JP2003059649A - Electrostatic induction driven organic electroluminescence display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display panel in which electricity can be supplied to the element without wiring to the electrode of the electroluminescence display element mounted on the display panel. SOLUTION: The display panel comprises at least a pair of organic EL elements for one picture element, a transparent substrate that carries the pair of elements from the anode side, an insulating sealing membrane that covers the pair of elements and seals these in insulation on the transparent substrate, and at least a pair of drive electrodes that are opposed to each of the cathodes of the above pair of elements interposing the insulating sealing membrane, and the anode on one side and the cathode on the other side of the above pair of electroluminescent elements are mutually connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display panel using an organic electroluminescence element (hereinafter simply referred to as "organic EL element").

[0002]

2. Description of the Related Art An organic electroluminescence display panel (hereinafter simply referred to as "organic EL display panel") is
An organic EL element is used as a light emitting pixel to display an image or a character. That is, organic EL elements are laid in a matrix on a display panel, and each pixel is excited to emit light by a driving voltage supplied from a driving power supply circuit to perform a display process.

In a conventional organic EL display panel, the organic EL is generally mounted on a transparent substrate such as glass or plastic film.
A large number of elements are laid, and in order to protect these elements from the external environment such as moisture and dust, these elements are insulated and sealed on a transparent substrate with an insulating sealing coating such as a silicon oxide coating. Therefore, in order to connect the organic EL element and the drive power supply circuit, the electrode is directly drawn from the organic EL element on the panel, and the electrode is led to the drive power supply circuit outside the display panel through the outer periphery of the insulating sealing film. It will need to be routed.

Conventionally, in order to achieve such an object, a connecting electrode is once drawn out of the insulating sealing film to form a connecting pattern, and further, an anisotropic conductive film such as anisolum is used to form an external power feeding side. It adopted a structure to make an electrical connection with the connection pattern. However, such a structure has a drawback that the manufacturing process of the display panel is complicated because the thermocompression bonding process is required when forming the electrical insulation by the anisotropic conductive film. In addition, such a structure generally has a drawback that the anisotropic conductive film is easily peeled off, and once the peeling occurs, it is difficult to reattach the anisotropic conductive film.

Further, since the electrodes are pulled out from the organic EL element from the peripheral portion of the display panel, it is difficult to connect the electrodes near the center of the light emitting surface. Therefore, when the electrodes are drawn out from all the organic EL elements forming the display panel, a dead space is generated in the peripheral portion of the display panel, which is also a factor to increase the area of the entire display panel.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is possible to drive an organic EL element from a driving power supply circuit without wiring an electrode of the organic EL element through an insulating sealing film. It is an object of the present invention to provide a display panel capable of supplying power to a display.

[0007]

According to the present invention, an organic EL display panel is used which uses an organic EL element as a pixel and excites the organic EL element to emit light by a driving voltage supplied from a driving power supply circuit to display an image on the panel. At least one pair of organic EL elements for one pixel, a transparent substrate carrying the pair of organic EL elements from its anode side, and the organic EL element.
An insulating sealing film that covers the element pair and insulates and seals it on the transparent substrate, and the organic EL device with the insulating sealing film interposed therebetween.
Each of the cathodes of the element pair includes at least one pair of drive electrodes facing each other, and one anode and the other cathode of the light emitting element pair are connected to each other.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of an organic EL display panel according to the present invention is shown in the configuration diagram of FIG. In FIG. 1, the induction electrode side substrate (10) is an insulating substrate formed of, for example, a polymer material such as plastic, and the induction electrode (10) forming a pair for each pixel provided on the panel side substrate described later ( 11) is buried. In addition, the induction electrode (1
1) is connected to a drive power supply circuit (13) provided outside the panel via a connection line (12).

The drive power supply circuit (13) is an oscillating circuit for generating a predetermined AC voltage, and its oscillating waveform is not limited to a general sine wave, but may be any other rectangular or triangular wave. good. Further, various parameters relating to oscillation conditions such as the frequency and amplitude of the oscillation waveform can be set to various values in relation to the emission brightness required for the organic EL element provided on the panel-side substrate described later.

