JPH11125570A - External force sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an external force sensor that can detect an external force and further maintain the detection state by incorporating a constituent for maintaining the molecular array state of a liquid crystal, into the liquid crystal which is filled between substrates that can be elastically deformed by the external force. SOLUTION: When a substrate 2 that can be elastically deformed by applying an external force is deformed, a liquid crystal composition 4 is deformed in a region corresponding to the deformation of the substrate 2, and the molecular array state of liquid crystal 6 is disturbed, thereby a contrast of the array state of the liquid crystal 6 at the reasion to other region where the external force is not applied is generated, and the external force can be detected. Even after the external force is removed and the deformation of the substrate 2 is recovered, the molecular array state of the liquid crystal 6 in the region is continuously maintained by a second constituent 8. As a result, the molecular array state of the liquid crystal 6 in the region deformed by the external force is distinguished from that of the peripheral liquid crystal 6, even after the external force is eliminated, and the state where the contrast is generated is maintained, and the detection state of the external force is retained. The detection state of the external force can be erased by applying an appropriate electric field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external force sensor, and more particularly, to an external force sensor that senses an external force by deformation of a liquid crystal composition, stores the external force, and can be used repeatedly.

[0002]

2. Description of the Related Art Conventionally, there is pressure-sensitive paper as a device for sensing external force applied to a surface as pressure. In this method, a microcapsule in which a dye is confined is broken by pressure to perform color display. According to the pressure-sensitive paper, the magnitude of the pressure is detected by the density of the color display.

According to the pressure-sensitive paper, the pressure once detected provides a continuous display (meaning that the display state is maintained even after the external force is removed) by coloring. However, it is impossible to recycle pressure-sensitive paper that has been used once and use it repeatedly. In addition, a special device is required for reading the color in order to digitize the amount of pressure obtained by coloring.

[0004]

Therefore, in the present invention,
An object of the present invention is to provide an external force sensor capable of detecting an external force and maintaining the detection state.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors can obtain a liquid crystal composition in which a liquid crystal is mixed with a second component for maintaining a molecular alignment state of the liquid crystal. The present invention has been completed by finding that an external force can be detected and the detection state can be maintained by forming a liquid crystal element using the liquid crystal composition. That is, in the present invention, a liquid crystal containing a pair of substrates, at least one of which is elastically deformable by an external force, and a liquid crystal and a second component for maintaining a molecular alignment state of the liquid crystal filled between the substrates. An external force sensor comprising the composition and was created.

FIG. 1 shows the operation of the external force sensor 1 of the present invention. When the elastically deformable substrate 2 is deformed by applying an external force, the liquid crystal composition 4 is deformed in a region corresponding to the deformation.
Is deformed. Due to this deformation, in this area,
The molecular alignment state of the liquid crystal 6 is disturbed. As a result, a contrast in the alignment state of the liquid crystal is generated between the other regions to which no external force is applied. That is, an external force is detected. Even after the external force is removed and the deformation of the substrate 2 is recovered, the molecular alignment state of the liquid crystal 6 in this region is maintained by the second component 8. As a result, the molecular alignment state of the liquid crystal 6 in the region deformed by the external force is distinguished from the molecular alignment state of the surrounding liquid crystal 6 even after the external force is removed, and the state in which the contrast occurs is maintained. Therefore,
The detection state of the external force is maintained. This external force detection state can be erased by applying an appropriate electric field, aligning the molecular arrangement state of the liquid crystal 6, and eliminating the contrast. In this specification, the external force includes any of externally applied force, pressure, stress, and work. According to this external force sensor, the external force is detected as a disorder of the alignment state of the liquid crystal. Also, this detection state can be kept permanently. Further, this detection state is erased by applying the voltage, and the external force can be detected again.

In this case, the liquid crystal composition comprises a liquid crystal having a positive dielectric anisotropy at any frequency and the following three properties, that is, a state in which the liquid crystal forms a continuous phase or a discontinuous phase. It is preferable to use a second component made of a polymer material having a functional group that is mixed with the liquid crystal and regulates the alignment of the molecules of the liquid crystal.

According to this liquid crystal composition, when a voltage is applied between the substrates at a frequency at which the liquid crystal has a positive dielectric anisotropy, the major axes of the liquid crystal molecules are aligned between the substrates in parallel to the direction of the electric field. A state (hereinafter, such an arrangement state of the liquid crystal molecules is also referred to as an alignment state or a light transmission state) is obtained. In a region where the liquid crystal composition is deformed by an external force via the substrate, the molecular alignment state of the liquid crystal is disturbed and the liquid crystal composition is not aligned (hereinafter, such a liquid crystal molecular alignment state is also referred to as a random alignment state or a light scattering state). ). This disordered molecular arrangement state is restricted from reorienting due to interaction with the functional group of the polymer material. As a result, even after removing the applied external force, in this region,
The random arrangement state is maintained. Therefore, in the deformed area, a random alignment state is maintained, and a state in which a contrast in the alignment state of the liquid crystal occurs between the deformed area and the other aligned state is maintained. Here, again, when a voltage is applied at a frequency at which the liquid crystal has positive dielectric anisotropy, the long axes of the molecules of the liquid crystal are aligned and aligned between the substrates in parallel to the direction of the electric field, and the transparent state is restored. The contrast is erased. That is, the display is deleted. Since this liquid crystal composition constitutes a light scattering type liquid crystal, a bright display is possible, and an external force sensor that does not require an alignment film, a polarizing plate, or the like can be formed.

As the liquid crystal composition, a liquid crystal having a positive dielectric anisotropy at any frequency and flat particles dispersed in the liquid crystal and exhibiting an affinity for molecules of the liquid crystal are described. It is preferred to use components.

