JPH0143934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvement of a thin film type electrochromic display device (hereinafter abbreviated as ECD).
In particular, it relates to ECDs in which the proton donor layer is made of an appropriate material and layer composition to improve memory, appearance and coloring characteristics, and further reduce current consumption.

ECDs can be broadly divided into those whose basic element, electrochemical coloring substance (hereinafter referred to as EC layer), is an inorganic substance and those whose basic element is an organic substance.
The EC layer is made of inorganic material, which is another basic element, the proton or cation donor layer (hereinafter referred to as
(abbreviated as PS layer) can be divided into solid and liquid types. If the EC layer is made of an organic substance such as biologen or the PS layer is a liquid, the manufacturing cost of the display element is extremely high due to the complicated structure of the display element and the complicated manufacturing process. Therefore, it was inferior to other display elements such as LED and liquid crystal. EC layer and PS
A structure in which both layers are solid can be manufactured by a single process called vapor deposition or by a process called printing, which has a significant cost advantage.

The reason why all-solid-state ECDs could not be put to practical use in the past was due to their short lifespan and poor color development characteristics, including color density and response. The present invention significantly improves on these drawbacks, as detailed below.

The present invention is an electrochromic display having a plurality of electrodes, an electrochemical coloring layer, and a proton donor layer, characterized in that at least one solid proton donor layer containing boron oxide is provided as the proton donor layer. The present invention relates to a display element. In the description of the present invention, the proton donor layer refers to a layer that releases protons upon application of voltage and has the role of reducing and coloring the EC layer.

In addition, the EC layer is a layer that undergoes reduction and discoloration by protons, such as tungsten oxide (WO ₃ ),
Metal oxides include molybdenum oxide (MoO ₃ ), vanadium oxide (V ₂ O ₅ ), and titanium oxide. However, in the present invention, the material of the EC layer is not limited to these.

Conventional all-solid-state ECDs have slow color development speed1
It took several seconds to several tens of seconds to apply a voltage of ~2V.
It also had a short lifespan, with the color density decreasing due to repeated color development and fading, and the lifespan could be repeated no more than ¹⁰⁴ times until the initial color density was reduced to 1/2. In addition, all-solid-state ECDs generate gas through repetition,
This has been a major drawback since it often damages the element structure. In order to prevent gas generation, it is necessary to lower the applied voltage as much as possible, but this brings about a trade-off in that the speed of color development and the density of color development decrease.

The material for the proton donor layer is generally preferably a solid acid because of its role in injecting protons into the EC layer when a voltage is applied.Chromium oxide (chromium oxide) is a relatively effective proton donor material for all-solid-state ECDs. Cr ₂ O ₃ ), tantalum oxide (Ta ₂ O ₅ ),
Examples include nickel oxide (NiO). However, although ECDs that use these substances as proton donor layers develop color at low voltages (1.3 to 2 V), they suffer from significant changes over time (the coloring properties deteriorate even if left unattended) and have not been put into practical use. .

The present invention involves forming a mixed film of boron oxide (B ₂ O ₃ ) in the PS layer, and the addition of B ₂ O ₃ brings about a significant improvement in the coloring characteristics (coloring density, responsiveness, change over time) of display elements. It is.

