JPH0896960A - El element - Google Patents

Abstract

PURPOSE: To provide a stabilized and practical EL element, which can prevent the insulation breakdown without lowering quality of a filter function and which has high luminance and high reliability. CONSTITUTION: In the case where thickness of an optical filter of an EL element 100 is too thick, since the self-repair impossible breakdown is easy to be generated in a light emitting layer, filter thickness is formed at 0.5-2μm so as to prevent the generation of breakdown. A combination glass 9 is formed with a layer 8' of the same optical filter. In the case where a second electrode is perfectly coated with a third insulating layer, direct influence of the optical filter to the light emitting layer is restricted, and the influence of the insulation breakdown is reduced so as to prevent the lowering of display quality. In the case of a multiple color EL element 100, an optical filter as same as the optical filter to the light emission color of the first EL element is provided on a third insulating layer 7 of the EL elements of both sides so as to form the structure that the optical filter is divided into two positions, lowering of color purity is prevented, and the insulation breakdown is restricted so as to prevent the lowering of display quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EL element (electroluminescence element, electroluminescence) used for, for example, self-luminous segment display or matrix display of instruments, or display of various information terminal devices.
Regarding

[0002]

2. Description of the Related Art There are several types of EL elements, and there is a demand for EL elements that emit red, green, and blue, which are the three primary colors of full color. A ZnS: Mn light-emitting layer in which manganese (Mn) is added to zinc sulfide (ZnS) that emits light is used and a red filter is combined to obtain a pure red color. Conventionally, as an EL element having such a configuration, for example, as described in Japanese Patent Laid-Open No. 1-315978, an optical filter that transmits or blocks a specific wavelength is used, and as a result, the light emission of the EL element is specified through the optical filter. The means of getting color is incorporated.

When the optical filter is provided on the electrode (FIG. 3), it is known that the optical filter affects the electrode, and the self-repair type destruction also occurs, which is a problem.

When a dielectric breakdown occurs at a certain point of the dielectric thin film sandwiched between the front and back electrodes, the breakdown propagates to an adjacent point and the breakdown region gradually expands (self-repair type or There is a difference between the case of the propagation mode) and the case of the breakdown remaining at only one point (called the point destruction or the self-healing mode). Especially for non-self-repair type EL
It is fatal to the element, and these modes depend on the material and thickness of the electrode, and various materials have been tried,
The definite cause of the destruction has not been clarified yet, and it has not been possible to provide a practically stable device.

Therefore, as the formation position of the optical filter, for example, as shown in Japanese Utility Model Publication No. 5-21278, indium oxide (In
An EL element 500 in which a color filter containing a dye is directly formed on the ₂ O ₃ ) electrode 58 by screen printing has been proposed (FIG. 5). The optical filter 5 is directly provided on the second electrode 58.
In the structure in which No. 9 is formed, independent colors can be selected and taken out, but as a result of aging and continuous light emission tests, it has been found that the rate of dielectric breakdown of the EL element is extremely high.

Therefore, as shown in FIG. 4, the present inventors have made it possible to prevent the optical filter from contacting the second electrode directly with the third electrode.
We have proposed a structure with an insulating layer (Japanese Patent Application No. 5-259368).
And Japanese Patent Application No. 6-87666). With the configurations of these inventions, the dielectric breakdown is considerably suppressed.

[0007]

However, if the thickness of the filter provided on the third insulating layer is increased in order to increase the color purity, the area of dielectric breakdown increases, and the breakdown point of a large area, that is, self-repair is impossible. It has been found that there is a problem that it will also be destroyed. That is, if the thickness of the optical filter is increased in order to improve the color purity, there are more regions in the light emitting layer where light emission does not occur due to dielectric breakdown even if the filter is not in direct contact with the second electrode. It became clear that there was a problem in practice.

Accordingly, an object of the present invention is to provide an EL element requiring an optical filter, which is capable of preventing dielectric breakdown without deteriorating the quality of the filter function, and having high brightness and high reliability, which is stable and practical. It is to provide a simple EL element.

[0009]

In order to solve the above problems, the structure of the present invention is such that a first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are provided on an insulating support substrate. An EL device in which at least the light emitting layer, the second insulating layer, and the second electrode are sequentially laminated, and are configured to be optically transparent,
A third insulating layer is laminated on the second electrode, and an optical filter layer for selecting light of the light emitting layer is formed on the third insulating layer.
The thickness is 0.5 μm or more and 2 μm or less, and the same optical filter layer that selects the light of the light emitting layer is also formed on the combined glass on the light extraction side.

