JP2016126184A - Electrolyte and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a well-decolorable and well-light transmissive electrolyte having high light transmissivity, and an optical device using this electrolyte with which it is possible to vary light transmissivity by repeating metal deposition and remelting.SOLUTION: The electrolyte includes a metal compound in which at least a reversible oxidation-reduction reaction occurs, a decoloring agent for promoting the remelting of metal deposited from the metal compound and decoloring a metallic color, and a support electrolyte that are dissolved in a solvent. The decoloring agent contains 2 mmol/L or more of Brin terms of mol concentration. It is preferable that the decoloring agent contains 1 mmol/L or more of Cu, in addition to Br. Furthermore, it is desirable that the decoloring agent satisfy X+3X≤23, where Xmmol/L represents the mol concentration of Br, and Xmmol/L represents the mol concentration of Cu. The electrolyte layer 3 of the optical device includes this electrolyte 8.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrolytic solution and an optical device, and more particularly to an electrolytic solution containing an electrochromic material whose light transmittance is changed by deposition and re-dissolution of the metal, and using this electrolytic solution to deposit and regenerate the metal. The present invention relates to an optical apparatus in which light transmittance is variable by repeating dissolution.

  2. Description of the Related Art In recent years, research and development have been actively conducted on optical devices that use an electrochromic material in which an oxidation-reduction reaction is caused by application of a direct current voltage, and in which light transmittance is variable by repeating metal deposition and remelting.

  In this type of optical device, a metal compound that causes a reversible redox reaction, a decolorizer that erases the metal color by promoting re-dissolution of the metal deposited from the metal compound, and a supporting electrolyte are dissolved in a solvent. An electrolyte layer is prepared, and an electrolyte layer enclosing the electrolyte is interposed between a pair of electrodes.

  In the optical device configured as described above, when a predetermined voltage is applied between the electrodes, metal is deposited on the surface of one of the electrodes, the light transmittance is lowered, and an opaque reflection state is obtained. In addition, when a reverse polarity voltage (hereinafter referred to as “reverse voltage”) in which the polarity of the voltage is reversed is applied between the electrodes, the metal is re-dissolved and the light transmittance is increased. It becomes a transmission state.

  For example, Patent Document 1 includes a pair of substrates, a pair of electrodes formed on opposing surfaces of the pair of substrates, and an electrochromic material and a mediator containing silver that are sandwiched between the pair of electrodes. A display device having an electrolyte layer has been proposed.

In Patent Document 1, an electrochromic material such as an Ag salt, a mediator having a decoloring function such as a Cu salt containing a divalent Cu ion (Cu ²⁺ ), and a supporting electrolyte such as a Br salt are represented by dimethyl sulfoxide (hereinafter referred to as a dimethyl sulfoxide). , "DMSO") and the like, and an electrolyte solution is prepared by forming the electrolyte layer with this electrolyte solution. By applying a voltage of -2.5 V, a reflection state, that is, a mirror state is realized. A transmission state is to be realized by applying a voltage of .5V.

  In Patent Document 2, a silver halide solution is disposed between a working electrode and a counter electrode, and is configured to cause precipitation or dissolution of Ag by driving control of these electrodes. The supporting salt capable of supplying the same or different halogen as the silver halide for dissolution was selected from the group consisting of LiX, NaX and KX (where X is F, Cl, Br or I). An optical device in which at least one salt is added and the silver halide is complexed has been proposed.

In Patent Document 2, Ag is precipitated and dissolved by an oxidation-reduction reaction of silver halide. Then, a Cu salt containing Cu ^{2+ in the} electrolytic solution and a clarifying agent such as triethanolamine are added to reduce the presence state of Cu in the solvent from Cu ²⁺ to Cu ^+. The overvoltage of the film is reduced and the light absorption of the electrolyte in the visible light region is avoided.

JP 2012-181389 A (Claim 1, paragraph [0 [0032] etc.) JP-A-10-148851 (Claim 1, paragraphs [0020] to [0025], etc.)

In Patent Document 1, the inclusion of Cu ²⁺ in the electrolytic solution promotes re-dissolution of the metal and decolors the metal color, but instantaneously shifts from the opaque state where the metal is deposited to the transmission state. For this purpose, a large amount of Cu ²⁺ needs to be contained in the electrolytic solution. On the other hand, if Cu ²⁺ is contained in a large amount, a sufficient transparency state cannot be ensured due to the coloring action of Cu ²⁺ itself on the electrolytic solution, which may cause a decrease in permeability.

That is, when a Cu salt containing Cu ²⁺ is contained together with an Ag compound, the Ag compound is reduced by applying a predetermined voltage to precipitate Ag. Thereafter, by applying a reverse voltage, an oxidation-reduction reaction shown in the chemical reaction formula (1 ′) occurs, Ag is redissolved and oxidized to Ag ⁺ , and Cu ²⁺ is reduced to Cu ⁺ .

