JP2002107772A - Display element - Google Patents

Abstract

(57) [Problem] To provide a display element using a gel, which is superior in contrast and response speed as compared with the conventional display element. SOLUTION: The display device has a light-transmitting display-side substrate, a non-display-side substrate opposed thereto, a liquid contained between the two substrates, and a gel that swells / shrinks or bends in response to an external stimulus,
A display element in which display is performed by adjusting incident light due to deformation of a gel, wherein wettability between a liquid and a display-side substrate surface in contact with the liquid is set to be low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display element utilizing deformation of a gel.

[0002]

2. Description of the Related Art At present, self-luminous display devices such as CRTs, plasma displays, EL displays, and fluorescent display tubes, and non-luminous display devices such as liquid crystal displays utilizing reflected light and transmitted light are available as display elements. Yes, each has been put to practical use. In recent years, with the development of information systems, the VDT (Visual Data Term) for a long time
inal) work is increasing rapidly, and a non-light emitting display screen is desirable in view of fatigue. For this reason, liquid crystal displays have recently become widespread, replacing CRTs, but have a narrow viewing angle and insufficient contrast between light and dark. In order to solve such a problem, there has been proposed a display element which uses a gel which swells / shrinks or bends in response to an external stimulus, and performs display by adjusting incident light by deformation of the gel ( JP-A-61-14992
No. 6, JP-A-63-13021, JP-A-9-
No. 160081). These technologies are based on the phenomenon that the polymer gel absorbs and swells or drains and shrinks, or bends, due to external stimuli such as temperature, electric field, light, pH, ion concentration, and solvent composition. The display is performed by adjusting the incident light for each pixel to provide a contrast. Such a scheme is
Unlike liquid crystal displays, they have a wide viewing angle and do not require a deflecting plate, so they are excellent in terms of light use efficiency and brightness, but they are excellent in contrast and response speed (speed of gel expansion and contraction).
Is not enough.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a display device using a gel, which is superior in contrast and response speed as compared with the prior art.

[0004]

Means for Solving the Problems The above problems are as follows:
15) (hereinafter referred to as the present invention 1 to 15). 1) It has a light-transmitting display-side substrate, a non-display-side substrate opposed thereto, a liquid contained between the two substrates, and a gel that swells / shrinks or bends in response to an external stimulus. Wherein the wettability between a liquid and a display-side substrate surface in contact with the liquid is set to be low. 2) The display element according to 1), wherein the receding contact angle between the liquid and the display-side substrate surface in contact with the liquid is 50 ° or more. (3) The display element according to (1) or (2), wherein the display side substrate surface in contact with the liquid is subjected to liquid generation processing. 4) The display element according to 1) or 2), wherein wettability between the liquid and the display-side substrate surface in contact with the liquid is set to be variable by an external stimulus. 5) The display element according to 4), wherein the wettability between the liquid and the display-side substrate surface in contact with the liquid is set so as to change in conjunction with an external stimulus that causes deformation of the gel. 6) A conductive polymer compound layer is provided on the display-side substrate surface in contact with the liquid, and ions are doped and de-doped by an electric field to control wettability with the liquid, and deform the gel to form a conductive layer. The display element according to 5), wherein the liquid crystal is set so that the wettability with a liquid is reduced when the liquid crystal panel contacts a display-side substrate having a polymer compound layer. 7) The display element according to any one of 1) to 6), wherein the liquid contained between the substrates is colored. 8) The display element according to any one of 1) to 7), wherein the external stimulus for deforming the gel is an electric field. 9) The display element according to 8), wherein at least a portion of the gel that is in contact with the display-side substrate surface is insulative, and another portion of the gel is conductive. 10) The display element according to 9), wherein the length of the conductive portion when the gel swells is at least 1/3 or more of the internal thickness of the element. 11) When the insulating portion of the gel contracts, the thickness of the liquid contained between the two substrates is 400 nm or more, which allows the liquid to pass through.
The display element according to 9) or 10), wherein the distance between the gel and the display-side substrate surface is set so that the average transmittance of 700 nm visible light is 50% or more. 12) The display element according to any one of 9) to 11), wherein the gel contains a conductive polymer compound. 13) The display element according to 12), wherein the conductive polymer compound is compounded in a gel by an electrolytic polymerization method. 14) The display element according to any one of 9) to 13), wherein the display-side substrate surface in contact with the liquid has low wettability with the liquid and also serves as an insulating layer. 15) A conductive polymer compound layer is provided on the display-side substrate surface in contact with the liquid, and ions are doped and de-doped by an electric field, so that wettability with the liquid is controlled and gel is formed on the display-side substrate surface. The display element according to any one of 9) to 14), wherein the conductive polymer compound is set so as to be undoped and in an insulator state when it comes into contact.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a reflection type display element by electric field control using a gel. However, in the present invention, the control method is not limited to an electric field, and if a type of gel is selected, it is possible to use a transmission type instead of a reflection type. is there. However, in view of driving of the display device, an electric field is practically preferable. In the case of electric field control, electrodes are provided above and below the pixel and an electric field is applied, and the gel contacts with a transparent electrode such as ITO, which has strong hydrophilicity, and is stored between the substrates. More preferably, the liquid is aqueous. Further, in the present invention, in addition to the method shown in FIG. 1, the display between the display side substrate and the liquid contained between the substrates is controlled by the deformation of the gel, such as one using the bending of a polymer gel. Any known method that has been proposed in the past can be used.

