004]

The present invention provides a liquid crystal optical element having a photocurable polymer compound and a liquid crystal material sandwiched between two substrates having at least one transparent electrode layer. The liquid crystal material is a liquid crystal material different from that at the time of photo-curing, and the liquid crystal material is oriented in a predetermined direction by interaction of the interface between the photo-curable polymer compound and the liquid crystal material. And a liquid crystal optical element (claim 1). The manufacturing method is such that a solution comprising a photocurable polymer compound precursor and a liquid crystal material is injected between two substrates, at least one of which has an electrode layer and is transparent, and the molecular axis direction of the liquid crystal material is relative to the substrates. The light-curable polymer compound precursor is cured by irradiating light while applying an electric field or magnetic field above the Frederick transition point so as to form a predetermined alignment state between the substrates to form a dimming layer. After that, the liquid crystal material is extracted from between the substrates, and another liquid crystal material is injected into the holes (claim 2).

Further, the present invention is a liquid crystal optical element comprising a photocurable polymer compound and a liquid crystal material sandwiched between two substrates having at least one transparent electrode layer. Is a liquid crystal material different from that at the time of photo-curing, and the liquid crystal material is oriented in a direction perpendicular to the substrate due to the interaction of the interface between the liquid crystal material and the photo-curable polymer compound. And a liquid crystal optical element (claim 3). The manufacturing method is such that a solution of a photocurable polymer compound precursor and a liquid crystal material having a positive dielectric anisotropy is injected between two substrates having at least one transparent electrode layer, and the liquid crystal material Dimming is performed by irradiating light while applying an electric field or magnetic field above the Frederick transition point such that the molecular axis direction is perpendicular to the substrate to the substrate to cure the photocurable polymer compound precursor. After forming the layer, the liquid crystal material is extracted from the light control layer, and a liquid crystal material having a negative dielectric anisotropy is injected into the holes (claim 4). According to the inventions of claims 3 and 4, since the liquid crystal molecules are aligned vertically to the substrate when no voltage is applied and are parallel to the substrate when a voltage is applied, the refractive index in the molecular axis direction of the liquid crystal material is If the refractive index of the photocurable polymer compound is set to be equal to that of the photocurable polymer compound, it is possible to realize a liquid crystal optical element that is in a transparent state when no voltage is applied and in a scattering state when a voltage is applied.

Further, the present invention is a liquid crystal optical element comprising a photocurable polymer compound and a liquid crystal material sandwiched between two substrates having at least one transparent electrode layer.
The liquid crystal material is a liquid crystal material different from that at the time of photo-curing, and the liquid crystal material is aligned in a direction parallel to the substrate by the interaction of the interface between the liquid crystal material and the photo-curable polymer compound. It is a characteristic liquid crystal optical element (Claim 5). The manufacturing method is to inject a solution composed of a photocurable polymer compound precursor and a liquid crystal material having a negative dielectric anisotropy between two substrates having at least one transparent electrode layer,
The photocurable polymer compound precursor is obtained by irradiating light while applying an electric field or magnetic field of a Frederick transition point or more such that the molecular axis direction of the liquid crystal material is parallel to the substrate, between the substrates. After being cured to form a light control layer, the liquid crystal material is extracted from the light control layer, and a liquid crystal material having a positive dielectric anisotropy is injected into the holes (claim 6). According to the fifth and sixth aspects of the invention, the liquid crystal molecules are aligned parallel to the substrate when no voltage is applied, and are perpendicular to the substrate when a voltage is applied. Therefore, the refractive index in the molecular axis direction of the liquid crystal material is When the refractive index is set to be equal to the refractive index of the photocurable polymer compound, it is possible to realize a liquid crystal optical element that exhibits high scattering characteristics when no voltage is applied.

