JPS5825618A - Electrochromic display device - Google Patents

Abstract

PURPOSE:To provide an electrochromic display device (ECD) which prevents failure owing to thermal expansion of an electrolyte during the use of the ECD at a high temp. and which does not produce foam during the use at a room temp. or further at a low temp. with respect to the ECD which utilizes electrochemical coloring and erasing reaction. CONSTITUTION:11 is three-layered laminated thin films formed by using a sheet consisting of a hydrolyzed ethylene-vinyl acetate copolymer film of 15mu and a low gas transmission rate laminated on both surfaces thereof with low density PE (60mu) having good thermal adhesive strength and biaxially oriented PP (20mu) having a m.p. higher than that of PE and having electrolyte resistance, and adhering said sheet thermally with a heat sealer in such a way as to position the PE layer on the inner layer. A gas 12 such as gaseous nitrogen is sealed in the space formed in said thin films, whereby a reversible elastic body is constituted. When the ECD is manufactured by sealing such elastic body 11 in the inside of the ECD and injecting an electrolyte 8 through an injection port 9 for the electrolyte, no foam is produced despite exposure to an atmosphere of high and low temps. for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrochromic display device (hereinafter referred to as ECD) that utilizes an electrochemical coloring/erasing reaction.

Generally, in an ECD consisting of a display electrode, a counter electrode, and an electrolyte, when the electrolyte is injected at room temperature, when used at high temperatures, the pressure inside the ECD increases due to thermal expansion of the electrolyte, causing damage.

Therefore, considering the thermal expansion of the electrolyte, the volume ratio is 10
A method has been reported in which air bubbles of a certain size are placed inside the cell. Although this method does not cause damage when used in a high temperature atmosphere, air bubbles are always present in the cells. Moreover, when used in a low-temperature atmosphere, the electrolytic solution contracts and becomes even larger bubbles.

Note that even if air bubbles exist in the cell, there is no problem as long as they do not appear on the display electrode, but if vibrations are applied or the cell falls over, the bubbles can easily move to any position, so the absolute visibility on the display electrode side will not be affected. There is no guarantee that it will not happen. If it appears on the display pole side, the display becomes difficult to see and the product value also decreases. Placing air bubbles in the cells in this way is not the best way to prevent damage.

In view of these problems, in order to provide an ECD that prevents damage due to thermal expansion of the electrolytic solution when the ECD is used at high temperatures, and does not generate bubbles when used at room or even low temperatures, An ECD with an elastic body installed inside was considered.

An ECD in which such an elastic body is installed will be described in detail.

Page 3 Structure of Reversible Elastic Body Enclosed When an electrolytic solution is injected into an ECD at room temperature and sealed and left at a high temperature, the electrolytic solution expands as the temperature rises, and the pressure inside the ECD also begins to rise. Pressure acts equally on the surface in contact with the electrolyte. If there is an elastic body that contracts easily even at low pressures, the elastic body will contract and absorb the pressure, reducing the pressure acting on other surfaces. For example, in the case of an electrolyte solution in which lithium perchlorate is dissolved in propylene carbonate, the temperature is 2°C.
If the volume of the electrolytic solution at the time is 1, then it becomes 1.04 at 75°C. Therefore, any elastic material that contracts by 0.04 at 76° C. is sufficient.

When the electrolytic solution expands in this manner, the elastic body contracts in proportion to the rate of expansion, thereby preventing damage to the ECD. Even at low temperatures near room temperature, the elastic body expands in accordance with the volume reduction of the electrolytic solution, and unnecessary movement of the elastic body does not occur.

Therefore, if a predetermined elastic body is installed inside, unnecessary air bubbles or cavities will not be generated, and the elastic body at a predetermined position can perform the contraction/expansion action.

In such an ECD, when the material constituting the reversible elastic body is made of polyethylene or polypropylene sheet, when left at high or low temperatures for a long period of time,
Air surrounded by the sheet permeates through the sheet and dissolves in the electrolyte, resulting in a reduced pressure inside the ECD. This ECD
It was found that when a shock is applied to the electrolyte, the air dissolved in the electrolyte becomes bubbles.