In the display device shown in FIG. 1, a gel and a liquid are arranged between a pair of substrates, at least one of which is transparent, and the gel absorbs a solvent and swells or a solution is discharged and contracts depending on how an electric field is applied. The display is performed by adjusting the incident light for each pixel to obtain a contrast by utilizing the phenomenon of the above. At this time, for example, if the gel is colored white and the liquid is colored black, or if the gel is colored black and the liquid is colored white, only the solvent can pass through the gel, so that black and white display can be performed. Color display is also possible if the gel or liquid is colored in three primary colors of RGB (red, green, blue) instead of black, and color display is possible even by using a color filter. In this example, the driving method is such that the electric field is ON (applied) only when the gel is contracted or elongated, and there is no electric field in the other cases. However, depending on the type of the gel, the electrode on the display side is an anode when the gel is contracted. , So that the opposing electrode is a negative electrode,
A driving method in which an electric field is applied such that the electrode on the display side becomes a negative electrode and the electrode facing the anode becomes an anode when the gel elongates, and vice versa is also possible.

In such a display device, the contrast and the response speed were examined. As for the contrast, when the gel and the display side substrate contacted, a liquid remained between the gel and the display substrate. I found that I couldn't get it. Therefore, as a result of studying to solve this problem, it was found that by setting the wettability of the display-side substrate surface in contact with the liquid to be low, an image with high contrast was obtained without liquid remaining between the gel and the display-side substrate. . Regarding the response speed, it was found that the higher the electric field strength, the faster the gel expands and contracts. However, since the gel generally does not have sufficient conductivity, the top end of the gel and the display side substrate The electric field strength (E1) applied to the transparent electrode becomes smaller than the electric field strength (E0) originally applied between the electrodes. Then, as a result of studying to solve this problem, as shown in FIG. 2, it was found that the gel can be solved by making at least the gel in contact with the display-side substrate surface insulative and making the gel in other portions conductive. . According to this configuration, when a part of the gel is conductive and has sufficient conductivity, E0 = E2 can be satisfied, and the internal thickness of the cell in the configurations of FIGS. When the values are the same, a larger electric field can be applied to the gel insulating portion of FIG. 2 than in the case of FIG. 1, so that the response speed can be improved.

The gel which can be used in the present invention and which is deformed by an external stimulus is, for example, a liquid-absorbing polymer which absorbs a liquid and swells and discharges and contracts the liquid.
Examples include polyether, polyvinyl alcohol, cellulose, starch, and polyacrylic acid-based materials obtained by graft-polymerizing a crosslinkable monomer such as N, N-methylenebisacrylamide. Preferred are a crosslinkable polymer obtained by polymerizing a crosslinkable monomer, a copolymer of methyl methacrylate and acrylic acid, a polyacrylate, and the like. Examples of the polymer that bends due to an external stimulus include a polyacrylic acid-polyvinyl alcohol composite. To color the gel, pigment particles such as carbon and pigment may be immobilized in the gel or on the display surface side of the gel by adsorption, bonding, or the like.

In order to make such a gel conductive, a conductive substance may be mixed into the gel, but a gel made of a conductive compound may be used. The mixing of conductive materials
After dispersing the conductive material during the liquid state before gelation,
It can be performed by gelling. As the conductive substance, a metal, a metal oxide, a metal nitride, a conductive organic substance, or the like can be used. Specifically, Au, Pt, Ag, C
metal particles such as u, Fe, Al, Ti, In ₂ O ₃ , Sn
O ₂ , ZnO, CdO, TiO ₂ , In ₂ O ₃ —Sn,
Examples include oxides such as SnO ₂ —Sb, nitrides such as TiN and ZrN, and organic substances such as graphite and conductive polymer compounds, which need to be electrochemically stable under an applied electric field. . Further, the shape is preferably fine particles.

[0010] Among these conductive substances, a conductive polymer compound is preferable. This is because, since they are the same organic substance, they have good affinity for the gel which is the base material and can stably exist as a complex. It is liquid before gelation,
Since the dispersion can be easily stabilized during the liquid state, it is preferable to use a conductive polymer compound also from the viewpoint of gel synthesis. The conductive polymer compound used for the composite is not particularly limited, and examples thereof include a five-membered heterocyclic compound, a condensed polycyclic compound, and a polymer of an amine compound. Specifically, polypyrrole, polythiophene, polyphenylene,
Polyazulene, polyaniline, polydiphenylbenzidine, polyisothionaphthene and derivatives thereof can be exemplified, and polyaniline and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives are preferred from the viewpoint of high conductivity and stability, and the most preferred is Polyaniline, polypyrrole, and poly (3-methylthiophene). Since these compounds are used in a conductive state, it goes without saying that they are in a doped state. Further, it is preferable to use a polymer dopant which is not easily dedoped by an applied electric field for the ion species as a dopant.