In the liquid crystal optical element of the present invention, a method of sandwiching a mixture of a liquid crystal material, a photocurable polymer compound precursor and, if necessary, a photocuring initiator between substrates having electrode layers is usually Any method may be used as long as the polymer-dispersed liquid crystal is formed. For example, there is a method of injecting the mixture into a cell in which a gap between the substrates is determined, a method of placing the mixture on one substrate and stacking another substrate thereon. The substrate used in the present invention has a highly transparent electrode layer such as ITO on the surface, and at least one of the substrates is transparent, and glass, plastic, metal or the like can be used. The two substrates are installed so that the electrodes are on the light control layer side. Spacers used in ordinary liquid crystal devices can be used to set the distance between the substrates, and the distance is preferably about 3 μm to 30 μm.
Although the electrode layer may be formed uniformly on the substrate, a simple matrix configuration in which the strip-shaped electrodes are arranged orthogonally to each other between the opposing substrates, or active elements are added in pixel units It may have an active matrix configuration.

The liquid crystal material used in the present invention is not particularly limited as long as it is a liquid crystal material, and any of nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal and the like can be used. It is also possible to colorize by a host-guest type in which a dichroic dye is mixed. Further, by changing the frequency, a dual-frequency drive liquid crystal whose dielectric anisotropy can take both positive and negative values can be used.
The photocurable polymer compound precursor is usually a polymer precursor that forms a cured product by irradiation with light such as ultraviolet rays, and is a polymerizable monomer or polymerizable oligomer or a mixture of a polymerizable monomer and a polymerizable oligomer. Etc. can be used. As the polymerizable monomer, methyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate,
Examples thereof include acrylic monomers such as butanediol monoacrylate, and may be a single substance or a mixture of two or more types of substances. Examples of the polymerizable oligomer include urethane acrylate oligomer type, epoxy acrylate oligomer type, ester oligomer type and the like, and may be a single substance or a mixture of two or more types. As the photocuring initiator, those used as an initiator of a general photocurable compound can be used. For example, acetophenone-based, benzoin-based, benzophenone-based, thioxanthone-based, etc. are used as the initiator of the ultraviolet curable compound. The initiator may be solid or liquid, but it is desirable that it be soluble or compatible with the photocurable compound from the viewpoint of uniformity of the device.

The shape of the liquid crystal material present in the light control layer varies depending on the concentration and type of the liquid crystal material used and the photo-curable compound, but even if the liquid crystal material is dispersed in the photo-curable compound, the photo-curable compound is photo-cured. The polymerizable compound may be present in the liquid crystal material in the form of a three-dimensional network, or the photocurable compound may be dispersed in the liquid crystal material. In the method for producing a liquid crystal optical element of the present invention, as a method for extracting the liquid crystal material from between the substrates, an ordinary extraction method with a solvent is preferable. Any solvent may be used as the solvent insofar as the cured photocurable compound is insoluble, and the liquid crystal material is not necessarily soluble. As a method for injecting the liquid crystal material into the holes between the substrates, injection under reduced pressure which is used for ordinary TN-type liquid crystal injection is preferable, but not limited to this. Applications of the liquid crystal optical element of the present invention include building materials such as windows and partitions, and display devices for displaying characters and figures.

[0010]

