JP2008040512A - Recording/displaying medium and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording/displaying medium in which the thickness of a liquid crystal layer can be kept constant and the uneven thickness of the liquid crystal layer or the uneven concentration (an unevenly color-developed state) of a liquid crystal compound due to flow of the liquid crystal compound can be prevented and which can display a uniform and beautiful picture. <P>SOLUTION: The recording/displaying medium includes: a base material 1; the liquid crystal layer 3 which is formed on the base material 1 and contains a cholesteric liquid crystal compound; a protective layer 4 formed on the liquid crystal layer 3; and a partition wall 2 formed between the base material 1 and the protective layer 4. The partition wall 2 contains another cholesteric liquid crystal compound which is different from the cholesteric liquid crystal compound contained in the liquid crystal layer 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rewritable and heat-sensitive recording display medium capable of recording and displaying in a specific color or full color and a method for manufacturing the same.

  Color photographs and color copies are known as recording materials that can record full color and cannot be rewritten. Rewritable recording materials that are not full color include thermal recording materials containing long-chain alkyl carboxylic acid derivatives such as behenic acid, optical recording materials using photochromic compounds such as spiropyran derivatives, and other memory such as magnetism and magneto-optical. The material is known.

  Until now, recording materials have not achieved both full color and rewritable characteristics. Certainly, some display materials change the display, such as TV and liquid crystal display, and there are full-color ones, but they can be used as thin cards that fit in your wallet or display images stably without power. It was not possible to use it instead of recording material.

  In recent years, rewritable full-color recording has been achieved by a new method using a liquid crystalline compound. JP-A-11-281945 and JP-A-2000-227772 disclose reversible thermosensitive recording media using the method. A recording medium having a spacer in the heat-sensitive recording layer is disclosed.

  However, since the spacer used in the above publication is a spherical particle such as silica, the thickness of the liquid crystal layer and the deviation of the liquid crystal compound concentration due to the flow of the liquid crystal compound cannot be sufficiently prevented, so that the spacer cannot be visually determined. There was also a problem that the size of the spacer and the installation density were restricted.

  In view of the above-described conventional problems, the present invention can keep the thickness of the liquid crystal layer constant and can prevent unevenness of the thickness of the liquid crystal layer and the concentration of the liquid crystal compound (colored state) due to the flow of the liquid crystal compound. It is an object of the present invention to provide a recordable display medium capable of display and a manufacturing method thereof.

  It is another object of the present invention to provide a recording display medium that is not restricted by the size of the partition walls, the installation density, and the like, and a method for manufacturing the same.

  It is another object of the present invention to provide a recording display medium that can be used as an anti-counterfeit medium and a method for manufacturing the same.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

  That is, the first recording display medium of the present invention has a substrate, a liquid crystal layer containing a cholesteric liquid crystal compound on the substrate, and a protective layer on the liquid crystal layer, and the substrate and the protective layer. The partition includes a cholesteric liquid crystal compound, and the cholesteric liquid crystal compound contained in the partition is different from the cholesteric liquid crystal compound contained in the liquid crystal layer. .

  The second recording display medium of the present invention is a recording display medium comprising a substrate, a liquid crystal layer containing a cholesteric liquid crystal compound on the substrate, and a protective layer on the liquid crystal layer, wherein the liquid crystal It has a forgery prevention part containing a cholesteric liquid crystal compound different from the cholesteric liquid crystal compound contained in the layer.

  Further, the method for producing a recording display medium of the present invention comprises a step of coating a liquid crystal layer with an organic solvent solution of a cholesteric liquid crystal compound on a substrate, and a step of coating and forming a protective layer on the liquid crystal layer. It is characterized by having.

  Since the first recording display medium of the present invention has a partition between the substrate and the protective layer, the thickness of the liquid crystal layer can be kept constant, and the thickness of the liquid crystal layer and the deviation of the liquid crystal compound concentration (coloring state) due to the flow of the liquid crystal compound Can be prevented, and a uniform and clean display is possible. Furthermore, since the partition contains a cholesteric liquid crystal compound, if the cholesteric liquid crystal compound contained in the partition and the cholesteric liquid crystal compound contained in the liquid crystal layer are the same, there is no restriction on the size, density, etc. of the partition, If they are different, they can also be used as an anti-counterfeit medium.

  Further, the second recording display medium of the present invention has a forgery preventing part containing a cholesteric liquid crystal compound different from the cholesteric liquid crystal compound contained in the liquid crystal layer, and therefore can be suitably used as a forgery preventing medium.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  First, the first recording display medium of the present invention will be described.

