JP2006251592A - Display medium, and display device and reversible display body using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display medium for an electrophoretic display producing a display with high visibility, and a display device and a reversible display body using the same. <P>SOLUTION: The display medium is composed of a display cell and a display composition contained in the display cell, and the display medium is characterized in that the display cell is constituted of a substrate 1 which has an electrode 2 on the one side surface thereof and a vertical alignment liquid crystal alignment layer 3 composed of an alkylphosphonic acid compound formed on the electrode surface, and a transparent substrate 4 which has a transparent electrode 5 on the one side surface thereof and the vertical alignment liquid crystal alignment layer 3 composed of the alkylphosphonic acid compound formed on the transparent electrode surface, and the display composition contains a dual frequency driven liquid crystal composition with 0.3-1.2 μm helical pitch and electrophoretic particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In an electrophoretic display device, at least one transparent substrate is placed opposite to each other through a spacer to form a sealed space, and dispersed particles (pigment component particles) are placed in the sealed space. A particle is a display panel filled with a display liquid dispersed in a dispersion medium colored in a different color tone, and an electric field is applied to the display panel to obtain a display. Becomes the display surface.

  The display liquid for electrophoretic display filled in the sealed space is a dispersion medium such as xylene or isoparaffin, fine particles (dispersion particles) such as titanium dioxide, a dye for imparting a color contrast with the dispersion particles, a surfactant, etc. And other additives such as a dispersing agent and a charge imparting agent. By applying an electric field to the display liquid, the dispersed particles in the display liquid move to the transparent plate side, and the color of the dispersed particles appears on the surface. Also, by applying an electric field in the opposite direction, the dispersed particles move to the back side, and the color of the dispersion medium colored with the dye appears on the surface.

  Such an electrophoretic display device is a display device that obtains a desired display by controlling the direction of an electric field, the display liquid is a relatively low-cost material that is relatively easily available, and the viewing angle is the same as that of a normal printed matter. It has attracted attention as an inexpensive display device because it has advantages such as wideness, low power consumption, and memory property.

  Further, a dispersion system (display liquid for electrophoretic display) composed of such dispersed particles and a dispersion medium colored in a different color tone from the dispersed particles is enclosed in microcapsules, and these microcapsules are arranged between the electrodes. An electrophoretic display device having a configuration to be worn has been proposed (Patent Document 1), and simple means have been proposed as a method for configuring the electrophoretic display device.

However, the display liquids of these electrophoretic display devices are generally dispersed in high-refractive index inorganic pigment particles such as titanium dioxide in a hydrophobic dispersion medium colored by dissolving a dye or the like. It is difficult to maintain the stability of the display, and there is a drawback in that the display quality deteriorates due to a decrease in contrast due to aggregation or the like when repeatedly displaying. In addition, since these systems generally use dye solutions, color adsorption due to dye adsorption on the pigment surface and penetration of the dye solution into the gap between the pigment and the pigment is likely to occur, and the contrast is also greatly reduced. It also has a drawback.
Regarding these problems, it is considered that the stability of the above dispersion state is involved together with the constitution of the dispersion system using the dye solution, and it is required to overcome both.

  On the other hand, means for improving dispersion stability has been proposed. For example, in a system using a titanate coupling agent as a surface treatment agent for electrophoretic particles in a colored dispersion medium colored with a dye. A method of adding a sorbitan fatty acid ester surfactant has been proposed (Patent Document 2). However, the surfactant used here has an insufficient pigment dispersion stabilizing effect in a non-aqueous organic solvent, and a sufficient effect is not obtained under electrophoresis conditions in which a voltage is applied.

  Patent Document 3 proposes a method of incorporating a quaternary ammonium salt compound as a charge control agent into charged particles. Specifically, one of two types of electrophoretic particles having different charges is proposed. Is treated with the above charge control agent, and a surfactant is further added. However, in this case as well, as in the case of Patent Document 2, sufficient dispersion stability is not obtained, and this is effective. Is insufficient.

  On the other hand, apart from improving dispersion stability, various proposals have been made to improve contrast. For example, a dye that is non-adsorptive to the pigment surface is used as the dye used for coloring the dispersion medium (Non-patent Document 1), the dye concentration in the dispersion medium is decreased (Non-Patent Document 2), and the dye Improvements by optimization of concentration, pigment concentration, and surfactant (Non-Patent Document 3) have also been proposed. However, these methods are not only ineffective, but also cause problems such as a decrease in display density and a decrease in response speed due to the dye solution, and no practical solution has been reached.

