JP3087322B2 - Liquid crystal optical element and driving method thereof - Google Patents

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 two-frequency driving liquid crystal optical element and its use, and relates to a display device for displaying characters, figures, etc. Used for light glass, light shutter, etc.

[0002]

2. Description of the Related Art Conventionally, a TN type or STN type liquid crystal display element using a nematic liquid crystal has been put to practical use. However, they have the disadvantage that they require a polarizing plate and are therefore limited in brightness and contrast.

On the other hand, the method of encapsulating a liquid crystal material disclosed in Japanese Patent Publication No. 58-501631 and dispersing it in a polymer has the advantage that light attenuation is small since a polarizing plate is not required. .

The disclosed technique utilizes the fact that the refractive index of the liquid crystal in the capsule changes depending on the presence or absence of an electric field, and sets the refractive index of the encapsulant equal to the refractive index of the liquid crystal under voltage application. Transparent under applied,
When the voltage is removed, an optical element that scatters light and becomes opaque is obtained. As similar elements utilizing the change in the refractive index of the liquid crystal material, a liquid crystal material dispersed in an epoxy resin (Japanese Unexamined Patent Publication (KOKAI) Showa No. 61-502128) and a liquid crystal material dispersed in an ultraviolet curable resin (JP-A-62-2231) No.)
Etc. are known.

[0005]

As described above, the conventional liquid crystal display device has a nematic liquid crystal having a positive dielectric anisotropy dispersed in a polymer substance, a polymer substance dispersed in the liquid crystal, or a three-dimensional network. The rise response time of the liquid crystal can be controlled by the applied voltage, frequency, and the like. However, the fall response time strongly depends on the properties (elasticity and viscosity) of the liquid crystal material when no voltage is simply applied, and it has been difficult to control the fall time.

An object of the present invention is to provide a liquid crystal optical element which can be driven at a high speed by controlling the fall time, and a driving method thereof.

The present invention has been made in order to solve the above-mentioned problem, and has two transparent substrates having an electrode layer or at least one of two transparent substrates, and a control device supported between the two substrates. An optical layer, wherein the light modulating layer is composed of a liquid crystal material and a transparent solid substance, and the liquid crystal material changes the frequency so that the dielectric constant (ε _‖ ) in the major axis direction and the minor axis direction of the liquid crystal molecules are changed. the difference in dielectric constant (ε _⊥) (Δε = ε _||
-Epsilon _⊥) is a liquid crystal material that can take both positive and negative values, the ordinary refractive index (n _o) or the extraordinary refractive index of the refractive index of the transparent solid substance is the liquid crystal material (n _e) or LCD In a liquid crystal optical element selected to match or approach one of the refractive indices (n _LC ) when the material is randomized, the liquid crystal material and the transparent solid material form a layer structure, and the interface is It is a liquid crystal optical element characterized by having irregularities.

Further , the liquid crystal optical element of the present invention has a
Simultaneous application of AC voltages with frequencies with different signs of ε
It is characterized by being driven by

The aforementioned liquid crystal material and transparent solid substance have a layer structure.
When the interface is uneven, the liquid crystal material is also
Or a dispersion-type liquid crystal device in which a transparent solid substance is dispersed.
In all, the shape of the interface between the liquid crystal material and the transparent solid
There is an advantage that control can be performed with high accuracy.

The substrate used in the present invention is a substrate having at least one electrode layer having a transparent layer, and may be made of glass, plastic, metal or the like. The two substrates are set so that the electrodes are on the light control layer side. Spacers used for ordinary liquid crystal optical elements can be used for setting the distance between the substrates, and the distance is desirably about 3 μm to 30 μm.

As the liquid crystal material used in the present invention, by changing the frequency, the difference (Δε = ε ₁₁ ) between the permittivity (ε ₁₁ ) parallel to the orientation vector and the permittivity (ε ₁ ) perpendicular to the orientation vector is obtained.
Any liquid crystal material that can take both positive and negative values for -ε ₁ ) can be used. The liquid crystal material is not particularly limited as long as Δε has both positive and negative values, and any of a nematic liquid crystal, a smectic liquid crystal, and a cholesteric liquid crystal can be used.

[0012]

A liquid crystal material and a transparent solid substance have a layer structure.
For devices having
Rivinyl alcohol, polyvinyl formal, polymeta
Uses various polymer substances such as methyl acrylate and polystyrene
Can be.

The method of driving a liquid crystal optical element according to the present invention is characterized in that a voltage having a frequency different from the rising edge of the liquid crystal molecules in the sign of Δε is applied when the liquid crystal molecules fall.

As the method of manufacturing the liquid crystal optical element of the present invention, the following eight kinds of methods are desirable, but not limited thereto.

