JPS6319999B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a thin film EL device that emits EL light upon application of an alternating current electric field, and in particular, by limiting the material composition of the substrate glass of the thin film EL device, it is possible to create a highly reliable thin film EL device. This relates to the element structure that has made this possible. <Summary of the invention> As a glass substrate, the volume resistivity is 10 ⁹ at 350°C.
Ω・cm or more, 10 ⁶ Ω・cm or more at 600°C, and a strain point temperature of 600°C or more, and a non-alkali type glass with an alkali component content of 0.5% by weight or less, Obtain a highly reliable thin film EL element. <Prior Art> The manufacturing process of thin film EL devices includes several high-temperature deposition, sputtering processes and high-temperature heat treatment processes, and the glass substrate is exposed to high temperatures several times before the EL device is completed. High-purity fused silica (quartz glass) is ideal as a glass substrate for EL elements because it is extremely stable even at high temperatures, but cannot be used because the manufacturing cost is extremely high. Therefore, low-alkali borosilicate glass is usually used. <Problems to be Solved by the Invention> However, alkali ions (Li ⁺ , Na ⁺ , K ⁺ ) contained in glass may be difficult to manufacture in EL devices depending on the volume resistivity (volume electrical conductivity) of the glass. Under the high temperature process of the process, it precipitates on the substrate surface and EL
Significantly deteriorates the characteristics of the element. In particular, as the substrate temperature rises during insulating film sputtering, the alkali ions precipitate on the substrate surface, and due to the interaction between the alkali ions and the current flowing through the transparent electrode (ITO) stripes due to charges incident on the substrate from the plasma, The ITO composition is altered, the electrode resistance becomes extremely high, and the characteristics of the EL device are extremely degraded. The present invention was made in view of the above problems, and its purpose is to obtain a highly reliable EL element by limiting the alkaline component content and volume resistivity of the substrate glass. That is. <Means for Solving the Problems> The thin film EL device of the present invention is a thin film consisting of a pair of electrode layers formed on a glass substrate and an electroluminescent layer sandwiched between these electrode layers in a sandwich pattern.
In the EL element, the glass substrate has a volume resistivity of 10 ⁹ Ω·cm or more at 350°C and 10 ⁶ Ω·cm at 600°C.
cm or more, and the strain point temperature is 600℃ or more,
It is also characterized by using non-alkali type glass with an alkali component content of 0.5% by weight or less. <Function> As described above, the rate of change in resistance of ITO at 600° C. is small and can be formed without altering the ITO composition, and the rate of change in resistance due to the alkali component of the glass can also be made small. Furthermore, by having a strain point temperature of 600° C. or higher, a thin film EL element with even better characteristics can be obtained. <Example> Figure 1 shows the relationship between the amount of alkali contained (weight percent) and the volume resistivity of the borosilicate glass used as the glass substrate of the EL element at each temperature. It is. In Figure 1, glass with a lower alkali content generally has a higher volume resistivity, but this relationship is reversed when the alkali content is 0% and 0.2%, and when it is 1.5% and 3%. are doing. This is a glass matrix (B ₂ O,
Component ratio of Al ₂ O ₃ , SiO ² ) and mixing ratio of added alkali (Na ₂ O, K ₂ O) (mixed alkali effect)
This is due to 350 with a content of 0.5% or less
A volume resistivity of 10 ⁹ Ω·cm or more at ℃ and a volume resistivity of 10 ⁶ Ω·cm or more at 600 ℃ can be obtained. Figure 2 shows the relationship between the volume resistivity of glass and the resistance change rate of ITO (substrate temperature 600
℃). As shown in Figure 2, the volume resistivity at 600℃ is 10 ⁶
For glasses with a resistance of Ω・cm or less, the rate of change in resistance of ITO at 600°C becomes extremely large. Moreover, FIG. 3 shows the relationship between the alkali component (Na ₂ O, K ₂ O) content of glass and the resistance change rate of ITO. The resistance change rate increases when the alkali content is 0.5% by weight or more. Furthermore, the strain point temperature of the glass substrate needs to be 600°C or higher. As mentioned above, thin film
The manufacturing process of EL devices includes several high-temperature deposition,
There are sputtering processes and high temperature heat treatment processes, and the glass substrate needs to be able to withstand these high temperatures. And the glass substrate is heated to 600℃.
The advantages of being able to use the product at higher temperatures include the following. Since the annealing temperature of the transparent electrode (ITO) can be raised, the crystallinity of the ITO film can be improved and the specific resistance can be lowered.
Also, the dielectric strength of the EL element is improved. Furthermore, it is possible to increase the annealing temperature of the light emitting layer.
It is possible to improve the crystallinity of thin film polycrystalline particles such as ZnS, and to use e.g. Mn as a luminescent center.
(active impurity element) can be diffused into the crystal lattice at an appropriate concentration, improving EL light emission characteristics. From the above, the volume resistivity is 10 ⁹ Ω at 350°C.
cm or more, 10 ⁶ Ω・cm or more at 600°C, and a strain point temperature of 600°C or more, and an alkali content of 0.5% by weight or less.
By using this type of glass as the substrate glass, it is possible to obtain an EL element with high display quality and reliability. Table 1 shows the properties of the glass according to this example.

【table】

[Table] <Effects of the Invention> As explained above, according to the present invention, an EL element with high display quality and high reliability can be obtained.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the amount of alkali contained (wt%) and the volume resistivity of the borosilicate glass used as the glass substrate of the EL element, and the volume resistivity at each temperature. is the volume resistivity of the glass and
Figure 3 shows the relationship between ITO and the resistance change rate.
FIG. 3 is a diagram showing the relationship between the alkali component content of glass and the resistance change rate of ITO.

Claims (1)

[Claims] 1. In a thin film EL device consisting of a pair of electrode layers formed on a glass substrate and an electroluminescent layer sandwiched between these electrode layers in a sandwich pattern, the glass substrate has a volume resistivity of 10 ⁹ Ω at 350°C. ·cm
The above features include using non-alkali type glass having a resistance of 10 ⁶ Ω・cm or more at 600°C, a strain point temperature of 600°C or more, and an alkali component content of 0.5% by weight or less. Thin film EL element.