JP2002040252A - Optical sheet containing cholesteric liquid crystal layer, information recording body using the same, method for recording information and method for discriminating information - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet, comprising immobilized uniform cholesteric liquid crystal phase not getting cloudy, comparatively freely selecting chemical species of the cholesteric liquid crystal, an information recording medium using the same and methods for recording and discriminating information. SOLUTION: The optical sheet is characterized by containing a structure comprising a cholesteric liquid crystal layer, composed of a liquid crystal immobilized by a cross-linking reaction and consisting of a monodomain structure obtained by reacting a certain steroid and a liquid crystal composition containing a reactive liquid crystalline compound, formed on a substrate. Further the information recording medium using the same and the methods for recording and discriminating the information are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sheet, an information recording medium using the same, an information recording method and an information discriminating method, and more particularly to an improvement of a cholesteric liquid crystal layer used for the same.

[0002]

2. Description of the Related Art It is well known that cholesteric liquid crystalline compounds exhibit interference colors in a liquid crystal state. This color is based on light reflected by a molecular array having a spiral periodic structure. When the helical period has a molecular arrangement of P,
A wavelength width Δλ = P centered on a wavelength λ = nP (where n is the average refractive index of the liquid crystal) of light incident parallel to the helical axis.
Only light of Δn (Δn = refractive index anisotropy) is selectively reflected, and light in other wavelength ranges is transmitted. The selective reflection of light caused by the cholesteric liquid crystal is remarkable, and emits a glittering metallic glow from blue to red.
When the incident light has an incident angle θ, p ·
It is known that light having a wavelength satisfying the Bragg reflection condition of cos θ = λ / n is selectively reflected, and that when observed at an angle, a shorter wavelength color is observed and a change in color tone due to the viewing angle occurs. I have.

[0003] As the name implies, many liquid crystals have fluidity, and in order to use them as a material, some form of immobilization method is required. At present, most liquid crystal display devices that use liquid crystal materials are used in a cell state in which liquid crystal is sealed between two glass substrates.

Attempts to fix a cholesteric liquid crystal phase have been made for a long time. As a main method, JP-A-61-31721 discloses a method of dispersing a cholesteric liquid crystal composed of a polypeptide in an amorphous polymer. JP-A-2-24297 discloses a method of polymerizing a monomer having a cholesterol skeleton and fixing a liquid crystal phase at a temperature equal to or lower than the glass transition temperature (Tg) of the polymer.

[0005]

However, in the prior method, since the liquid crystal phase and the amorphous polymer phase are incompatible and have different refractive indices, light scattering occurs at the interface, and the film becomes cloudy and cholesteric. The color tone of the liquid crystal may be impaired, and the chemical species of the cholesteric liquid crystal used are limited. Further, in the latter case, chemical species that express cholesteric liquid crystal in a predetermined temperature range are limited, and even with chemical species that express cholesteric liquid crystal phase, it is extremely difficult to perform a process for uniformly expressing cholesteric liquid crystal phase. There are many. Therefore, a general-purpose cholesteric liquid crystal phase fixing technology suitable for an optical sheet has been desired.

The present invention has been made to solve the above-mentioned problems, and an optical sheet in which a uniform cholesteric liquid crystal phase that is not opaque and is fixed without relatively selecting a cholesteric liquid crystal species, and an information recording medium using the same, An object of the present invention is to provide an information recording method and an information determining method.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a reactive liquid crystal having a polymerizable functional group which undergoes a cross-linking reaction with general-purpose steroids having cholesteric liquid crystal properties. An optical sheet having a structure in which a cholesteric liquid crystal layer having a monodomic structure obtained by reacting with a reactive compound is formed on a substrate is an optical sheet in which a uniform cholesteric liquid crystal that does not become cloudy is fixed, and the above problem is solved. Was found. Since this optical sheet has a monodomic cholesteric liquid crystal layer structure, the color tone greatly depends on the viewing angle, and in the case of an optical sheet that has been subjected to liquid crystal alignment, there is a large difference in optical performance between the vertical direction and the horizontal direction in the alignment direction. In addition, it is possible to produce an optical sheet excellent in selective reflection in the infrared region,
The present inventors have found that the present invention can be used as an information recording medium, and have accomplished the present invention.

That is, the optical sheet according to the present invention comprises:
A cholesteric liquid crystal layer comprising a liquid crystal fixed by a cross-linking reaction includes a structure formed on a substrate, and the cholesteric liquid crystal layer is obtained by reacting a liquid crystal composition containing a steroid and a reactive liquid crystal compound. It is characterized by having a monodomeic structure.

Further, the optical sheet according to the present invention is characterized in that the steroids do not undergo a crosslinking reaction. Further, the optical sheet according to the present invention is characterized in that the cholesteric liquid crystal layer reacts a liquid crystal composition containing a photopolymerization initiator.

[0010] The optical sheet according to the present invention is characterized in that the cholesteric liquid crystal layer exhibits a cholesteric liquid crystal phase in a wider temperature range than the mixture of the steroids and the reactive liquid crystal compound before the reaction.

Further, in the optical sheet of the present invention, the reactive liquid crystal compound is a nematic liquid crystal having a polymerizable functional group.

In the optical sheet of the present invention, the reactive liquid crystalline compound contains a cellulose skeleton in a main chain, and a functional group selected from an alkyl group, an alkoxy group, an acryl group and a methacryl group in a side chain. A liquid crystalline compound which exhibits thermotropic liquid crystallinity at room temperature when mixed with a compound.

Further, in the optical sheet of the present invention, the weight ratio between the steroids before the reaction and the reactive liquid crystal compound is 10%.
The ratio is preferably from 0:40 to 100: 400.

Further, the optical sheet according to the present invention is characterized in that the cholesteric liquid crystal layer on the base material exhibits a color tone due to a helical structure, and the color tone changes depending on a viewing angle.

Further, the optical sheet according to the present invention is characterized in that the cholesteric liquid crystal layer on the substrate is made of cholesteric liquid crystal that has been subjected to an alignment treatment, and has a difference in optical performance between the direction parallel to the alignment axis and the direction perpendicular to the alignment axis. I do.

The optical sheet according to the present invention has a difference in optical performance between the direction parallel to the orientation axis and the direction perpendicular to the orientation axis.
The cholesteric liquid crystal layer exhibits a color tone due to the helical structure of the cholesteric liquid crystal, and the incident light at the reflection angle of 10 to 80 ° with respect to the incident light of the incident angle of 10 to 80 °
The color difference value (ΔE) between the case where the orientation axis of the liquid crystal layer is made parallel and the case where it is perpendicular to the reflection surface is 5 or more.

Further, in the optical sheet according to the present invention, the cholesteric liquid crystal layer on the substrate has a selective reflection peak of 700 to 2,000 n due to the helical structure of the cholesteric liquid crystal.
m.

The optical sheet according to the present invention is characterized in that the cholesteric liquid crystal layer on the substrate does not have a selective reflection peak at 400 to 700 nm due to the helical structure of the cholesteric liquid crystal.

The optical sheet according to the present invention is characterized in that a plastic layer is formed on a cholesteric liquid crystal layer on a substrate.

The optical sheet according to the present invention is a hologram film in which the substrate or the plastic layer has a light diffraction pattern recorded by hologram emboss or a kinegram film in which a light diffraction pattern is recorded by a diffraction grating. It is characterized by the following. Further, the optical sheet according to the present invention is characterized in that a cholesteric liquid crystal layer made of liquid crystal fixed by a crosslinking reaction is formed on the back surface of the hologram film or kinegram film on the image reproducing surface. Further, the optical sheet according to the present invention is characterized in that a cholesteric liquid crystal layer comprising a liquid crystal fixed by a crosslinking reaction is formed on a video reproduction surface of a hologram film or a kinegram film as a base material.

Further, in the information recording medium according to the present invention, in the information recording medium using the optical sheet, a selective reflection peak due to a helical structure of a cholesteric liquid crystal layer on a base material has a difference in an optical sheet plane. The difference between the selective reflection peaks is recorded as information. Further, the information recording body according to the present invention, in the information recording body using the optical sheet, in the optical sheet surface, a portion having a selective reflection peak due to the helical structure of the cholesteric liquid crystal layer on the substrate, also. The difference is recorded as information.

The information recording medium according to the present invention is characterized in that information is recorded as a bar code.