Ag + Cu ²⁺ → Ag ⁺ + Cu ⁺ (1 ′)
In this case, Cu ²⁺ promotes re-dissolution of Ag and has a decoloring function for Ag, so that the color of precipitated Ag can be erased.

However, when the content of Cu ²⁺ in the electrolytic solution is small, it is not possible to instantaneously shift from an opaque state with low transmittance to a state with high transmittance, and sufficient decoloring property can be obtained. Can not. For this reason, in order to obtain a desired decoloring property, it is necessary to contain a large amount of Cu ^{2+ in the} electrolytic solution.

On the other hand, Cu ²⁺ has an electron configuration in which electrons are incompletely filled in d orbitals. Therefore, when irradiated with light, a plurality of d orbitals degenerated with the same energy have low energy. It splits into an orbit and a higher orbit, and absorbs light of a wavelength corresponding to this split energy difference. Accordingly, since the more even amount of light absorbed in the visible light region when Cu ²⁺ is increased, so that the Cu ²⁺ is colored strongly electrolytic solution. For this reason, even if the color of Ag can be erased, a sufficient transparent state cannot be obtained, and the transparency may be lowered.

As described above, in Patent Document 1, if the content of Cu ^{2+ in} the electrolytic solution is small, sufficient decoloring property cannot be obtained. On the other hand, if the content of Cu ²⁺ is large, the permeability is lowered. For this reason, it is difficult to achieve both decolorization and transparency.

Further, Patent Document 2 adds Cu salt to a solution together with a clarifying agent in order to reduce dissolution overvoltage of the deposited Ag film, thereby reducing Cu ²⁺ to Cu ⁺ and avoiding coloring of the solution. .

That is, in Patent Document 2, even if the electrolyte solution can be made transparent by reducing Cu ²⁺ to Cu ⁺ , Cu ²⁺ and Ag coexist in the electrolyte solution to cause a redox reaction. It is not a thing and the decoloring property by Cu ^<2+ > cannot be obtained.

  Therefore, as with Patent Document 2, it is difficult to obtain an electrolytic solution that achieves both transparency and decoloring properties.

  The present invention has been made in view of such circumstances, and has an excellent erasability and a highly light-transmitting electrolytic solution having a high light transmittance, and using this electrolytic solution, An object of the present invention is to provide an optical device having a variable light transmittance by repeating dissolution.

The inventors of the present invention have made extensive studies to achieve the above object. As a result, the tribromide ion (Br ₃ ⁻ ) can suppress the coloring of the electrolytic solution, thereby improving the permeability. In addition, the decoloring property is equal to or higher than that of divalent Cu ions (Cu ²⁺ ), thereby obtaining the knowledge that both transparency and decoloring property are possible. In order to achieve both transparency and decolorization, the knowledge that the content of tribromide ions (Br ₃ ⁻ ) in the electrolytic solution is 2 mmol / L or more in terms of molar concentration is sufficient. I got it.

The present invention has been made based on such knowledge, the electrolyte solution according to the present invention is an electrolyte solution in which at least a metal compound, a color erasing agent, and a supporting electrolyte are dissolved in a solvent, The color erasing agent is characterized by containing at least 2 mmol / L or more of Br ₃ ⁻ .

  As a result, it is possible to obtain an electrolyte solution with good erasability and high light transmittance and good transparency, and both erasability and transparency can be achieved.

In the electrolytic solution of the present invention, the content of Br ₃ ⁻ is preferably 100 mmol / L or less.

  As a result, the electrolyte solution can be obtained without being unstable, and an electrolyte solution capable of achieving both permeability and decoloring properties can be obtained.

Further, as a result of further diligent research by the present inventors, by adding a predetermined amount of divalent Cu ions (Cu ²⁺ ) in addition to the above-mentioned Br ₃ ⁻ , the transparency and decoloring properties are not impaired. It has been found that the metal deposition voltage can be reduced.

That is, in the electrolytic solution of the present invention, the decolorizer preferably contains 1 mmol / L or more of Cu ²⁺ in addition to the Br ₃ ⁻ .

  As a result, metal can be deposited by applying a low voltage, so it is possible to reduce the voltage load applied to the electrolyte, and in addition to permeability and decolorization, it is possible to extend the life of the electrolyte. Become.

In the electrolytic solution of the present invention, the Cu ²⁺ is preferably contained in the form of copper halide.

Further, in the electrolytic solution of the present invention, when the decolorizer represents the molar concentration of Br ₃ ⁻ by X _TBr mmol / L and the molar concentration of Cu ²⁺ by X _Cu mmol / L, It is preferable that X _TBr + 3X _Cu ≦ 23 is satisfied.

Thus the molar concentration of Cu ²⁺ Br ₃ ^- to about 1/3 of the molar concentration of, and Cu ²⁺ and Br ₃ ^- by defining the total molar concentration of as described above, decolorizable course That is, good permeability can be maintained while lowering the metal deposition voltage.

