JP2003229283A - Flat-panel display device and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently utilize the light emitted from a display device. <P>SOLUTION: The display device comprises a glass plate 20, a plurality of organic EL elements OLED emitted light on the glass plate 20 as display pixels independent from each other, and a reflection layer RF reflecting the light emitted from the plurality of organic EL elements OLED to the glass plate 20 side. Especially, the reflection layer RF includes a plurality of concave parts 15 which are respectively separated from the plurality of organic EL elements OLED through light transmitting insulation films 26, and make the reflected light travel toward corresponding organic EL elements OLED. <P>COPYRIGHT: (C)2003,JPO

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 in which a plurality of display elements are arranged as independent display pixels on a supporting substrate and a method for manufacturing the same, and in particular, light emitted from each display pixel to the supporting substrate side. The present invention relates to a flat panel display configured to reflect light and a method for manufacturing the same.

[0002]

2. Description of the Related Art A flat panel display device represented by a liquid crystal display device is characterized by being thinner, lighter and lower in power consumption than a CRT display, and therefore its demand is rapidly increasing. Among them, the active matrix flat panel display device in which a plurality of display elements are driven through independent switch elements can reduce crosstalk between adjacent display elements and is therefore used in various displays including mobile information devices. Has been done.

In recent years, an organic electroluminescence (EL) display device has been actively developed as a self-luminous display capable of obtaining higher response and wider viewing angle than a liquid crystal display device. A typical organic EL display device includes an organic EL panel including a plurality of organic EL elements arranged in a matrix as independent display pixels and a plurality of current control circuits respectively connected to the organic EL elements, and the organic EL panel. It is composed of an external drive circuit provided outside the panel. Each organic EL element has a structure in which an organic light emitting layer is sandwiched between a pair of electrodes, and is formed on a supporting substrate such as glass. By injecting electrons and holes into the organic light emitting layer and recombining them, excitons are generated. Then, the excitons emit light by light emission that occurs when the excitons are deactivated. The light from the organic light emitting layer is extracted to the outside by either a bottom emission method of transmitting the light through the support substrate or a top emission method of emitting the light from the side opposite to the support substrate.

In a bottom emission type organic EL display device, if the current control circuit is arranged below the organic light emitting layer, this switch element blocks light from the organic light emitting layer.
It is necessary to lay out the current control circuit and the organic EL element so that they do not overlap each other on the supporting substrate. Therefore, the current control circuit occupies a part of the pixel area, resulting in a reduction in the aperture ratio of the display pixel. On the other hand, in the top emission type organic EL display device, since the light from the organic light emitting layer is extracted from the side opposite to the supporting substrate, the opening is performed without being restricted by the current control circuit arranged on the supporting substrate side. It is possible to set a rate to ensure high light utilization efficiency.

[0005]

By the way, in a top emission type organic EL display device, a supporting substrate side electrode of an organic EL element is used as a reflection electrode for reflecting light emitted from an organic light emitting layer. However, a part of the light reflected by the reflective electrode travels in an oblique direction and enters the partition wall surrounding the organic EL display element, and does not exit to the space on the side opposite to the support substrate. This not only reduces the efficiency of light utilization,
This causes interference with the light of the adjacent organic EL element and causes color bleeding.

Further, since the reflective electrode also reflects external light, the contrast is lowered. In order to deal with this, a technique of arranging a circularly polarizing plate on the light emitting surface (display surface) side of the organic EL display device is known, but this causes an increase in cost and a decrease in productivity.

The present invention has been made in view of the above-mentioned technical problems, and it is an object of the present invention to provide a flat display device capable of efficiently utilizing light emitted from a display element and a manufacturing method thereof. To aim. It is another object of the present invention to provide a flat display device with good display quality, and in particular to provide a method for manufacturing a flat display device that does not impair productivity.

[0008]

According to the present invention, a support substrate, a plurality of display elements that emit light as independent display pixels on the support substrate, and a plurality of display elements emit light toward the support substrate. And a light reflection layer that reflects the light,
A flat display device is provided in which a light reflection layer is separated from a plurality of display elements via a light transmissive insulating film and includes an incident angle adjusting unit that directs each reflected light toward a corresponding display element.

