JP4176599B2 - Display medium, display device using the same, and reversible display - Google Patents

Description

  The present invention relates to a display medium capable of reversibly changing a visual state by the action of an electric field, a display device using the display medium, and a reversible display body.

  Various types of conventional liquid crystal display elements that are the premise of the present invention have been proposed and put to practical use. A typical method is a transmission (S) TN method in which a twisted liquid crystal molecular layer is sandwiched between two polarizing plates. In these methods, since a polarizing plate is used and a color filter and a polarizing plate are used for color display, a strong backlight is required to obtain a brighter display. From the relationship between power consumption and brightness, a reflection type (S) TN method that does not require a backlight or a method that does not use a polarizing plate has been proposed.

As a typical display element using a method that does not use a polarizing plate, there is a polymer dispersed liquid crystal (PDLC) element. The PDLC element uses a polymer matrix material having a refractive index comparable to each other and a positive dielectric anisotropy liquid crystal material. From the light control layer in which the liquid crystal is dispersed in a droplet shape having a diameter of several microns in the polymer matrix. Thus, the display is performed by utilizing the difference in refractive index between the polymer matrix and the liquid crystal. That is, since the liquid crystal molecules when no voltage is applied have a distorted arrangement, a difference in refractive index occurs between the liquid crystal droplet and the matrix, and the light incident on the light control layer is scattered. On the other hand, when a voltage is applied, the liquid crystal molecules are aligned in the voltage direction, the refractive index of the droplet and the matrix are the same, and the light incident on the light control layer is transmitted.
As another typical display element that does not use a polarizing plate, an element using a light control layer made of a liquid crystalline gel has been proposed (Patent Documents 1, 2, 3, and 4). A liquid crystalline gel is a gel-like substance exhibiting liquid crystallinity that has substantially lost the fluidity of a liquid liquid crystalline compound that originally has fluidity.

The display element described in Patent Document 1 uses a compound having at least two groups capable of molecular bonding and alkylene groups in each molecule as a gelling agent, and is simpler than conventional polymer dispersed liquid crystals. An object of the present invention is to provide an element with excellent contrast that can be manufactured by a simple process. A method of forming a light control layer by air-drying a solution composed of a liquid crystal, a gelling agent, and an organic solvent in a fume hood is exemplified, and the object is certainly achieved in terms of simplifying the manufacturing process.
In addition, a gel material including a liquid crystal compound and a gelling agent having an organic group including a divalent skeleton represented by —NH—CH (—R) —CO—, and a display element using the same It is presented in Patent Document 2. Specifically, a TN type element formed by providing a light control layer made of a gel material between two ITO electrodes having a rubbing-treated polyimide alignment film is shown. This TN type cell is superior to the case of using a non-gelled liquid crystal compound in terms of electric field response.

  According to Patent Document 3, a liquid crystal gel showing a nematic phase, a smectic phase or a chiral smectic phase, or a ferroelectric property showing a smectic phase or a chiral smectic phase, using the same gelling agent and liquid crystal compound as described above. Or the display element which uses an antiferroelectric liquid crystal gel as a light control layer is provided. The element comprised from the illustrated ferroelectric liquid crystal gel has high stability excellent in shock resistance. Furthermore, the display element described in Patent Document 4 contains a liquid crystal substance and a gelling agent between a pair of substrates subjected to alignment treatment for the purpose of improving switching characteristics, increasing contrast, and realizing gradation expression. There has been proposed a method of aligning the liquid crystal composition to be parallel or perpendicular to the alignment treatment direction.

However, the method using light scattering by the refractive index difference using a PDLC element does not require a polarizing plate, but the scattering intensity is not so strong, and thus there is a problem that a sufficiently bright and high-contrast display cannot be obtained. The light scattering element described in Patent Document 1 does not reach a sufficient level in terms of contrast, similar to the PDLC method. In addition, the display element described in Patent Document 2 has a defect that a sufficient contrast cannot be obtained due to a small light transmittance when no voltage is applied, and the light scattering element and the TN described in Patent Document 3 are not provided. The mold element has a disadvantage that a contrast with excellent visibility cannot be obtained.
Furthermore, the method described in Patent Document 4 smoothly switches from horizontal alignment to vertical alignment, but has a problem that it does not reach a sufficient level in the same manner as the above-described element in terms of contrast.

