JPH11142821A - Optical response element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable writing and rewriting with light by mixing a liquid crystal with a monomer or oligomer having a photoresponsive part, polymerizing the mixture to obtain a polymer dispersion-type liquid crystal and irradiating the liquid crystal with polarized light. SOLUTION: The polymer dispersion-type liquid crystal used is prepared by mixing a liquid crystal and a monomer or oligomer having a photoresponsive part and then polymerizing the mixture, and this liquid crystal is a polarizing polymer dispersion-type liquid crystal in which the liquid crystal is oriented by irradiation of polarized light. As for the monomer having a photoresponsive part to be used, monomers which are polymerized by heat or light are usually used, and acryl monomers, acrylic acid monomers, methacrylic acid monomers, vinyl monomers and epoxy monomers are preferable. As for the oligomer having a photoresponsive part, oligomers which are polymerized by heat or light are used, and urethane acrylates, epoxy acrylates, polyester acrylates, polyether acrylates and polyesterurethane acrylates are preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel liquid crystal optical element utilizing a change in alignment by light. More specifically, a polymer-dispersed liquid crystal obtained by mixing and polymerizing a liquid crystal with a monomer or oligomer containing a photoresponsive site, wherein the liquid crystal is oriented by irradiating polarized light. Related to liquid crystal.

[0002]

2. Description of the Related Art As a liquid crystal optical element using a liquid crystal material, there are a liquid crystal optical element using a change in liquid crystal alignment by an electric action,
Some of them utilize a liquid crystal phase change or alignment change caused by the action of light. Use these changes to store information,
Erasing can be performed to function as an optical element.

[0003] As a method of utilizing the electric action, there are the following methods. A device in which a nematic liquid crystal is sandwiched between two substrates having a transparent electrode layer and utilizes the birefringence, optical rotation, and light scattering of the liquid crystal phase. 2. It uses the bistability and birefringence of chiral smectic liquid crystals. 3. A device that uses the phase transition of cholesteric liquid crystal. 4. A device utilizing light scattering due to an electric field change of a polymer-dispersed liquid crystal obtained by mixing and polymerizing a nematic liquid crystal and a monomer (see Japanese Patent Application Laid-Open No. Hei 1-312527). It has been known.

[0004] On the other hand, a method utilizing a phase change and an orientation change of a liquid crystal caused by the action of light includes: A low molecular weight, high molecular weight nematic liquid crystal in which a compound having an optically responsive site is dissolved (see "Opto News", 1993, No. 3, page 16). 2. Optically responsive sites chemically bonded to the substrate surface (K. Ichimura, Y. Suzuki, T. Seki, A. Hosoki, K. Aok
i, Langmuir, 4, 1214 (1988)). It has been known.

[0005]

In a conventional optical element utilizing an optical change by an electric action, the size of an electrode,
The display resolution is restricted by the shape, and it is difficult to achieve high definition. On the other hand, in a display method using optical writing, high-definition display is possible without being restricted by electrodes. However, when a compound having optical responsiveness is dissolved in the liquid crystal or exists only on the surface of the substrate, after the light responsive site is induced by light, the morphology and orientation of the surrounding liquid crystal molecules are changed. In order to write information, a long response time of several tens to several hundreds of seconds was required. In addition, since the ability to control the liquid crystal in the light responsive portion is weak, the liquid crystal returns to its original state in several tens of seconds, and it is difficult to preserve optical changes due to light for a long time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoresponse element which compensates for the drawbacks of the prior art, can store information by optical writing for a long time, and can perform high-definition display which can be easily rewritten. is there.

[0007]

The present invention has been made in order to solve the above problems. A polymer-dispersed liquid crystal obtained by mixing and polymerizing a liquid crystal with a monomer or oligomer containing a photoresponsive portion, wherein the liquid crystal is oriented by irradiating polarized light. Dispersion type liquid crystal. 2. Monomers or oligomers containing photoresponsive sites are acrylic monomers, acrylic acid monomers, methacrylic acid monomer vinyl monomers, epoxy monomers or urethane acrylates, epoxy acrylates, polyester acrylates, polyether acrylates,
2. The polymer-dispersed liquid crystal according to the above 1, wherein the liquid crystal is at least one kind of polyester urethane acrylate. 3. The photoresponsive site is at least one of an azobenzene derivative, a stilbene derivative, a spiropyran derivative, an α-aryl-β-keto acid ester derivative or a chalcone derivative
2. The polymer-dispersed liquid crystal according to the above 1, which is a seed. 4. 2. The polymer-dispersed liquid crystal according to the above item 1, wherein the site capable of responding to light is azobenzene. 5. The orientation of the liquid crystal obtained by irradiating polarized light is
2. The polymer-dispersed liquid crystal according to the above item 1, wherein the liquid crystal is realigned by irradiating polarized light again. 6. 2. The polymer-dispersed liquid crystal according to the above 1, wherein the polarized light to be irradiated is visible polarized light. As the above-mentioned solution.