An elastic body that solves these drawbacks is one in which gas is sealed in the space formed by a sheet of metal foil laminated with polyethylene film on both sides, but this elastic body has the following problems. be. That is, when a sheet formed by laminating polyethylene film on both sides is thermally bonded to form an elastic body, the outer polyethylene film is heated to a temperature higher than that required to bond the inner layer polyethylene film, and the outer layer polyethylene The film melts more than necessary. Furthermore, the outer layer polyethylene film was damaged, and as a result, the electrolytic solution came into direct contact with the At foil, causing corrosion of the At foil. As a result, ECDs containing elastic bodies that undergo changes over time such as corrosion have low reliability as display devices.

The present invention is a three-layer laminate thin film consisting of an inner layer made of a polymeric resin with good thermal adhesion, an outer layer made of a polymeric resin that has a higher melting point than the inner layer and is inert to an electrolytic solution, and an intermediate layer with a low gas permeability. Even if the ECD is left at high temperatures for a long period of time, bubbles will not be generated inside the ECD, making it possible to obtain a highly reliable ECD at a low cost. Hereinafter, the ECD of the present invention will be explained using the drawings.

The figure shows an ECD according to an embodiment of the present invention. In the figure, 1 is a glass substrate, 2 is a thin film transparent electrode, and 2' is an electrode application terminal. 3 is a display electrode on which WO3 is vapor-deposited. 4 is a light reflecting plate, 6 is a counter electrode, 6 is a counter electrode voltage application terminal, and 7 is a glass case. 8 is an electrolytic solution prepared by dissolving lithium perchlorate in propylene carbonate to a concentration of 1 M/l. 9 is the electrolyte injection hole,
After injecting the electrolytic solution 8, it is sealed with thermoplastic resin. 1
゜ is an epoxy resin for bonding the glass substrate 1 and the glass case 7, and 11 is an ethylene resin with a low gas permeability of 16μ.
A sheet laminated on both sides of a saponified vinyl acetate copolymer film with low-density polyethylene (6011), which has good thermal adhesion, and biaxially oriented polypropylene (20/7), which has a higher melting point than polyethylene and is resistant to electrolyte, is used. It is a three-layer laminate thin film that is thermally bonded with a heat sealer so that the polyethylene layer becomes the inner layer, and a gas 12 such as nitrogen gas is sealed in the space formed inside, thereby forming a reversible elastic body. There is. When creating this elastic body using a heat sealer, the outer layer has better thermal stability than conventional ones, so workability is improved.

In the ECD of this example, as a result of producing the ECD by injecting the electrolytic solution 8 at room temperature, no bubbles were generated even if the ECD was left in a high-temperature/low-temperature atmosphere for a long period of time.

In addition, as an elastic body, the inner layer is made of polyethylene, a bore, etc.
- An ECD with the same structure as in the above example was fabricated using an elastic body with a laminate structure of polyester, polypropylene for the outer layer, and vinylidene chloride, polyamide, polyvinyl alcohol, cellophane, and At foil for the intermediate layer, and was kept at high temperatures for a long period of time. Characteristics when stored in an atmosphere.

The corrosivity of the elastic body and the workability of making the elastic body were investigated.

The results are shown in the following table together with the structure of the above embodiment and the conventional structure.

(Hereinafter referred to as gold and white) 94・-ζ・ As described above, according to the 0ECD of the present invention, the workability when creating the elastic body placed in the electrolyte that contacts the display electrode and the counter electrode is good. Moreover, there is no corrosion of the intermediate layer due to damage to the thermally bonded part of the outer layer, and there is no formation of bubbles even when left in a high-temperature atmosphere, making it highly reliable.
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[Brief explanation of drawings]

The figure is a sectional view showing an electrochromic display device according to an embodiment of the present invention. 3...Display electrode, 6...Counter electrode, 8
... Electrolyte, 11 ... Three-layer laminate thin film, 12 ... Gas.

Claims (1)

[Claims] It is formed from a three-layer laminate thin film consisting of an inner layer made of a polymeric resin with good thermal adhesion, an outer layer made of a polymeric resin that has a higher melting point than the inner layer and is inert to the electrolyte, and an intermediate layer with a low gas permeability. An electrochromic display device characterized in that an elastic body is formed by sealing a gas in a space, and the elastic body is placed in an electrolytic solution in contact with a display electrode and a counter electrode.