JPH06132083A - Thin film el display device and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve electric breakdown performance of a thin film EL display device. CONSTITUTION:A plurality of band-shaped first electrodes 2, consisting of metal and ITO, are formed on a glass substrate 1, and in accordance with a kind of the first electrode in use, an insulator 3, consisting of SiO2, Ta2O5, alumina to cover each end face part 2a of this first electrode, is formed. The first insulation layer 4, formed of an SiO2 layer 4a and an Si3N4 layer 4b to cover the insulator 3 and the first electrode 2, is formed, to successively laminate an EL emission layer 5 of ZnS:Mn film doped with Mn serving as the emission center to a base unit material ZnS and the second insulation layer 6, formed of an Si3N4 film 6a and an Al2O3 film 6b, to this first insulation layer 4. Further, a plurality of band-shaped second electrodes 7, consisting of ITO having permeability, are formed in a direction orthogonal to the first electrode 2 in a surface of the second insulation layer 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film EL display device and a method for manufacturing the same for the purpose of improving dielectric breakdown performance.

[0002]

2. Description of the Related Art FIG. 9 is a sectional view showing the structure of a conventional thin film EL display device 91. This thin film EL display device 91 is a color E using an organic color filter, for example.
The EL (electroluminescent) light-emitting layer 85 and the first insulating layer 84 sandwiching the EL light-emitting layer 85 are formed on the glass substrate 81 and have a so-called inverted structure suitable for an L display.
And a second insulating layer 86, and a first electrode 82 and a second electrode 87 provided outside the both insulating layers 84 and 86.

The EL light emitting layer 85 has a thickness of, for example, about 1 μm obtained by doping the base material ZnS with Mn as an emission center.
ZnS: Mn film. The first insulating layer 84 is, for example, a SiO ₂ film 84a having a thickness of 30 to 80 nm and a thickness of 200.
Consisting of the Si ₃ N ₄ film 84b of to 300 nm. The second insulating layer 86 is made of, for example, S having a thickness of 100 to 200 nm.
i ₃ N ₄ film 86a and Al ₂ O ₃ film 86 having a thickness of 30 to 50 nm
b and. Further, the first electrode 82 and the second electrode 87 are made of a metal Mo film and an ITO (tin-doped indium oxide) film, respectively, and are called a back electrode and a transparent electrode.

FIG. 10 shows a conventional thin film EL display device 9.
FIG. 3 is a process diagram showing a production procedure of 1. First, in step c1, a metal Mo film is formed on the glass substrate 81 by a sputter deposition method or the like, and a plurality of parallel strip-shaped first electrodes 82 are formed by a photolithography method or the like. Next, step c2
In the SiO ₂ film 8 by the reactive sputtering method or the like.
4a, the Si ₃ N ₄ film 84b is formed to form the first insulating layer 84. Next, in step c3, the EL light emitting layer 85 is formed by an electron beam vapor deposition method, a CVD method, or the like, and then surface treatment is performed by heat treatment, if necessary. Further, in step c4, a Si ₃ N ₄ film 86a and an Al ₂ O ₃ film 86b are formed by a reactive sputtering method or the like to form a second insulating layer 86, and in step c5, ITO is formed by a sputter deposition method or the like. Then, a plurality of parallel strip-shaped second electrodes 87 are formed in a direction orthogonal to the first electrodes 82 by a photolithography method or the like. Next, silicone resin 8
8 and the like are applied and cured by heating and drying.

Subsequently, a filter material in which a green or red pigment is dispersed in a photosensitive resin is applied on the seal glass 90, and then processed into a mosaic shape by a photolithography method or the like. This process is repeated for each of the green and red filter films to form the color filter 89, and finally the glass substrate 81 and the seal glass 90 are bonded together.

By applying a predetermined AC voltage to the first electrode 82 and the second electrode 87 of the thin-film EL display device 91 manufactured as described above, the first electrode 82 and the second electrode 87 are separated from each other.
The EL light emitting layer 85 which is sandwiched between the electrodes 87 and constitutes one picture element emits light, thereby displaying.

[0007]

In the so-called inverted structure element in which the first electrode 82 is made of metal as described above, the end shape of the electrode becomes acute, and the step 84c of the electrode end step 84c formed by the first insulating layer 54 is formed. The step coverage performance is deteriorated, and the local electric field concentration is also combined, so that the dielectric breakdown performance in this portion is deteriorated, and the pixel breakdown and the wire breakage are likely to occur.