JP-A-11-52341 Japanese Patent Laid-Open No. 11-256164 JP 2000-239663 A JP 2000-305087 A

  In view of the above problems, it is an object of the present invention to provide a display medium capable of high-contrast display with excellent visibility, a display device using the display medium, and a reversible display.

In order to solve the above-mentioned problem, the present invention according to claim 1 is a display medium comprising a display cell and a display composition contained in the display cell, wherein the display cell has an electrode on one side surface and the electrode surface. A light-absorbing substrate having a vertically aligned liquid crystal alignment film comprising a compound having a long-chain alkyl group having 8 or more carbon atoms, a transparent electrode on one surface, and a long-chain alkyl group having 8 or more carbon atoms on the electrode surface. And a transparent substrate having a vertical alignment liquid crystal alignment film made of a compound having the above structure, and the display composition comprises a dual frequency drive liquid crystal composition having a helical pitch of 0.3 to 1.2 μm and a gelling agent. The display medium is characterized by the following.
The invention according to claim 2 is the display medium according to claim 1, wherein a protective layer is provided on at least a part of the display medium.
The invention according to claim 3 is the display medium according to claim 1 or 2, wherein a printing layer is provided on at least a part of the display medium and / or at least a part on the protective layer.

The invention according to claim 4 is the display medium according to claim 3, wherein a print protective layer is provided on the print layer.
The invention according to claim 5 is the display medium according to any one of claims 1 to 4, further comprising an information recording section.
The invention according to claim 6 is the display medium according to claim 5, wherein the information recording unit is a recording unit capable of writing and reading information recording by a magnetic action.
The invention according to claim 7 is the display medium according to claim 5 or 6, wherein the information recording unit is an integrated circuit memory or an optical memory.
The invention according to claim 8 is the display medium according to any one of claims 5 to 7, wherein the information recording unit is a transparent recording unit capable of reading out information recording by the action of light. It is.
The invention described in claim 9 is characterized in that the information in the information recording unit is information indicating the front and back of the display medium and / or information indicating the position of the display medium. It is a display medium of description.

A tenth aspect of the invention comprises the display medium according to any one of the first to ninth aspects, and a writing device capable of displaying visible information on the display medium. Is a display device that can be attached and detached so that it can be brought close to at least during writing, and the writing device is equipped with a plurality of signal electrodes and scanning electrodes, and an electric field is applied to the display medium in accordance with an image signal at the intersection. A display device characterized in that it has a switching element capable of displaying an image on a display medium.
According to an eleventh aspect of the present invention, in the display device according to the tenth aspect, the switching element capable of applying an electric field to the display medium in accordance with an image signal is a thin film transistor.
A twelfth aspect of the present invention is a reversible display body in which the display medium according to any one of the first to ninth aspects and a thin film transistor are integrated.
A thirteenth aspect of the present invention is a reversible display body in which the display medium according to any one of the first to ninth aspects occupies a part or all of the display medium.
The invention according to claim 14 is the reversible display body according to claim 13, wherein the reversible display body is a reversible display card, a reversible display sheet, a reversible display display or a reversible display type signboard.
The invention described in claim 15 is the reversible display body according to claim 14, characterized in that the reversible display card, reversible display sheet, reversible display, or reversible display type signboard has flexibility.