  Further, Patent Document 1 discloses a method of encapsulating a display liquid for electrophoretic display as described above and using it as display particles. An advantage of this method is that non-uniform display due to uneven distribution of migrating particles can be prevented. However, this method is also not sufficient in terms of contrast, as in the case of Non-Patent Documents 1 to 3, since the display liquid contained therein uses a colored dye solution and a dispersion of pigment particles.

  Thus, a system that does not use a dye solution has been proposed as a means for solving the above-described drawbacks of a system that uses a colored dispersion medium. For example, a liquid in which at least two kinds of electrophoretic fine particles having different color tones and electrophoretic properties are dispersed in a highly insulating and low-viscosity colorless dispersion medium is dispersed through a spacer between two opposing electrodes, at least one of which is transparent. An electrophoretic display element enclosed in a cell formed in this manner has been proposed (Patent Document 4). However, in these systems, the charged charges of the electrophoretic fine particles having different color tones are opposite (positive and negative combination), so a stable dispersion state is not maintained, and aggregation occurs due to an electric attractive force between the particles. Therefore, it is difficult to realize a display having a good contrast by causing color mixing.

  Further, a liquid in which at least two kinds of electrophoretic fine particles having the same electrophoretic property, different color tone and electrophoretic speed are dispersed in a highly insulating and low-viscosity colorless dispersion medium, is opposed to two transparent plates at least one of which is transparent. An electrophoretic display element encapsulated in a cell formed through a spacer between electrodes has been proposed (Patent Document 5). However, also in this case, it is difficult to maintain a stable dispersion state when collision between particles occurs, and a sufficient function has not been achieved. Furthermore, in this case, since the electrophoretic fine particles moving in the same direction use different moving speed differences, it is impossible to display different color tones simultaneously on one surface, and the same direction Because of the movement of particles, the display is slow and lacks practicality.

  An example in which the same dispersion system as the electrophoretic display display liquid proposed in Patent Document 4 is enclosed in a microcapsule is disclosed in Patent Document 6, but in this case, the stability of the dispersion system is also disclosed. This is not a practical means because it is not maintained, and color mixing due to aggregation due to electrical attraction between the electrophoretic fine particles occurs in the microcapsule and causes display color mixing.

  On the other hand, agglomeration between particles, which is a problem in a system in which a liquid in which two kinds of electrophoretic fine particles having different color tones and electrophoretic properties (charged charges) are dispersed as a display liquid for electrophoretic display, is prevented. For this purpose, it has been proposed to use a steric repulsion effect by adding a charge adjusting agent, surface treatment of particles, or the like (Patent Document 7). However, with this means, it is difficult to maintain sufficient dispersion stability and completely prevent aggregation between the two types of electrophoretic fine particles, and a good contrast has not been realized.

  Further, there has been proposed an image display ink composition composed of white particles for concealment composed of a resin and a white pigment, colored particles for display, and a solvent (Patent Document 8). The white particles proposed here are white The purpose of adjusting the specific gravity difference with a solvent in a display liquid for electrophoresis using a dispersion medium that is a dispersion medium colored with a dye. White particles used in Even in this case, since the stability of the dispersed state is not maintained, the function of reducing aggregation between two kinds of particles in combination with pigments having different color tones (color pigments for display made of magnetic powder alone or a mixture). Therefore, as in the above-described technique, color mixing due to aggregation is caused, and contrast is lowered.

  On the other hand, as an example relating to the solvent species, it has been proposed to use linear alkylbenzene as a dispersion medium in a system using a colored dispersion medium colored with a dye (Patent Document 9). However, since these solvents do not have a function of improving the special dispersion stability, it is difficult to improve the dispersion stability and further improve the contrast by developing this technology. Examples of using a mixed solvent of halogenated tetrachloroethylene and alkylbenzene or a mixed solvent of tetrachloroethylene, 5-ethylidenenorbornene and an aromatic solvent as a dispersion medium have been proposed (Patent Documents 10 and 11). As with chain alkyl benzene, it does not achieve a sufficient effect.