  FIG. 1 is a schematic sectional view showing an example of the first recording display medium of the present invention. In FIG. 1, 1 is a base material, 2 is a partition, 3 is a liquid crystal layer containing a cholesteric liquid crystal compound, 4 is a protective layer, and 5 is a lipophilic layer.

  As the substrate 1, a polymer film, a thin glass plate, a metal plate, or the like is used, but at least one of the substrate 1 and the protective layer 4 needs to be transparent so that at least a part of light is transmitted. is there. Further, as will be described later, when light is used for writing or erasing a record, it is desirable that either one absorbs the light. Although the thickness of the base material 1 is not specifically limited, 5 micrometers-2 mm are preferable.

  As shown in FIG. 1B, when the lipophilic layer 5 is provided between the base material 1 and the liquid crystal layer 3, the surface of the base material 1 becomes easy to become familiar with the cholesteric liquid crystal compound. 1 can be uniformly formed, and the thickness of the liquid crystal layer 3 can be further increased. This is particularly effective when the liquid crystal layer 3 is formed by applying an organic solvent solution of a cholesteric liquid crystal compound onto the substrate 1.

  The method for forming the oleophilic layer 5 is not particularly limited. For example, the lipophilic layer 5 can be formed by applying an adhesive resin such as polyisobutylene on the substrate 1. In addition, a base material 1 such that a lipophilic filler such as lipophilic smectite or lipophilic particles is directly applied on the base material 1 or dispersed in a resin such as an acrylic resin so that the filler protrudes from the surface. It can form by apply | coating on. As a coating method, a spin coating method, a reverse roll coating method, a gravure coating method, or the like can be used. The thickness of the lipophilic layer 5 is not particularly limited, but is preferably 0.1 μm to 100 μm. In addition, when base material 1 itself has lipophilicity, it is not necessary to form a lipophilic layer separately.

  The partition wall 2 is made of a transparent resin containing a cholesteric liquid crystal compound, and is provided between the substrate 1 and the protective layer 4.

  The cholesteric liquid crystal compound contained in the partition walls 2 may be the same as or different from the cholesteric liquid crystal compound contained in the liquid crystal layer 3. Further, only the cholesteric liquid crystal compound contained in some partition walls 2 is different from the cholesteric liquid crystal compound contained in the liquid crystal layer 3, and the cholesteric liquid crystal compounds contained in other partition walls 2 are added to the liquid crystal layer 3. It may be the same as the cholesteric liquid crystal compound contained. When both are the same, the liquid crystal layer 3 and the partition wall 2 exhibit the same color. Therefore, even if the partition wall has a size that can be visually confirmed (which can be confirmed with the naked eye, approximately 100 μm or more), Can be recorded and displayed in a uniform color, and the size and density of the partition walls are not restricted. On the other hand, if the two are different, the liquid crystal layer 3 and the partition 2 may exhibit different colors even at the same temperature. Therefore, if the partition 2 has a size that can be visually confirmed, it can be used as a forgery prevention medium. Of course, even when the partition wall 2 has a size that cannot be visually confirmed, it can be used as an anti-counterfeit medium as long as it can be enlarged and confirmed with a magnifying glass, a mapping device, or the like.

  The content ratio of the cholesteric liquid crystal compound in the partition walls 2 is not particularly limited, but is preferably 10 parts by weight to 200 parts by weight with respect to 100 parts by weight of the resin constituting the partition walls 2 in order to develop the same color as the liquid crystal layer.

  The shape of the partition wall 2 is not particularly limited, and may be any of a plate shape, a column shape, and the like, but in order to sufficiently prevent the thickness of the liquid crystal layer 3 and the concentration of the liquid crystal compound due to the flow of the liquid crystal compound, a plate shape is preferable. Those fixed to the substrate 1 are more preferable. Moreover, in order to improve the orientation of the liquid crystal layer 3, those having a smooth surface are preferable.

  The pattern for forming the partition wall 2 is not particularly limited, and examples include a stripe shape as shown in FIG. 2A and a lattice shape as shown in FIG. When the cholesteric liquid crystal compound contained in the partition wall 2 and the liquid crystal layer 3 is different and used as a forgery prevention medium, the character pattern, figure pattern, symbol pattern, etc. shown in FIG. Good. Furthermore, for example, a character pattern may be formed in a stripe pattern, and only a partition wall 2 constituting the character pattern may contain a cholesteric liquid crystal compound different from the cholesteric liquid crystal compound contained in the liquid crystal layer 3.