In the electrolytic solution of the present invention, the Br ₃ ⁻ is preferably contained in the form of alkylammonium tribromide.

  In the electrolytic solution of the present invention, the metal compound preferably contains an Ag compound.

  Thereby, it is possible to obtain a high-quality electrolytic solution that repeats the deposition mode in which Ag with good reflectivity is deposited and the dissolution mode in which Ag is re-dissolved.

  In the electrolytic solution of the present invention, the metal compound is preferably contained in a range of 5 to 1000 mmol / L.

  Thereby, the optical state between the opaque state and the transparent state can be repeatedly changed without impairing the stability of the electrolytic solution.

In the electrolytic solution of the present invention, the supporting electrolyte preferably contains bromide ions (Br ⁻ ).

  Furthermore, in the electrolytic solution of the present invention, the supporting electrolyte is preferably 0.5 to 50 times the metal compound in terms of molar concentration.

  Thereby, a metal complex can be formed without impairing the stability of the electrolytic solution.

  An optical device according to the present invention is an optical device in which an electrolyte layer is interposed between a pair of transparent electrodes, and the electrolyte layer includes any one of the above-described electrolytic solutions. .

According to the electrolytic solution of the present invention, at least a metal compound, a color erasing agent, and a supporting electrolyte are dissolved in a solvent, and the color erasing agent contains at least 2 mmol / L or more of Br ₃ ⁻ . Therefore, Br ₃ ⁻ can suppress the coloring of the electrolyte solution and has a decoloring property equal to or higher than that of Cu ²⁺ , so that the decoloring property is good and the light transmittance is high. An electrolysis solution can be obtained, and both decolorization and permeability can be achieved.

  In addition, according to the optical device of the present invention, the electrolyte device includes an electrolyte layer interposed between a pair of transparent electrodes, and the electrolyte layer includes any one of the above-described electrolyte solutions, and thus has a predetermined voltage. Is applied to the surface of one of the transparent electrodes to cause an opaque state, and the deposited metal is re-dissolved by applying a reverse voltage. By repeating the deposition and re-dissolution of the metal, it is possible to obtain a high-quality optical device having a variable light transmittance having good decoloring properties and high light transmittance.

It is sectional drawing which shows one Embodiment of the optical apparatus using the electrolyte solution which concerns on this invention. It is a perspective view for demonstrating the production method of the empty cell in an Example. It is a figure which shows the relationship between the wavelength and light transmittance of Example 1 in [Example 1] and Comparative Example 1. It is a figure which shows the relationship between the decolorizer ion and light transmittance of each sample in [Example 1].

  Next, an embodiment of the present invention will be described in detail.

  In the electrolytic solution as one embodiment of the present invention, at least a metal compound, a color erasing agent, and a supporting electrolyte are dissolved in a solvent.

The decolorizer contains at least 2 mmol / L or more of tribromide ions (Br ₃ ⁻ ), which has good decoloring properties and high light transmittance, and has excellent decoloring properties and transparency. A compatible electrolyte solution can be obtained.

  In an optical device that repeats deposition and remelting of metal, it is necessary to smoothly remelt the deposited metal by applying a predetermined voltage and to decolorize the metal color by applying a reverse voltage. An agent is contained.

  That is, the decolorizer can spontaneously generate an oxidation reaction in which the deposited metal is ionized, and reversibly performs an oxidation reaction from the deposited metal to the metal ion and a reduction reaction from the metal ion to the deposited metal. Function is required.

As a color erasing agent having such a function, conventionally, Cu salts such as CuCl ₂ containing Cu ²⁺ have been widely used as described in Patent Document 1.

However, as described in [Problems to be Solved by the Invention], when a Cu salt containing Cu ²⁺ is used as a decoloring agent, the metal color can be erased, but Cu ²⁺ Since it strongly colors the electrolytic solution, the transparency of the electrolytic solution is lowered and the light transmittance is lowered.

Therefore, as a result of intensive studies by the present inventors, Br ₃ ⁻ can effectively suppress the coloring of the electrolytic solution and has a good decoloring property equal to or better than Cu ^2+. I found.

Therefore, in the present embodiment, Br ₃ ⁻ is used instead of Cu ²⁺ , thereby achieving both transparency and decolorization.

That is, Br ₃ ⁻ has a good color erasability equal to or higher than that of Cu ²⁺ as described above.

For example, when an Ag compound is used as the metal compound, the oxidation reaction of Ag proceeds according to the chemical reaction formula (1), and the reduction reaction of Br ₃ ⁻ proceeds according to the chemical reaction formula (2).

Ag → Ag ⁺ + e ⁻ (1)
Br ₃ ⁻ + 2e ⁻ → 3Br ⁻ (2)
That is, since the chemical reaction formula (1) has a lower redox potential than the chemical reaction formula (2), the chemical reaction formula (1) occurs spontaneously.