  On the other hand, an electrophoretic display device in which an electrophoretic particle composed of dielectric particles and a dispersion medium composed of a dichroic dye and a nematic liquid crystal are sealed in a gap between a transparent substrate and a counter substrate, and the above electrophoretic particles And an electrophoretic display device comprising microcapsules having a particle diameter of 1 to 100 μm enclosing a dispersion medium (Patent Document 12). In the former electrophoretic display device, a vertically aligned alignment film is provided on a transparent substrate serving as a display surface, and a vertical alignment or a horizontal alignment alignment film is provided on a counter substrate serving as a back surface. Both absorption axes of chromatic dyes are vertically aligned.

  When displaying the color tone of electrophoretic display particles with this apparatus, that is, when electrophoretic particles are present on the display surface, absorption of dichroic dye existing in the gaps between electrophoretic particles is eliminated, and electrophoretic properties are eliminated. It is possible to effectively display the color tone of the particles. However, when displaying the color tone of the dichroic dye, i.e., when the electrophoretic particles are present on the back side, the absorption axis of the dichroic dye is closer to the display surface and becomes more vertically oriented, and the incident light is dichroic. It is not absorbed by the pigment and the desired color tone is not displayed. Therefore, a display with high contrast cannot be obtained.

  Also, when displaying the color tone of electrophoretic display particles with the latter device, the dichroic dye in the microcapsule does not interact with the alignment film as in the former device. Color mixing with the color tone of the active particles occurs and the contrast is lowered.

Japanese Patent Laid-Open No. 1-86116 (Patent No. 2551783) JP-A-2-284128 Japanese Patent Laid-Open No. 11-119704 JP 62-269124 A JP-A 63-50886 International Publication No. 98/03896 Pamphlet Japanese National Patent Publication No. 8-510790 JP 10-149117 A Japanese Patent Laid-Open No. 1-300233 (Japanese Patent No. 2612474) Japanese National Patent Publication No. 9-500458 Japanese National Patent Publication No. 9-507881 JP 2000-66247 A Phlips Lab: Conference Record of 1980 Biennial Disp. Res. Conf. XeroxPaloAlto: Proc.SID, Vol.18,3 / 4,1977 Matsushita: Proc. SID, Vol. 18, No 3/4, 1977

  In view of the above problems, it is an object of the present invention to provide a display medium capable of clearer display, a display device using the display medium, and a reversible display.

As a result of intensive studies, the present inventor has found that in a display medium comprising a display cell and a display composition contained in the display cell, the display cell has an electrode on one side surface and an alkylphosphone formed on the electrode surface. A substrate having a vertical alignment liquid crystal alignment film made of an acid compound, and a transparent substrate having a transparent electrode on one surface and a vertical alignment liquid crystal alignment film made of an alkylphosphonic acid compound formed on the transparent electrode surface. And the display composition contains a dual-frequency driving liquid crystal composition having a helical pitch of 0.3 to 1.2 μm and electrophoretic particles, so that the above problem can be solved. The present invention has been found.
That is, this invention is the display medium of the (1)-(16) described below, a display apparatus, and a reversible display body.

(1) In a display medium comprising a display cell and a display composition contained in the display cell, the display cell is composed of an electrode on one side surface and a vertical alignment comprising an alkylphosphonic acid compound formed on the electrode surface. And a transparent substrate having a transparent electrode on one side surface and a vertical alignment liquid crystal alignment film made of an alkylphosphonic acid compound formed on the transparent electrode surface. Contains a dual-frequency driving liquid crystal composition having a helical pitch of 0.3 to 1.2 μm and electrophoretic particles.
(2) The display medium according to the above (1), wherein the alkylphosphonic acid compound is α-hydroxyalkylphosphonic acid.
(3) The display medium according to (1) or (2) above, wherein a protective layer is provided on at least a part of the display medium.
(4) The display medium according to any one of (1) to (3) above, 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.
(5) The display medium according to (4) above, wherein a print protective layer is provided on the print layer.

(6) The display medium according to (1) to (5) above, wherein an information recording unit is provided.
(7) The display medium according to (6), wherein the information recording unit is a recording unit capable of writing and reading information recording by a magnetic action.
(8) The display medium according to (6) or (7), wherein the information recording unit is an integrated circuit memory or an optical memory.
(9) The display medium according to any one of (6) to (8), wherein the information recording unit is a transparent recording unit capable of reading out information recording by the action of light.

(10) The display medium according to (6) to (9) above, 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.
(11) The display medium according to the above (1) to (10) and a writing device capable of displaying visible information on the display medium, so that 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.
(12) The display device according to (11), 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.