According to this liquid crystal composition, when a voltage is applied between the substrates at a frequency at which the liquid crystal has a positive dielectric anisotropy, the major axes of the liquid crystal molecules are aligned and aligned in the direction of the electric field between the substrates. Is obtained. In a region where the liquid crystal composition is deformed by an external force via the substrate, the arrangement state of the liquid crystal molecules and the flat particles is disturbed, and the liquid crystal composition is in a random arrangement state. In the disordered molecular arrangement state, the reorientation is regulated by the affinity of the flat particles in the disordered state. As a result, even after the applied external force is removed, a molecular arrangement state different from the aligned state is maintained in this region. Therefore, in this region, a random alignment state is maintained, and a state in which the contrast of the alignment state of the liquid crystal occurs between the deformed region and another region is maintained. Here, when a voltage is again applied between the substrates at a frequency at which the liquid crystal has a positive dielectric anisotropy, the long axes of the liquid crystal molecules are aligned and aligned between the substrates in parallel to the direction of the electric field, and the alignment state is restored. Then, the contrast is eliminated. That is, the display is deleted. Since this liquid crystal composition can constitute a light scattering type liquid crystal, an external force sensor having the same advantages as the liquid crystal composition described above can be formed.

In the external force sensor according to the present invention, the molecular alignment state of the liquid crystal is changed according to the magnitude of the external force applied to the elastically deformable substrate. That is, the molecular arrangement state of the liquid crystal is changed in a region having a width corresponding to the magnitude of the external force, and the degree of disorder of the molecular arrangement state of the liquid crystal is changed according to the magnitude of the external force. The size of the deformation region of such a liquid crystal composition,
The magnitude of the external force can be quantified by measuring the change in the amount of light transmission, the amount of light reflection, or the change in the capacitance based on the change in the degree of the disorder in the molecular alignment state of the liquid crystal.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. An external force sensor according to the present invention is based on a liquid crystal element including a pair of substrates and a liquid crystal composition filled between the substrates and containing a liquid crystal and a second component for maintaining a molecular alignment state of the liquid crystal. Configuration. The liquid crystal composition used in the present invention is a composition containing a liquid crystal and a second component capable of maintaining a molecular alignment state of the liquid crystal. (Liquid crystal) One type of liquid crystal may be used alone, or a mixture of two or more types of liquid crystal may be used. Generally, it is preferable to use a mixture of two or more liquid crystals in order to obtain a liquid crystal satisfying various properties. The liquid crystal preferably has a positive dielectric anisotropy at any frequency. If the dielectric anisotropy is positive at any frequency, a liquid crystal (dual-frequency driving liquid crystal) having both positive and negative dielectric anisotropy depending on the frequency may be used. This is because the frequency can be selected and used appropriately. In the case of a mixed liquid crystal, even if the mixed liquid crystal includes a liquid crystal having a negative dielectric anisotropy, it is sufficient that the dielectric anisotropy is positive at any frequency in the entire mixed liquid crystal.

The liquid crystal is preferably a nematic liquid crystal or a liquid crystal having a high electric field response characteristic of a difference of erasing a display by applying an electric field, but a cholesteric or smectic liquid crystal has a required electric field response. It can be used as far as shown. Further, although the molecular weight of the liquid crystal molecule is not limited, it is preferable to use a liquid crystal molecule having a high electric field response and a low molecular weight which can set a low threshold voltage for an electric field response for erasing display. The term “low molecular weight” here depends on the chemical structure of liquid crystal molecules, but means, for example, that the molecular weight is 1000 or less. As such a liquid crystal, for example, there are those shown in [Formula 1] to [Formula 58]. In these chemical formulas, n and m are each 1
-17. However, the liquid crystal that can be used in the present invention is not limited to a liquid crystal having a low molecular weight.

[0014]

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[0015]

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[0020]

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[0024]

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[0026]

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[0027]

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[0030]

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[0031]

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[0032]

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[0034]

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[0035]

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[0036]

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[0037]

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[0039]

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[0040]

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[0041]

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[0043]

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[0044]

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[0045]

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[0046]

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[0047]

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[0048]

Embedded image [Wherein, R 1 represents an alkyl group having 1 to 17 carbon atoms, and R 2 represents an alkyl group having 1 to 17 carbon atoms]

[0049]

Embedded image [Wherein, R 3 represents an alkyl group having 1 to 17 carbon atoms, and R 4 represents an alkyl group having 1 to 17 carbon atoms]

[0050]

Embedded image [Wherein, R5 represents an alkyl group having 1 to 17 carbon atoms, and R6 represents an alkyl group having 1 to 17 carbon atoms]

[0051]

Embedded image [Wherein, R 7 represents an alkyl group having 1 to 17 carbon atoms, and R 8 represents an alkyl group having 1 to 17 carbon atoms]

[0052]

Embedded image [Wherein, R 9 represents an alkyl group having 1 to 17 carbon atoms, and R 10 represents an alkyl group having 1 to 17 carbon atoms]

[0053]

Embedded image [Wherein, R11 represents an alkyl group having 1 to 17 carbon atoms, and R12 represents an alkyl group having 1 to 17 carbon atoms]

[0054]

Embedded image [Wherein, R13 represents an alkyl group having 1 to 17 carbon atoms]

[0055]

Embedded image [Wherein, R14 represents an alkyl group having 1 to 17 carbon atoms]

[0056]

Embedded image [Wherein, R15 represents an alkyl group having 1 to 17 carbon atoms]

[0057]

Embedded image [Wherein, R16 represents an alkyl group having 1 to 17 carbon atoms]

[0058]

Embedded image [Wherein, R17 represents an alkyl group having 1 to 17 carbon atoms]

[0059]

Embedded image [Wherein, R18 represents an alkyl group having 1 to 17 carbon atoms]

[0060]

Embedded image [Wherein, R19 represents an alkyl group having 1 to 17 carbon atoms, and R20 represents an alkyl group having 1 to 17 carbon atoms]

[0061]

Embedded image [Wherein, R21 represents an alkyl group having 1 to 17 carbon atoms, and R22 represents an alkyl group having 1 to 17 carbon atoms]

[0062]

