JP2001004834A - Polarizing diffraction element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both selectively reflecting characteristic and circularly polarizing characteristic to reveal an optical effect having both the characteristics in a good balance regardless of the surface or reverse side of a polarizing diffraction element by constituting the polarizing diffraction element from a cholesteric liquid crystal layer partially having an area showing diffractivity, and setting the number of spiral turns in the cholesteric alignment of this liquid crystal layer in a specified range. SOLUTION: This polarizing diffraction element is formed of at least a cholesteric liquid crystal layer partially having an area showing diffractivity. The area showing diffractivity means the area causing the effect such that the light transmitted or reflected by this area creeps into a part geometrically forming a shadow. In this cholesteric liquid crystal, the number of spiral turns in the cholesteric alignment is within the range of 2-20. When the winding is less than two, the selective reflectivity or circular polarizability by cholesteric alignment might be deteriorated. When the number of turns exceeds 20, the selective reflectivity or circularly polarizability might appear too conspicuously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization diffraction element that can generate a polarized diffracted light.

[0002]

2. Description of the Related Art A diffractive element is a general-purpose optical element that is widely used in the field of spectral optics and the like for the purpose of splitting light and splitting a light beam. Diffraction elements are classified into several types based on their shape.Amplitude type diffraction elements, in which light-transmitting and non-light-transmitting parts are periodically arranged, are phase-type, in which periodic grooves are formed in a highly transparent material. It is usually classified as a diffraction element. Further, they may be classified as a transmission type diffraction element or a reflection type diffraction element according to the direction in which diffracted light is generated.

In the above-described conventional diffraction element, only non-polarized light can be obtained as diffracted light obtained when natural light (non-polarized light) is incident. Polarizing optical instruments such as ellipsometers, which are frequently used in the field of spectroscopy, can only obtain non-polarized light as diffracted light. In general, a method of using diffracted light through a polarizer in order to use only the polarized light component is used.
In this method, there is a problem that about 50% or more of the obtained diffracted light is absorbed by the polarizer, so that the amount of light is reduced by half. For that purpose, it is necessary to prepare a detector having a high sensitivity and a light source having a large amount of light, and the development of a diffraction element in which the diffracted light itself becomes a specific polarized light such as a circularly polarized light or a linearly polarized light has been required.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has succeeded in imparting diffractive power to a partial region of a cholesteric liquid crystal layer by controlling the structure of the liquid crystal layer. More specifically, by controlling the number of helical turns in the cholesteric liquid crystal phase, we have developed a liquid crystal layer that achieves both the selective reflection characteristic and circular polarization characteristic characteristic of cholesteric liquid crystal and the diffraction effect caused by the region showing diffractive power. As a result, the inventors have invented a polarization diffraction element having excellent visibility and design.

[0005]

That is, the present invention comprises at least a cholesteric liquid crystal layer partially having a region exhibiting a diffractive power, wherein the number of helical turns in the cholesteric orientation of the liquid crystal layer is in the range of 2 to 20 turns. Is a polarization diffraction element.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The polarization diffraction element of the present invention comprises at least a cholesteric liquid crystal layer partially having a region exhibiting diffractive power. Here, the region exhibiting the diffractive power means a region which produces an effect such that the light transmitted through the region or the light reflected by the region wraps around a portion which is geometrically shadow. The presence or absence of a region exhibiting a diffractive power is confirmed by, for example, the presence or absence of light (higher-order light) emitted at a certain angle other than light (0th-order light) that is incident on a film and transmitted or reflected linearly. be able to. As another method, by observing the surface shape and cross-sectional shape of the liquid crystal layer with an atomic force microscope, transmission electron microscope, etc.,
The presence or absence of a region exhibiting a diffraction ability can be confirmed.

The region exhibiting diffractive power in the cholesteric liquid crystal layer constituting the polarization diffraction element of the present invention may be any region inside the liquid crystal layer and / or inside the liquid crystal layer. (Liquid crystal layer surface area),
It may be provided in a part inside the liquid crystal layer (in the liquid crystal layer inner region). Further, the region exhibiting the diffractive power may be provided in a plurality of regions of the single cholesteric liquid crystal layer, for example, in the front and back regions of the cholesteric liquid crystal layer and in the plurality of liquid crystal layer internal regions. In addition, the region exhibiting the diffractive power does not necessarily need to be formed as a layer having a uniform thickness on the surface or inside the cholesteric liquid crystal layer, for example, and is formed at least partially on the surface of the liquid crystal layer or inside the liquid crystal layer. It is only necessary that a region is formed. For example, the region showing diffraction power,
It may have a shape of a desired figure, pictogram, number, symbol, or the like. Further, when a plurality of regions exhibiting diffractive power are provided, it is not necessary that all the regions exhibit the same diffractive power, and each region may exhibit a different diffractive power. In addition, the alignment state of the region exhibiting the diffractive power is such that the helical axis direction in the cholesteric liquid crystal phase is not uniformly parallel to the film thickness direction, preferably the helical axis direction in the cholesteric liquid crystal phase is uniformly parallel to the film thickness direction. In addition, it is desirable to form a cholesteric orientation in which the helical pitch is not uniformly spaced in the film thickness direction. Except for the region exhibiting diffraction power,
An alignment state similar to the normal cholesteric alignment, that is, a helical structure in which the helical axis orientation in the cholesteric liquid crystal phase is uniformly parallel to the film thickness direction and the helical pitch is uniformly spaced in the film thickness direction. It is desirable. In the present invention, the surface of the cholesteric liquid crystal layer means a portion of the cholesteric liquid crystal layer which is in contact with the outside, and the inside of the liquid crystal layer means a portion other than in contact with the outside.

