JP2827324B2 - Method for producing liquid crystal resin composite and liquid crystal optical element using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a liquid crystal resin composite for fixing phase separation between a liquid crystal and a cured resin and a transmission / scattering liquid crystal optical element using the same. Things.

[Prior art] In recent years, a liquid crystal is impregnated in a porous body, or a liquid crystal is encapsulated in a microcapsule, and a liquid crystal optical element is formed using a liquid crystal resin composite in which the liquid crystal is dispersed and held in a resin matrix.
A liquid crystal optical element that controls transmission and scattering by changing the refractive index of the liquid crystal depending on the presence or absence of an electric field and adjusting the relationship with the refractive index of the resin matrix has attracted attention.

Specifically, JLF Fergason et al. Used nematic liquid crystals microencapsulated using polyvinyl alcohol (Japanese Patent Publication No. 58-501631), and KNPearlman et al. Used various latex-incorporated liquid crystals (Japanese Patent Application Laid-Open No. 60-252687).
And JWDoane et al. Make a method of dispersing and hardening a liquid crystal in an epoxy resin (Japanese Patent Publication No. Sho 61-502128).

[Problem to be Solved by the Invention] When a liquid crystal resin composite is used as a liquid crystal optical element, a structure in which liquid crystal is dispersed and held in a resin matrix is required depending on the use. However, in the conventional method of manufacturing a liquid crystal resin composite, it is difficult to freely control the structure of the system, and there has been a problem that a sufficient function as an optical element cannot be exhibited.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and a method of curing a liquid crystal and a resin by photocuring a mixture of a liquid crystal and an uncured photocurable resin. by fixing the phase separation of the object, phase diagram of the liquid crystal in the production process of the liquid crystal polymer composite material to produce a liquid crystal polymer composite material which is dispersed and held in a resin matrix, the liquid crystal volume fraction C _LC in the mixture is a mixture The liquid crystal volume fraction C _{Q at} the intersection Q of the upper compatible-incompatible line and the compatible-liquid crystal deposition line and the following formula (1) are satisfied, and C _Q +0.05 <C _LC <0.75 (1) In a method for producing a liquid crystal resin composite, wherein the temperature at which the mixture is photocured is a temperature at which the mixture substantially exhibits a liquid crystal phase, and in the production method, the liquid crystal has a positive dielectric constant. a nematic liquid crystal having anisotropic, ordinary refractive index of the liquid crystal (n _o) and the resulting resin Ma A method for producing a liquid crystal resin composite, characterized by using a photocurable resin selected so that the refractive index of Trix matches, and in the production methods, a monomer and an oligomer of the photocurable resin are used. A method for producing a liquid crystal resin composite, wherein the ratio is adjusted within a range of 15:85 to 90:10 to obtain a melt, and the liquid crystal resin composite obtained by the production method is used as a pair. An object of the present invention is to provide a liquid crystal optical element sandwiched between substrates with electrodes.

In the present invention, the mixture of the liquid crystal and the uncured photocurable resin is irradiated with light, thereby curing the photocurable resin. By fixing the structure, a liquid crystal resin composite in which liquid crystal is dispersed and held in a resin matrix can be obtained.

In the present invention, in a state where no voltage is applied, the refractive index of the resin matrix by light curing resin is cured by light irradiation, it is to match the ordinary refractive index of the liquid crystal (n _o).

Thus, in the element in which the liquid crystal resin composite of the present invention is sandwiched between a pair of substrates with electrodes, the difference between the refractive index of the unaligned liquid crystal and the refractive index of the resin matrix when no electric field is applied. Due to scattering state (that is, cloudy state)
In addition, when an electric field is applied, the liquid crystal is aligned, and the ordinary state refractive index (n _o ) of the liquid crystal matches the refractive index of the resin matrix obtained by photocuring, thereby indicating a transmission state. It has a reversible transmission-scattering function.

In the present invention, the refractive index of the resin matrix and the ordinary refractive index (n _o ) of the liquid crystal to be used are made to coincide with each other. Should be almost equal to each other so as not to adversely affect the image quality.

As the photocurable resin used in the present invention, a photocurable resin having no compatibility with the liquid crystal after curing can be used. Examples of the photocurable resin include those that have photoreactivity themselves, those that are cured by a substance generated by light irradiation, specifically those that are decomposed and cured by light irradiation, and those that are polymerized and cured. Various known ones can be used.

