JPS6320977Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is a so-called electrochromic (hereinafter referred to as EC) that exhibits reversible color development and disappearance upon application of voltage.
It is related to elements, and more specifically, transmission type
The present invention relates to a reflective EC display element characterized in that a background plate is arranged on the back side of the EC element.

In recent years, with the spread of microprocessors, the need for display elements has increased.

Among various display elements, liquid crystal display elements are rapidly growing in fields such as calculators and watches because of their characteristics such as low voltage drive and low power consumption.

EC devices have advantages over liquid crystal devices, such as no viewing angle dependence, bright display, and memory function, and are being considered for use in numeric display devices, light valves, optical shutters, etc.

Already, EC elements are known that have a structure in which a thin film layer of an electrochromic substance of a transition metal oxide formed on a display electrode is sandwiched between the display electrode and a counter electrode via an electrolyte. When a negative voltage is applied to the transition metal oxide side, M ⁺ + WO ₃ + e → MWO ₃ (colorless and transparent) (colored) cation M ⁺ and electrons are injected into WO ₃ to form a colored state as shown in the following formula. The display is performed using the .

Conventionally, in this type of EC element, due to the element configuration,
Symmetric and asymmetric types have been proposed. As shown in Fig. 1, the symmetrical type has a transparent substrate 1, 1' having a transparent conductive display electrode and counter electrodes 2, 2', and EC thin films 3, 3' of the same type formed on the electrodes 2, 2'. The electrolyte 5 is sandwiched between the pair of substrates, and the periphery is sealed with a sealing member 6. On the other hand, the asymmetric type uses an inert electrode material such as metal or carbon for the counter electrode. Currently, it is considered that an inert electrode is insufficient from the viewpoint of the life of the device, and a symmetrical structure is generally adopted.
In this case, since the same type of EC thin film, such as a tungsten oxide thin film, is formed on both the display electrode and the counter electrode, the tungsten oxide on the counter electrode remains colored even when no display is performed. Therefore, a masking material 4 is required to hide this from viewers. Furthermore, it has been impossible to obtain a transmission type element due to such a configuration.

The present inventors previously proposed that in the symmetrical element,
We proposed a transmission type device by improving the EC thin film formed on the counter electrode.

The content is that in a symmetric EC element, the EC thin film on the display electrode changes optical properties in the ion and electron absorbing state when a voltage is applied, including the visible region, and in the emitting state, the region does not include the visible region. ,
The EC thin film on the counter electrode is characterized by being a crystalline tungsten oxide thin film in which the main wavelength range in which the optical properties change due to this state change does not substantially include the visible range.

Thus, in the non-display state when ions and electrons are injected into the EC thin film on the counter electrode by application of a reverse voltage, there is no substantial change in the visible region, resulting in a transparent state.

That is, a so-called transmissive element is realized which is in a transmissive state when not displaying information and is colored when displaying information.

By adopting the configuration described above, the transmission type element eliminates the need for a masking material to be placed inside the EC element, simplifying the structure and facilitating the process. Moreover, since it is a transmissive element, it has the advantage that it can be illuminated from behind.

The present invention relates to a reflective EC display element characterized in that a background plate is arranged on the back side of such a transmissive element.

As the background plate, a colored plate having an absorption spectrum complementary to that of the EC thin film, a scattering reflector plate that scatters and reflects light incident from the front surface of the element, or a scattering colored plate is used.

Conventional EC elements were displayed using a masking material provided inside as a background, so the masking material must be a porous material that allows the electrolyte to pass through, and be inert to the electrolyte. , do not elute harmful impurity ions, withstand the temperature of device fabrication, color tone,
The range of materials that can be selected is narrow due to factors such as preferable reflectance, pattern, etc., and the masking materials that are actually used include porous paper such as filter paper, cloth,
Although porous ceramic plates and the like are available, they are unsatisfactory in appearance as background plates.

In the reflective EC display element of the present invention, the above-mentioned background plate is placed outside the element, so there are almost no restrictions mentioned above, and the range of choices is expanded, the appearance can be improved, and the degree of freedom in design is increased. benefits will be generated.

Hereinafter, the reflective electrochromic device according to the present invention will be explained in detail with reference to the drawings.