The cholesteric liquid crystal layer constituting the polarization diffraction element of the present invention has a cholesteric orientation in the range of 2 to 20, preferably 2.2 to 16, more preferably 2.5 to 13 spiral turns. is there. When the number of helical turns of the cholesteric liquid crystal layer is less than two, there is a possibility that the selective reflection characteristics and the circular polarization characteristics due to the cholesteric alignment are reduced. When the number of windings is more than 20, there is a possibility that the selective reflection characteristic and the circular polarization characteristic due to the cholesteric orientation may appear too much. Since the polarization diffraction element of the present invention is at least composed of a cholesteric liquid crystal layer having the above-mentioned helical winding number, selective reflection characteristics caused by cholesteric alignment regardless of the front and back of the element,
It is possible to obtain the element in which the circular polarization characteristic and the diffraction characteristic caused by the region exhibiting the diffractive ability are compatible with a good balance, and it is also possible to easily confirm both optical characteristics.

The cholesteric liquid crystal layer having the above-mentioned region exhibiting diffractive power and a desired number of helical windings is formed by forming a cholesteric alignment layer using, for example, a polymer liquid crystal, a low molecular weight liquid crystal or a mixture thereof as a liquid crystal material. A method of transferring a diffraction pattern of a diffraction element substrate to a cholesteric alignment layer by applying a heat and / or a pressure to the diffraction element substrate, or a polymer liquid crystal, a low molecular weight liquid crystal or a liquid crystal thereof using the diffraction element substrate as an alignment substrate. After the liquid crystal material made of the mixture is cholesterically aligned, it can be obtained by, for example, fixing the liquid crystal material while maintaining the alignment state.

The polymer liquid crystal used as the liquid crystal material of the cholesteric liquid crystal layer and the cholesteric alignment layer is not particularly limited as long as the cholesteric alignment can be fixed, and any of a main chain type and a side chain type polymer liquid crystal can be used. can do. Specific examples include main-chain liquid crystal polymers such as polyester, polyamide, polycarbonate, and polyesterimide, and side-chain liquid crystal polymers such as polyacrylate, polymethacrylate, polymalonate, and polysiloxane. Among them, a liquid crystalline polyester which has good orientation in forming cholesteric orientation and is relatively easy to synthesize is desirable. Preferable examples of the structural unit of the liquid crystalline polyester include an aromatic or aliphatic diol unit, an aromatic or aliphatic dicarboxylic acid unit, and an aromatic or aliphatic hydroxycarboxylic acid unit.

[0011] Further, low-molecular liquid crystal as a liquid crystal material includes:
For example, a liquid crystal having a basic skeleton of a biphenyl derivative, a phenylbenzoate derivative, a stilbene derivative, or the like into which a functional group such as an acryloyl group, a vinyl group, or an epoxy group is introduced can be given. As the low-molecular liquid crystal, both lyotropic properties and thermotropic properties can be used, but those exhibiting thermotropic properties are more preferable from the viewpoint of workability, process and the like.

In order to improve the heat resistance of the finally obtained cholesteric liquid crystal layer, for example, a bis azide compound or a bis azide compound may be used as long as the cholesteric phase is not impaired in the liquid crystal material in addition to the polymer liquid crystal and the low molecular liquid crystal. A cross-linking agent such as glycidyl methacrylate can be added, and by adding these cross-linking agents, cross-linking can be performed with a cholesteric liquid crystal phase developed. Furthermore, in the liquid crystal material, dichroic dyes, dyes, pigments, antioxidants,
Various additives such as an ultraviolet absorber and a hard coat agent can be appropriately added as long as the effects of the present invention are not impaired.

The number of spiral windings can be appropriately adjusted by the pitch (the length in the direction of the spiral axis required for one rotation of the spiral) and the film thickness. The pitch can be appropriately adjusted to a desired value depending on the content of the optically active site in the liquid crystal material. Although the content of the optically active site differs depending on the type (composition ratio, etc.) and various physical properties of the polymer liquid crystal or the low molecular liquid crystal, and the manufacturing conditions of the cholesteric alignment layer before transferring the diffraction pattern, it cannot be unconditionally determined. The content is usually at least 3%, preferably 5 to 70%, more preferably 10 to 50% based on the liquid crystal material. The optically active site may be contained in the structure of a high-molecular liquid crystal or a low-molecular liquid crystal which is a main component of the liquid crystal material, or a compound which does not exhibit liquid crystallinity and which can be appropriately added as a sub-component of the material. Etc. may be included in the structure. In addition, the said content is only an illustration to the last, and this invention is not limited to this at all. The adjustment of the film thickness is different depending on the method of applying the liquid crystal material and the like, and cannot be unconditionally described. For example, when applying a solution, the solution concentration of the liquid crystal material is usually 3 to 70% by weight, preferably 5 to 50% by weight. %, More preferably in the range of 7 to 30% by weight. Note that the solution concentration is merely an example, and the present invention is not limited to this. Here, the actual thickness of the cholesteric liquid crystal layer and the actual thickness of the cholesteric alignment layer before the transfer of the diffraction pattern is not particularly limited, but is generally 0.1 to 30 μm, preferably from the viewpoint of mass productivity and a manufacturing process. 0.
It is desirable that the thickness be 3 to 20 μm, more preferably 0.5 to 10 μm.