Further, according to the present invention, the step of forming the light reflecting layer on the supporting substrate and the step of forming the light transmissive insulating film covering the light reflecting layer respectively emit light as independent display pixels. And a step of forming a plurality of display elements, the light-reflecting layer forming step includes forming a light-reflecting layer so as to include an incident angle adjusting section that reflects light from the plurality of display elements and directs each reflected light toward the corresponding display element. A method for manufacturing a flat display device to be formed is provided.

In this flat panel display device and the manufacturing method thereof, the light reflection layer includes an incident angle adjusting section which is separated from a plurality of display elements via the light transmissive insulating film, and the incident angle adjusting section is provided from the corresponding display element. Light is reflected and directed to this display element. Therefore, the light emitted from the display element can be surely emitted to the space on the side opposite to the support substrate to improve the light utilization efficiency. Further, it is possible to prevent the deterioration of the image quality caused by the interference of the reflected light with the light of the adjacent display element.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A flat panel display device according to an embodiment of the present invention will be described below with reference to the drawings. This flat display device is a top emission type active matrix organic EL display device.

FIG. 1 shows a circuit configuration of this flat display device. This flat display device includes an organic EL panel PNL and an external drive circuit DRV.

The external drive circuit DRV is a controller that receives data output from a signal source such as a personal computer, generates control signals for driving the organic EL panel PNL, and performs digital processing such as rearrangement of video signals. It is composed of a unit 1, a plurality of driver ICs 2 for converting a video signal into digital / analog, and a DC / DC converter 3 for generating various power supply voltages for driving the controller unit 1, the driver IC 2 and the organic EL panel PNL. On the other hand, the organic EL panel PNL includes a plurality of display pixels PX arranged in a matrix in the display area DS, a plurality of signal lines X (X1 to Xm) arranged along a column of the plurality of display pixels PX, and a plurality of signal lines X. A plurality of scanning lines Y (Y1 to Yn) arranged along the rows of the display pixels PX, a signal line driving circuit 5 that drives the plurality of signal lines X, and a scanning line driving circuit that drives the plurality of scanning lines Y. 6 is provided.

A plurality of display pixels PX are adjacent to each other in the row direction.
One color display pixel is configured by a set. Each display pixel PX
Includes an organic EL element OLED that emits light having a wavelength corresponding to red, green, or blue, and a current control circuit 7 that controls a current flowing through the organic EL element OLED. The current control circuit 7 includes, for example, an N-channel thin film transistor 11, a P-channel thin film transistor 12, and a capacitive element 13. Here, the thin film transistor 11 is arranged in the vicinity of the intersection of the corresponding signal line X and the corresponding scanning line Y, and is used as a switch element for taking in a video signal from the corresponding signal line X by controlling the corresponding scanning line Y. Thin film transistor 12
Is connected in series with the organic EL element OLED between the power supply lines Vdd and Vss, and is used as a current driving element for flowing a current to the organic EL element OLED based on the video signal voltage applied via the thin film transistor 11. The capacitor 13 is used to hold the video signal voltage when the thin film transistor 11 is in the non-conducting state.

FIG. 2 shows a planar structure of one color pixel of the organic EL panel PNL, and FIG. 3 shows a cross section taken along line III-III shown in FIG. As shown in FIG. 2, the display pixel PX is arranged in a region surrounded by the scanning line Y and the signal line X. The source electrode S of the thin film transistor 11 is connected to the signal line X,
The gate electrode G is connected to the scanning line Y, and the drain electrode D is provided through the lower electrode of the capacitive element 13 which is capacitively coupled to the power supply line Vdd which is the upper electrode of the capacitive element 13.
It is connected to the second gate electrode G. Thin film transistor 12
The source electrode S of is the anode electrode AD of the organic EL element OLED.
And the drain electrode D is connected to the power supply line Vdd.

