JP2011095406A - Electrochromic mirror - Google Patents

Abstract

An electrochromic mirror in which discoloration of an electrochromic film is suppressed even when silver is used for a reflective film is obtained.
In the electrochromic mirror 10, an electrochromic film 16, a conductive reflective film 18 containing silver, and a protective film 36 made of a metal having a work function equal to or lower than silver are provided. The diffusion of silver to 16 is suppressed, and yellowing of the electrochromic film 16 can be suppressed.
[Selection] Figure 1

Description

  The present invention relates to an electrochromic mirror that can be used for an outer mirror or an inner mirror for confirming the rear of a vehicle, and whose reflectance can be varied by applying a voltage.

  In the electrochromic mirror disclosed in Patent Document 1 below, a transparent lithium ion permeable film is provided between the electrochromic film and the reflective film. Thereby, silver contained in the reflective film can be prevented from diffusing into the electrochromic film, and coloring of the electrochromic film can be suppressed.

JP 2009-8747 A

However, although coloring of the electrochromic film can be suppressed, a transparent lithium ion permeable film generally has low conductivity, and it may be difficult to obtain sufficient coloring and decoloring properties.
In view of the above facts, an object of the present invention is to obtain an electrochromic mirror in which discoloration of an electrochromic film is suppressed while maintaining good color decoloring properties.

  The electrochromic mirror according to the first aspect of the present invention is formed on one side in the thickness direction of the electrochromic film that is colored by a reduction reaction and is transmitted through the electrochromic film. Provided on the opposite side of the electrochromic film on one side in the thickness direction of the conductive reflective film, and having a conductive reflective film that reflects light and has conductivity and is formed of silver or an alloy containing silver A protective film formed of a metal having a work function equal to or lower than silver, and a conductive film provided on one side of the protective film in the thickness direction opposite to the conductive reflective film. A conductive carbon film including activated carbon on the conductive reflective film side of the conductive film, and the protective film and the conductive film including lithium ions. The lithium ion is moved to the electrochromic film side by applying a voltage with the conductive film being positive and the conductive reflective film or the protective film being negative. And an electrolytic solution used for the reduction reaction of the membrane.

  In the electrochromic mirror according to the first aspect of the present invention, diffusion of silver ions to the electrochromic film is suppressed by the protective film formed including a metal having a work function of silver or less, and the electrochromic film Discoloration is suppressed.

  The electrochromic mirror according to the second aspect of the present invention is the electrochromic mirror according to the first aspect of the present invention, wherein the metal having a work function smaller than the silver has a Mohs hardness of 4 or less.

  In the electrochromic mirror according to the second aspect of the present invention, the durability of the conductive reflective film is improved by the protective film formed by including a metal having a Mohs hardness of 4 or less. Is suppressed.

  The electrochromic mirror according to the third aspect of the present invention is characterized in that, in the invention according to the first or second aspect, the metal having a work function smaller than that of silver is bismuth or tin.

  In the electrochromic mirror according to the third aspect of the present invention, the protective film formed by containing bismuth or tin further improves the durability of the conductive reflective film, and the whitening of the conductive reflective film is more effective. To be suppressed.

  As described above, in the electrochromic mirror according to the present invention, discoloration of the electrochromic film is suppressed.

It is sectional drawing which shows the outline of the structural example of the electrochromic mirror of this invention.

FIG. 1 is a schematic sectional view showing an example of the configuration of an electrochromic mirror according to the present invention.
As shown in FIG. 1, the electrochromic mirror 10 includes a surface side substrate 12. The front-side substrate 12 includes a transparent substrate body 14 made of glass or the like. The material constituting the substrate body 14 is not particularly limited as long as it has transparency (translucency) suitable for constituting the surface of the mirror. For example, glass (inorganic glass) and resin can be mentioned.

An electrochromic film 16 is formed on the surface of the substrate body 14 on one side in the thickness direction (the direction of arrow W in FIG. 1). The electrochromic film 16 is formed of, for example, tungsten trioxide (WO ₃ ), molybdenum trioxide (MoO ₃ ), or a mixture containing such an oxide. It is preferable that the electrochromic film 16 is formed of tungsten.
Moreover, there is no restriction | limiting in particular in the thickness of the electrochromic film | membrane 16 along the thickness direction of the substrate main body 14, For example, it can set in the range of 300 nm or more and 1000 nm or less. In the present invention, the thickness of the electrochromic film 16 is preferably 400 nm or more and 600 nm or less from the viewpoint of a decrease in reflectance.