Above all, a photocurable vinyl resin is preferable. In particular, these monomers and oligomers may be used in combination and set in a desired shape of the phase diagram.

This photo-curable resin may be used alone or in combination of two or more, including a photo-curing initiator, other modifiers necessary for preparing a liquid crystal resin composite, a modifier for the prepared liquid crystal resin composite, and the like. May be. Specifically, a crosslinking agent, a surfactant,
It may contain a diluent, a thickener, an antifoaming agent, an adhesion-imparting agent, a stabilizer, a polymerization accelerator, a chain transfer agent, a polymerization inhibitor and the like.

Examples of the photo-curing initiator include benzoin ether, benzophenone, acetophenone, and thioxanthone.

The liquid crystal used in the present invention includes a nematic liquid crystal, a smectic liquid crystal, and the like, and the composition may be used alone or in an operating temperature range. It can be said that use is more advantageous. In particular, the use of a nematic liquid crystal is preferred.

Further, the liquid crystal substance to be used must be one that does not dissolve or is difficult to dissolve in the resin matrix after light irradiation. When a composition is used, it is desirable that the solubility of each liquid crystal be as close as possible.

When manufacturing the liquid crystal polymer composite material of the present invention, the liquid crystal and the uncured photocurable resin, crystal volume fraction C _LC of the mixture
Is the liquid crystal volume fraction C _{Q at} the intersection Q of the compatible-incompatible line and the compatible-liquid crystal deposition line on the phase diagram and the following equation (1): C _Q +0.05 <C _LC <0.75 (1 Satisfies the relationship of.

This is because, in a liquid crystal resin composite, liquid crystal particles in the order of submicron to micron need to be dispersed and held in a resin matrix, and the more uniform particle size requires a contrast ratio and low voltage driving characteristics. This is because it is necessary for improving the electro-optical characteristics such as the above.

In the present invention, a mixture of an uncured resin and a liquid crystal generally becomes a homogeneously dissolved state (transparent) at a high temperature and becomes a cloudy state or a liquid crystal phase at a low temperature, but the temperature differs depending on its composition. The phase diagram is as shown in the figure.

In FIG. 1, indicates a compatible region (uniformly dissolved state),
Is an incompatible region or a region of a liquid crystal phase, the line A is a compatible-incompatible line, a point where the state changes from a homogeneously dissolved state (transparent solution state) to a cloudy state, and the line B is a compatible-liquid crystal deposition. Line
The figure shows that the liquid crystal starts to precipitate from the homogeneously dissolved state and the liquid crystal and the isotropic liquid start to coexist. The point Q is the intersection of the compatible-incompatible line A and the compatible-liquid crystal deposition line B.

The positional relationship between the lines A and B varies depending on the nematic-isotropic transition point _{TNI of} the liquid crystal, the compatibility between the liquid crystal and the uncured photocurable resin, the molecular weight of the liquid crystal and the uncured photocurable resin, and the like. I do.

The liquid crystal volume fraction C _LC is the volume fraction C _{Q at} point _Q and C _Q +0.0
5 <C _LC <0.75 is satisfied. C _LC ≦ C _Q +0.05
In this case, it is difficult to substantially select the liquid crystal phase and harden the photocurable, and if 0.75 ≦ _CLC , the scattering power of the liquid crystal optical element is undesirably small.

The temperature at the time of photocuring is also an important factor. Specifically, the temperature To (° C.) at which the melt is photocured is such that the mixture is substantially in the liquid crystal phase. That is, a region showing a liquid crystal phase is formed at a temperature lower than the compatibility-liquid crystal deposition line. At a temperature immediately below the compatibility-liquid crystal deposition line, a region where a liquid crystal phase and an isotropic liquid are mixed,
It is difficult for the manufactured liquid crystal optical element to have high scattering-transmission performance. In the present invention, photocuring is performed in a region showing a liquid crystal phase,
In particular, photocuring is preferably performed at a temperature lower by at least 10 ° C. than the temperature of this wire. The lower limit of the temperature may be set to a temperature equal to or higher than the temperature at which no liquid crystal phase is exhibited.

Here, the liquid crystal phase means a mixture in which about 75% or more of the liquid crystal phase has a liquid crystal phase. The larger the ratio of the liquid crystal phase, the more preferable because the scattering property of the liquid crystal optical element increases.

Since this liquid crystal phase usually uses a nematic liquid crystal, it is a nematic liquid crystal phase.