As a method for producing a gel having a conductive part and an insulating part as shown in FIG. 2, for example, a pre- (precursor) solution of a conductive gel containing a conductor is applied to a substrate,
Applying energy such as heat and ultraviolet rays to form a conductive gel film, then applying a pre-solution of an insulating gel containing no conductor thereon, and applying heat and ultraviolet light to create a gel film Can be made. As described above, according to the configuration of FIG. 2, when a part of the gel is conductive and has sufficient conductivity, E0 = E2 can be satisfied, and the response speed is improved. However, since the gel conductive portion is usually less conductive than the electrodes (ITO, metal, etc.), a voltage drop occurs to some extent at the conductive gel, and substantially E
0 ≧ E2. However, the difference is smaller than the configuration of FIG. In this case, an electric field is also applied to the conductive portion of the gel, so that the conductive portion of the gel also slightly shrinks depending on the degree of conductivity of the gel. The length of the conductive part of the gel depends on its conductivity, but it is 1 of the internal thickness of the cell.
/ 3 or more.

When a conductive polymer compound is selected as the conductive substance to be mixed into the gel, the gel can be combined with the conductive polymer compound by an electrolytic polymerization method. In this case, the insulating gel is immersed in an electrolytic solution for electrolytic polymerization, and after the monomer is sufficiently diffused in the gel, by applying an electric field, a conductive polymer compound is generated from the electrode surface, The conductive polymer compound can grow in the gel over time. This method is capable of providing a gel having higher conductivity than a method of preparing a conductive gel by dispersing conductive particles in the gel, and is basically based on an electrolytic reaction. The feature is that conductivity can be selectively provided only on the electrode.

The above-mentioned electrolytic polymerization method refers to, for example, chemical industry 19
June 1986, p. 43, Polymer 35, February (198
6) As shown on page 124 and the like, a method in which a monomer and an electrolyte are dissolved in a solvent and put in a predetermined electrolytic cell, the electrodes are immersed, and a polymerization reaction is caused by anodic oxidation or cathodic reduction through electric current. It is. As the electrolytic polymerization method, any of constant voltage electrolysis, constant current electrolysis, and constant potential electrolysis may be used, but constant current electrolysis and constant potential electrolysis are preferable, and constant current electrolysis is particularly preferable in terms of mass productivity.

As the monomer, a monomer that gives the above-described conductive polymer compound is used. Examples of the electrolyte include BF ₄ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , PF ₆ ⁻ ,
Halogen anions such as ClO ₄ ⁻ , HSO ₄ ⁻ , SO ₄ ²⁻ , aromatic sulfonic acid, Cl ⁻ , Br ⁻ , I ⁻ , polymer anion, or H ⁺ , quaternary ammonium cation, Li, Na, K And the like, but are not limited thereto.

Examples of the solvent include water, acetonitrile, benzonitrile, propylene carbonate, γ-butyrolactone, dichloromethane, dioxane, dimethylformamide, and nitro solvents such as nitromethane, nitropropane, and nitrobenzene. It is not limited to these. These can be used in combination of two or more.

An example of the gel made of a compound having conductivity is a gel of a conductive polymer compound. As the name implies, a gel of a conductive polymer compound has both properties as a conductive polymer compound and properties as a gel, and its structure is a crosslinked conductive polymer compound. Specifically, a three-dimensional structure is obtained by adding a small amount of a cross-linking agent to a five-membered heterocyclic compound, a condensed polycyclic compound, an amine compound, or the like as a monomer and performing polymerization. Such a material has conductivity in a doped state, and also exhibits a gel behavior of contracting in a doped state and expanding in a undoped state, and is a gel that can be preferably used.

The thickness of the insulating gel located above the conductive gel is determined when the liquid enters between the display-side substrate and the upper surface of the gel when the gel contracts (ON state shown in FIG. 2), and when the gel elongates. It is necessary that the thickness be such that a sufficient contrast can be obtained between the case where is in contact with the display side substrate surface (OFF state shown in FIG. 2). The thickness of the liquid, which should be appropriately set depending on the type of the gel and the liquid to be used, and cannot be unconditionally determined. Do 40
Setting the distance between the gel and the display-side substrate surface (the distance at which liquid enters) so that the average transmittance of visible light of 0 nm to 700 nm is equal to or greater than the thickness of 50% is a contrast of the display element. It is preferable to obtain

The liquid contained between the two substrates must have a property of being absorbed in the gel, and when the gel is used by coloring, it is preferably colorless or pale. Water, alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, aprotic polar solvents such as N-methylpyrrolidone and N, N-dimethylformamide, carbon tetrachloride,
Examples include halogenated hydrocarbons such as chloroform, ethers such as tetrahydrofuran and diethyl ether, and hydrocarbons such as isopentane and benzene. The present invention suppresses the wettability between these liquids and the display-side substrate. For this purpose, as described later, the surface of the substrate in contact with the liquid is surface-treated, or a new layer is provided to form the wettability. There is a method of adjusting the temperature or a method of selecting a solvent according to the substrate. In any case, the selection of the solvent is important.

When the liquid is used after being colored, a dye that does not enter the gel is used by dispersing it in the above-mentioned solvent (using a surfactant or the like, if necessary). that time,
The dye to be used is not particularly limited and may be a known dye, and a general dispersion method or the like may be used. Therefore, known hydrophilic inks, lipophilic inks and the like can also be used. Further, the liquid is used by adding an electrolyte salt such as sodium chloride, potassium chloride, calcium chloride, ammonium chloride and lithium perchlorate as necessary.