As a method for producing a cholesteric alignment layer before transferring a diffraction pattern, for example, when a polymer liquid crystal is used, for example, the polymer liquid crystal is arranged on a support substrate or an alignment film formed on the substrate. After that, a method of developing a cholesteric liquid crystal phase by a heat treatment or the like, and rapidly cooling the state to fix the cholesteric orientation can be adopted. When using a low-molecular liquid crystal, for example, after arranging the low-molecular liquid crystal on a support substrate or an alignment film formed on the substrate, a cholesteric liquid crystal phase is developed by heat treatment or the like, and light, A method of fixing the cholesteric orientation by crosslinking with heat or an electron beam or the like can be appropriately employed.

The diffraction element substrate used for transferring a diffraction pattern or as a support substrate when the liquid crystal material is oriented as described above is a diffraction element substrate formed of a material such as a metal or a resin, or a diffraction element formed on a film surface. A diffraction element substrate made of any material and configuration may be used as long as it has a diffraction function, such as a substrate having a function or a thin film having a diffraction function transferred to a film. Above all, in view of ease of handling and mass productivity, it is desirable in the present invention to use a film or a film laminate having a diffraction function as the diffraction element substrate.

The term "diffraction element" as used herein includes, as its definition, all diffraction elements which generate diffracted light, such as an original flat hologram. The type may be a diffraction element derived from the surface shape, a so-called film thickness modulation hologram type, or a phase element independent of the surface shape or a surface shape converted into a refractive index distribution, a so-called refraction. A rate modulation hologram type may be used. In the present invention, a diffraction element substrate of a film thickness modulation hologram type is more preferably used in that the diffraction pattern information of the diffraction element can be more easily given to the liquid crystal. In addition, even a refractive index modulation type diffraction element substrate can be suitably used in the present invention as long as it has undulations that cause diffraction in the surface shape.

As a method of transferring a diffraction pattern, for example, generally used heat rollers, laminators,
Using a hot stamp, an electric heating plate, a thermal head, or the like, it can be performed under pressurized and / or heated conditions. Pressing conditions and heating conditions vary depending on the physical properties of the polymer liquid crystal and low molecular liquid crystal used, the type of diffraction element substrate, etc.
Although it cannot be said unconditionally, usually, the pressure is 0.01 to 100MPa.
a, preferably 0.05 to 80 MPa, temperature 30 to 40
It is appropriately selected according to the type of liquid crystal, substrate, etc. used in the range of 0 ° C., preferably 40 to 300 ° C. Further, when transferring the diffraction pattern, it is desirable in the present invention that the transfer is performed under conditions where pressure and heating can be applied simultaneously. By transferring the diffraction pattern of the diffraction element substrate to the cholesteric alignment layer under the above-mentioned heating and / or pressurizing conditions, a cholesteric liquid crystal layer partially having a region exhibiting a diffractive ability can be obtained.

When a diffraction element substrate is used as an alignment substrate, a liquid crystal material is spread on the substrate by a method such as solution coating or melt coating, and then heat-treated and cooled. After going,
A cholesteric liquid crystal layer partially having a region exhibiting diffractive ability can be obtained by a method of irradiating light or an electron beam. Further, an alignment treatment such as a rubbing treatment can be appropriately performed on the surface of the diffraction element substrate in contact with the liquid crystal material.

The polarization diffraction element of the present invention has the cholesteric liquid crystal layer obtained by the above method as a component. As a specific embodiment, for example, if the cholesteric liquid crystal layer has sufficient self-supporting properties,
The liquid crystal layer alone can be used for various applications as a polarization diffraction element. If it does not have a self-supporting property, various plastic films / sheets, glass substrates, paper such as high-quality paper or synthetic paper are laminated on the substrate as a supporting substrate, or as they are formed on an oriented substrate. Further, a device in a state of being laminated and formed on a diffraction element substrate can be used as a polarization diffraction element. In the cholesteric liquid crystal layer, a protective layer can be provided on the surface of the liquid crystal layer. In the case where the protective layer has sufficient self-supporting property, a laminate composed of the protective layer / cholesteric liquid crystal layer can be used as a polarization diffraction element for various applications. It is particularly desirable that the protective layer has an ultraviolet absorbing property and / or a hard coat property. For example, a material formed of a protective layer containing a UV absorber and a hard coat agent into a film, sheet, thin film, or plate can be used as the protective layer. Further, a protective layer having an ultraviolet absorbing property made of a protective layer forming material containing an ultraviolet absorbent (hereinafter, referred to as an ultraviolet absorbing layer) and a protective layer having a hard coating property made of a protective layer forming material containing a hard coat agent (Hereinafter, a hard coat layer) may be used as a protective layer.
In addition, a commercially available ultraviolet cut film or hard coat film, or a laminate of the film can be used as the protective layer. A laminate formed by applying various hard coat agents to the ultraviolet absorbing layer to form a film can also be used as the protective layer. Here, the ultraviolet absorbing layer and the hard coat layer may each be formed from two or more layers,
Each layer can be laminated via an adhesive layer or the like.