However, boron oxide is actually used in film formation.
It is thought that water molecules are adsorbed as BOx or some boric acid without taking the form of B ₂ O ₃ , and that it combines with other coexisting solid acids to form a complex structure. The type is not particularly limited. Note that solid acids are solids that act as proton donors or electron acceptors, such as silicon oxide, aluminum oxide, vanadium oxide, titanium oxide, antimony oxide, tin oxide, chromium oxide, niobium oxide, tantalum oxide, Metal oxides such as zirconium oxide, tungsten oxide, and molybdenum oxide, cation exchange resins, solidified acids made by adhering ordinary acids to carriers, and the above containing some water as crystal water or structured water. , or a mixture thereof, and the present invention is not limited to these. The present invention provides solid acid with B ₂ O ₃
However, a layer of B ₂ O ₃ alone has a weak film strength and peels off after vapor deposition. In order to maintain the membrane state, it is preferable to use a substance with adhesive strength as the carrier, and further, in order to cause proton extraction, it is preferable to use a substance in the range of solid acids. Further, the present invention does not specify the content of B ₂ O ₃ or the position of the proton donor layer containing B ₂ O ₃ , and furthermore, the content ratio of B ₂ O ₃ is changed from the EC layer to the proton donor layer. The concentration of B 2 O 3 may be changed sequentially within the range of the layers, or the concentration of B ₂ O ₃ may be particularly high near the interface with the electrode in contact with the proton donor layer, which is called the counter electrode.
Further, some kind of intermediate layer may be provided at the interface between the EC layer and the proton donor layer, and the present invention
There are no particular limitations on the format or structure in which B ₂ O ₃ is contained.

By including B ₂ O ₃ in the proton donor layer, the applied voltage required for color development can be lowered (0.8~
1.5V), increases color development speed (0.1 to 1 second), and enables extremely long-life ECD. As described above, the present invention provides an epoch-making display element compared to conventional all-solid-state electrochromic displays.

Next, the present invention will be explained in detail with reference to examples.

<Example 1> In the example shown in FIG. 1, a transparent electrode 2 of indium oxide containing 5% tin oxide is formed on a glass substrate 1, and WO is applied on this in a vacuum of 7×10 ^-5 torr. ₃
The EC layer 3 was formed to a thickness of 4000 Å. Furthermore, this
Cr ₂ O ₃ layer 4 on the EC layer 3 at a vacuum level of 3×10 ^-4 torr
was deposited to a thickness of 2000 Å, then (SiO ₂ + B ₂ O ₃ )
Layer 5 was co-deposited containing 30% by weight of B ₂ O ₃ in a vacuum of 3×10 ^-4 torr to have a thickness of 1000 Å.
On top of this, Au is laminated to a thickness of 150 Å, and the counter electrode 6
And so. When a voltage of 1.3V was applied to this display element with the counter electrode 6 as the positive electrode, the concentration was 0.4 after 1 second.
The color density was obtained. When color development and decolorization were repeated 10 ² times, a color density of 0.6 was obtained after 0.5 seconds, and there was almost no deterioration even after 10 ⁶ times. The leakage current was extremely low at 0.4 mA/cm ² .

<Example 2> In the example shown in FIG.
and Cr ₂ O ₃ layer 4 was provided, and then oxygen gas saturated with moisture was introduced into the vapor deposition machine with a vacuum level of 2×10 ^-6 torr, and the pressure was adjusted to 3×10 ^-4 torr to form B ₂ O ₃ . A (NiO+B ₂ O ₃ ) layer 7 containing approximately 8% by weight was laminated to a thickness of 800 Å. Thereafter, a counter electrode 6 was formed from indium oxide containing 5% tin oxide using a low-temperature sputtering device so as not to increase the substrate temperature. Furthermore, silicon dioxide was laminated as an antireflection film 8 to increase the transmittance of visible light. When a voltage of 1.3 V was applied to this display element using the counter electrode 6 as a positive electrode, a color density of 0.7 was obtained in 0.1 seconds, and almost no decrease in density was observed even after 10 ⁶ times.

[Brief explanation of drawings]

1 and 2 are partial cross-sectional views showing an embodiment of an all-solid-state electrochromic display element of the present invention. 1...Glass substrate, 2...Transparent electrode, 3...EC layer,
4 _{... 3 Cr2O} layers, 5...( _SiO2 + _B2O3 ) layers, 11...
(NiO+B ₂ O ₃ ) layer, 6... counter electrode, 7... (NiO+
B ₂ O ₃ ) layer, 8... antireflection film.

Claims (1)

[Claims] 1. An electrochromic display element having an electrochemical coloring layer and a proton donor layer, characterized in that the proton donor layer is provided with at least one solid proton donor layer containing boron oxide. .