As shown in FIG. 3, an organic EL panel PNL
Has a structure in which thin film transistors 11 and 12 and an organic EL element OLED are sequentially stacked on a glass substrate 20 serving as a supporting substrate. The glass substrate 20 may be replaced with a substrate made of, for example, an insulating material such as synthetic resin, a conductive material, a semiconductor, or the like. In particular, when a conductive material or a semiconductor is used,
It is necessary to cover the substrate 10 with an insulating film such as SiO ₂ or SiN and form the thin film transistors 11 and 12 and the organic EL element OLED on this insulating film. Thin film transistor 11,
Each of 12 is of a top gate type, and has a structure in which a gate electrode G is formed on, for example, a polysilicon (Poly-Silicon) semiconductor thin film via a gate insulating film.

The organic EL element OLED has a structure in which an organic light emitting layer EM is sandwiched between an anode electrode AD and a cathode electrode CD. The anode electrode AD is ITO (Indium Tin Oxi).
de) or other light-transmissive conductive material, and the cathode electrode CD
Is made of a conductive material such as an alkaline earth metal or a rare earth metal, which is thin enough to have light transmittance. Organic EL
In the device OLED, when the holes injected from the anode electrode AD and the electrons injected from the cathode electrode CD are recombined inside the organic light emitting layer EM, the organic molecules forming the organic light emitting layer EM are excited and excited. Spawn a child. Light is emitted from the organic light emitting layer EM in the process of radiation-deactivation of the excitons, and the light is emitted to the outside through the light-transmitting cathode electrode CD. The organic light emitting layer EM may be composed of a three-layer stack of a hole transport layer, an electron transport layer, and a light emitting layer in order to improve the light emission efficiency, or may be a functionally composite two layer or a single layer. May be.

The organic EL display panel PNL further includes the organic light emitting layer EM of the plurality of organic EL elements OLED and the glass substrate 2.
A light reflection layer RF that reflects the light emitted to the 0 side is provided, and the light reflection layer RF is an organic EL element via a light transmissive insulating film 26.
A plurality of concave portions 15 which are separated from the OLED and face the corresponding organic EL element OLED are included as incident angle adjusting portions. Each recess 15 has an inclined surface 16 along the outer edge of the organic light emitting layer EM of the corresponding organic EL element OLED. The light reflection layer RF is made of a conductive material such as metal, and is used as an anode electrode AD of the organic EL element OLED.
Also serves as a wiring member for connecting the source electrode S of the thin film transistor 12.

Next, a method of manufacturing the above flat panel display device will be described.

First, atmospheric pressure CVD or plasma CVD
Thus, the SiN film and the SiO ₂ film are deposited as the undercoat layer 21 on the insulating substrate 20 such as glass, and the amorphous silicon film is deposited thereon. Here, in order to control the threshold value of the thin film transistors 11 and 12, the entire surface of the substrate may be doped with P-type impurities such as boron (B).

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 are performed to form the polycrystalline silicon film in an island shape.

Subsequently, a SiOx film is formed by CVD on the entire surface covering the polycrystalline silicon film to form the gate insulating film 22.
To form. A resist mask that exposes the source region and the drain region of the N-channel thin film transistor is formed on the gate insulating film 22 by using a holographic technique. Using this resist mask as a mask, phosphorus ions (P) are doped to form a source region and a drain region, which are conductive regions, in the polycrystalline silicon film of the thin film transistor 11.

Next, MoW is deposited as a gate metal film on the gate insulating film and the polycrystalline silicon film, and the gate metal film is patterned by using the photolithography technique to form the gate electrode G of the P-channel thin film transistor 12. .

After that, the gate electrode G of the thin film transistor 12 or the resist for forming the gate electrode is used as a mask to dope boron ions (B) from above to form a source region and a drain region in the polycrystalline silicon film of the P channel thin film transistor 12. .

Then, the gate metal film is further patterned to form the gate wiring and the N-channel thin film transistor 1.
1, the gate electrode G, a part of the signal line Xa, the capacitance element 13
Forming the lower electrode of. Then, using these gate metal films as masks, phosphorus ions (P) are implanted at a low concentration to form LDD regions between the source and drain regions and the channel region.