The size, density, etc. of the partition walls may be set as appropriate. For example, when plate-like partition walls are provided in a stripe shape, the partition wall height is 3 μm to 55 μm, and the partition wall widths and intervals are in the following ranges. It is preferable to do this.
(1) When the cholesteric liquid crystal compounds contained in the partition walls and the liquid crystal layer are the same Width: 5 μm to 1 mm, Interval: 5 μm to 5 mm
(2) When the cholesteric liquid crystal compounds contained in the partition walls and the liquid crystal layer are different i) When not used as an anti-counterfeit medium Width: 5 μm to 5 mm, Interval: 100 μm or more, preferably 100 μm to 5 mm
ii) When used as an anti-counterfeit medium that can be visually confirmed Width: 100 μm to 5 mm, Interval: 100 μm or more, preferably 100 μm to 5 mm
iii) When used as an anti-counterfeit medium that cannot be visually confirmed a) When not allowing the partition walls to be visually confirmed Width: 5 μm to 50 μm, Interval: 5 μm to 5 mm
b) When the liquid crystal layer cannot be visually confirmed Width: 5 μm to 5 mm, Interval: 5 μm to 50 μm

  If the height of the partition wall 2 is larger than the thickness of the liquid crystal layer 3, the contact area between the protection layer 4 and the partition wall 2 is large, so that the adhesion of the protection layer 4 is improved. In order to sufficiently improve the adhesion of the protective layer 4, it is preferable that the height of the partition wall 2 is 0.5 μm to 5 μm larger than the thickness of the liquid crystal layer 3.

  Further, when at least the surface of the partition wall 2 has oil repellency, the liquid crystal separation on the surface of the partition wall 2 is improved. Therefore, the cholesteric liquid crystal compound is less likely to remain on the partition wall 2 when the liquid crystal layer 3 is formed, and the adhesion between the partition wall 2 and the protective layer 4 is improved. In addition, even when the partition walls 2 are provided in a lattice shape as shown in FIG. 2B, the cholesteric liquid crystal compound easily enters the region surrounded by the partition walls 2. This is particularly effective when the liquid crystal layer 3 is formed by applying an organic solvent solution of a cholesteric liquid crystal compound onto the substrate 1.

  The partition wall 2 having oil repellency can be formed of, for example, a fluorine-containing additive-containing resin, a fluorine group-containing resin, a mixed resin of a fluorine group-containing resin and another resin, or the like. Further, after forming the partition wall 2 having no oil repellency, the oil repellency layer may be formed by coating these resins on the surface of the partition wall 2 or treating the surface with a fluorine-based additive.

  Examples of the resin that constitutes the partition wall 2 include those shown below, in which the resin itself is photosensitive, the resin itself is not photosensitive, but can be patterned using a photosensitive resin, screen printing, a printer, etc. And the like that can directly draw the partition wall.

[The resin itself has photosensitivity]
<Photosensitive resin>
So-called photoresist material is a resin, and when it is irradiated with specific light using a mask pattern, depending on whether it receives light or not, a difference in solubility occurs in a developer typified by an alkaline solution, A resin having the property that the same pattern as the mask or the reverse pattern remains undissolved can be used. Further, a resin that is removed by decomposition by electron beam irradiation or the like may be used instead of a liquid such as a developer. Specific examples include polyimide-based, novolak-based, phenol-based, epoxy-based, styrene-based, acrylic-based resins, and the like, and liquid and film-like resins can be used.

<Polymerized by addition of photopolymerization initiator>
Specifically, resin components such as urethane acrylate, epoxy acrylate, ester acrylate, acrylate, epoxy, and vinyl ether can be used.

  These may be monomers or oligomers, and may be used as a mixture of two or more types, or various additives may be mixed. For example, when a urethane acrylate oligomer is used as the urethane acrylate, a monofunctional or polyfunctional acrylate monomer, a photopolymerization initiator, various additives, and the like can be added.

  As the photopolymerization initiator, benzophenone-based, acetophenone-based, peroxide-based, iodonium salt, sulfonium salt and other cationic systems can be used. As additives, polymerization retarders, thermal polymerization inhibitors, fillers, surface modifiers and the like can be used. Moreover, you may add a pigment and dye as a coloring agent.

[The resin itself is not photosensitive, but can be patterned using a photosensitive resin]
Any resin that can be removed at the same time as developing the photosensitive resin or that can be removed by a different developer or method from the developed photosensitive resin without destroying the developed photosensitive resin pattern. Such a resin may be used. For example, when a photosensitive resin that can be developed with an alkaline aqueous solution is used, an alkali-soluble polyimide resin, an acrylic resin, or the like can be used.