Further, the method for recording information on the information recording medium according to the present invention is directed to an optical sheet having a cholesteric liquid crystal layer composed of an unfixed liquid crystal composition containing a steroid and a reactive liquid crystal compound on a flat base material. By irradiating light by a mask exposure method, a selective reflection peak caused by a helical structure of the cholesteric liquid crystal layer on the flat base material is partially fixed. At the temperature where the selective reflection peak due to the helical structure is different from the selective reflection peak of the portion to be fixed, or at the temperature at which the cholesteric liquid crystal phase does not appear, the entire or non-fixed portion is irradiated with light and the remaining unfixed portion is fixed. And a step of fixing the whole by thermal polymerization.

In the information discriminating method for an information recording medium according to the present invention, a laser beam having a wavelength of a selective reflection peak caused by a helical structure of a cholesteric liquid crystal layer of the information recording medium is emitted to the information recording medium as a light source. Information is identified by receiving light with a light receiver that recognizes the light having the selective reflection peak wavelength out of the reflected light or transmitted light from the information recording medium and scanning the light having the selective reflection peak wavelength. And

In the information discriminating method of the present invention,
It is preferable that the selective reflection peak wavelength due to the helical structure of the cholesteric liquid crystal layer of the information recording medium is 700 to 1200 nm.

[0026]

Embodiments of the present invention will be described below. The optical sheet of the present invention is schematically illustrated in FIG. The upper diagram of FIG. 1 is a diagram showing a state before fixing the optical sheet of the present invention. A cholesteric liquid crystal layer 16 on which a liquid crystal composition comprising a steroid 12 and a reactive liquid crystal compound 14 is not immobilized is present on a substrate 10, and a plastic layer 20 is present thereon. The lower diagram in FIG. 1 shows the optical sheet 18 of the present invention after the liquid crystal is not fixed. The sheet in the state shown in the upper part of FIG. 1 is irradiated with light or ultraviolet light to cause photopolymerization, preferably in the presence of a photopolymerization initiator in the liquid crystal composition, thereby fixing the fixed cholesteric liquid crystal layer 22 having a monodomeic structure. Is formed. The optical sheet of the present invention is shown in the optical sheet 24 on which the liquid crystal thus formed is fixed. However, the plastic layer 20 may or may not be present.

Further, a sheet of a single cholesteric liquid crystal layer 22 having a fixed monodomeic structure and separated from a substrate which is easily separated may be used.

In the optical sheet of the present invention, since the steroids 12 and the reactive liquid crystal compound 14 have an affinity, the liquid crystal composition is immobilized as a cholesteric liquid crystal layer having a monodomeic structure without breaking the cholesteric liquid crystal phase. It is characterized by the ability to

First, steroids and reactive liquid crystal compounds suitably used in the present invention, a photopolymerization initiator, and formation of a cholesteric liquid crystal layer having a monodomy structure obtained by photopolymerization will be described in detail.

[0030]Steroids  In the present invention, the steroid is a cholesteric liquid crystal phase.
Is a main component for forming As steroids
Is a relatively low-molecular cholesteric liquid crystal phase
Can be widely selected. Specifically,
You.

Examples of the steroids of the present invention include ester compounds such as cholesterol alkylate, cholesterol phenylate, cholestanol alkylate, cholestanol phenylate, phytosterol alkylate, phytosterol phenylate and cholesterol halide, cholestanol halide and the like. Halides. These are used in one kind or in a mixture of two or more kinds.

As the cholesterol alkylate, cholesterol acetate, cholesterol propionate, cholesterol butyrate, cholesterol pentanate, cholesterol hexanate, cholesterol heptane, cholesterol decanate, cholesterol nanoate, cholesterol octanoate, cholesterol dodecaneate, cholesterol Millistate,
Cholesterol palmitate, cholesterol stearate, cholesterol oleate, cholesterol oleyl carbonate, cholesterol formate and the like can be mentioned.

The cholesterol phenylate includes cholesteryl benzoate.

The cholestanol alkylates include cholestanol acetate, cholestanol propionate, cholestanol butyrate, cholestanol pentanate, cholestanol hexanate, cholestanol heptanoate, cholestanol decanoate, cholestanol nanoate, Cholestanol octanoate, cholestanol dodecane, cholestanol myristate,
Cholestanol palmitate, cholestanol stearate, cholestanol oleate, cholestanol oleyl carbonate, cholestanol formate and the like.

As cholestanol phenylate, cholestaryl benzoate can be mentioned.

Phytosterol alkylates include:
Phytosterol acetate, phytosterol propionate, phytosterol butyrate, phytosterol pentanate, phytosterol hexanate, phytosterol heptanate, phytosterol decanoate, phytosterol nanoate, phytosterol octanoate, phytosterol dodecane, phytosterol myristate, phytosterol palmitate, phytosterol palmitate, phytosterol palmitate Phytosterol oleate, phytosterol oleyl carbonate,
Phytosterol formate and the like.

As phytosterol phenylate,
Phytosteryl benzoate is mentioned.

Examples of the cholesterol halide include cholesteryl fluoride, cholesteryl chloride, cholesteryl bromide, and cholesteryl iodide.

The cholestanol halide includes cholestanol fluoride, cholestanol chloride, cholestanol bromide, and cholestanol iodide.

The optical sheet of the present invention is excellent in versatility because the above-mentioned ordinary cholesteric liquid crystal steroids can be immobilized thereon.

[0041]Reactive liquid crystalline compound  In the present invention, the reactive liquid crystalline compound is
Cholesteric liquid crystal phase when mixed with
And cholesteric liquid crystal
No need to show. The mixed liquid crystal composition is light or purple.
Polymerized by irradiation with external light, and even after polymerization
Cholesteric liquid crystal phase must be maintained.

Specifically, a nematic liquid crystal having a polymerizable functional group is preferably used. The nematic liquid crystal has a cellulose skeleton in a main chain, and has an alkyl group, an alkoxy group, an acryl group in a side chain.
A liquid crystal compound which is a compound containing a functional group selected from a methacryl group and exhibits thermotropic liquid crystallinity at room temperature when mixed with a steroid is more preferable. As such a reactive liquid crystal compound, for example, UV-curable liquid crystal (trade name) manufactured by Dainippon Ink and the like is suitably used in the present invention.

[0043]Photopolymerization initiator  The photopolymerization initiator in the present invention is uniformly dissolved in the liquid crystal composition.
It is necessary that the cholesteric liquid crystal phase be retained
is there. In addition, it is decomposed by UV light irradiation to
Generate a polymerization reaction of the reactive liquid crystal compound efficiently.
Those that can occur are selected. This includes Irgaki
651, Irgacure 184, Irgacure 117
3, Irgacure 500, Irgacure 1000, Ir
Gacure 2959, Irgacure 907, Irgacure
369, Irgacure 1700, Irgacure 149,
Irgacure 1800, Irgacure 1850, Irgac
Cure 819, Irgacure 784 (Cibagaiki Co., Ltd.
Manufactured).

The optical sheet of the present invention can contain other chiral agents.

[0045]Cholesteric liquid crystal with monodomeic structure
Layer formation  Mix the steroids and a reactive liquid crystal compound in an appropriate amount,
A liquid crystal composition is obtained. This liquid crystal composition is heated from room temperature to 50 ° C.
It is preferable to develop a cholesteric liquid crystal phase within the range of
New The weight ratio of steroids to the reactive liquid crystalline compound
Is preferably from 100: 40 to 100: 400. reaction
When the amount of the liquid crystal compound is too small, the fixation of the liquid crystal becomes insufficient.
Cholesteric liquid crystal properties
Is sometimes unsatisfactory.

About 0.1 to 10 parts of the above photopolymerization initiator is dissolved in about 140 to 500 parts of the liquid crystal composition. The liquid crystal composition in which the photopolymerization initiator is dissolved is required to exhibit a uniform cholesteric liquid crystal phase similarly to the liquid crystal composition before mixing.

A liquid crystal composition in which a photopolymerization initiator is dissolved is
As it is or after dissolving in a suitable solvent, it is coated on a substrate by a casting method, a bar coating method, a screen printing method, or the like.