[0008] To solve the above problems, the present inventors have
As a result of intensive studies on liquid crystal optical elements using light,
By mixing and polymerizing a liquid crystal with a monomer or oligomer containing a site that can respond to light, polymer-dispersed liquid crystal is created, and by irradiating polarized light to orient the liquid crystal,
The present inventors have found a photoresponsive liquid crystal optical element capable of storing information by optical writing for a long time and capable of easily rewriting and capable of high-definition display, and have completed the present invention.

That is, the present invention provides a polymer-dispersed liquid crystal obtained by mixing and polymerizing a liquid crystal with a monomer or oligomer containing a site capable of photoresponse to solve the above-mentioned problem. Is a polymer-dispersed liquid crystal characterized in that the liquid crystal is oriented by irradiating the polymer. In the photoresponsive liquid crystal optical element according to the present invention, the photoresponsive portion is three-dimensionally fixed by polymerizing a monomer or oligomer containing the photoresponsive portion. Therefore, compared to the case where the compound having an optically responsive part is dissolved in the liquid crystal, after the light responsive part is induced by the light, the information written by changing the form and orientation of the surrounding liquid crystal molecules is changed. Can be stored for a long time. In addition, compared to the case where a compound having a photoresponsive site only on the surface of the substrate is present, since the photoresponsive portion exists not two-dimensionally but three-dimensionally, the controllability for the surrounding liquid crystal is increased.
The morphology and orientation of liquid crystal molecules can be changed quickly and easily.

The present invention will be described in further detail. By irradiating polarized light to a polymer-dispersed liquid crystal formed by polymerization by heat and light, the induced orientation of the photoresponsive portion is regulated by the polarization direction. You. The aligned light-responsive portion promotes the alignment of the liquid crystal, so that the light-irradiated portion increases the orientation, causing a difference in the transmission and absorption of light from the non-light-irradiated portion, thereby preserving information.

When this alignment is irradiated with a second polarized light having a polarization axis in a direction different from that of the first irradiation, it is re-oriented, and
The liquid crystal undergoes the alignment induced by the second polarized light irradiation.
Due to this effect, information can be rewritten.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of a photoresponsive device according to the present invention will be described. The present invention is a polymer-dispersed liquid crystal obtained by mixing and polymerizing a liquid crystal with a monomer or oligomer containing a photoresponsive portion, and the liquid crystal is oriented by irradiating polarized light. And a polymer-dispersed liquid crystal.

[0013] The monomer or oligomer containing a photoresponsive site may be an acrylic monomer, an acrylic acid monomer, a methacrylic acid monomer vinyl monomer, an epoxy monomer, or urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, polyester urethane acrylate. A polymer-dispersed liquid crystal, wherein the liquid crystal is oriented by irradiating polarized light.

Further, the present invention provides a polymer-dispersed liquid crystal in which the photoresponsive site is at least one of an azobenzene derivative, a stilbene derivative, a spiropyran derivative, an α-aryl-β-keto acid ester derivative or a chalcone derivative. Further, the present invention relates to a polymer-dispersed liquid crystal characterized in that the liquid crystal is oriented by irradiating polarized light.

A polymer-dispersed liquid crystal obtained by mixing and polymerizing a liquid crystal and a monomer or oligomer whose photoresponsive portion is azobenzene, and the liquid crystal is oriented by irradiating polarized light. The present invention relates to a polymer-dispersed liquid crystal.

Further, according to the present invention, the liquid crystal obtained by irradiating the polarized light is obtained by mixing the liquid crystal with a monomer or oligomer containing a photoresponsive portion which reorients by irradiating the polarized light again. And a polymer-dispersed liquid crystal obtained by polymerization.