  ADVANTAGE OF THE INVENTION According to this invention, the display medium which can display more clearly compared with the conventional one, a display apparatus using the same, and a reversible display body can be provided.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a diagram showing an example of a form of a display medium comprising a display cell of the present invention and a display composition contained in the display cell. The display cell includes a light-absorbing substrate 1 in which a vertical alignment liquid crystal alignment film 3 made of a compound having an electrode 2 and a long-chain alkyl group having 8 or more carbon atoms is sequentially stacked on one surface, and a transparent electrode 5 and carbon on one surface. A display composition comprising a transparent substrate 4 on which vertical alignment liquid crystal alignment films 6 made of a compound having a long-chain alkyl group of several 8 or more are sequentially laminated so that the alignment film surfaces face each other. 8 is formed from a dual-frequency drive liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm and a gelling agent.

  The vertically aligned liquid crystal alignment film 3 made of a compound having a long-chain alkyl group having 8 or more carbon atoms provided on the surface of the electrode 1 and the transparent electrode 4 of each of the substrates 1 and 4 has a long axis direction of liquid crystal molecules with respect to the substrate. An alignment film that is vertically aligned. In an alignment film made of a compound having a long-chain alkyl group having 7 or less carbon atoms, effective vertical alignment cannot be obtained. As compounds having a long-chain alkyl group having 8 or more carbon atoms, long-chain alkyltrimethoxysilane, long-chain alkyldimethoxysilane, long-chain alkylmethoxysilane, long-chain alkyltriethoxysilane, long-chain alkyldiethoxysilane, long-chain alkyl Examples include, but are not limited to, ethoxysilane, long-chain alkyltrichlorosilane, long-chain alkyldichlorosilane, long-chain alkylchlorosilane, long-chain alkylphosphonic acid, long-chain alkylcanlubonic acid, long-chain alkylcanlubonic acid chloride, and the like. . These compounds having a long-chain alkyl group having 8 or more carbon atoms are physically or chemically adsorbed on the surfaces of the electrode 2 and the transparent electrode 4 to form the vertical alignment liquid crystal alignment film 3. From the viewpoint of thermal stability, chemical adsorption is preferred. When a compound having a long-chain alkyl is chemically adsorbed on the electrode surface, it can be reacted with a compound having a long-chain alkyl having 8 or more carbon atoms using a hydroxyl group present on the electrode surface.

The dual frequency drive liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm constituting the display composition 8 is lower than fc with a certain frequency (crossover frequency: fc) of the applied voltage as a boundary point. It consists of a nematic liquid crystal compound and a chiral agent that show positive dielectric anisotropy at an applied voltage of frequency fL, and negative dielectric anisotropy at an applied voltage of frequency fH higher than fc, and the size of the helical pitch is It can be adjusted according to the type and concentration of the chiral agent. In general, the helical pitch increases as the chiral agent concentration decreases.
The dual-frequency driving liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm forms a focal conic alignment in a light transmission state by applying and blocking a voltage having a positive dielectric constant frequency fL. A planar orientation in a light selective reflection state is formed by applying / cutting off a voltage having a frequency fH indicating a negative dielectric constant.

In particular, the focal conic alignment and the planar alignment of the dual frequency drive liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm are combined with the vertical alignment liquid crystal alignment films 3 and 6 having a pretilt angle of 80 ° or more. As a result, the memory property of each orientation state is stably expressed for a long time. When the pretilt angle is less than 80 °, the memory property in the planar alignment state is not different from that in the case where the pretilt angle is 80 ° or more, but the memory property in the focal conic alignment state is greatly deteriorated.
Further, in the planar orientation having a spiral pitch larger than 1.2 μm, light selective reflection is difficult to occur, and therefore, a color tone other than the color tone depending on the electrophoretic particles 6 is not displayed. On the other hand, in order to reduce the spiral pitch of the display composition 8, it is necessary to add more chiral agent to the dual frequency drive liquid crystal composition 7, but the display is proportional to the increase in the concentration of the chiral agent. Since the viscosity of the composition 8 is increased, problems such as a decrease in response speed and an increase in driving voltage occur. Therefore, the lower limit of the helical pitch is set to 0.3.
Further, the dual-frequency driving liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm is more stably maintained in the planar alignment and the focal conic alignment by forming a gel composition with a gelling agent.
The liquid crystal gel composition is obtained by a method in which a hot solution composed of a liquid crystal compound and a gelling agent is cooled to room temperature and left for a long time, or a method in which ultrasonic waves are applied to the hot solution. The hot solution of liquid crystal / gelling agent is a method of adding a gelling agent to a liquid crystal compound and stirring, or a method of dissolving the gelling agent in a solvent capable of dissolving the gelling agent at room temperature or heating and adding this solution to the heated liquid crystal compound Is obtained.