[Those that can draw partition walls directly by screen printing, printers, etc.]
It is not particularly limited as long as it can form a partition wall having a desired height, for example, an evaporation-drying ink that is dried and solidified by evaporation of a volatile solvent in the ink, and oxygen is absorbed into the ink and dried. Either solidified oxidation polymerization type ink, two-component reactive ink that is reactively cured by mixing a curing agent, or ultraviolet curable ink that is cured by irradiation with ultraviolet rays can be used.

  The method for forming the partition wall 2 is not particularly limited, and examples thereof include printing such as silk screen and flexographic printing, drawing with an ink jet printer, photolithographic technique, and transfer.

  The liquid crystal layer 3 may be a layer made of only a cholesteric liquid crystal compound, or may be a layer in which a cholesteric liquid crystal compound is dispersed in a binder resin. Moreover, the liquid crystal layer 3 can contain additives such as pigments and antioxidants, and by containing a dichroic dye, a cholesteric liquid crystal compound that does not show a reflected color in the visible region can also be used. The content of these additives is preferably 10% by weight or less based on the cholesteric liquid crystal compound. The thickness of the liquid crystal layer 3 is not particularly limited, but is preferably 3 μm to 50 μm.

  The method for forming the liquid crystal layer 3 is not particularly limited, and examples thereof include a method in which a cholesteric liquid crystal compound is heated to a molten state and cast onto the substrate 1. In addition, as a method that does not require heating to a molten state, a method of forming the liquid crystal layer 3 by dissolving a cholesteric liquid crystal compound in an organic solvent, applying the solution on the substrate 1, and then drying to remove the organic solvent. Is mentioned.

  The application method is not particularly limited, and general methods such as spin coating, bar coating, reverse roll coating, and gravure coating can be used. The organic solvent is not particularly limited as long as it can dissolve the cholesteric liquid crystal compound, and examples thereof include toluene, xylene, tetrahydrofuran, and methylene chloride.

  The organic solvent may be used at least in an amount capable of dissolving the cholesteric liquid crystal compound, but in order to obtain the liquid crystal layer 3 utilizing the metallic luster that is characteristic of the cholesteric reflection color, the concentration of the cholesteric liquid crystal compound is as low as possible. Higher is preferred. Specifically, although it varies depending on the combination of the cholesteric liquid crystal compound and the organic solvent to be used, it is generally preferable to use in the range of 100 parts by weight to 1500 parts by weight with respect to 100 parts by weight of the cholesteric liquid crystal compound.

  Alternatively, the cholesteric liquid crystal compound can be converted into an ink or mixed with a general ink to form the liquid crystal layer 3 by printing. The printing method is not particularly limited, and general methods such as offset printing, letterpress printing, silk printing, and flexographic printing can be used, and printing methods such as drawing and transfer using an inkjet printer can also be used.

  As the protective layer 4, synthetic resin such as acrylic resin, polyamide resin, polyimide resin, polyethersulfone resin, polyetherimide resin, acrylic urethane resin, polyester resin, polyolefin resin, ultraviolet curable resin, etc. An inorganic material such as a siloxane compound, an organic / inorganic hybrid material such as organosiloxane, a glass plate, or the like can be used, and a material excellent in heat resistance, flexibility, and adhesion to the liquid crystal layer 3 may be selected as appropriate.

  The method for forming the protective layer 4 is not particularly limited. For example, the material is applied by a spin coating method, a reverse roll coating method, a gravure coating method, or the like, or in the case of a resin film, a glass plate, or the like. It is formed. Although the thickness of the protective layer 4 is not specifically limited, The thickness in the upper part of the partition 2 is preferably 1 μm to 2 mm.

  The cholesteric liquid crystal compound contained in the partition wall 2 and the liquid crystal layer 3 is not particularly limited, but is a liquid crystal state that develops color according to the heating temperature and maintains the developed state by rapidly cooling from the temperature (color Are preferred).

  Examples of the cholesteric liquid crystal compound that develops color according to the heating temperature in the liquid crystal state and maintains the color developed state upon rapid cooling from the temperature include the compounds shown in the following i) to iv).

i) Dibasic acid dicholesteryl ester Specific examples include dibasic acid dicholesteryl ester represented by the following general formula (I).
_{YO-CO (CH 2) o} -R- (CH 2) p CO-OY ...... (I)
(In the formula, Y represents a cholesterol residue obtained by removing a hydroxyl group bonded to cholesterol from cholesterol, R is any group shown in the following (a) to (k), and o and p are the same or Differently, it represents an integer of 1 to 20. In the following (f), l represents an integer of 2 to 20.)

  ii) A cholesteric liquid crystalline compound having a molecular weight of 2000 or less and a glass transition temperature of 35 ° C. or more.

  The molecular weight of this compound is preferably 500-1500, more preferably 700-1200, and the glass transition temperature is preferably 50 ° C. or higher, more preferably 70-110 ° C.