  Here, the oxidation-reduction potentials of the chemical reaction formula (1) and the chemical reaction formula (2) can be confirmed by cyclic voltammetry.

For example, an Ag electrode as a reference electrode (Ag / Ag ⁺ reference electrode) is immersed in a solution of silver nitrate 100 mmol / L and tetrabutylammonium perchlorate 100 mmol / L dissolved in DMSO to prepare a reference electrode tank. For example, the working electrode and the counter electrode are immersed in an electrolytic cell in which silver nitrate 50 mmol / L and tetrabutylammonium bromide 250 mmol / L are dissolved in DMSO. The oxidation-reduction potential of the chemical reaction formula (1) can be obtained by well-known cyclic voltammetry.

  Similarly, the working electrode and the auxiliary electrode are immersed in an electrolytic cell in which tetrabutylammonium tribromide 5 mmol / L and tetrabutylammonium perchlorate 100 mmol / L are dissolved in DMSO. And an oxidation-reduction potential of the chemical reaction formula (2) can be obtained by the cyclic voltammetry.

As a result, it can be confirmed that the redox potential of the chemical reaction formula (1) is electrochemically lower than the redox potential of the chemical reaction formula (2). That is, since the oxidation-reduction potential of the chemical reaction formula (1) is electrochemically lower than the oxidation-reduction potential of the chemical reaction formula (2), the Ag compound and the tribromide salt coexist in the electrolytic solution. In this case, the chemical reaction formula (1) spontaneously occurs, and the precipitated Ag is oxidized and redissolved to produce Ag ⁺ , while Br ₃ ⁻ causes a reduction reaction to produce Br ⁻ . Moreover, the chemical reaction formula (2) proceeds reversibly as apparent from the state of change of the valence, and Br ⁻ is oxidized and returned to Br ₃ ⁻ during the reduction reaction in which Ag precipitates. Has color.

Moreover, unlike Cu ²⁺ as described above, Br ₃ ⁻ can effectively suppress the coloring of the electrolytic solution, and can thereby increase the light transmittance compared to Cu ²⁺ . It becomes possible to achieve both transparency and decolorization.

In order to achieve both transparency and decoloring properties in this way, the content of Br ₃ ⁻ in the electrolytic solution needs to be at least 2 mmol / L or more in terms of molar concentration.

Meanwhile, Br ₃ ^- content limit is not particularly limited, considering the stability of the solution is preferably not more than 100 mmol / L on a molar basis.

The content of Br ₃ ^{− in} the electrolytic solution is not particularly limited. For example, tetrabutylammonium tribromide represented by chemical formula (1) or tetrabutylammonium tribromide represented by chemical formula (2) is used. Tetraalkylammonium tribromide such as can be used.

In addition to the Br ₃ ⁻ described above, the electrolytic solution preferably contains a certain amount of Cu ²⁺ as a decoloring agent.

That is, Cu ²⁺ has a function of strongly coloring the electrolyte as described above, but contributes to a decrease in the deposition voltage.

Accordingly, by adding a certain amount of Cu ²⁺ in addition to Br ₃ ⁻ , the deposition voltage can be lowered while maintaining the desired permeability and decoloring property, and this is applied to the electrolyte. The voltage load can be reduced, and the life of the electrolyte can be extended.

Thus, in order to reduce the deposition voltage, Cu ²⁺ is required to be at least 1 mmol / L in the electrolyte.

However, when the Cu ²⁺ content is excessive, the effect of adding Br ₃ ⁻ is impaired and the permeability is lowered. Therefore, the Cu ²⁺ content is determined by _setting the molar concentration of Br ₃ ⁻ to X _TBr , When the molar concentration of Cu ²⁺ is X _Cu , it is preferable to satisfy the formula (3).

X _TBr + 3X _Cu ≦ 23 (3)

That is, the molar concentration of divalent Cu ions (Cu ²⁺ ) is set to about 1/3 of the molar concentration of tribromide ions (Br ₃ ⁻ ), and the total molar concentration of Cu ²⁺ and Br ₃ ⁻ is 23 mmol / L. By making it below, not only decolorization but also good permeability can be maintained while lowering the metal deposition voltage.

The content of Cu ^{2+ in} the electrolytic solution is not particularly limited, and for example, copper halides such as copper chloride, copper bromide, and copper iodide, copper nitrate, and the like can be used.

Thus, in this electrolytic solution, in addition to 2 mmol / L or more of Br ₃ ⁻ , a certain amount of Cu ²⁺ is contained in the electrolytic solution, so that both permeability and decoloring can be achieved. Can lower the deposition voltage, and can provide a high-quality and long-life electrolyte.