The substrate must be transparent on the display side, and a glass, transparent plastic film, or the like is used. The wettability of the surface in contact with the liquid inside is important. In the case of a transmissive display element, a transparent substrate similar to the display side is used as the substrate on the side opposite to the display side, and in the case of a reflective display element, the gel itself has a reflection function by whitening the gel. A transparent substrate similar to that on the display side may be used when making the display, and Al or SUS is used when the gel does not have a reflection function.
A metal plate such as (stainless steel) or a substrate having a metal film such as Al or Cr formed on a glass or plastic film to enhance the reflection effect is used.

When the external stimulus is an electric field, an electrode is required to accompany the substrate. As an electrode to be used, a transparent electrode is required on the display substrate side, and In ₂ O ₃ , SnO ₂ ,
_{ZnO, CdO, TiO 2, In} 2 O 3 -Sn, SnO
Known materials such as an oxide thin film such as _2- Sb and a conductive nitride thin film such as TiN and ZrN are used. On the other hand, examples of the electrode used on the substrate on the side opposite to the display side include a metal thin film such as Pt, Au, Cu, and Al, in addition to the transparent electrode.

In the present invention, the wettability between the liquid and the display-side substrate surface in contact with the liquid is reduced. The low wettability herein refers to the state in which the liquid and the display-side substrate surface in contact with the liquid. It is desirable that the contact angle with the receding contact angle is 50 ° or more. As shown in FIG. 3, the contact angle refers to the angle between the surface of the droplet and the surface of the solid, which includes the droplet, and the receding contact angle refers to the angle at which the liquid drops. This is determined by sucking the liquid after wetting and then measuring the contact angle of the remaining liquid droplet by enlarging it with an optical system.

In order to set the receding contact angle to 50 ° or more, it is very effective if the surface of the display-side substrate which is in contact with the liquid has been subjected to liquid generation processing. Also, if the wettability can be changed by an external stimulus such as heat or an electric field, it is very convenient because the wettability can be controlled even when the liquid used is changed,
The effect is further enhanced if it can be changed in conjunction with an external stimulus that causes gel deformation. That is, when the gel contacts the display side substrate and the gel, the wettability between the substrate and the liquid decreases and when the gel separates from the substrate, the substrate comes into contact with the liquid and the wettability increases. It is possible to improve the contrast.

Means for changing the wettability include:
It is effective to provide a conductive polymer compound layer on the display-side substrate surface in contact with the liquid. The conductive polymer compound is doped and undoped with ions by an electric field, and the wettability of the surface changes. Further, the gel may be deformed simultaneously with the applied electric field. In this case, when the gel contacts the conductive polymer compound, the conductive polymer compound is in an insulated state and When the wettability is low (de-dope state) and the gel is separated from the conductive polymer compound, the conductive polymer compound is in a conductive state and has a high wettability (doped state). Further, in the present invention, among the display elements utilizing the deformation of the gel, in particular, in the case of the type in which the liquid to be stored between the substrates is colored in order to cause a problem of liquid remaining between the gel and the display side substrate. Great effect.

Next, a method for reducing the wettability between the display-side substrate and the liquid contained between the substrates is as follows. The surface of the substrate in contact with the liquid is surface-treated, or a new layer is provided to adjust the wettability. And a method of selecting a combination of a substrate and a solvent. To explain the former in more detail, first, it is conceivable to make the surface of the substrate in contact with the liquid hydrophobic if the liquid used is hydrophilic, or hydrophilic if the liquid used is lipophilic. Hydrophobicization of the substrate can be achieved, for example, by providing a polymer layer containing a hydrophobic group such as an alkyl group, or by performing a surface treatment using a silane-based or titanium-based coupling agent. The hydrophilicity of the substrate can be achieved by providing a polymer layer containing a hydrophilic group such as a sulfonic acid group, a carboxyl group, a hydroxyl group, an amino group, and a cyano group. Further, it is preferable that any liquid is subjected to an effective liquefaction treatment because it can be used regardless of the type of liquid.
Liquefaction can be achieved by, for example, providing a polymer layer having a fluoroalkyl group, a siloxane group, or the like, but is not particularly limited as long as the desired liquid repellency can be obtained.

As the polymer having a fluorinated alkyl group,
Fluorinated resins such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer are exemplified. Examples of the polymer having a siloxane group include silicone resins such as dimethyl silicone, methyl phenyl silicone, amino-modified silicone, epoxy-modified, carboxyl-modified, methacryl-modified, phenol-modified and alkyl-modified silicone. . These polymers are dissolved or dispersed in a solvent, and the surface of the substrate is liquefied, for example, by immersing the substrate. In addition, sol-gel method, virosol method, CVD
(Chemical vapor deposition), vacuum deposition, ion plating or the like may be used to form the liquefied layer.

As a further preferred embodiment of the present invention, there is a method of changing the wettability by an external stimulus such as heat or an electric field. To change the wettability, a so-called planographic printing technique can be used. For example, a copolymer layer composed of a polymer containing a fluorinated alkyl group and / or a siloxane group and a polymer containing a hydrophilic group is formed on the surface of the display-side substrate in contact with the liquid, and is housed between the substrates by heating. Change the wettability to liquid or chemically treat the surface of the polyolefin film or sheet to introduce sulfonic acid groups to make the surface hydrophilic, and then remove some or most of the sulfonic acid groups by heating. It is made hydrophobic to change the wettability with the liquid contained between the substrates. Other than these lithographic techniques, there is no particular limitation as long as it is a technique that changes wettability.