Further, even if the first electrode 82 is a transparent electrode made of ITO having excellent transmittance and specific resistance, the conventional thin film EL display device 91 has the following problems. When the thin film EL display device 91 in which the first electrode 82 is a transparent electrode is used for a large-sized panel, the influence of the wiring resistance of ITO itself cannot be ignored, and the unevenness of the luminance can be caused by the length of the wiring. Therefore, measures are taken to increase the film thickness of the transparent electrode 82 to reduce the wiring resistance, but the step coverage performance of the electrode end step portion 84c of the first insulating layer 84 is further deteriorated, and the same problem as described above occurs. .

An object of the present invention is to provide a thin film EL display device having improved step coverage performance and dielectric breakdown performance of the first insulating layer, and a more reliable thin film EL display device, and a manufacturing method thereof.

[0010]

According to the present invention, a plurality of strip-shaped first electrodes, a first insulating layer, an EL light emitting layer, a second insulating layer, and a plurality of strip-shaped first electrodes which are orthogonal to the first electrode are formed on a substrate. In the thin film EL display device including two electrodes sequentially stacked, the first
The thin film EL display device is characterized in that an insulator is formed at a first electrode end step portion between an electrode and the first insulating layer.

The present invention also provides a plurality of strip-shaped first members on a substrate.
Forming an electrode, forming an insulator covering each end of the first electrode, the insulator and the first
Forming a first insulating layer covering the electrodes, forming an EL light emitting layer over substantially the entire surface of the first insulating layer,
Forming a second insulating layer over substantially the entire surface of the EL light emitting layer; and forming a plurality of translucent strip-shaped second electrodes on the surface of the second insulating layer in a direction orthogonal to the first electrode. And a step of manufacturing the thin film EL display device.

[0012]

According to the present invention, a plurality of strip-shaped first electrodes, an insulator, a first insulating layer, an EL light emitting layer, a second insulating layer and a second electrode are sequentially laminated on a substrate to form a double insulating structure. Of the thin film EL display device.

After a film is formed on the substrate by, for example, a sputter deposition method, a plurality of parallel strip-shaped first electrodes are formed by, for example, a photolithography method or a dry etching method, and each of the first electrodes is formed. The insulator is formed so as to cover the end portion of. A first insulating layer is formed by, for example, a sputter deposition method so as to cover the insulator and the first electrode, and for example, an electron beam vapor deposition method or a chemical vapor deposition method is formed over almost the entire surface of the first insulating layer. Thus, the EL light emitting layer is formed. Further, a second insulating layer is formed on almost the entire surface of the EL light emitting layer in the same manner as the method for forming the first insulating layer. Further, in the same manner as the method of forming the first electrode, the plurality of band-shaped second electrodes having a light-transmitting property are formed in the direction orthogonal to the first electrode on the surface of the second insulating layer.

Therefore, the step coverage of the step portion of the first electrode end is improved and the electric field applied to each end portion of the first electrode covered with the insulator is covered without changing the characteristics relating to light emission. It can be made lower than that of an unexposed picture element surface, and the dielectric breakdown performance can be improved. Further, since the light emission start voltage is different between the picture element surface covered with the insulator and the picture element surface not covered with the insulator, a thin film EL display device suitable for gradation display can be manufactured. Further, the light emission starting voltage itself can be changed by changing the material (dielectric constant ε is different) or the film thickness of the insulator.

[0015]

1 is a sectional view showing the structure of a thin film EL display device 11 according to a first embodiment of the present invention. This thin film EL display device 11 is a color EL device using an organic color filter.
An EL light emitting layer 5 having a so-called inversion structure suitable for a display, a first insulating layer 4 and a second insulating layer 6 sandwiching the EL light emitting layer 5, and both insulating layers 4, 4.
6, and a first electrode 2 and a second electrode 7 provided outside. Further, an insulator 3 is formed between the first electrodes 2 so as to cover the step portion 2a of the first electrode 2 in order to protect the first electrode end step portion 2a.

Reference numerals from w1 to w5 shown in FIG. 1 are reference numerals indicating respective dimensions. As concrete numerical values, w1 is 220 μm and w2 is 180 to 190.
μm, w3 is 15 to 20 μm, w4 is 110 to 120 μ
m and w5 are 80 μm.

