KR100476615B1 - Optical Device and Electrolytic Solution - Google Patents

Abstract

The present invention is a pair of substrate transparent to one or more substrates; At least one transparent electrode disposed on one side of the transparent substrate; At least one counter electrode; A spacer provided between the distal ends of the pair of substrates; And a reversible electro-deposition (RED) solution as a filter material provided in the space between the pair of substrates, the RED solution comprising a silver salt and DMSO and other solvents to dissolve the silver salt. It provides an optical device comprising a mixed solvent.

The transparent electrode and the counter electrode are driven by the application of a voltage, and the silver salt is reversibly precipitated and dissolved under the control of the voltage, thereby making the RED solution colored or colorless, respectively, so that the light amount is controlled.

Description

Optical Device and Electrolytic Solution

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device such as a display device for displaying numerals or letters or an X-Y matrix display, an optical filter capable of controlling light transmittance or reflectance, and an electrolyte solution used in the optical device.

Electrochromic materials (hereinafter referred to as EC materials) have been used in display devices driven by voltage, such as a digital clock for displaying time.

A display device using an electrochromic material, that is, an electrochromic display element (hereinafter referred to as ECD) is a non-light-emitting display device, which is displayed by reflected light or transmitted light as an electrochemical dimming element, so that the observer It has the advantage of low fatigue, relatively low driving voltage and low power consumption. For example, as disclosed in Japanese Patent Laid-Open No. 59-24879, a liquid ECD using an organic molecular system viologen molecular derivative which reversibly forms a colored or colorless state as an EC material is known.

However, when an EC material such as a viologen molecular derivative is used for an ECD device, the response speed and shielding degree required by an actual device are insufficient, so that it is far from practical use. In addition, although it was necessary to control the light transmittance in the visible light region (wavelength 400 to 700 nm) as a light quantity adjusting device, the EC material to date did not fully satisfy the said required point.

In such a situation, the present inventors have focused on a light control element using precipitation or dissolution of a metal salt instead of ECD, and have developed an electrochemical light control element using silver deposition or dissolution. As a result, an element having desired characteristics in both response speed and shielding degree was obtained.

Nevertheless, it is found that devices using a high freezing point (DMSO 18 ° C.) solvent such as dimethyl sulfoxide (DMSO) have a high reversibility of precipitation and dissolution of silver, but have a problem of being easily solidified at low temperatures due to very poor low temperature properties. It became.

Therefore, it is an object of the present invention to provide an optical device which can be driven with low power consumption, can control the transmission or reflection of light in the visible light region, and also has good low temperature properties, and an electrolyte solution used for the optical device.

In order to achieve the above object, the present invention

A pair of substrates in which at least one substrate is transparent;

At least one transparent electrode disposed on one side of the transparent substrate;

At least one counter electrode;

A spacer provided between the distal ends of the pair of substrates; And

An electrolyte solution provided in a space between the pair of substrates,

The electrolyte provides an optical device comprising a mixed solvent comprising a silver salt (hereinafter referred to as a silver salt) such as AgF, AgCl, AgBr, AgI and AgSCN and at least two solvents for dissolving the silver salt. .

In the optical device, the transparent electrode and the counter electrode are driven by the application of a voltage, and the silver salt precipitates and dissolves under the control of the voltage, thereby making the electrolyte solution colored or colorless, respectively.

Further, according to the present invention, there is provided a silver salt; And a mixed solvent including two or more solvents for dissolving the silver salt.

The electrolyte solution is provided between a pair of electrodes to which a voltage is applied, and the silver salt precipitates and dissolves under the control of the voltage, thereby making the electrolyte solution colored or colorless, respectively.

Silver (complex) salts in optical devices and electrolytes according to the invention prevent the solution from absorbing light in the visible region (wavelengths 400 to 700 nm) when the solution is prepared and are almost uniform in the visible region when the solution is colored. Since shielding is possible, silver (complex) salt is used as a reversible plating material for depositing or dissolving silver, that is, a material for reversible electro-deposition (RED). In addition, silver (complex) salt satisfactorily exhibits reversibility between precipitation and dissolution by controlling the driving voltage applied to the electrode. In contrast, although the cyanide solution used in the plating bath has been known to be used to precipitate silver from the silver (complex) salt, the cyanide solution causes problems of securing a safe working environment and treating the waste liquid. Therefore, in this invention, a non-cyanide silver salt is used.

As described above, a non-light-emitting optical device such as an optical filter suitable for visible light region with low power consumption by using a reversible system for depositing or dissolving silver from a silver (complex) salt onto a transparent electrode, that is, a material for RED as a material for reversible plating. Can be provided.

In addition, an important point in the optical device and the electrolyte according to the present invention is that the solvent used to prepare the silver salt solution includes two or more solvents (mixed solvents). Therefore, when using a solvent of dimethyl sulfoxide (DMSO) alone as mentioned above, there is a problem that the operating environment of the device is limited because the low temperature characteristics are poor, and mixed by mixing DMSO and other solvents compatible with DMSO in particular By using a solvent, the low temperature characteristic of a solution can be improved and the usable temperature range can be expanded.