  As a gelling agent, 4-[{(1-naphthylamino) carbonyl} amino] benzoic acid 2-octyldodecyl ester, N, N ′, N ″ -tristearyl trimesamide, 4-hexadecanoyl-2-nitro N-benzyloxycarbonyl-L-alanine ester of phenyl (2-benzyloxycarbonylamino-propionic acid 4-hexadecanoyl-2-nitro-phenyl ester), N-benzyloxycarbonyl-L-valyl-L-valine- n-octadecylamide, N-lauroyl-L-glutamic acid-α, γ-dibutyramide, 1,3: 2,4-dibenzylidene-D-sorbitol (1- (2,6-diphenyl-tetrahydro- [1,3 Dioxino [5,4-d] [1,3] dioxin-4-yl) -ethane-1,2-diol), 4,4′-bis (n-octylureido) diphenylmethane, Nε-lauroyl-Nα-stearylaminocarbonyl-L-lysine ethyl ester, Nε-lauroyl-Nα-butylaminocarbonyl-L-lysine ethyl ester, Nε-lauroyl- Nα-cyclohexaneaminocarbonyl-L-lysine ethyl ester, Nε-lauroyl-Nα-benzylaminocarbonyl-L-lysine ethyl ester, trans- (1R, 2R) -bis (octadecylureido) cyclohexane, trans- (1R, 2R) -Bis (dodecanoylamino) cyclohexane, Nn-octyl-D-gluconamide-6-benzoate, cyclo [(R) -phenylalanyl- (R) -leucyl], cyclo [glycyl- (R) -γ -Ethylglutamyl], cyclo [ R) -valyl- (R) -leucyl], cyclo [(R) -valyl- (R) -γ-ethylglutamyl], cyclo [(R) -valyl- (R) -3,7-dimethyloctylglutamyl] , Cyclo [(R) -valyl- (R) -γ-2-ethylhexylglutamyl], cyclo [(R) -leucyl- (R) -γ-ethylglutamyl], cyclo [(R) -β-3,7 -Dimethyloctyl asparaginyl- (R) -phenylalanyl], cyclo [(R) -β-butylasparaginyl- (R) -phenylalanyl], t-butoxycarbonyl-L-tyrosyl (3-methoxy Carbonyl-terminal fretket type dendron) -L-alanine, 5-hexadecyl-2,4,6-triaminopyrimidine, 5,5-didodecylbarbituric acid, or cyclotetrapeptides It is.

According to the display medium comprising such a display cell and the display composition 8, as shown in FIG. 1A, the electrode 2 on the light-absorbing substrate 1 and the transparent electrode 5 on the transparent substrate 4 are interposed. When the frequency fH is applied, the two-frequency driving liquid crystal composition 7 starts planar alignment, and a colored color tone by selective reflection light is displayed. This state is maintained even after the voltage is removed, and stable display is possible. Alternatively, for the homeotropic alignment of the two-frequency driving liquid crystal composition 7, it is also possible to perform planar alignment by applying a sufficiently large voltage at a frequency fL and then removing the voltage immediately.
As shown in FIG. 1B, when the frequency fL is applied, the two-frequency driving liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm exhibits a positive dielectric anisotropy and thus has a focal conic orientation. Thus, a transparent state that transmits visible light is obtained. Therefore, the color tone of the light-absorbing substrate 1 is displayed on the transparent substrate 4 side.
When the application of voltage is stopped in this state, the dual frequency drive liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm is affected by the interface between the gelling agent and the vertical alignment liquid crystal alignment films 3 and 6. Accordingly, the focal conic orientation is maintained, the transparent state is maintained, and the color tone of the light-absorbing substrate 1 when a voltage is applied is stably maintained for a long time.