Embedded image [Wherein, R23 represents an alkyl group having 1 to 17 carbon atoms, and R24 represents an alkyl group having 1 to 17 carbon atoms]

[0063]

Embedded image [Wherein, R25 represents an alkyl group having 1 to 17 carbon atoms, and R26 represents an alkyl group having 1 to 17 carbon atoms]

[0064]

Embedded image [Wherein, R27 represents an alkyl group having 1 to 17 carbon atoms, and R28 represents an alkyl group having 1 to 17 carbon atoms]

[0065]

Embedded image [Wherein, R29 represents an alkyl group having 1 to 17 carbon atoms, and R30 represents an alkyl group having 1 to 17 carbon atoms]

[0066]

Embedded image [Wherein, R31 represents an alkyl group having 1 to 17 carbon atoms, and R32 represents an alkyl group having 1 to 17 carbon atoms]

[0067]

Embedded image [Wherein, R33 represents an alkyl group having 1 to 17 carbon atoms, and R34 represents an alkyl group having 1 to 17 carbon atoms]

[0068]

Embedded image [Wherein, R35 represents an alkyl group having 1 to 17 carbon atoms, and R36 represents an alkyl group having 1 to 17 carbon atoms]

[0069]

Embedded image [Wherein, R37 represents an alkyl group having 1 to 17 carbon atoms]

[0070]

Embedded image [Wherein, R38 represents an alkyl group having 1 to 17 carbon atoms]

[0071]

Embedded image [Wherein, R39 represents an alkyl group having 1 to 17 carbon atoms]

(Second Component) The second component is a component that can maintain the molecular alignment state of the liquid crystal unless it receives an external stimulus. In addition, the external stimulus mentioned here means deformation due to an electric field, a magnetic field, heat, or stress. In the case of a liquid crystal composition containing such a second component, for example, when an electric field having a frequency at which the dielectric anisotropy is positive is applied, the liquid crystal molecules are aligned in the direction of the electric field to be in an aligned state. The object develops light transmittance. The second component maintains the aligned state that expresses such light transmittance even after the voltage application is stopped. Further, in the liquid crystal composition in the aligned state, in a region where the liquid crystal composition is deformed due to an external force, the molecular alignment state of the liquid crystal is changed to a random alignment state (light scattering state). Second
The components maintain the changed molecular arrangement state, that is, the random arrangement state even after the external force is removed, in a state where no voltage is applied.

Examples of such a second component include a polymer material described below and particles having a flat shape. These second components form a composite with a liquid crystal.

(Liquid-Crystal-Polymer Composite) One of the second components is a transparent one, which is mixed with the liquid crystal in a state where the liquid crystal forms a continuous phase or a discontinuous phase, and controls the orientation of the liquid crystal molecules. It is a polymer material having a group.

It is preferable that the polymer material itself has transparency. This is because, when the external force sensor is formed of a light transmissive liquid crystal cell, the light transmissivity can be improved. When the light transmittance is good, an external force sensor capable of displaying a bright image is formed, or the sensitivity of external force detection by visual or optical means is improved. Also,
When the polymer material is transparent, it is preferable that the refractive index almost coincides with the ordinary light refractive index of the compounded liquid crystal. This polymer material needs to be mixed with the liquid crystal. This is because, in any region of the liquid crystal composition, uniform display can be maintained in response to given deformation. The polymer material is mixed with the liquid crystal in a state where the liquid crystal forms a continuous phase or a discontinuous phase.

In the liquid crystal composition, a state in which the liquid crystal forms a continuous phase means a state in which the polymer material is dispersed in a three-dimensional network, and the liquid crystal is present in continuous voids of the network structure (a so-called PNLC type). ,Furthermore,
An example is a state in which a polymer material in the form of particles or flakes is dispersed in a liquid crystal. In these cases, the size and shape of the void formed by the polymer material can be selected as needed. The size is 0.05μm
10 μm to 10 μm, preferably 0.1 μm to 5 μm, and more preferably 0.5 μm to 5 μm.
The size of the void is approximately equal to the wavelength of visible light, which is most effective for light scattering during display. If the size is too large, the light scattering effect is weakened. If it is too small, transparency at the time of light transmission is impaired, or a high voltage is required to erase the display. As described above, the liquid crystal composition using a polymer material in which a liquid crystal forms a continuous phase can lower the threshold voltage when erasing a display as compared with a liquid crystal composition in which a liquid crystal exists in a discontinuous phase, and This is preferable because the response speed is high.

In the liquid crystal composition, a state in which the liquid crystal forms a discontinuous phase means a state in which a large number of liquid crystal domains completely surrounded by a polymer material are formed. Specifically, a state in which the polymer material has independent vacuoles and the liquid crystals are filled in the vacuoles (so-called PDLC type)
Can be mentioned. In this case, the size and shape of the vacuoles of the polymer material can be selected as necessary, and the size is 0.05 μm to 10 μm, preferably 0.1 μm to 5 μm, and more preferably 0.1 μm to 5 μm. Preferably it is 0.5 μm to 5 μm. It is most effective for light scattering during display that the size of the vacuole is substantially equal to the wavelength of visible light, and the light scattering effect is weakened when it is too large. If it is too small, transparency at the time of light transmission is impaired, or a high voltage is required to erase the display.

In order to form such a composite structure, various known methods for forming a composite of a liquid crystal and a polymer material (a method of microencapsulating a liquid crystal, a method of dissolving a liquid crystal and a polymer in a solvent) are used. E.g., a method of evaporating, a method of cooling a homogeneous liquid mixture of a liquid crystal and a thermoplastic resin melted by heating, and the like). Alternatively, the polymer material in the form of particles or flakes may be simply mixed with the liquid crystal. Preferably, the monomer is polymerized by applying a stimulus such as ultraviolet irradiation or heating to a liquid mixture of a monomer and a liquid crystal that can be polymerized to form a polymer material, and more preferably by polymerization by ultraviolet irradiation. is there. At the time of polymerization, a polymer may be cross-linked by mixing a cross-linking agent. Polymerization can also be carried out by adding an additive such as a photoinitiator, a photosensitizer, a reactive diluent, an organic solvent and the like.