As a result, in the optical device and the electrolytic solution of the present invention, a mixed solvent in which various kinds of solvents having high reversibility of silver precipitation or dissolution but poor temperature characteristics is used. Contributes to dissolution and prevents solidification of the electrolyte at low temperatures. This prevents the electrolyte from freezing even in devices used in cold regions.

In the optical device and the electrolyte according to the present invention, the mixed solvent is preferably propylene carbonate (PC), acetonitrile (AN), dimethylformamide (DMF), diethylformamide (DEF), N, N -Dimethylacetamide (DMAC), N-methylpropionamide (MPA), N-methylpyrrolidone (MP), 2-ethoxyethanol (EEOH), 2-methoxyethanol (MEOH), dimethyl sulfoxide (DMSO ), Dioxolane (DOL), ethyl acetate (EA), tetrahydrofuran (THF), methyltetrahydrofuran (MeTHF), dimethoxyethane (DME) and γ-butyrolactone (γ-BL) At least two solvents selected.

Next, the chemical structural formula of the solvent is shown.

<Chemical Structural Formula>

The mixed solvent described above preferably includes various kinds of solvents having different structures from each other. For example, the mixed solvent may include a solvent having a cyclic structure and a solvent having a bicyclic structure (eg, a chain structure). Alternatively, even if both solvents have a cyclic structure, heterocyclic compounds and nonheterocyclic compounds, 5-membered ring compounds and 6-membered ring compounds, and heterocyclic compounds having one hetero atom, and two kinds of solvents Heterocyclic compounds having heteroatoms may be combined. In addition, even for a compound having a bicyclic structure, a combination of a compound having a chain structure and a compound having a non-chain structure, and a combination of a compound having a hetero atom and a compound having no hetero atom may be possible.

In particular, the mixed solvent is preferably a mixed solvent comprising dimethyl sulfoxide and another solvent. The fraction of dimethyl sulfoxide in this mixed solvent is preferably equal to or greater than that of other solvents, which makes the solubility and low temperature properties of the silver salt compatible. For example, when the mixed solvent is maintained at −20 ° C. for 2 hours at a ratio of 2: 3 of silver salt to the supporting electrolyte (to be described later), the mixed solvent preferably includes dimethyl sulfoxide and acetonitrile, and dimethyl The mixing ratio of sulfoxide: acetonitrile is 50:50 to 55:45 in volume ratio, or the mixed solvent includes dimethyl sulfoxide and a solvent having a cyclic structure, and dimethyl sulfoxide: mixing of a solvent having a cyclic structure The ratio is 55:45 to 60:40. Extremely small amounts of dimethyl sulfoxide cause salt precipitation, and excessive excess is likely to cause coagulation at low temperatures. However, the mixing ratio of mixed solvent dimethylsulfoxide (DMSO): other solvent may vary in the range of 60:40 to 20:80 with respect to a predetermined ratio of silver salt and supporting electrolyte as described below.

As the silver salt, silver halides such as AgBr are preferably used, and a solution having a concentration of 0.005 to 2.0 mol / L is preferably used.

In addition, for the dissolution of silver halides, silver halides preferably form a complex salt by using a supporting salt (eg, sodium halide, potassium halide, calcium halide or quaternary ammonium salt) which can provide the same or different types of halogenated elements. desirable.

In this case, the concentration of the supporting salt is preferably 1/2 to 5 times the silver salt concentration.

In order to deposit or dissolve silver acting as a filter material, a transparent electrode (especially an ITO electrode obtained by doping tin indium oxide) as a working electrode is chemically or physically modified to lower the potential at which silver precipitates into the transparent electrode and It is easy to precipitate or dissolve, and can reduce the electrical damage of the transparent electrode and the electrolyte itself.

As a chemical modification method in this case, it is preferable to perform surface treatment of an ITO electrode with palladium by the two-solution process method using a tin solution and a palladium solution. That is, by depositing a palladium nucleus on the ITO single substrate, the surface activation treatment of the ITO electrode is performed to improve the surface activity of the ITO electrode.

In this case, as a tin solution, a solution in which 0.10 to 1.0 g of tin chloride (SnCl ₂ ) is dissolved in 1 L of 0.010 to 0.10% HCl is used. As a palladium solution, 0.10 to 1.0 g of palladium chloride (PdCl ₂ ) is 0.010 to 0.10. A solution dissolved in 1 L of% HCl can be used.

As a physical modification method, a method of depositing a metal more precious than silver on each ITO electrode can be used.

In the case where the silver halide is a silver iodide having a particularly high reversibility, it is preferable to add a supporting electrolyte (supporting salt) such as sodium iodide (NaI) to the solution at a concentration equal to 20 times the concentration of silver iodide in order to increase the conductivity of the RED solution. desirable.

