JPS61288396A - Thin film display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is suitable for displaying the time of an electronic watch, the speed display of a car, etc., which display characters and figures by applying voltage to electrodes in a desired pattern. The present invention relates to a thin film display device.

(Prior Art) Recently, thin film EL elements, liquid crystals, and the like have been used in display devices, and FIG. 4 shows a cross-sectional structure of a conventional thin film EL element. In FIG. 4, a transparent electrode 2 made of tin-doped indium oxide or the like, an insulating film 3 made of Y2O3 or the like, and a light-emitting film 4 made of ZS doped with about 0.5% by weight of M, etc. are disposed on a substrate glass 1. , Y2O3, etc., insulating film 5, A! A back electrode 6 made of J or the like is sequentially laminated by electron beam evaporation or sputtering.

By applying an AC voltage between the transparent electrode 2 and the back electrode 6, the portion of the light emitting film 4 sandwiched between the transparent electrode 2 and the back electrode 6 emits light. Therefore, the transparent electrode 2 or the back electrode 6
Characters and figures can be displayed by making the shape into any pattern. - As an example, the pattern of the transparent electrode 2 of a so-called 7-segment numeric display is shown in FIG. As shown in FIG. 5, since the transparent electrode 2 has a higher sheet resistance than a metal electrode, the width of the wiring pattern is made as wide as possible in order to minimize the voltage drop due to wiring resistance. There is.

Furthermore, as a display device using a liquid crystal display element having a transparent electrode, Japanese Patent Laid-Open No. 53-20794 discloses a display device shown in FIGS. 6 and 7. These are designed to make the characteristics such as the response speed and commull last of the liquid crystal uniform among each element, and in the device shown in Fig. 6,
By changing the wiring width in response to the difference in the length of the wiring 2 to each element 7, and in the device shown in FIG. 7, by changing the film thickness in the longitudinal direction of the wiring 2, the value of the wiring resistance can be made uniform. things are being done. Both of the devices shown in FIGS. 6 and 7 are the same as the example shown in FIG. 5 above in terms of the purpose of minimizing the voltage drop due to wiring resistance.

(Problems to be Solved by the Invention) The thin film constituting the thin film display element is formed by an electron beam evaporation method, a high frequency sputtering method, etc., and the film thickness is 0.
．． It is very thin, about 2 to 0.6 μm, and the thin film contains defects such as pinholes and foreign matter, and it is almost impossible to completely eliminate these defects. If there is a defect in the insulating film, a strong electric field of about 106 V/m will be applied to the insulating film, resulting in minute dielectric breakdown due to the defect. In the conventional thin film display elements mentioned above, the wiring resistance is reduced in order to suppress the voltage drop, so the current supply from the power supply continues, and the area of dielectric breakdown gradually expands, until the entire segment is insulated. There is a problem in that the display element is destroyed and cannot function as a display element.

(Objects and Structure of the Invention) The present invention has been made in view of the above points, and has the purpose of preventing the spread of thin film dielectric breakdown of thin film display elements. If the resistance value is 1 in the wiring from the power supply terminal formed on the surface to the electrode,
A resistive portion within the range of KΩ to 5KΩ was provided to control the current flowing at the time of dielectric breakdown.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 is a plan view of one embodiment of a thin film display device according to the present invention. Prior to explaining FIG. 1, three facts discovered during the experimental stage leading up to the present invention will be explained.

First, dielectric breakdown caused by a defect in the thin film begins with the energy generated by the charge accumulated between the transparent electrode and the back electrode and the current supplied from the power supply, and the expansion of the breakdown area is caused by the energy supplied from the power supply. The fact is that it depends on the energy of the current. Therefore, it can be seen that by limiting the current supplied from the power supply at the time of dielectric breakdown, it is possible to prevent the dielectric breakdown portion from expanding.

Second, chain dielectric breakdown of a thin film with an area of about 50 - can be prevented by introducing a wiring resistance of about 1KΩ to 5KΩ.