In FIG. 1, only two electrodes are shown as the induction electrodes facing one pixel of the panel-side substrate, but this embodiment is not limited to this, and the number of electrodes is on the panel side. Organic E that constitutes one pixel provided on the substrate
It corresponds to the number of L elements. However, even if the number of electrodes is two or more, two or more electrodes should be connected in parallel.
There is no one electrode group, and such a pair of electrode groups is connected to the driving power supply circuit (1
The point of connection to 3) is the same as the configuration shown in FIG.

The panel-side transparent substrate (20) is a transparent substrate formed of, for example, a polymer (plastic) film such as polycarbonate or polyethersulfone, glass, or the like, and an organic EL element on the substrate. Pixels are laid in a matrix. That is, FIG. 1 shows only one pixel on the substrate, and an actual display panel has a structure in which a large number of such pixels are laid in each of the XY directions on the panel surface.

As shown in FIG. 1, one organic EL element is
The transparent electrode (24) and the metal electrode (22) sandwich the organic functional layer (23). Here, the organic functional layer is a single-layer structure having only a light emitting layer, a two-layer structure having an organic hole transporting layer and a light emitting layer, or a three layer having an organic hole transporting layer, a light emitting layer and an organic electron transporting layer. The term “structure” refers to a laminated structure composed of a plurality of layers having an electron or hole injection layer or a carrier block layer inserted between these appropriate layers.

The transparent electrode (24) is a light-transmissive electrode made of an indium-based oxide such as indium tin oxide (ITO) and serves as an anode of the organic EL element. . Meanwhile, the metal electrode (22)
Is made of metal such as aluminum and functions as a cathode (cathode) of the organic EL element. The organic functional layer (23) is
When excited by the power supply from the upper and lower electrodes, a light emission phenomenon is exhibited, and this light emission passes through the transparent electrode (24) and the transparent substrate (20) and is emitted to the outside of the display panel.

In the present embodiment, as shown in FIG. 1, one pixel is composed of two organic EL elements on the left and right, and the anode and cathode of each element are connected to each other using an electrode connection line (25). It has a structured structure. Such electrode connecting wire (2
5) may be constructed by connection by ordinary wire bonding, or by providing a protruding piece on the metal electrode (22) of each element and extending the protruding pieces to each other to form the transparent electrode (24) of the other element. ).

It should be noted that in FIG. 1, one pixel corresponds to two organic E
Although it is composed of L elements, this embodiment is not limited to this, and one pixel may be composed of an even number of two or more organic EL elements. However, even in this case, a plurality of organic EL elements are formed as an organic EL element pair composed of two organic EL elements, and the positive and negative electrodes are interconnected for each organic EL element pair.

In this embodiment, as is clear from FIG. 1, SiON and SiO are formed so as to cover the entire organic EL element pair.
An insulating sealing film (21) made of a silicon oxide layer such as x is provided to completely hermetically seal the organic EL element pair on the transparent substrate (20). That is, the electrode of the organic EL element is not led out through the insulating sealing film (21). Therefore, the process of forming the insulating sealing film (21) on the panel-side transparent substrate (20) is facilitated, and the reliability of the insulating sealing process is also improved.

Next, the operation of the organic EL display panel based on the embodiment of FIG. 1 will be described. First, FIG. 2 shows an electrical equivalent circuit of the constituent elements for one pixel in FIG. In FIG. 2, the same elements as those of FIG. 1 described above are denoted by the same reference numerals, and the description of the constituent elements of such reference numerals is omitted to avoid redundant description.