As the material for forming the protective layer, those having high light transmittance are desirable. For example, polyethylene, polypropylene, poly (4-methyl-pentene-1), polystyrene, ionomer, polyvinyl chloride, polymethyl methacrylate, polyethylene terephthalate, polyamide,
A material obtained by adding an ultraviolet absorber and / or a hard coat agent to polysulfone, a cellulose resin, or the like can be used. Further, as the protective layer, an adhesive composition obtained by adding an ultraviolet absorber and / or a hard coat agent to a light or electron beam curing type reactive adhesive can be used,
A cured product of the adhesive composition can be used as a protective layer.

The ultraviolet absorber is not particularly limited as long as it is compatible or dispersible in the protective layer forming material. For example, a benzophenone compound, a salsylate compound,
Organic ultraviolet absorbers such as benzotriazole-based compounds, oxalic anilide-based compounds, and cyanoacrylate-based compounds, and inorganic ultraviolet absorbers such as cesium oxide, titanium oxide, and zinc oxide can be used. Among them, a benzophenone-based compound having high ultraviolet absorption efficiency is preferably used. In addition, one or more ultraviolet absorbers can be added. The blending ratio of the ultraviolet absorber in the protective layer varies depending on the material for forming the protective layer to be used.
It is 1 to 20% by weight, preferably 0.5 to 10% by weight.

The hard coat agent is not particularly limited as long as it is compatible or dispersible in the protective layer forming material.
For example, use of an inorganic compound such as an organopolysiloxane-based, photo-curable resin-based acrylic oligomer-based, urethane acrylate-based, epoxy acrylate-based, polyester acrylate-based, thermosetting resin-based acryl-silicone-based, or ceramics. Can be. Above all, an organopolysiloxane-based or photo-curable resin-based acrylic oligomer-based hard coat agent is preferably used from the viewpoint of film-forming properties and the like. These hard coat agents are
Either a solventless type or a solvent type can be used.

As the light or electron beam curing type reactive adhesive, a photopolymer or electron beam polymerizable prepolymer and / or a monomer may be used, if necessary, with another monofunctional or polyfunctional monomer, various polymers, or a stable polymer. It is possible to use a mixture of an agent, a photopolymerization initiator, a sensitizer and the like.

Examples of the prepolymer having photo- or electron beam polymerizability include polyester acrylate, polyester methacrylate, polyurethane acrylate, polyurethane methacrylate, epoxy acrylate, epoxy methacrylate, polyol acrylate, and polyol methacrylate. . Examples of the monomer having photo- or electron beam polymerizability include monofunctional acrylate, monofunctional methacrylate, difunctional acrylate, difunctional methacrylate, trifunctional or higher polyfunctional acrylate, and polyfunctional methacrylate. These can also use a commercial item, for example, Aronix (acrylic special monomer, oligomer;
Toagosei Co., Ltd.), Light Ester (Kyoeisha Chemical Co., Ltd.),
Viscote (manufactured by Osaka Organic Chemical Industry) or the like can be used.

As the photopolymerization initiator, for example, benzophenone derivatives, acetophenone derivatives, benzoin derivatives, thioxanthones, Michler's ketone, benzyl derivatives, triazine derivatives, acylphosphine oxides, azo compounds and the like can be used. .

The viscosity of the light- or electron-beam-curable reactive adhesive which can be used as the protective layer is appropriately selected depending on the processing temperature of the adhesive, and cannot be unconditionally determined. To 2000 mPa · s, preferably 50 to 1000 mPa · s, more preferably 100
５００500 mPa · s. When the viscosity is lower than 10 mPa · s, it becomes difficult to obtain a desired thickness. Also 200
If it is higher than 0 mPa · s, the workability may decrease, which is not desirable. When the viscosity is out of the above range, it is preferable to appropriately adjust the solvent and the monomer ratio to obtain a desired viscosity.

When a photocurable reactive adhesive is used, a known curing method such as a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, or a xenon lamp may be used as a method for curing the adhesive. Can be. Further, the exposure amount cannot be determined unconditionally because it varies depending on the type of the reactive adhesive used, but it is usually 50 to 2000 mJ / cm.
² , preferably 100 to 1000 mJ / cm ² .