The EL light emitting layer 5 is formed of, for example, the base material Z.
It is composed of a ZnS: Mn film having a thickness of about 1 μm, in which nS is doped with Mn as an emission center. The insulator 3 has a thickness of 200
It is composed of a SiO ₂ film of about 600 nm. The first insulating layer 4 is
SiO ₂ film 4a having a thickness of 30 to 80 nm and thickness of 200 to 3
It is composed of a Si ₃ N ₄ film 4b of 00 nm. The second insulating layer 6 is composed of a Si ₃ N ₄ film 6a having a thickness of 100 to 200 nm and an Al ₂ O ₃ film 6b having a thickness of 30 to 50 nm. The first electrode 2 is made of a Mo (molybdenum) film and is also called a back electrode. The second electrode 7 is made of an ITO film and is also called a transparent electrode. By applying a predetermined AC voltage to the plurality of first electrodes 2 and second electrodes 7,
The EL light emitting layer 5 which is sandwiched between both electrodes and constitutes one picture element emits light, and a display is performed.

FIG. 2 is a process chart showing the procedure for manufacturing the thin film EL display device 11. Although the materials used and the film forming method are different, the working steps are the same as those in FIG. 2 in all the examples described below. First, in step a1, a Mo film is sputter-deposited on a glass substrate 1 and processed into a predetermined strip by photolithography to form a first electrode 2.

Next, in step a2, a SiO ₂ film is formed to 25
The insulator 3 is formed with a thickness of 0 nm by vapor deposition by the reactive sputtering method and processed by the photolithography method and the dry etching method so as to cover at least the end portion 2a of the first electrode 2. In the dry etching method at this time,
CF ₄ is used as the dry etching gas, the etching rate is about 350 Å / min for the insulator 3 and about 20 Å / min for the first electrode 2, and selective etching is possible.

Next, in step a3, the SiO ₂ film 4a and the Si ₃ N ₄ film 4b are sequentially formed by the reactive sputtering method to form the first insulating layer 4. Next, in step a4,
EL emission layer 5 formed by electron beam evaporation method or CVD method
And then surface treatment by heat treatment is performed if necessary. Further, in step a5, a Si ₃ N ₄ film 6a and an Al ₂ O ₃ film 6b are sequentially formed by a reactive sputtering method to form a second insulating layer. In step a6, ITO is deposited by a sputtering method and photolithography is performed. The strip-shaped second electrode 7 is formed in the direction orthogonal to the first electrode by the method.

Next, a silicone resin 8 is applied, heated and dried to be cured, and a filter raw material in which a green or red pigment is dispersed in a photosensitive resin is applied on the seal glass 10 and then mosaic is applied by a photolithography method. Process into a shape. This process is repeated for each of the green and red filter films to form the color filter 9, and finally the glass substrate 1 and the seal glass 10 are bonded together.

The thin-film EL display device 11 and the conventional thin-film EL display device 91 manufactured as described above are actually driven, and the breakdown characteristics are examined and compared by an evaluation method in which the element is destroyed while gradually increasing the voltage. In that case, the breakdown voltage of propagate breakdown generated from the first electrode end portion 82a is 2 in the conventional case.
While it was 70V, the breakdown voltage of the first electrode end portion 2a of this example was 350V. Therefore, by forming the insulator 3, the step coverage performance of the first electrode end portion 82a is improved, the dielectric breakdown and the disconnection are less likely to occur, and the reliability of the thin film EL display device 11 is improved.

Next, a second embodiment of the present invention will be described. The feature of this embodiment is that the insulator 23 is formed by the anodic oxidation method. FIG. 3 is a side view of an anodizing apparatus used in the second embodiment of the present invention, FIG. 4 is a process diagram showing a treatment process of the present embodiment, and FIG. 5 corresponds to the process. It is sectional drawing of a board | substrate. When the same materials as those in the first embodiment are used in the second and subsequent embodiments, the same reference numerals are given.

The stainless steel plate is connected to the cathode side of the electrode provided in the anodizing tank 32 containing the 1% ammonium tartrate solution, which is the anodizing solution 33, and the substrate 36 is connected to the anode side. The substrate 36 on which this anodic oxidation is performed is manufactured by the following procedure.