In the figure, a capacitor C1 (30)
(Hereinafter, simply referred to as C1 (30)) and the capacitor C2 (40) (hereinafter, simply referred to as C2 (40)),
Induction electrode (11) embedded in the induction electrode side substrate (10)
And the cathode of the organic EL element laid on the panel side transparent substrate (20), that is, the metal electrode (22). That is, the induction electrode (11) confronts the cathode (metal electrode (22)) of the organic EL element by enclosing the insulating sealing film (21). Therefore, when the induction electrode side substrate (10) is brought into contact with the panel side transparent substrate (20), the induction electrode (11) and the metal electrode (2) of the organic EL element are
2) and 2 are two electrodes, and the insulating sealing film (21) is a dielectric sandwiched between both electrodes to form a kind of capacitor. In FIG. 2, such capacitors are represented as C1 and C2.

Further, between the anode (24) and the cathode (22) of the organic EL element provided on the panel side transparent substrate (20), the rectification similar to that of a general diode element is taken into consideration in view of its electrical characteristics. Have characteristics. Therefore, in FIG. 2, these are referred to as EL1 (50) and EL2 (60), respectively,
It is marked with the symbol of a general diode. The metal electrode (22) forming the above-mentioned C1 (30) is EL1 (5).
It goes without saying that the metal electrode (22) which also serves as the cathode of 0) and which similarly constitutes C2 (40) also serves as the cathode of EL2 (60). Furthermore, EL1 (50) and EL2
(60) is connected by the electrode connecting wire (25) as described above.
Since the respective anodes and cathodes are electrically connected to each other, the equivalent circuit thereof is a wiring line as shown in FIG.

Next, for convenience of explanation of the operation of this embodiment, the equivalent circuit of FIG. 2 is further divided into two operation modes and shown in FIG. First, FIG. 3A shows the operation of the equivalent circuit in the operation mode 1. The operation mode 1 is the phase of the AC voltage supplied from the drive power supply circuit 13 and is C1 (3
0) refers to an operation mode in which a plus appears on the side connected and a minus appears on the side connected to C2 (40). Therefore, in the operation mode 1, charges of opposite polarity are induced by the electrostatic induction phenomenon on the electrodes on the opposite side of each capacitor, that is, the electrodes on the side to which the organic EL element pair is connected. In other words, C1 (30) is minus, C2 (40)
A positive charge will be induced in each.

Then, the positive charge induced in C2 (40) passes from the anode of EL1 (50) to the cathode of C1 (3).
0), and the negative charge induced in C1 (30) is transferred from the cathode of EL1 (50) through the anode to C2.
Moving to (40), each induced charge is neutralized. In this process, a so-called forward current flows through the EL1 (50), which causes the EL1 (50) to emit light. Since the direction of EL2 (60) is opposite to the forward current, EL2 (6)
No charge transfer through 0) occurs. That is, EL2
No current flows through (60) and EL2 (60) does not emit light.

Next, FIG. 3B shows the operation of the equivalent circuit in the operation mode 2. In contrast to the operation mode 1 described above, the phase of the AC voltage supplied from the driving power supply circuit 13 is negative and C2 (40) is connected to the side to which the C1 (30) is connected. This is an operating mode in which a plus appears on the side. Therefore, in this case, C1 (3
A positive charge is induced in 0) and a negative charge is induced in C2 (40).

Then, the positive charge induced in C1 (30) passes from the anode of EL2 (60) to the cathode of C2 (4).
0) and the negative charge induced in C2 (40) is transferred from the cathode of EL2 (60) to the anode to C1 (30).
To be neutralized. As a result, a forward current flows through the EL2 (60) as in the operation mode 1, and the EL2 (60) emits light. In this case, the direction of EL1 (50) is opposite to the forward current, so that no current flows through EL1 (50) and EL1 (50) does not emit light.

The operation mode 1 and the operation mode 2 described above are repeatedly performed by the AC voltage supplied from the drive power supply circuit 13 in accordance with the oscillation cycle thereof. Along with this, EL1 (50) and EL2 (60) emit light alternately, and if the oscillation frequency of the AC voltage is sufficiently high, the light emitting pixel composed of EL1 (50) and EL2 (60) continuously emits light. Will look like.