The metal compound is not particularly limited as long as it is an electrochromic material that spontaneously generates a reversible oxidation-reduction reaction and deposits and re-dissolves the metal. In addition to the above Ag compound, the Bi compound In general, an Ag compound containing Ag having good reflectivity is preferably used. Therefore, as the metal compound, Ag salts such as AgNO ₃ , AgBr, AgI, AgCl, AgCH ₃ COO, and Ag complex salts can be used alone or in combination.

  Further, the molar concentration of the metal compound in the electrolytic solution is not particularly limited as long as the desired metal deposition occurs by the oxidation-reduction reaction, but the optical state can be sufficiently changed without impairing the stability of the electrolytic solution. In order to make it, 5-1000 mmol / L is preferable.

Further, the supporting electrolyte is not particularly limited as long as it is a material that acts as a complexing agent of metal ions and is not destroyed electrochemically, but usually sodium bromide containing bromide ions (Br ⁻ ). Br salts such as potassium bromide, lithium bromide, tetrabutylammonium bromide and tetraethylammonium bromide can be particularly preferably used.

  Further, the molar concentration of the supporting electrolyte is not particularly limited, but it is preferably selected appropriately in a wide range of about 0.5 to 50 times the metal compound, for example, about 2.5 to 50000 mmol / L.

  The solvent is not particularly limited as long as the metal compound, the color erasing agent and the supporting electrolyte described above can be completely dissolved and the metal can be precipitated, and a polar solvent such as water. Or a nonpolar organic solvent such as DMSO may be used.

  Next, the manufacturing method of the said electrolyte solution is explained in full detail.

First, a supporting electrolyte such as a metal compound such as an Ag salt, a tribromide salt containing Br ₃ ⁻ , a Cu salt containing Cu ²⁺ , and a Br salt as required is prepared, and a predetermined amount is weighed. Then, these weighed materials are put in a solvent such as DMSO, and sufficiently stirred in an inert gas atmosphere such as an Ar atmosphere or an N ₂ atmosphere to dissolve these solutes in the solvent, thereby producing an electrolyte. .

Thus, this electrolytic solution comprises at least a metal compound that causes a reversible oxidation-reduction reaction, a decolorizing agent that promotes re-dissolution of the metal deposited from the metal compound and decolorizes the metal color, and a supporting electrolyte. In the electrolytic solution dissolved in the solvent, the decolorizer contains at least 2 mmol / L or more of tribromide ions (Br ₃ ⁻ ) in terms of molar concentration, so Br ₃ ⁻ Since it can suppress coloring to the liquid and has a decoloring property equal to or higher than that of Cu ²⁺ , it is possible to obtain an electrolytic solution having a good decoloring property and a high light transmittance. Can be achieved.

In addition to Br ₃ ⁻ , the decolorizer contains Cu ²⁺ of 1 mmol / L or more in terms of molar concentration within the range defined by the formula (3), so that precipitation is maintained while maintaining permeability. Since the voltage can be lowered, the voltage load applied to the electrolytic solution is reduced, and it is possible to extend the life of the electrolytic solution in addition to achieving both permeability and decoloring properties.

  Next, an optical device using the electrolytic solution will be described in detail.

  FIG. 1 is a cross-sectional view schematically showing one embodiment of an optical device manufactured using the above electrolytic solution.

  In this optical device, a first transparent electrode 2 is formed on the surface of a first transparent substrate 1 such as a glass substrate, and an electrolyte layer 3 is formed on the surface of the first transparent electrode 2. A second transparent electrode 4 is formed on the surface of the electrolyte layer 3, and a second transparent electrode made of the same glass substrate as the first transparent substrate 1 is formed on the surface of the second transparent electrode 4. A substrate 5 is formed.

Here, the 1st and 2nd transparent electrodes 2 and 4 are formed with the transparent conductive film. The transparent conductive film is not particularly limited as long as it has good transparency and conductivity. For example, ITO (tin-doped indium oxide), ZnO, TNO (niobium-doped titanium oxide), GZO (gallium-doped oxide) Zinc), an In ₂ O ₃ —ZnO-based material, or the like can be used.

  The electrolyte layer 3 includes a spacer 6 that secures an interval between the first transparent electrode 2 and the second transparent electrode 4, a protective wall 7 formed on the inner peripheral surface of the spacer 6, And an electrolytic solution 8 sealed in the container. That is, the electrolytic solution 8 is interposed between the first transparent electrode 2 and the second transparent electrode 4 in a form surrounded by the first transparent electrode 2, the protective wall 7, and the second transparent electrode 4. ing.

  Here, the protective wall 7 is not particularly limited as long as it has solvent resistance. However, it is usually preferable to use an ultraviolet curable resin that can be liquid-cured.

  Also, the spacer 6 is not particularly limited as long as it has solvent resistance. For example, a fluorine resin can be used.

  This optical device can be easily manufactured as follows.