  As a method of forming an electrochromic film on the substrate body, a method that is usually used can be applied without any particular limitation. For example, a vapor deposition method, a sputtering method, etc. can be mentioned.

A conductive reflective film 18 is formed on the surface of the electrochromic film 16 opposite to the substrate body 14. The conductive reflective film 18 is a reflective film having conductivity and gloss capable of transmitting lithium ions, and is formed of silver or an alloy containing silver. The alloy containing silver is mainly composed of silver and other metals (preferably, a metal material having high cation permeability). Examples of the metal other than silver constituting the silver-containing alloy include rhodium (Rh), ruthenium (Ru), palladium (Pd), nickel (Ni), and the like. Among them, palladium (Pd) is included. An alloy is preferred. With such an embodiment, the cation permeability of the conductive reflective film is improved, and the response speed is improved.
Moreover, there is no restriction | limiting in particular in the thickness of the electroconductive reflection film 18 along the thickness direction of the substrate main body 14, For example, it can set in the range of 30 nm or more and 200 nm or less. In the present invention, the thickness of the conductive reflective film 18 is preferably 40 nm or more and 60 nm or less from the viewpoint of conductivity and reflectance.

  The conductive reflective film can be produced (deposited) by various physical or chemical vapor deposition methods. For example, a conductive reflective film containing silver can be formed on the electrochromic film by preparing a target material containing silver and performing various sputtering using the target material.

A protective film 36 is formed on the surface of the conductive reflective film 18 opposite to the electrochromic film 16. The protective film 36 includes a metal having a work function of silver or less, but is preferably made of only a metal having a work function of silver or less. Here, the work function means the minimum energy required to extract one electron from the surface to infinity at the material surface.
By forming the protective film 36 including a metal having a work function equal to or lower than silver, diffusion into the silver electrochromic film 16 included in the conductive protective film 18 is suppressed, and the electrochromic film 16 made of silver is suppressed. Discoloration can be suppressed.

This can be considered as follows, for example. Since the electrochromic film 16 is made of a material having a work function larger than that of silver (for example, tungsten trioxide), the silver contained in the conductive reflective film 18 at the boundary between the electrochromic film 16 and the conductive reflective film 18. Atomic electrons are trapped by the material constituting the electrochromic film 16, and silver atoms are easily converted into silver ions. Since silver ions can move more easily than silver atoms, discoloration of the electrochromic film is likely to occur due to silver ions diffused into the electrochromic film 16.
On the other hand, in the present invention, the protective film 36 containing a metal having a work function of silver or less is formed on the surface of the conductive reflective film 18 opposite to the electrochromic film 16. Electrons are supplied from the metal atoms contained in the silver ions generated at the boundary between the electrochromic film 16 and the conductive reflective film 18 to suppress the ionization of silver contained in the conductive reflective film 18.

Compared with the silver work function (4.63 eV) contained in the protective film 36, the metal having a work function equal to or lower than silver is bismuth (Bi, 4.34 eV), tin (Sn, 4.42 eV), molybdenum. (Mo, 4.57 eV), antimony (Sb, 4.63 eV), gallium (Ga, 4.32 eV), zinc (Zn, 4.27 eV), chromium (Cr, 4.50 eV), niobium (Nb, 4. 33), vanadium (V, 4.30 eV), titanium (Ti, 4.33 eV), tungsten (W, 4.63 eV), cesium (Cs, 4.50 eV), boron (B, 4.45 eV), tantalum ( Ta, 4.30) and the like.
Among these, bismuth (Bi), tin (Sn), and chromium (Cr) are preferable from the viewpoint of suppressing discoloration of the electrochromic film 16.

In addition, the metal having a work function of silver or less contained in the protective film 36 in the present invention preferably has a Mohs hardness of 4 or less. By configuring the protective film 36 to include a metal having a Mohs hardness of 4 or less, white turbidity of the conductive reflective film 18 can be suppressed. This is because, for example, the protective film 36 includes a soft metal having a Mohs hardness of 4 or less, so that the conductive reflective film 18 is formed in contact with the protective film 36 by repeated use of the electrochromic mirror of the present invention. It can be considered that generation of fine cracks (cracks) can be suppressed.
Examples of metals having a work function of silver or less and a Mohs hardness of 4 or less include bismuth (Bi), tin (Sn), antimony (Sb), gallium (Ga), zinc (Zn), and cesium (Cs). Among them, bismuth (Bi) and tin (Sn) are preferable.