A second embodiment of the organic EL display panel according to the present invention is shown in the block diagram of FIG. In addition,
The configuration of this embodiment and the operating principle thereof are the same as those of the first embodiment described above, and therefore their explanations are omitted. In this example, as is clear from FIG. 4, the area of the cathode (metal electrode (22)) of the organic EL element was changed to the anode (transparent electrode (2
4)), and correspondingly, the area of the induction electrode (11) provided facing the metal electrode is also expanded accordingly.

Generally, the capacitance of a capacitor increases in proportion to its electrode area, and the amount of electric charges induced in one electrode by the electrostatic induction phenomenon also increases accordingly. Therefore, in the embodiment shown in FIG. 4, the amount of neutralizing charges transferred through the organic EL element is also increased as compared with the first embodiment. As a result, the value of the forward current flowing through the organic EL element increases, so that the emission brightness of the organic EL element can be increased.

Further, since the electrode areas of the capacitors C1 and C2 are expanded, when the induction electrode side substrate (10) is brought into contact with the panel side transparent substrate (20), the alignment process between the two is simplified. Therefore, the manufacturing cost of the display panel can be reduced. Also, the second
As a modified example of the above embodiment, as shown in FIG.
On the cathode of the device (metal electrode (22)), another additional electrode (2
6) may be electrically connected and provided. By adopting such a configuration, it is possible to further enhance the effect obtained in the second embodiment described above. Note that FIG.
In the embodiment shown in FIG. 3, the capacitor between the driving power supply circuit 13 and the organic EL element is the induction electrode (11) and the additional electrode (2).
It goes without saying that it is configured between 6) and.

Next, a third embodiment of the organic EL display panel according to the present invention is shown in the block diagram of FIG. In this embodiment, one of the pair of organic EL elements is a normal rectifying diode (70).
It is characterized in that it is replaced with. As described above, since the organic EL element also has the same rectifying characteristic as the diode, the operation in this embodiment is the same as that of the first and second embodiments described above even with such a configuration.

However, the organic EL element has an extremely large forward voltage drop as compared with a general rectifying diode. For example, the forward voltage drop value (Vdo
f) is usually about Vdof = 0.6V, whereas the forward voltage drop value (Velf) of the organic EL element is Velf.
In many cases, it is about 6 to 8V. The forward voltage drop value of an element having a rectifying characteristic refers to a minimum forward voltage applied when a forward current is applied to the element.

That is, as shown in FIG. 7A, when one pixel of the display panel according to the present invention is composed of a pair of elements using an organic EL, the driving power supply circuit required in the operation mode 1 described above. The voltage amplitude value of 13 must be larger than the forward voltage drop value (Velf) of EL1 (50), and the voltage amplitude value required in the operation mode 2 is similarly EL2 (60). Forward voltage drop value (Ve
It should be larger than lf).

Therefore, in this case, the voltage waveform of the AC voltage supplied from the driving power supply circuit 13 is, as shown in FIG. 7A, a peak-to-peak value of the voltage waveform, Velf + Vel.
A voltage of f = 2Velf or higher is required. In the figure, the waveform of the AC voltage is marked with a rectangular wave for convenience of explanation. On the other hand, if one of the element pairs is replaced with a rectifying diode as in the present embodiment, as shown in FIG. 7B, the AC voltage supplied from the drive power supply circuit 13 to the element pair has a voltage waveform. Peak-to-peak value of Velf + V
Since the voltage of dof≈Velf is sufficient, the output voltage amplitude from the driving power supply circuit 13 can be reduced.

The rectifying diode used in this embodiment may be a conventional silicon semiconductor diode, but it may be an organic diode composed of a junction of a P-type organic layer and an N-type organic layer, or an organic layer. And metal materials or IT
A Schottky diode formed by joining with a transparent electrode layer such as O may be used. By adopting such a configuration, such an organic diode or Schottky diode can be formed at the same time as the organic EL element in the manufacturing process of the organic EL element, and the light emission sealed with an insulating film without increasing the thickness thereof. It becomes possible to manufacture panels.