The substrate may be in the form of a plate or a film, and usually includes polyethylene terephthalate (PET), glass, etc., but is not particularly limited. In addition, when light needs to be transmitted through the optical sheet, it is necessary that the optical sheet be transparent or that light of a required wavelength be transmitted. However, there is no particular limitation when the optical sheet is used after being reflected. The material of the plastic layer provided on the cholesteric liquid crystal layer is the same as that of the base material, but it is required that the plastic layer be transparent or transmit light of a required wavelength. Also,
The substrate or the plastic layer of the optical sheet of the present invention includes a hologram film and a kinegram film.

The cholesteric liquid crystal phase is fixed by any one of the following methods (A) to (C).

(A) Irradiating the formed coating film with ultraviolet light,
Perform the polymerization reaction. The obtained cured liquid crystal film may be further subjected to a thermal polymerization reaction at 50 to 100 ° C. for several hours in order to complete the polymerization reaction.

(B) The liquid crystal cured film produced in (A) is overcoated with an acrylic resin or the like to produce a sheet comprising a base material / liquid crystal cured film / overcoat layer.

(C) A film is stuck on the formed coating film. In this state, light irradiation is performed in the same manner as in (A) to cure and fix the liquid crystal phase, thereby producing a sheet composed of the base material / the cured liquid crystal film / film.

The obtained liquid crystal sheet has no domain structure, is entirely uniform (monodomain), has a cholesteric liquid crystal phase immobilized by a photopolymerization reaction, and has a steroid and a reactive liquid crystal compound before the reaction. It exhibits a cholesteric liquid crystal phase in a wider temperature range than the mixture.

In the present invention, various applications are possible. In other words, using a cholesteric liquid crystal layer having a monodomeic structure, by performing an alignment treatment on an optical sheet or a liquid crystal phase in which the color tone changes according to the viewing angle, there is a difference in optical performance in the direction parallel to the direction perpendicular to the alignment axis of the cholesteric liquid crystal. An optical sheet can be produced, and an optical sheet having a selective reflection peak in an infrared region can be produced. These optical sheets may be used in combination.

Hereinafter, the above three optical sheets are classified and described in detail.
I do.Optical sheet whose color tone changes with viewing angle  In the present invention, the cholesteric liquid crystal layer has a spiral structure.
Characteristic color tone, and the color tone depends on the viewing angle.
It is possible to produce an optical sheet that changes.

The color tone of the optical sheet can be adjusted by adjusting the ratio of the steroid and the reactive liquid crystal compound or the amount of the photopolymerization initiator. This range is about 100 parts by weight of the steroids, and the reaction liquid crystalline compound 40
~ 150 parts by weight are preferred. If the amount of the reactive liquid crystal compound is less than 40 parts by weight, the polymerization reaction may be insufficient, and the stability of the cholesteric liquid crystal layer may be insufficient. On the other hand, if the amount of the reactive liquid crystalline compound is more than 150 parts by weight, color development in the visible region may be insufficient, which is not preferable. However, when it is not necessary to obtain a color tone in the visible region, and when a selective reflection peak of the cholesteric liquid crystal layer is determined in an infrared portion described later, polymerization may be performed in an amount of more than 150 parts by weight.

The optical sheet of the present invention can have a difference in optical performance between the parallel direction and the vertical direction of the alignment axis by subjecting the cholesteric liquid crystal layer to an alignment treatment. Next, the optical sheet that has been subjected to the orientation treatment will be described.

[0058]Optical sheet with orientation treatment  The alignment treatment for the cholesteric liquid crystal layer is, for example, as follows:
There are three methods. Note that the alignment treatment is performed before immobilization.
To do. The polymer liquid crystal is formed into a film.
It is difficult to develop steric liquid crystal properties.

(Alignment Treatment) A method of forming an alignment film made of rubbed polyvinyl alcohol, polyimide, or the like on a substrate, forming a liquid crystal layer thereon, and aligning the liquid crystal. A method of applying liquid crystal to a substrate, such as roll coating or bar coating, in which coating is applied so that shear is applied in one direction, and the liquid crystal is aligned. After forming a liquid crystal layer, a transparent substrate is attached to the upper surface of the liquid crystal layer, and then shear stress is applied to align the liquid crystal.

An optical sheet having a cholesteric liquid crystal layer which has been subjected to alignment treatment and fixed by any one of the above methods has a difference in optical performance between the direction parallel to the alignment axis and the direction perpendicular to the alignment axis. 2A to 2C are examples in which a difference in optical performance is caused.

For example, using the optical sheet 26 which has been subjected to the alignment treatment, the left view of FIG. 2A shows that the liquid crystal alignment axis is perpendicular to the traveling direction of the incident light 28 and the reflected light 30 is reflected. The right figure is an example in which the reflected light 32 is obtained in a state where the liquid crystal alignment axis is parallel to the traveling direction of the incident light 28. The difference in optical performance between the parallel direction and the vertical direction of the orientation axis of the oriented optical sheet of the present invention is, for example, a reflection angle of 10 with respect to an incident light of 10 to 80 °.
In the reflected light of up to 80 °, the color difference value (ΔE) when the orientation axis of the liquid crystal layer is parallel to and perpendicular to the incident-reflection surface can be 5 or more.

FIG. 2B shows reflected light when the incident light has polarization. The left figure shows the liquid crystal alignment axis perpendicular to the vibration direction of the polarized incident light 34. This is an example in which the reflected light 36 is obtained in a state where the reflected light 40 is obtained in a state where the liquid crystal alignment axis is parallel to the vibration direction of the polarized incident light 38. In the alignment-treated optical sheet of the present invention, the liquid crystal layer is caused by the helical structure of the cholesteric liquid crystal, the polarization reflectance parallel to the alignment axis of the liquid crystal layer at the selective reflection peak wavelength in the reflectance spectrum, and the alignment axis. The ratio to the vertical polarization reflectance is 1.2 or more or 0.8
The following optical sheets are possible.

FIG. 2C shows transmitted light when the incident light has polarization. The left figure shows a state where the orientation axis is perpendicular to the vibration direction of the polarized incident light 42. Is an example in which the transmitted light 44 is obtained, and the right figure is an example in which the transmitted light 46 is obtained in a state where the orientation axis is parallel to the vibration direction of the polarized incident light 42. In the alignment-treated optical sheet of the present invention, the liquid crystal layer is due to the helical structure of the cholesteric liquid crystal, the polarization transmittance parallel to the alignment axis of the liquid crystal layer at the selective reflection peak wavelength in the transmittance spectrum, and the alignment axis. Optical sheets having a ratio to the vertical polarization transmittance of 1.2 or more or 0.8 or less are possible.

Next, an optical sheet having selective reflectivity in the infrared region
Will be described.Optical sheet with selective reflection or transmission in the infrared  The optical sheet of the present invention is a liquid crystal reactive with steroids.
Cholesteric liquid crystal
When the layer is selected by the helical structure of the cholesteric liquid crystal,
Having an emission peak in the infrared region of 700 to 2000 nm
Is obtained. Optical sheet with selective reflectivity in this infrared region
Has no reflection peak at 400 to 700 nm,
It is useful for discriminating information.

As the specific reaction amount, steroids 1
The reactive liquid crystalline compound is preferably used in an amount of 150 to 400 parts by weight with respect to 00 parts by weight. If less than 150 parts by weight, the selective reflection peak of the cholesteric liquid crystal layer is out of the infrared region,
This is not preferable because it tends to shift to the visible region. On the other hand, if the amount exceeds 400 parts by weight, the cholesteric liquid crystal phase tends not to be maintained, which is not preferable.

[0066]Hologram film and kinegram fill
M  In the optical sheet of the present invention, the hologram film or the hologram film is used.
Or kinegram film can be used together
You. Hologram films use holograms to improve light interference.
Hologram embossing with projections and depressions for projection
Formed of a transparent synthetic resin film having
Layer and a light-reflective metal or metal oxide with a high refractive index
And a reflective layer. These hologram embosses
A hologram layer made of a synthetic resin film having
By laminating a reflective layer consisting of a metal deposition film,
When light is applied from the hologram layer side, it passes through the transparent resin
Incident light is reflected by the reflection layer and the emboss
To raise the hologram image by unevenness due to
Configuration.

For example, FIG. 3 is a schematic diagram of a general hologram reproducing body. The hologram film in the figure includes a support 48, a release layer 50, a protective layer 52, and a hologram layer 5.
4, a reflective layer 56 and a coat layer 58 are laminated.