For example, in the case of the monomer polymerization method,
Whether the liquid crystal forms a continuous phase or a discontinuous phase depends on
Although it depends on the combination of the liquid crystal and the type of polymer material (as a raw material, a monomer that forms a polymer), it can be roughly made by selecting the ratio between the liquid crystal and the monomer. Generally, if the proportion of monomer is large, PDL
It is easy to become C type, and if the ratio of monomer is small, PN
Easy to be LC type. The proportion of the polymer material in the liquid crystal-polymer composite is 5 to 95% by weight, preferably 5 to 80% by weight. More preferably, 10-8
0% by weight, more preferably 20 to 80% by weight. If the proportion of the polymer material is too large or too small, the light scattering effect is weakened. If the proportion of the polymer material is too large, a high voltage is required to erase the display.

The polymer material has a functional group capable of regulating the alignment of the liquid crystal molecules so that the molecular alignment state of the liquid crystal can be maintained. More specifically, it is a functional group capable of regulating the alignment of the liquid crystal molecules unless an external stimulus for realigning the liquid crystal molecules is applied. As the form in which the polymer material has such a functional group, the polymer material is composed of a monomer having a functional group, or the functional group forms a part of the polymer material by including such a monomer. This also includes the case where the compound containing the functional group is uniformly mixed with the polymer material.

The functional groups included in the polymer material include:
Hydroxyl group, amide group, amino group, urea group, urethane group,
A functional group such as a carboxylic acid group and a phenol group is preferably used. Further, as a monomer used when a functional group is introduced into a polymer material by polymerizing the monomer, monofunctional having one group such as a double bond or the like which can be polymerized by light or heat, or two monomers The polyfunctional compounds having the above-mentioned properties can be mentioned. Further, the monomer may include one or two of the functional groups.
Two or more functional groups may be the same or different from each other. Specifically, 2-hydroxyethyl (meth) acrylate, 1
-Or 2-hydroxypropyl (meth) acrylate;
1- or 2-hydroxybutyl (meth) acrylate,
1,4-butanediol mono (meth) acrylate,
1,6-hexanediol mono (meth) acrylate,
Glycerol mono (meth) acrylate, 2-aminoethyl (meth) acrylate, (meth) acrylamide,
Monoalkyl (meth) acrylamide, (meth) acrylamide, monoalkyl (meth) acrylamide, (meth) acrylic acid, 4-hydroxybenzyl (meth) acrylate, Kayarad R-167, Kayarad PET-128, Kayarad
R-128H (all the above three products are manufactured by Nippon Kayaku).

The proportion of the monomer having a functional group in the polymer material is 5% by weight to 100% by weight, preferably 20% by weight to 100% by weight, and more preferably 40% by weight to 100% by weight. 100% by weight. If the proportion of the monomer having a functional group is too small, transparency at the time of light transmission may be impaired.

Further, as the copolymerizable monomer and the crosslinking agent,
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth)
Acrylate, hexyl (meth) acrylate, 1,4
-Butane di (meth) acrylate, 1,6-hexyl di (meth) acrylate, polyethylene di (meth) acrylate, polypropylene di (meth) acrylate, Kaya
rad HX-620, Kayrad HX-220, Kayrad R-684, Kayrad
TMPTA, Kayarad GPO-303, Kayarad R-551, Kayarad
R-712 (All seven products are made by Nippon Kayaku.)
Can be mentioned. By adding a cross-linking agent, the mechanical strength of the polymer material can be improved. Examples of the photoinitiator include 2-hydroxy-2-methyl-1-phenoxypropan-1-one, benzyldimethylketal, and the like.

The liquid crystal mixed with such a polymer material is preferably a liquid crystal having a positive dielectric anisotropy at any frequency. With such a liquid crystal, a light-scattering liquid crystal capable of forming a bright display can be formed, and a polarizing plate and an alignment film are not required.

FIG. 2 shows, as an example, an elastically deformable substrate 14, another substrate 16, and a liquid crystal composition.
A liquid crystal 20 whose dielectric anisotropy is positive at any frequency.
1 shows a cross-sectional structure of an external force sensor 12 using a liquid crystal-polymer composite 18 of a polymer material 21 having a network structure such that a liquid crystal forms a continuous phase. In (a), when an electric field having a frequency at which the dielectric anisotropy is positive is applied between the substrates 14 and 16, the liquid crystal 20 is aligned and aligned in parallel with the direction of the electric field, and enters a light transmitting state. This state continues even after the voltage application ends unless an external stimulus is applied. And
Next, when no electric field is applied and an external force is applied to the substrate 14 as shown in (b), the substrate 14 is deformed.
The molecular alignment state of the liquid crystal 20 in the corresponding region is disturbed. As a result, the region is in a light scattering state, and a contrast of the molecular alignment state of the liquid crystal is generated between the region and the region in the light transmitting state. At this time, the reorientation is regulated by the functional group provided in the polymer material 21, and the disordered molecular arrangement state is maintained. After that, even if the deformation of the substrate 14 is recovered, the molecular arrangement of the liquid crystal 20 is maintained in the molecular arrangement state under the action of the external force by the functional group. As a result, the state where the contrast with the region (transparent region) to which no external force is applied is maintained (see (c)). Further, thereafter, when an electric field having a frequency at which the dielectric anisotropy becomes positive is applied between the substrates 14 and 16,
The liquid crystal 20 is oriented along the direction of the electric field, the detection state is erased, and the light transmission state is established (see (a)). In FIG. 2, the liquid crystal-polymer composite in which the liquid crystal forms a continuous phase has been described. However, the liquid crystal-polymer composite in which the liquid crystal forms a discontinuous phase has the same effect.