According to the structure of the related invention, a first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are sequentially laminated on an insulating support substrate, and at least the light emitting layer and the second insulating layer are provided. In a multicolor EL element in which a single EL element composed of a layer and a second electrode which are optically transparent is combined, a third insulating layer is laminated on the second electrode, and long-wavelength light emission is formed on the lower layer. A first EL element having a color light emitting layer, and a second EL element having an upper layer having a light emitting layer having a shorter wavelength than the light emitting wavelength of the light emitting layer of the first EL element, The optical filters formed on the respective third insulating layers are both for the first EL element, and the optical filters are formed to have a film thickness of 0.5 μm or more and 2 μm or less, respectively. To do.

The present invention is also characterized in that the light emitting layer according to claim 1 or the light emitting layer of the first EL element according to claim 2 is a red-orange light emitting layer and the optical filter is a red filter. To do.

[0012] Another aspect of the invention is defined in claim 1 or 2.
The third insulating layer according to [4] has a film thickness larger than that of the second electrode in the film thickness viewed from the second insulating layer,
In addition, the region of the second electrode is completely covered with the third insulating layer.

[0013]

[Function] When the optical filter is too thick, the reason why the self-repair type destruction in the light emitting layer is likely to occur is that, due to the factor of the filter thickness, the influence of the film stress is the same as in Japanese Patent Application No. 6-87666 of the previous application. It is suspected that there are some, but the exact cause is unknown. However, in reality, the influence of the film thickness of the optical filter easily extends to the layers below the second electrode, and if the filter is too thick, the ratio of large area destruction to the total number of point destruction is large. Form with thinness.
When the film thickness of the optical filter is 0.5 μm or less, it does not substantially function as an optical filter, so 0.5 μm or more is secured. When the color purity is insufficient with the filter thickness formed in the element, the same optical filter layer is formed on the side of the combined glass, which is, so to speak, a lid.

In the case of a multicolor EL element, the third insulating layer side is opposed to each other and the combination is made. However, in the conventional case, an optical filter is provided only on one side of the EL element, and the EL element on both sides is connected to the lower side. The same optical filter for the emission color of the EL element (first EL element) coming on the side is provided. In any of the EL devices having the above structures, the third insulating layer formed on the second electrode protects the second electrode and suppresses the influence of the optical filter formed on the third insulating layer. Therefore, when the third insulating layer completely covers the second electrode, the direct influence of the optical filter on the light emitting layer is suppressed.

[0015]

By not increasing the thickness of the optical filter, the influence of dielectric breakdown on the light emitting layer is reduced and the display quality is not deteriorated. Further, by forming the same optical filter on the combination glass, the thickness of the optical filter formed directly on the element is supplemented. Even in a multi-color EL element, since thin optical filters are formed by being dispersed in two places, the color purity is not lowered, the dielectric breakdown is suppressed, and the display quality is not lowered.

[0016]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 (a) is a schematic cross-sectional view of the EL element 100, and FIG. 1 (a) shows the third insulating layer on the second electrode 6 of the EL element 100 having the same structure (A portion) as the conventional structure. The layer 7 is formed so as to completely cover the second electrode 6, and the optical filter 8 is thinly formed thereon. The optical filter 8 is formed to have a thickness of about 2 μm without exceeding 2 μm. This is because the thicker the optical filter, the greater the effect as a filter.
However, if this thickness is 0.5 μm or less, the effect as an optical filter is lost, and it is not practical. Therefore, when it is necessary to make up for the lack of color purity, the same optical filter 8 ′ is further formed on the back surface of the combined glass 9.

It will be shown below that when the thickness of the optical filter is 2 μm or less, the state of destruction of the light emitting layer is significantly reduced as compared with the conventional case. FIG. 2 shows the ratio of the point breakage occurrence rate to the total number of point breakages in terms of the optical filter film thickness with respect to the optical filter film thickness. The abscissa indicates the film thickness of the optical filter, and the ordinate indicates the percentage of point destruction that can be visually confirmed with respect to the total number of point destruction. As is clear from FIG. 2, when the optical filter film thickness exceeds 2 μm,
The large-scale destruction occurrence rate exceeds 20%, and it is noticeable on the device. Therefore, it is effective that the optical filter film thickness is 2 μm or less. When the film thickness is 0.5 μm or less, the occurrence rate of large-scale destruction becomes zero, but as the effect as an optical filter for specifying a color becomes weaker, it becomes weaker, and the actual effect disappears.