Next, a preferred embodiment of the display medium of the present invention will be described with reference to FIG.
The light absorbing substrate 1 is a colored substrate made of a glass plate or a plastic film having a light absorbing layer. The transparent substrate 4 is a transparent substrate made of a glass plate or a plastic film. The thickness of the substrates 1 and 4 is about 10 μm to 1 mm, preferably 25 to 200 μm. The electrode 2 may be transparent or colored and is made of a conductive thin film such as metal, ITO, SnO2, or ZnO: Al, and is formed by a sputtering method, a vacuum deposition method, a CVD method, a coating method, or the like. The electrode 5 is a transparent electrode made of a transparent material such as ITO, SnO 2, or ZnO: Al. The electrode 2 and the electrode 5 are electrodes that are patterned in a matrix or are not patterned, and at least one of them is an unpatterned electrode. An unpatterned electrode can be used as a common electrode. The vertical alignment liquid crystal alignment films 3 and 6 are provided by a physical adsorption method or a chemical adsorption method, and do not require a rubbing treatment.

The protective layer 11 is formed by applying a protective layer material and, optionally, a protective layer material composition to which a medium, a curing agent, a catalyst and / or a promoter for dissolving, dispersing, suspending or emulsifying the material is added on the transparent substrate 4. It is formed by a coating method such as bar coating, roll coating, blade coating, dip coating, spray coating, spin coating or gravure coating, or a vapor phase method such as sputtering or chemical vapor deposition.
The thickness of the protective layer 11 is desirably as thin as possible within the range having the function of protecting the substrate 4, and is about 0.1 to 100 μm, more preferably 0.3 to 30 μm.
Protective layer materials include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, ethylene-vinyl alcohol copolymer, polyacetal. , Acrylic resin, methylcellulose, ethylcellulose, phenolic resin, fluororesin, silicone resin, diene resin, polystyrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyphenylene ether, polyphenylene sulfide, Polyethersulfone, polyetherketone, polyarylate, aramid, polyimide, poly-p- Enylene, poly-p-xylene, poly-p-phenylene vinylene, polyhydantoin, polyparabanic acid, polybenzimidazole, polybenzothiazole, polybenzoxadiazole, polyquinoxaline, thermosetting resin or active energy ray curable resin, or A mixture thereof may be mentioned.

The printing layer 12 may be formed by known offset printing, gravure printing, or screen printing on at least a part on the protective layer 11 (at least a part excluding the display part on the protective layer 11) according to the purpose of use of the display medium. it can.
The print protective layer 13 is made of the same material as that of the protective layer 11, and can be provided on the print layer 12 and the protective layer 11 by a known method in the same manner as the protective layer 11 and the print layer 12.

Next, another preferred embodiment of the display medium of the present invention will be described with reference to FIG. The substrate 1, the transparent substrate 4, the electrode 2, the transparent electrode 5, the vertical alignment liquid crystal alignment film 3, and the display composition 8 are the same as those in FIG.
As shown in FIG. 3A, a magnetic recording unit 23 and an integrated circuit memory 24 are provided on at least a part of the substrate 1 on the non-display surface 26, and the magnetic recording unit 23, the integrated circuit memory 24, and the substrate 1 are provided. The second protective layer 25 is provided. The second protective layer 25 is formed of the same material as that of the protective layer 11 and the print protective layer 13.
As shown in FIG. 3B, the transparent recording unit 22 can be provided in a lattice shape. The intersection (xn, ym) between the formed row xn and the column ym (n, m = 1, 2,...) Can be specified as read / write information and used as digital information. That is, in the case of such a display medium, the display of the display composition 8 can be visually observed through the transparent substrate 4, the transparent common electrode 5, and the transparent recording unit 22, and at the same time, it corresponds to the display or is an independent digital Information can be written and read. The protective layer 21 protects the transparent recording portion 22.