(Compound of Liquid Crystal-Flat Shaped Particles) The term “flat” of flat shape particles means that the aspect ratio of the particles is larger than a certain level, and efficiently forms liquid crystal domains in the liquid crystal composition. However, in order to maintain the alignment state of the liquid crystal molecules due to the affinity of the particles, it is generally desirable that the aspect ratio is 2 or more, more preferably 5 or more. The shape of the particles is not limited to a plate shape, but may be a rod shape or a needle shape.

The material constituting the flat particles is not limited. The particles are required to have an affinity, but the affinity can also be imparted by material processing. Further, it is not always necessary to be transparent. When the flat particles are particles that undergo an orientation change by an electric field, the orientation change occurs clearly and quickly, thereby increasing the response speed and reducing the time required to erase the input display. The threshold voltage can be reduced.

Preferred examples of the flat particles whose orientation changes by the electric field include layered clay mineral, titanium oxide, alumina white (water-insoluble basic aluminum sulfate), calcium carbonate, flaky zinc oxide, and flaky aluminum powder. , Navy blue, hematite oxide, plate crystals of various ceramics, graphite and the like. Further, organic crystals and metal complexes of organic substances can also be used. It should be noted that particles that do not cause an orientation change by the electric field can be used in the present invention. Examples of particles having little or no electric field response include organic polymers such as polyethylene, polypropylene, and polytetrafluoroethylene.
And particles composed of the same.

On the other hand, in order to keep the response speed of the liquid crystal composition equal to that of the liquid crystal itself, the flat particles interact only with the liquid crystal molecules through the interface and hardly affect the internal viscosity of the liquid crystal. Preferably, it is

In view of the above requirements, the material used as the flat particles is most preferably a layered clay mineral. As the layered clay mineral, natural or synthetic montmorillonite, saponite, mica, hectorite and the like can be used, and montmorillonite is a typical example because it is relatively easily dispersed in liquid crystal. Further, as flat particles, Japanese Patent Application No. 4-360
No. 551 (JP-A-6-200034) is also particularly preferred. here,
The layered organosilicon-based polymer is a crystalline layered polymer composed of a laminate of a tetrahedral sheet having silicon or a metal as a central atom and an octahedral sheet having a metal as a central atom. Is a layered organosilicon polymer characterized in that some or all of the atoms of silicon or metal are bonded to an organic group by a covalent bond. Hereinafter, the term "layered clay mineral or the like" refers to a layered clay mineral and a layered organosilicon polymer.

The particle size of the flat particles (the particle size here means the maximum length of the particles) is from 0.1 to 2.
About 0 μm is appropriate. If the particle size is smaller than this range, liquid crystal domains cannot be effectively formed,
There is a disadvantage that the alignment state cannot be effectively maintained due to the affinity of the particles. If the particle size is larger than this range, when a light modulating material or a device using the same is formed, the non-uniformity of the liquid crystal composition is conspicuous, causing a defect in appearance, and a cell gap of several tens μm as a device. In the case where a cell having the above structure is formed, the orientation may be physically insufficient. A particularly preferred particle size range is 0.2 to 5 μm.
m. It is easy to prepare a layered clay mineral or the like in such an appropriate particle size range.

The flat particles are preferably dispersed at such a density that liquid crystal domains can be effectively formed. On the other hand, it is also not preferable that the density of the flat particles is too high, so that the change in the orientation is restricted. The density that simultaneously responds to these requirements differs according to the type of liquid crystal or the type and size of flat-shaped particles, and it is difficult to uniformly define the density.
It is desirable to disperse 1 to 10 parts by weight of flat particles with respect to 0 parts by weight. This range also applies when the flat particles are a layered clay mineral or the like.

The dispersion state of the flat particles in the liquid crystal is not necessarily required to be a state in which the individual particles are completely dispersed, and even if some to several tens of particles are aggregated, It suffices that the particles having a flat shape as a whole are dispersed to such an extent that the above-mentioned effects and effects are exhibited. For example, layered clay minerals, etc., in a dispersed state in the liquid crystal,
Some of the particles often exist in a state in which dozens of individual particles (unit layers) are superimposed, but the action and effect of sufficiently flat particles are still exerted.

Such particles have an affinity for the liquid crystal in order to maintain the molecular alignment state of the liquid crystal. If the flat particles are made of a material that originally has an affinity for liquid crystal, for example, some organic crystals or metal complexes of organic materials, the particles may be used as they are. However, when the flat particles are made of a material that does not have an affinity for the liquid crystal, such as particles made of an inorganic substance such as a layered clay mineral, etc. Processing is required. As an example of such a treatment, there is generally a treatment for adsorbing or binding an organic substance to the surface of the particle.

In particular, when the flat particles are layered clay minerals, it is effective to carry out ion exchange in order to give them affinity for liquid crystal. That is, since alkali metal ions are present between the layers of the layered clay mineral, the alkali metal ions are exchanged with organic onium ions having affinity for liquid crystal molecules or onium ions having a liquid crystal group (so-called organicization) to form liquid crystals. Affinity.

As the type of the onium ion, one having an excellent affinity for the liquid crystal molecules is preferred, and therefore, the most suitable type is selected according to the type of the liquid crystal molecules to be used. is there. The selection of the organic onium ion has the advantage that the surface properties, electrical and optical properties, dispersibility, response to an electric field, and the like of the layered clay mineral can be variously controlled.

In preparing a composition of liquid crystal and flat particles having affinity for the liquid crystal, it is sufficient to simply mix the two. However, if both are uniformly mixed using a common solvent and then the common solvent is removed by an appropriate means, the mixture is more uniformly mixed. The same can be said for preparing a composition of a liquid crystal and a layered clay mineral or the like.

The liquid crystal mixed with such flat particles is preferably a liquid crystal having a positive dielectric anisotropy at any frequency. With such a liquid crystal,
A light-scattering liquid crystal capable of forming a bright display can be formed, and a polarizing plate and an alignment film are not required.