When an electron beam-curable reactive adhesive is used, the method of curing the adhesive is appropriately selected depending on the penetrating power and curing power of the electron beam, and cannot be unconditionally determined. Usually, curing can be carried out by irradiating under an acceleration voltage of 50 to 1000 kV, preferably 100 to 500 kV.

In addition to the ultraviolet absorber and the hard coat agent, if necessary, a light stabilizer such as a hindered amine or a quencher, an antistatic agent, a slipperiness improver, a dye, a pigment, etc. Also, various additives such as a surfactant and a filler such as fine silica and zirconia can be blended. The mixing ratio of these various additives is not particularly limited as long as the effects of the present invention are not impaired.
It is from 0.01 to 10% by weight, preferably from 0.05 to 5% by weight.

Further, the ultraviolet absorbing layer constituting the protective layer can be formed by using a material obtained by appropriately blending the above-described protective layer forming material with an ultraviolet absorbing agent and, if necessary, a light stabilizer. Further, a commercially available ultraviolet cut film or the like can be used as the ultraviolet absorbing layer in the present invention.

The hard coat layer constituting the protective layer is
The protective layer can be formed by using a material in which a hard coat agent and various additives are added to the protective layer forming material described above. The hard coat layer may be formed by applying the above hard coat agent on a transparent support film. As a transparent support film, polymethyl methacrylate, polystyrene, polycarbonate,
Examples include films formed from polyether sulfone, polyphenylene sulfide, amorphous polyolefin, triacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate, and the like.

The protective layer can be formed by laminating the ultraviolet absorbing layer and the hard coat layer via an adhesive or the like. The adhesive used in this case may be the light or electron beam curing described above. Preferred examples include reactive adhesives of the type. The protective layer can also be formed by using an adhesive containing an ultraviolet absorber and laminating a separately prepared hard coat layer on the cholesteric liquid crystal layer of the present invention. Further, a dye, a pigment, a surfactant and the like may be appropriately added to the adhesive as needed.

Further, as the hard coat layer, a vehicle resin for gravure ink or the like can be suitably used.
Examples of the gravure ink vehicle resin include nitrocellulose, ethyl cellulose, polyamide resin, vinyl chloride, chlorinated polyolefin, acrylic resin, polyurethane, polyester, and the like. In addition, hard resins such as ester gum, dammar gum, maleic resin, alkyd resin, phenol resin, ketone resin, xylene resin, terpene resin, petroleum resin, etc. are used in the gravure ink vehicle resin in order to improve adhesion and film strength. May be blended.

The structure of the hard coat layer can be a single hard coat layer or a composite layer according to the required weather resistance and the like. As the composite layer, for example, a hard coat layer containing an organopolysiloxane, a hard coat layer containing a photocurable resin, a hard coat layer containing a thermosetting resin,
A composite layer composed of two or more layers, such as a hard coat layer containing an inorganic compound, may be used as the hard coat layer.

As a method for forming an ultraviolet absorbing layer and / or a hard coat layer serving as a protective layer on the cholesteric liquid crystal layer constituting the polarization diffraction element of the present invention, usually, a roll coating method, a dipping method, a gravure coating method, a bar coating method, or the like is used. Known methods such as a code method, a spin coating method, a spray coating method, and a printing method can be employed. After forming a film on the cholesteric liquid crystal layer by any of these methods, a protective layer can be formed by performing post-processing according to the protective layer forming material used. As a method for forming a protective layer composed of a composite layer of an ultraviolet absorbing layer and a hard coat layer,
For example, a method of directly applying and forming a hard coat agent on the ultraviolet absorbing layer, a method of laminating via an adhesive or the like, and the like can be mentioned.

The thickness of the protective layer cannot be determined unconditionally because it differs depending on the performance required for the ultraviolet absorbing property and / or the hard coating property, but it is usually 0.1 to 100.
μm, preferably 1 to 50 μm. Also, when the protective layer is formed of a composite layer with an ultraviolet absorbing layer and a hard coat layer, the total thickness of each layer is preferably within the above range.

In the polarization diffraction element of the present invention, since a part of the cholesteric liquid crystal layer constituting the element has a region exhibiting a diffractive ability, a conventional optical member in which the diffracted light has a circular polarization property. It has a unique effect that is not found in. Due to this effect, it is possible to extremely increase the light use efficiency by using, for example, a spectroscopic optical device that requires polarized light, such as an ellipsometer. Conventional spectroscopic optical devices that require polarized light use a diffraction element such as a diffraction grating or prism to separate the light emitted from the light source for each wavelength and then transmit the light through the polarizer, or transmit the light through the polarizer and then separate the light. It was necessary to have a polarizer. This polarizer has a problem that it absorbs about 50% of the incident light and has a problem of extremely low light utilization efficiency due to reflection at the interface. However, the use of the polarization diffraction element of the present invention Makes the light use efficiency extremely high, theoretically about 1
00% can be used. Further, the polarization diffraction element of the present invention can easily control transmission and blocking of diffracted light by using a normal polarizing plate. Normally, diffracted light having no polarization cannot be completely blocked by any combination of polarizing plates. That is, in the polarization diffraction element of the present invention, for example, the diffracted light having the right polarization property can be completely blocked only when the left circularly polarizing plate is used, and complete blocking can be achieved even with other polarizing plates. It is something that cannot be done. Because of such an effect, for example, in an environment in which an observer observes a diffraction image through a polarizing plate, by changing the state of the polarizing plate, the diffraction image suddenly emerges from the dark field, or suddenly disappears. It becomes possible.

