JPH0449694B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] This invention relates to an all-solid-state electrochromic display element. [Prior art and its problems] Electrochromic display elements using transition metal oxides represented by WO ₃ have been attracting attention because of their excellent visibility. In an all-solid-state electrochromic display element, since a solid electrolyte is used as the electrolyte, the structure of the element is simpler than one using a solution electrolyte. It has advantages such as no leakage problem. An all-solid-state electrochromic display element generally has the structure shown in FIG. That is, a transparent electrode 2 formed on a glass substrate 1
An electrochromic layer 3 made of a transition metal oxide is laminated thereon. A solid electrolyte layer 4 of SiO ₂ , MgF ₂ , NiO, SiO, etc. is laminated thereon, and a counter electrode 5 is provided. As described above, the all-solid-state electrochromic display element is extremely easy to form, but as a result of repeated experiments, the inventors have found that it has the following problems. That is, since the transparent electrode and the counter electrode are formed in a laminated manner with an oxide or fluoride layer separated from each other with a thickness of at most 1 μm, short circuits between the electrodes are likely to occur. If a short circuit occurs between the electrodes, no electric field will be applied to the electrochromic layer and the solid electrolyte layer, and ion injection into the electrochromic layer will not occur, resulting in a defective product in which no electrochromic formation occurs. The causes of short circuits between electrodes are usually attributed to electrochromic layers, solid electrolyte layers, pinholes, and cracks. Therefore, in order to prevent short circuits, it is considered effective to reduce the dust in the work room that causes pinholes, specifically working in a clean room. It is necessary to form the electrolyte layer densely. However, these measures have the following problems. First of all, clean room work requires a large amount of investment in equipment, and in order to keep it functioning satisfactorily, the maintenance and management of the equipment requires a lot of effort and expense, and above all, work efficiency decreases. Furthermore, since the coloring principle of electrochromic display elements is based on the diffusion of ions between the electrochromic layer and the solid electrolyte layer, the dense formation of the electrochromic layer and the solid electrolyte layer itself results in This obstructs the diffusion of ions in the pores and causes deterioration of electrochromic properties, that is, a decrease in display contrast and a decrease in response speed. Therefore, the problem of electrode short circuits has been an extremely important constraint on the production of all-solid-state ECDs.
Furthermore, in actual elements that display character patterns, the transparent electrode portion on which the electrochromic layer is not formed occupies a large area, but this transparent electrode portion also faces the counter electrode with a solid electrolyte layer in between. , defects occurring in the solid electrolyte layer directly lead to short circuits and impede the operation of the device. As described above, the thin film laminated type all-solid-state electroluminescent element is easy to form and has a thin element thickness, and although it is an extremely promising element, it has been very difficult to actually manufacture it. [Purpose of the Invention] The present invention has been made to solve the above-mentioned drawbacks or problems of the all-solid-state electrophoretic element, and aims to provide an all-solid-state electrophoretic element with a structure that is unlikely to cause short circuits between electrodes. It is something. [Summary of the Invention] The all-solid-state electrochromic element of the present invention has an insulating layer that can easily form a dense film on a transparent electrode on which the electrochromic layer is laminated with a thickness of 500 Å or less ( A film with a thickness of 500 Å or more (hereinafter referred to as the second short-circuit prevention layer) is provided between the transparent electrode and the counter electrode on the transparent electrode on which the electrochromic layer is not laminated. This prevents short circuits between the two. The electrical insulator of the present invention may be composed of a single film having portions of different thicknesses, or may be composed of a plurality of films as shown in FIGS. 3 to 5. Generally speaking, it is easier to work if a plurality of films are formed. It is presumed that providing a short-circuit prevention layer between the transparent electrode and the counter electrode inhibits ion exchange between the electrochromic layer and the solid electrolyte and deteriorates the electrochromic properties. By using thin and high dielectric constant material,
Contrary to predictions, it has virtually no effect on electrochromic properties in practice. [Examples of the Invention] The present invention will be described in detail below based on Examples. Example 1 FIG. 2 is a diagram showing the manufacturing process of the all-solid-state electroluminescent element of the present invention, and will be explained using the drawings. A first short-circuit prevention layer 6 is deposited on the entire surface of the transparent electrode 2 formed on the glass substrate 1 and patterned into a desired pattern using a sputtering method to a thickness of 500 Å or less (FIG. 2B). . Next, a photoresist 7 is coated and exposed on the first short-circuit prevention layer, and the photoresist 7 is applied only to the portion where the electrochromic layer is to be deposited on the transparent electrode.