(13) A reversible display, wherein the display medium of (1) to (10) and a thin film transistor are integrated.
(14) A reversible display body characterized in that the display medium of (1) to (10) occupies a part or all of the display medium.
(15) The reversible display body according to (14), wherein the reversible display body is a reversible display card, a reversible display sheet, a reversible display display, or a reversible display type signboard.
(16) The reversible display according to (15), wherein the reversible display card, the reversible display sheet, the reversible display, or the reversible display type signboard has flexibility.

  According to the present invention, it is possible to provide a display medium capable of displaying clearer than conventional ones, a display device using the display medium, and a reversible display.

The present invention will be described in detail below.
FIG. 1 shows 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 comprises an electrode 2 and an alkylphosphonic acid compound on one surface. The substrate 1 on which the vertical alignment liquid crystal alignment film 3 is sequentially laminated, and the transparent substrate 4 on which one side surface is laminated with the vertical alignment liquid crystal alignment film 3 made of the alkylphosphonic acid compound in order, and the alignment film surfaces thereof. The display composition 8 is formed of a two-frequency drive liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm and electrophoretic particles 6. .

  A vertical alignment liquid crystal alignment film 3 made of an alkylphosphonic acid compound provided on one side of each of electrodes 2 and transparent electrodes 4 of substrates 1 and 4 is an alignment film that aligns the major axis direction of liquid crystal molecules perpendicularly to the substrate. . A preferred alkylphosphonic acid compound is a linear alkylphosphonic acid compound having 8 or more carbon atoms that is effective for vertical alignment of liquid crystals. A linear alkylphosphonic acid compound having 7 or less carbon atoms or a branched alkylphosphonic acid compound having 8 or more carbon atoms cannot provide effective vertical alignment of liquid crystals.

  Any alkylphosphonic acid compound can be used without particular limitation as long as it has vertical alignment. It is more preferable to use α-hydroxyalkylphosphonic acid as the alkylphosphonic acid compound because it is superior to alkylphosphonic acid in that a stable alignment film is formed by hydrogen bonding with a hydroxy group.

Preferred alkylphosphonic acid compounds include octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, dodecylphosphonic acid, tridecylphosphonic acid, tetradecylphosphonic acid, pentadecylphosphonic acid, hexadecylphosphonic acid, heptadecylphosphonic acid, octadecyl Examples include phosphonic acid, nonadecylphosphonic acid, icosylphosphonic acid, heicosylphosphonic acid, and docosylphosphonic acid.
Preferred α-hydroxyalkylphosphonic acid compounds include 1-hydroxyoctylphosphonic acid, 1-hydroxynonylphosphonic acid, 1-hydroxydecylphosphonic acid, 1-hydroxydodecylphosphonic acid, 1-hydroxytridecylphosphonic acid, 1 -Hydroxytetradecylphosphonic acid, 1-hydroxypentadecylphosphonic acid, 1-hydroxyhexadecylphosphonic acid, 1-hydroxyheptadecylphosphonic acid, 1-hydroxyoctadecylphosphonic acid, 1-hydroxynonadecylphosphonic acid, 1-hydroxyico Examples thereof include silphosphonic acid, 1-hydroxyhenicosylphosphonic acid, and 1-hydroxydocosylphosphonic acid.

The alkylphosphonic acid compound is physically adsorbed 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.
The two-frequency driving liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm constituting the display composition 8 has a certain frequency (crossover frequency: f _c ) with an applied voltage as a boundary point. the applied voltage of the low frequency f _L indicates a positive dielectric anisotropy, the applied voltage f _c higher frequency f _H is composed of a negative nematic liquid crystal compound showing a dielectric anisotropy and a chiral agent, the helical pitch The size of can be adjusted by 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 and a frequency f _L. Further, a planar orientation in a light selective reflection state is formed by applying / cutting off a voltage having a frequency f _H indicating a negative dielectric constant.

  In particular, the focal conic alignment and the planar alignment of the dual frequency driving liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm are preferably combined with the vertical alignment liquid crystal alignment film 3 made of an alkylphosphonic acid compound. In combination with the vertical alignment liquid crystal alignment film 3 made of a linear alkylphosphonic acid compound having 8 or more carbon atoms, the memory property of each alignment state is stably expressed for a long time. When an alignment film made of an alkylphosphonic acid compound having 7 or less carbon atoms is used, the memory property of the planar alignment state is not different from that in the case of using an alignment film made of an alkylphosphonic acid compound having 8 or more carbon atoms, but the focal conic alignment state. The memory performance of the camera is greatly reduced.

