JP2000310780A - Manufacture of liquid crystal film, liquid crystal film and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a large area, to be light in weight and to manufacture at a low cost with respect to a liquid crystal film, of which the direction of the helical axis of the smectic liquid crystal phase with a helical structure is fixed so as to be nearly vertical to the substrate surface, and an optical element containing the film. SOLUTION: The method for manufacturing the liquid crystal film comprises a step to extend a liquid crystal material exhibiting a smectic liquid crystal phase with a helical structure between two plastic substrates with <=50 dyn/cm critical surface tension, a step to align the extended liquid crystal material so as to keep the direction of the helical axis nearly vertical to the film surface in the smectic liquid crystal phase with the helical structure and a step to fix the alignment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a liquid crystal film, a liquid crystal film and an optical element.

[0002]

2. Description of the Related Art Liquid crystals are an intermediate phase (mesophase) having properties of both liquid and crystal, and are characterized by having both fluidity as a liquid and anisotropy as a crystal. is there. Various substances such as so-called low-molecular liquid crystal substances and high-molecular liquid crystal substances are known as substances capable of exhibiting a liquid crystal state (hereinafter, referred to as “liquid crystal substance”). Since it has an orientational order, it can be applied to various uses by utilizing or controlling its molecular orientation, and has formed a large industrial field.

[0003] Liquid crystals are roughly classified into nematic liquid crystals, smectic liquid crystals, discotic liquid crystals, and the like according to their molecular shapes and molecular arrangements. Among these, a smectic liquid crystal is a liquid crystal having a layered structure in which a liquid crystal material such as a rod-like molecule is also referred to as a one-dimensional crystal or a two-dimensional liquid. The smectic liquid crystal has a smectic A phase (SmA phase), a smectic B phase (SmB phase), and a smectic C phase (SmC phase) due to the order in the layer structure.
Phase), smectic E phase (SmE), smectic F phase (SmF phase), smectic G phase (SmG phase), smectic H phase (SmH phase), smectic I phase (SmI phase)
Phase), smectic J phase (SmJ phase), smectic K
Phase (SmK phase), smectic L phase (SmL phase) and the like. In some of these smectic phases, the orientation vector of each layer in the phase is slightly twisted at a certain angle, and as a whole, the orientation vector exhibits a certain helical structure.

[0004] Smectic liquid crystals having a helical structure have various properties, in particular, exhibit various optical properties such as birefringence, optical rotation, polarization separation properties, diffraction properties, and selective reflection properties. It is expected to be applied to the optical field.

For example, Jpn. J. Appl. Phys. 21, L627
As described on page (1982), a low molecular weight chiral smectic liquid crystal substance is sealed in a liquid crystal cell made of two glass substrates, and the liquid crystal cell is oriented while applying an electric field, a magnetic field, or the like. It is known that a spiral structure is formed so that the light is substantially perpendicular to the substrate surface, and exhibits selective reflection characteristics with respect to light incident parallel to the spiral axis. At this time, when the liquid crystal material has a right-handed helical structure, right circularly polarized light of a certain wavelength determined by half the helical pitch (half pitch) is completely reflected, and the left circular The polarized light passes through as it is. This is a phenomenon similar to the selective reflection observed in the cholesteric liquid crystal. For light incident obliquely with respect to the helical axis, it exhibits properties specific to the smectic phase. For example, in the chiral smectic C phase, in addition to the selective reflection corresponding to the half pitch of the spiral, the selective reflection corresponding to the full pitch is also observed. Observed. This is a phenomenon that cannot be seen in the selective reflection of the cholesteric liquid crystal. On the other hand, chiral smectic C exhibiting antiferroelectricity
_As in the cholesteric liquid crystal, only selective reflection corresponding to the half pitch is observed in the _A phase.

When the helical structure is formed such that the helical axis is substantially perpendicular to the substrate as described above, an optical element utilizing the selective reflection characteristic peculiar to the smectic liquid crystal can be manufactured. However, in the case of a device in which a low-molecular-weight chiral smectic liquid crystal substance is sealed and aligned in a liquid crystal cell made of two glass substrates as described above, the helical pitch of the chiral smectic liquid crystal is easily affected by temperature, so that it is stable. It is also difficult to obtain a large-area and lightweight optical element at a low cost because the properties cannot be obtained. Therefore,
Unless the orientation is fixed by some method and the helical pitch is not changed, it cannot be used as a device having stable properties.