As described above, the polarization diffraction element of the present invention has a very wide range of application as a new diffraction function element, and can be used as various optical elements, optoelectronic elements, decorative members, and forgery prevention elements. Can be.

Specific examples of the optical element and the optoelectronic element include transparent and isotropic films, specifically, triacetyl cellulose films such as Fujitac (manufactured by Fuji Photo Film) and Konikatac (manufactured by Konica). , TPX film (Mitsui Chemicals), Arton film (Nippon Synthetic Rubber), Zeonex film (Nippon Zeon), acrylene film (Mitsubishi Rayon), etc. By using the element, development to various optical applications can be achieved. For example, the polarization diffraction element is set to TN (twis
ted nematic) -LCD (Liquid C)
crystal Display), STN (Super
Twisted Nematic) -LCD, ECB
(Electrically Controlled
Birefringence) -LCD, OMI (Op
Tical Mode Interference)-
LCD, OCB (Optically Compensation)
attached Birefringence)-LCD, H
AN (Hybrid Aligned Nemati)
c) -LCD, IPS (In Plane Switchc)
hing)-Various types of Ls having improved color compensation and / or improved viewing angle by being provided in a liquid crystal display such as an LCD.
You can get a CD. Further, the polarization diffraction element of the present invention is used as a spectroscopic optical device that requires polarized light separated as described above, a polarization optical element that obtains a specific wavelength by a diffraction phenomenon, an optical filter, a circularly polarizing plate, a light diffusion plate, and the like. It is also possible to provide various optical members that can exhibit an optical effect that has not existed as an optical element or an optoelectronic element, for example, a linear polarizing plate can be obtained by combining with a quarter-wave plate. Can be.

As the decorative member, there can be obtained various designable molding materials including a new designable film having both a rainbow coloration effect by diffractive power and a colorful coloration effect by cholesteric liquid crystal. . In addition, since it can be made into a thin film, it can be expected that it is given a design property by attaching it to an existing product or the like, or integrating it, and greatly contributes to differentiation from other similar products. For example, when the polarizing diffraction element of the present invention incorporating a designable diffraction pattern is attached to a glass window or the like, the selective reflection specific to the cholesteric liquid crystal accompanied by the diffraction pattern looks different from the outside depending on the viewing angle. , And can be very excellent in fashionability. In addition, it is possible to provide a window in which the inside is hard to be seen from the bright outside, and the outside is good in visibility from the inside.

As the forgery preventing element, it can be used as a new forgery preventing film, a seal, a label or the like having both the forgery preventing effects of the diffraction element and the cholesteric liquid crystal. Specifically, for example, the polarizing diffraction element of the present invention, for example, a car driver's license, an identification card, a passport,
The effect can be exhibited by integrating with a credit card, a prepaid card, various cash vouchers, gift cards, securities, or the like, or by providing a part thereof, specifically, attaching, embedding, or weaving into paper. Further, the polarization diffraction element of the present invention has a region exhibiting diffractive ability in a part of the cholesteric liquid crystal layer, and also has a wavelength-selective reflectivity of the cholesteric liquid crystal, a circularly-polarized light selective reflectivity, a viewing angle dependency of color, and a beautiful color of cholesteric color. Is also exhibited. Therefore, when the polarization diffraction element of the present invention is used as a forgery prevention element, it can be said that forgery of the cholesteric liquid crystal layer constituting the element is extremely difficult. In addition to the anti-counterfeiting effect, it has an iridescent color effect of the diffractive element and a vivid color effect of the cholesteric liquid crystal, so that the design is excellent.

These applications are only examples, and the polarizing diffraction element of the present invention can be used for various applications in which a single diffraction element or a single cholesteric liquid crystal film is conventionally used, or can exhibit a new optical effect. Because it is possible, it can be applied to various applications other than the above-mentioned applications.

[0043]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples.

Example 1 50 mmol of terephthalic acid,
Hydroxybenzoic acid 20 mmol, catechol 20 mm
ol, (R) -2-methyl-1,4-butanediol 1
0 mmol and 100 mg of sodium acetate in a nitrogen atmosphere at 180 ° C. for 1 hour, 200 ° C. for 1 hour,
The polycondensation reaction was performed while the temperature was raised stepwise at 50 ° C. for 1 hour.

Next, the polycondensation reaction was continued at 250 ° C. for 2 hours while flowing nitrogen, and the polycondensation was further performed at the same temperature under reduced pressure for 1 hour. After dissolving the obtained polymer in tetrachloroethane, reprecipitation was performed with methanol to obtain a liquid crystalline polyester.