Particularly preferred cholesteric liquid crystal compounds include compounds represented by the following general formula (II).
Z-O-CO-Q-CO-O-Z '(II)
Wherein Z and Z ′ each independently represent a cholesteryl group, a hydrogen atom or an alkyl group, Q represents a divalent hydrocarbon group having 2 to 20 carbon atoms, and at least one of Z and Z ′ is cholesteryl. Represents a group)

Examples of the divalent hydrocarbon group include groups represented by the following general formula (III).
— (CH ₂ ) _q —C≡C—C≡C— (CH ₂ ) _r — (III)
(Wherein q and r are each independently an integer of 1 or more, provided that the sum of q and r does not exceed 30)

  Preferred examples include 10,12-docosadiin dicarboxylic acid dicholesteryl ester, eicosane dicarboxylic acid dicholesteryl ester, 10,12-pentacosadiin dicarboxylic acid cholesteryl ester, dodecadicarboxylic acid dicholesteryl ester, 12,14-hexacosa. And diindicarboxylic acid dicholesteryl ester.

  iii) A mixture comprising at least two kinds of cholesteryl ester compounds and having a reflection peak in a liquid crystal state other than the visible range or not taking a liquid crystal state.

  Such a mixture exhibits a temperature range that is different from the liquid crystal temperature range exhibited by the cholesteryl ester compound alone, and the fixed reflection wavelength region is also different.By appropriately setting the compound to be mixed and the mixing ratio, the liquid crystal temperature range, The fixed reflection wavelength region can be arbitrarily controlled. As a result, the color can be fixed at a temperature lower than that of the compound alone. In addition, even in the case of a mixture of compounds that cannot fix the color, the temperature range different from the liquid crystal temperature range shown by the single substance is shown, and the fixed reflection wavelength region is also different, so that the color can be fixed. Become.

  Examples of the mixture include a mixture of dicholesteryl ester compounds, a mixture of a dicholesteryl ester compound and a monocholesteryl ester compound, a mixture of a compound that can fix a color and a compound that cannot fix a color, and a mixture of compounds that cannot fix a color. However, at least one compound other than the compound that cannot fix the color develops color according to the heating temperature in the liquid crystal state, and maintains the colored state by rapidly cooling from the temperature, that is, the color is changed. A compound to be immobilized is preferable.

Although it does not specifically limit as a dicholesteryl ester compound, For example, dibasic acid dicholesteryl ester is mentioned, Specifically, the dibasic acid dicholesteryl ester represented with the following general formula (IV) is mentioned, s is When the number is odd, the compound can fix the color, and when s is even, the compound cannot fix the color.
YO—CO (CH ₂ ) _s —O—R′—O— (CH ₂ ) _s CO—OY (IV)
(In the formula, Y represents a cholesteryl group, R ′ represents p-phenylene or 4,4′-biphenylene, and s represents a number of 1 to 20)

Moreover, as a monocholesteryl ester compound, the compound represented by the following general formula (V) is mentioned. This is a compound that cannot fix or hardly fix color.
YO—CO (CH ₂ ) _t —O—R′—OH (V)
(In the formula, Y represents a cholesteryl group, R ′ represents p-phenylene or 4,4′-biphenylene, and t represents a number of 1 to 20)

  Among these, a mixture of dibasic acid dicholesteryl esters represented by the general formula (IV), that is, a mixture of a compound capable of fixing the color and a compound capable of fixing the color, two represented by the general formula (IV) Of the basic acid dicholesteryl ester, a mixture of a compound capable of fixing the color and the monocholesteryl ester represented by the general formula (V) is preferable.

  Although it does not specifically limit as a mixing ratio, When mixing 2 types of compounds, it is preferable that both weight ratio is 1: 0.8-1.2. Moreover, it is preferable to contain 20% by weight or more, more preferably 40% to 60% by weight of a compound capable of fixing the color. By setting such a mixing ratio, the liquid crystal temperature range and the reflection wavelength range can be widened.

  As a mixing method, a conventionally known method can be used. For example, a compound to be mixed is dissolved in a solvent that dissolves such as methylene chloride, and the solvent is distilled off, followed by vacuum drying. A powdery mixture can be obtained.

  iv) A cholesteric liquid crystal containing a superstructure substance having at least one group capable of intermolecular hydrogen bonding, a group having a steroid skeleton, and an alkylene group having 3 to 20 carbon atoms.

  Here, the superstructure material is a type of compound having a supramolecular structure, that is, an assembly having a structure having a geometric order due to the interaction of weak forces acting between molecules, specifically hydrogen bonds. It is a substance that forms the body (self-organization, self-assembly).