  The thickness of the protective film 36 is not particularly limited, and can be set, for example, in the range of 10 nm to 200 nm. In the present invention, from the viewpoint of suppressing discoloration of the electrochromic film 16 and suppressing turbidity of the conductive reflective film 18, the thickness of the protective film 36 is preferably 20 nm or more and 80 nm or less.

  The protective film 36 can be formed (deposited) by various physical or chemical vapor deposition methods, similarly to the conductive reflective film 18. For example, by preparing a target material containing a metal having a work function of silver or less (preferably a metal having a Mohs hardness of 4 or less) and performing various sputtering using the target material, the work function is less than silver. A protective film 36 containing a certain metal can be formed on the conductive reflective film 18.

The back side substrate 24 is provided on one side in the thickness direction of the front side substrate 12 having the above configuration so as to face the front side substrate 12. The back surface side substrate 24 includes a transparent substrate body 26 made of glass or the like. A conductive film 28 is formed on the other side in the thickness direction of the substrate body 26, that is, on the surface on the surface-side substrate 12 side. The conductive film 28 is made of a metal such as chromium (Cr) or nickel (Ni), indium tin oxide (In ₂ O ₃ : Sn, so-called “ITO”), tin oxide (SnO ₂ ), fluorine-doped tin oxide (SnO). ₂ : F), zinc oxide (ZnO ₂ ), and the like, and a mixture of these is preferable.
The conductive film 28 can be formed (deposited) by various physical or chemical vapor deposition methods, similarly to the conductive reflective film 18.

A conductive carbon film 30 is formed on the surface of the conductive film 28 on the surface side substrate 12 side. The carbon film 30 is formed including at least one selected from graphite, carbon black, and activated carbon, and preferably includes 50% by weight or more of activated carbon. By including activated carbon as the carbon material, the surface area of the electrode increases, the flow of electrons (current) becomes smoother, and the voltage loss is reduced. The activated carbon surface also serves as a suitable place for a catalyst that can easily generate hydrogen ions.
Furthermore, by including a carbon material such as graphite, the hydrogen ion absorption ability in the electrode layer can be improved, and the transfer of hydrogen ions from the electrochromic film to the electrolyte can be promoted when the application of voltage is released. . Furthermore, by including carbon black together with activated carbon and graphite, the degree of electrical contact between the main components (activated carbon, graphite, etc.) constituting the carbon electrode can be improved.
The carbon film 30 preferably further includes at least one synthetic resin material such as a phenol resin, a polyimide resin, and an acrylic resin as a binder.

The thickness dimension of the carbon film 30 along the thickness direction of the substrate body 26 is preferably 50 μm or more.
As the method for forming the carbon film 30, for example, several types of carbon materials (for example, activated carbon, graphite, and carbon black described above) are used as appropriate binders (for example, cellulose binders such as carboxymethyl cellulose, phenol resins, polyimides). Mixed with a resin, a synthetic resin binder such as an acrylic resin), and applied onto the back side substrate 26 on which the conductive film 28 is formed by a known method such as a doctor blade method, and an appropriate temperature (for example, 150 to The film can be formed by heating at 200 ° C.).

  A predetermined gap is formed between the front surface side substrate 12 and the back surface side substrate 24 having the above configuration, and a sealing material is provided between the outer peripheral portion of the front surface side substrate 12 and the outer peripheral portion of the back surface side substrate 24. 32 is sealed. An electrolytic solution 34 is sealed in a space surrounded by the front surface side substrate 12, the back surface side substrate 24, and the sealing material 32. The electrolytic solution 34 has a solvent formed of propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, γ-butyrolactone, dimethylformamide, or the like, or a mixture thereof. In particular, in the present invention, propylene carbonate is a solvent. It is preferable to be used as

In addition to the solvent, the electrolyte 34 is composed of lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium bis (trifluoromethanesulfonyl) imide. (LiN (SO ₂ CF ₃ ) ₂ ), lithium bis (pentafluoroethanesulfonyl) imide (LiN (SO ₂ C ₂ F ₅ ) ₂ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), etc., and mixtures thereof In particular, in the present invention, lithium perchlorate is preferably used as the electrolyte.