FIG. 3 shows, as an example, a transparent and elastically deformable substrate 24, another substrate 26, and a liquid crystal 30 whose liquid crystal composition has a positive dielectric anisotropy at any frequency. -Flat particle composite 28 of flat particles 32 having affinity for liquid crystal dispersed in liquid crystal
2 shows a cross-sectional structure of an external force sensor 22 using the same. As shown in (a), when an electric field having a frequency at which the dielectric anisotropy is positive is applied between the substrates 24 and 26, the liquid crystal 30 is aligned and aligned in parallel with the direction of the electric field, and the flat particles 32 In order to have an affinity for the liquid crystal 30, the sheet 12 is arranged in parallel with the direction of the electric field together with the liquid crystal 30, and the sheet 12 is in a light transmitting state. This state continues after the voltage application ends unless an external stimulus is further applied. And then,
As shown in (b), when an external force is applied to the substrate 24 after the application of the electric field is stopped, the substrate 24 is deformed, and the molecular alignment state of the liquid crystal 30 and the alignment state of the flat particles 32 in the corresponding region are disturbed. Only this region is in a light scattering state, and a contrast of a liquid crystal molecular alignment state is generated between the region and the light transmitting state. At this time, realignment of the liquid crystal 30 is regulated by the affinity of the flat particles 32, and the liquid crystal 30 maintains the disordered alignment state with the flat particles 32. Thereafter, even if the deformation of the substrate 24 is recovered, the flat particles 32 and the liquid crystal 3
The arrangement state of 0 is maintained in the arrangement state during the action of the external force.
As a result, the state in which the contrast is generated between the region and the region to which no external force is applied is maintained (see (c)). Thereafter, when an electric field having a frequency at which the dielectric anisotropy becomes positive is applied between the substrates 24 and 26, the liquid crystal 30 and the flat particles 3
2 are oriented along the direction of the electric field and are in a light transmitting state,
The detection state is deleted (see (a)).

(Substrate) At least one of the pair of substrates constituting the external force sensor needs to be elastically deformable. Both may be elastically deformable substrates.
Also, the substrate can be translucent. By making at least one of the substrates light-transmitting, a change in the liquid crystal composition due to an external force can be visually observed. Further, it is possible to optically measure the light scattering intensity and the like in a deformation region of the liquid crystal composition due to an external force. When an elastically deformable and translucent substrate is used, the state of change of the liquid crystal composition due to an external force can be visually observed from the substrate subjected to the external force. Alternatively, the other substrate facing the elastically deformable substrate can be made to transmit light. Then, the state of the change of the liquid crystal composition can be visually observed from the side of the substrate opposite to the external force. Both of the pair of substrates may be translucent and elastically deformable. These combinations are selected according to the external force detection method or the like in the external force sensor. Note that “elastically deformable” means that it is depressed when an external force is applied and can be recovered thereafter.

Examples of the light-transmitting and elastically deformable materials include transparent resin films such as PET films and acrylic films, and rubber films such as polyisoprene. Examples of the transparent and non-elastic body include glass and a transparent resin plate such as a PET plate, an acrylic plate, and a polystyrene plate. Examples of the non-transparent elastically deformable substrate include a crystalline resin film such as polypropylene, polyethylene, and nylon, and a resin or rubber film to which carbon black or the like is added. Further, the reflection efficiency may be increased by vapor-depositing aluminum or the like on these, or applying a metal foil such as an aluminum foil. A hard coat material or the like may be applied to the surface of such an elastically deformable substrate as long as the input is not hindered, in order to prevent damage.

Examples of the transparent electrode include indium tin oxide (ITO). Non-transparent electrodes include common conductive materials such as iron, copper, chromium, gold, silver, and the like. These electrodes can also be used as a substrate. Also, various electrode patterns may be formed.

(Spacer) The gap between the substrates is defined,
In addition, it is preferable to use a spacer in order to support the substrate so that the deformation of the substrate does not extend to a region other than the region where the external force is excessively applied. In particular, when the liquid crystal composition is a liquid crystal-particle composite showing fluidity as a whole, it is necessary to use a predetermined amount of spacer. Examples of the spacer include spherical particles such as polystyrene and glass beads, and a polymer film having predetermined holes. The amount of the beads differs depending on whether a liquid crystal-polymer composite or a liquid crystal-particle composite is used as the liquid crystal composition. In the case of the liquid crystal-polymer composite, the amount is 1 to 500 per 1 mm 2. In the case of a liquid crystal-particle composite, the number is preferably 50 to 500 per 1 mm 2. The size is determined by the cell gap, but is preferably about 2 to 50 μm in consideration of the display contrast in the liquid crystal element. Furthermore, preferably 5
３０30 μm. In the case of a polymer film, it is preferable that the area occupied by the polymer film is 90% or less, and that the structure efficiently supports all parts of the display element. An example of such a structure is a film having a honeycomb structure. The cell size of the honeycomb is 20 to 500
It is preferably about μm. Further, the thickness of the honeycomb cell wall is preferably about 1/5 to 1/100 of the cell size. Of course, the shape of the cell is not limited to the honeycomb, and may be circular or polygonal. The thickness of the film is 2 to 50 μm, as in the case of beads.
The degree is preferred.

(Sealant) The periphery of the liquid crystal element is preferably sealed with a sealant or the like in order to maintain the mechanical strength of the cell and prevent the liquid crystal from being oxidized and degraded. This sheet
The sealing agent is not particularly limited, and a general agent such as an epoxy-based sealing agent can be used.

(External Force Sensor) The external force sensor of the present invention is composed of such a liquid crystal composition and a substrate. The external force sensor according to the present invention receives and detects the external force exerted by the measurement target as it is. The form of the external force sensor of the present invention is not particularly limited as long as the external force can be detected as disturbance of the molecular alignment state of the liquid crystal via the elastically deformable substrate. Any of the amount and position of the applied external force, the presence or absence of the applied external force, and the like may be detected, and two or more of these may be detected simultaneously. Specifically, a pressure sensor that detects the amount of external force, an impact sensor, a weight sensor, a two-dimensional (surface) sensor that two-dimensionally detects the position where the external force has acted, a pressure sensor, and a tactile sensor that detects the presence or absence of external force , A convex sensor or the like.