Therefore, a device in which a helical axis direction of a smectic liquid crystal phase having a helical structure is fixed so as to be substantially perpendicular to the substrate surface and which can be manufactured at a low cost with a large area and a light weight. A method is needed.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal film having a helical structure, in which a helical axis direction of a smectic liquid crystal phase is substantially perpendicular to a substrate surface, and has a large area. An object of the present invention is to provide a manufacturing method capable of manufacturing a light-weight product at low cost.

Another object of the present invention is to provide a liquid crystal film in which the helical axis direction of a smectic liquid crystal phase having a helical structure is fixed so as to be substantially perpendicular to the substrate surface. Another object of the present invention is to provide a liquid crystal film which is lightweight and can be manufactured at low cost, and an optical element including the film.

[0010]

According to the present invention, there is provided a liquid crystal material exhibiting a smectic liquid crystal phase having a helical structure,
Developing a liquid crystal material between two plastic substrates having a critical surface tension of 50 dyne / cm or less, and applying the developed liquid crystal material to a smectic liquid crystal phase having a helical structure such that a helical axis orientation is substantially perpendicular to a film surface. And a step of fixing the alignment.

Further, according to the present invention, there is provided the method for producing a liquid crystal film, wherein the plastic substrate is a substrate that has not been subjected to an alignment treatment.

Furthermore, according to the present invention, the step of aligning is performed at a temperature equal to or higher than the glass transition temperature of the liquid crystal material, and the step of fixing the alignment is performed by cooling the aligned liquid crystal material to form a glass. A method for producing the liquid crystal film is provided, which comprises a step of setting a state.

Further, according to the present invention, there is provided the method of manufacturing a liquid crystal film, wherein the step of fixing the alignment includes a step of polymerizing the aligned liquid crystal material while maintaining the alignment. Provided.

Further, according to the present invention, there is provided a liquid crystal film produced by the above method.

Further, according to the present invention, there is provided an optical element including at least the liquid crystal film produced by the above method.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method for producing a liquid crystal film of the present invention, a liquid crystal material exhibiting a smectic liquid crystal phase having a helical structure is used.

The smectic liquid crystal phase is a liquid crystal phase having a layer structure in which molecules constituting the liquid crystal phase are also called one-dimensional crystals or two-dimensional liquids. Examples of the smectic liquid crystal phase include a smectic A phase and a smectic B phase.
Phase, smectic C phase, smectic E phase, smectic F phase, smectic G phase, smectic H phase, smectic I phase, smectic J phase, smectic K phase, smectic L phase, and the like. Smectic I phase, smectic F
A phase in which rod-like molecules such as a phase, a smectic J phase, a smectic G phase, a smectic K phase, and a smectic H phase are inclined with respect to a layer normal direction of a liquid crystal phase is preferable.

Also, among the smectic liquid crystal phases such as the above various ones, chiral smectic C phase (SmC * phase),
Chiral smectic I phase (SmI * phase) or chiral smectic F phase (SmF * phase) show the shown ferroelectric optical activity, such as, or chiral smectic C _A phase (Sm
C _A * phase), chiral smectic I _A phase (SmI _A * phase),
Or chiral smectic F _A phase (SmF _A * phase) or the like, which exhibits optical activity and exhibits antiferroelectricity, or chiral smectic Cγ phase (SmCγ phase), chiral smectic Iγ phase (SmIγ phase), chiral smectic Fγ phase ( SmFγ
Various chiral smectic phases such as those exhibiting ferrielectricity and exhibiting optical activity such as phase) are particularly preferable as the smectic phase having a helical structure. However, being chiral is not a requirement, for example, J. Mater. Chem.
6, p. 1231 (1996) and J. Mater. Chem. 7, 1307 (1997), etc., may be an achiral smectic phase having a helical structure.

Among the above-mentioned various smectic phases, the most preferable one is from the viewpoint of the stability of the helical structure, the easiness of the change of the helical pitch, the ease of synthesis, and the ease of orientation due to low viscosity. Is chiral smectic C
Phase or a chiral smectic C _A phase.

The helical structure means that the arrangement of molecules constituting the liquid crystal phase changes little by little in each layer, and that the overall arrangement forms a structure in which the arrangement of molecules is rotated. Examples of the change in the arrangement of the molecules include a structure in which the inclination direction of the molecules in the major axis direction with respect to the normal direction of the layer in the smectic liquid crystal phase is gradually rotated in adjacent layers.