  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.

  In addition, the electrophoretic particles 6 move to one electrode according to the electrophoresis polarity by applying an electric field. When moving to the transparent substrate 4 side which is a display surface, the color tone of the electrophoretic display particles 6 is displayed.

  The electrophoretic particles 6 are lead white, zinc white, lipoton, titanium dioxide, zinc sulfide, antimony oxide, calcium carbonate, kaolin, mica, barium sulfate, gloss white, alumina white, talc, silica, calcium silicate, cadmium yellow. , Cadmium lipoton yellow, yellow iron oxide, titanium yellow, titanium barium yellow, cadmium orange, cadmium lipoton orange, molybdate orange, bengara, red lead, silver vermilion, cadmium red, cadmium lipoton red, amber, brown iron oxide, Zinc iron chrome brown, chrome green, chromium oxide, viridian, cobalt green, cobalt chrome green, titanium cobalt green, bitumen, cobalt blue, ultramarine, cerulean blue, cobalt aluminum chrome blue, co Selected from violet, mineral violet, carbon black, iron black, manganese ferrite black, cobalt ferrite black, copper chrome black, copper chrome manganese black, titanium black, aluminum powder, copper powder, lead powder, tin powder, zinc powder, etc. One or more inorganic pigments, fast yellow, disazo yellow, condensed azo yellow, anthrapyrimidine yellow, isoindoline yellow, copper azomethine yellow, quinophthaloin yellow, benzimidazolone yellow, nickel dioxime yellow, monoazo yellow lake, dinitro Aniline orange, pyrazolone orange, perinone orange, naphthol red, toluidine red, permanent carmine, brilliant fast scarlet, pyrazolone red Rhodamine 6G rake, permanent red, risor red, bon lake red, lake red, brilliant carmine, Bordeaux 10B, naphthol red, quinacridone magenta, condensed azo red, naphthol carmine, perylene car red, condensed azo scar red, benzimidazolone carmine, anthra Quinonyl red, perylene red, perylene maroon, quinacridone maroon, quinacridone scarred, quinacridone red, diketopyrrolopyrrole red, benzimidazolone brown, phthalocyanine green, Victoria blue lake, phthalocyanine blue, fast sky blue, alkaline blue toner, indan Thoron Blue, Rhodamine B Lake, Methyl Violet Lake, Dioxazine Violet Or one or more kinds of organic colored particles selected from naphthol violet, or composite particles in which inorganic pigments or organic colored particles thereof are attached to the surface of polymer particles or hollow polymer particles or introduced into the inside thereof.

  According to such a display medium comprising the display cell and the display composition 8, as shown in FIG. 1A, a DC voltage is applied via the electrode 2 on the substrate 1 and the transparent electrode 5 on the transparent substrate 4. Then, the electrophoretic particles 6 move to the transparent substrate 4 side according to the polarity of the electric field. At the same time, when the DC voltage is not large enough for homeotropic alignment, the dual frequency drive liquid crystal composition 7 having a helical pitch of 0.3 to 1.2 μm exhibits positive dielectric anisotropy. It has a focal conic orientation and is in a transparent state that transmits visible light. Therefore, the color tone of the electrophoretic particles 6 is displayed on the transparent substrate 4 side.

  When the application of voltage is stopped in this state, the electrophoretic particles 6 are maintained by the cohesive force between the particles and the adsorptive force between the alignment films, and an effective color tone state is maintained, and the electrophoretic particles are 0.3 to 1.2 μm. The dual-frequency driving liquid crystal composition 7 having a helical pitch maintains the focal conic alignment under the influence of the vertical alignment liquid crystal alignment film 3 and maintains a transparent state. Therefore, the display state during voltage application is stably maintained for a long time.

  Alternatively, when a DC voltage sufficient for homeotropic alignment is applied, the homeotropically aligned two-frequency drive liquid crystal composition 7 returns to the planar alignment that selectively reflects light when the voltage application is stopped. It needs to be oriented. That is, a DC voltage having the same polarity as the initial voltage is applied in a magnitude that does not cause homeotropic alignment. At this time, the electrophoretic particles 6 are maintained on the display surface because the applied voltage has the same polarity as the initial voltage. Therefore, the color tone by the favorable electrophoretic particles 6 without color mixing due to selective light reflection is displayed.