Further, a SiOx film to be an interlayer insulating layer 23 is formed by a CVD method or the like so as to cover all of the upper surfaces thereof, and penetrates through the interlayer insulating layer 23 and the gate insulating film 21 to source and drain the thin film transistors 11 and 12. After forming a contact hole reaching the area, Mo / Al
A metal film made of / Mo is formed and patterned to form the source electrode S, the drain electrode D of the thin film transistors 11 and 12, the power supply line Vdd, and a part Xb of the signal line X. The thin film transistors 11 and 12 are formed by the above processing. The signal line driving circuit 5 and the scanning line driving circuit 6 are formed simultaneously with the thin film transistor 11 by the same process as the N-channel thin film transistor, and the thin film transistor 12 is formed by the same process with the P channel at the same time.
Obtained as a combination of channel transistors. Further, the upper electrode of the capacitive element 13 is formed as a part of the power supply line Vdd.

Further, a SiNx insulating layer 24 is formed on the entire surface of the substrate, and contact holes for exposing the source electrodes S of the thin film transistors 12 of all the display pixels PX are provided. After that, the insulating layer 24 is partially half-etched, and the insulating layer 24 is covered with Mo / Al / Mo, Mo / Al, A
A light reflection layer RF having a plurality of recesses 15 is formed by forming a metal film such as g and performing patterning processing. The light reflection layer RF is composed of a plurality of metal film portions divided by a patterning process, and each metal film portion contacts the source electrode S of the thin film transistor 12 of the corresponding display pixel PX around the recess 15. After that, a resist material or an organic material such as polyimide is applied to the entire surface as the light-transmitting insulating film 26 to form a contact hole that partially exposes each metal film of the light-reflecting layer RF around the recess 15. Subsequently, an ITO film is formed to cover the entire light-transmissive insulating film 26 and a patterning process is performed to contact the metal films of the light-reflecting layer RF and to face the recesses 15 of these metal films. To form.

Next, an organic insulating material having a film thickness of 3 μm is applied to the entire surface of the light transmissive insulating film 26 and dried, and the organic insulating material film is subjected to a patterning process to correspond to the plurality of recesses 15. A partition film 27 is formed to cover the light-transmissive insulating film 26, leaving a plurality of openings OP exposing the anode electrodes AD in the region.

Further, by the ink jet method, R,
Polymeric organic light emitting materials corresponding to G and B are discharged into the openings OP, respectively, and a plurality of organic light emitting layers EM are formed on the plurality of anode electrodes AD exposed by the openings OP.
Are formed with a thickness of about 100 nm. After this,
For example, a light-transmissive conductive film such as Ba is used as the organic light emitting layer EM.
The barrier film 27 is formed to a thickness of 10 nm. In this case, the sheet resistance of the light transmissive conductive film is about 1.
It becomes 0 ⁵ Ω / □. The cathode electrode CD of each organic EL element OLED is commonly configured by such a light transmissive conductive film. After that, a transparent insulating substrate such as glass is arranged to face the supporting substrate 20 on the cathode electrode CD side, and the periphery of these substrates is sealed in, for example, a nitrogen atmosphere.

The partition film 27 has a film thickness equal to or larger than the thickness of the organic light emitting layer EM in order to separate the organic EL devices OLED from each other, and the opening OP is a light-transmissive conductive film for the cathode electrode CD. It is desirable to set a tapered shape inclined at a taper angle of about 80 degrees so as not to cause breakage. The above-mentioned inkjet method is used when the organic light emitting material is a polymer. In this case, the thickness of the partition film 27 is preferably 1 μm or more in order to surely store the organic light emitting material in the opening.