The present invention also relates to a polymer-dispersed liquid crystal obtained by mixing and polymerizing a liquid crystal with a monomer or oligomer containing a photoresponsive portion capable of aligning the liquid crystal with visible polarized light. Related.

Hereinafter, the present invention will be described in detail. As the monomer containing a photoresponsive site used in the present invention, those which generally undergo thermal polymerization and photopolymerization can be used, but acrylic monomers, acrylic acid monomers, vinyl methacrylate monomers, and epoxy monomers are preferred.

As the oligomer having a photoresponsive site used in the present invention, those which generally undergo thermal polymerization and photopolymerization can be used. Urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, polyester urethane acrylate Is preferred.

The site capable of photoresponsiveness is considered to be a site having light absorption, which has the effect of the present invention. Preferably, the azobenzene derivative, stilbene derivative, spiropyran derivative, α-aryl-β-keto acid ester derivative or It is a chalcone derivative, particularly preferably an azobenzene derivative.

The irradiation of polarized light can be carried out at room temperature, but it is preferable to carry out the irradiation of the polymer-dispersed liquid crystal at a temperature higher than room temperature. Particularly preferably, 70 ° C
Polarized light irradiation in a state of being heated to ８０80 ° C. Light irradiation energy is preferably 0.5 J / cm ² or more,
Particularly, an energy of ² J / cm ² or more is preferable. The wavelength of the polarized light is most preferably the absorption wavelength of the light-responsive portion. Visible light is preferable, and for azobenzene, 400
-450 nm is preferred, and 430-440 nm is particularly preferred.

Further, the present invention relates to the fact that the orientation of the liquid crystal obtained by irradiating polarized light is realigned by irradiating polarized light again. As described above, the display written on the polymer-dispersed liquid crystal by irradiating light to the photoresponsive portion and orienting it, and further irradiating polarized light in a different direction, changes the orientation direction of the liquid crystal and reorients it. Then, a new display can be written.

[0023]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. (Example 1) [Sample preparation] 4- (2-acryloylethoxy) azobenzene (AzM2A), 0.021 g, liquid crystal composition DON-103 (composition described below) 0.38 g was dissolved in methylene chloride, and vacuum was applied for 1 hour. Dry and remove the methylene chloride. Further, a solution of benzoyl peroxide (BPO) in methylene chloride (concentration 10% by weight)
After adding 0 μl and drying under vacuum for 1 hour, 0.021 g (20 μl) of 1,4-butanediol diacrylate (BDA) is added and the mixture is vigorously stirred. The obtained mixture is sandwiched between glass plates,
After sealing with an epoxy resin, the mixture was heated at 80 ° C. for 10 minutes and polymerized to obtain a polymer-dispersed liquid crystal. DO
N-103 is an equal weight percent composition of the following three compounds.

[0024]

Embedded image

[Light Irradiation] While heating the obtained cell to 75 ° C., as shown in FIG. 1, a light irradiator mercury lamp, a colored glass filter, Y-43, V-44 (Toshiba), a polarizing plate 436 nm polarized light obtained by using, the energy of the irradiation light is 0.5
^{0J / cm 2, 1.0J / cm} 2, 2.0J / cm 2, by irradiating the polymer dispersed liquid crystal sample was placed 5.0J / cm ^2, the heating device so as to 10J / cm ^2, A photo-aligned polymer dispersed liquid crystal was obtained. The obtained orientation had a long-term storage property. [Measurement] The photo-aligned polymer-dispersed liquid crystal obtained when the energy of the irradiation light was 10 J / cm ² was sandwiched between two orthogonal polarizing plates as shown in FIG. The direction was rotated α ° counterclockwise from the direction of the upper polarizing plate, and the luminance was measured at room temperature and observed. FIG. 3 shows the observed photograph. In FIG. 3, the upper left is α = 0 ° and the upper right is α = 15.
゜, the lower left is a photograph observing the luminance at α = 30 °, and the lower right is an observation of the luminance at α = 45 °. It can be seen that the liquid crystal is the brightest when α = 45 ° and the darkest when α = 0 °, and the liquid crystal is aligned in one direction due to polarized light.