Next, the N-
Preparing a methyl-2-pyrrolidone solution (20% by weight);
The solution was applied on a rubbed polyphenylene sulfide film by a spin coating method. After the application, a drying treatment was performed to remove N-methyl-2-pyrrolidone, and a liquid crystalline polyester coating film was formed on the polyphenylene sulfide film.

Next, the liquid crystalline polyester coating film was
A heat treatment was performed for 5 minutes in a heating atmosphere of 00 ° C., and the mixture was cooled to room temperature to obtain a liquid crystalline polyester film exhibiting a golden specular reflection on a polyphenylene sulfide film.

The transmission spectrum of the film was measured with an ultraviolet-visible-near-infrared spectrophotometer V-570 manufactured by JASCO Corporation. A cholesteric film exhibiting selective reflection having a center wavelength of about 600 nm and a selective reflection wavelength bandwidth of about 110 nm was obtained. It was confirmed that a cholesteric alignment layer in which the alignment was fixed was obtained. Observation of the orientation state of the cholesteric alignment layer by a polarizing microscope and transmission electron microscopy of the cross section of the film showed that the helical axis orientation in the cholesteric phase was uniformly parallel to the film thickness direction, and the helical pitch was uniform in the film thickness direction. It was confirmed that the cholesteric orientation was formed at regular intervals. The number of spiral windings was found to be about 3 by transmission electron microscope observation.

On the obtained cholesteric alignment layer, an engraved diffraction grating film (900 engraved lines / mm) manufactured by Edmund Scientific Japan Co., Ltd. was superposed so that the liquid crystal surface and the diffraction surface faced each other. Using a laminator DX-350 manufactured by Laminex, 150 ° C, 0.3MP
a, Heating and pressurization was performed under the condition of a roll contact time of 0.5 seconds. Then, after cooling to room temperature, the ruled line diffraction grating film was removed.

When the liquid crystal surface on which the diffraction grating film was superimposed was observed, rainbow colors caused by the diffraction pattern and gold selective reflection caused by the cholesteric liquid crystal were recognized. When the same observation was performed with the surface on which the diffraction grating film was superimposed facing down, the luminance of the selective reflection caused by the cholesteric liquid crystal and the luminance of the iridescent color caused by the diffraction pattern were observed in a well-balanced manner.

The alignment state of the liquid crystal layer was observed with a polarizing microscope and the cross section of the liquid crystal layer was observed with a transmission electron microscope.
It was confirmed that a cholesteric orientation in which the helical axis orientation in the cholesteric phase was not uniformly parallel to the film thickness direction and the helical pitch was not evenly spaced in the film thickness direction was formed in the surface region of the liquid crystal layer. Was. In other regions, it was confirmed that a cholesteric orientation in which the helical axis orientation was uniformly parallel to the film thickness direction and the helical pitch was uniformly uniform in the film thickness direction was formed. He-Ne laser (wavelength 632.8 nm) perpendicular to the plane of the liquid crystal layer
Was incident, laser light was observed at an emission angle of 0 ° and about ± 35 °.

In order to further confirm the polarization characteristics, the liquid crystal layer was observed through a right circularly polarizing plate (transmitting only right circularly polarized light) under ordinary room illumination. The resulting gold reflected color was observed at the same time, and was almost the same as the brightness when observed without the polarizing plate. On the other hand, when the liquid crystal layer was observed through the left circularly polarizing plate (transmitting only left circularly polarized light), a dark field was observed, and neither rainbow-colored reflected diffracted light nor gold-colored reflected color caused by the cholesteric liquid crystal was observed. .

As described above, by transferring the diffraction pattern of the diffraction grating film to the cholesteric alignment layer having about 3 helical turns, a cholesteric liquid crystal layer having a diffractive region in the surface region was obtained. Check
In addition, it was confirmed that the liquid crystal layer functioned as a polarization diffraction element.