By the way, in the case of this embodiment, the above-mentioned first
Also, since the number of light emitting elements is halved compared to the second embodiment, a physical decrease in brightness cannot be denied. However, for example, by taking measures such as increasing the oscillation frequency of the AC voltage supplied from the driving power supply circuit 13, the number of times the light emitting element is excited can be increased and a desired luminance can be ensured.

In the first to third embodiments described above, the induction electrode side substrate (10) is replaced with the panel side transparent substrate (2).
0) is shown separately. This is because the induction electrode side substrate (10) is manufactured in a separate process from the panel side transparent substrate (20), and when both members are completed, the panel side transparent substrate (20).
It is shown that a display panel in which both members are integrated can be created by pasting or pressing the induction electrode side substrate (10) on the above.

However, these embodiments are not limited to such cases. For example, the induction electrode (1) is formed on the insulating sealing film (21) of the panel side transparent substrate (20).
1) may be directly formed by means such as vapor deposition or printing.

[0036]

As described above in detail, according to the present invention, it is not necessary to directly draw the electrode from the light emitting element of the display panel, so that the light emitting element is completely hermetically sealed and the reliability of the display panel is improved. . Moreover, since the drive unit and the panel unit can be manufactured independently, the manufacturing process is simplified. Further, even in a large-area display panel, a wasteful space due to wiring is not needed, and the display panel can be downsized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a structure of a first embodiment according to the present invention.

FIG. 2 is a configuration diagram showing an equivalent circuit in the embodiment shown in FIG.

FIG. 3 is an operation explanatory view explaining a function of the equivalent circuit shown in FIG.

FIG. 4 is a configuration diagram showing a structure of a second embodiment according to the present invention.

FIG. 5 is a configuration diagram showing a structure of a modification example of the second embodiment shown in FIG.

FIG. 6 is a configuration diagram showing an equivalent circuit of a third exemplary embodiment of the present invention.

FIG. 7 is an operation explanatory view explaining a difference in operation in the equivalent circuits of the embodiments shown in FIGS. 2 and 6;

[Explanation of symbols]

10 ... Induction electrode side substrate 11 ... Induction electrode 12 ... Connection line 13 ... Driving power supply circuit 20 ... Transparent substrate on panel side 21 ... Insulation sealing film 22 ... Metal electrode (cathode) 23 ... Organic functional layer 24 ... Transparent electrode (anode) 25 ... Electrode connecting wire 26 ... Additional electrode (metal electrode) 30 ... Capacitor C1 40 ... Capacitor C2 50 ... Organic EL element EL1 60 ... Organic EL element EL2 70 ... Diode

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/14 H05B 33/26 Z 33/26 H01L 29/28 F term (reference) 3K007 AB11 AB18 BA06 BB02 CB01 CC05 DA01 DB03 EB00 FA02 5C094 AA15 AA38 AA48 BA27 CA20 DA15 DB03 DB04 EA04 EA05 EB02 FA01 FA02 FB01 FB20 GA10

Claims (5)

[Claims] 1. An organic EL display panel, which uses an organic EL element as a pixel, excites and emits the organic EL element with a drive voltage supplied from a drive power supply circuit, and displays an image on the panel. A pair of organic EL element pairs, a transparent substrate that carries the organic EL element pair from its anode side, an insulating sealing film that covers the organic EL element pair and insulates and seals the organic EL element pair on the transparent substrate, At least a pair of drive electrodes facing each of the cathodes of the organic EL element pair with an insulating sealing film interposed therebetween, and one anode of the light emitting element pair and the other cathode are connected to each other. An organic EL display panel characterized by the above. 2. The area of each cathode of the pair of organic EL elements is
The organic EL display panel according to claim 1, which is larger than each of the anodes. 3. An electrode pair comprising another electrode connected to each cathode of the organic EL element pair is further provided, and the electrode pair faces the drive electrode pair with the insulating sealing film interposed therebetween. The organic EL display panel according to claim 1, wherein: 4. The organic EL display panel according to claim 1, wherein one organic EL element of the organic EL element pair is replaced with a diode element. 5. The organic EL display panel according to claim 1, wherein one organic EL element of the organic EL element pair is replaced with an organic diode element.