For example, a conductive polymer compound is also a material that can be used for such a purpose, and since it has different surface energies in a doped state and a undoped state and different wettability to a liquid, the doped and undoped states can be used in an electric field. Thus, the wettability to the liquid can be controlled by electrochemically controlling the pressure. In this case, as shown in FIG. 4, at the same time as controlling the deformation of the gel by the electric field, by doping and undoping ions, the gel is deformed and comes into contact with the display-side substrate having the conductive polymer compound layer. When the display-side substrate comes into contact with the gel, the wettability with the liquid decreases, and when the display-side substrate comes into contact with the liquid, the wettability with the liquid increases. It is very effective because it can. FIG. 4 shows an example in which an aqueous colored liquid is used. However, an oil-based colored liquid can be implemented by changing the type of gel, the electric field of an external stimulus, and the like.
Examples of conductive polymer compounds include polyaniline, polypyrrole, polythiophene, polyazulene, polyphenylene, polyacetylene, and polyacene (acid resistance and chemical resistance obtained by a special thermal condensation reaction of phenolic resin).
Conductive polymer compound with excellent heat resistance. ), Polyphthalocyanine, poly (3-methylthiophene), polypyridine, polydiphenylbenzidine, and other high-molecular compounds, and derivatives thereof.

[0029]

The present invention will be described below in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A silane coupling agent was formed on a glass substrate 1 (see FIG. 5) on which an ITO electrode was formed by a sputtering method.
A 0.5% ethanol solution of γ-aminopropyltrimethoxysilane (Nihon Unicar A1110) was applied, and 10
The surface was subjected to a coupling treatment by heating at 0 ° C. for 10 minutes to perform a hydrophobic treatment. A surface subjected to this hydrophobic treatment,
When the contact angle (receding contact angle) of the black aqueous ink used in this example was measured, it was 62 °. Next, acrylamide / acrylic acid / vinyl alcohol / titanium oxide (average particle size: 0.2 μm) was used in a molar ratio of 659/40/1 /
The solution was mixed at 200 and copolymerized by adding ammonium persulfate as an initiator.
About 3 μm was applied onto the glass substrate 2 on which TO was formed, and crosslinked by heating to form an acrylic acid-acrylamide copolymer white gel. Next, a 10 μm glass substrate 1 and a glass substrate 2 were arranged as spacers at the periphery.
The mylar film was sandwiched, and the periphery was sealed to form an empty cell. The cell was filled with a black aqueous ink containing an electrolyte to swell the gel, thereby obtaining an evaluation cell as shown in FIG. In this state, the gel is in contact with the electrodes of the display-side substrate 1 and shows white display. When a voltage of 3 V is applied to the evaluation cell with the electrode on the substrate 2 side being + and the electrode on the substrate 1 side being-, the gel shrinks and separates from the display side substrate 1 and is filled with black ink. Black display was shown from the display substrate side. Next, when the electric field is turned off, the gel returns to the original swelling state, and the first white display can be confirmed again,
The contrast between white and black determined from the reflectance was 9.6. Even when the electric field was repeatedly turned ON and OFF many times, the contrast between white and black was firmly maintained.

Example 2 4.8 g of N-isopropylacrylamide, 0.1 g of acrylic acid, 80 m of N, N-methylenebisacrylamide
g and 40 mg of ammonium persulfate were mixed with 60 ml of cold water, 150 μl of tetramethylethylenediamine was added, and the mixture was degassed under reduced pressure to obtain a monomer solution. Glass substrate 1
Then, the same surface treatment as in Example 1 was performed, and a 10-μm mylar film disposed as a spacer on the periphery was sandwiched between this and another glass substrate 2 on which Al was deposited, and the periphery was sealed to form an empty cell. did. After filling the cell with the monomer solution and leaving it at room temperature for 30 minutes to gel,
The same black aqueous ink as in Example 1 was added to obtain an evaluation cell as shown in FIG. In this case, the glass substrate without electrodes is the display side, and the electrodes on the glass substrate 2 act as a resistance heating layer. The gel swells and is in contact with the display-side substrate 1, and the incident light is reflected on the Al electrode surface to show a bright display. The contact angle of the display side substrate with respect to the black aqueous ink is the same as in the first embodiment. An electric pulse signal with a frequency of 1 kHz (pulse height 20) is applied to the electrodes of this evaluation cell.
V, a pulse length of 5 msec), the gel contracted and separated from the display-side substrate 1, which was filled with black ink, and a black (dark) display was shown from the display substrate side. Next, when the pulse signal is turned off, the gel returns to its original swelling state,
The first bright display was again confirmed, and the contrast between light and dark determined from the reflectance was 9.0. Even when the electrical pulse signal was repeatedly turned ON and OFF many times, the contrast between light and dark was firmly maintained.