The magnetic recording unit 23, the integrated circuit memory 24, or the optical memory information recording unit capable of writing and reading information recording by the magnetic action used for the display medium can be manufactured using conventional techniques.
Furthermore, the display medium includes a display device and a writing device capable of displaying information visible on the display medium, and the display medium and the writing device are attachable and detachable so as to be close to each other at the time of writing. Can be configured. The writing device includes a plurality of signal electrodes and scanning electrodes, and has a switching element that can apply an electric field to the display medium in accordance with an image signal at an intersection thereof, whereby an image is displayed on the display medium. It can be configured to display.
In such a configuration, since the two-dimensionally arranged electric field applying means has a switching element, the electric charge given to a part at the time of selection is discharged by the time constant of the material constituting the display medium when not selected. If it is longer than the particle movement time (response time), the selection time can be made shorter than the response time, and as a result, the writing speed is increased.

Further, the switching element that can apply an electric field to the display medium in accordance with the image signal may be a thin film transistor.
As the switching element, a thin film transistor that can easily manufacture a thin film device having a large area is preferable. Since the thin film transistor is a three-terminal element, the switching performance is high, and a clear display can be obtained even when halftone is involved. In order to increase the writing speed, a storage capacitor can be provided in parallel with the display medium in an equivalent circuit.
The display medium can be used in various forms as a reversible display body in which a thin film transistor and a display medium are integrated. Further, the display medium can be used in various forms as a reversible display body in which the display medium occupies a part or all of the display medium.

For example, the display medium of the present invention constitutes a part or all of a small card such as a business card or a credit card, so that a card capable of rewriting information is produced. Can be used as a card or membership card. By increasing the size of such a small card with excellent portability, it is a reversible display sheet as a substitute display for displays and recording paper (output paper for copiers, printers, etc.) used in general offices. Can also be produced. Since such a reversible display sheet can be used repeatedly, it is an excellent display medium from the viewpoint of resource saving and energy saving. Further, by incorporating the display medium of the present invention into various articles such as home appliances, information can be provided instead of a conventional liquid crystal monitor. In this case, an excellent display with a wide viewing angle and high contrast can be realized. Furthermore, the display medium of the present invention can also be used for various advertisements, billboards, and the like. In this case as well, the entire surface can be constituted by a display medium, but it is also possible to realize effective display by incorporating it in a part of a poster or the like.
In addition, since the above-described display medium can give flexibility to the medium by a configuration including a substrate, there are restrictions on the shape in various uses including the card, sheet, display, signboard, and advertisement. It can be used for a very wide range of applications.

  EXAMPLES Hereinafter, although this invention is demonstrated in more detail based on an Example, these are only one aspect | modes of this invention, and this invention is not limited by these Examples.

(Example 1)
[Production of display medium]
A 1.1 mm thick glass substrate with ITO (SuperITO-A, ULVAC, Inc.) is used in 1: 1: 5 hydrogen peroxide solution (about 30%), aqueous ammonia solution (about 30%) and ions. After immersing in a solution composed of exchange water and sonicating for about 5 minutes, the solution was immersed in the solution at 60 ° C. for 30 minutes to create a hydroxyl group on the ITO surface. To a dry toluene solution in which 5% by volume of octadecyltrimethoxysilane was dissolved, 0.5% by volume of n-butylamine was added. The surface-treated glass substrate with ITO was immersed in the obtained solution and subjected to ultrasonic treatment at 10 ° C. or lower for about 60 minutes to form a vertically aligned liquid crystal alignment film on the ITO surface.
Two glass substrates with ITO on which a vertical alignment liquid crystal alignment film is formed are prepared, arranged with the alignment film surfaces facing each other, and an internal space having a distance between electrode surfaces of about 18 μm is formed by a resin particle spacer to display I got a cell.
On the other hand, 8.10.0 g of chiral agent S-1011 (100.0 g of dual-frequency driving liquid crystal composition MX001544 (manufactured by Merck Japan, Δε (10 kHz) = 1.1, Δε (100 kHz) = − 3.9)) Merck Japan Ltd.) was dissolved to prepare a liquid crystal composition. As a result of measuring the helical pitch with a wedge-shaped cell, it was about 1.1 μm.
To this liquid crystal composition, 1.0 g of a gelling agent having the structure of the following [Chemical Formula 1] was added, stirred while heating until dissolved, and then allowed to stand for about 6 hours to obtain a liquid crystal gel composition having no fluidity. It was. This gel composition was heated again, and the obtained transparent solution was injected into the internal space of the display cell. After leaving for about 12 hours, the cell was sealed with an adhesive to produce a display medium.