In addition, in order to increase the reversibility when silver precipitates from the electrolyte or silver is dissolved in the electrolyte, an additive such as ascorbic acid is preferably added to the solution. Ascorbic acid is preferably added at a rate of 5 to 200 mmol / L.

Silver salts used as RED materials allow for nearly uniform shielding in the visible region, but are produced when silver dissolves from the electrode to the solution in precipitation from or dissolution into silver (complex) salts. By-products lead to turbidity of the solution system and difficulty in maintaining the transparency of the solution.

Investigation of this problem has revealed that iodine, which occurs when dissolving precipitated silver in a solution using silver (complex salt) as a RED material, causes the solution to become cloudy. Therefore, yellow turbidity of a solution can be prevented by adding the reducing agent which reduces precipitation iodine to an ionic state.

As a result, it is preferable to use a solution in which silver halide is dissolved and a reducing agent is added as the RED solution.

In particular, in a system in which silver iodide is used and sodium iodide is further added, precipitation of iodine generated when dissolving precipitated silver is suppressed, a decrease in transmittance of the RED solution is prevented, and a change in the crude composition due to iodine generation is prevented. It is preferable to use ascorbic acid and / or tin chloride as a reducing agent for suppressing. In this case, it is preferable to add a reducing agent in the range of the same or twice the concentration of silver halide or the like.

Preferably, the solution does not absorb light in the visible region when the solution is colorless, and the ITO electrode absorbs less light in the visible region so that the substrate electrode, which causes the solution to be colored or colorless, acts as an optical filter, resulting in near uniform absorption. It is preferable to obtain.

When repeating the colored and colorless state using the RED solution, the device is too small to stir the solution system. Therefore, the device is preferably driven by current control in which the precipitation and dissolution reaction of silver are easy to quantify.

As a driving method for coloring and colorless a solution by such a current control, driving by a current which changes from a high current value to a low current value in a rectangular shape in order to improve the speed of coloring and colorlessness (precipitation and dissolution rate of silver). The law is preferred. In addition, in order to alleviate damage to the substrate due to repetition of the deposition and dissolution of silver, it is also preferable to use a driving method with a current that changes from a low current value to a high current value into a rectangle.

Hereinafter, embodiments of the present invention will be described.

1 and 2 are schematic diagrams showing an optical filter 10 according to an embodiment according to the present invention.

In the optical filter 10, a pair of transparent substrates 4 and 5 (e.g., glass plates) forming a battery are arranged in parallel at regular intervals, and each transparent substrate functions as a display window. On the inner surface of this substrate, transparent working electrodes 2 and 3 (eg, ITO electrodes) are provided so as to face each other. At least one of these working electrodes 2 and 3 is used as an electrode for coloring or colorization.

The counter electrode 6 is provided on all the entire circumferences of the substrates 4 and 5 and also serves as a spacer. For example, the counter electrode includes a silver plate. Although not shown, the optical filter 10 is provided with the reference electrode which is a silver wire, for example.

The RED solution 1 is enclosed between the transparent electrodes 2 and 3 facing each other to contact the electrodes 2 and 3 and the donor electrode. RED solutions contain silver (complex) salts used as electrochromic materials. The DC driving voltage is applied across the counter electrode and the transparent electrodes 2 and 3 for a specific time so that the silver (complex) salt induces a redox reaction on the ITO electrode as a cathode, as shown in Scheme 1 below, so that the transparent As silver precipitates on the electrode, the display window is colored.

With this silver precipitation on the electrode, certain coloring by silver precipitation is observed from the display window, and the solution acts as the filter material. Then, the filter function of the solution due to this coloring, i.e., the visible light transmittance (or coloring density) of the solution depends on the magnitude of the voltage or its application time. Thus, by adjusting this voltage or its application time, the optical filter 10 can act as a filter having a variable transmittance. With the coloring solution, the reflectance of visible light also changes, so that this solution can act as a filter with variable reflectance.

This optical filter 10 may have electrodes 2 and 3 made to be formed over almost all surfaces in the cell. However, it may actually be formed as illustrated in FIGS. 3 and 4.

The transparent electrodes provided on the transparent substrates 4 and 5 are not only the center electrodes 2a and 3a but also annular electrodes arranged around the center electrodes 2a and 3a concentrically at fine intervals, respectively. Polarized into (2b), (2c), (2d), (2e) and (3b), (3c), (3d) and (3e). At the outermost ends, silver counter electrodes 6A and 6B for potential compensation are provided around the counter electrodes 2e and 3e.

Such electrodes (2a) and (3a), (2b) and (3b), (2c) and (3c), (2d) and (3d), (2e) and (3e), and (6A) and (6B) Drive power source 8A, 8B, 8C, 8D with wiring of 9A, 9B, 9C, 9D, 9E, and 9F of each thin chrome wire , (8E) and (8F).