The central axis of the helix in the helix structure is called a helix axis, and the distance in the helix axis direction for one helix rotation is called a helix pitch.

The helical pitch is not particularly limited, but is preferably from 0.2 to 20 μm, more preferably from 0.3 to 10 μm. Further, the helical pitch may be constant in the film, but may be different depending on the location in the film, or may change continuously. The helical pitch is a known method such as adjusting the alignment conditions such as temperature or the like, adjusting the optical purity of the optically active site, adjusting the blending ratio of the optically active substance, etc. It can be easily adjusted by the method.

The liquid crystal material is not particularly limited as long as it has a smectic liquid crystal phase having the helical structure in a phase series and can fix its orientation. For example, various low-molecular liquid crystal substances, high-molecular liquid crystal substances, or mixtures thereof can be used. The liquid crystal material referred to in the present invention may be any one as long as the composition finally obtained exhibits desired liquid crystallinity, and may be used alone or in combination with a plurality of low-molecular and / or high-molecular liquid crystal substances. A composition comprising a molecule and / or a polymer non-liquid crystalline substance may be used. In the liquid crystal material, for example, a surfactant, a polymerization initiator, a polymerization inhibitor, a sensitizer, a stabilizer, a catalyst, a dye, a pigment, an ultraviolet absorber, and an infrared absorber within a range that does not impair the effects of the present invention. And various additives such as an adhesion improver. The content ratio of the liquid crystal substance in the liquid crystal material can be usually 30 to 100% by weight, preferably 50 to 100% by weight, and more preferably 70 to 100% by weight.

The low-molecular liquid crystal substance includes Schiff base compounds, biphenyl compounds, terphenyl compounds, ester compounds, thioester compounds, stilbene compounds, tolan compounds, azoxy compounds, azo compounds, phenyl compounds. A cyclohexane compound, a pyrimidine compound, a cyclohexylcyclohexane compound, a composition thereof, or the like can be used.

As the polymer liquid crystal material, various kinds of main-chain polymer liquid crystal materials, side-chain polymer liquid crystal materials, compositions thereof, and the like can be used.

The main chain type polymer liquid crystal material includes polyester, polyamide, polycarbonate, polyimide, polyurethane, polybenzimidazole, polybenzoxazole, polybenzthiazole, polyazomethine, and polyesteramide. System, polyester carbonate system, polyester imide system, etc., or a composition thereof. As the main-chain type polymer liquid crystal material, a semi-aromatic polyester-based polymer liquid crystal material in which mesogenic groups providing liquid crystallinity and bent chains of polymethylene, polyethylene oxide, polysiloxane and the like are alternately bonded, in particular, Non-all aromatic polyester polymer liquid crystal materials are preferred.

The side chain type polymer liquid crystal material includes:
Polyacrylate-based, polymethacrylate-based, polyvinyl-based, polysiloxane-based, polyether-based, polymalonate-based, polyester-based substances having a skeleton chain of a linear or cyclic structure, such as a mesogen group bonded as a side chain, Or these compositions are mentioned. As the side-chain type polymer liquid crystal substance, a substance in which a mesogen group providing liquid crystallinity is bonded to a skeleton chain via a spacer formed of a bent chain is preferable. Further, those having a molecular structure having a mesogen in both the main chain and the side chain are also preferable.

As the liquid crystal material, a mixture of a low-molecular liquid crystal substance and / or a high-molecular liquid crystal substance as described above mixed with a chiral agent or introduced with an optically active unit exhibits a smectic liquid crystal phase having a desired helical structure. Is preferred. For example, a chiral agent is added to a liquid crystal material exhibiting a smectic C phase, a smectic I phase, a smectic F phase, or the like, or an optically active unit is introduced into the liquid crystal material to obtain a chiral smectic C phase, a chiral smectic I phase, a chiral smectic phase. A liquid crystal substance which can exhibit a chiral smectic phase which easily exhibits a helical structure such as a smectic F phase can be obtained. The helical pitch can be adjusted by appropriately adjusting the compounding amount of such a chiral agent, the amount of the optically active unit introduced, the optical purity, the temperature conditions for orientation, and the like, and further, the properties of the film, for example, selection When used as a reflective element, the selective reflection wavelength can be adjusted.