As a first method, a polymer substance is dissolved in a good solvent, water and alcohol are added to the solution, and the mixture is cast based on the mixed solution. Then, the solvent is evaporated to form a porous polymer film. Then, there is a method of filling a liquid crystal material there. In this case, examples of the polymer substance used include polymethyl methacrylate, polystyrene, polyimide, polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyurethane, polytetrafluoroethylene, and polyvinyl fluoride. There is no particular limitation as long as a separation structure can be formed. As a solvent for dissolving the polymer substance, it is sufficient that the polymer substance is uniformly dissolved, and examples thereof include tetrahydrofuran, methyl ethyl ketone, ethyl acetate, and chloroform. As the alcohol, a lower alcohol such as methanol or ethanol is desirable. The concentration of the polymer substance in the mixed solution is desirably 2 to 30% by weight.

As a second method, there is a method in which a liquid crystal material is dispersed in an aqueous solution of a polymer substance to obtain an emulsified state, cast on a substrate, evaporate the solvent, and then adhere to another substrate. At this time, the polymer substance used is not particularly limited as long as it is a water-soluble polymer, and examples thereof include polyvinyl alcohol, polyvinyl formal, and polyallylamine. The concentration in the aqueous solution is preferably about 2 to 30% by weight.

As a third method, there is a method in which a solution of a liquid crystal material, a polymer material, and a solvent for dissolving them is cast on a substrate, the solvent is evaporated, and then another substrate is laminated. In this case, examples of the polymer substance used include polymethyl methacrylate, polystyrene, polyimide, polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyurethane, polytetrafluoroethylene, and polyvinyl fluoride. There is no particular limitation as long as it can form a phase separation structure. Examples of the solvent used include tetrahydrofuran, methyl ethyl ketone, ethyl acetate, chloroform and the like, but are not particularly limited as long as the solvent is a common solvent between the liquid crystal and the polymer material.

As a fourth method, 2 having an appropriate interval is used.
In a cell consisting of one substrate, a solution containing a liquid crystal, one or more polymerizable monomers and a suitable initiator, or a liquid crystal, one or more polymerizable monomers and at least one oligomer and a suitable initiator. Inject the contained solution and polymerize with ultraviolet rays or electron beams, or cast the solution onto a substrate, polymerize with ultraviolet rays, electron beams, etc., and then paste it on another substrate or cast the solution on the substrate Then, there is a method of polymerizing with an ultraviolet ray, an electron beam or the like after bonding another substrate. Acrylic monomers such as methyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, and butadiol monoacrylate are used as polymerizable monomers, and urethane acrylate oligomers and epoxy acrylate oligomers are used as polymerizable oligomers. As the initiator, acetophenone type, benzoin type, benzophenone type, and thioxanthone type are preferable, but not limited thereto.

As a fifth method, 2 having an appropriate interval
A method of injecting a mixed solution of a two-component curable resin and a liquid crystal material into a cell composed of two substrates and curing the solution, or casting the solution on a substrate and curing the same, and then bonding another substrate. is there. The two-component curable resin is preferably an epoxy-amine resin or an epoxy-thiol resin, but is not particularly limited as long as it is a two-component curable resin.

As a sixth method, there is a method of impregnating a liquid crystal into a porous transparent solid substance.

Examples of the porous transparent solid substance include a glass filter and a polymer filter. The refractive index of the transparent substance is the ordinary light refractive index (n ₀ ) or the extraordinary light refractive index (n ₀ ) of the liquid crystal material. n _e) or a liquid crystal material is not particularly limited as long as it matches or close to the one of the refractive index in the case of randomly oriented (n _LC).

As a seventh method, there is a method utilizing a change in compatibility between a thermoplastic resin and a liquid crystal material. This is a method in which the liquid crystal material and the thermoplastic resin undergo phase separation during the process of cooling and solidifying the thermoplastic resin from a high temperature region where the thermoplastic resin and the liquid crystal material are compatible with each other, thereby fixing the liquid crystal material. As a thermoplastic resin,
There is no particular limitation as long as the material melts at a temperature lower than the temperature at which the liquid crystal decomposes and degrades, is compatible with the liquid crystal material, and solidifies when cooled, and is incompatible with the liquid crystal material. For example, epoxy resin, polystyrene, or the like can be used.

As an eighth method, there is a method in which the light control layer is composed of a transparent solid substance 5 having irregularities on the surface and a liquid crystal material 4 as shown in FIG. In this method, the surface of a transparent solid material is mechanically cut or pressed by a mechanical method such as pressing, a process using a laser beam, a method using a photoreaction such as that used for a photoresist, a chemical method such as elution with a solvent, or unevenness. Is formed by a method such as copying a portion having a pattern with a replica or the like, and is sandwiched together with a liquid crystal material on a substrate.