That is, the manufacturing method described above is used in the supporting substrate 20.
A step of forming a light reflection layer RF thereon, a step of forming a light transmissive insulating film 26 covering the light reflection layer RF, and a plurality of organic EL elements OLED that emit light as independent display pixels.
And a step of forming. Here, in the light reflecting layer forming step, a plurality of concave portions 15 that reflect light from a plurality of display organic EL elements OLED and direct each reflected light to the corresponding organic EL element OLED.
The light reflection layer is formed so as to include the incident angle adjusting portion.
In the process of forming the organic EL element OLED, a partition film 27 that covers the light-transmissive insulating film 26 is formed by leaving a plurality of openings OP in regions corresponding to the plurality of recesses 15, and the plurality of openings OP are formed independently of each other. A plurality of organic EL elements OLED are formed as the display pixels PX. More specifically, in this forming process, a light-transmissive conductive film is formed on the light-transmissive insulating film 26, and the light-transmissive conductive film is patterned. Anode electrode A
D is formed, a partition film 27 is formed to cover the plurality of anode electrodes and the light transmissive insulating film 26, and the partition film 27 is patterned so as to expose a part of the plurality of anode electrodes. To form these openings O
A process of forming a plurality of organic light emitting layers EM on the plurality of anode electrodes AD exposed in P and further forming a cathode electrode covering the plurality of organic light emitting layers EM is included.

In the flat panel display device obtained by the above manufacturing method, the light reflection layer RF includes a plurality of recesses 15 separated from the plurality of organic EL elements OLED via the light transmissive insulating film 26,
Each recess 15 reflects the light from the corresponding organic EL element OLED and directs it toward this organic EL element OLED. Further, each concave portion 15 has an inclined surface 16 along the outer edge of the organic light emitting layer EM of the corresponding organic EL element OLED. Therefore, each organic EL element
The light emitted from the OLED can be emitted to the space on the opposite side of the support substrate 20 to improve the light utilization efficiency.

FIG. 4 shows a comparative example of how light is emitted from the organic light emitting layer. When the light reflecting layer RF is arranged apart from the organic EL element OLED and has a recess, the organic light emitting layer E
The light from M is easily emitted to the external space through the opening OP as shown in (a). 6 of light from the organic light emitting layer EM
0 to 80% can be effectively used. On the other hand, when the anode electrode AD of the organic EL element OLED also serves as the light reflecting layer RF as shown in (b), the organic light emitting layer E
The light from M easily enters the partition film 27, and only 30 to 50% of this light is emitted to the external space through the opening OP.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist thereof.

In the above-mentioned embodiment, the case where the organic light emitting material is a high molecular type has been described, but a low molecular weight organic light emitting material such as Alq ₃ may be used. In this case, the organic light emitting layer EM is formed by vacuum vapor deposition of an organic light emitting material or the like. At this time, the thickness of the partition film 27 may be 100 nm or more, which is the thickness of the organic light emitting layer EM.

In the above-described embodiment, the light reflection layer RF is composed of a plurality of metal layers which also serve as wiring members for connecting the plurality of organic EL elements OLED and the plurality of thin film transistors 12 arranged below the light reflection layer RF. However, this structure can be a structure as shown in FIG. 5, for example. Figure 5
In the first modification shown in FIG. 1, the light reflection layer RF is maintained as a single metal layer, and instead, a plurality of organic EL elements OLEDs are used.
And a plurality of thin film transistors 12 arranged below the light reflection layer RF, respectively. In this case, light utilization efficiency similar to that of the structure shown in FIG. 2 can be obtained, while the light reflection layer RF is used.
Since it is not necessary to consider the selectivity with respect to ITO or the source electrode as the member, the choice of materials is expanded.

Further, in the above-mentioned embodiment, each light reflection layer R is provided.
Although F has a structure having one concave portion 15, each concave portion 15 corresponds to the corresponding organic EL element OL as in the second modification shown in FIG.
It may be configured to further have an uneven surface 17 facing the organic light emitting layer EM of the ED. After forming a contact hole in the insulating layer 24 of SiNx, the uneven surface 17 is coated with a photosensitive organic insulating film and is non-uniformly etched under predetermined exposure and development conditions. It is obtained by forming. With such a structure, the light utilization efficiency similar to that of the structure shown in FIG. 2 can be obtained, while external light can be scattered to increase the contrast ratio.