  The group capable of intermolecular hydrogen bonding is not particularly limited, and examples thereof include a carboxyl group, a hydroxyl group, an amide group, an amino group, an imino group, a nitrilo group, and a nitrogen-containing heterocyclic group such as a pyridyl group and an imidazolyl group. Aminopyridyl group, uracil group and the like.

  In addition, the intermolecular hydrogen bond to be formed is not particularly limited, but carboxyl groups, hydroxyl groups, amide groups, nitrogen-containing heterocyclic groups such as carboxyl groups and pyridyl groups, hydroxyl groups and pyridyl groups, etc. Examples include an intermolecular hydrogen bond formed by a heterocyclic group having nitrogen, a carboxyl group and a nitrilo group, a diaminopyridyl group and a uracil group.

  In addition, the group having a steroid skeleton is not particularly limited, but from cholesterol, a cholesterol residue obtained by removing a hydroxyl group bonded thereto from dicholesterol, a dihydrocholesterol residue obtained by removing a hydroxyl group bonded thereto from dihydrocholesterol, cholic acid Cholic acid residue obtained by removing hydroxyl group bonded to it, β-sitosterol residue obtained by removing hydroxyl group bonded to β-sitosterol, α-spinner obtained by removing hydroxyl group bonded to α-spinasterol Examples thereof include sterol residues, and among these, since various colors can be exhibited, cholesterol residues and dihydrocholesterol residues are preferable.

  Moreover, carbon number of an alkylene group is 3-20, Preferably it is 3-11. If the number of carbon atoms exceeds 20, the viscosity in the superstructure liquid crystal state may increase and the response to temperature changes may be delayed. If the number of carbon atoms is less than 3, the cholesteric reflection is caused by a rapid cooling operation from the superstructure liquid crystal state. It is not preferable because it is difficult to fix the color.

  The molecular weight of the superstructure material is preferably 385 to 900, more preferably 500 to 800. If the molecular weight exceeds 900, the viscosity in the liquid crystal state of the superstructure may increase and the response to temperature changes may be delayed. If the molecular weight is less than 385, the cholesteric reflection color is fixed by a rapid cooling operation from the liquid crystal state of the superstructure. There is a risk that it will be difficult.

  Specific examples of the superstructure material include the following cholesteryl ester compounds.

(In the formula, Y represents a cholesterol residue obtained by removing a hydroxyl group bonded thereto from cholesterol, n represents an integer of 3 to 20, and X represents —OH, —Me, —OMe, —NO _2. , -Cl, -Br, -I, -CN, m represents an integer of 0 to 2, and when m = 2, they may be the same or different substituents.)

  Specific examples of the cholesteric liquid crystal include the compounds represented by the general formulas (1) to (1 ″), the compounds represented by the general formulas (2) to (2 ″), and the general formula (3). And supramolecular compounds formed by a combination of n being an even number or n being an even number and an odd number, and those having the same carbon number n may be used alone, or those having different carbon numbers n may be combined. In the latter case, the liquid crystal temperature and the wavelength range that can be fixed can be adjusted by appropriately setting the carbon number n and the mixing ratio.

  In addition, a combination of a compound represented by any one of the above general formulas (1) to (4) and a compound represented by any one of the above general formulas (5) to (5 ″), the above general formulas (1) to ( 4) Supramolecules formed by a combination of a compound represented by any one of the above and 4,4′-bipyridyl, or a combination of a compound represented by any one of the above general formulas (5) to (5 ″) and terephthalic acid Compounds. In these cases, the liquid crystal temperature and the wavelength range that can be fixed can be adjusted by appropriately setting the mixing ratio of the two. The mixing ratio of the two is not particularly limited, but it is preferable that the hydrogen donor part and the hydrogen acceptor part are mixed at a molar ratio of 1: 2 to 2: 1.

  Next, the second recording display medium of the present invention will be described.

  3A and 3B are diagrams showing an example of the second recording display medium of the present invention, in which FIG. 3A is a top view and FIG. 3B is a cross-sectional view taken along line AA of FIG. In FIG. 3, 1 is a base material, 3 is a liquid crystal layer containing a cholesteric liquid crystal compound, 4 is a protective layer, and 6 is a forgery prevention part.

  As shown in FIG. 3, the second recording display medium of the present invention has a forgery preventing unit 6 containing a cholesteric liquid crystal compound different from the cholesteric liquid crystal compound contained in the liquid crystal layer 3. In FIG. 3, the forgery prevention unit 6 is provided between the protective layer 4 and the liquid crystal layer 3 in which a cholesteric liquid crystal compound is dispersed in a transparent binder resin. In the case where the liquid crystal layer 3 is sandwiched, forgery prevention part 6 may be provided on the glass plate (protective layer 4).