The electrode substrates 4 and 5 are arranged at predetermined intervals by the spacer 7 (in FIG. 1, the counter electrode 6 is provided), and the RED solution 1 is enclosed therebetween.

RED solution (1) is divided into electrodes (2a) and (3a), (2b) and (3b), (2c) and (3c), because the redox reaction (i.e. density) is adjusted according to the applied voltage. Depending on the voltages (V1, V2, V3, V4 and V5) applied to (2d) and (3d), (2e) and (3e) respectively, the amount of silver precipitation from the RED solution on the cathode of the split electrode can be changed. have. Moreover, the potential compensation voltage V6 is applied to the electrodes 6A and 6B.

As a result, if all of the applied voltages are the same (V1 = V2 = V3 = V4 = V5), all parts of the RED solution 1 can be colored uniformly, and the coloring density can be changed uniformly with the voltage.

If a different voltage is applied to each electrode (e.g. V1 < V2 < V3 < V4 < V5), the color increases from center to end (in other words, the transmittance decreases from center to end). This is advantageous in that the optical filter 10 is used as the optical stop for CCD (charge coupled device) of a TV camera, which can cope with an increase in CCD integration. If the voltage is applied in the reverse order, the transmittance increases from the center to the end.

Therefore, by applying a voltage to the split electrode, the density or gradation can be adjusted to various types of applied voltages, so that an optical filter is useful for various fields of use.

As described above, according to the present embodiment, the RED material containing silver salt is used as a filter material for adjusting the light quantity of the optical device, and the density of the colored RED material is a completely different concept from the case of using a conventional RED material. Based on this, the drive of the transparent electrode and the counter electrode can be changed by adjusting (particularly, applied voltage). By using these characteristics, the color of the optical filter can be grayed out. As a result, the use of a RED material can provide a filter having a larger capacity and consuming very little power as compared to a conventional variable ND filter operating mechanically as a light amount adjusting device.

This embodiment is described in more detail with reference to specific examples using the optical filter having the structure shown in FIGS. 1 and 2.

<Example 1>

Driving Experiments of Devices Using Silver Halide (AgX)

In this example, reversible precipitation and dissolution of silver were studied using silver halides. As silver halide silver bromide (AgBr) having higher reversibility than other silver (complex) salts was used.

In order to know the precipitation potential of silver, the change of transmittance at a constant potential was investigated. A mixed solvent comprising dimethyl sulfoxide (DMSO) and acetonitrile (AN) having a mixing ratio of dimethyl sulfoxide: acetonitrile 1: 1 was used as the solvent. The concentration of silver bromide was 500 mmol / L. Silver bromide was dissolved and sodium iodide (NaI) was dissolved in the solution at 750 mmol / L to increase conductivity, and ascorbic acid was added to the solution at 50 mmol / L. This solution, that is, the electrolyte solution, was used as the RED solution.

The change in transmittance was investigated over time while keeping the voltage applied to the battery constant. That is, a constant potential driving method was used to drive the optical filter, and silver was precipitated for 2 seconds at -0.8 V (cell voltage) and dissolved for 2 seconds at +1.0 V (cell voltage). Here, an ITO electrode was used as a working electrode, silver wire was used as a reference electrode, and a silver plate was used as a counter electrode.

The results are shown in FIGS. 5 and 6. Ag precipitation on the cathode advances with voltage application time to reduce the transmittance, and the shielding is satisfactory throughout the visible light region (wavelength of 400 to 700 nm). When the voltage polarity is reversed, the transmittance increases due to melting of the precipitated silver. From this change in transmittance, it was found that the precipitation and dissolution of silver were satisfactorily reversible.

<Example 2>

Cryopreservation experiment

In Example 1, electrolytes were prepared using various mixed solvents having a mixing ratio of DMSO: another solvent of 1: 1, and the cryopreservation characteristics of each electrolyte solution were investigated in comparison with the others. The results are shown in Table 1, where the state without freezing is indicated by o, and the coagulated or salt (NAI) precipitated state is indicated by x.

Another solvent mixed with DMSO Cold storage conditions -10 ℃, 2 hours -20 ℃, 2 hours AN ○ ○ γ-BL ○ ○ DMAC ○ x- ○ NMP ○ x- ○ PC ○ x- ○ DOL ○ ○ AN: acetonitrile, γ-BL: γ-butyrolactone, DMAC: dimethylacetamide, NMP: n-methylpyrrolidone, PC: propylene carbonate, DOL: dioxolane

From these results, it is understood that when a mixed solvent in which DMSO and another solvent are mixed is used, the electrolyte solution does not easily coagulate at low temperatures, thereby improving the low temperature characteristics. When used alone with DMSO, the electrolyte solidified under all of the above low temperature conditions.