After Ta (tantalum) as the first electrode 22 is deposited on the entire surface of the glass substrate 1 by the sputtering method in step b1, a photoresist 34 is applied over the entire surface of the tantalum layer in step b2. Next, in step b3, as shown in FIG. 5A, the photoresist 3 is formed by the photolithography method while leaving the spaces between the broken line portions 34a and 34b and between the broken line portions 34c and 34d.
4 is patterned, and the tantalum layer is similarly etched by the dry etching method in step b4.
As shown in (2), the photoresist 34 remains on the first electrode 22. The substrate 36 in this state
And

Next, in step b5, the substrate 36 is subjected to an oxidation treatment at an oxidation voltage of 80 V by using the anodizing device shown in FIG. 3, and the oxidation reaction causes the end portion of the first electrode in contact with the anodizing liquid 33. As shown in FIG. 5C, an insulator 23 made of Ta ₂ O ₅ which is an anodized film is formed on the first electrode end 22a. Then, in step b6, the photoresist 34 left on the first electrode 22 is removed as shown in FIG. The formation after the first insulating layer is performed in the same manner as in the first embodiment.

This embodiment also has the same effect as that of the first embodiment. Furthermore, the insulator 2 is formed by the anodic oxidation method.
By producing 3, the dense insulator 23 with few pinholes can be formed. Further, as compared with a method using a vacuum device such as a sputtering method, the facility is simple and mass productivity is excellent, and further, there is an advantage that processing is not required after the insulator 23 is formed. There is.

FIG. 6 shows a thin film EL of the third embodiment of the present invention.
6 is a cross-sectional view showing the structure of the display device 51. FIG. The feature of this embodiment is that a transparent electrode made of an ITO film is used as the first electrode 42. The other components and dimensions of each part are similar to those of the first embodiment.

As a method of manufacturing the thin film EL display device 51, the first electrode 42 is formed to a thickness of 3000 Å by the reactive sputtering method in which indium oxide containing tin added to the substrate glass 1 is adopted as a sintering target. Thereafter, if necessary, surface treatment is performed by heat treatment under reduced pressure, and patterning is performed by photolithography. Next, an alumina insulator 43 is formed by a low pressure CVD method using alkoxy aluminum as a starting material, and is processed by a photolithography method so as to leave a portion covering the end 42a of the first electrode. The process of forming the first insulating layer 4 to the second electrode 7 is the same as in the first embodiment.

Next, regarding the method of sealing the substrate, after sealing glass 10 on which the digging is formed on the EL portion and glass substrate 1 are bonded together, oil 53a mixed with silica gel powder is injected into this space 53. . This oil 53
By injecting a, it is possible to prevent moisture absorption and separation between the EL light emitting layer 5 and the second insulating layer 6 caused by moisture by the silica gel and the oil absorbing moisture invading from the outside or being released from the film.

This embodiment also has the same effect as that of the first embodiment. Further, when the insulator 43 is formed, the low pressure CVD method is used instead of the SiO ₂ sputtering method, so that the insulator 43 having excellent step coverage performance can be formed.

FIG. 7 shows a thin film EL of the fourth embodiment of the present invention.
14A and 14B are a plan view and a cross-sectional view showing the structure of the display device 71.
The constituent elements of the thin film EL display device 71 and the method of manufacturing the same are the same as those in the third embodiment. The difference from the third embodiment is that the width of the insulator 43 formed so as to cover the end 42a of the first electrode is wide, and the first to third
This is about three times as large as that of the above-mentioned embodiment and covers half of the picture elements, and regions A and B having different light emission start voltage values occur in one picture element as shown in FIG. 7 (1). . As specific numerical values of the dimensions shown by reference numerals w7 to w10 in FIG. 7, w7 is 220 μm and w8 is 110 μm.
m and w9 are selected to be 50 μm, and w10 is selected to be 80 μm.

FIG. 8 shows a thin film EL display device 71 of this embodiment.
3 is a graph showing the luminance-voltage characteristics of the conventional and conventional products. Two curves α shown in the graph of FIG. 8 (1)
1, β1 are the measured values of the luminance in different picture elements in the thin film EL display device 71, and this difference is due to the difference in the film thickness distribution in manufacturing the EL light emitting layer and the insulator. Figure 8
The two curves α2 and β2 shown in the graph of (2)
Is a measured value in a conventional EL display device.

As shown in FIG. 8B, the characteristic of the curve showing the luminance-voltage characteristic of the conventional thin film EL display device is that the luminance h5 is
From a sharp rise in the low brightness part indicated by the range k5 from the brightness h6 to the brightness h6, and a point where the high brightness part indicated by the range k6 from the brightness h6 to the brightness h7 becomes saturated. In contrast, as shown in FIG. 8A, in the EL display device 71, the range k1 from the brightness h0 to the brightness h1 and the brightness h2
To the brightness h3, there is a steep rising portion indicated by the range k3 and the range k2 from the brightness h1 to the brightness h2.
And a saturated portion indicated by a range k4 from the brightness h3 to the brightness h4. That is, in this embodiment,
The steep rising portion and the saturated portion are divided into two stages. This is because the region covered with the insulator and the region not covered with the same have different emission start voltages in the same pixel.