Depending on the ratio of the monomer and oligomer of the photocurable resin, the phase diagram can be greatly changed, so that the ratio of the monomer and oligomer is changed from about 15:85 to 90:10 to obtain the desired electro-optical characteristics. I can do it.

This is because the monomer and the oligomer have different molecular weights and have different compatibility with the liquid crystal, so that by using them together, the phase diagram can be easily changed.

In other words, it is possible to control the compatibility of the mixture in the uncured state, and it is also possible to control the liquid crystal-resin matrix separation structure of the liquid crystal resin composite obtained after curing. .

Since the molecular weight of the oligomer is usually several times or more the molecular weight of the monomer, the compatibility of the oligomer with the liquid crystal is lower than that of the monomer. Therefore, increasing the oligomer / monomer ratio, compatibility of the phase diagram - the critical point P is the peak point of the heterologous溶線moves to (low side of C _LC) left side in the figure. The critical point P may not be clearly observed due to the relative relationship between the line A and the line B.

In the above description, the liquid crystal has been described as forming a completely spherical liquid bubble. However, this may not be completely spherical, and the individual liquid bubbles are not independent and communicate with each other. It may be something. When the liquid crystal forms a substantially spherical liquid bubble, the particle diameter of the liquid crystal indicates the diameter of the liquid crystal, and when the liquid crystal has a porous communication structure, the liquid crystal director has an area having a correlation with each other. Express the diameter.

The liquid crystal resin composite of the present invention is, for example, an In ₂ O ₃ —SnO ₂ (I
A liquid crystal optical element is sandwiched between substrates made of glass, plastic or the like with a transparent electrode such as TO) and SnO ₂ . As a method of manufacturing this liquid crystal optical element, a pair of substrates with electrodes are arranged so as to face each other, the periphery is sealed to form an empty cell, and a mixture of liquid crystal and uncured photocurable resin is injected from an injection port. Then, the injection port is sealed, the light curable resin is cured by light irradiation, and the phase may be separated, or the mixture may be supplied onto one electrode-attached substrate, and the other electrode-attached substrate may be overlaid. Alternatively, phase separation may be performed by irradiating light to cure the photocurable resin.

Although the gap between the substrates can be operated at 5 to 100 μm, it is appropriate to set it to 7 to 40 μm in consideration of the applied voltage and the contrast at the time of ON / OFF.

Since the refractive index of the resin matrix is made to coincide with the ordinary refractive index n _o of the liquid crystal, after the light irradiation becomes opaque state for refractive index scattering by the liquid crystal and the resin matrix that is not arranged. By applying a voltage, the liquid crystal optical element of the present invention prepared in this way is arranged in a liquid crystal state, and is in a transmissive state because the refractive index matches that of the resin matrix.

In the present invention, furthermore, a spacer for controlling a gap such as a pigment or a pigment, glass particles, plastic particles, or ceramic particles is added to the melt, a colored substrate is used as a substrate, or a color filter is laminated. Can also.

In the present invention, a mixture of a liquid crystal substance and an uncured photocurable resin is used, and the photocurable resin is cured by light irradiation. Therefore, there is no need to evaporate a solvent or water which is unnecessary at the time of curing. For this reason, since it can be cured in a closed system, it has high reliability and also has an effect of bonding two substrates with a photocurable resin, so that a sealing material can be eliminated.

By using such a liquid crystal resin composite, even if the area is large, the risk of short-circuiting between the upper and lower transparent electrodes is low, and the alignment and the substrate gap are strict as in a normal twisted nematic display element. Thus, a liquid crystal optical element having a large area can be manufactured with extremely high productivity.

Such a liquid crystal optical element can be used as a display element, and is also suitable as a light control body because it can be easily enlarged to a large area and can be cut into a desired size later.

In this case, a metal lead portion for lowering the resistance may be provided in a part of the electrode, or when used as a light control mirror, one electrode may be used as a reflective electrode.

This liquid crystal optical element may be formed by laminating a reinforcing plate such as plastic or glass for further protection when the substrate is made of plastic or thin glass, or may be made of tempered glass, laminated glass, wire-filled glass, etc. Is applicable.

Use of this liquid crystal optical element, the use of a light control body with a driving means is added to building materials such as windows, skylights, partitions, doors, etc.
There are materials for vehicles such as windows and moon roofs, and materials for cases, doors and lids for various electric appliances.