Whether the helical structure becomes a right helix or a left helix depends on the chirality of the chiral agent or the optically active unit used. Any structure can be manufactured.

In the method for producing a liquid crystal film according to the present invention, the liquid crystal material may be formed on a plastic substrate 2 having a specific critical surface tension.
A step of spreading the liquid crystal material between the sheets.

The critical surface tension can be measured by the method of WAZisman.

In the present invention, the critical surface tension of the plastic substrate refers to a critical surface tension of a surface of the plastic substrate that is in contact with the liquid crystal material during development. Therefore, the critical surface tension at the interface opposite to the side in contact with the liquid crystal material is not particularly limited.

The critical surface tension of the plastic substrate is:
It is 50 dyne / cm or less, and preferably 40 dyne / cm or less. When the critical surface tension of the plastic substrate exceeds 50 dyne / cm, the helical axis direction may not be substantially vertical.

The plastic substrate is not particularly limited, but may be polyimide, polyamideimide, polyamide, polyetherimide, polyetheretherketone, polyetherketone, polyketonesulfide, polyethersulfone, polysulfone, polyphenylenesulfide, polyphenyleneoxide, or the like. Cellulose plastics such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, methacrylic resin, polyvinyl alcohol, polyethylene, polypropylene, poly-4-methylpentene-1 resin, triacetyl cellulose, etc. , Epoxy resin, phenolic resin, polymer liquid crystal, etc. plastic film substrate, on the above substrate Other coatings, for example, a polyimide film, polyamide film, polyvinyl alcohol film, or those having a thin silicone membrane, a silane coupling agent, a metal complex such as chromium, lecithin and CTAB (cetyltrimeth
ylammonium bromide) and other plastic substrates that have been subjected to a physical or chemical surface treatment and have a critical surface tension of 50 dyne / c.
m or less. The two plastic substrates for development have a critical surface tension of 50.
As long as the film is dyne / cm or less, a combination of the same type of plastic substrates or a combination of different types of plastic substrates may be used.

It is preferable that these plastic substrates are not subjected to an alignment treatment represented by rubbing or the like in order to make the helical axis direction substantially perpendicular to the film surface. When an alignment treatment such as a parallel alignment treatment is performed by rubbing or the like, the helical axis orientation may be substantially parallel or oblique to the film surface, which is not preferable as the method for producing the liquid crystal film of the present invention.

The method for developing the liquid crystal material between the two plastic substrates is not particularly limited. Specifically, for example, the liquid crystal material is developed by holding the liquid crystal material between two plastic substrates. can do. More specifically, after the liquid crystal material is applied on at least one of the plastic substrates, the other substrate can be bonded and developed on the liquid crystal material so that air bubbles, wrinkles, and the like do not enter. At this time, when two rolls are used and bonded while passing between the rolls while applying pressure, air bubbles and the like are less likely to enter and the bonding can be performed neatly. Alternatively, a roll having a heating function may be used, and an orientation treatment or the like described later may be simultaneously performed.

As a method of applying the liquid crystal material on the plastic substrate, the liquid crystal material may be directly applied without using a solvent, or the liquid crystal material may be dissolved in an appropriate solvent to form a solution. After applying the liquid crystal material described above, the solvent may be evaporated to apply.

As the solvent, the type of the liquid crystal material,
Appropriate ones can be selected according to the composition and the like, but usually, halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene, phenol, Phenols such as parachlorophenol, benzene, toluene, xylene, methoxybenzene, 1,2
-Aromatic hydrocarbons such as dimethoxybenzene, alcohols such as isopropyl alcohol and tert-butyl alcohol, glycols such as glycerin, ethylene glycol and triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, ethyl cellosolve and butyl Glycol ethers such as Cellsolve, acetone, methyl ethyl ketone, ethyl acetate, 2-pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, butyronitrile, carbon disulfide, And a mixed solvent thereof.

A surfactant may be added to the solvent, if necessary, for adjusting the surface tension of the solution and improving the coatability.

The concentration of the liquid crystal material in the solution can be appropriately adjusted depending on the type and solubility of the liquid crystal material to be used, the thickness of the film to be produced, and the like, but is usually 3 to 50% by weight, preferably, 3 to 50% by weight. It can be in the range of 5 to 30% by weight.