Furthermore, the conductive film 28 of the electrochromic mirror 10 having the above configuration is connected to a switch 42 that constitutes the circuit 40. The switch 42 is connected to a terminal connected in the ON state by a battery or the like mounted on the vehicle, and is connected to the positive electrode of a DC power supply 44 having a rated voltage of about 1.3V. The negative electrode of the DC power supply 44 is connected to the conductive reflective film 18. The terminal connected when the switch 42 is in the OFF state is connected to the conductive reflective film 18 without passing through the DC power supply 44, and in the OFF state, the conductive reflective film 18 and the conductive film 28 are short-circuited. Is done.
Although not shown, the negative electrode of the DC power supply 44 is connected to the protective film 36, and the terminal to which the switch 42 is connected in the OFF state is connected to the protective film 36 without passing through the DC power supply 44. In a state, the protective film 36 and the conductive film 28 may be short-circuited.

  In the electrochromic mirror 10 having the above configuration, the electrochromic film 16 is substantially transparent when the switch 42 is in an OFF state. Therefore, light incident from the opposite side of the substrate body 14 from the electrochromic film 16 is The light passes through the substrate body 14 and the electrochromic film 16 and is reflected by the conductive reflective film 18. Further, the light reflected by the conductive reflective film 18 passes through the electrochromic film 16 and the substrate body 14. In the electrochromic mirror according to the present invention, the light reflectance is not particularly limited, and can be, for example, about 55%.

On the other hand, when the switch 42 is switched to the ON state, the electrons (e ⁻ ) that have moved through the circuit 40 toward the conductive reflective film 18 enter the electrochromic film 16, and at the same time, the lithium ions ( Li ⁺ ) penetrates the protective film 36 and the conductive reflective film 18 and enters the electrochromic film 16. As a result, a reduction reaction of the following formula 1 occurs in the electrochromic film 16, and blue Li _x WO ₃ called so-called tungsten bronze is formed in the electrochromic film 16.
Li ⁺ + e ⁻ + WO ₃ → Li _x WO ₃ (Formula 1)
As a result of the electrochromic film 16 being colored in blue in this way, the reflectivity, which was about 55 percent before the electrochromic film 16 was colored, is reduced to, for example, about 7 percent.

Furthermore, when the above reduction reaction occurs, electrons (e ⁻ ) move from the carbon constituting the carbon film 30 to the DC power supply 44 side, whereby negative ions derived from the salt constituting the electrolyte, for example, Then, negative ions (ClO ₄ ⁻ ) of lithium perchlorate move to the carbon film 30 side. As a result, a compensation reaction like the following formula 2 occurs with respect to the above reduction reaction.
ClO ₄ ⁻ + C−e ⁻ → C ⁺ · ClO ₄ ⁻ (Formula 2)

Further, the carbon film 30 contains not only activated carbon but also graphite and carbon ink, whereby the carbon film 30 is imparted with sufficient conductivity and the reaction in the carbon film 30 can be accelerated.
Furthermore, the provision of the carbon film 30 can reduce the voltage applied when coloring the electrochromic film 16. For this reason, when the switch 42 is turned off and the conductive reflective film 18 and the conductive film 28 are short-circuited, a reaction opposite to the above formulas 1 and 2 occurs, and the electrochromic film 16 is quickly discolored. The

  When the electrochromic mirror 10 as described above is used for a mirror body such as an inner mirror (room mirror) or an outer mirror (door mirror or fender mirror) for rear confirmation in a vehicle, for example, the switch 42 is maintained in an OFF state during the daytime. When the vehicle behind is turning on the headlight at night or the like, the switch 42 is turned on to color the electrochromic film 16 and reduce the reflectance. Thereby, the reflected light of a headlight can be reduced and dazzling falls.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
An electrochromic film was formed on an 85 × 114 mm glass substrate as follows. That is, using a commercially available vacuum deposition apparatus, tungsten trioxide (WO ₃ ) was deposited, and an electrochromic film made of tungsten trioxide having a thickness of 500 nm was formed on a glass substrate.
Next, a conductive light reflecting film was formed in contact with the obtained electrochromic film. That is, in the formation of the electrochromic film, a conductive reflective film having a thickness of 50 nm was formed on the electrochromic film using silver (Ag) instead of tungsten trioxide (WO ₃ ).
Next, a protective film was formed in contact with the obtained conductive reflective film. That is, in the formation of the conductive reflective film, a protective film made of tin having a thickness of 50 nm was formed on the conductive reflective film using tin (Sn) instead of silver.