  That is, first and second transparent substrates 1 and 5 formed of a glass substrate or the like are prepared, and one of each of the first and second transparent substrates 1 and 5 is used by using a thin film forming method such as a sputtering method. First and second transparent electrodes 2 and 4 made of ITO or the like having a film thickness of 0.1 to 0.5 μm are formed on the main surface.

  Next, a UV curable resin capable of liquid contact curing is applied linearly to the outer periphery of the surface of the first transparent electrode 2 to form a coating film. At this time, an opening is provided in a part of the coating film so that the electrolytic solution can be injected.

  Next, a spacer 6 made of fluororesin or the like with a film thickness of 100 to 2000 μm is arranged on the outer peripheral portion of the coating film, and the second transparent electrode 2 on which the second transparent electrode 4 is formed is placed on the coating film and the spacer 6. Placed on. Thereafter, this is irradiated with ultraviolet rays, and the first transparent substrate 1, the first transparent electrode 2, the coating cured film having the opening, the spacer 6, the second transparent electrode 4, and the second transparent substrate 5 are formed. Empty cells stacked in sequence are produced.

  In addition, since the spacer 6 is provided in order to ensure the distance between the 1st transparent electrode 2 and the 2nd transparent electrode 4, you may remove after preparation of an empty cell.

  Next, the above-described electrolytic solution is injected from the opening of the coating cured film, and thereafter, the opening is sealed with an ultraviolet curable resin that can be liquid-cured to form the protective wall 7. Thereby, the electrolytic solution 8 is surrounded by the protective wall 7 and the first and second transparent electrodes 2, 4, and an optical device is manufactured.

  The optical device thus formed is an optical device in which the electrolyte layer 3 is interposed between the first and second transparent electrodes 2 and 4, and the electrolyte layer 3 contains the electrolytic solution. By applying a predetermined voltage, a metal is deposited on the surface of the first transparent electrode 2 to become an opaque state, and the deposited metal is redissolved by applying a reverse voltage. By repeating the deposition and re-dissolution of the metal, it is possible to obtain a high-quality optical device having a variable light transmittance having good decoloring properties and high light transmittance.

  The present invention is not limited to the above embodiment. In the above embodiment, the metal compound, the color erasing agent and the supporting electrolyte are dissolved in a solvent to prepare an electrolytic solution. However, if it is not electrochemically destroyed, an additive may be appropriately added to the solvent. For example, an appropriate amount of a gelling agent such as PVB may be added for the purpose of suppressing precipitation unevenness.

  Next, examples of the present invention will be specifically described.

[Sample preparation]
Example 1
Silver nitrate was prepared as a metal compound, tetrabutylammonium tribromide as a tribromide salt, and tetrabutylammonium bromide as a supporting electrolyte. And it measured so that the molar concentration in electrolyte solution might be silver nitrate: 50 mmol / L, tetrabutylammonium tribromide: 10 mmol / L, and tetrabutylammonium bromide: 250 mmol / L, and these weighed materials were used as solvents. Was put into a pot mill together with DMSO and stirred for 12 hours in a glove box adjusted to 40 ° C. under an inert atmosphere such as Ar gas or N ₂ gas, thereby preparing an electrolyte.

  Next, as shown in FIG. 2, glass substrates 51a and 51b having a length of 50 mm and a width of 50 mm were prepared. Next, using a sputtering method, ITO films 52a and 52b (transparent electrodes) having a film thickness of 0.2 μm were formed on one main surface of the glass substrates 51a and 51b. An ITO film having a specific resistance of 10 Ω · cm was used.

  Next, the glass substrates 51a and 51b are arranged so that the ITO films 52a and 52b face each other, and then a U-shaped spacer 53 made of a fluororesin and having a thickness of 300 μm is arranged between the glass substrates 51a and 51b. The glass substrates 51a and 51b were fixed by irradiating ultraviolet rays. Next, the electrolytic solution was injected into the opening of the spacer 53, and then the opening was sealed with a resin that can be wet-cured, whereby the sample of Example 1 was produced.

(Comparative Example 1)
A sample of Comparative Example 1 was prepared in the same manner and procedure as in Example 1 except that tetrabutylammonium tribromide: 10 mmol / L instead of copper chloride: 10 mmol / L.

(Example 2)
A sample of Example 2 was prepared in the same manner and procedure as in Example 1 except that the molar concentration of tetrabutylammonium tribromide was 2 mmol / L.

(Comparative Example 2)
A sample of Comparative Example 2 was prepared in the same manner and procedure as in Example 1 except that tetrabutylammonium tribromide: 10 mmol / L instead of copper chloride: 2 mmol / L.

(Comparative Example 3)
A sample of Comparative Example 3 was prepared in the same manner and procedure as Example 1 except that tetrabutylammonium tribromide was not added.

(Sample evaluation)
About each sample of the said Example and comparative example, permeability, decoloring property, and deposition voltage were evaluated.