The method of coating is not particularly limited.
Spin coating, roll coating, printing, immersion pulling, curtain coating, Meyer bar coating,
Doctor blade method, knife coat method, die coat method,
A gravure coating method, a microgravure coating method, an offset gravure coating method, a lip coating method, a spray coating method, or the like can be used. After the application, the solvent can be removed if necessary, and the liquid crystal material can be formed into a uniform layer.

The method for producing a liquid crystal film of the present invention includes a step of aligning the developed liquid crystal material to a smectic liquid crystal phase having the helical structure such that the helical axis direction is substantially perpendicular to the film surface.

The expression that the helical axis direction is substantially perpendicular to the film surface means that the helical axis direction is macroscopically substantially perpendicular to the film surface. The angle of the helical axis with respect to the film surface is not particularly limited, but is usually between 70 ° and 90 °, preferably between 80 ° and 90 °.

The method for the orientation is not particularly limited.
It can be performed simultaneously with or separately from the step of developing. For example, when the liquid crystal material is developed at a temperature at which a smectic liquid crystal phase having a helical structure can be obtained, a smectic liquid crystal phase having a helical structure may be obtained simultaneously with the development. Further, the developed liquid crystal material is heated once, and a phase developed at a higher temperature than the smectic liquid crystal phase having a helical structure, for example, a smectic A phase, a chiral nematic phase, an isotropic phase, and the like, and then having a helical structure Alignment can also be performed by cooling to a temperature at which a smectic liquid crystal phase develops. The heating is performed simultaneously or separately with the above-mentioned bonding of the plastic substrates,
It can also be performed by passing a liquid crystal material held between two plastic substrates between two heated rolls or a heat treatment furnace.

The orientation may be formed on the entire surface of the film, or may be formed only on a part of the film.

In the developing step or in any subsequent step, for example, in the alignment step, the magnetic material, electric field, shear stress, flow, stretching, and temperature gradient may be applied to the liquid crystal material developed between the interfaces as necessary. Etc. can be acted upon. By performing such an operation, the step of orienting the helical axis orientation substantially perpendicular to the film surface may be achieved in a shorter time in some cases. In particular, shear stress is preferable because it can be easily applied without requiring large electric power.

The method for producing a liquid crystal film of the present invention includes a step of fixing the alignment.

The step of fixing the alignment includes: (A) a step of cooling the aligned liquid crystal material to a glassy state;
Alternatively, (B) a step of performing polymerization while maintaining the orientation of the oriented liquid crystal material can be included.

In the step (A), as the liquid crystal material,
It can be performed using a liquid crystal material that exhibits a smectic liquid crystal phase having a desired helical structure at a temperature equal to or higher than the glass transition temperature, such as one containing the high-molecular liquid crystal substance as a main component, and can be brought into a glassy state by cooling. .

In the step (A), the step of aligning is performed at a temperature equal to or higher than the glass transition temperature of the liquid crystal material, and then the aligned liquid crystal material is cooled and cooled to a temperature at which the liquid crystal material becomes glassy. In addition, the liquid crystal material can be fixed in a glassy state without being in a crystalline state. The cooling means is not particularly limited, and it is possible to perform desired cooling sufficient for immobilization simply by taking out from a heating atmosphere in a development or orientation step to an atmosphere below the glass transition point, for example, at room temperature. In order to increase the production efficiency and the like, forced cooling such as air cooling or water cooling may be performed.

The step (B) can be performed using a material containing a substance having a substituent that can react with ultraviolet light, visible light, electron beam, heat, or the like as the liquid crystal material. As the substituent, a vinyl group, an acryl group, a methacryl group, a vinyl ether group, a cinnamoyl group, an allyl group, an acetylenyl group, a crotonyl group, an aziridinyl group,
Epoxy group, isocyanate group, thioisocyanate group, amino group, hydroxyl group, mercapto group, carboxylic acid group,
An acyl group, a halocarbonyl group, an aldehyde group, a sulfonic acid group, a silanol group and the like can be mentioned, preferably a group having a multiple bond, an epoxy group, an aziridinyl group and the like are more preferable. Examples thereof include an acryl group, a methacryl group, a vinyl group, a vinyl ether group, an epoxy group, and a cinnamoyl group. These substituents may be contained in any one or more of the liquid crystal substance and / or the non-liquid crystal substance and / or the additive. In the case of two or more substances, the same and / or different substituents are contained. It may be. In addition, two or more of the same and / or different substituents may be contained in one kind of substance.