  The forgery prevention unit 6 uses the resin that can directly draw the partition wall by the above-described screen printing, printer, etc., as the resin constituting the partition wall of the first recording display medium of the present invention, printing such as silk screen, flexographic printing, inkjet printer, etc. It can be formed by drawing. Although the content ratio of the cholesteric liquid crystal compound in the forgery prevention unit 6 is not particularly limited, in order to cause the same color development as the liquid crystal layer, 10 parts by weight to 200 parts by weight with respect to 100 parts by weight of the resin constituting the forgery prevention unit 6 Is preferred. Moreover, the shape, pattern, etc. of the forgery prevention part are not particularly limited as long as they can be visually confirmed during color development.

  The material, thickness, formation method, and the like of the base material 1, the liquid crystal layer 3, and the protective layer 4 are the same as those of the first recording display medium of the present invention, and thus description thereof is omitted. In addition, an oleophilic layer may be provided between the substrate 1 and the liquid crystal layer 3 as in the first recording display medium of the present invention.

  The recording display medium of the present invention can perform recording (writing) and recording display by partial or total heating. For the heating, various methods such as a thermal head, a heating roll, and a laser beam are possible. Heating that requires temperature control to the liquid crystal temperature range is controlled by controlling the temperature of the thermal head, heating roll, etc., adjusting the laser beam intensity and spot diameter, or heating the whole to a certain temperature. This is possible by lowering the temperature to the required temperature with a flat metal plate or rubber plate.

  On the other hand, in order to fix the coloration of the cholesteric liquid crystal compound, it is necessary to rapidly cool the liquid crystal below its glass transition temperature. For this purpose, the entire liquid is immersed in a refrigerant or a cooled atmosphere. A method, a method of bringing a part into contact with a cooled head, or the like is employed.

  The recording display medium of the present invention can be used as, for example, a card, an overhead project sheet, a label, a ticket, a member for forming a forgery prevention unit used by being attached to these, a forgery prevention medium, etc. Accordingly, a back layer or the like may be further provided. For example, in the case of a label, a mount is provided on the back surface of the recording display medium via an adhesive layer. In the case of a magnetic ticket, a magnetic recording layer made of a binder and a ferromagnetic powder is provided instead of the mount.

FIGS. 4 and 5 are flowcharts for explaining an example of the authenticity determination method when the cholesteric liquid crystal compounds contained in the partition walls 2 and the liquid crystal layer 3 are different from each other and used as a forgery prevention medium. The liquid crystal layer 3 has a stripe-shaped partition wall 2, the liquid crystal layer 3 is blue at T ₁ ° C, green at T ₂ ° C (T ₁ > T ₂ ), and the partition 2 is blue at T ₂ ° C. As an example, the medium in which the color erasing temperature of the part ₃ is T ₃ ° C (T ₂ > T ₃ ) and the color erasing temperature of the part 2 is T ₄ ° C (T ₃ > T ₄ ) An example of the authenticity determination method of the present invention will be described.

As shown in FIG. 4, first, heated to T ₁ ° C., rapidly cooled after dropped to T ₂ ° C.. If authentic, exhibit portions of the liquid crystal layer 3 is green at T ₂ ° C., part of the partition wall 2 exhibits a blue color, when quenched from this state, the blue stripes to a green background color is fixed. Therefore, it is a counterfeit product if it is not colored or if it is colored but its state is not fixed. Even if it is fixed, if it is determined by visual inspection or color difference, spectrum measurement, etc. that the pattern is not striped, the ground color is not green, etc. It is a product.

Next, it is heated again to T ₁ ° C and gradually cooled. If the pattern is erased, it is genuine. Since the recording display medium of the present invention is rewritable, the authenticity determination can be made any number of times.

The method shown in FIG. 5 is the same as the method shown in FIG. 4 until the pattern is fixed and the authenticity is determined. After that, it is heated to T ₄ ° C., and when the blue color of the partition wall 2 disappears and becomes transparent, it is genuine, and otherwise it is a counterfeit product. Next, it is heated to T ₃ ° C., and if the green part of the partition wall 2 disappears and the whole becomes transparent, it is genuine, and if not, it is a forged product. When the medium with T ₃ = T ₄ is genuine, it is genuine if the pattern is erased by heating to T ₃ ° C, and it is a counterfeit if it is not erased.

<Example 1>
The recording display medium shown in FIG.

