JP5403506B2 - Display element, optical shutter using the same, and display element device - Google Patents

Description

  The present invention is a display element characterized by being changed to transparent and black by electrochemical oxidation or reduction. The present invention is a display element using an electrochemical oxidation or reduction reaction for transparent display and black display, which could not be achieved conventionally, and an optical shutter for adjusting the amount of transmitted light, display for electronic paper, etc. The present invention relates to a material applicable to an element device.

  The use of materials and elements that can freely adjust the light coming from outside light for buildings and window windows of automobiles, etc. is expected to produce a significant energy saving effect.

  Recent research includes photochromism (a phenomenon in which a single chemical species reversibly isomerizes between two states with different absorption spectra by the action of light), thermochromism ( Thermochromic light-modulating material using a material whose transmittance changes with temperature), gaschromic material whose transmittance changes by controlling atmospheric gas, and electrochromic material that can electrically control light transmittance Etc.

  Among these, research on electrochromic light-modulating materials using tungsten oxide thin films is the most vigorous and has been put into practical use (for example, see Non-Patent Document 1). In addition, as a new technique, a light control material having characteristics that reversibly change a mirror state and a transparent state has been studied (for example, see Patent Document 1).

  Research has also been conducted on display elements intended to increase contrast and black density (for example, see Patent Documents 2 and 3) and safe display elements using an electrolyte that does not contain volatile components (for example, Patent Documents). 4, 5).

Japanese Patent No. 3968432 JP 2002-258327 A JP 2003-31658 A JP 2004-177755 A JP 2006-323022 A

Lee.W.J; Fang.Y.K; Ting.S.F., Electron.Mater. 2000, 29, (2), 183

  Various display elements have been studied in the past, but there are few materials that can reversibly switch between a transparent state and a black state, and no research report has been made.

For example, a light control material using tungsten oxide, which is disclosed in Non-Patent Document 1 and is in practical use as an electrochromic material, has a transparent state and a blue state that change electrically reversibly.
In addition, the display element disclosed in Patent Document 1 has a transparent state and a mirror state that are electrically reversibly changed.

In addition, the display elements disclosed in Patent Documents 2 and 3 are obtained by adding a colorant for increasing whiteness in a polymer solid electrolyte, and a high transparency state cannot be obtained. The display elements disclosed in Patent Documents 4 and 5 are also examined for the contrast between the white state and the black state, but a transparent state cannot be obtained.
An object of the present invention is to provide a new display element having high transmittance in a transparent state and black and high light-shielding property in a black state.

In view of the above-described prior art, the present inventors have conducted extensive research with the goal of developing a new display element having high transmittance in the transparent state and black and high light-shielding property in the black state. As a result, by containing a specific metal ion in the electrolyte layer and forming a specific metal oxide layer on the transparent electrode, it has a high transmittance in the transparent state and a high light-shielding property in the black state. The present invention has been completed by successfully developing a display device having the same.
That is, the present invention is as follows.

(1) a first transparent electrode, a second transparent electrode paired with the first transparent electrode, an electrolyte layer disposed between the first transparent electrode and the second transparent electrode, A display element comprising:
The electrolyte layer is an electrolyte solution or a solid electrolyte containing a metal ion that is discolored by electrochemical reduction or oxidation and accompanying precipitation or dissolution,
The metal ion is selected from the group consisting of silver ion, tungsten ion and bismuth ion,
The first transparent electrode has a nickel oxide layer as an outermost layer, a display element.

(2) The display element according to (1), wherein the electrolyte layer is either an electrolyte solution containing an organic solvent as a main component or a solid electrolyte.
(3) The said electrolyte layer is a display element as described in said (1) or (2) to which the mediator is added.

(4) The display device according to (3), wherein the mediator is a blend of 100 to 750 mmol /.
(5) An optical shutter using the display element according to any one of (1) to (4) above.
(6) A display element device using the display element according to any one of (1) to (4).

  According to the present invention, it is possible to provide a display element, an optical shutter, and a display element device capable of reversibly switching between a transparent state having high transmittance and a black state having high shielding properties. In addition, the present invention can be used as light control glass by combining with glass used for buildings and automobiles, and can be applied to materials such as electronic paper.

The display element sectional drawing which expresses a transparent state and a black state is shown. The display element sectional view of a transparent state is shown. A cross-sectional view of a display element in a black state is shown.