In the polymer dispersed liquid crystal device, in order to maximize the ratio between the light transmitting state and the light scattering state, the refractive index of the photocurable compound and the liquid crystal material should be matched in the light transmitting state, and At this time, the difference in refractive index between the photocurable compound and the liquid crystal material may be maximized. That is, one of the refractive index in the major axis direction (molecular axis) and the refractive index in the minor axis direction of the liquid crystal material and the refractive index of the photocurable compound are made to coincide with each other so that the direction of the liquid crystal molecules is horizontal to the substrate. The configuration may be such that it can control the state in which it faces and the state in which it faces in a direction perpendicular to it. In the present invention, when the photocurable compound is cured, light is irradiated while an electric field is applied between the substrates such that the molecular axis direction of the liquid crystal material having negative dielectric anisotropy is parallel to the substrates. . Therefore, the liquid crystal material is fixed in the state of being aligned in the direction parallel to the substrate at the interface with the photocurable compound. After curing of the photocurable compound, the liquid crystal molecules cannot be returned to a random state even if the electric field at the time of production is cut off by the anchoring of this interface, and the liquid crystal molecules are fixed. The orientation ability of this interface is maintained even when the liquid crystal material used during curing is extracted and another liquid crystal material is injected. Therefore, if a liquid crystal with positive dielectric anisotropy is injected here,
This liquid crystal is parallel to the substrate when no voltage is applied, and is perpendicular to the substrate when a voltage is applied. Further, in the present invention, when the photocurable compound is cured, an electric field such that the molecular axis direction of the liquid crystal material having a positive dielectric anisotropy is oriented in the direction perpendicular to the substrate, or a magnetic field higher than the Frederick transition point of the liquid crystal material is applied. Light is applied while being applied between the substrates. Therefore, the liquid crystal material is fixed in the state of being aligned in the direction perpendicular to the substrate at the interface with the photocurable compound. After curing of the photocurable compound, the liquid crystal molecules cannot be returned to a random state even if the electric field at the time of production is cut off by the anchoring of this interface, and the liquid crystal molecules are fixed. The orientation ability of this interface is maintained even when the liquid crystal material used during curing is extracted and another liquid crystal material is injected. Therefore, when a liquid crystal with negative dielectric anisotropy is injected here, a liquid crystal optical element in the reverse mode is realized in which this liquid crystal is perpendicular to the substrate when no voltage is applied and is parallel to the substrate when voltage is applied. it can.

[0011]

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 unless it exceeds the gist. Example 1 1 part of a polymerizable monomer 2-ethylhexyl acrylate, 1 part of a polymerizable oligomer UN9000PEP (manufactured by Negami Kogyo Co., Ltd.), and a liquid crystal material E-8 having a positive dielectric anisotropy
A mixed solution of 3.7 parts (manufactured by Merck & Co., Inc.) and 0.02 part of a polymerization initiator 2,2-diethoxyacetophenone was injected into a liquid crystal cell having a gap of 10 μm. This liquid crystal cell 3
The temperature was kept at 2 ° C., and while applying a rectangular wave AC voltage of 100 Hz and 50 V, ultraviolet rays were irradiated to polymerize. FIG. 1 is a cross-sectional view of a liquid crystal optical element obtained in this example, in which 1 is a substrate, 2 is an electrode layer, 3 is a liquid crystal material, and 4 is a photocurable polymer compound. When observed by SEM, the size of the liquid crystal droplet 3 in the obtained film was 1 to 2 μm. The light transmittance of the obtained liquid crystal optical element was 95%. The liquid crystal material of this device was extracted with methanol. After drying the device under reduced pressure, the liquid crystal material NR-10 having a negative dielectric anisotropy
23XX (manufactured by Chisso Petrochemical Co., Ltd.) was injected under reduced pressure. The light transmittance of the obtained liquid crystal optical element was 93% when no voltage was applied, and the element transmittance was 1% when 100 Hz and 50 V were applied. FIG. 2 shows the waveform of the rectangular wave AC voltage applied to the liquid crystal optical element and the light transmittance of the liquid crystal optical element at this time.

Example 2 1 part of a polymerizable monomer 2-ethylhexyl acrylate, 1 part of a polymerizable oligomer UN9000PEP (manufactured by Negami Kogyo Co., Ltd.), and a liquid crystal material NR- having a negative dielectric anisotropy
3.73 parts of 1023XX (manufactured by Chisso Petrochemical Co., Ltd.),
A mixed solution of 0.02 parts of a polymerization initiator benzophenone was injected into a liquid crystal cell having a gap of 10 μm. This liquid crystal cell was kept at 20 ° C., and while being applied with a rectangular wave AC voltage of 100 Hz and 50 V, it was irradiated with ultraviolet rays and polymerized to obtain a liquid crystal optical element as shown in FIG. When observed by SEM, the size of the liquid crystal droplets in the obtained film was 2-3 μm. The light transmittance of the obtained liquid crystal optical element was 0%. The liquid crystal material of this device was extracted with methanol. After drying under reduced pressure, liquid crystal material E-8 having positive dielectric anisotropy
(Manufactured by Merck) was injected under reduced pressure. The light transmittance of the obtained liquid crystal optical element is 100% when no voltage is applied and is 0%.
The transmittance of the device was 97% when z and 50 V were applied. In the above-mentioned examples, the driving is performed by the rectangular wave, but the similar driving could be performed by using other AC electric fields such as sine wave and triangular wave.