In the step (B), polymerization is performed while maintaining the orientation of the oriented liquid crystal material. The polymerization method is not particularly limited, and reactions such as thermal polymerization, photopolymerization, radiation polymerization such as γ-ray, electron beam polymerization, polycondensation, and polyaddition can be used. Among them, it is preferable to use photopolymerization or electron beam polymerization using visible light or ultraviolet light, which is easy to control the reaction and is advantageous in production.

The liquid crystal film of the present invention is manufactured by the manufacturing method of the present invention.

The thickness of the liquid crystal film of the present invention is not particularly limited, but is preferably 0.1 to 10 from the viewpoint of orientation.
0 μm, more preferably 0.2 to 50 μm, further preferably 0.3 to 20 μm.

The optical element of the present invention contains at least the liquid crystal film produced by the above-mentioned production method of the present invention.

More specifically, the liquid crystal film formed between the two plastic substrates by the manufacturing method of the present invention is processed as it is or as necessary by appropriately processing the optical element of the present invention. can do. For example, an optical element can be used as it is formed between substrates, an optical element can be obtained by peeling at least one plastic substrate, or different from a substrate used for development. An optical element can be formed by laminating a film on another substrate. Further, an optical element having a plurality of layers of films having the same or different properties may be provided.

The other substrate is not particularly limited, and examples thereof include polyimide, polyamideimide, polyamide, polyetherimide, polyetheretherketone, polyetherketone, polyketonesulfide, polyethersulfone, polysulfone, polyphenylenesulfide, and the like.
Cellulose such as polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, methacrylic resin, polyvinyl alcohol, polyethylene, polypropylene, poly-4-methylpentene-1 resin, and triacetyl cellulose Plastic substrates such as plastics, epoxy resin, and phenolic resin, and the above-mentioned glass substrates, ceramic substrates, paper, metal plates, polarizing plates, retardation plates, reflection plates,
Other optical elements such as a diffuser plate, a plastic substrate with irregularities, etc. can be used. The liquid crystal film of the present invention can be used as an element in which the orientation of the helical axis is defined without causing alignment disorder or the like even when the substrate is removed.

For the purpose of protecting the surface, increasing the strength, and improving the environmental reliability, a protective layer such as a transparent plastic film or a hard coat layer may be provided on the liquid crystal film as required. it can.

When light is incident on the optical element of the present invention, characteristics such as birefringence, optical rotation, polarization separation characteristics, a waveguide, selective reflection, and the like, or a combination thereof can be obtained. Therefore, the optical element of the present invention makes use of these properties to provide various optical elements such as a birefringent element, an optical rotation element, a polarization separation element, a waveguide element, a selective reflection element, or an element obtained by combining them. be able to.

[0060]

The manufacturing method of the present invention includes a step of spreading a specific liquid crystal material between specific substrates, a step of aligning in a specific direction, and the like, so that the helical axis orientation of the smectic liquid crystal phase having a helical structure is reduced. A liquid crystal film fixed to be substantially perpendicular to the substrate surface and having a large area and light weight can be manufactured at low cost. In particular, it is applicable to continuous mass production of roll-to-roll and the like.

Since the liquid crystal film and the optical element of the present invention are or include the liquid crystal film produced by the production method of the present invention, the helical axis direction of the smectic liquid crystal phase having a helical structure is determined by the substrate. A liquid crystal film and an optical element fixed so as to be substantially perpendicular to a surface. The liquid crystal film and the optical element can have a large area, are lightweight, and can be manufactured at low cost. Optical rotation, polarization separation characteristics, selective reflection characteristics,
Various properties such as diffraction characteristics can be set freely and in a stable state. Furthermore, it has features of high heat resistance, impact resistance, chemical resistance, high strength and light weight, good dimensional stability, can be manufactured in large area at low cost, and is easy to handle. Incorporation into other systems is very easy. Therefore, it is useful in the fields of optics, optoelectronics, liquid crystal display, security, and design.

[0062]

The present invention will be described in more detail with reference to the following examples.
The present invention is not limited to these.