As described above, the hologram layer 54 and the reflection layer 56 reflect the light transmitted through the hologram layer 54 having the hologram embossed pattern on the reflection layer 56 and reproduce the hologram image by the reflected light. By adjusting the properties of the material used for the reflective layer 56 and the reflectivity with respect to incident light, there are those commonly referred to as a fully-reflective hologram reconstructed body, a translucent hologram reconstructed body, and a transparent hologram reconstructed body.

The support 48 supports another layer to be laminated, and is peeled off from the other layer after transferring the hologram reproducing body. The support 48 has strength, heat resistance,
A material having a surface property, for example, polyethylene terephthalate, polyester, polypropylene or the like is selected. The release layer 50 is formed from the transferred hologram reproducing body to the support 4.
8 is used to facilitate peeling. Of course, a resin may be used for the release layer, but a release agent may be used.

The protective layer 52 protects the hologram layer 54, and is selected from translucent resins having performance such as abrasion resistance, stain resistance, and solvent resistance. This protective layer 52
Can be used also as a release layer by further considering the releasability from the support, or can be used also as a hologram layer by providing a hologram embossed pattern.

The coating layer 58 protects the hologram emboss and the reflection layer from abrasion and contamination by coating the hologram emboss and the reflection layer of the hologram layer 54. When it is attached to an article such as a card, it may be attached by an adhesive or the like without using a coat layer.

When the hologram is used for the optical sheet of the present invention, the optical sheet of the present invention and the hologram film are separately prepared and used, or a hologram emboss having a light diffraction pattern directly on the surface of the optical sheet is used. It is also possible to record and use it.

The hologram film used in the present invention is not limited to the above structure. FIGS. 4A to 4F show schematic examples of other hologram films. The hologram reproduction surface in FIG. 4 is all on the upper side of the figure. The material of the support 57 is the same as that of the hologram layer 54.

The hologram film is different from the hologram film in that a light diffraction pattern is recorded as a hologram by hologram embossing, whereas the kinegram film is recorded as a light diffraction pattern as a diffraction grating. A hologram can provide a three-dimensional effect, and a kinegram can provide a pearlescent effect. However, regarding the method of use, production method, and structure of the kinegram in the present invention,
The hologram can be followed.

[0075]Information recording medium, information recording method, and information
Judgment method  The optical sheet of the present invention is a color filter, a reflector,
Used as an information recording medium in addition to optical elements such as polarizers
Can be

The optical sheet of the present invention can partially fix the liquid crystal by using a mask exposure method or the like during the photopolymerization reaction, and can record information in the form of characters, characters, and bar codes. it can. In the case of the mask exposure method, an unfixed optical sheet is irradiated with light through a mask at a temperature at which the liquid crystal to be fixed exhibits a cholesteric liquid crystal phase, and first the information portion is fixed. Next, at a temperature at which the selective reflection peak due to the helical structure of the cholesteric liquid crystal layer of the information portion and the unfixed portion is different, or at a temperature not showing a cholesteric liquid crystal phase, the entire or unfixed portion is irradiated with light,
Alternatively, information can be recorded by fixing the whole by thermal polymerization. In the optical sheet of the present invention,
If necessary, various types of optical sheets described above can be used in combination.

The viewing-angle-dependent color tone of the optical sheet of the present invention can be used particularly well as an information recording medium in which color copying and duplication are difficult.

The difference in optical performance between the parallel direction and the vertical direction of the alignment axis of the liquid crystal of the optical sheet subjected to the alignment treatment is as follows.
It is extremely useful as an information recording medium, and can be used, for example, for a non-reusable easily collapsible seal. FIG. 5 shows an example of the easily collapsible seal. As can be seen from the figure, the seal-shaped optical sheet 62 that has been subjected to the orientation treatment is a steroid 1
2 is a cholesteric liquid crystal layer 60 having been subjected to an alignment treatment.
By making it weaker than the adhesion between the cholesteric liquid crystal layer 60 and the adherend, the cholesteric liquid crystal layer 60 after the alignment treatment is broken when the plastic layer 20 is peeled off once adhered to the object to be peeled off. Can be made unavailable. Once peeled off, the layer 64 has a disordered liquid crystal alignment even if it is re-adhered, so that cholesteric liquid crystallinity is not exhibited. In addition, it is needless to say that no color difference is obtained when the compound axis of the liquid crystal layer is made parallel to and perpendicular to the incident-reflective surface.

The use of the optical sheet of the present invention having selective reflectivity or selective transmittance in the infrared region is useful as an information recording medium that cannot be visually confirmed. In the optical sheet of the present invention, since the information portion has a reflection peak selectively at a specific wavelength, the selective reflection peak is detected if light is detected by a photodiode at the wavelength of the selective reflection peak and a wavelength slightly shifted therefrom. Is detected, and not detected at a slightly shifted wavelength, so that a highly reliable information discriminating method can be realized.

[0080]

The present invention will be described below with reference to examples of the present invention, but the present invention is not limited to these examples.
All parts are parts by weight.

First, an embodiment of the present invention will be described. As the steroids, general cholesteric liquid crystal compositions were selected. <Example 1> (A) Cholestanol oleate / cholesterol nonanonate / cholesteryl butyrate / cholestanol butyrate /
100 parts of steroids composed of phytostole ole,
(B) 40 parts of UCL (Dainippon Ink Kogyo Co., Ltd.) as a reactive liquid crystal compound and (C) Irgacure 149 (Ciba Specialty Chemical Co., Ltd.) as a photopolymerization initiator.
Five parts were mixed to obtain a liquid crystal composition.

The liquid crystallinity of the liquid crystal composition was observed with a polarizing microscope equipped with a heating unit. The liquid crystal composition showed a blue cholesteric layer at room temperature, and changed to blue-green-red with heating, and changed to an isotropic phase at 55 ° C. During this time, the liquid crystal phase maintained a cholesteric phase, and the liquid crystal phase had a monodomain structure as a whole.

To this liquid crystal composition, 0.1 part of 4.5 μm spacer particles was dispersed and mixed. This was sandwiched and pressed between the washed PET films. The liquid crystal layer was treated at 40 ° C. for 2 hours to obtain a monodomain state. When irradiated with ultraviolet light from a low-pressure mercury lamp at room temperature for 10 minutes, it was confirmed that the liquid crystal composition was cured by a polymerization reaction while maintaining a blue cholesteric liquid crystal phase. Further, when observation was made by heating, the optical sheet did not change in color tone even at 200 ° C. or higher, and maintained a cholesteric liquid crystal phase. In addition, a heat cycle test and a water resistance test were performed to observe the durability of the color tone. The results are summarized in Table 1.

[0084]

[Table 1]  Test item Condition Result  Heat resistance 220 ° C (uncrosslinked: 45 ° C) No color change Thermal cycle Room temperature to 150 ° C (20 cycles) No color change UV resistance Low pressure mercury lamp irradiation 12hr No color change Water resistance Room temperature 24hr immersion No color change

As can be seen from Table 1, it is understood that the optical sheet of the present invention has excellent color tone durability against heat, ultraviolet rays and water.

Next, in order to compare the optical sheet of the present invention with the prior art, the following optical sheet of Comparative Example 1 was produced. <Comparative Example 1> Instead of (B) in Example 1, a liquid crystal composition was obtained using methyl methacrylate (MMA: Tokyo Chemical Industry Co., Ltd.), which has been conventionally used as a crosslinking agent. Although the liquid crystal composition exhibited a blue color tone, no cholesteric liquid crystal phase was observed as a result of observation with a polarizing microscope.

The liquid crystal composition was formed into a cell in the same manner as in Example 1 and irradiated with light to obtain a liquid crystal cured product. The cured liquid crystal had a cloudy, faint blue color, and was observed with a polarizing microscope. As a result, it was observed that the MMA polymer part and the liquid crystal part of the cured liquid crystal were separated. Further, when a heating observation was performed, the liquid crystal composition was transformed into an isotropic phase in the range of 40 to 60 ° C., and the liquid crystal property was lost.

Therefore, it is understood that the cured liquid crystal of Comparative Example 1 is unstable. This is because the presence of a cross-linking agent does not result in a monodomeic structure, and it can be seen that it is difficult to produce an optical sheet exhibiting cholesteric liquid crystallinity over a wide temperature range as in the present invention using the conventional technique.

Next, the amount of the reactive liquid crystalline compound of Example 1 was changed to 60 to 140 parts, and an optical sheet of Example according to the present invention was similarly produced. Table 2 summarizes the results.