Further, by using this light control body and combining it with an arrangement means for arranging various objects, it can also be used for an object display such as a show window or a showcase for displaying various products. In this case, there is also an application in which, when used in a showcase, the inside is normally opaque and cannot be seen, but when a voltage is applied to make it transparent, the inside can be seen.

Further, the liquid crystal optical element can be used for a display device for displaying characters and figures. For example, the present invention is suitable for a large-scale public display, and can also be used for a high-density display element in which one of the substrates is an active matrix substrate in which an active element such as a TFT is formed for each pixel.

When applying a voltage to the liquid crystal optical element of the present invention, an AC voltage that changes the alignment of the liquid crystal may be applied.
Specifically, an AC voltage of about 5 to 100 V and about 10 to 1000 Hz may be applied.

When no voltage is applied, the electrodes may be opened or short-circuited. Of course, a low voltage enough to keep the liquid crystal resin composite in a scattering state may be applied. Furthermore, since the voltage-transmittance curve is gentle,
A gray scale display can be performed by applying a medium voltage.

[Action] By irradiating the mixture of the uncured resin and the liquid crystal with light, the resin is cured and the molecular weight is increased.
The compatibility with the liquid crystal is reduced, and the liquid crystal is independently precipitated to form a liquid crystal resin composite in which the liquid crystal is dispersed in a resin matrix.

At this time, the characteristics of the obtained liquid crystal optical element change depending on which point on the phase diagram causes photocuring-phase separation. For this reason, in the present invention, the volume fraction C _LC of the liquid crystal in the mixture is the volume fraction C _LC of the liquid crystal at the intersection Q of the compatible-incompatible line A and the compatible-liquid crystal deposition line B on the phase diagram of the mixture. _Q and
C _Q +0.05 satisfied <C _LC <0.75 the relationship, the mixture temperature photocuring the To (° C.) is, the mixture is to be cured at temperatures substantially exhibits a liquid crystal phase. As a result, a large liquid crystal resin composite having a substantially uniform liquid crystal particle diameter is obtained, and a liquid crystal optical element that can be driven at a low voltage is obtained.

[Examples] Hereinafter, the present invention will be specifically described with reference to examples.

Example 1 A pair of glass substrates with ITO were sealed around the periphery except for the injection port with a gap of 14 μm to form empty cells.

A mixture using 65 parts of "E-8" manufactured by BDH as a liquid crystal, 17.5 parts of ethylhexyl acrylate as an uncured photocurable resin, 17.5 parts of a urethane oligomer, and 0.35 part of "Darocur 1116" manufactured by Merck as a photocuring initiator. Is injected into the empty cell, the injection port is sealed, and ultraviolet light is irradiated at 7 ° C. for 60 seconds to cure the photocurable resin and cause a phase separation between the resin and the liquid crystal. Was sandwiched between substrates with electrodes to produce a liquid crystal optical element. The liquid crystal volume fraction C _{Q at} the point Q of the mixture before photocuring is about 0.55.
And C _LC = C _Q +0.10. The temperature of the compatibility-liquid crystal deposition line at C _LC = 0.65 was 20 ° C., which was 13 ° C. higher than the curing temperature.

The liquid crystal optical element was in a scattering state (white turbid state) at the time of photocuring, and had a transmittance of 18%. When an AC voltage (30 V AC, 50 Hz) was applied between the electrodes, the electrode became transparent, and the transmittance was 84%. This returned to the scattering state when the application of the voltage was stopped, and sufficient scattering-transmission characteristics were obtained.

Example 2 A liquid crystal composition having a liquid crystal nematic-isotropic transition point T _NI of 93 ° C., a refractive index anisotropy of 0.24, and a dielectric anisotropy of 15, instead of the liquid crystal “E-8” of Example 1. Use this liquid crystal composition
60 parts, 20 parts of 2-ethylhexyl acrylate as an uncured photocurable resin, acrylic urethane oligomer 20
Part, "Darocur 111" manufactured by Merck as a photo-curing initiator
6) A mixture using 0.40 parts was injected into the empty cell, the injection port was sealed, and a liquid crystal optical element having excellent scattering-transmission performance was produced in the same manner as in Example 1. The liquid crystal volume fraction C _Q of this system was 0.43.

Example 3 An excellent scattering-transmission performance was obtained in the same manner as in Example 2 except that 10 parts of 2-ethylhexyl acrylate and 10 parts of 2-hydroxyethyl acrylate were used instead of 20 parts of 2-ethylhexyl acrylate of Example 2. A liquid crystal optical element was manufactured.