  Hereinafter, embodiments of the present invention will be described in detail.

<Display element>
The display element of the present invention is disposed between the first transparent electrode, the second transparent electrode paired with the first transparent electrode, and the first transparent electrode and the second transparent electrode. A display element having an electrolyte layer,
The electrolyte layer is an electrolyte solution or a solid electrolyte containing a metal ion that is discolored by electrochemical reduction or oxidation and accompanying precipitation or dissolution,
The metal ion is selected from the group consisting of silver ion, tungsten ion and bismuth ion,
The first transparent electrode has a nickel oxide layer as an outermost layer.
Hereinafter, each structure used for the display element will be described.

(First transparent electrode and second transparent electrode)
The transparent electrode used in the present invention is a first transparent electrode having a nickel oxide layer as an outermost layer, and a second transparent electrode which forms a pair with the first transparent electrode.

As long as the first transparent electrode has a nickel oxide layer as the outermost layer, both the first transparent electrode and the second transparent electrode are not particularly limited as long as the transmittance is high. Although the transmittance of the transparent electrode to be used varies depending on the purpose of use, the transmittance is preferably 50% or more, more preferably 70% or more, and particularly preferably 90% or more. When the transmittance is 50% or less, there arises a problem that the transmittance of the obtained display element is lowered. The higher the transparency of the transparent electrode, the better the transmittance in the transparent state.
In the present invention, the transmittance is measured by the following method.

  Using LS1 (manufactured by Ocean Optics) as a light source and HR2000 (manufactured by Ocean Optics) as a light receiving unit and a measuring device, a value of 700 nm is measured to obtain transmittance.

  An example of the transparent electrode is one in which a transparent conductive film is formed on a substrate. In the first transparent electrode, a transparent conductive film is formed on a substrate, and a nickel oxide layer is further provided as an outermost layer.

The substrate for the transparent electrode is preferably transparent, and examples thereof include a transparent glass substrate such as a quartz glass plate and a white plate glass plate. Polyester resins such as polyethylene naphthalate and polyethylene terephthalate; Cellulose ester resins such as cellulose acetate; Fluorine resins such as polyvinylidene fluoride; Polyolefin resins such as polystyrene, polyethylene and polypropylene; Polyimide-amides and polyetherimides Examples thereof include polyimide and the like; and plates and films such as.
Examples of the transparent conductive film of the transparent electrode include films made of a mixture of ITO, zinc oxide (ZnO), IZO (In-Zn-O), and the like.
The formation of the transparent conductive film on the substrate for the transparent electrode can be performed by an ordinary method, and specifically, for example, it is performed by a magnetron sputtering method, a CVD method or the like.

  The first transparent electrode has a nickel oxide layer as the outermost layer. The method for forming the nickel oxide layer is not particularly limited as long as nickel oxide can be formed in layers on the transparent electrode. For example, the nickel oxide layer is formed using a method such as an electrodeposition method or a vacuum deposition method.

  The amount of nickel oxide formed should not be so large that the transmittance is significantly reduced. The transmittance of the first transparent electrode is preferably 50% or more, more preferably 70% or more, and particularly 80% transmittance. % Or more is preferable. When the transmittance of the first transparent electrode after nickel oxide is formed is 50% or less, the transmittance is low, and the display characteristics may be deteriorated. If the transmittance of the first transparent electrode after forming the nickel oxide layer is 80% or more, the transmittance in the transparent state is considered good.

Further, in the present invention, the surface resistance of both the first and second transparent electrodes is preferably low in order to quickly switch between the transparent state and the black state by passing an electric current. When the surface resistance is high, there is a possibility that the problem of slow switching of the display between the transparent state and the black state may occur.
The surface resistance can be adjusted, for example, by adjusting the temperature at the time of sputtering when performing the magnetron sputtering method.

(Electrolyte layer)
The electrolyte layer in the present invention is an electrolyte that is disposed between the first transparent electrode and the second transparent electrode, and contains metal ions that are decolorized by electrochemical reduction or oxidation and precipitation or dissolution associated therewith. It is a solution or a solid electrolyte.

  The metal ions that are decolored by the electrochemical reduction or oxidation and the accompanying precipitation or dissolution are selected from the group consisting of silver ions, tungsten ions, and bismuth ions. By combining these metal ions and a transparent electrode having a nickel oxide layer, a display element excellent in black color development can be obtained.