The third insulating layer 7 of the EL element 100 fills up the unevenness formed by the second insulating layer 5 and the second electrode 6, so that the surface is almost flattened, and the optical filter formed thereon is also the same. It is formed flat and has a substantially constant film thickness. Since the second electrode and the optical filter are not in direct contact with each other, the influence on the light emitting layer 4 is suppressed.

As shown in FIG. 1 (b), by combining two EL elements (first EL element) and (second EL element),
When configured as the multicolor EL element 200, the optical filter 14 (for example, a red filter) provided on both EL elements is an optical filter for the emission color of the lower EL element. A space between the two EL elements is often filled with a transparent silicone oil having a substantially equal refractive index. Optical filter 1 for each EL element
The steps of forming 4 may be exactly the same.

In the case of this multicolor EL element 200, this is equivalent to doubling the thickness of the optical filter 14. To obtain the same effect with the conventional configuration, the thickness of the optical filter should be 4 μm.
In such a structure, it is inevitable that the light emitting layer of the first EL element is overloaded and is destroyed. Therefore, as in the present invention, by providing the two EL elements with the optical filter having a thickness of 2 μm or less, the point breakage of the light emitting layer can be suppressed and the effect of maintaining the display quality can be exhibited. That is, for each EL element, the display quality can be expected to be maintained without causing self-recoverable type destruction in the light emitting layer.

As for the film thickness of the optical filters 8, 8'and 14, a thin film is formed on the surface of the third insulating layer 7 using a spin coater because the optical filter is an organic material.
An arbitrary thickness can be formed by controlling the viscosity of the material, the rotation speed of the spin coater, the maintenance time, and the like. Therefore, it is easy to make the target thickness close to 2 μm without exceeding 2 μm. In addition, the third insulating film 7 forms the second electrode 6
The optical filter can be formed without directly contacting the second electrode and the third electrode can be formed.
The surface of the insulating film 7 is flat, and the filters 8, 8'and 14
The film thickness of can be constant over almost the entire area.

[Brief description of drawings]

FIG. 1 is a schematic configuration cross-sectional view of an EL element to which the present invention is applied.

FIG. 2 is an explanatory diagram showing the dependence of a large-scale (visually observable) point breakdown occurrence rate and the optical filter film thickness on the total number of point breakdowns in the light emitting layer of the EL element.

FIG. 3 is a schematic configuration cross-sectional view of an EL element having a conventional configuration in which an optical filter is directly configured on a second electrode.

FIG. 4 is an EL device of the prior application in which a third insulating layer is provided on the second electrode.
FIG. 3 is a schematic configuration cross-sectional view of an element.

FIG. 5 is a schematic configuration cross-sectional view of an EL element having a conventional configuration in which an optical filter is provided only on a second electrode.

[Explanation of symbols]

 100 EL element 200 Multicolor EL element 300, 400, 500 EL element (conventional structure) 1, 11 Glass substrate 4, 14 Light emitting layer

Claims (4)

[Claims] 1. A first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are sequentially stacked on an insulating support substrate,
In an EL element in which at least the light emitting layer, the second insulating layer and the second electrode are optically transparent, a third insulating layer is laminated on the second electrode, An optical filter layer for selecting the light of the light emitting layer is formed thereon with a film thickness of 0.5 μm or more and 2 μm or less, and the same optical filter layer for selecting the light of the light emitting layer is formed on the combined glass on the light extraction side. An EL device characterized by the above. 2. A first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are sequentially laminated on an insulating support substrate,
In a multicolor EL element in which a single EL element in which at least the light emitting layer, the second insulating layer, and the second electrode are optically transparent is combined, a third insulating layer is provided on the second electrode. A first EL element that is laminated and has a lower layer having a long-wavelength emission color light emitting layer, and an upper layer that has a second EL element having a light emission layer having a wavelength shorter than the emission wavelength of the light emission layer of the first EL element; The optical filters formed on the third insulating layers of the EL element and the second EL element are for the first EL element, and the film thickness of the optical filter is 0.5 μm or more, and 2
EL characterized by being formed with a film thickness of less than μm
element. 3. The light emitting layer according to claim 1 or the light emitting layer of the first EL element according to claim 2, wherein the light emitting layer is a red-orange light emitting layer,
The optical filter is a red filter E
L element. 4. The third insulating layer according to claim 1 or 2,
The second insulating layer has a thickness larger than that of the second electrode, and the third insulating layer completely covers the region of the second electrode. An EL device characterized by the above.