In the examples, the measurement of the intrinsic viscosity, the determination of the liquid crystal phase series, the measurement of the refractive index, the measurement of the film thickness, and the measurement of the transmission spectrum were carried out according to the following methods. (1) Measurement of Intrinsic Viscosity Using an Ubbelohde viscometer, it was measured in a phenol / tetrachloroethane (60/40 weight ratio) mixed solvent at 30 ° C. (0.5 g / dL). (2) Determination of liquid crystal phase series Determined by DSC (Perkin Elmer DSC-7) measurement and observation with an optical microscope (BX50 polarizing microscope manufactured by Olympus Optical Co., Ltd.). (3) Measurement of Refractive Index The refractive index was measured using an Abbe refractometer (Type-4, manufactured by Atago Co., Ltd.). (4) Film thickness measurement Dektak, a surface profile measuring device manufactured by Japan Vacuum Engineering Co., Ltd.
Model 3030ST was used. Also, interference wave measurement (UV-visible / near-infrared spectrophotometer V-570 manufactured by JASCO Corporation)
And a method of obtaining the film thickness from the data of the refractive index was also used. (5) Measurement of transmission spectrum The transmission spectrum was measured using a V-570 type spectrophotometer manufactured by JASCO Corporation. (6) Confirmation of helical axis direction Optical microscope (BX50 polarizing microscope manufactured by Olympus Optical Co., Ltd.)
A conoscopic observation was carried out using to confirm.

[0064]

Example 1 200 mmol of dimethyl 4,4'-biphenyldicarboxylate, (R) -1,3-butanediol (enantiomeric excess, ee)
= 95.0%) A liquid crystalline polyester was synthesized by melt polymerization at 220 ° C for 2 hours using 80 mmol, 120 mmol of 1,5-pentanediol, and tetra-n-butyl orthotitanate as a catalyst (intrinsic viscosity). 0.20 dL / g).

15% by weight of N of this liquid crystalline polyester
A -methyl-2-pyrrolidone solution was prepared and applied to a polyethylene terephthalate (PET) film (critical surface tension: 43 dyne / cm) substrate by a spin coating method, and the solvent was removed at 60 ° C on a hot plate.
While laminating another identical PET film on the application surface, the film was passed between rolls of a laminating apparatus having two heating rolls. The roll temperature at this time is 150 ° C
When the liquid crystal material passes between the rolls,
Shear stress due to pressure was applied. Thereafter, the mixture was further cooled in a thermostat from 150 ° C. to 50 ° C. at a rate of 5 ° C./min, and taken out at room temperature.

Next, one PET film was peeled off, and an 80 μm-thick triacetyl cellulose (TAC) film was bonded to the peeled surface with an adhesive, and then the other PET film was peeled off.
The film was peeled off to obtain an optical element including a liquid crystal film. The liquid crystal film in the device was glass-fixed with a chiral smectic C _A phase having a helical structure, and had a substantially uniform film thickness (12 μm). In addition, from conoscopic observation using a polarizing microscope, it was confirmed that the helical axis orientation was substantially 90 degrees with respect to the film surface. When a transmission spectrum of this optical element was measured at an incident angle of 45 degrees, one selective reflection derived from a half pitch was shown.

[0067]

Embodiment 2

[0068]

Embedded image

10 g of a 10:90 (weight ratio) mixture of the bifunctional low-molecular liquid crystal substance (1) and the monofunctional chiral liquid crystal substance (2), and Irgacure 907 as a photopolymerization initiator.
(Product name, Ciba Specialty Chemicals) 0.
2 g and 0.045 g of Kayacure DETX (trade name, manufactured by Nippon Kayaku) as a sensitizer were mixed by heating to obtain a uniform liquid crystal material. Next, the liquid crystal material is coated with a TA having a thickness of 80 μm.
After applying to a C substrate (critical surface tension of 38 dyne / cm) using a doctor blade, a 38 μm-thick silicone surface-treated PET substrate (critical surface tension of the silicone-treated surface of 18 dyne / cm) was used. We stuck together. Next, using a laminating apparatus having two heating rollers, the mixture was passed between heating rollers at a temperature of 90 ° C. showing a smectic A phase, and further heat-treated at 90 ° C. for 2 minutes in a thermostat. Then 40 ° C
Cool slowly at 5 ° C / min.
The alignment of the liquid crystal material was fixed by photopolymerization using an ultraviolet irradiation device having a high-pressure mercury lamp of 0 W / cm at an irradiation energy of 600 mJ / cm ² . After the alignment was fixed, the PET substrate subjected to the silicone surface treatment was peeled off to obtain an optical element including a liquid crystal film. The liquid crystal film in the optical element thus obtained was fixed with a chiral smectic C phase having a helical structure, and had a substantially uniform film thickness (10 μm). In addition, from conoscopic observation using a polarizing microscope, it was confirmed that the helical axis direction was substantially 90 degrees with respect to the film surface. This optical element showed selective reflection derived from half pitch, and selectively reflected right circularly polarized light. When the transmission spectrum of this optical element was measured at an incident angle of 45 degrees, two selective reflections derived from a half pitch and a full pitch were shown as shown in FIG.