<Example 3>

Selection of a suitable mixed solvent

In order to determine the mixing ratio of the mixed solvent used and the concentration of the solute, an optimal study was conducted with the electrolyte solution of the RED solution of Example 1. An electrolyte comprising 500 mmol / L AgBr and 750 mmol / L NaI was prepared at various mixing ratios of DMSO: AN. The electrical conductivity of the electrolyte maintained at −20 ° C. (1000 / T ≒ 3.95), room temperature (1000 / T ≒ 3.41) and 60 ° C. (1000 / T ≒ 3.95) for two hours is driven by a high frequency of 1 to 100 kHMz. It measured by fixing electrolyte solution between a pair of electrode. The results are shown in FIG. 7 as temperature dependence of the electrical conductivity of the electrolyte in the case of mixed solvents of various mixing ratios (volume ratios).

In addition, the properties after holding for 2 hours at −20 ° C. for electrolytes having various mixing ratios of DMSO: AN and the ease of handling the electrolyte at room temperature (no change in mixing ratio when charging the battery with a mixed solvent). Impact). The results are shown in Table 2 below. Here, the term "salt precipitated" in the item "maintained at -20 ℃" means "precipitation of NaI", in the "ease of handling at room temperature", ◎ "very good", ○ "excellent" , Δ indicates "may be acceptable" and x indicates "not acceptable".

DMSO / AN (volume ratio) Maintained at -20 ℃ Ease of handling at room temperature 45:55 Salt precipitation in certain cases × 50:50 No freezing △ 55:45 No freezing ◎ 60:40 Partially solidified in certain cases ○ 80:20 Solidified in certain cases ○

From the above results, electrical conductivity tends to decrease at low temperatures, and as the DMSO ratio increases, low temperature properties tend to be poor due to the decrease in coagulation and electrical conductivity. However, it was also observed that sufficient DMSO concentration was needed to dissolve the supporting electrolyte well. In addition, when the DMSO concentration is excessively low, it is easy to induce precipitation of salts (NaI: the same applies below) in the electrolyte maintained at low temperature. As a result, in terms of both low temperature properties and solubility, the DMSO concentration was determined to be better at DMSO: AN = (50:50) to (55:45), suggesting that DMSO: AN = (55:45) is optimal. Found.

Next, the polarization of the electrolyte was investigated with silver salts of various concentrations and a mixed electrolyte with a fixed ratio of DMSO: AN = (55:45). The polarization was compared by measuring the voltage across the working electrode and the reference electrode when silver precipitated on the working electrode of a constant current of 7 mm diameter and comparing the measured voltage corresponding to the polarization. FIG. 8 shows the results as voltages for the current characteristics of the electrolyte for different concentration ratios (mmol / mmol) of silver salt to the supporting electrolyte.

This result shows that the smallest polarization obtained with 650 mmol / L AgBr and 700 mmol / L NaI is clearly optimal. However, this results in poor reversibility, so that the concentrations giving the second smallest polarization of 500 mmol / L AgBr and 750 mmol / L NaI have been found to be practically optimal.

<Example 4>

Solubility in Solutes

As described in Example 3, various types of silver salts and various types of the mixing ratio of another solvent to DMSO were fixed at 50:50 and the ratio of silver salts to the supporting electrolyte was fixed at 500 mmol / L: 750 mmol / L The solubility of solutes was investigated for various combinations of supported electrolytes. The results obtained at room temperature are shown in the following Tables 3, 4 and 5, where? Denotes "easy solubility", ○ denotes "soluble",? Denotes "solubility", x denotes "insoluble", and- "Not measured".

AN NaI NaBr LiI LiBr AgI - ◎ - ◎ AgBr ◎ - ○ -

PC NaI NaBr LiI LiBr AgI - × - ◎ AgBr △ - ○ -

DOL NaI NaBr LiI LiBr AgI - × - ◎ AgBr △ - ○ -

Table 3 shows that AgI is well combined with NaBr or LiBr, and AgBr is well combined with NaI or LiI in a mixed solvent of DMSO and AN. Similarly, Table 4 shows that AgI is well combined with LiBr, AgBr is well combined with LiI in a mixed solvent of DMSO and PC, Table 5 shows AgI is well combined with LiBr, and AgBr is a mixed solvent of DMSO and DOL. In combination with LiI.

Example 5

Selection of Other Suitable Mixed Solvents

The RED solution of Example 1 was a mixture of various mixing ratios (volume ratios) of DMSO and another various solvents, and maintained at −20 ° C. for two hours. The results are shown in Tables 6 to 11, where "-" indicates no measurement, "PC" is propylene carbonate, "DME" is 1,2-dimethoxyethane, "DEE" is 1, 2-diethoxyethane, "DMF" stands for N, N-dimethylformamide, "DOL" stands for 1,3-dioxolane and "DMAC" stands for N, N-dimethylacetamide. In addition, the case of "solidified" and "salt precipitated" in the table includes cases in which the electrolyte may be solidified in addition to the case where the electrolyte is totally solidified, and may be precipitated in addition to the case where the electrolyte is totally precipitated. .