(Example 2)
[Production of display medium]
In 100 mg of nematic liquid crystal composition MX001544, 10.3 mg of chiral agent S-1011 was dissolved to prepare a liquid crystal composition. As a result of measuring the helical pitch with a wedge-shaped cell, it was about 0.6 μm.
Using this liquid crystal composition, a liquid crystal gel composition was prepared in the same manner as in Example 1, and then a display medium was produced.

(Comparative Example 1)
A display cell was produced in the same manner as in Example 1 except that hexylmethoxysilane was used instead of octadecyltrimethoxysilane in Example 1.
The same liquid crystal gel composition as in Example 2 was injected into this display cell, and a display medium was produced in the same manner as in Example 2.

(Comparative Example 2)
In 100 g of nematic liquid crystal composition MX001544, 6.2 g of chiral agent S-1011 was dissolved to prepare a liquid crystal composition. As a result of measuring the helical pitch with a wedge-shaped cell, it was about 1.8 μm.
Using this liquid crystal composition, a liquid crystal gel composition was prepared in the same manner as in Example 2, and then a display medium was produced.

(Comparative Example 3)
A liquid crystal composition prepared in the same manner as in Example 2 was injected into the same display cell as in Comparative Example 1 to produce a display medium.

(Example 3)
A voltage of 50 V (100 Hz) was applied to the display surface through the electrode of the medium to the display media produced in Examples 1-2 and Comparative Examples 1-3, and the dual-frequency drive liquid crystal composition was subjected to focal conic alignment. Thereafter, the electric field was removed, and a color tone depending on the light-absorbing substrate was displayed.
In color tone display depending on the light-absorbing substrate, one hour after the display operation, the reflected light of the display medium is irradiated in the wavelength region of 380 to 800 nm by 45-degree irradiation-vertical light reception using Photo MCPD-1000 manufactured by Otsuka Electronics Co., Ltd. Measurement was performed, and the reflectance of the light-absorbing substrate display was calculated with the reflectance of the standard white plate as 100%. The results are shown in Table 1.

Example 4
An AC voltage of 50 V (50 kHz) was applied to the display surface side through the electrode of the medium to planarize the two-frequency driving liquid crystal composition, and then the electric field was removed to display the color tone by selectively reflected light.
In the display depending on the selective reflection light, the reflected light of the display medium is measured in the wavelength region of 380 to 800 nm by using the MCPD-1000 with 45-degree irradiation-vertical light reception one hour after the display operation. The reflectance at the peak wavelength was determined. Table 1 shows the peak wavelength and the reflectance of the selectively reflected light display. Further, the ratio (contrast ratio) of the reflectance of the selectively reflected light display to the reflectance of the electrophoretic particle display was obtained.

As can be seen from Table 1, Examples 1 and 2 showed a contrast ratio of 10 or more. However, in Comparative Examples 1 and 3, the liquid crystal composition with focal conic alignment in the light-absorbing plate display was aged for about 1 hour. Since the planar alignment was gradually performed, color mixture due to selective reflected light occurred, and an effective low reflectance could not be obtained. Further, Comparative Example 2 did not exhibit selective reflection in the planar alignment, and light scattering by the liquid crystal gel occurred in the focal conic alignment state, and thus showed a low contrast ratio opposite to that of the example and other comparative examples.
From these results, it became clear that a display medium having excellent visibility and high memory property can be obtained by using the display medium of the present invention.