(Transparency)
Each sample of Examples and Comparative Examples was injected into a spectrophotometer cell (S10-UV-1 manufactured by GL Sciences Inc.) having an optical path length of 1 mm. Subsequently, the transmission spectrum was measured using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.), the average value of the transmittance in the visible light region (wavelength 400 nm to 800 nm) was determined, and the transmittance was evaluated.

(Decolorization)
Using a digital fiber amplifier (E3X-DA11AN-S, manufactured by OMRON Corporation) as a light source, irradiating each sample of Examples and Comparative Examples with laser light having a wavelength of 635 nm at room temperature (25 ° C.) The light transmittance in the initial state (hereinafter referred to as “initial transmittance”) was measured with the mounted detector. Next, a voltage of 2.3 V was applied between the ITO films 52a and 52b, and the light transmittance of the sample was monitored with the light transmittance meter. When the light transmittance was reduced to 20%, 0.8V was applied. A reverse voltage was applied to the sample, and the time until returning to the initial transmittance was measured. Then, the sample that returned to the initial transmittance within 30 seconds was judged as good (◯), and the sample that took more than 30 seconds to return to the initial transmittance was judged as defective (x), and the decoloring property was evaluated.

(Deposition voltage)
The voltage applied to each sample in the examples and comparative examples was swept from 0 V to 2.7 V, and the voltage at the time when the light transmittance reached 90% of the initial transmittance was defined as the deposition voltage.

(Measurement result)
Table 1 shows the Br ₃ ⁻ molar concentration X _TBr and the Cu ²⁺ molar concentration X _Cu , the light transmittance (average value), the decoloring property, and the deposition voltage of each sample of Examples and Comparative Examples. Yes.

In Table 1, the Br ₃ ⁻ molar concentration X _TBr was calculated from the ion equilibrium in the electrolyte.

That is, the electrolytic solution was subjected to composition analysis by ICP-AES (inductively coupled plasma-emission spectroscopy) method, and the molar concentration of the cation and the molar concentration of the anion were determined. Since the total amount of the cation charge and the total amount of the anion charge in the electrolytic solution are always in a chemical equilibrium state, the molar concentration of ions other than Br ⁻ and Br ₃ ⁻ and the concentration of Br element And the molar concentration of Br ₃ ⁻ was calculated.

For example, in Example 1, when the ion concentration contained in the electrolytic solution was analyzed using the ICP-AES method and ion chromatography, the molar concentration of Ag ions was 50 mmol / L, and tetrabutylammonium ions It was found that the molar concentration was 260 mmol / L, and nitrate ions were 50 mmol / L as anions. The molar concentration of Br element was found to be 280 mmol / L. Accordingly, when the molar concentration of Br ₃ ⁻ is x, the total amount of charges of the cation is 310 (= 50 + 260) mmol / L, and the total amount of charges of the anion is {50+ (280−3x) + x}. Since both are chemically balanced, 310 = {50+ (280−3x) + x}, and the molar concentration x of Br ₃ ⁻ is calculated as 10 mmol / L.

Since Example 1 contains 10 mmol / L Br ₃ ⁻ , the color erasing property is good, and since the coloring to the electrolytic solution is suppressed, the light transmittance is as high as 91%, and the color erasing property is high. It was found that it was possible to achieve both transparency and permeability.

In contrast in Comparative Example 1, Br ₃ ^- does not contain, because it contains only Cu ²⁺ of 10 mmol / L as a decolorizer, decoloring property was good, Cu ²⁺ It was found that the liquid itself colored the electrolyte, and thus the light transmittance was reduced to 76%, and the transmittance was significantly inferior to that of Example 1.

  FIG. 3 shows the transmission spectra of Example 1 and Comparative Example 1, where the horizontal axis represents wavelength (nm) and the vertical axis represents light transmittance (%). In the figure, the solid line is Example 1, and the broken line is Comparative Example 1.

As is apparent from FIG. 3, in Comparative Example 1, since the sample is colored with Cu ²⁺ , the light transmittance gradually increases in the range of 400 to 650 nm. On the other hand, Example 1 rises steeply because coloring to the sample is suppressed, and it can be seen that Example 1 has better permeability than Comparative Example 1.

In addition, Example 2 contains 2 mmol / L Br ₃ ⁻ , and in this case, coloring to the electrolytic solution is also suppressed. Therefore, the decoloring property is good and the light transmittance is as high as 98%. It was found that both decolorization and transparency were possible.

On the other hand, Comparative Example 2 does not contain Br ₃ ^{− and} contains 2 mmol / L of Cu ^2+, so the decoloring property is good, but Cu ²⁺ itself colors the electrolyte. For this reason, the light transmittance was 95%, and it was found that the transmittance was inferior compared with Example 2 in which the same amount of decolorizer was added.