(Detection of External Force) The external force can be detected as a disorder of the molecular alignment state of the liquid crystal in the deformation region of the liquid crystal composition. Disorder in the molecular alignment state of the liquid crystal can be visually detected when at least one of the substrates is translucent. When at least one of the substrates is translucent,
The change can be detected by measuring the change in the amount of light reflection or the amount of light transmission of the liquid crystal by optical detection means. Furthermore, the change can be detected by measuring the change in the electric capacity of the liquid crystal by the electric detection means.

(Conversion to Quantitative Data) It is possible to obtain the amount of the applied external force according to the size of the region where the liquid crystal composition is deformed by the external force, that is, the region where the molecular alignment state of the liquid crystal is disturbed by the external force. it can. This is because the size of the region where the molecular alignment state of the liquid crystal is disturbed changes according to the applied external force. In addition, in the liquid crystal element or the deformation region,
The amount of applied external force can also be obtained by the amount of change in light scattering intensity, light transmission amount, or light reflection amount. This is because the degree of disorder in the molecular alignment state of the liquid crystal and the size of the deformation region differ depending on the applied external force. It is preferable that the light scattering intensity, the light transmission amount, or the light reflection amount be obtained by converting the light scattering intensity, the light transmission amount, or the light reflection amount into an electric signal (current value) by an optical detection unit such as a photomultiplier. Also,
Various known optical detection means such as electronic copying, imaging by a CCD camera, and reading by a scanner can also be used. Further, the amount of applied external force can be obtained also by the amount of change in the capacitance of the liquid crystal element or the deformation region. The disorder of the liquid crystal molecular alignment state is
This is because it appears as a change in electric capacity. The electric capacity can be measured using various conventionally known means.

(Conversion to Positional Data) When the position of the deformation area can be visually checked, the position of the applied external force can be obtained by performing actual measurement. It is also possible to specify an external force acting portion by running an external force sensor with a light beam such as a laser, measuring the amount of light transmission or light reflection, and converting the amount of light transmission or the like into an electric signal with a photomultiplier. . Even when it is not possible to visually check, for example, an external force acting portion can be specified by forming a matrix XY electrode and measuring the electric capacitance. The same method can be used to simply detect the presence or absence of an external force.

In the external force sensor of the present invention,
By changing the deformation characteristics of the elastically deformable substrate, the characteristics of the liquid crystal composition, the thickness, and the like, the type of external force to be measured, the detection sensitivity of the external force, or the measurable range of the amount of external force can be adjusted. For example, the material and thickness of the elastically deformable substrate, the type of liquid crystal in the liquid crystal composition, the type of the second component, and the amounts thereof, the thickness of the liquid crystal layer, the concentration of the spacer, and the like can be changed.

FIG. 4 illustrates a case where the external force sensor of the present invention is a two-dimensional sensor 40. In this example, the liquid crystal element is formed in a sheet shape, and the surface side that receives an external force is formed of an elastically deformable and transparent substrate. According to the two-dimensional sensor 40, a deformed region is formed in a portion where the external force has acted according to each external force. In the two-dimensional sensor 40, since the deformation area can be visually observed, the magnitude of the external force can be detected from the size of the deformation area and the degree of the light scattering state. In addition, the position where the external force acts can be measured. Furthermore, this 2
If an appropriate capacitance detecting means is provided in the dimensional sensor 40, the magnitude and position of the external force can be detected from the change in the capacitance. Also, as shown in FIG. 5, by using an optical detecting means including a light source 42, a photomultiplier 44, a control unit 46, etc., which can be driven, a change in the amount of light reflection or light transmission can be detected by an electric signal. And the magnitude and position of the external force can be detected.

FIG. 6 illustrates a case where the external force sensor of the present invention is a convex sensor 50. Also in this example, the liquid crystal cell is formed in a sheet shape, and the surface side that receives an external force is formed of a transparent substrate that is elastically deformable. When the measurement target 60 has the protrusion 60a, if the protrusion 60a side is applied to the surface side of the protrusion sensor 50, the molecular alignment state of the liquid crystal in a region corresponding to the protrusion 60a is changed. The disorder of the molecular arrangement state is detected in the same manner as in the two-dimensional sensor 40 illustrated in FIG.

(Erase of Detection State) The detection state of the external force sensor is determined by aligning the molecular arrangement of the liquid crystal in the deformation region of the liquid crystal composition formed by the external force by means capable of changing the molecular arrangement state of the liquid crystal. By
Can be erased. That is, the molecular arrangement state of the liquid crystal in all regions is changed so as to be aligned, or
It can be erased by changing the deformation region from the random arrangement state to the aligned state. When a liquid crystal having a positive dielectric anisotropy is used, by applying an electric field between the substrates at a frequency at which the liquid crystal exhibits a positive dielectric anisotropy, the liquid crystal molecules are aligned in parallel to the direction of the electric field, and the alignment state is obtained. Can be formed. The detection state erasing means may be any means that can change the molecular alignment state of the liquid crystal.
According to such means, in the liquid crystal composition, the state where there is a contrast in the molecular arrangement state of the liquid crystal can be eliminated to form the aligned state. Specifically, the detection state erasing means is achieved by electrodes provided on a pair of substrates, respectively, and means for applying a voltage between the electrodes.