(Example 2) 6.42 g of methylhydroquinone bis (4- (6-acryloyloxyoxyhexyloxy) benzoic acid) ester which is a positive uniaxial nematic liquid crystal compound, and 4-cyanophenol 4- (6- (Acryloyloxyhexyloxy) benzoic acid ester to 0.
98 g, 2.60 g of a commercially available chiral dopant liquid crystal S-811 (manufactured by Roddick Co., Ltd.) were weighed and distilled and purified.
Dissolved in 90 g of methyl-2-pyrrolidone. To this solution was added 0.5 m of a fluorine surfactant S-383 (manufactured by Asahi Glass Co., Ltd.).
g, photoinitiator Irgacure 907 (Ciba-Geigy) 0.3 g, sensitizer diethylthioxanthone 0.1 g
Was coated on a polyethylene naphthalate (PEN) film (manufactured by Mitsubishi Diafoil Co., Ltd.) whose surface was rubbed with rayon cloth using a bar coater. After coating, the film was put into a clean oven set at 60 ° C., dried for 15 minutes, and then heat-treated in an oven set at 80 ° C. for 5 minutes.
Cholesteric alignment of the liquid crystal layer was completed by cooling to 50 ° C. in minutes. Next, the liquid crystal layer formed on the PEN film was put into an oven set at 50 ° C., allowed to cool to the oven set temperature in a nitrogen atmosphere having an oxygen concentration of 250 ppm or less, and then subjected to UV irradiation at that temperature. A high-pressure mercury lamp was used as a UV light source, the irradiation intensity was 120 W / cm2 at the maximum, and the integrated irradiation amount for 5 seconds of irradiation time was 135 mJ. The liquid crystal layer after irradiation was hardened to some extent and did not have the fluidity observed before hardening, but its surface hardness was lower than 6B in pencil hardness, and it was not possible to measure the exact hardness. The liquid crystal layer after UV irradiation
10 so that the rubbing direction is long along with the EN film
A cm × 3 cm rectangle was cut out, and a commercially available embossed film J52,989 (manufactured by Edmund Scientific Japan) was cut into a 12 cm × 5 cm rectangle in which the grating direction of the diffraction grating was long. The cut liquid crystal layer of the liquid crystal layer on the PEN film and the diffraction grating surface of the embossed plate film are overlapped so that they are in contact with each other, one short side is fixed with cellophane tape, and the heat laminating apparatus DX-350 ( (Made by Higashi Rami). In the case of thermal lamination, the temperature of the laminating roll is 72
C. and the moving speed of the sample was 30 mm per second. After the heat lamination, the liquid crystal layer and the embossed plate film were integrally adhered to each other to form a laminate. The laminate was cooled to room temperature, and the liquid crystal layer was irradiated with an electron beam (EB) at room temperature. The EB irradiation was performed using an EB irradiator manufactured by Eye Electron Beam Co., Ltd. at room temperature and in an atmosphere with an oxygen concentration of 0.20% at an acceleration voltage of 30 kV. After the EB irradiation, the embossed plate film was peeled off from the laminate along the film longitudinal direction. The liquid crystal layer remaining on the PEN film after EB irradiation was hardened, and its surface hardness was about 2H in pencil hardness.
The liquid crystal layer was measured with an ultraviolet-visible near-infrared spectrophotometer V manufactured by JASCO Corporation.
When the transmission spectrum was measured at -570, it was confirmed that the cholesteric orientation exhibiting selective reflection with a center wavelength of about 580 nm and a selective reflection wavelength bandwidth of about 40 nm was fixed. When the liquid crystal layer was visually observed,
Apart from the reflected light caused by the cholesteric orientation, when the film longitudinal direction is viewed at 12 o'clock, the rainbow-colored light characteristic of the diffraction grating is observed when viewed obliquely from 3 o'clock and 9 o'clock. Was done. When the liquid crystal layer was similarly observed with the surface on which the embossed plate film was superimposed facing downward, the luminance of the selective reflection caused by the cholesteric liquid crystal and the luminance of the iridescent color caused by the diffraction pattern were observed in a well-balanced manner.

The alignment state of the liquid crystal layer was observed by a polarizing microscope and a cross section of the liquid crystal layer was observed by a transmission electron microscope.
It was confirmed that a cholesteric orientation in which the helical axis orientation in the cholesteric phase was not uniformly parallel to the film thickness direction and the helical pitch was not evenly spaced in the film thickness direction was formed in the surface region of the liquid crystal layer. Was. In other regions, it was confirmed that a cholesteric orientation in which the helical axis orientation was uniformly parallel to the film thickness direction and the helical pitch was uniformly uniform in the film thickness direction was formed. The number of spiral windings was found to be 12 to 13 by transmission electron microscope observation. Further, when a He / Ne laser was vertically incident on the liquid crystal surface from the PEN film side, 0th-order and ± 1st-order diffracted lights were observed at an emission angle of 0 ° and about ± 9 °. In order to further confirm the polarization characteristics, the liquid crystal layer was observed through a left circularly polarizing plate (transmitting only left circularly polarized light) under normal room illumination. A bright yellow reflected color was observed at the same time, which was almost the same as the brightness when observed without a polarizing plate. On the other hand, when the liquid crystal layer was observed through the right circularly polarizing plate (transmitting only right circularly polarized light), a dark field was observed, and neither rainbow-colored reflected diffracted light nor yellow reflected color due to the cholesteric liquid crystal was observed.

From the above, it was confirmed that the surface region was a cholesteric liquid crystal layer having 12 to 13 helical windings in which a region having diffractive ability was formed, and that the liquid crystal layer functioned as a polarization diffraction element. It was confirmed.

[0057]

The polarization diffraction element of the present invention has both selective reflection characteristics and circular polarization characteristics due to cholesteric orientation, and diffraction characteristics due to a region exhibiting diffractive ability. An optical effect that achieves a good balance of characteristics can be obtained. In addition, since it has such an optical effect, its application range is extremely wide as a diffraction function element, and it is suitably used as an optical element such as an optical element such as a liquid crystal display, an optoelectronic element, a decoration material, and a forgery prevention element. The industrial value is extremely high.

Claims (1)

[Claims] 1. A polarizing diffraction element comprising at least a cholesteric liquid crystal layer partially having a region exhibiting diffractive power, wherein the number of spiral turns in the cholesteric orientation of the liquid crystal layer is in the range of 2 to 20 turns.