Comparative Example 1 A liquid crystal optical element was manufactured in the same manner as in Example 1, except that photocuring was performed at 17 ° C.

Since the device was irradiated with light at a temperature around the compatible-liquid crystal deposition line of 20 ° C., the photocuring temperature was too high, and the nematic liquid crystal phase and the isotropic liquid were mixed during photocuring. Although having the transmission performance, only a non-uniform element was obtained.

Comparative Example 2 The amount of the liquid crystal "E-8" in Example 1 was changed to 80 parts, and 10 parts of 2-ethylhexyl acrylate, 10 parts of an acrylic urethane oligomer, and 0.20 part of "Darocur 1116" manufactured by Merck as a photocuring initiator were used. A liquid crystal optical element was manufactured in the same manner as in Example 1, except that the mixture was mixed.

In this device, photocuring was started from the nematic liquid crystal phase, but the resulting device was almost transparent and had low scattering performance because of too much liquid crystal.

[Effects of the Invention] As described above, the present invention provides a method for producing a liquid crystal resin composite, and the liquid crystal and the resin are cured by photocuring a mixture of the liquid crystal and an uncured photocurable resin. by fixing the phase separation of the object, phase diagram of the liquid crystal in the production process of the liquid crystal polymer composite material to produce a liquid crystal polymer composite material which is dispersed and held in a resin matrix, the liquid crystal volume fraction C _LC in the mixture is a mixture The liquid crystal volume fraction C _{Q at} the intersection Q of the upper compatible-incompatible line and the compatible-liquid crystal deposition line and the following formula (1) are satisfied, and C _Q +0.05 <C _LC <0.75 (1) A method for producing a liquid crystal resin composite, wherein the temperature To (° C.) at which the mixture is photocured is a temperature at which the mixture substantially exhibits a liquid crystal phase.

As a result, the liquid crystal and the uncured photocurable resin are cured from the liquid crystal phase state, so that the liquid crystal particle size is substantially uniform, relatively large, and the electro-optical characteristics of scattering-transmission that can be driven at a low voltage are obtained. A good liquid crystal resin composite can be obtained.

Further, by changing the phase diagram, a liquid crystal resin composite having a desired liquid crystal particle size and density can be easily produced. In particular, by changing the ratio between the oligomer and the monomer, this can be easily coped with.

By sandwiching the liquid crystal resin composite between the substrates with electrodes, a transmission-scattering control type liquid crystal optical element can be easily obtained.

The present invention is also applicable to various applications within a range that does not impair the effects of the present invention.

[Brief description of the drawings]

FIG. 1 is a phase diagram of a mixture of a general uncured resin and liquid crystal. A: compatible-incompatible line B: compatible-liquid crystal deposition line P: critical point Q: intersection of line A and line B

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/1333

Claims (4)

(57) [Claims] A liquid crystal in which a liquid crystal is dispersed and held in a resin matrix by fixing a phase separation between the liquid crystal and a cured resin by photocuring a mixture of the liquid crystal and an uncured photocurable resin. In a method for producing a liquid crystal resin composite, the volume fraction C _LC of the liquid crystal in the mixture is determined by adjusting the liquid crystal at the intersection Q between the compatible-incompatible line and the compatible-liquid crystal deposition line on the phase diagram of the mixture. Satisfies the following volume fraction C _Q and the following formula (1), and C _Q +0.05 <C _LC <0.75 (1) The temperature To (° C.) at which the mixture is photocured, the mixture substantially shows a liquid crystal phase. A method for producing a liquid crystal resin composite, characterized by being at a temperature. 2. The method for producing a liquid crystal resin composite according to claim 1, wherein the liquid crystal is a nematic liquid crystal having a positive dielectric anisotropy, and the ordinary refractive index (n _o ) of the liquid crystal and the refraction of the obtained resin matrix. A method for producing a liquid crystal resin composite, characterized by using a photocurable resin selected to have the same ratio. 3. The method for producing a liquid crystal resin composite according to claim 1 or 2, wherein the ratio of the monomer to the oligomer of the photocurable resin is adjusted within a range of 15:85 to 90:10 to obtain a solution. A method for producing a liquid crystal resin composite, comprising: 4. A liquid crystal optical element characterized in that the liquid crystal resin composite obtained by the method for manufacturing a liquid crystal resin composite according to claim 1 is sandwiched between a pair of substrates with electrodes.