  That is, when Example 2 and Comparative Example 2 are compared, the content of the decolorizer ions is 2 mmol / L, and the light transmission is higher than that of Example 1 and Comparative Example 1 where the content is 10 mmol / L. Although the difference in rate was reduced, it was found that Comparative Example 2 was inferior in permeability compared to Example 2.

  Comparative Example 3 had a light transmittance of 100%, but since no decolorizer was added, it was found that the decolorability was poor and was not suitable for an optical device that repeats precipitation and redissolution.

FIG. 4 is a graph showing the relationship between decolorizer ions (Br ₃ ⁻ or Cu ²⁺ ) and light transmittance, the horizontal axis is the molar concentration of decolorizer ions (mmol / L), and the vertical axis is the light. Transmittance (%). In the figure, ◯ indicates an example, and X indicates a comparative example.

As is apparent from FIG. 4, when comparing the same amount of Br ₃ ⁻ and Cu ²⁺ , Br ₃ ⁻ is less colored in the sample than Cu ²⁺ and is superior to the permeability. I know that there is. It has also been found that it is effective to contain at least 2 mmol / L or more Br ₃ ⁻ in the electrolytic solution in order to achieve both transparency and decoloring property.

Br ₃ ^- except that the molar concentration X _TBr and Cu ²⁺ molarity X _Cu of, was added tetrabutylammonium tribromide and copper chloride so that the values shown in Table 2 in the electrolyte solution, Example 1] Samples of Examples 11 to 14 were prepared by the same method and procedure as Example 1.

  Next, the permeability, decoloring property, and deposition voltage were evaluated for the samples of Examples 11 to 14 in the same manner and procedure as in [Example 1].

Table 2 shows Br ₃ ⁻ molar concentration X _TBr , Cu ²⁺ molar concentration X _Cu , (X _TBr + 3X _Cu ) value, light transmittance, decoloring property, and deposition voltage of each sample of Examples 11-14. Is shown. In Table 2, the measurement results of Example 1 are shown again for comparison.

As is clear from the comparison between Example 1 and Examples 11-14, the deposition voltage in Example 1 was 2.3 V, whereas in Examples 11-14, the deposition voltage decreased to 2.0 V. . That is, it was found that the deposition voltage can be reduced by containing at least 1 mmol / L or more of Cu ²⁺ in the sample (electrolytic solution) as compared with Example 1 that does not contain Cu ²⁺ . .

As is clear from Examples 11 to 14, Br ₃ as the molar concentration X _Cu of ^{_{Cu 2+ (X TBr + 3X Cu}} ) value is 23 or less ^- for adjusting the respective molar concentrations of Cu ²⁺ Thus, it was found that a light transmittance of 80% or more can be secured.

That is, by adding 1 mmol / L or more of Cu ²⁺ in the electrolyte and _{setting the} value of (X _TBr + 3X _Cu ) to 23 or less, the light transmittance can be secured 80% or more, and the transparency and decoloring It was confirmed that the deposition voltage can be suppressed low without impairing the properties, and it is possible to realize a long-life electrolyte solution with reduced voltage load.

  It is possible to realize an electrolyte solution that can achieve both transparency and decoloring property and can suppress the deposition voltage, and can realize an optical device in which the light transmittance is variable by repeating deposition and re-dissolution of metal.

2 First transparent electrode 3 Electrolyte layer 4 Second transparent electrode 8 Electrolytic solution

Claims (11)

An electrolytic solution in which at least a metal compound, a color erasing agent, and a supporting electrolyte are dissolved in a solvent,
The electrolytic solution, wherein the decolorizer contains at least 2 mmol / L or more of tribromide ions.   The electrolytic solution according to claim 1, wherein the content of the tribromide ions is 100 mmol / L or less.   3. The electrolytic solution according to claim 1, wherein the color erasing agent contains 1 mmol / L or more of divalent copper ions in addition to the tribromide ions.   The electrolytic solution according to claim 3, wherein the copper ions are contained in the form of copper halide. When the molar concentration of the tribromide ion is represented by X _TBr mmol / L and the molar concentration of the copper ion is represented by X _Cu mmol / L,
X _TBr + 3X _Cu ≦ 23
The electrolyte solution according to claim 3 or 4, wherein:   6. The electrolytic solution according to claim 1, wherein the tribromide ion is contained in the form of alkylammonium tribromide.   The electrolytic solution according to claim 1, wherein the metal compound includes an Ag compound.   The electrolytic solution according to any one of claims 1 to 7, wherein the metal compound is contained in a range of 5 to 1000 mmol / L.   The electrolytic solution according to claim 1, wherein the supporting electrolyte contains bromide ions.   10. The electrolytic solution according to claim 1, wherein the supporting electrolyte is 0.5 to 50 times the metal compound in terms of molar concentration. An optical device in which an electrolyte layer is interposed between a pair of transparent electrodes,
The optical device, wherein the electrolyte layer includes the electrolytic solution according to any one of claims 1 to 10.

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