  In addition, as shown in FIG. 1B, when a DC voltage having the opposite polarity to the above is applied, the electrophoretic particles 6 move to the substrate 1 side. At the same time, the dual frequency drive liquid crystal composition 7 starts focal conic alignment due to positive dielectric anisotropy. Furthermore, when the voltage is cut off after applying a sufficient DC voltage for the homeotropic alignment of the dual frequency drive liquid crystal composition 7, the dual frequency drive liquid crystal composition 7 is planarly aligned and corresponds to the helical pitch. A color tone by selective reflection light is displayed.

  Alternatively, when the electrophoretic particles 6 move to the substrate 1 side and the two-frequency driving liquid crystal composition 7 is in focal conic orientation, a high-frequency voltage exhibiting negative dielectric anisotropy is applied. The composition 7 shifts to the planar orientation, and a colored color tone by selective reflection light corresponding to the helical pitch is displayed. At this time, the electrophoretic particles 6 remain on the substrate 1 side because the applied voltage is high frequency, and the color tone by the selectively reflected light is displayed effectively and stably.

Next, a preferred embodiment of the display medium of the present invention will be described with reference to FIG.
The substrate 1 is a transparent or colored substrate made of a glass plate or a plastic film. 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 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, a 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 the sectional view of FIG. 3A, the non-display surface 26 is provided with a magnetic recording unit 23 and an integrated circuit memory 24 on at least a part of the substrate 1, and the magnetic recording unit 23, the integrated circuit memory 24, and A second protective layer 25 is provided on the substrate 1. The second protective layer 25 is formed from a material similar to the material constituting the protective layer 11 or the print protective layer 13.

  As shown in the plan view of FIG. 3B, the transparent recording portion 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 by using a conventional technique.

  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 oriented electric field applying means has a switching element, the electric charge given to a certain 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. Can be used for a 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]
(Preparation of display medium)
A glass substrate with ITO of 1.1 mm in thickness (SuperITO-A, ULVAC Film Co., Ltd.) 1: 1: 5 hydrogen peroxide solution (about 30%), aqueous ammonia solution (about 30%) and ion exchange After immersing in a solution made of water and sonicating for about 5 minutes, the surface of ITO was cleaned by immersing in the same solution at 60 ° C. for 30 minutes. A 5 mmol solution of tetradecylphosphonic acid in dimethyl sulfoxide / ion exchange water (volume ratio 9: 1) was prepared, and a glass substrate with ITO that had been surface-treated was immersed in the solution at 40 ° C. for 21 hours. The substrate was taken out, heat-treated at 140 ° C. for 2 hours, immersed in 0.5 mol of K ₂ CO ₃ ethanol / ion exchange water (volume ratio 2: 1), sonicated for 10 minutes, and perpendicular to the surface of 10 ITO. An alignment liquid crystal alignment film was formed.
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 an inter-electrode distance of about 18 μm is formed by a polyester film, and a display cell Got.

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.
In this liquid crystal composition, 2.5 g of oleic acid was dissolved, and 12.0 g of titanium black (TilacD ultrafine particle type, manufactured by Ako Kasei Co., Ltd., Ti surface treatment product) was added to the resulting solution, followed by ultrasonic dispersion for 15 minutes. Thus, a display composition was prepared.
This display composition was poured into a display cell, and after deaeration treatment under reduced pressure, the gap between the substrates was sealed to produce a display medium.

[Example 2]
(Preparation 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 display composition was prepared in the same manner as in Example 1, and then a display medium was produced.

[Comparative Example 1]
A display medium was produced in the same manner as in Example 1 except that hexylmethoxysilane was used instead of tetradecylphosphonic acid in Example 1.

[Comparative Example 2]
A display medium was produced in the same manner as in Comparative Example 1 except that the display composition of Example 2 was used.

[Comparative Example 3]
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. In this liquid crystal composition, 2.5 g of oleic acid was dissolved, and 12.0 g of titanium black (TilacD ultrafine particle type, manufactured by Ako Kasei Co., Ltd., Ti surface treatment product) was added to the resulting solution, followed by ultrasonic dispersion for 15 minutes. Thus, a display composition was prepared. Using this display composition, a display medium was produced in the same manner as in Example 1.