[0013]

As described above, by using the liquid crystal optical element according to the present invention, the light scattering intensity can be set to the theoretical maximum value. Further, a reverse mode element can be easily realized.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a liquid crystal optical element according to the present invention.

FIG. 2 is a diagram showing a waveform of a rectangular wave AC voltage applied to a liquid crystal optical element and a light transmittance of the liquid crystal optical element in Example 1 of the present invention.

[Explanation of symbols]

 1 substrate 2 electrode layer 3 liquid crystal material 4 photocurable polymer compound

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideya Murai Inventor Hideya Murai 5-7-1, Shiba, Minato-ku, Tokyo NEC Corporation

Claims (6)

[Claims] 1. A liquid crystal optical element comprising a photocurable polymer compound and a liquid crystal material sandwiched between two substrates, at least one of which has an electrode layer and which is transparent. Are different liquid crystal materials, and the liquid crystal material is aligned in a predetermined direction by the interaction of the interface between the photocurable polymer compound and the liquid crystal material. 2. A solution comprising a photocurable polymer compound precursor and a liquid crystal material is injected between at least one transparent substrate having an electrode layer, and the liquid crystal material has a molecular axis direction with respect to the substrate. The light-curable polymer compound precursor is cured by irradiating light while applying an electric field or magnetic field above the Frederick transition point so as to form a predetermined alignment state between the substrates to form a dimming layer. After that, the liquid crystal material is extracted from between the substrates, and another liquid crystal material is injected into the pores of the liquid crystal optical element manufacturing method. 3. A liquid crystal optical element comprising a photocurable polymer compound and a liquid crystal material sandwiched between at least one transparent substrate having an electrode layer, wherein the liquid crystal material is at the time of photocuring. A liquid crystal material different from that, and the liquid crystal material is aligned in a direction perpendicular to the substrate due to the interaction of the interface between the liquid crystal material and the photocurable polymer compound. element. 4. A solution of a photocurable polymer compound precursor and a liquid crystal material having a positive dielectric anisotropy is injected between two substrates having at least one transparent electrode layer, and the liquid crystal material Dimming is performed by irradiating light with the electric field or magnetic field above the Frederick transition point such that the molecular axis direction is perpendicular to the substrate is applied between the substrates to cure the photocurable polymer compound precursor. After the layer is formed, the liquid crystal material is extracted from the light control layer, and a liquid crystal material having a negative dielectric anisotropy is injected into the pores of the liquid crystal material. 5. A liquid crystal optical element comprising a photocurable polymer compound and a liquid crystal material sandwiched between two substrates, at least one of which has an electrode layer and is transparent, wherein the liquid crystal material is photocurable. And a photo-curable polymer compound. The liquid crystal optical element is characterized in that the liquid crystal material is aligned in a direction parallel to the substrate due to the interaction of the interface between the liquid crystal material and the photocurable polymer compound. 6. A liquid crystal material comprising a photocurable polymer compound precursor and a liquid crystal material having a negative dielectric anisotropy is injected between two substrates having at least one transparent electrode layer. The photocurable polymer compound precursor is cured by irradiating with light in a state in which an electric field or a magnetic field having a Frederick transition point or more such that the molecular axis direction of the is parallel to the substrate is applied between the substrates, A method for producing a liquid crystal optical element, comprising forming the light control layer, extracting the liquid crystal material from the light control layer, and injecting a liquid crystal material having a positive dielectric anisotropy into the holes.