[0070]

Embodiment 3

[0071]

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10 g of a 10:90 (weight ratio) mixture of the bifunctional low-molecular liquid crystal substance (3) and the monofunctional chiral liquid crystal substance (4), and Irgacure 907 as a photopolymerization initiator.
(Product name, Ciba Specialty Chemicals) 0.
2 g and 0.045 g of Kayacure DETX (trade name, manufactured by Nippon Kayaku) as a sensitizer were once dissolved in dichloromethane, and the solvent was removed to obtain a uniform liquid crystal material. Next, two TAC substrates having a thickness of 80 μm (critical surface tension of 38 dyne / cm) were prepared, and the liquid crystal material was applied to one of the TAC films using a doctor blade. Next, while laminating another TAC film on the application surface, the TAC film was passed between rolls of a laminating apparatus having two heating rollers. At this time, the temperature of the two heating rolls was adjusted to a value such that the liquid crystal material exhibited a smectic A phase of 80.
Set to ° C. Then, after further heat-treating at 80 ° C. for 2 minutes in a thermostatic oven, gradually cooled to 40 ° C. at 5 ° C./min, taken out to room temperature and quickly 600 mJ / cm ² using an ultraviolet irradiation apparatus having a 120 W / cm high-pressure mercury lamp. By performing photopolymerization with the irradiation energy of the above, the orientation of the liquid crystal material was fixed, and an optical element including a liquid crystal film was obtained. Liquid crystal film in the resultant optical element is fixed in a chiral smectic C _A phase having a helical structure, it was nearly uniform thickness (15 [mu] m). In addition, from conoscopic observation using a polarizing microscope, it was confirmed that the helical axis orientation was substantially 90 degrees with respect to the film surface. Further, when a transmission spectrum of this optical element was measured at an incident angle of 45 degrees, one selective reflection derived from a half pitch was shown.

[Brief description of the drawings]

FIG. 1 is a view showing a measurement result of a transmission spectrum of an optical element of the present invention measured in Example 2.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Ryo Nishimura 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Central Research Laboratory, Nishiishi Mitsui Co., Ltd. (72) Shinichi Komatsu 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Address F-term in Nisseki Mitsui Co., Ltd. Central Research Laboratory (reference) 2H049 BA05 BA43 BC02 2H090 JB03 JB05 JC11 LA06 MA04 MB13

Claims (8)

[Claims] 1. A liquid crystal material exhibiting a smectic liquid crystal phase having a helical structure is prepared from a liquid crystal material having a critical surface tension of 50 dyne / c.
m, the step of developing the liquid crystal material between two plastic substrates, the step of aligning the developed liquid crystal material in a smectic liquid crystal phase having the helical structure such that the helical axis orientation is substantially perpendicular to the film surface; A method for producing a liquid crystal film, comprising a step of fixing the alignment. 2. The method according to claim 1, wherein the plastic substrate is a substrate that has not been subjected to an alignment treatment. 3. The step of aligning is performed at a temperature equal to or higher than the glass transition temperature of the liquid crystal material, and the step of fixing the alignment includes a step of cooling the aligned liquid crystal material to a glassy state. The method for producing a liquid crystal film according to claim 1, wherein: 4. The method for producing a liquid crystal film according to claim 1, wherein the step of fixing the orientation includes a step of polymerizing the oriented liquid crystal material while maintaining the orientation. . 5. The method for producing a liquid crystal film according to claim 1, wherein the smectic liquid crystal phase is a chiral smectic C phase. 6. The method for producing a liquid crystal film according to claim 1, wherein the smectic liquid crystal phase is a chiral smectic C _A phase. 7. A liquid crystal film produced by the method according to claim 1. 8. An optical element comprising at least a liquid crystal film produced by the method according to claim 1.