[Evaluation]
(Evaluation of reflectivity of electrophoretic particle display)
A voltage of −150 V is applied to the display surface produced in Examples 1 and 2 and Comparative Examples 1 to 3 through the electrode of the medium to move the electrophoretic particles to the display surface, and the liquid crystal composition After the object was homeotropically oriented, the electric field was removed.
Next, a voltage of −50 V was applied to cause the liquid crystal composition returned to the planar alignment to be in a focal conic alignment, and then the electric field was removed to display a color tone depending on the electrophoretic particles.
In the color tone display depending on the electrophoretic particles, the display medium is placed on a standard white plate within 10 minutes after the display operation, and the display medium is irradiated with 45 ° irradiation-vertical light reception using Photo MCPD-1000 manufactured by Otsuka Electronics Co., Ltd. Was measured in the wavelength region of 380 to 800 nm, and the reflectance of the electrophoretic particle display was calculated with the reflectance of the standard white plate as 100%. The results are shown in Table 1.

(Evaluation of reflectance and contrast ratio of selective reflected light display)
A voltage of +150 V was applied to the display surface side through the electrode of the medium to move the electrophoretic particles to the non-display surface, and the liquid crystal composition was homeotropically aligned, and then the electric field was removed.
Next, an AC voltage of 50 V (50 kHz) was applied to sufficiently planarize the 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 display medium is placed on a standard white plate within 10 minutes after the display operation, and the reflected light of the display medium is 380 to 800 nm by 45-degree irradiation-vertical light reception using MCPD-1000. The reflectance at the peak wavelength of the selectively reflected light 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 20 or more, but in Comparative Examples 1 and 2, color mixing due to selective reflected light occurred in electrophoretic particle display, and sufficient reflectance was achieved. Was not obtained. In Comparative Example 3, the selective reflection did not occur, so the contrast ratio was 1.
From these results, it became clear that a display medium with high visibility can be obtained by using the display medium of the present invention.

[Example 3]
[Production of display medium]
A glass substrate with ITO of 1.1 mm in thickness (SuperITO-A, ULVAC Film Co., Ltd.) 1: 1: 5 hydrogen peroxide solution (about 30%), aqueous ammonia solution (about 30%) and ion exchange After immersing in a solution made of water and sonicating for about 5 minutes, the surface of ITO was cleaned by immersing in the same solution at 60 ° C. for 30 minutes. A 5% by volume (α-hydroxyoctadecyl) phosphonic acid solution in dimethyl sulfoxide / ion exchange water (volume ratio 5: 5) was prepared, and the washed glass substrate with ITO was immersed in the solution at 40 ° C. for 24 hours. The substrate was taken out, heat-treated at 140 ° C. for 2 hours, immersed in 0.5 mol of K ₂ CO ₃ ethanol / ion exchange water (volume ratio 2: 1), sonicated for 1 minute, and perpendicular to the ITO surface. An alignment liquid crystal alignment film was formed.
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.
In this liquid crystal composition, 2.5 g of oleic acid was dissolved, and 12.0 g of titanium black (TilacD ultrafine particle type, manufactured by Ako Kasei Co., Ltd., Ti surface treatment product) was added to the resulting solution, followed by ultrasonic dispersion for 15 minutes. Thus, a display composition was prepared.
This display composition was poured into a display cell, and after deaeration treatment under reduced pressure, the gap between the substrates was sealed to produce a display medium.

[Example 4]
[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 display composition was prepared in the same manner as in Example 3, and then a display medium was produced.

[Comparative Example 4]
A display medium was produced in the same manner as in Example 3 except that hexylmethoxysilane was used instead of (α-hydroxyoctadecyl) phosphonic acid in Example 3.

[Comparative Example 5]
A display medium was produced in the same manner as in Comparative Example 4 except that the display composition of Example 4 was used.

[Comparative Example 6]
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. In this liquid crystal composition, 2.5 g of oleic acid was dissolved, and 12.0 g of titanium black (TilacD ultrafine particle type, manufactured by Ako Kasei Co., Ltd., Ti surface treatment product) was added to the resulting solution, followed by ultrasonic dispersion for 15 minutes. Thus, a display composition was prepared. Using this display composition, a display medium was produced in the same manner as in Example 3.