(Figure 2C). A second short-circuit prevention layer 8 is formed on the substrate using the sputtering method again.
is formed over the entire surface to a thickness of 500 Å or more. Afterwards,
Remove the resist (so-called lift-off process)
Then, as shown in FIG. 2D, a substrate is obtained in which an insulating film with a thickness of 500 Å or less is formed on the transparent electrode where the electrochromic layer is formed, and an insulating film with a thickness of 500 Å or more is formed on the part where the electrochromic layer is not formed. It will be done. On such a substrate, an electrochromic layer made of, for example, WO ₃ is patterned by mask evaporation or photoetching, and then a solid electrolyte layer made of ZrO ₂ and gold (Au) are formed on top of it.
The electroluminescent element according to the present invention can be obtained by vapor-depositing or sputtering a counter electrode consisting of the following. It is shown in cross section in FIG. Table 1 shows the characteristics of the all-solid-state electrochromic display element thus obtained. As a comparative example, a conventional electrochromic display element without the first and second short-circuit prevention layers was made and its characteristics were compared. As shown in the table, providing a short-circuit prevention layer makes it possible to significantly reduce short-circuits between electrodes. In this embodiment, in which the first and second short-circuit prevention layers are provided between the electrochromic layer and the solid electrolyte layer, particularly if the first short-circuit prevention layer is too thick, the electrochromic characteristics deteriorate. This may be due to the fact that the first short-circuit prevention layer inhibits the diffusion and movement of ions. The dielectric constant of the first short-circuit prevention layer shown in Table 1 is a value at a frequency of 1 MHz of a thin film formed by sputtering and having a thickness of 5000 Å. The effect of the short-circuit prevention layer is clearly recognized in all samples. From the table, it can be seen that the higher the dielectric constant of the first short-circuit prevention layer and the lower the dielectric constant of the second short-circuit prevention layer, the less influence it has on the electrochromic properties. This is because the short-circuit prevention layer has a large capacitance and can absorb current due to exchange of ions between the electrochromic layer and the electrolyte layer due to polarized charges. On the other hand, if the dielectric constant of the second short-circuit prevention layer is high, the capacitance of the element itself will be large and the coloring/fading speed will be reduced. Example 2 In the above-mentioned example, the first short-circuit prevention layer was provided on the entire surface of the transparent electrode, but the first short-circuit prevention layer was patterned to have the structure shown cross-sectionally in FIG. 4, that is, an electrochromic layer. It can also be provided only in the parts to be laminated. Although the patterning process is increased, this is the most preferable electrically. Further, as shown in FIG. 5, it is also possible to form the first short-circuit prevention layer after first forming the second short-circuit prevention layer. As explained above in the Examples, the all-solid-state electrochromic display element according to the present invention can be said to have great practical advantages because it is easy to form and has a high manufacturing yield. [Effects of the Invention] According to the present invention, since the transparent electrode and the counter electrode are insulated by the short-circuit prevention layer made of a dense and uniform thin film, an element in which electrode short-circuits are less likely to occur can be obtained. 【table】

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a conventional example of an all-solid-state electrochromic display element, Fig. 2 is a schematic diagram showing the manufacturing process of an all-solid-state electrochromic display element according to the present invention, and Figs. 3 to 5 are in accordance with the present invention. 1 is a schematic cross-sectional view of an all-solid-state electrochromic display element according to the present invention. DESCRIPTION OF SYMBOLS 1... Glass substrate, 2... Transparent electrode, 3... Electrochromic layer, 4... Solid electrolyte, 5... Counter electrode,
6... First short circuit prevention layer, 7... Photoresist pattern, 8... Second short circuit prevention layer.

Claims (1)

[Claims] 1. In an all-solid-state electrochromic display element, which is formed by laminating at least one electrochromic layer and at least one solid electrolyte layer on a substrate patterned with transparent electrodes in a predetermined shape, and on which a counter electrode is provided, a transparent Film thickness of the part where the electrochromic layer is laminated on the electrode is 500 Å
1. An all-solid-state electrochromic display element, characterized in that an electrically insulating film having a thickness of 500 Å or more in a portion where the electrochromic layer is not laminated is formed on the transparent electrode.