Example 3 A 5% solution of Cytop CTX-805A (Asahi Kasei Corporation), which is a thermoplastic resin having a perfluoro structure, was placed on a glass substrate on which an ITO electrode was formed in the same manner as in Example 1. -Solv. A solution diluted to 0.1% with 100 (manufactured by Asahi Kasei Corporation) was applied, and dried by heating at 150 ° C. for 2 hours to perform a liquid generation treatment. The contact angle (receding contact angle) between the liquid-treated surface and the black oil-based ink used in this example was measured and found to be 84 °.
Next, N, N-dimethylaminopropylacrylamide 3
g, methylenebisacrylamide 0.1 g, azobisisobutyronitrile 0.1 g, titanium oxide (average particle diameter 0.2 μm) 0.5 g, dimethylformamide (DM
F) 15 ml was mixed and polymerized at 60 ° C. for 24 hours to produce a white poly N, N-dimethylaminopropylacrylamide gel. This was introduced into the same evaluation cell as in Example 1, and subsequently, tetracyanoquinodimethane (TC
After adding a DMF solution of NQ) to swell the gel, a black oil-based ink was added to prepare an evaluation cell. When a voltage under the same conditions as in Example 1 was applied to this evaluation cell, the gel shrank and separated from the display side substrate, which was filled with black ink, and black display was shown from the display substrate side.
Next, when the electric field was cut off, the gel returned to the original swelling state, white display was confirmed, the first white display was confirmed again, and the contrast between white and black determined from the reflectance was 11.2.
Even when the electric field was repeatedly turned ON and OFF many times, the contrast between white and black was firmly maintained.

Example 4 A polypyrrole thin film was formed on a glass substrate on which an ITO electrode was formed in the same manner as in Example 1 by a known electrolytic polymerization method.
Thereafter, an evaluation cell was prepared using the same gel as in Example 1. In this case, when no electric field is applied, polypyrrole exhibits hydrophobicity in the undoped state, and the contact angle (receding contact angle) with the aqueous black ink used in this embodiment is 59 °.
Although the wettability is low, when an electric field is applied, doping of anions occurs, the hydrophilicity is changed, and the contact angle (receding contact angle) with the black aqueous ink becomes 35 °, thereby improving the wettability. That is, a cell having a variable wettability display-side electrode that has good wettability with ink during dark display when voltage is applied, and has low wettability with ink during bright display without voltage applied. It is. Example 1 for this cell
When the same evaluation was performed, the brightness obtained from the reflectance,
The dark contrast was 8.7. In addition, electric field ON,
Even if the OFF operation was repeated many times, the contrast between light and dark was firmly maintained.

Comparative Example 1 In Example 1, the ITO surface on the glass substrate was not subjected to the hydrophobizing treatment with the silane coupling agent, and the contact angle with the liquid used in Example 1 (receding contact angle) was obtained.
Was 14 °. Using this substrate, an evaluation cell similar to that of Example 1 was prepared and evaluated. When the cell changed from a black state where an electric field was applied to a white state where no electric field was applied, the black ink swelled while adhering to the display-side electrode surface. Since the gel was in contact with the electrode surface, a bright white display was not obtained, and the black and white contrast was reduced to 6.5.

Comparative Example 2 In Example 2, the glass substrate was not subjected to a hydrophobizing treatment with a silane coupling agent.
The contact angle (receding contact angle) with the liquid used in the above was 10 °. Using this substrate, an evaluation cell similar to that of Example 2 was prepared and evaluated. When the state changed from a dark state in which an electric signal pulse was applied to a light state in which no electric signal was applied, black ink remained attached to the display-side electrode surface. Since the swollen gel was in contact with the electrode surface, a bright bright display was not obtained, and the contrast between light and dark was reduced to 5.6.

Comparative Example 3 In Example 3, the liquid surface was not treated with a thermoplastic resin having a perfluoro structure on the ITO surface on the glass substrate, but the contact angle with the liquid used in Example 3 (receding contact) Corner) was 22 °. Using this substrate, an evaluation cell similar to that of Example 3 was prepared and evaluated. When the cell changed from a black state in which an electric field was applied to a white state in which no electric field was applied, the black ink swelled while adhering to the display-side electrode surface. Since the gel thus contacted the electrode surface, a bright white display was not obtained, and the black and white contrast was reduced to 6.3.

Example 5 Glass substrate 1 and glass substrate 2 on which ITO electrodes were formed
Was prepared. A solution obtained by mixing acrylamide / acrylic acid / vinyl alcohol at a molar ratio of 659/40/1 and adding ammonium persulfate and carbon powder as an initiator to form a copolymer was placed on an ITO-formed glass substrate 2 for about 3 hours.
μm was applied and crosslinked by heating to form an acrylic acid-acrylamide copolymer gel. Next, a solution obtained by adding ammonium persulfate and titanium oxide powder as an initiator to the above-mentioned acrylamide / acrylic acid / vinyl alcohol mixture and copolymerizing the mixture was applied to the above-mentioned conductive gel at about 3 μm, and crosslinked by heating to form white acrylic acid. -An acrylamide copolymer gel was formed. Subsequently, a glass substrate 1 and a glass substrate 2 sandwich a mylar film disposed as a spacer on the peripheral edge, seal the peripheral edge to produce a cell, and fill the cell with a black aqueous ink containing an electrolyte to form a gel. Was swollen to obtain an evaluation cell as shown in FIG. In this state, the gel is in contact with the electrodes of the display-side substrate 1 and shows white display. When a voltage of 3 V was applied to this evaluation cell, the gel contracted and separated from the display-side substrate 1, where the gel was filled with black ink, and black display was shown from the display substrate side. Next, when the electric field was turned off, the gel returned to the original swelling state, the first white display was confirmed again, and the contrast between light and dark as determined from the reflectance was 8.2. Next, 1.
Although a voltage of 5 V was applied, the same behavior as at 3 V was shown.