[Evaluation]
(Evaluation of reflectivity of electrophoretic particle display)
A voltage of −150 V is applied to the display surface produced in Examples 3 and 4 and Comparative Examples 4 to 6 on the display surface side through the electrodes of the medium to move the electrophoretic particles to the display surface, and the liquid crystal composition After the object was homeotropically oriented, the electric field was removed.
Next, a voltage of −50 V was applied to cause the liquid crystal composition returned to the planar alignment to be in a focal conic alignment, and then the electric field was removed to display a color tone depending on the electrophoretic particles. In the color tone display depending on the electrophoretic particles, the display medium is placed on a standard white plate within 10 minutes after the display operation, and the display medium is irradiated with 45 ° irradiation-vertical light reception using Photo MCPD-1000 manufactured by Otsuka Electronics Co., Ltd. Was measured in the wavelength region of 380 to 800 nm, and the reflectance of the electrophoretic particle display was calculated with the reflectance of the standard white plate as 100%. The results are shown in Table 1.

(Evaluation of reflectance and contrast ratio of selective reflected light display)
A voltage of +150 V was applied to the display surface side through the electrode of the medium to move the electrophoretic particles to the non-display surface, and the liquid crystal composition was homeotropically aligned, and then the electric field was removed.
Next, an AC voltage of 50 V (50 kHz) was applied to sufficiently planarize the 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 display medium is placed on a standard white plate within 10 minutes after the display operation, and the reflected light of the display medium is 380 to 800 nm by 45-degree irradiation-vertical light reception using MCPD-1000. The reflectance at the peak wavelength of the selectively reflected light 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 2, Examples 3 and 4 showed a contrast ratio of 20 or more, but in Comparative Examples 4 and 5, color mixing due to selective reflected light occurred in electrophoretic particle display, and sufficient reflectance was achieved. Was not obtained. In Comparative Example 6, the selective reflection did not appear, so the contrast ratio was 1.
From these results, it became clear that a display medium with high visibility can be obtained by using the display medium of the present invention.

  Since the display medium of the present invention can display with high visibility, it can be suitably used in various applications including cards, sheets, displays, signboards, and advertisements.

It is sectional drawing which shows an example of the form of the display medium which concerns on this invention. (A) shows the state which electrophoretic particle moves to the transparent substrate side according to the polarity of an electric field. (B) shows a state in which the electrophoretic particles move to the substrate side according to the polarity of the electric field. 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 by this invention, (a) is sectional drawing, (b) is a top view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Electrode 3 Vertical alignment liquid crystal aligning film 4 Transparent substrate 5 Transparent electrode 6 Electrophoretic particle 7 Dual frequency drive liquid crystal composition 8 Display composition 11 Protective layer 12 Print layer 13 Print 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 x _{1 to} x ₇ Row number of transparent recording portion of grid shape y _{1 to} y ₉ Column of transparent recording portion of grid shape number

Claims (16)

  A display medium comprising a display cell and a display composition contained in the display cell, wherein the display cell is composed of an electrode on one surface and an alkylphosphonic acid compound formed on the electrode surface. A substrate having a film, and a transparent substrate having a transparent electrode on one surface and a vertically aligned liquid crystal alignment film made of an alkylphosphonic acid compound formed on the transparent electrode surface. A display medium comprising a dual-frequency driving liquid crystal composition having a helical pitch of 3 to 1.2 μm and electrophoretic particles.   The display medium according to claim 1, wherein the alkylphosphonic acid compound is α-hydroxyalkylphosphonic acid.   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 at least a part of the protective layer.   The display medium according to claim 4, wherein a print protective layer is provided on the print layer.   6. The display medium according to claim 1, further comprising an information recording unit.   The display medium according to claim 6, 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 6 or 7, wherein the information recording unit is an integrated circuit memory or an optical memory.   9. The display medium according to claim 6, wherein the information recording unit is a transparent recording unit capable of reading out information recording by the action of light.   The display medium according to claim 6, 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 10 and a writing device capable of displaying visible information on the display medium, wherein the display medium and the writing device are attached and detached so as to be close at least during writing. 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 the intersection thereof. A display device configured to display an image on a display medium.   The display device according to claim 11, 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.   A reversible display, wherein the display medium according to claim 1 and a thin film transistor are integrated.   The reversible display body, wherein the display medium according to claim 1 occupies a part or all of the display medium.   15. The reversible display body according to claim 14, 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 15, wherein the reversible display card, the reversible display sheet, the reversible display, or the reversible display type signboard has flexibility.

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