DMSO / PC (volume ratio) Maintained at -20 ℃ 50:50 Precipitated salt 55:45 Partially precipitated 60:40 Not frozen 70:30 Solidified

DMSO / DME (volume ratio) Maintained at -20 ℃ 50:50 Precipitated salt 55:45 Partially precipitated 60:40 Precipitated salt 70:30 Precipitated salt

DMSO / DEE (volume ratio) Maintained at -20 ℃ 50:50 Precipitated salt 55:45 Precipitated salt 60:40 Precipitated salt 70:30 Precipitated salt

DMSO / DMF (Volume Ratio) Maintained at -20 ℃ 50:50 - 55:45 - 60:40 - 70:30 Solidified

DMSO / DOL (volume ratio) Maintained at -20 ℃ 50:50 Precipitated salt 55:45 Not frozen 60:40 Not frozen 70:30 Solidified

DMSO / DMAC (Volume Ratio) Maintained at -20 ℃ 50:50 Precipitated salt 55:45 - 60:40 Partially solidified 70:30 Solidified

The results, together with those of Table 2, indicate that the mixed solvent comprising dimethyl sulfoxide and other solvents containing dimethyl sulfoxide as the main fraction is preferred for the solubility and low temperature properties of silver salts and compatible support salts.

In this case, the mixed solvent preferably includes several kinds of solvents having different structures. For example, a solvent having a chain structure (the above DMSO) and a solvent having a cyclic structure (the PC or the DOL) are included. DMSO has a chain structure in which two hydrocarbon groups (methyl groups) are bonded through a sulfur atom (hetero atom), whereas AN has only one hydrocarbon group (methyl group) and thus cannot be called a chain structure. It can be said that the mixed solvent includes a solvent having a structure different from each other.

The mixing ratio of the solvent in the mixed solvent including dimethyl sulfoxide and acetonitrile is preferably (dimethyl sulfoxide: acetonitrile) = (50:50) to (55:45) in volume ratio, and the dimethyl sulfoxide and cyclic structure In a mixed solvent including a solvent having a solvent, the solvent is preferably (volume having a dimethyl sulfoxide: cyclic structure) = (55:45) to (60:40) in a volume ratio. When the dimethyl sulfoxide is excessively small, salt precipitation is likely to occur, and when excessively large, the dimethyl sulfoxide is easily solidified at low temperature. Conversely, excessively large amounts tend to cause coagulation at low temperatures. Salt precipitation is thought to be due to NaI precipitation. Some of the electrolytes with precipitated salts did not freeze and some coagulated.

<Example 6>

Suitable mixed solvents based on solute concentration

In the case of the electrolyte solution, which is the RED solution of Example 1, another kind of solvent was maintained at −30 ° C. for 12 hours at various mixing ratios (volume ratios) with DMSO, and then its properties were investigated. The results are shown in Tables 12 to 16, where "-" indicates no measurement.

DMSO: AN 50:50 40:60 30:70 20:80 10:90 AgBr (mmol / L) 453 363 273 180 90 NaI (mmol / L) 680 545 410 270 136 -30 ℃, 12 hours Not frozen Not frozen Not frozen Not frozen -

DMSO: PC 50:50 40:60 30:70 20:80 10:90 AgBr (mmol / L) 453 363 273 180 90 NaI (mmol / L) 680 545 410 270 136 -30 ℃, 12 hours Not frozen Not frozen Not frozen Not frozen -

DMSO: AN 50:50 40:60 30:70 20:80 10:90 AgI (mmol / L) 453 363 273 180 90 LiBr (mmol / L) 680 545 410 270 136 -30 ℃, 12 hours Not frozen Not frozen Not frozen Not frozen -

DMSO: PC 50:50 40:60 30:70 20:80 10:90 AgI (mmol / L) 453 363 273 180 90 LiBr (mmol / L) 680 545 410 270 136 -30 ℃, 12 hours Solidified Not frozen Not frozen Not frozen -

DMSO: DOL 50:50 40:60 30:70 20:80 10:90 AgI (mmol / L) 453 363 273 180 90 LiBr (mmol / L) 680 545 410 270 136 -30 ℃, 12 hours Not frozen Not frozen Not frozen Not frozen -

The results indicate that the mixed solvent preferably comprises DMSO and another solvent. Mixing ratios for preparing mixed solvents provide good low temperature properties but depend on the total concentration of the solute including the silver salt and the supporting electrolyte. In particular, if the total solute concentration is reduced by reducing the amount of silver salts and at the same time the amount of supported electrolyte, the DMSO fraction is reduced further than the above-mentioned range, so that the mixing ratio range of another solvent is 50:50 to 20:80. Even when expanded, the mixed solvent can be prevented from freezing at low temperatures.