Example 6 Glass substrate 1 and glass substrate 2 on which ITO electrodes were formed
Was prepared. A solution obtained by mixing acrylamide / acrylic acid / vinyl alcohol at a molar ratio of 659/40/1, adding ammonium persulfate and carbon powder as an initiator, and copolymerizing the solution was placed on an ITO-formed glass substrate 2 at about 3 μm.
m, and crosslinked by heating to form an acrylic acid-acrylamide copolymer gel. Next, a solution obtained by adding ammonium persulfate as an initiator to the above acrylamide / acrylic acid / vinyl alcohol mixture and copolymerizing the mixture was applied to the above-mentioned conductive gel at about 3 μm, and crosslinked by heating to form an acrylic acid-acrylamide copolymer gel. Was formed. Subsequently, a glass substrate 1 and a glass substrate 2 sandwich a mylar film disposed as a spacer at the peripheral edge, seal the peripheral edge to form a cell, and fill the cell with a yellow aqueous ink containing an electrolyte and fill the cell with a gel. Was swollen to obtain an evaluation cell similar to that of Example 1. In this state, the gel is
, And black display is shown. When a voltage of 3 V was applied to this evaluation cell, the gel contracted and separated from the display-side substrate 1, where it was filled with yellow ink, and yellow display was shown from the display substrate side. Next, when the electric field was cut off, the gel returned to the original swelling state, the first black display was confirmed again, and the light / dark contrast determined from the reflectance was 6.3. Next, a voltage of 1.5 V was applied.
The movement was the same as at 3V.

Comparative Example 4 A cell was prepared in the same manner as in Example 6, except that no carbon powder was added to the gel. In this cell, the gel contracted when a voltage of 3 V was applied, but the gel contracted very slowly at a voltage of 1.5 V.

Example 7 Glass substrate 1 and glass substrate 2 on which ITO electrodes were formed
Was prepared. A solution obtained by mixing acrylamide / acrylic acid / vinyl alcohol at a molar ratio of 659/40/1 and adding ammonium persulfate as an initiator was copolymerized into an IT solution.
About 3 μm was coated on the glass substrate 2 on which O was formed, and crosslinked by heating to form an acrylic acid-acrylamide copolymer gel. Separately, 0.75 mol of aniline and 3
An aqueous solution containing HBF ₄ (tetrafluoroboric acid) is prepared, and the substrate 2 on which the gel is formed is immersed in the aqueous solution and allowed to stand for a sufficient time. Then, aniline electrolysis is performed at a constant current of 3 mA / cm ^2. Polymerization was performed to grow polyaniline in the gel. After taking out and cleaning this substrate 2,
The glass substrate 1 and the glass substrate 2 sandwich a mylar film arranged as a spacer at the peripheral edge, seal the peripheral edge to produce an empty cell, and fill the cell with a yellow aqueous ink containing an electrolyte for evaluation. Cell. In this state, the gel is in contact with the electrode of the display-side substrate 1, and a black (black-green) display is shown. When a voltage of 3 V was applied to this evaluation cell, the gel contracted and separated from the display-side substrate 1, where it was filled with yellow ink, and yellow display was shown from the display substrate side. Next, when the electric field was cut off, the gel returned to the original swelling state, the first black (black-green) display was again confirmed, and the contrast of light and dark obtained from the reflectance was 6.4. Next, a voltage of 1.5 V was applied, but showed the same movement as at 3 V.

Comparative Example 5 A cell was prepared in the same manner as in Example 7, except that polyaniline was not combined with the gel. In this cell, the gel contracted when a voltage of 3 V was applied, but the gel contracted very slowly at a voltage of 1.5 V.

Example 8 Glass substrate 1 and glass substrate 2 on which ITO electrodes were formed
Was prepared. A 0.6% ethanol solution of γ-aminopropyltrimethoxysilane (Nippon Unicar A1110) was applied to the substrate 1 as a silane coupling agent.
The surface was subjected to a coupling treatment by heating at 10 ° C. for 10 minutes to make the surface hydrophobic. The surface of the substrate which has been hydrophobized is described in Example 6.
The contact angle (receding contact angle) with the liquid used in the above was 63 °. An evaluation cell was prepared in the same manner as in Example 6, except that the above-mentioned hydrophobic substrate 1 was used. 3V of this cell
The contrast of light and dark obtained from the reflectance at the time of application is 8.
It was 5.

Example 9 A substrate 1 made of Cytop CTX-805A (manufactured by Asahi Kasei Corporation), which is a thermoplastic resin having a perfluoro structure, was used.
% Solution was obtained from CT-solv. 100 (made by Asahi Kasei Corporation)
And diluted to 0.1% with 150 ° C
The mixture was dried by heating for 2 hours to form a liquid emitting layer. The contact angle (receding contact angle) between the substrate 1 provided with the liquid generating layer and the liquid used in Example 6 was 83 °. An evaluation cell was prepared in the same manner as in Example 8, except that the substrate 1 provided with the liquid-emitting layer was used. The light / dark contrast of this cell obtained from the reflectance at the time of application of 3 V was 9.2.