[0090]

[Table 2]

Each of the liquid crystal compositions and the cured liquid crystal had a monodomain structure.

As can be seen from Table 2, in the present invention, cholesteric liquid crystallinity is maintained even at 200 ° C. or higher, which is much higher than the liquid crystal phase-isotropic phase transition temperature.

[0093]Quantitative ratio of steroids to reactive liquid crystalline compounds  Steroids and reactive liquid crystallinity in the optical sheet of the present invention
The relationship between the compound ratios is as shown in FIG. Fig. 6
100 parts of steroids, reacting liquid crystalline compound
Light curing is possible with more than 40 parts, and less than 400 parts.
It turns out that it shows a steric liquid crystal property.

It is clear from FIG. 6 and Table 2 that the color tone of the optical sheet of the present invention can be adjusted by the quantitative ratio of the steroid and the reactive liquid crystalline compound.
As can be seen from FIG. 6, the color tone of the liquid crystal composition is blue-green-yellow-orange when the amount of the reactive liquid crystalline compound is 150 parts or less with respect to 100 parts of the steroid. Is difficult to obtain, an optical sheet showing a color tone in the range of 40 to 150 parts can be obtained.

Next, the total light reflection spectrum and the total light transmission spectrum of the optical sheets of Examples 4, 5 and 6 are shown in FIG. 7 and FIG. In addition, the spectrum of the following pearl agent mica titanium is also shown for comparison.

Ir201 (Mica titanium mica having a yellow interference light) Ir211 (Merck titanium mica having a red interference light) Ir221 (Merck titanium mica having a blue interference light) Ir231 (Green interference light Titanium mica manufactured by Merck)

As can be seen from FIGS. 7 and 8, the liquid crystal cured products of Examples 4, 5, and 6 according to the present invention are different from ordinary pearl agents and selectively reflected only at specific wavelengths, as compared with pearl agents. It can be seen that there is a peak.

[0098]Addition of chiral agent  Next, the change in color tone due to the amount of chiral agent added
investigated. Chiral agents usually have a unique helical molecular arrangement
Added as a mixed liquid crystal for the purpose of forming morphology
However, this makes it possible to adjust the color tone. In the above embodiment
100 parts of steroids used and reactive liquid crystal compound 100
Parts, 5 to 5 parts of a photopolymerization initiator, 0.1 to 5.0%
(0.2 to 10 parts) with the following chiral agent
FIG. 9 shows the diffuse transmission spectrum when the addition is performed. Chemical 1
Among the chiral agents, R811 (Merck, right-handed
The diffuse transmission spectrum when the compound of
In FIG. (A), S811 (Merck, left-handed spiral)
The figure below shows the diffuse transmission spectrum when a compound is added.
It is shown in (B). In R and S, the absolute configuration of the asymmetric carbon is
different.

[0099]

Embedded image

As is clear from FIG. 9, when R811 was added (A), the color tone shifted from the short wavelength side to the long wavelength side, and when S811 was added, the color tone shifted from the long wavelength side to the short wavelength side. It turns out that there is a tendency. Therefore, it can be seen that the color tone of the optical sheet can be controlled also by the type and amount of the chiral agent.

[0101]Reaction temperature  Next, the reaction temperature when polymerizing the liquid crystal composition was examined.
Debated. FIG. 10 shows light at 20 to 60 ° C. in the fourth embodiment.
3 shows a diffuse transmission spectrum of a polymerized liquid crystal cured product. Figure
As can be seen from FIG. 10, peaks at specific wavelengths above 45 ° C.
The tendency to disappear was seen. Therefore, the liquid crystal composition
It is found that a reaction temperature of less than 45 ° C. is preferable for the product.
However, in general, the temperature is preferably 50 ° C. or lower in the present invention.

In FIG. 10, the change in the specific wavelength peak depending on the reaction temperature is small, but it can be changed depending on the liquid crystal composition.

The reaction was not cured unless the reaction time was 5 minutes or more.

[0104]Cholesteric liquid crystal layer thickness  Next, the thickness of the cholesteric liquid crystal layer of the optical sheet,
That is, the cell gap was examined. Example 4
Similarly, changing the particle size of the sir particles to 7.5 and 12.5 μm
An optical sheet was produced. 4.5 to 12.5 μm in FIG.
3 shows a diffuse transmission spectrum of an optical sheet having a layer thickness of. FIG.
As can be seen from Fig. 1, the effect of the layer thickness is almost
Did not.

[0105]Viewing angle dependence of color tone  The color tone of the optical sheet of the present invention is remarkable depending on the viewing angle.
It has changing properties. About the optical sheet of the example,
Tone change is measured by Murakami Color Research Laboratory
It was measured by CMS-3. The measurement is white from the incident angle of 45 °.
Color light is incident on the sample surface, and reflected light
The measurement was performed in the range of -20 ° to 70 ° (see FIG. 12).
See). The color tone was evaluated by Lab chromaticity. FIG. 12 shows an embodiment.
The results of Examples 1, 2, and 4 are shown in FIG.
FIG. 12 shows, as a comparison, the blue interference light of the pearl agent.
Mica titanium (Ir221, manufactured by Merck) was shown.
As can be seen from FIGS.
The optical sheet changes color tone greatly depending on the viewing angle
You can see that In contrast, titanium mica (Ir221
(Blue)) shows that there is little change in color tone depending on the viewing angle.

Next, the alignment-treated optical sheet is described.
Examples will be described.There is a difference in optical performance between the parallel direction and the vertical direction of the alignment axis.
Optical sheet  The following optical sheets were produced as examples of the present invention. <Example 7> (A) Cholestanol oleate / cholesterol na
Nonate / Cholesteryl butyrate / Cholestanol butyrate / F
100 parts of steroids composed of citrate ole,
(B) UCL (Dainippon Ink) as a reactive liquid crystalline compound
Industrial Co., Ltd.) and (C) a photopolymerization initiator.
Lugacure 149 (Ciba Specialty Chemical)
5 parts were mixed to obtain a liquid crystal composition.

This liquid crystal composition was placed on a black film by 100
Coating was performed using a μm thick applicator. This was irradiated with ultraviolet light from a low-pressure mercury lamp for 10 minutes under a nitrogen atmosphere at room temperature to carry out a reaction, thereby obtaining an optical sheet. Before and after the light irradiation, the orientation of the liquid crystal was observed under crossed Nicols, and it was confirmed that the orientation of the liquid crystal was in the coating direction.

Next, an optical sheet was prepared by a method of dissolving the cured liquid crystal and orienting it when forming a film. <Test Example> The liquid crystal composition of Example 7 was dissolved in chloroform, formed into a film by a casting method, and measured in the same manner as in the example. However, no anisotropy was observed in the plane of the liquid crystal sheet.

Therefore, it can be seen that it is difficult to produce an optical sheet having a difference in optical performance between the direction parallel to the orientation axis and the direction perpendicular to the orientation axis without rubbing.

Next, an optical sheet was prepared by changing the amount of the reactive liquid crystalline compound. <Embodiments 8 and 9> (B) described in Embodiment 7 was replaced by 1
A liquid crystal sheet was prepared in the same manner as in Example 7 except that the amount was changed to 40 parts or 160 parts.

Next, the optical properties of the optical sheet of the present invention were evaluated. For a liquid crystal cured product, the color tone change with respect to the alignment direction is measured by the Gakuen Sekisui Kagaku Kenkyusho GCM
It measured in S-3. In the measurement, white light was made incident on the sample surface from an incident angle of 45 °, and reflected light corresponding thereto was measured in a reflection angle range of −20 ° to 70 °. The case where the liquid crystal orientation direction was parallel to the measurement surface (the surface including the incident light beam and the reflected light beam) and the case where it was perpendicular were measured. The color tone was evaluated by Lab chromaticity.

FIG. 14A shows the results of Example 7, FIG. 14B shows the results of Example 8, and FIG. 15 shows the results of Example 9. As is clear from the figure, the color tone when the liquid crystal orientation direction is perpendicular to the measurement surface is larger than when the measurement surface is parallel to the liquid crystal orientation direction. The color difference value ΔE reached 5 or more.

Next, the polarized light reflectance parallel to the orientation axis of the liquid crystal layer at the selective reflection peak wavelength in the reflectance spectrum of the liquid crystal layer (the left figure in FIG. 2B) and the polarized light reflectance perpendicular to the orientation axis (FIG. 2B). FIG. 2 (B) right figure) was measured, and the ratio was determined.