  On a black PET film (base material 1) having a thickness of 188 μm, a partition wall forming coating solution (urethane acrylate resin: liquid crystal compound (Y represents a cholesterol residue)): toluene: photopolymerization initiator by spin coating. : A polymerization retarder mixed at a weight ratio of 100: 100: 500: 5: 1), and exposure and development are performed through a mask to form a line-shaped partition wall 2 having a width of 50 μm and a height of 10 μm. Was formed with a partition wall spacing of 300 μm.

On top of this, a toluene solution of the following liquid crystal compound (Y represents a cholesterol residue) was applied to form a liquid crystal layer 3 having a thickness of 7 μm in the recesses between the partition walls 2.
Y—O—CO— (CH ₂ ) ₈ —C≡C—C≡C— (CH ₂ ) ₈ —CO—O—Y

  Further, a protective layer 4 was formed by applying a mixed solution of ultraviolet curable acrylic resin: methyl ethyl ketone (weight ratio 1: 1) by spin coating and curing by ultraviolet irradiation. The thickness of the protective layer 4 was about 5 μm on the partition wall 2 (about 8 μm on the liquid crystal layer 3).

  When this recording display medium was heated to 120 ° C., the temperature was lowered to 115 ° C., and when immersed in cold water from this state, the whole surface was fixed to blue.

<Example 2>
A recording display medium was prepared in the same manner as in Example 1 except that the liquid crystal compound in the partition wall forming coating solution was the following liquid crystal compound (Y represents a cholesterol residue) and the partition wall width was 200 μm.

  When this recording display medium was once heated to 125 ° C. and then cooled to 115 ° C. and then immersed in cold water and rapidly cooled, the partition 2 portion was fixed in green and the liquid crystal layer 3 portion was fixed in blue. Thereafter, when the mixture was again heated to 125 ° C. and gradually cooled, the whole became transparent.

<Example 3>
The recording display medium shown in FIG. 3 was produced.

  The partition wall-forming coating solution of Example 1 was applied to a black PET film (base material 1) having a thickness of 188 μm by spin coating, and was cured by irradiating the entire surface with ultraviolet rays to form a liquid crystal layer 3 having a thickness of 10 μm. Formed. On top of that, a character pattern was printed by a screen printing method using the partition wall forming coating solution of Example 2 and cured with ultraviolet rays to form a forgery preventing portion 6 having a thickness of 5 μm. On top of this, a protective layer 4 having a thickness of 10 μm was formed in the same manner as in Example 1.

  When this recording display medium was heated to 125 ° C. and then lowered to 115 ° C., a character pattern could be recognized.

It is a schematic sectional drawing which shows an example of the 1st recording display medium of this invention. It is a partial top view which shows an example of the 1st recording display medium of this invention. It is a figure which shows an example of the 2nd recording display medium of this invention. It is a flowchart explaining an example of the authenticity determination method using the recording display medium of this invention. It is a flowchart explaining the other example of the authenticity determination method using the recording display medium of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 2 Partition 3 Liquid crystal layer 4 Protective layer 5 Lipophilic layer 6 Forgery prevention part

Claims (8)

  A recording display medium comprising a substrate, a liquid crystal layer containing a cholesteric liquid crystal compound on the substrate, and a protective layer on the liquid crystal layer, and having a partition between the substrate and the protective layer, A recording display medium, wherein the partition wall contains a cholesteric liquid crystal compound, and the cholesteric liquid crystal compound contained in the partition wall is different from the cholesteric liquid crystal compound contained in the liquid crystal layer.   The recording display medium according to claim 1, wherein at least a surface of the partition wall has oil repellency.   The recording display medium according to claim 1, further comprising an oleophilic layer between the substrate and the liquid crystal layer.   The recording display medium according to claim 1, wherein a height of the partition wall is larger than a thickness of the liquid crystal layer.   The recording display medium according to claim 1, wherein the partition wall is fixed to the base material.   A recording display medium comprising a substrate, a liquid crystal layer containing a cholesteric liquid crystal compound on the substrate, and a protective layer on the liquid crystal layer, wherein the cholesteric liquid crystal compound is different from the cholesteric liquid crystal compound contained in the liquid crystal layer A recording display medium comprising a forgery preventing part containing a liquid crystal compound.   The cholesteric liquid crystal compound is a cholesteric liquid crystal compound that develops a color according to a heating temperature in a liquid crystal state and retains the colored state when rapidly cooled from the temperature. The recording display medium described in 1.   8. The method according to claim 1, comprising: a step of forming a liquid crystal layer by applying an organic solvent solution of a cholesteric liquid crystal compound on a substrate; and a step of forming a protective layer on the liquid crystal layer. A method for producing the recording display medium according to claim 1.

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