The absorption spectra of the polymer-dispersed liquid crystal, which was photoaligned at an irradiation light energy of 10 J / cm ² , in the direction parallel to and perpendicular to the polarization by irradiation at 436 nm used for photoalignment were measured. Before the irradiation of polarized light, there is no difference between the parallel and perpendicular absorptions, and they agree (see FIG. 4). It can be understood that the liquid crystal material is isotropic. It is larger (see FIG. 5). This is presumably because the liquid crystal was oriented by the irradiation of polarized light, and the scattering was increased.

Further, the obtained photo-aligned polymer-dispersed liquid crystal is rotated with respect to a polarizing plate (angle φ ゜) by a measurement system shown in FIG. 6 and is irradiated with a He-Ne-laser (633 nm) at room temperature. The transmitted light intensity was measured at an irradiation temperature of 75 ° C. and room temperature, and observed.
The results of the observation are shown in FIG. When the rotation angle Φ, which is an angle formed with the polarizing plate, is 0 °, 90 °, 180 °, 270 °, and 360 °, it is darkest, and when 45 °, 135 °, 225 °, and 315 °, it is the brightest. As a result, the liquid crystal is oriented in one direction by the polarized light irradiation, and the angle between the polarized direction of the irradiated polarized light and the polarizing plate is changed.
If it is perpendicular to the direction of polarization, such as 90 °, the irradiated part can be displayed in black, and if the direction of polarization of the irradiated polarized light and the angle between the polarizers are parallel to 0 °, 180 °, etc. ,
It can be seen that bright writing can be performed on a dark background.

At a heating temperature of 75 ° C., the polarization direction
The polymer-dispersed liquid crystal obtained by irradiating polarized light of 6 nm (FIG. 8) was again irradiated with polarized light in the 45 ° direction (FIG. 9), and the light transmittance of the polymer-dispersed liquid crystal was measured. Figure 1 shows the result
0. It can be seen that the orientation of the liquid crystal obtained by the first irradiation (0 °) is rotated by 45 ° between light and dark by the second irradiation (45 °). As described above, it is understood that the present invention can re-orient the display once written by the optical alignment by irradiating the polarized light again. (Example 2) A sample was prepared under the same conditions as in Example 1 and the light irradiation was performed using the same light source as in Example 1 and the irradiation light was heated to 35 degrees and the energy of the irradiation polarized light was 0.50 J / cm ² . 2.0J /
cm ^2, was irradiated so as to ^{5.0J / cm 2, 10J / cm} 2, Example 1
A polymer-dispersed liquid crystal oriented in the same manner as in was obtained. (Example 3) A sample was prepared under the same conditions as in Example 1 and the light irradiation was performed using the same light source as in Example 1 and the irradiation light was heated to 40 degrees and the energy of the irradiation polarization was 0.50 J / cm ² . 2.0J /
cm ^2, was irradiated so as to ^{5.0J / cm 2, 10J / cm} 2, Example 1
A polymer-dispersed liquid crystal oriented in the same manner as in was obtained. (Example 4) A sample was prepared under the same conditions as in Example 1 and the light was irradiated with the same light source as in Example 1 while heating to 47.5 degrees while the energy of the irradiation polarization was 0.50 J / cm ² , 2.0
J / cm ^2, was irradiated so as to ^{5.0J / cm 2, 10J / cm} 2, Example
A polymer-dispersed liquid crystal aligned in the same manner as in 1 was obtained. (Example 5) A sample was prepared under the same conditions as in Example 1 and the light irradiation was performed using the same light source as in Example 1, while heating to 50 degrees and the energy of the irradiation polarization was 0.50 J / cm ² , 2.0J /
cm ^2, was irradiated so as to ^{5.0J / cm 2, 10J / cm} 2, Example 1
A polymer-dispersed liquid crystal oriented in the same manner as in was obtained. (Example 6) A sample is prepared under the same conditions as in Example 1. Light irradiation was also performed using the same light source as in Example 1, and while heating to 57 degrees, the energy of the irradiation polarized light was 0.50 J / cm ² , 2.0 J /
cm ^2, was irradiated so as to ^{5.0J / cm 2, 10J / cm} 2, Example 1
A polymer-dispersed liquid crystal oriented in the same manner as in was obtained. (Example 7) A sample is prepared under the same conditions as in Example 1. Light irradiation was also performed using the same light source as in Example 1 and the irradiation polarization energy was 0.50 J / cm ² , 2.0 J /
cm ^2, was irradiated so as to ^{5.0J / cm 2, 10J / cm} 2, Example 1
A polymer-dispersed liquid crystal oriented in the same manner as in was obtained. (Example 8) A sample was prepared under the same conditions as in Example 1 and the light irradiation was performed using the same light source as in Example 1, while heating to 25 degrees, the energy of the irradiation polarization was 0.50 J / cm ² , 2.0J /
cm ^2, was irradiated so as to ^{5.0J / cm 2, 10J / cm} 2, Example 1
A polymer-dispersed liquid crystal oriented in the same manner as in was obtained. (Example 9) A sample is prepared under the same conditions as in Example 1. Light irradiation was also performed using the same light source as in Example 1, and while heating to 80 degrees, the energy of the irradiation polarized light was 0.50 J / cm ² , 2.0 J /
cm ^2, was irradiated so as to ^{5.0J / cm 2, 10J / cm} 2, Example 1
A polymer-dispersed liquid crystal oriented in the same manner as in was obtained.