Thirdly, if current is limited at the time of dielectric breakdown, even if dielectric breakdown occurs due to a defect in the thin film, the breakdown can be limited to about 0.1 mφ or less, and it can be suppressed to a level that does not affect the display. This is something that can be done.

FIG. 3 shows the relationship between these facts, and shows the diameter of the dielectric breakdown portion and the increase in driving voltage when the wiring resistance is changed. It can be seen that when the wiring resistance is increased to 1KΩ or more, the diameter of the dielectric breakdown portion decreases rapidly. This effect increases as the resistance value of the wiring resistance increases, but it is limited to about 5KΩ because the increase in drive voltage and the heat generation in the wiring section increase. Wiring resistance is 1K
If it is about Ω to 5KΩ, the increase in drive voltage will be within an allowable range of about 10-odd volts, and the problem of heat generation will not occur.

Based on these results, a thin film display device according to the present invention is constructed as shown in FIG. FIG. 1 shows an embodiment in which the present invention is applied to a 7-segment numeric display device, in which a transparent electrode 2 is laminated on a substrate glass 1, and this transparent electrode 2 is divided into seven segments of a-Ω. ing. In order to reduce the variation in brightness within each segment 1 to a-g, that is, the difference in brightness between the part near the voltage supply point (for example 15a) and the part far away, the resistance of the transparent electrode 2 is as low as possible. It is more desirable (for example, about 10 Ω/port).
Wiring connecting to CI 14. a~14Cl is 14g, 14
b, 14c, 14e, 14f.

14a, 14. It becomes gradually shorter in the order of d. So wiring 1
4a to 14C], the widths of the wirings 14a to 14CI are made thicker in proportion to their lengths in order to make the resistance values of the wirings 14a to 14C equal to 1KΩ to 2Ω. The thinnest wiring 14a and 14d have a line width of 0.
．． It is about 1#.

FIG. 2 shows another embodiment of the thin film display device according to the present invention. Components in the figure that are the same as those in FIG. 1 are designated by the same reference numerals. In this embodiment, the wiring 148~
A meander type resistor of 168 to 1 is used as a resistance value in the middle of 14g.
6g is provided so that the combined resistance of the respective wirings 14a to 14g and the meandering resistors 16a to 16g is 1 to 2Ω. In the embodiment shown in FIG.
a to 13C] and segments a to Ω is short, it is necessary to make the width of the wirings 148 to 149 thin, and there is a risk of disconnection during etching. Therefore, in this embodiment, the wirings 148 to 14Q are made extremely thin. In order to prevent this, meander type resistors 16a to 16g were used, and the line width of the wiring was made to be the same everywhere. The functions and effects of this embodiment are the same as those of the embodiment shown in FIG. 1, so the explanation will be omitted.

(Effects of the Invention) As explained above, the present invention is configured such that a resistive portion is provided between the electrode of the thin film display element and the power supply terminal portion to the electrode to limit the current flowing at the time of dielectric breakdown. It is possible to prevent dielectric breakdown of the thin film display element from expanding.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the thin film display device according to the present invention, FIG. 2 is a plan view showing another embodiment of the thin film display device according to the present invention, and FIG. 3 is the experimental result leading to the present invention. Figure 4 is a cross-sectional structural diagram of a conventional thin film display element.
7 to 7 are plan views of conventional thin film display elements. 1...Substrate glass, 2...-Transparent electrode, 13a-13
Ω...Power supply terminal section, 148~14g...Wiring, 15
a... Voltage supply point, 16a to 16g... Meander type resistor Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] A thin film display device comprising a light-emitting film and an insulating film sandwiched between a pair of electrodes, at least one of which is transparent, and in which the light-emitting film between the electrodes emits light by applying a voltage between the pair of electrodes. A thin film display device characterized in that a resistance portion having a resistance value within a range of 1KΩ to 5KΩ is provided in wiring from a power supply terminal portion formed on the same surface to the electrode.