Further, in FIG. 6, although formed together with the metal film of the light reflection layer RF, a plurality of metal film portions insulated from the metal film of the light reflection layer RF respectively connect the plurality of thin film transistors 12. It is provided as a wiring member. In this case, the light reflection layer RF and the anode electrode AD can be used as a test capacitor. This test capacitor accumulates electric charges when the signal line driving circuit 5, the scanning line driving circuit 6, and the current control circuit 7 are operated with the potential of the anode electrode AD fixed after the formation of the anode electrode AD. By detecting the accumulated charges with an electron beam tester or the like, it becomes possible to find a defective substrate before forming the organic EL element OLED.

Although the above embodiment has been described by using the organic EL display panel PNL as an example of the flat panel display device,
The present invention can be applied to all flat display devices in which a plurality of display pixels PX are formed in independent islands.

[0041]

According to the present invention, it is possible to provide a flat display device capable of efficiently utilizing light emitted from a display element and a manufacturing method thereof.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of a flat panel display device showing an embodiment of the present invention.

FIG. 2 is a diagram showing a planar structure of one color pixel of the organic EL panel shown in FIG.

3 is a diagram showing a cross section taken along line III-III shown in FIG.

FIG. 4 is a diagram showing a comparative example of how light is emitted from the organic light emitting layer shown in FIG.

FIG. 5 is a diagram showing a first modification of the configuration shown in FIG.

FIG. 6 is a diagram showing a second modification of the configuration shown in FIG.

[Explanation of symbols]

15 ... Recess 16 ... Inclined surface 17 ... uneven surface 20 ... Glass substrate 26 ... Light-transmissive insulating film 27 ... Partition film RF ... Light reflection layer AD ... Anode EM ... Organic EL light emitting layer OLED: Organic EL element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/14 H05B 33/14 A 33/22 33/22 Z

Claims (10)

[Claims] 1. A support substrate, and a plurality of display elements that emit light as independent display pixels on the support substrate,
A light reflection layer that reflects the light emitted from the plurality of display elements to the supporting substrate side, the light reflection layer is separated from the plurality of display elements via a light transmissive insulating film, A flat display device comprising an incident angle adjusting section directed to a corresponding display element. 2. The flat display device according to claim 1, wherein each display element is an electroluminescence element having a structure in which an organic light emitting layer is sandwiched between a pair of light transmitting electrodes. 3. The flat panel display device according to claim 1, wherein the incident angle adjusting portion is formed as a concave portion having an inclined surface along an outer edge of the organic light emitting layer of the display element. 4. The concave portion further has an uneven surface facing the organic light emitting layer of the display element.
The flat panel display device according to. 5. The light reflection layer has a plurality of openings surrounding wiring members respectively connecting the plurality of display elements and a plurality of drive elements arranged below the light reflection layer. Item 2. The flat panel display device according to Item 1. 6. The light reflection layer is formed of a plurality of metal layers that also serve as wiring members that connect the plurality of display elements and the plurality of drive elements arranged below the light reflection layer, respectively. The flat panel display device according to claim 1. 7. A step of forming a light-reflecting layer on a supporting substrate, a step of forming a light-transmissive insulating film covering the light-reflecting layer, and a plurality of display elements each emitting light as an independent display pixel. And a step of forming the light reflection layer, the light reflection layer forming step includes forming the light reflection layer so as to include an incident angle adjusting portion that reflects light from the plurality of display elements and directs each reflected light toward a corresponding display element. A method of manufacturing a flat panel display device, comprising: 8. The display element forming step includes forming a light-transmissive conductive film on the light-transmissive insulating film and patterning the light-transmissive conductive film, whereby the display device is disposed above the plurality of recesses. Forming a plurality of first electrode layers, forming a partition film covering the plurality of first electrode layers and the light-transmissive insulating film, and patterning the partition film so as to expose a part of the plurality of electrode layers. To form a plurality of openings, thereby forming a plurality of organic light emitting layers on the plurality of electrode layers exposed in the plurality of openings, respectively, and further forming a second electrode layer covering the plurality of organic light emitting layers. The manufacturing method according to claim 7, further comprising: 9. The manufacturing method according to claim 7, wherein the light-transmissive insulating film is made of an organic resist material. 10. The manufacturing method according to claim 7, wherein the organic light emitting layer forming process is performed by a method of discharging a liquid organic light emitting material into the opening.