In order to contain metal ions in the electrolyte layer, specifically, a salt containing the above metal ions (hereinafter also referred to as “metal ion salt”) may be contained in the electrolyte solution medium or the solid electrolyte medium.
Examples of the metal ion salt include halogen compounds such as bismuth chloride.

  The metal ion salt is preferably added to the electrolyte solution or solid electrolyte at a concentration of 1 to 500 mmol / L, more preferably 5 to 450 mmol / L, particularly preferably 10 to 400 mmol / L. When it is 1 mmol / L or less, the required black-state light-shielding property tends to be inferior, and when it is 500 mol / L or more, it may be insoluble in an electrolyte solution medium or a solid electrolyte medium. At a concentration of 10 to 400 mmol / L, both the transparency in the transparent state and the light shielding property in the black state are good.

  The electrolyte solution medium or solid electrolyte medium in the present invention is not particularly limited as long as it can dissolve the metal ion salt. However, the one containing an organic solvent as a main component is also safe from the viewpoint of temperature. This is preferable from the viewpoint of reducing dependency.

In the present invention, “containing an organic solvent as a main component” means that moisture is not contained, or even if it is contained, there is an influence of moisture (for example, generation of bubbles) when the display element is formed. Means no.
Examples of the electrolyte solution medium containing an organic solvent as a main component include polyethylene glycol, ethylene glycol, dimethyl sulfoxide and the like.

  The preferred weight average molecular weight of polyethylene glycol is not particularly limited and is appropriately adjusted depending on the required display switching speed between the transparent state and the black state. In general, as the weight average molecular weight of polyethylene glycol used in the electrolyte solution medium increases, the viscosity increases, and the display switching speed between the transparent state and the black state tends to decrease. Therefore, from the viewpoint of display switching speed, the preferred weight average molecular weight of polyethylene glycol is 150 to 500.

  When dimethyl sulfoxide is used, the viscosity of the electrolyte solution may be adjusted. What is used when preparing an electrolyte solution will not be specifically limited if it can melt | dissolve in a dimethylsulfoxide, For example, polyvinyl butyral etc. can be used as an electrolyte solution preparation agent.

  Available polyethylene glycols include polyethylene glycol 200 (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 180-220), polyethylene glycol 300 (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 300), polyethylene glycol. 400 (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 360 to 440).

  Examples of the solid electrolyte medium include those obtained by dissolving an electrolyte salt in a polyethylene oxide derivative. The solid electrolyte refers to a solid electrolyte that is not in a “solution” state, such as a gel electrolyte or a polymer electrolyte.

  Furthermore, in the electrolyte layer in the present invention, in order to make the transparent state and the black state respond responsively, in particular, in order to speed up the switching from the black state to the transparent state (hereinafter also referred to as “decoloring effect”), Mediators can be added.

  In the present invention, addition of a mediator contributes particularly to improvement in display stability (memory property). As the mediator, a normal one used in the field of electrochemistry can be used and is not particularly limited. For example, when the metal ion is a bismuth ion, the mediator preferably has a higher oxidation potential than the bismuth ion. Specifically, lithium bromide, ferrocene, tetrabutylammonium bromide, or the like can be used. By using these, the decoloring effect can be improved and the memory performance can be improved.

  The addition amount is preferably 1 mmol / L to 1 mol / L, more preferably 10 to 950 mmol / L, and particularly preferably 10 to 900 mmol / L. When the concentration of the mediator is 1 mmol / L or less, the memory effect tends to be difficult to obtain, and when it is 1 mol / L or more, the transmittance tends to decrease due to coloring of the mediator. When the concentration of the mediator is in the range of 10 to 900 mmol / L, it is considered that coloring of the mediator itself is suppressed and the transmittance in the transparent state is not significantly reduced.

In addition, from the viewpoint of reversibly and rapidly responding between the transparent state and the black state, the preferable amount of mediator is 2.5 to 7.5 mol of mediator with respect to 1 mol of metal ion, specifically, 100 to 750 mmol of mediator. / L is preferable.
The thickness of the electrolyte layer in the present invention is preferably 10 to 200 μm in order to increase the response speed and improve the memory property.

(Manufacture of display elements)
The display element of the present invention can be manufactured as follows.
First, the first transparent electrode and the second transparent electrode are prepared. Examples of the method for disposing the electrolyte layer between the first transparent electrode and the second transparent electrode include the following methods.