On the other hand, the same glass substrate as the front surface side substrate was also adopted as the back side substrate, and a conductive film made of chromium (Cr) having a thickness of 200 nm was formed on the surface by vapor deposition in the same manner as described above.
Next, a carbon electrode film was formed on the conductive film made of chromium. That is, a carbon material composed of 10% by mass of graphite, 10% by mass of carbon black, 70% by mass of activated carbon and 10% by mass of polyimide binder is mixed with an appropriate amount of water, and the obtained mixed material is applied to the substrate surface by a doctor blade method. did. Then, it heated at 180 degreeC for 1 hour, and formed the carbon electrode film about 50 micrometers thick.

A sealing material made of an epoxy resin was applied to the peripheral portion of the surface of the carbon electrode film thus obtained, and an electrolytic solution was applied to the inside to a thickness of about 0.2 mm. As the electrolytic solution according to this example, a solution obtained by adding lithium perchlorate to propylene carbonate, which is an aprotic solvent, to a concentration of 100 mM was used.
Subsequently, the front side surface board | substrate provided with an electrochromic film | membrane, an electroconductive reflection film, and a protective film was piled up, and the electrochromic mirror which has a structure shown in FIG. 1 was obtained by sealing with the said sealing material.

<Examples 2-7, Comparative Examples 1-2>
In Example 1, an electrochromic mirror was obtained in the same manner as in Example 1 except that the metal constituting the conductive reflective film and the metal constituting the protective film were changed as shown in Table 1 below.

<Example 8>
In Example 1, a conductive reflective film is formed by sputtering using Ag37 (manufactured by Mitsubishi Materials Corporation, silver alloy No37) as a metal constituting the conductive reflective film, and a protective film is formed using chromium (Cr). Except that, an electrochromic mirror was obtained in the same manner as in Example 1.

<Comparative Example 3>
In Example 1, the conductive reflective film was formed by sputtering using AgBi (Bi-added silver alloy) as a metal constituting the conductive reflective film, and the protective film was not formed. Thus, an electrochromic mirror was obtained.

<Evaluation>
(Discoloration and cloudiness)
About the obtained electrochromic mirror, discoloration and white turbidity of the electrochromic film were evaluated as follows. The results are shown in Table 1.
Connect the 1.3V DC power supply so that the electroreflective film of the obtained electrochromic mirror is the negative electrode and the conductive film is the positive electrode, and repeat the switch ON / OFF 100 times. The film and the conductive reflective film were observed and evaluated according to the following evaluation criteria.
~Evaluation criteria~
○: Discoloration of the electrochromic film was not observed, and white turbidity of the conductive reflective film was not observed after 24 hours.
Δ: Discoloration of the electrochromic film was not observed, but white turbidity of the conductive reflective film was observed after 24 hours.
X: Discoloration of the electrochromic film was observed, and white turbidity of the conductive reflective film was also observed.

(Reflectance)
The reflectance of the obtained electrochromic mirror when no voltage was applied (DAY reflectance (%)) and the reflectance when voltage was applied (NIGHT reflectance (%)) were measured using a spectral reflectometer. The results are shown in Table 1.

  It can be seen from Table 1 that discoloration can be suppressed by forming a protective film using a metal having a work function of silver or less. Furthermore, it turns out that the cloudiness of a mirror can also be suppressed by comprising a protective film using the metal whose Mohs hardness is less than 4.

DESCRIPTION OF SYMBOLS 10 Electrochromic mirror 16 Electrochromic film 18 Conductive reflective film 28 Conductive film 30 Carbon film 34 Electrolyte solution 36 Protective film

Claims (3)

An electrochromic film colored by a reduction reaction;
A conductive reflective film formed on one side in the thickness direction of the electrochromic film, reflecting light transmitted through the electrochromic film and having conductivity, and formed of silver or an alloy containing silver;
A protective film that is provided on one side in the thickness direction of the conductive reflective film on the side opposite to the electrochromic film and that includes a metal having a work function of silver or less;
A conductive film having conductivity provided on one side in the thickness direction of the protective film on the side opposite to the conductive reflective film;
A carbon film having conductivity formed including activated carbon on the conductive reflective film side of the conductive film;
Lithium ions are included and enclosed between the protective film and the conductive film, the conductive film is positive, and the conductive reflective film or the protective film is negative and voltage is applied to apply the voltage. An electrolytic solution in which lithium ions move to the electrochromic film side and subjected to a reduction reaction of the electrochromic film;
Electrochromic mirror equipped with.   The electrochromic mirror according to claim 1, wherein the metal having a work function smaller than silver has a Mohs hardness of 4 or less.   The electrochromic mirror according to claim 1 or 2, wherein the metal having a work function smaller than silver is bismuth or tin.

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