In this embodiment, a gentle curve is shown in the halftone region near the range k2, which is suitable for gradation display. In order to make this clearer, the luminance differences L1 and L2 (L2 (L2) between the two curves α1 and β1;
1 = α1-β1, L2 = α2-β2), and the luminance difference-voltage characteristics are shown in the upper part of FIGS. 8 (1) and 8 (2), respectively. First, in the conventional thin-film EL display device, there is a maximum value m indicating that the luminance difference L2 is large in the low luminance part indicated by the range k5, and the luminance difference can be visually recognized, and the difference in gradation level is noticeable. On the other hand, in this embodiment,
A portion having a large luminance difference L1 is divided into a plurality of portions, and the value is improved to be considerably smaller than the conventional maximum value m. This characteristic can be further improved by forming a plurality of layers of the insulator.

[0036]

As described above, according to the present invention, the step coverage performance of the step portion is improved by forming the insulator on the step portion of the first electrode end between the first electrode and the first insulating layer. In addition to being improved, the electric field applied near the end of each of the first electrodes covered with the insulator can be made lower than that of the pixel surface not covered with the insulator,
The dielectric breakdown performance can be improved, and it is possible to prevent pixel damage and wire breakage.

In the case of a so-called inverted structure in which a metal electrode is used as the first electrode, dielectric breakdown is less likely to occur, while
When a transparent electrode is used as the first electrode, a large-sized panel with a reduced wiring resistance as compared with the conventional one can be manufactured, and variation in brightness caused by the length of wiring can be improved, and a highly reliable thin film can be obtained. An EL display device can be provided.

Further, since the light emission starting voltage is different between the part covered with the insulator and the part not covered with the insulator in the same picture element, a thin film EL display device suitable for gradation display can be manufactured. . Further, the light emission starting voltage can be changed by changing the material and the film thickness of the insulator, which can be used for gradation display.

[Brief description of drawings]

FIG. 1 is a thin film EL display device 11 according to a first embodiment of the present invention.
It is a cross-sectional view showing the structure of.

2A to 2D are process drawings showing a manufacturing procedure of the thin film EL display device 11. FIG.

FIG. 3 is a side view of an anodizing device used in a second embodiment of the present invention.

FIG. 4 is a process drawing showing a procedure for forming an insulator 23 in the second embodiment.

FIG. 5 is a cross-sectional view of a substrate showing a procedure for forming an insulator 23 in the second embodiment.

FIG. 6 is a thin film EL display device 41 according to a third embodiment of the present invention.
It is a cross-sectional view showing the structure of.

FIG. 7 is a thin film EL display device 71 according to a fourth embodiment of the present invention.
It is a cross-sectional view showing the structure of.

FIG. 8 is a graph showing luminance-voltage characteristics of the thin film EL display device 71 of the present invention and a conventional device.

FIG. 9 is a cross-sectional view showing the structure of a conventional thin film EL display device 91.

FIG. 10 is a process chart showing the manufacturing procedure of a conventional thin-film EL display device 91.

[Explanation of symbols]

 1 Glass Substrate 2,2a, 22,22a, 42,42a First Electrode 3,23,43 Insulator 4,4a, 4b First Insulating Layer 5 EL Light Emitting Layer 6,6a, 6b Second Insulating Layer 7 Second Electrode 11,51,71 Thin film EL display device

Claims (2)

[Claims] 1. A plurality of strip-shaped first electrodes, a first insulating layer, an EL light emitting layer, a second insulating layer, and a plurality of strip-shaped second electrodes orthogonal to the first electrodes are sequentially laminated on a substrate. Thin film EL
In the display device, a thin film EL display device is characterized in that an insulator is formed in a step difference portion of a first electrode end between the first electrode and the first insulating layer. 2. A step of forming a plurality of strip-shaped first electrodes on a substrate, a step of forming an insulator covering each end of the first electrode, and a step of covering the insulator and the first electrode. Forming a first insulating layer; forming an EL light emitting layer over substantially the entire surface of the first insulating layer; forming a second insulating layer over substantially the entire surface of the EL light emitting layer; A step of forming a plurality of translucent strip-shaped second electrodes in a direction orthogonal to the first electrodes on the surface of the layer, the method for manufacturing a thin film EL display device.