  When an electrolyte solution is used for the electrolyte layer, there are methods of utilizing the current state of capillaries, injecting between electrodes in a vacuum, or dropping an electrolyte solution using an ink jet or a dispenser. In the case where a solid electrolyte is used for the electrolyte layer, a method of forming a solid electrolyte film and bonding it can be mentioned.

<Use of display element>
One embodiment of the display element of the present invention is shown in FIG.
The display element 10 of the present invention includes a first transparent electrode 1 having a substrate 1a, a transparent conductive film 1b, and a nickel oxide layer 1c,
A second transparent electrode 2 having a substrate 2a and a transparent conductive film 2b;
An electrolyte layer 3 disposed between the first transparent electrode 1 and the second transparent electrode 2;
A spacer 4 is provided for controlling the thickness of the electrolyte layer and for sealing the electrolyte solution.

  Further, the second transparent electrode is connected to the driving element by a wiring (not shown), and is electrochemically controlled by the driving element.

The spacer is not particularly limited as long as it does not dissolve in the organic solvent used for the electrolyte solution or current flows, but for example, sealing materials used in liquid crystal displays (epoxy type, acrylic type, urethane type, etc.) In addition, examples of the curing method of the sealing material include a photo-curing type and a thermosetting type.
As the drive element, for example, a drive element used in a liquid crystal display can be used. Specifically, a passive drive element, an active drive element, or the like can be used.

  When the display element of the present invention is in the transparent state, as shown in FIG. 2, the bismuth ions 5a contained in the electrolyte layer 3 are present in the electrolyte solution or in the solid electrolyte in a transparent state. The nickel oxide layer 1c of the transparent electrode (counter electrode) is in a transparent state. Therefore, the transmittance of the display element is high, and the display element is in a transparent state (display element 10A in FIG. 2).

  On the other hand, in the black state, as shown in FIG. 3, the bismuth ions present in the electrolyte layer 3 are reduced on the second transparent electrode (working electrode) side and precipitated to become bismuth precipitates 5b. In addition to color development, the nickel oxide layer 1d also develops black color on the first transparent electrode (counter electrode) side (display element 10B in FIG. 3). Therefore, the display element is in a black state with excellent shielding properties.

  The display element of the present invention is a display element capable of reversibly switching between a transparent state having a high transmittance and a black state having a high shielding property. It can be used for an optical shutter such as a shutter mounted on a display element device such as an electronic paper or a flexible display.

  The present invention can be used as light control glass by combining with glass used for buildings, automobiles, etc., and can be applied to materials such as electronic paper. It is useful for providing new products.

  In order to describe the present invention more specifically, examples and comparative examples are shown below, but the present invention is not limited to the following examples.

<Production of first transparent electrode: formation method of nickel oxide layer>
A method for forming a nickel oxide layer on an ITO electrode having a surface resistance of 10Ω, in which an ITO transparent conductive film is formed on a non-alkali glass substrate (size 25 × 25 mm) by magnetron sputtering, is described below.

  Nickel nitrate (II) hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) is dissolved in water at a concentration of 200 mmol / L to form a nickel nitrate aqueous solution, and the ITO electrode is immersed in the nickel nitrate aqueous solution to form a first transparent electrode The working electrode for the production of The counter electrode for producing the first transparent electrode was a platinum rod (manufactured by Nilaco Corporation), and a silver-silver chloride electrode was used as the reference electrode. Each was pinched by an alligator clip and the cord was extended.

  The extended cord is connected to Electrochemical Analyzer 440A (manufactured by ALS / CH Instruments), 0.9 V (2 mA), 300 seconds (hereinafter “NiO-300”), 600 seconds (hereinafter “NiO-600”), 900 Second (hereinafter referred to as “NiO-900”) was applied under different conditions. Thereafter, it was placed in an electric furnace set at 300 ° C. and baked for 20 minutes to obtain ITO electrodes having nickel oxide layers with different amounts of nickel oxide (hereinafter referred to as ITO electrodes 1 to 3 with nickel oxide layers). All the transmittances were about 90% or more (Table 1 shows the results as transmittance in a transparent state).