Figure 2 shows a transmission type EC element according to the present invention.
A display EC thin film 23 is formed on the electrode 22 of a transparent substrate 21 having a transparent conductive electrode 22. The EC thin film 23 is an amorphous tungsten oxide film formed by a conventional method such as an EB method. Transparent substrate 2
A transparent conductive counter electrode 22' is formed on the counter electrode 1', and electrons that cause EC characteristics reversibly enter and exit the counter electrode 22', but oxidation that does not cause optical changes in the visible range is formed on the counter electrode 22'. An EC thin film 23' made of a crystalline tungsten thin film is formed. The EC thin film 23' has the following properties.

(1) It has a porous structure that allows ions to diffuse by controlling the potential.

(2) It has such mobility that electrons that compensate for the charge of the diffused ions drift and reach the vicinity of the ions.

(3) The mother lattice, ions, and electrons interact to form a color center.

(4) It has crystallinity such that electrons trapped in the color center can be delocalized to a considerable degree;
Color centers have no absorption in the visible range.

A substrate 21 on which the pair of EC thin films described above are formed,
A transparent electrolyte 25 is held between 21' and the periphery thereof is sealed with a sealing member 26. In the EC element of the present invention, the masking material 4 required in the conventional element shown in FIG. 1 is unnecessary. 27 is a colored plate or a reflection plate as a background plate, and is arranged on the back side of the element. The material No. 27 is selected from the viewpoint of increasing the contrast of the EC element, and therefore a colored plate exhibiting an absorption spectrum complementary to the display color or a reflecting plate that scatters light incident from the front of the cell is used.

Since such a colored plate or reflective plate is placed outside the element, it is not subject to restrictions on the material and can be processed into any color tone or pattern, compared to conventional masking materials for EC elements.

In this way, by arranging an appropriate background plate, it is possible to obtain effects such as increasing the contrast of the display, increasing the brightness of the display, and adding diversity to the design by the background plate.

Example: 2×10 ^-5 Torr was deposited on a glass substrate with a transparent conductive film using a vacuum evaporation system equipped with an ordinary electron gun.
A tungsten oxide film was formed to a thickness of 0.5μ, and this was used as a display electrode plate. Also, by the same method,
Tungsten oxide was formed to a thickness of about 1.0 μm at 6×10 ⁻⁴ Torr, and then crystallized by heat treatment at 390° C. for 20 minutes in air, and this was used as a counter electrode plate.

A pair of electrode plates made in this way are placed facing each other, and a spacer is placed around the periphery for sealing. Then, an electrolyte containing LiClO ₄ dissolved in propylene carbonate at a concentration of 0.5M is injected through a predetermined injection hole. The injection hole was sealed and the device was completed. In this state, when a voltage of 3.5V was applied to the device with the display electrode negative, the amorphous tungsten oxide film on the display electrode turned blue. Next, when a voltage of 1.5 V was applied with the display electrode positive, the blue color on the display electrode disappeared, and there was almost no macroscopic change in the crystalline thin film of tungsten oxide on the counter electrode. further after this
Switching was repeated at 1.5V, but the tungsten oxide on the display electrode simply changed color and faded, and the tungsten oxide on the counter electrode showed almost no change, resulting in a transmissive element. When displaying was performed using a scatter-reflective golden vinyl cloth with a satin pattern as a background plate, blue letters appeared on a shiny golden background, and the appearance was evaluated as good.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional symmetrical EC element, Figure 2
The figure is a cross-sectional view of the transmission type EC element according to the present invention. 1, 1', 21, 21' are transparent substrates, 2, 2',
22, 22' are transparent conductive electrodes, 3, 3', 23,
23' is an EC thin film, 4 is a masking material, 5 and 25 are electrolytes, 6 and 26 are sealing members, and 27 is a background plate.

Claims (1)

[Claims for Utility Model Registration] 1. A transparent substrate having a pair of transparent conductive electrodes arranged opposite to each other, and one of the transparent substrates formed on the transparent conductive electrodes having optical properties in a state in which ions and electrons are injected by applying a voltage. Oxidation is one in which the region of change in the state includes the visible region and substantially excludes the visible region in the emitted state, and the other is oxidation in which the main wavelength region of the optical property change caused by this state change does not substantially include the visible region. A transmission type electrochromic device consisting of a pair of electrochromic thin films that are crystalline tungsten thin films, an electrolyte containing ions that change the optical properties of the electrochromic thin film, and a sealing member that encapsulates the electrolyte. A reflective electrochromic display element characterized by having a background plate placed on the back. 2. The reflective electrochromic display element according to claim 1, wherein the background plate is a colored plate having an absorption spectrum complementary to that of the electrochromic thin film. 3. The reflective electrochromic display element according to claim 1, wherein the background plate is a scattering reflector.