As described above, the present invention can take the following forms. (1) a liquid crystal composition containing a pair of substrates, at least one of which can be elastically deformed by an external force, and a liquid crystal and a second component for maintaining a molecular alignment state of the liquid crystal, filled between the substrates; Wherein the liquid crystal has a positive dielectric anisotropy at any frequency, and the second component has
An external force sensor, wherein the liquid crystal is a polymer material which is mixed with the liquid crystal in a state of forming a continuous phase or a discontinuous phase and has a functional group which regulates the alignment of molecules of the liquid crystal. (2) a liquid crystal composition containing a pair of substrates, at least one of which can be elastically deformed by an external force, and a liquid crystal and a second component for maintaining a molecular alignment state of the liquid crystal, filled between the substrates; Wherein the liquid crystal has a positive dielectric anisotropy at any frequency, and the second component has
An external force sensor comprising flat particles dispersed in the liquid crystal and exhibiting an affinity for the liquid crystal. (3) A pair of substrates, at least one of which is elastically deformable by an external force and at least one of which is translucent, a liquid crystal filled between these substrates, and a second component for maintaining a molecular alignment state of the liquid crystal. A liquid crystal composition comprising: and an external force sensor comprising: (4) a liquid crystal composition containing a pair of substrates, at least one of which can be elastically deformed by an external force, and a liquid crystal and a second component for maintaining a molecular alignment state of the liquid crystal, filled between the substrates; Means for changing the molecular alignment state of the liquid crystal. (5) a liquid crystal composition containing a pair of substrates, at least one of which is elastically deformable by an external force, and a liquid crystal filled between the substrates and a second component for maintaining a molecular alignment state of the liquid crystal; Means for detecting disturbances in the molecular alignment state of the liquid crystal.

[0114]

According to the external force sensor of the present invention, the external force is detected as disturbance of the molecular alignment state of the liquid crystal in the liquid crystal composition, and this detected state is detected by the second component in the liquid crystal composition after the external force is removed. Can also be held.

[0115]

【Example】

(Example 1) 49% by weight of liquid crystal (E70, manufactured by BDH),
2-hydroxyethyl methacrylate (manufactured by Wako Pure Chemical Industries) 3
4% by weight, 15% by weight of a crosslinking agent (R167, manufactured by Nippon Kayaku), and 2% by weight of a photoinitiator (Irgacure184, purchased from Ciba-Geigy) were mixed. This mixture was sandwiched between a PET film with ITO (thickness: 100 μm, translucent) and a glass substrate with ITO (translucent) through a 12 μm spacer, and ultraviolet light (3.5 mW / cm 2) was applied for 180 seconds. Irradiation was performed to form a liquid crystal-polymer composite between the substrates to form a sheet-like liquid crystal cell. As shown in FIG.
A ceramic ball (1.91 g) 80 is dropped from various heights onto the PET film of the external force sensor 70,
The area of the deformation region of the external force sensor 70 was measured. The result is shown in FIG.

As shown in FIG. 8, the impact energy by the ceramic sphere 80 and the size of the deformation region had a linear relationship in the range of 1.5 to 8 gcm. That is, it was found that the impact energy can be measured from the size of the deformation region.

Example 2 A mixture of a liquid crystal, a polymer, a crosslinking agent and a photoinitiator was prepared in the same manner as in Example 1, and this mixture was passed through a 12 μm spacer to form a 100 μm thick ITO. UV light (3.5 mW / c) sandwiched between a PET film (light transmitting) with ITO and a glass substrate (light transmitting) with ITO
m2) was irradiated for 180 seconds to form a liquid crystal-polymer composite between the substrates to produce a sheet-like liquid crystal cell, which was used as an external force sensor 90A. In addition, a liquid crystal cell was prepared in the same manner as the external force sensor 90A, except that the thickness of the PET film with ITO was 125 μm, and used as an external force sensor 90B.

As shown in FIG. 9, a load was applied to the PET film side of the external force sensors 90A and 90B using the tip of a ballpoint pen to form a deformed area, and the light transmittance in the deformed area was measured. The result is shown in FIG. As shown in FIG. 10, when a 100 μm PET film is used as an elastically deformable substrate, the light transmittance decreases as the load increases in the range of 0 to 100 g, and the load is measured from the light transmittance. did it. Also, 125 μm PE
When a T film is used as an elastically deformable substrate,
The light transmittance decreased with increasing load in the range of 0 to 140 g, and the load could be measured from the light transmittance. further,
From these results, it is possible to change the measurement range of the magnitude of the external force by changing the thickness of the elastically deformable substrate, that is, the deformation characteristic of the elastically deformable substrate that transmits the deformation due to the external force to the liquid crystal composition. I knew I could do it.

[Brief description of the drawings]

FIG. 1 is a diagram showing a principle of detecting an external force in an external force sensor of the present invention.

FIG. 2 is a view showing an input display step when a liquid crystal-polymer composite is used as a liquid crystal composition in the present invention.

FIG. 3 is a view showing an input display step when a liquid crystal-flat particle composite is used as a liquid crystal composition in the present invention.

FIG. 4 is a diagram showing an example in which the external force sensor of the present invention is a two-dimensional sensor.

FIG. 5 is a diagram illustrating an example of an optical detection unit for detecting an external force in the two-dimensional sensor.

FIG. 6 is a diagram showing an example in which the external force sensor of the present invention is a convex sensor.

FIG. 7 is a diagram showing a detection state of impact energy in the first embodiment.

FIG. 8 is a graph showing measurement results of Example 1.

FIG. 9 is a diagram illustrating a detection state of a load according to the second embodiment.

FIG. 10 is a view showing measurement results of Example 2.

[Explanation of symbols]

 Reference Signs List 1 external force sensor 2 elastically deformable substrate 4 liquid crystal composition 6 liquid crystal 8 second component

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Arimitsu Usuki 41, Chukumi Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory, Inc. (72) Inventor Kenzo Obata 1 Showa-cho, Kariya City, Aichi Prefecture 1-chome Inside DENSO Corporation

Claims (1)

[Claims] 1. A liquid crystal composition comprising: a pair of substrates at least one of which can be elastically deformed by an external force; and a liquid crystal filled between the substrates and a second component for maintaining a molecular alignment state of the liquid crystal. , And an external force sensor.