Although the embodiment according to the present invention has been described above, the present embodiment may be changed based on the technical spirit of the present invention.

For example, the above-mentioned RED materials, in particular the type of solvent, the combination and concentration of the components of the RED solution can vary widely, and the silver salts are not limited to those shown in the above examples.

The structure of the optical filter including the ITO electrode pattern as well as the component material and also the driving method are not limited to those described above. For example, in the filter structure, the electrode pattern shown in FIG. 3 may be changed into a stripe type or a lattice type. In addition, the cells can be divided into different polarizing electrodes arranged in parallel with each other to contain different RED solutions from each other.

The above mentioned optical filter may also be combined with another known filter material (eg, organic electrochromic material, liquid crystal, electroluminescent material). Such optical filters can be widely used for the purpose of adjusting the amount of light, including CCD optical apertures, various optical systems, moreover electrophotographic copying equipment and optical communication devices.

As described above, in the present invention, the RED solution containing silver salt is used as a filter material for controlling the amount of light in the optical device, and thus the driving of the counter electrode is based on a concept completely different from using a conventional RED material. The adjustment forms a variable system for the precipitation and dissolution of silver due to the silver salt on the transparent electrode. Thus, the present invention can provide a non-light emitting optical device of smaller power consumption suitable for the visible region using RED materials.

The solvent used to prepare the silver salt solution is a mixed solvent comprising two or more solvents, and dimethyl sulfoxide (DMSO) is used as a mixed solvent, in particular in combination with a solvent having good affinity with DMSO, whereby Low temperature properties can be improved to extend to the usable temperature range. As a result, the problem of limiting the operating conditions of the device due to the poor temperature characteristics of the device when using a single solvent can be solved. Therefore, by using a solvent having high reversibility but poor temperature properties in the form of a mixed solvent in the optical device and the electrolyte according to the present invention, it is possible to prevent the electrolyte from freezing even when the optical device is used in a cold region.

1 is a schematic cross-sectional view showing an embodiment of an optical filter according to the present invention.

FIG. 2 is a conceptual diagram of the optical filter shown in FIG. 1. FIG.

FIG. 3 is a schematic view showing a specific example of an ITO electrode arrangement pattern of the optical filter shown in FIG. 1. FIG.

4 is a schematic cross-sectional view of an embodiment of an optical filter having the ITO electrode arrangement pattern shown in FIG. 3.

Fig. 5 is a spectral diagram showing a change in transmittance when Example 1 of the optical filter according to the present invention becomes colorless.

Fig. 6 is a spectrum diagram showing a change in transmittance when Example 1 of the optical filter according to the present invention is colored.

7 is a graph showing the temperature dependence of the electrical conductivity of an electrolyte solution with respect to various mixing ratios of the mixed solvents used in another embodiment of the optical filter according to the present invention.

8 is a graph showing the voltage versus current characteristics of an electrolyte solution for silver salts of various concentration ratios (mmol / mmol) with respect to a supporting electrolyte in another embodiment of the optical filter according to the present invention.

<Explanation of symbols for the main parts of the drawings>

1: RED solution

2, 3: working electrode

4, 5: transparent substrate

6: counter electrode

10: optical filter

Claims (27)