FIG. 11 shows the change in transmittance of the polymer-dispersed liquid crystal prepared in the example according to the heating temperature and the light irradiation energy during the irradiation of polarized light. It can be seen that the apparent orientation of the liquid crystal is increased by heating, and the transmittance is increased. The highest transmittance was obtained by heating from 70 ° C to 80 ° C. The transmittance increases as the irradiation energy increases, but an energy of 2 J / cm ² or more is sufficient for writing.

[0030]

The polymer-dispersed liquid crystal obtained by mixing and polymerizing a liquid crystal and a monomer or oligomer having a photoresponsive site according to the present invention can be optically written by irradiating polarized light. By irradiating polarized light again, rewriting can be performed.

[Brief description of the drawings]

FIG.

FIG. 2 is a layout diagram showing a positional relationship between a polymer-dispersed liquid crystal and two polarizing plates orthogonal to each other when the liquid crystal is dispersed.

FIG. 3 is a photograph taken.

FIG. 4

FIG. 5 is an absorption spectrum after irradiation with polarized light at an energy of 10 J / cm ² .

FIG.

FIG. 7 shows the result of measuring the transmittance while rotating.

FIG. 8 is a schematic diagram when irradiating a polarized light having a polarization direction of 0 ° with an energy of 10 J / cm ² .

FIG. 9 is a schematic view when irradiating polarized light having a polarization direction of 45 ° with an energy of 10 J / cm ² by changing FIG.

FIG. 10 is an excess rate.

FIG. 11 shows a change in transmittance when the heating temperature during light irradiation is changed.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinya Morino 2-42-5 Nagatsuta-cho, Yokohama-shi, Kanagawa Pref. ) Inventor Akira Kaiho 503-1, 27-9-9 Kameido, Koto-ku, Tokyo

Claims (6)

[Claims] 1. A polymer-dispersed liquid crystal obtained by mixing and polymerizing a liquid crystal and a monomer or oligomer containing a site capable of responding to light, wherein the liquid crystal is oriented by irradiating polarized light. Characteristic polymer dispersed liquid crystal. 2. The method according to claim 1, wherein the monomer or oligomer containing a photoresponsive site is an acrylic monomer, an acrylic acid monomer, a methacrylic acid monomer vinyl monomer, an epoxy monomer or a urethane acrylate, an epoxy acrylate, a polyester acrylate, a polyether acrylate, or a polyester urethane acrylate. The polymer-dispersed liquid crystal according to claim 1, wherein the liquid crystal is at least one kind. 3. The photoresponsive site according to claim 1, wherein the photoresponsive site is at least one of an azobenzene derivative, a stilbene derivative, a spiropyran derivative, an α-aryl-β-keto acid ester derivative, and a chalcone derivative. Polymer dispersed liquid crystal. 4. The polymer-dispersed liquid crystal according to claim 1, wherein the photoresponsive portion is azobenzene. 5. The polymer-dispersed liquid crystal according to claim 1, wherein the orientation of the liquid crystal obtained by irradiating the polarized light is realigned by irradiating the polarized light again. 6. The polymer-dispersed liquid crystal according to claim 1, wherein the polarized light to be applied is visible polarized light.