It is sectional drawing which shows an example of the form of the display medium which concerns on this invention, (a) is a figure which shows the state in which the dual frequency drive liquid crystal composition which has a helical pitch is planar-aligned, and the display by selective reflection light is possible, b) is a diagram showing a state in which a dual-frequency driving liquid crystal composition having a helical pitch is in a focal conic orientation and can display depending on a light-absorbing substrate. It is sectional drawing which shows preferable embodiment of the display medium based on this invention. It is a figure which shows other preferable embodiment of the display medium based on this invention, (a) is sectional drawing, (b) is a top view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light absorption board | substrate 2 Electrode 3 Vertical alignment liquid crystal aligning film 4 Transparent substrate 5 Transparent electrode 6 Vertical alignment liquid crystal aligning film 7 Dual frequency drive liquid crystal composition 8 which has a helical pitch Display composition 11 Protective layer 12 Print layer 13 Printing Protective layer 14 Display surface 21 Protective layer 22 Transparent recording portion 23 Magnetic recording portion 24 Integrated circuit memory 25 Second protective layer 26 Non-display surface X1 to X7 Row numbers Y1 to Y7 of lattice-like transparent recording portions Grid-like transparency Column number

Claims (15)

In a display medium comprising a display cell and a display composition contained in the display cell,
The display cell has a light-absorbing substrate having a vertical alignment liquid crystal alignment film composed of an electrode on one surface and a compound having a long-chain alkyl group having 8 or more carbon atoms on the electrode surface, and a transparent electrode on one surface. The display composition comprises a transparent substrate having a vertically aligned liquid crystal alignment film composed of a compound having a long-chain alkyl group having 8 or more carbon atoms on the electrode surface, and the display composition has a helical pitch of 0.3 to 1.2 μm. A display medium comprising a liquid crystal composition having a dual frequency drive and a gelling agent. The display medium according to claim 1, wherein a protective layer is provided on at least a part of the display medium. The display medium according to claim 1, wherein a print layer is provided on at least a part of the display medium and / or on at least a part of the protective layer. The display medium according to claim 3, wherein a print protective layer is provided on the print layer. 5. The display medium according to claim 1, further comprising an information recording unit. The display medium according to claim 5, wherein the information recording unit is a recording unit capable of writing and reading information recording by a magnetic action. The display medium according to claim 5, wherein the information recording unit is an integrated circuit memory or an optical memory. The display medium according to claim 5, wherein the information recording unit is a transparent recording unit capable of reading information recording by an action of light. 9. The display medium according to claim 5, wherein the information in the information recording unit is information indicating the front and back of the display medium and / or information indicating the position of the display medium. A display medium according to any one of claims 1 to 9 and a writing device capable of displaying visible information on the display medium, wherein the display medium and the writing device are brought close to each other at the time of writing. The display device is detachable, and the writing device is equipped with a plurality of signal electrodes and scanning electrodes, and has a switching element that can apply an electric field to the display medium in accordance with an image signal at an intersection thereof. A display device configured to display an image on a display medium thereby. The display device according to claim 10, wherein the switching element capable of applying an electric field to the display medium in accordance with an image signal is a thin film transistor. 10. A reversible display, wherein the display medium according to claim 1 and a thin film transistor are integrated. A reversible display, wherein the display medium according to any one of claims 1 to 9 occupies a part or all of the display medium. The reversible display body according to claim 13, wherein the reversible display body is a reversible display card, a reversible display sheet, a reversible display display, or a reversible display type signboard. The reversible display card according to claim 14, wherein the reversible display card, the reversible display sheet, the reversible display, or the reversible display type signboard has flexibility.

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