A pair of substrates in which at least one substrate is transparent; At least one transparent electrode disposed on an inner surface of the transparent substrate; At least one counter electrode; Terminal spacers provided therebetween along the distal ends of the pair of substrates; Is provided in the space between the pair of substrates, and is limited by the terminal spacers, A mixed solvent comprising a first solvent which is dimethyl sulfoxide and at least one second solvent selected from the group consisting of acetonitrile, propylene carbonate and dioxolane, and An electrolyte comprising a first halide anion and a silver halide salt having a supporting salt selected from an alkali metal halide salt or an alkaline earth metal salt and having a second halide anion different from the first halide anion; And A driver that applies a variable voltage to the at least one transparent electrode and the counter electrode to cause the silver salt to be precipitated or dissolved by the applied voltage so that the electrolyte is colored or colorless, respectively. Optical device comprising a. The optical device according to claim 1, wherein the mixed solvent is a mixture of the dimethyl sulfoxide and the second solvent, and the volume ratio of dimethyl sulfoxide to the second solvent is 60:40 to 20:80. The optical device of claim 1, wherein the volume fraction of dimethyl sulfoxide is equal to or greater than the volume fraction of the second solvent. The optical device according to claim 1, wherein the mixed solvent is a mixture of dimethyl sulfoxide and acetonitrile as the second solvent, and the volume ratio of dimethyl sulfoxide: acetonitrile is 50:50 to 55:45. The optical device according to claim 1, wherein the mixed solvent is a mixture of dimethyl sulfoxide and propylene carbonate as the second solvent, and the volume ratio of dimethyl sulfoxide: propylene carbonate is 55:45 to 60:40. The optical device of claim 1, wherein the silver halide is present in the electrolyte at a molar concentration ranging from 0.005 to 2.0 mol / L. The optical device according to claim 1, wherein the supporting salt is present in the electrolyte in a concentration range of 1/2 to 5 times the silver salt. The optical device of claim 1, wherein the transparent electrode is chemically or physically modified to act as a working electrode for depositing or dissolving silver as the optical filter material. The optical device of claim 1 wherein the electrolyte further comprises ascorbic acid. The optical device of claim 9 wherein the ascorbic acid is dissolved at a molar concentration in the range of 5 to 200 mmol / L. A mixed solvent comprising a first solvent which is dimethyl sulfoxide and at least one second solvent selected from the group consisting of acetonitrile, propylene carbonate and dioxolane; Silver halide salts having a first halide anion; And Support salts having a second halide anion different from the first halide anion selected from alkali metal halide salts or alkaline earth metal salts Electrolyte comprising a. The electrolyte of claim 11, wherein the mixed solvent is a mixture of dimethyl sulfoxide and the second solvent, and a volume ratio of dimethyl sulfoxide to the second solvent is 60:40 to 20:80. The electrolyte of claim 11, wherein the volume fraction of dimethyl sulfoxide is equal to or greater than the volume fraction of the second solvent. The electrolytic solution according to claim 11, wherein the mixed solvent is a mixture of dimethyl sulfoxide and acetonitrile, and the volume ratio of dimethyl sulfoxide: acetonitrile is 50:50 to 55:45. 12. The electrolyte solution according to claim 11, wherein the mixed solvent is a mixture of dimethyl sulfoxide and propylene carbonate as the second solvent, and the volume ratio of dimethyl sulfoxide: propylene carbonate is 55:45 to 60:40. The electrolyte of claim 11, wherein the silver halide is present in the electrolyte at a molar concentration ranging from 0.005 to 2.0 mol / L. The electrolyte of claim 11, wherein the supporting salt is present in the electrolyte in a concentration range of 1/2 to 5 times the silver salt. The electrolyte of claim 11, wherein the electrolyte further comprises ascorbic acid. The electrolyte of claim 18, wherein the ascorbic acid is dissolved at a molar concentration ranging from 5 to 200 mmol / L. 9. The optical device of claim 8 wherein the transparent electrode is an ITO electrode physically modified to have a deposited metal layer comprising a metal that is more precious than silver. The optical device according to claim 8, wherein the transparent electrode is an ITO electrode chemically modified by a palladium surface activation treatment. The method of claim 1, wherein the electrolyte comprises a mixture of dimethyl sulfoxide (DMSO) and acetonitrile (AN), the volume ratio of DMSO: AN is 50:50 to 55:45, respectively, the silver halide salt is silver iodide or silver bromide Wherein the supporting salt is sodium bromide or lithium bromide when the silver halide salt is silver iodide, and the supporting salt is sodium iodide or lithium iodide when the silver halide salt is silver bromide. The method of claim 1, wherein the electrolyte comprises a mixture of dimethyl sulfoxide (DMSO) and dioxolane (DOL), the volume ratio of DMSO: DOL is 55:45 to 60:40, respectively, the silver halide salt is silver iodide or silver bromide Wherein the supporting salt is lithium bromide when the silver halide salt is silver iodide and the supporting salt is lithium iodide when the silver halide salt is silver bromide. The method of claim 1, wherein the electrolyte comprises a mixture of dimethyl sulfoxide (DMSO) and propylene carbonate (PC), the volume ratio of DMSO: PC is 60:40, the silver halide salt is silver iodide or silver bromide, silver halide And the supporting salt is lithium iodide when the salt is silver iodide and the supporting salt is lithium iodide when the silver halide salt is silver bromide. The method of claim 11, wherein the electrolyte comprises a mixture of dimethyl sulfoxide (DMSO) and acetonitrile (AN), the volume ratio of DMSO: AN is 50:50 to 55:45, respectively, wherein the silver halide salt is silver iodide or silver bromide And the supporting salt is sodium bromide or lithium bromide when the silver halide salt is silver iodide, and the supporting salt is sodium iodide or lithium iodide when the silver halide salt is silver bromide. The method of claim 11, wherein the electrolyte comprises a mixture of dimethyl sulfoxide (DMSO) and dioxolane (DOL), the volume ratio of DMSO: DOL is 55:45 to 60:40, respectively, wherein the silver halide salt is silver iodide or silver bromide And the supporting salt is lithium bromide when the silver halide salt is silver iodide, and the supporting salt is lithium iodide when the silver halide salt is silver bromide. The method of claim 11, wherein the electrolyte comprises a mixture of dimethyl sulfoxide (DMSO) and propylene carbonate (PC), the volume ratio of DMSO: PC is 60:40, the silver halide salt is silver iodide or silver bromide, silver halide The supporting salt is lithium iodide when the salt is silver iodide, and the supporting salt is lithium iodide when the silver halide salt is silver bromide.

Images