Example 10 A polythiophene thin film was formed on a glass substrate on which an ITO electrode was formed by an electrolytic polymerization method. Thereafter, an evaluation cell was prepared in the same manner as in Example 2 (the same was applied to the gel). in this case,
When no electric field is applied, the polythiophene exhibits hydrophobicity in the undoped state, and the contact angle (receding contact angle) with the aqueous yellow ink used in this embodiment is 60 °, and the wettability is low. As a result, doping of an anion occurs to change to hydrophilicity, so that the contact angle (receding contact angle) with the yellow aqueous ink becomes 34 °, and the wettability is improved. That is, a cell having a variable wettability display-side electrode that has good wettability with ink during yellow display when voltage is applied, and has low wettability with ink during black display when no voltage is applied. It is. When this cell was evaluated in the same manner as in Example 2, the contrast between light and dark calculated from the reflectance was 8.1.

[0045]

According to the first and second aspects of the present invention, a high-contrast display device can be provided. According to the third aspect, when the gel comes into contact with the display-side substrate, the liquid does not remain on the substrate surface, so that a display element with good gel color display can be provided. According to the fourth aspect, it is possible to provide a display element that can be used by changing only the wettability without changing the substrate material, regardless of the hydrophilicity or hydrophobicity of the liquid. According to the fifth, sixth, and seventh aspects of the present invention, it is possible to provide a display element with further improved contrast. According to the eighth aspect of the invention, it is possible to provide a display element that can be driven easily and has high definition in addition to high contrast. According to the present inventions 9, 10, 11, and 12, it is possible to provide a display device having good responsiveness. According to the thirteenth aspect, it is possible to provide a display element capable of selectively imparting conductivity only to a portion on an electrode with respect to a gel produced on the electrode. Invention 1
According to 4 and 15, a display device with higher contrast can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a reflective display element by electric field control using a gel.

FIG. 2 is a diagram illustrating an example of a display element using a gel having a conductive portion and an insulating portion.

FIG. 3 is an explanatory diagram of a contact angle.

FIG. 4 controls gel deformation by electric field,
FIG. 3 is a diagram illustrating an example of a display element in which wettability can be changed depending on a doped or undoped state of a conductive polymer compound.

FIG. 5 is a diagram illustrating a configuration of a display element of Example 1. (A) The state when no electric field is applied (OFF). (B) The state when the electric field is applied (ON).

FIG. 6 is a diagram illustrating a configuration of a display element according to a fifth embodiment. (A) The state when no electric field is applied (OFF). (B) The state when the electric field is applied (ON).

Claims (15)

[Claims] 1. A light-transmitting display-side substrate, a non-display-side substrate opposed thereto, a liquid contained between the substrates, and a gel that swells / shrinks or bends in response to an external stimulus,
A display element in which display is performed by adjusting incident light due to deformation of a gel, wherein wettability between a liquid and a display-side substrate surface in contact with the liquid is set to be low. 2. The display element according to claim 1, wherein a receding contact angle between the liquid and the display-side substrate surface in contact with the liquid is 50 ° or more. 3. The display device according to claim 1, wherein the display side substrate surface in contact with the liquid is subjected to a liquid generation process. 4. The display element according to claim 1, wherein the wettability between the liquid and the display-side substrate surface in contact with the liquid is set to be variable by an external stimulus. 5. The liquid crystal device according to claim 4, wherein the wettability between the liquid and the display-side substrate surface in contact with the liquid is set so as to change in conjunction with an external stimulus that causes deformation of the gel. Display element. 6. A conductive polymer compound layer is provided on a display-side substrate surface in contact with a liquid, and ions are doped and de-doped by an electric field to control wettability with the liquid and deform the gel. 6. The display element according to claim 5, wherein the liquid crystal panel is set so that wettability with a liquid is reduced when the liquid crystal panel comes into contact with a display-side substrate having a conductive polymer compound layer. 7. The display element according to claim 1, wherein the liquid contained between the substrates is colored. 8. The display device according to claim 1, wherein the external stimulus for deforming the gel is an electric field. 9. The display device according to claim 8, wherein at least a portion of the gel that is in contact with the display-side substrate surface is insulative, and another portion of the gel is conductive. 10. The display device according to claim 9, wherein the length of the conductive portion at the time of gel swelling is at least 1/3 or more of the internal thickness of the device. 11. The thickness of the liquid contained between the two substrates when the insulating portion of the gel contracts is such that the thickness of the liquid permeating through the liquid is reduced.
The display element according to claim 9 or 10, wherein a distance between the gel and the display-side substrate surface is set so that an average transmittance of visible light of 0 nm to 700 nm is equal to or greater than a thickness of 50%. . 12. The display element according to claim 9, wherein the gel contains a conductive polymer compound. 13. The display element according to claim 12, wherein the conductive polymer compound is compounded in a gel by an electrolytic polymerization method. 14. The display element according to claim 9, wherein the display-side substrate surface in contact with the liquid has low wettability with the liquid and also serves as an insulating layer. 15. A conductive polymer compound layer is provided on a display-side substrate surface in contact with a liquid, and ions are doped by an electric field.
By being undoped, the wettability with the liquid is controlled, and when the gel contacts the display-side substrate surface, the conductive polymer compound is set to be undoped and in an insulator state. The display device according to claim 9, wherein: