JP2002318556A - Active matrix type planar display device and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the sheet resistance of an electrode on a display surface side without increasing the man-hours for manufacturing in an upper surface emission luminous display device. SOLUTION: The active matrix type planar display device 1, wherein display elements P provided with a light modulating layer 121 between a 1st electrode 117 and a 2nd electrode 122 formed on a substrate 101 are arranged in a matrix form, is provided with auxiliary wirings 118, which is formed in the same layer as the 1st electrode 117, also electrically insulated from the 1st electrode 117 and electrically connected to the 2nd electrode 122.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat display device such as an organic electroluminescence (EL) display device and a method of manufacturing the same, and more particularly to an active matrix type flat display device having a switching element for each display element. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Demand for flat display devices such as liquid crystal display devices has been rapidly increasing by making use of the features of thinness, light weight, and low power consumption with respect to CRT displays. Among them, an active matrix type flat display device in which a switch element is provided for each display element can obtain good display quality without crosstalk between adjacent display elements.
It has been used for various displays including portable information devices.

In recent years, an organic electroluminescence (EL) display device has been actively developed as a self-luminous display device capable of responding faster and having a wider viewing angle than a liquid crystal display device.

[0004] The organic EL display device comprises an organic EL panel and an external drive circuit for driving the organic EL panel.
An organic EL panel has a first electrode, a second electrode arranged opposite to the first electrode, and a display element having an organic light emitting layer interposed between these electrodes arranged in a matrix on a supporting substrate such as glass. And a drive circuit area for driving each display element based on a signal from an external drive circuit.

[0005] As a method of taking out the EL light emission of this organic EL display device to the outside, there are a bottom emission method of taking out light through a support substrate and a top emission method of taking out light to the side opposite to the support substrate.

In an active matrix type organic EL display device of the bottom emission type, a circuit such as a thin film transistor (TFT) for blocking transmission of EL light emission is arranged below the organic light emitting layer, so that a sufficient aperture ratio is secured. Difficult
For this reason, improvement in light use efficiency has been a problem.

On the other hand, in the top emission type organic EL display device, since the EL emission is taken out on the side facing the support substrate, the aperture ratio is determined without being restricted by the circuit arranged on the support substrate side. Therefore, high light use efficiency can be secured.

[0008]

In a flat panel display device, it is essential to use a light-transmitting conductive film for an electrode on the light extraction side. In addition, the common electrode disposed on the light extraction side needs to be formed of a light-transmitting conductive film. However, in general, it is known that a transparent conductive material having optical transparency has a resistivity that is about two to three orders of magnitude higher than that of a normal metal material.

For this reason, the electrode voltage may become non-uniform in the screen surface of the electrode on the light extraction side, which has been a cause of deteriorating the display quality.

[0010] This is particularly remarkable as the screen size increases, and there is a problem that the screen size is restricted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problem, and has as its object to provide an active matrix type flat display device having less display unevenness in a display surface and a method of manufacturing the same.

It is another object of the present invention to provide an active matrix type flat display device whose display quality is not restricted by the screen size, and to provide a manufacturing method which does not impair the productivity. I have.

[0013]

According to the first aspect of the present invention,
A plurality of scanning signal lines arranged on a substrate, a plurality of video signal lines arranged substantially orthogonal to the scanning signal lines, a switching element arranged near these intersections, connected to the switching element, In an active matrix type flat display device in which display elements each having a light modulation layer formed in an independent island shape between a first electrode and a second electrode are arranged in a matrix, the display elements are formed in the same layer as the first electrode, The first electrode is electrically insulated from the first electrode and includes an auxiliary wiring electrically connected to the second electrode.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A self-luminous display and an organic EL display will be described as examples of an active matrix type flat display according to an embodiment of the present invention with reference to the drawings. FIG. 1 is a schematic plan view of an active matrix type organic EL display device 1 according to this embodiment. FIG. 2 is a partially schematic plan view in which a part of the display region in FIG. 1 is enlarged. FIG. 4 is a cross-sectional view taken along line AA of FIG.

The display area of the organic EL panel 2 will be described in detail. In this embodiment, a 10.4-inch size display area is formed, and a video signal line 109 and a scanning signal line 107 are formed on an insulating substrate 101 made of glass or the like. The switching elements SW1 are arranged in a matrix, and
A p-type TFT and an organic EL display element P are formed as a type TFT, a video signal voltage holding capacitor 110, and a drive control element SW2.

The organic EL display element P includes a driving control element S
First electrode 11 made of a light-reflective conductive film connected to W2
7 and the organic light emitting layer 121 disposed on the first electrode 117
And a second electrode 122 disposed opposite the first electrode 117 with the organic light emitting layer 121 interposed therebetween. The organic light emitting layer 121 includes a hole transport layer, an electron transport layer, and a light emitting layer formed for each color.
It may be composed of a layer stack, or may be composed of functionally composite two layers or a single layer. This organic light emitting layer 121
Are arranged on the first electrode 117 exposed from the opening 120b of the partition 120 having a thickness of 3 μm and made of a black resist material for separating the display elements P.

The organic EL display device 1 has a second electrode 122
This is a top emission method in which the side is a display surface, and the second electrode 122 of the organic EL display element P is formed of a light-transmitting conductive film. The light-transmitting conductive film can be formed by using a transparent conductive material having a high transparency of the material itself, or by forming a thin material having a low transparency to have a light-transmitting property. Here, Ba is thin enough to transmit light, for example, a film thickness of 10 n
m, and was formed in common as a transparent conductive film over all display elements. The sheet resistance of this light transmitting conductive film was approximately 10 ⁵ Ω / □.

As shown in FIG. 3, the auxiliary wiring 118 and the second electrode 122 provided on the same layer as the first electrode 117 are connected to a contact portion 120 a provided on the partition 120 so as to expose the auxiliary wiring 118. Are electrically connected via The auxiliary wiring 118 is formed between the first electrode 117 and the partition 1.
The first electrode 1 of each display element P is electrically insulated at 20.
17, and are connected to each other over the display area.

Since the auxiliary wiring 118 electrically connected to the second electrode 122 is uniformly provided in the entire display area, it is possible to suppress the variation in the potential of the light extraction-side electrode in the screen. Become.

Here, the auxiliary wiring 118 has sufficiently smaller resistance than the transparent conductive film forming the second electrode;
More specifically, it is desirable to be formed of a conductive material having a resistivity of 11 × 10 ⁻⁶ Ωcm or less. By using a low-resistance conductive material for the auxiliary wiring as described above, it is possible to further reduce the potential variation in the screen surface of the light extraction side electrode.

Table 1 shows the resistivity of a typical metal material that can be selected as an auxiliary wiring and the resistivity of a transparent conductive material.
[Table 1]

In particular, the auxiliary wiring 118 has 1 × 10 ⁻⁶ Ω
It is desirable to use a conductive material having a resistivity of about cm to ⁶ × 10 ⁻⁶ Ωcm, and it may be a single material or a laminate of a plurality of materials.

In the present embodiment, the auxiliary wiring 118
It is formed of the same material as the first electrode, is formed by stacking three layers of Al, Mo, and ITO and using a conductive material having a resistivity of 4 × 10 ⁻⁶ Ωcm to have a sheet resistance of 10 ⁻¹ Ω / □. I have. This Mo is provided to prevent corrosion due to direct contact between ITO and Al, and may be any material having this function, for example, Ti, W, or the like.

In the organic EL display device thus constructed, the in-plane variation of the light extraction side electrode, here the cathode potential, can be sufficiently reduced as compared with the conventional one. Regardless of the size, the in-plane luminance distribution could be suppressed to within ± 3 cd / m ² .

FIGS. 4A to 4E show examples of the arrangement of the second electrode power supply line and the auxiliary wiring, and FIGS. 5A to 5C.
Is an enlarged view of a part of the display area of (a) to (c) of FIG. In the above-described embodiment, as shown in FIG. 4A, the periphery of the first electrode 117 of each display element P is surrounded and evenly arranged in the display area in a mutually connected pattern (FIG. 5A). Although the provided auxiliary wiring 118 is provided, the present invention is not limited to this, and can be formed in various patterns. At least the auxiliary wiring 118 and the first electrode 117 are electrically separated, and the auxiliary wiring 118 and the second electrode 122 are formed. And may be electrically connected. For example, as shown in FIG. 4B, a rectangular frame-shaped second electrode power supply line 11 surrounding a display area is provided.
9, auxiliary wirings 118 are formed in a matrix,
The auxiliary wirings 118 are formed densely in the center portion of the rectangular frame far from the second electrode power supply line 119, and the auxiliary wirings 118 are formed sparsely in the inner peripheral portion of the rectangular frame close to the second electrode power supply line 119. The density may be changed in the plane (FIG. 5B). Further, the auxiliary wiring 118 may not be linear,
As shown in FIGS. 4C and 4D, the periphery of the first electrode 117 may be formed in a zigzag shape (FIG. 5C). Further, as shown in FIG. 4 (e), a stripe may be formed inside the second electrode power supply line. Further, the size of the pixel may be changed for each color, and an auxiliary wiring whose size is determined according to the distance between the adjacent first electrodes may be provided.
An optimal pattern can be appropriately adopted depending on conditions such as the number of pixels.

As described above, the active matrix type in which the first electrodes are provided in the form of independent islands and the second electrodes are commonly arranged over the display elements is employed. A connected auxiliary wiring can be provided.

Further, according to the present invention, since the auxiliary wiring having a constant potential is provided between the adjacent display elements, the capacitive coupling between pixels can be reduced, and the display quality such as crosstalk is deteriorated. Thus, a higher quality surface display device can be achieved.

Further, since the first electrode 117 is formed on the TFT via the insulating layer 116, the TF under the insulating layer 116 is formed.
The display element P can be formed so as to overlap the T or the wiring, and the aperture ratio by the top emission method can be determined without being restricted by a circuit such as a TFT, and a high light use efficiency can be obtained.

Further, in the above-described embodiment, the case where Ba having a small film thickness is used as the transparent electrode material for the upper electrode (second electrode) of the display element has been described, but other various transparent conductive materials are selected. It is preferable to employ a material suitable for the material of the organic light emitting layer. The second electrode may be composed of a plurality of laminated films, and may be formed by laminating Ba, Ca, etc., and then laminating ITO or SnO.
When the second electrode is used as an anode, ITO or IZO (Indium ZnOxid) having high transparency of the material itself is used.
e) can be used as a transparent electrode material. It is desirable to select a material suitable for the organic light emitting layer also as a material for the lower electrode of the display element, and it is desirable to select a material suitable for the polarity of the electrode.

As described above, according to the present embodiment, since the auxiliary wiring is connected to the second electrode, the resistance of the entire electrode on the light extraction side can be reduced, and the display unevenness in the display surface can be sufficiently suppressed. be able to.

Next, a method for manufacturing the organic EL display device of the present invention will be described. First, a SiN film and a SiO2 film are deposited as an undercoat layer 102 on an insulating substrate 101 made of glass or the like by normal pressure CVD or plasma CVD, and an amorphous silicon film is deposited thereon. Here, the entire surface of the substrate may be doped with a p-type impurity such as boron (B) for controlling the threshold value of the TFT.

Next, the amorphous silicon film is annealed by an excimer laser to crystallize the amorphous silicon film into a polycrystalline silicon film.

Further, a resist is applied to the polycrystalline silicon film, and exposure, patterning and etching processes are performed to form the polycrystalline silicon film in an island shape.

Subsequently, a SiOx film is formed by CVD over the entire surface covering the polycrystalline silicon film.
Form 3 On the gate insulating film 103, MoW is deposited as a gate metal film, a gate electrode 104 in a p-type TFT portion is formed using photolithography technology, boron (B) is doped, and a polycrystalline silicon film of the p-type TFT is formed. Next, a source region 105 and a drain region 106 which are conductive regions are formed.

Next, the gate metal film is patterned to form the gate wiring 107 and the gate electrode 108 of the n-type TFT.
A part 109a of the video signal line 109 and a lower electrode pattern 110a of the video signal voltage holding capacitor 110 are formed.

Thereafter, phosphorus ions (P) are doped from above using the gate electrode 108 or the resist at the time of forming the gate electrode as a mask to form a source region 111 and a drain region 112 in the polycrystalline silicon film in the n-type TFT portion.

Further, an SiOx film serving as an interlayer insulating layer 113 is formed so as to cover all of these upper surfaces by a CVD method or the like, and penetrates through the interlayer insulating layer 113 and the gate insulating film 103 to form source regions 105 and 111 and a drain region 106. ,
After providing a contact hole reaching 112 or the like, Mo /
A metal film made of Al / Mo is formed and patterned to form a source electrode 113, a drain electrode 114, and an organic EL.
The current supply line 115 and the video signal line 109 (109
b) is formed. Thus, the switching element SW1
N-type TFT and p-type T as drive control element SW2
An FT, a video signal line driving circuit Xdr and a scanning signal line driving circuit Ydr in a driving circuit area formed by combining these are formed. In addition, a capacitor 110 for holding a video signal voltage is formed using the organic EL current supply line 115 as an upper electrode.

Further, an insulating layer 116 of SiNx is formed on the entire surface of the substrate.
Is formed, and a contact hole connected to the source electrode 113 of the drive control element SW2 is provided, and then Al / Mo / IT
A metal film made of O is formed and patterned to form a light-reflecting first electrode 117 and an auxiliary wiring 11 which constitute a display element.
8. A second electrode power supply line 119 formed integrally with the auxiliary wiring 118 is formed in a rectangular frame shape surrounding the display area.

As described above, the auxiliary wiring 118 and the first electrode 1
17 is formed using the same material in the same step, so that the auxiliary wiring 118 can be formed without specially providing a step for forming the auxiliary wiring 118.

The first electrode 117 of the display element is disposed on the insulating layer 116 and is connected to the source electrode 113 of the drive control element SW2 via the insulating layer 116, so that the first electrode 117 and the drive control element SW2, Switching element SW1
And so on, and the area of the first electrode can be increased.

Next, a black organic resist material is applied to the entire surface of the substrate to a dry thickness of 3 μm, and then patterned, and an opening for exposing the first electrode 117 at a position corresponding to the first electrode 117 of the display element. A partition 120 for element isolation is formed which has a contact portion 120a which has a contact portion 120b and which exposes the auxiliary wiring 118 on the auxiliary wiring 118.
The partition 120 is preferably a black material having a light shielding property to prevent color mixing of EL light between adjacent elements, and has a film thickness equal to or more than that of an organic light emitting layer for element isolation. Desirably, the shape and height are desirably set so that the second electrode does not break at the contact portion with the auxiliary wiring. For example, when the organic light emitting layer is made of a polymer material as in this embodiment, the organic light emitting layer is formed by an ink-jet method as described later. 1μ
m or more is desirable. When the organic light-emitting layer is a low molecular material, the thickness of the light-emitting layer should be equal to or more than the thickness of the light-emitting layer, specifically, 100 nm or more. In addition, the shape of the partition wall 120 preferably has a taper angle of 80 ° or less so that the second electrode does not break at the contact portion with the auxiliary wiring.

In this embodiment, the contact portion 120a of the auxiliary wiring is formed in a continuous pattern along the auxiliary wiring. However, the contact portion 120a may be formed in a discontinuous dot pattern on the auxiliary wiring.

Further, R, G,
The polymer organic light emitting material corresponding to B is sequentially discharged, and the organic light emitting layer 121 is selectively formed at a position corresponding to the opening 120b of the partition wall 120 on the first electrode. The organic light-emitting layer may be composed of a three-layer stack of a hole transport layer, an electron transport layer, and a light-emitting layer formed for each color, which are formed in common for each color. It may be composed of a single layer.

Next, a light-transmitting conductive film, here, Ba, is formed as a second electrode 122 on the entire surface of the substrate on the organic light-emitting layer 121 so as to have a thickness of 10 nm. The second electrode is connected to an auxiliary wiring 118 formed on the insulating layer 116 and in the same layer as the first electrode 117 via a contact portion 120a.

Thereafter, a transparent insulating substrate made of glass or the like is disposed as a sealing substrate so as to face the supporting substrate, and the periphery of the substrate is hermetically sealed to complete the organic EL display device.

In the above-described embodiment, the case where a high molecular weight organic light emitting material is used for the organic light emitting layer has been described. However, the present invention is not limited to this. For example, a low molecular weight organic light emitting material such as Alq ₃ may be used. Is also good. When a low molecular weight organic light emitting layer is formed, it can be formed by vacuum evaporation or the like.

As described above, by providing the auxiliary wiring connected to the second electrode, the resistance of the entire light extraction side electrode in the display surface can be reduced.

Also, by employing the top emission method, it is possible to realize an organic EL display device having a higher aperture ratio than that of the bottom emission method, and it is possible to improve the front luminance. Further, power consumption for achieving a predetermined front luminance can be reduced as compared with the bottom emission method, and the life of the organic EL element can be prolonged.

In particular, since the display element is arranged on a circuit formed on the support substrate via the insulating layer, the aperture ratio can be further improved.

Since the auxiliary wiring is formed in the same step with the same material as the first electrode, it is possible to prevent an increase in the number of steps without newly providing a step for forming the auxiliary wiring.

In the above embodiment, an organic EL display device has been described as an example. However, the present invention is not limited to this, and a general flat display device in which a light modulation layer is formed in an island shape independently for each pixel. Applicable to

[0052]

According to the present invention, the occurrence of display unevenness can be suppressed, and a flat display device with high display quality can be realized. Further, the flat display device can be achieved without increasing the number of manufacturing steps.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of an organic EL display device according to an embodiment of the present invention.

FIG. 2 is a partial schematic plan view showing a display area of an organic EL display device according to an embodiment of the present invention.

FIG. 3 is a partial schematic cross-sectional view showing a display area of an organic EL display device according to an embodiment of the present invention.

FIG. 4 is an auxiliary wiring showing one embodiment of the present invention;
FIG. 5 is a plan view showing a second electrode power supply line.

FIG. 5 is a first electrode showing one embodiment of the present invention;
FIG. 4 is a plan view showing auxiliary wiring.

[Explanation of symbols]

 117 first electrode 118 auxiliary wiring 120 partition 121 light modulating layer 122 second electrode

Claims (9)

[Claims] A plurality of scanning signal lines disposed on a substrate;
A plurality of video signal lines arranged substantially orthogonal to the scanning signal lines; a switching element arranged near the intersection thereof; and a switching element connected to the switching element, and an independent island between the first electrode and the second electrode. In an active matrix type flat display device in which display elements having a light modulation layer to be formed are arranged in a matrix, the display elements are formed in the same layer as the first electrode, and are electrically insulated from the first electrode; An active matrix type flat display device, comprising: an auxiliary wiring electrically connected to the second electrode. 2. The active matrix type flat display device according to claim 1, wherein said first electrode and said auxiliary wiring are formed of the same material. 3. The active matrix type flat display device according to claim 1, wherein the auxiliary wiring has a lower resistance than the second electrode. 4. The active matrix type flat display device according to claim 1, wherein said light modulation layer is formed of an organic light emitting material. 5. The active matrix type flat display device according to claim 1, wherein said second electrode is formed of a light transmitting conductive material. 6. The active matrix type flat display device according to claim 5, wherein light is extracted to the outside through said second electrode. 7. A method of manufacturing an active matrix type flat display device comprising a matrix of display elements provided with a light modulation layer between a first electrode and a second electrode formed on a substrate, the method comprising the steps of: Forming the first electrode and the auxiliary wiring in the same step; forming an insulating film having a region exposing the first electrode and the wiring;
Forming the light modulating layer at a position corresponding to the exposed region of the electrode, disposing a light transmitting conductive film over substantially the entire surface of the substrate, and opposing the first electrode via the light modulating layer. Forming the second electrode electrically connected to the auxiliary wiring. 8. The method according to claim 7, wherein said insulating film is made of an organic resist material. 9. The method according to claim 7, wherein the step of forming the light modulation layer includes a step of selectively discharging an organic light emitting material.