<Method for Manufacturing Display Characteristic Evaluation Cell>
As shown in FIG. 1, the second transparent electrode (working electrode) 2 is an ITO electrode (an electrode having a surface resistance of 10Ω formed by forming an ITO transparent conductive film on a non-alkali glass substrate (size 25 × 25 mm) by magnetron sputtering). The first transparent electrode (counter electrode) 1 uses any one of the ITO electrodes 1 to 3 with a nickel oxide layer, the spacer 4 uses a PET double-sided adhesive tape having a thickness of about 70 μm, and the two electrodes are The display element 10 was produced by bonding.

(Example 1) Evaluation of transmittance in transparent state and black state An electrolyte solution was prepared by the following method. Polyethylene glycol (weight average molecular weight: 180 to 220) with a concentration of bismuth chloride (manufactured by Wako Pure Chemical Industries, Ltd.) at 100 mmol / L and lithium bromide (manufactured by Wako Pure Chemical Industries, Ltd.) at 500 mmol / L. : Polyethylene glycol 200, manufactured by Wako Pure Chemical Industries, Ltd.) and stirred for a whole day and night to obtain an electrolyte solution (A).

  The electrolyte solution (A) was sucked with a dropper, and then dropped onto one of the ITO electrodes 1 to 3 with the nickel oxide layer obtained above. Furthermore, the second transparent electrode was put on and bonded to form the display element of FIG. 1, and the transmittance of each display element was measured by the following method.

<Transmittance measurement>
LS1 (manufactured by Ocean Optics) was used as the light source, and HR2000 (manufactured by Ocean Optics) was used as the light receiving unit and the measuring device, and transmittance measurements in a transparent state and a black state were performed. The results are shown in Table 1.

<Evaluation of memory>
For evaluation of memory property, the power was turned off from the black state, and the transmittance after 120 seconds, 300 seconds and 600 seconds from that point was measured. The results are shown in Table 2.

<Voltage operation in transparent state and black state>
As a switching operation method between the transparent state and the black state, −2.5 V was applied to the working electrode to obtain a black state. Thereafter, +0.5 V was applied to the counter electrode to make it transparent.

(Comparative example 1) Evaluation of transmittance in transparent state and black state Evaluation was performed in the same manner as in Example 1 using an ITO electrode having no nickel oxide layer as the first transparent electrode and using the electrolyte solution used in Example 1 as the electrolyte layer. did. The results are shown in Table 1.

(Example 2) Evaluation of memory properties Bismuth chloride (manufactured by Wako Pure Chemical Industries, Ltd.) was added to polyethylene glycol 200 at a concentration of 100 mmol / L and stirred for a whole day and night to obtain an electrolyte solution (B).

  This was used for the electrolyte layer of the display element of FIG. 1, and the ITO electrode with nickel oxide layer 1 obtained above was used to measure the transmittance and evaluate the memory property. The results are shown in Table 2.

  According to the present invention, it is possible to provide a display element, an optical shutter, and a display element device capable of reversibly realizing a transparent state having a high transmittance and a black state having a high light shielding property. In addition, the present invention can be used as light control glass by combining with glass used for buildings, automobiles, etc., and can be applied to materials such as electronic paper. -Useful as a new product offering.

1 First transparent electrode (counter electrode)
1a Substrate 1b Transparent conductive film 1c Nickel oxide layer (transparent state)
1d Nickel oxide layer (black state)
2 Second transparent electrode (working electrode)
2a Substrate 2b Transparent conductive film 3 Electrolyte layer 4 Spacer 5a Bismuth ion 5b Bismuth precipitate 10 Display element

Claims (4)

A display comprising: a first transparent electrode; a second transparent electrode paired with the first transparent electrode; and an electrolyte layer disposed between the first transparent electrode and the second transparent electrode. A device,
The electrolyte layer is an electrolyte solution or a solid electrolyte containing bismuth ions that are discolored by electrochemical reduction or oxidation and accompanying precipitation or dissolution, and a mediator is in the range of 100 to 750 mmol / L. Is blended,
Said first transparent electrode has a nickel oxide layer in the outermost layer, the transmittance of the said nickel oxide layer in the transparent state is formed first transparent electrode is equal to or greater than 50%, transparency A display element capable of reversibly switching between a state and a black state .   The display element according to claim 1, wherein the electrolyte layer is either an electrolyte solution containing an organic solvent as a main component or a polymer solid electrolyte. An optical shutter using the display element according to claim 1 . A display element device using the display element according to claim 1 .

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