As a method of applying a voltage to the liquid crystal device manufactured in this manner, alternating voltages of frequencies having different signs of Δε of the liquid crystal are alternately applied or simultaneously.
Any of the methods of applying may be used. The voltage can take any value, and may be the same or different.

[0026]

EXAMPLE In this example, a low-frequency AC voltage in which △ ε of the liquid crystal material is positive and a low-frequency AC voltage in which 負 ε is negative are alternately applied, and the rise and fall response times or The transmittance was measured. By applying a low-frequency voltage, the time until the light transmittance reaches 90% is defined as a rising response time, and by applying a high-frequency voltage, the time during which the light transmittance decreases to 10% is reduced. Response time. FIG. 1 is a cross-sectional view of the liquid crystal device used in this embodiment, FIG. 2A shows an applied voltage waveform, and FIG. 2B shows an optical response waveform.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

Example 1 One part of a polymerizable monomer, 2-ethylhexyl acrylate, two parts of a polymerizable oligomer UN9000 PEP (manufactured by Negami Kogyo Co., Ltd.) and a two-frequency driven liquid crystal NR-1012XX
A mixed solution of 6 parts [manufactured by Chisso Corporation] and an appropriate amount of a polymerization initiator diethoxyacetophenone was injected into a liquid crystal cell having a gap of 10 μm. The liquid crystal cell was kept at 25 ° C. and irradiated with ultraviolet rays to be polymerized. The size of the liquid crystal droplet in the obtained film is 1
２2 μm. The rise response time of this liquid crystal device was 3 milliseconds at an applied voltage of 10 ³ Hz and 20 V, and the fall response time was 3 milliseconds at an applied voltage of 3 × 10 ⁴ Hz and 20 V. Example 2 Polymerization A mixed solution of 1 part of a monomer butyl acrylate, 2 parts of a polymerizable oligomer M6200 [manufactured by Toa Gosei Co., Ltd.], 6 parts of a two-frequency drive liquid crystal NR-1013XX [manufactured by Chisso Corporation], and an appropriate amount of a polymerization initiator diethoxyacetophenone. Was injected into a liquid crystal cell having a gap of 10 μm. The liquid crystal cell was kept at 60 ° C. and irradiated with ultraviolet rays to be polymerized. The size of the liquid crystal droplet in the obtained film was 1-2 μm. The rise response time of this liquid crystal device is 10 ² Hz, 20
2 milliseconds at an applied voltage of V and a fall response time of 10
Example 3 3 parts of poly (methyl methacrylate) was added to tetrahydrofuran 90 at ⁵ Hz and an applied voltage of 20 V.
After dissolving in the part, the two-frequency drive liquid crystal NR-1013XX
6 parts (manufactured by Chisso Petrochemical Co., Ltd.) were mixed, cast on a substrate by a dip coating method, and dried at 50 ° C. under reduced pressure for 4 hours. The obtained cast film had a thickness of 15 μm and the size of liquid crystal droplets was 1 to 3 μm. Another substrate was laminated on the cast film to form a liquid crystal device.

The rising response speed is 10 ² Hz, 50
5 milliseconds at an applied voltage of V and a fall response speed of 10
⁵ milliseconds at an applied voltage of ⁵ Hz and 50 V.

Example 4 One part of polymethyl methyl methacrylate beads having a diameter of 1 μm was dispersed in one part of a two-frequency driving liquid crystal NR-1013XX [manufactured by Chisso Petrochemical Co., Ltd.], and the suspension was filled with a gap of 10 μm. Was injected into the liquid crystal cell. The rising response speed of this liquid crystal device is 13 milliseconds at an applied voltage of 10 ² Hz and 60 V, and the rising response speed is 10 ⁵ H
z, 15 milliseconds at an applied voltage of 60V.

Example 5 10 parts of polymethyl methacrylate was added to tetrahydrofuran 1
The resulting solution was cast on a substrate by a dip coating method, and dried at 80 ° C. under reduced pressure for 8 hours. The obtained cast film had a thickness of 15 μm and the size of pores was 1 to 3 μm. A two-frequency driving liquid crystal NR-10 was applied to this cast film at 80 ° C. under reduced pressure.
Filled with 12XX [manufactured by Chisso Petrochemical Co., Ltd.]. Another substrate was laminated on the cast film to form a liquid crystal device.

The rising response speed of this liquid crystal device is 15 milliseconds at an applied voltage of 10 ² Hz and 50 V, and the falling response speed is 1 at an applied voltage of 10 ⁵ Hz and 50 V.
5 ms.

Comparative Example 1 A liquid crystal device was obtained in the same manner as in Example 1, and the fall response time was measured without applying a voltage. 10 ² Hz,
Fall response time 18 after removing the applied voltage of 50V 18
Milliseconds.