Also, the polarized light transmittance parallel to the orientation axis of the liquid crystal layer at the selective reflection peak wavelength in the transmittance spectrum of the liquid crystal layer (left figure in FIG. 2C) and the polarized light transmittance perpendicular to the orientation axis (FIG. 2 (C), right figure), and the ratio was determined. The results are shown in the table below.

[0115]

[Table 3]  Example Polarized reflectance (%) Polarized light transmittance (%) Polarized light transmittance Polarized light transmittance Vertical Parallel Vertical Parallel ratio  7 45 20 60 75 2.25 1.25 8 45 22 60 77 2.05 1.28 9 45 22 60 76 2.05 1.27

As is clear from Table 3, the optical sheet of the present invention has a polarized light reflectance ratio (vertical / parallel) of 1.2 or more (0.8 or less when its reciprocal is taken) and a polarized light transmittance of 0.8 or less. ratio
(Parallel / vertical) is 1.2 or more (reciprocal is 0.8 or less)
It turns out that it becomes. It is understood that the present optical sheet having a clear difference in optical performance between the parallel direction and the vertical direction of the orientation axis of the polarization reflectance or the polarization transmittance is useful as an information recording medium.

Next, an optical sheet having selective reflectivity in the infrared region.
Examples will be described below.Including cholesteric liquid crystal layer with selective reflectivity in the infrared
Optical sheet  <Example 11> (Preparation of liquid crystal sheet) (A) Cholestanol oleate / cholesterol
Nanonate / cholesteryl butyrate / cholestanol butyrate /
Steroids consisting of phytostole oleate 10
0 parts and UCL (Dainichi) as a reactive liquid crystalline compound (B)
200 parts of this ink industry as (C) photopolymerization initiator
, Irgacure 149 (Ciba Specialty Chemi
(Cal Co., Ltd.) in an amount of 5 parts to obtain a liquid crystal composition.

The liquid crystallinity of the liquid crystal composition was observed with a polarizing microscope equipped with a heating unit. Liquid crystal composition 1
Showed a cholesteric phase at room temperature. When the temperature was raised at a rate of 5 ° C./min while observing, the phase changed to an isotropic phase at 55 ° C. During this time, the liquid crystal phase maintained a cholesteric phase, and the liquid crystal phase had a monodomain structure as a whole.

This liquid crystal composition was applied on a washed PET film to a thickness of 50 μm by a bar coater method. The mixture was treated at 40 ° C. for 2 hours in a nitrogen atmosphere to obtain a liquid crystal layer in a monodomain state. Thereafter, the reaction was carried out by irradiating a low-pressure mercury lamp with ultraviolet light for 10 minutes at room temperature under a nitrogen atmosphere. Further, thermal polymerization was performed at 60 ° C., and the reaction was completed to obtain an optical sheet. Observation of the optical sheet with a polarizing microscope confirmed that the cured liquid crystal was cured by a polymerization reaction while maintaining the cholesteric liquid crystal phase. Further, when a heating observation was performed, the optical sheet maintained a cholesteric liquid crystal phase even at 200 ° C. or higher.

(Transmission / Reflection Spectrum of Optical Sheet) The transmission spectrum of visible light / near infrared light of the optical sheet was 400
It was measured in the range of ２０００2000 nm. For the measurement, a Hitachi Spectrophotometer U3410 equipped with an integrating sphere was used. The transmission spectrum of the liquid crystal sheet did not have absorption in the visible region of 400 to 700 nm, and the sheet was colorless and transparent. In the near infrared region, a sharp absorption peak at 910 nm was confirmed. On the other hand, also in the reflection spectrum, there was no reflection in the visible region, and the color was colorless. In the reflection spectrum in the near infrared region, 910 n
m showed a sharp peak.

Next, an optical sheet according to the prior art will be described. <Comparative Example 3> A liquid crystal composition was obtained using methyl methacrylate (MMA: Tokyo Chemical Industry Co., Ltd.) instead of (B) in Example 11. Although the liquid crystal composition exhibited a blue color, it was observed with a polarizing microscope.
It was confirmed that the A polymer part and the liquid crystal part were separated. Further, when a heating observation was performed, it was found that the liquid crystal composition was 4
In the range of 0 to 60 ° C., a transition to an isotropic phase occurred, and liquid crystallinity was lost.

Therefore, it is understood that it is difficult to produce an optical sheet exhibiting a cholesteric liquid crystal phase in a wide temperature range by the conventional technique.

Next, an optical sheet was prepared in the same manner as in Example 11 except that the amount of the reactive liquid crystalline compound was changed to 160 to 360 parts. Table 4 shows the results.

[0124]

[Table 4]

Each of the liquid crystal compositions and the cured liquid crystal had a monodomain structure. In the present invention, it can be seen that cholesteric liquid crystal properties are maintained even at 200 ° C. or higher, which is much higher than the liquid crystal phase-isotropic phase transition temperature.

FIG. 16 shows diffuse transmission spectra of the optical sheets of Examples 10, 12 and 13, and FIG. 17 shows Examples 11 and 1.
4 shows diffuse transmission spectra of optical sheets Nos. 4 and 15. The optical sheet of the present invention has an infrared region (700 to 2000 n).
It can be seen that there is a sharp reflection peak at the specific wavelength of m).

FIG. 18 shows the diffuse reflection spectra of the optical sheets of Examples 11, 14, and 15. The optical sheet of the present invention has the same infrared region (700 to 2000 nm) as in FIG.
Has a sharp reflection peak at a specific wavelength. Further, the optical sheet of the present invention has a thickness of 400 to 700 nm.
It can be seen that there is no reflection peak in the visible region.

Next, the present inventor tried to produce an optical sheet using a hologram film as a base material. An optical sheet having a hologram layer above and a liquid crystal layer below (Example 16) and an optical sheet having a liquid crystal layer above and a hologram layer below so that the image recorded on the hologram can be seen from above (Example 16). Example 17) was produced.

<Example 16> The base material of Example 12 was replaced with P
Similarly, an optical sheet having selective reflectivity in the infrared region of the present invention was obtained by changing the ET film to a hologram film on which an image was recorded and providing a liquid crystal layer on the back side of the hologram image recording surface.

FIG. 19A shows a schematic configuration of an optical sheet using the hologram film of Example 16. The hologram reproducing body in the figure has a hologram layer 54 having a hologram emboss, a reflective layer 56, and a cholesteric liquid crystal layer 68 having a monodomaic structure fixed below a transparent hologram sheet 66 on which a coat layer 58 is laminated. It is laminated. In the present embodiment, the hologram layer 66 also functions as the release layer 55 and the protective layer 56 in FIG.

The visible light 70 incident from the outside of the hologram sheet 66 is transmitted through the hologram layer, partially reflected by the reflection layer 58 provided in the hologram sheet 66 to become reflected light 72a, and partially transmitted and transmitted light. 74a.
The hologram sheet 66 raises the hologram image by refracting the reflected light 72a by the hologram emboss of the hologram layer and causing it to interfere. In fact, the optical sheet of the present invention could confirm a hologram image.

On the other hand, in the lower layer of the hologram sheet 66, there is a cholesteric liquid crystal layer 68 having a fixed monodomy structure having a selective reflection peak at a specific wavelength in the near infrared region. Therefore, the infrared incident light 76 having the selective reflection peak wavelength
Is reflected by the cholesteric liquid crystal layer 68 and the reflected light 7
8a is detected. In addition, infrared incident light 8 of other wavelengths
0 transmits through the fixed cholesteric liquid crystal layer 68, and the transmitted light 82a is detected. In fact, it was confirmed that the optical sheet of the present invention exhibited a sharp reflection peak at 1160 nm in the reflection spectrum in the near infrared region.

<Example 17> The base material of Example 12 was replaced with P
Similarly, an optical sheet having selective reflectivity in the infrared region of the present invention was obtained by changing the ET film to a hologram film on which an image was recorded and providing a liquid crystal layer on the image recording surface of the hologram.

FIG. 19B is a schematic configuration of an optical sheet using the hologram film of the seventeenth embodiment. The hologram reproducing body shown in the figure includes a hologram layer 54 having a hologram emboss, a reflective layer 56, and a cholesteric liquid crystal layer 68 having a monodomic structure fixed on an upper layer of a transparent hologram sheet 66 on which a coat layer 58 is laminated. It is laminated.

The visible light 62 incident from outside the fixed cholesteric liquid crystal layer 68 passes through the hologram layer, and is partially reflected by the reflection layer 58 of the hologram sheet 66 to become reflected light 72b, and partially transmitted. Transmitted light 74
b. The hologram sheet 66 raises the hologram image by refracting and interfering the reflected light 72b with the hologram emboss of the hologram layer. In fact, the optical sheet of the present invention could confirm a hologram image.

On the other hand, in the upper layer of the hologram sheet 66, there is a fixed cholesteric liquid crystal layer 68 having a monodomic structure having a selective reflection peak at a specific wavelength in the near infrared region. Therefore, the infrared incident light 76 having the selective reflection peak wavelength
Is reflected by the cholesteric liquid crystal layer 68 and the reflected light 7
8b is detected. In addition, infrared incident light 8 of other wavelengths
0 transmits through the fixed cholesteric liquid crystal layer 68, and the transmitted light 82b is detected. In fact, it was confirmed that the optical sheet of the present invention exhibited a sharp reflection peak at 1160 nm in the reflection spectrum in the near infrared region.

Next, light having a selective reflection peak in the infrared region
Information recording method using information sheet and information recording medium
An example will be described.Information recording medium having selective reflectivity in infrared region and information recording method  <Example 18> Information recording body in optical sheet of the present invention
Can directly record normal characters and characters
It can also be recorded in the form of a barcode, etc.
Wear.

The information recording method in the form of a bar code is shown in FIG.
0 is shown. First, ultraviolet rays were irradiated on the unfixed optical sheet 88 of Example 13 through a mask mold 84 having a barcode exposure section 86 at a temperature of 40 ° C., which indicates a cholesteric liquid crystal phase lower than the liquid crystal phase-isotropic phase transition temperature. And the photosensitive part 9
0 is fixed. Next, at a temperature 50 ° C. higher than the liquid crystal phase-isotropic phase transition temperature, the entirety of the optical sheet 92 in which only the fixed portion 96 is partially fixed is irradiated with ultraviolet light, and the entirety including the unfixed portion 94 is irradiated. Is immobilized. By doing so, it is possible to obtain an information recording medium having a selective reflection peak at about 1300 nm in the information recording portion of the barcode and having no selective reflection peak in the other portion and having no visually recognizable barcode. .

Next, light having a selective reflection peak in the infrared region
An example of a discrimination method using a learning sheet will be described.
You.Information determination method  <Embodiment 19> FIG. 21 shows a case where the information recording medium of the embodiment 18 is used.
Of an information discriminating method of a type for detecting reflected light
You.

An information recording medium in which white polyethylene terephthalate 106 is used as the base material in Example 18 will be described as an example.

According to this method, in the information recording medium of Example 18 having a selective reflection peak at about 1300 nm, a bar code cannot be visually confirmed.
By using a semiconductor laser 98 capable of switching at / 1400 nm and using a photodiode 100 capable of detecting 1100 to 1500 nm as a light receiver, information recorded on the information recording body 102 can be detected.

For example, if the semiconductor laser 98 is 1300n
When the laser beam 110 is emitted, the laser beam 110 is selectively reflected at the information recording unit 108, but is not reflected on the information unrecorded portion 1.
At 04, it is hardly reflected. When the semiconductor laser 98 emits light having a wavelength of 1400 nm, the laser beam 110 is transmitted to the information recording section 108 and the information unrecorded section 1.
Both 04 are not reflected very much. Therefore, bar code information can be determined by scanning the reflected light 112 with the photodiode. At this time, 14
The 00 nm laser light is not always necessary, but is useful for highly accurate information discrimination. Table 5 shows the relationship between the resulting light source wavelength and the information recording medium.

[0143]

[Table 5]  Light source Information unrecorded area Information recorded area  Visible region--1300 nm-Detection (obtains strong reflected light) 1400 nm--

<Embodiment 20> FIG. 22 shows an embodiment of an information discriminating method of the type which detects transmitted light using the information recording medium of the embodiment 18.

An information recording medium in which transparent polyethylene terephthalate 116 is used as the base material of Example 18 will be described as an example.

According to this method, the information recording medium obtained in Example 18 cannot visually confirm the barcode, but uses a semiconductor laser 98 that can switch between 1300 nm and 1400 nm as a light source, and 1100-15
By using the photodiode 100 capable of detecting 00 nm, information recorded on the information recording body 114 can be detected.

For example, if the semiconductor laser 98 is 1300n
m, the laser beam 92 is emitted from the information recording unit 1.
At 08, the transmittance decreases due to selective reflection caused by the helical structure of the cholesteric liquid crystal layer.
At 04, it is transmitted almost as it is. Also,
When the semiconductor laser 98 emits light of 1400 nm, both the information recording unit 108 and the information non-recording unit 104 are transmitted almost as it is. Therefore, the transmitted light 11
By scanning 8 with the photodiode 100, bar code information can be determined. At this time, a laser beam of 1400 nm is not always necessary, but is useful for highly accurate information discrimination. Table 6 shows the relationship between the resulting light source wavelength and the information recording medium.

[0148]

[Table 6]  Light source Information unrecorded area Information recorded area  Visible range--1300 nm-Detection (weak transmitted light) 1400 nm--

[0149]

According to the optical sheet of the present invention, the optical sheet has a structure in which a cholesteric liquid crystal layer composed of a liquid crystal fixed by a crosslinking reaction is formed on a substrate, and the cholesteric liquid crystal is reacted with a steroid and a liquid crystal. Since it has a monodomeic structure obtained by reacting a composition containing a hydrophilic compound, it is possible to provide an optical sheet in which a uniform cholesteric liquid crystal phase that does not become cloudy is fixed, and has excellent versatility.

According to the present invention, the steroids do not need to undergo a crosslinking reaction, and general-purpose steroids can be used.

With the above optical sheet, it is possible to provide an optical sheet characterized in that the cholesteric liquid crystal layer on the base material exhibits a color tone due to a helical structure, and the color tone changes depending on the viewing angle.

Further, by performing the alignment treatment of the liquid crystal,
An optical sheet having a difference in optical performance between the direction parallel to the orientation axis and the direction perpendicular to the orientation axis can be provided.

Further, it is possible to provide an optical sheet having a cholesteric liquid crystal layer on a base material having a selective reflection peak at 700 to 2,000 nm due to a helical structure of the cholesteric liquid crystal.

The optical sheet of the present invention is also useful as an information recording medium, and can provide an information recording method and a discriminating method using the same.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical sheet of the present invention.

FIG. 2 is an explanatory diagram showing the orientation of the optical sheet of the present invention.

FIG. 3 is a view showing a structure of a general hologram film.

FIG. 4 is a diagram showing a structure of a general hologram film.

FIG. 5 is a diagram showing an example of the information recording medium of the present invention.

FIG. 6 is a diagram showing the relationship between the amount of steroids and the amount of reactive liquid crystal compound added in the optical sheet of the present invention.

FIG. 7 shows Examples 4 and 5 of the optical sheet of the present invention.
6 is a diagram showing a reflection spectrum of No. 6. FIG.

FIG. 8 is an optical sheet according to Examples 4 and 5 of the present invention.
6 is a diagram showing a transmission spectrum of No. 6. FIG.

FIG. 9 shows a chiral agent (R) in the optical sheet of the present invention.
811 is a diagram showing the relationship between the added amount of S811) and the transmission spectrum.

FIG. 10 is a diagram showing a relationship between a reaction temperature and a transmission spectrum in the optical sheet of the present invention.

FIG. 11 is a diagram showing the relationship between the thickness of the cholesteric liquid crystal layer and the transmission spectrum in the optical sheet of the present invention.

FIG. 12 shows an optical sheet according to the first embodiment of the present invention.
It is a figure which shows the viewing angle dependence of 2 and 4 color tones.

FIG. 13 is a view showing the viewing angle dependency of the color tone of Example 5 in the optical sheet of the present invention.

FIG. 14 is a diagram illustrating an orientation-treated optical sheet of the present invention.
It is a figure which shows the orientation dichroism of Examples 7 and 8.

FIG. 15 is a diagram illustrating an orientation-treated optical sheet of the present invention.
FIG. 14 is a diagram showing the orientation dichroism of Example 9.

FIG. 16 is an optical sheet according to a tenth embodiment of the present invention.
It is a figure which shows the diffuse transmission spectrum of 12-13.

FIG. 17 shows Example 11 of the optical sheet of the present invention.
It is a figure which shows the diffuse transmission spectrum of 14-15.

FIG. 18 shows an optical sheet according to Example 11 of the present invention.
It is a figure which shows the diffuse reflection spectrum of 14-15.

FIG. 19 is a diagram showing an optical sheet using the hologram of the present invention as a base material.

FIG. 20 is a diagram showing an information recording method of the present invention.

FIG. 21 is a diagram showing a reflection type information determination method of the present invention.

FIG. 22 is a diagram showing a transmission type information discriminating method of the present invention.

[Explanation of symbols]

Reference Signs List 10 base material 12 steroids 14 reactive liquid crystalline compound 16 cholesteric liquid crystal layer not fixed 18 optical sheet not fixed with liquid crystal 22 cholesteric liquid crystal layer with fixed monodomeic structure 24 optical sheet with fixed liquid crystal 26 alignment treatment Optical sheet 28 Incident light 30, 32, 36, 40 Reflected light 34, 42 Polarized incident light 44, 46 Transmitted light 60 Oriented cholesteric liquid crystal layer 62 Oriented optical sheet 64 Layer with misaligned liquid crystal 48 Support 50 Release layer 52 Protective layer 54 Hologram layer 56 Reflective layer 57 Support 58 Coating layer 66 Transparent hologram sheet 68 Immobilized cholesteric liquid crystal layer 84 Mask type 86 Exposure unit 88 Unfixed optical sheet 90 Photosensitive portion 92 Partially fixed Optical sheet 94 Unfixed part 96 Fixed Min 98 1300 nm / 1400 nm switchable semiconductor laser 100 photodiodes capable of detecting 1100-1500 nm 102,114 information recording medium 104 information unrecorded part 108 information recording part 106 white polyethylene terephthalate sheet (base material) 116 transparent polyethylene terephthalate sheet (base) Material) 110 Incident laser light 112 Reflected light 118 Transmitted light

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13 102 G02F 1/13 102 500 500 G03H 1/22 G03H 1/22 // C08L 101: 00 C08L 101: 00 F-term (reference) 2H048 AA01 AA06 AA11 FA04 FA12 FA22 2H049 AA02 AA12 AA43 AA56 AA60 AA64 BA02 BA42 BA43 BC02 BC04 2H088 EA62 GA03 GA17 MA06 2K008 AA04 AA15 CC03 EE01 FF12 HH02HH13A006

Claims (22)

[Claims] 1. A liquid crystal composition comprising a structure in which a cholesteric liquid crystal layer made of liquid crystal fixed by a crosslinking reaction is formed on a substrate, wherein the cholesteric liquid crystal layer contains steroids and a reactive liquid crystal compound. An optical sheet having a monodomeic structure obtained by reacting 2. The optical sheet according to claim 1, wherein the steroid does not undergo a crosslinking reaction. 3. The optical sheet according to claim 1, wherein the cholesteric liquid crystal layer is obtained by reacting a liquid crystal composition containing a photopolymerization initiator. 4. The optical sheet according to claim 1, wherein the cholesteric liquid crystal layer exhibits a cholesteric liquid crystal phase in a wider temperature range than a mixture of a steroid and a reactive liquid crystalline compound before the reaction. An optical sheet characterized by the above-mentioned. 5. The optical sheet according to claim 1, wherein the reactive liquid crystalline compound is a nematic liquid crystal having a polymerizable functional group. 6. The optical sheet according to claim 1, wherein the reactive liquid crystalline compound contains a cellulose skeleton in a main chain and is selected from an alkyl group, an alkoxy group, an acrylic group, and a methacryl group in a side chain. An optical sheet comprising a liquid crystalline compound having a functional group and exhibiting thermotropic liquid crystallinity at room temperature when mixed with a steroid. 7. The optical sheet according to claim 5, wherein the weight ratio between the steroids before the reaction and the reactive liquid crystal compound is from 100: 40 to 100: 400. 8. The optical sheet according to claim 1, wherein the cholesteric liquid crystal layer on the substrate has a color tone due to a helical structure, and the color tone changes depending on a viewing angle. 9. The optical sheet according to claim 1, wherein the cholesteric liquid crystal layer on the base material is made of an alignment-treated cholesteric liquid crystal, and the cholesteric liquid crystal layer has an optical axis between the parallel direction and the vertical direction of the alignment axis. An optical sheet characterized by a difference in performance. 10. The optical sheet according to claim 9, wherein
As a difference in optical performance between the parallel direction and the vertical direction of the alignment axis, the cholesteric liquid crystal layer exhibits a color tone due to the helical structure of the cholesteric liquid crystal, and the reflection angle is 10 to 80 with respect to incident light having an incident angle of 10 to 80 °. An optical sheet having a color difference value (ΔE) of 5 or more when the orientation axis of the liquid crystal layer is parallel to and perpendicular to the incident-reflection surface in the reflected light of °. 11. The optical sheet according to claim 1, wherein the cholesteric liquid crystal layer on the substrate has a selective reflection peak at 700 to 2000 nm due to a helical structure of the cholesteric liquid crystal. Optical sheet. 12. The optical sheet according to claim 11, wherein the cholesteric liquid crystal layer on the substrate has a thickness of 400 to 700 n.
An optical sheet, wherein m has no selective reflection peak due to a helical structure of a cholesteric liquid crystal. 13. The optical sheet according to claim 1, wherein a plastic layer is formed on the cholesteric liquid crystal layer on the base material. 14. The optical sheet according to claim 1, wherein the base material or the plastic layer is a hologram film in which an optical diffraction pattern is recorded by hologram emboss or a light diffraction pattern is recorded by a diffraction grating. An optical sheet characterized by being a kinegram film. 15. The optical sheet according to claim 14, wherein a cholesteric liquid crystal layer comprising a liquid crystal fixed by a crosslinking reaction is formed on the back surface of the hologram film or the kinegram film on the image reproducing surface. Characteristic optical sheet. 16. The optical sheet according to claim 14, wherein a cholesteric liquid crystal layer made of liquid crystal fixed by a crosslinking reaction is formed on an image reproduction surface of a hologram film or a kinegram film. Optical sheet. 17. An information recording medium using the optical sheet according to claim 1, wherein a selective reflection peak caused by a helical structure of a cholesteric liquid crystal layer on a substrate has a difference in an optical sheet plane. An information recording material, comprising: a difference between the selective reflection peaks recorded as information. 18. An information recording medium using the optical sheet according to claim 1, wherein the optical sheet has a selective reflection peak in the plane of the optical sheet due to a helical structure of a cholesteric liquid crystal layer on a substrate. Has a part and a part without,
An information recording body characterized in that the difference is recorded as information. 19. The information recording medium according to claim 17, wherein bar code information is recorded. 20. The information recording method for an information recording medium according to claim 17, wherein the cholesteric liquid crystal comprises an unfixed liquid crystal composition containing a steroid and a reactive liquid crystal compound on a flat base material. The optical sheet having a layer is irradiated with light by a mask exposure method,
The step of partially fixing the selective reflection peak caused by the helical structure of the cholesteric liquid crystal layer on the flat base material, the selective reflection peak caused by the helical structure of the non-fixed cholesteric liquid crystal layer on the flat base material, A process of irradiating the whole or the non-immobilized portion with light at a temperature at which the selective reflection peak of the portion to be immobilized at the selective reflection peak is different, or a temperature at which a cholesteric liquid crystal phase is not expressed, or An information recording method comprising two steps of fixing the whole by polymerization. 21. The information discriminating method according to claim 17, wherein a laser beam having a wavelength of a selective reflection peak caused by a helical structure of a cholesteric liquid crystal layer of the information recording body is used as a light source. Scanning the light having the selective reflection peak wavelength by receiving the light with the light receiving device that recognizes the light having the selective reflection peak wavelength out of the reflected light or transmitted light emitted from the information recording medium and obtained from the information recording material. An information discriminating method characterized in that information is identified by: 22. The information discriminating method according to claim 21, wherein a selective reflection peak wavelength caused by a helical structure of the cholesteric liquid crystal layer of the information recording medium is 700 to 1200 nm.