Comparative Example 2 A liquid crystal device was obtained in the same manner as in Example 1 except that E-8 (manufactured by BDH) was used as the liquid crystal, and the fall response time was measured without applying a voltage. The speed was measured. The rise response speed was 4 ms, while the fall response time was 25 ms.

Example 6 A release agent was thinly applied on a Fresnel lens, and 1 part of a polymerizable monomer, 2-ethylhexyl acrylate, and a polymerizable oligomer PE-9000 [manufactured by Negami Kogyo Co., Ltd.] 1
Then, the mixture was placed on a glass substrate with ITO, and the mixture was cured by irradiating ultraviolet rays for 1 minute. When the glass substrate is separated from the Fresnel lens, the polymer adheres to the substrate side. It was a transparent solid that captured the regular irregularities of the Fresnel lens. The concavities and convexities of the obtained transparent solid material form a part of a smooth group in which the distance between adjacent rings is 100 μm.
The inclination of the plane part of 0 μm was about 30 °. A two-frequency driving liquid crystal NR-1013XX (manufactured by Chisso Corporation) was dropped on the obtained transparent solid, and another glass substrate with ITO was mounted thereon and fixed. 150 with cell gap spacer
μm. When an AC voltage of 100 Hz and 50 V was applied to the device, the spot of the laser beam moved about 2 ° in 300 ms. When the voltage was not applied, the spot of the laser beam returned to the initial position in 2 seconds. Similarly 100H
After moving the spot by applying a voltage of z, 50V,
When an AC voltage of 10 ⁴ Hz and 50 V was applied for 100 ms, the device returned to the initial position in 300 ms.

The driving principle of this device will be briefly described.
In this embodiment, when no voltage is applied or when 50V10 ⁴ H
Since the refractive index of the liquid crystal when a high frequency such as z is applied is equal to the refractive index of the transparent solid material, the incident light travels straight without being refracted at these interfaces. On the other hand, 50 V, 100
When a low frequency of about Hz is applied, the refractive index of the liquid crystal is different from the refractive index of the transparent solid material, so that the incident light is refracted at these interfaces. This causes the spot of the laser light to move as described above.

[0037]

As described above, the present invention is a transmission / scattering type liquid crystal device driven by two frequencies, and can be driven much faster than a conventional liquid crystal device with a fall response time of 1 to 3 milliseconds. is there. It is also possible to change the response time by changing the frequency. It is also possible to change the response time by changing the frequency.

[Brief description of the drawings]

FIG. 1 shows a cross-sectional view of a liquid crystal optical element according to the present invention.

FIG. 2 shows a waveform diagram of a low-frequency and high-frequency short-wave AC voltage alternately applied to the liquid crystal optical element according to the present invention and a graph of time-light transmittance of the liquid crystal optical element.

FIG. 3 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

1 substrate 2 electrode layer 3 dimming layer 4 liquid crystal material 5 transparent solid substance

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-96629 (JP, A) JP-A-63-50819 (JP, A) JP-A-62-502780 (JP, A) JP-A-81 501342 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1334 G02F 1/133 555

Claims (3)

(57) [Claims] 1. A liquid crystal material comprising: two transparent substrates having electrode layers; and a dimming layer supported between the substrates, wherein the dimming layer comprises a liquid crystal material and a transparent solid substance; However, by changing the frequency, the difference (Δε = ε _‖ −ε _⊥ ) between the dielectric constant (ε _‖ ) in the major axis direction and the dielectric constant (ε _⊥ ) in the minor axis direction of the liquid crystal molecules becomes both positive and negative. a liquid crystal material that can take, the ordinary refractive index (n _o) or the extraordinary refractive index of the refractive index of the transparent solid substance is the liquid crystal material (n
_e ) or the index of refraction (n _LC ) when the liquid crystal material is randomized, is selected to be equal to or close to either, and the liquid crystal material and the transparent solid substance form a layered structure, and the interface thereof is A liquid crystal optical element having irregularities. 2. The method of driving a liquid crystal optical element according to claim 1 , wherein alternating voltages having frequencies having different signs of Δε of the liquid crystal are alternately or simultaneously applied. 3. At least one having an electrode layer has two transparent substrates, and a dimming layer supported between the substrates, wherein the dimming layer comprises a liquid crystal material and a transparent solid substance; The liquid crystal material, by changing the frequency,
A liquid crystal material in which the difference (Δε = ε _‖ −ε _⊥ ) between the dielectric constant (ε _‖ ) in the major axis direction and the dielectric constant (ε _⊥ ) in the minor axis direction can take both positive and negative values, It matches any of the ordinary refractive index of the refractive index of the liquid crystal material of the transparent solid material (n _o) or the extraordinary refractive index (n _e) or refractive index when the liquid crystal material becomes a random (n _LC) or In a liquid crystal optical element selected to be close, the Δε
A liquid crystal optical element, wherein AC voltages having different frequencies are simultaneously applied.