JP4473472B2 - Electrostatic induction driven organic electroluminescence display panel - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
An organic electroluminescence display panel (hereinafter simply referred to as “organic EL display panel”) displays images, characters, and the like using light-emitting pixels as organic EL elements. In other words, organic EL elements are laid in a matrix on the display panel, and each pixel is excited and emitted by a drive voltage supplied from a drive power supply circuit to execute display processing.
[0003]
In a conventional organic EL display panel, a large number of organic EL elements are generally laid on a transparent substrate such as glass or plastic film, and a silicon oxide film or the like is used 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 film. For this reason, in order to connect the organic EL element and the drive power supply circuit, an electrode is directly drawn out from the organic EL element on the panel, and this is extended to the drive power supply circuit outside the display panel through the outer periphery of the insulating sealing film. It is necessary to route.
[0004]
Conventionally, in order to achieve such an object, the connection electrode is once drawn out of the insulating sealing film to form a connection pattern, and further, an external conductive-side connection pattern is formed via an anisotropic conductive film such as anisolm. The structure which performs the electrical connection of was adopted.
However, such a structure has a drawback in that the manufacturing process of the display panel becomes complicated because the thermocompression treatment is required when forming the electrical insulation by the anisotropic conductive film. Further, 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 re-adhere the anisotropic conductive film.
[0005]
In addition, since the electrodes are extracted 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. For this reason, when electrodes are drawn from all the organic EL elements constituting the display panel, a dead space is generated in the periphery of the display panel, which increases the area of the entire display panel.
[0006]
[Problems to be solved by the invention]
The present invention has been made to solve such a problem, and enables a power supply from a drive power supply circuit to an organic EL element without wiring to an electrode of the organic EL element through an insulating sealing film. The purpose is to provide.
[0007]
[Means for Solving the Problems]
The present invention is an organic EL display panel that uses an organic EL element as a pixel, excites the organic EL element with a driving voltage supplied from a driving power supply circuit, and displays an image on the panel.
At least a pair of organic EL element pairs per pixel, a transparent substrate carrying the organic EL element pair from its anode side, and an insulating seal that covers and covers the organic EL element pair on the transparent substrate A coating, and at least a pair of drive electrodes facing each of the cathodes of the organic EL element pair across the insulating sealing coating,
One anode of the light emitting element pair and the other cathode are connected to each other.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of an organic EL display panel according to the present invention is shown in the block diagram of FIG.
In FIG. 1, an induction electrode side substrate (10) is an insulating substrate formed of a polymer material such as plastic, for example, and an induction electrode (for each pixel provided on the panel side substrate described later) 11) is buried. The induction electrode (11) is connected to a drive power supply circuit (13) provided outside the panel via a connection line (12).
[0009]
The drive power supply circuit (13) is an oscillation circuit that generates a predetermined AC voltage, and the oscillation waveform may be a waveform such as a general sine wave, other rectangular waves, and triangular waves. Various parameters relating to the oscillation conditions such as the frequency and amplitude of the oscillation waveform can be set to various values based on the relationship with the emission luminance required for the organic EL element provided on the panel side substrate described later.
[0010]
In FIG. 1, only two electrodes are shown as induction electrodes facing one pixel of the panel side substrate. However, the present embodiment is not limited to this, and the number of electrodes is provided on the panel side substrate. This corresponds to the number of organic EL elements constituting one pixel. However, even when there are two or more electrodes, a plurality of electrodes are connected in parallel to form two electrode groups, and the point of connecting the electrode group pair to the drive power supply circuit (13) is shown in FIG. It is the same as the form.
[0011]
The panel-side transparent substrate (20) is a transparent substrate formed using, for example, a polymer (plastic) film such as polycarbonate or polyethersulfone, glass, or the like, and a pixel made of an organic EL element is formed on the substrate. It is 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 of the panel surface.
[0012]
As shown in FIG. 1, one organic EL element has a structure in which a transparent electrode (24) and a metal electrode (22) sandwich an organic functional layer (23). Here, the organic functional layer is a single layer structure having only a light emitting layer, or a two-layer structure composed of an organic hole transport layer and a light emitting layer, or a three layer composed of an organic hole transport layer, a light emitting layer and an organic electron transport layer. The structure means a laminated structure composed of a plurality of layers in which an electron or hole injection layer or a carrier block layer is inserted between these appropriate layers.
[0013]
The transparent electrode (24) is a light-transmissive electrode made of an indium series oxide such as indium / tin oxide (ITO), for example, and serves as an anode (anode) of the organic EL element. On the other hand, the metal electrode (22) is made of a metal such as aluminum and functions as a cathode (cathode) of the organic EL element.
The organic functional layer (23) exhibits a light emission phenomenon when excited by the power supply from the upper and lower electrodes, and this light emission is transmitted to the outside of the display panel through the transparent electrode (24) and the transparent substrate (20). The
[0014]
In this embodiment, as shown in FIG. 1, one pixel is composed of two left and right organic EL elements, and the anode and cathode of each element are connected to each other using an electrode connection line (25). It has become. The electrode connection line (25) may be configured by connection by normal wire bonding, or a protrusion is provided on the metal electrode (22) of each element, and the protrusion is extended to the other element. It is good also as a structure vapor-deposited on this transparent electrode (24).
[0015]
In FIG. 1, one pixel is composed of two organic EL elements, but this embodiment is not limited to this, and one pixel is composed of two or more organic EL elements. May be. 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 above-described positive / cathode interconnection is performed for each organic EL element pair.
[0016]
In this embodiment, as is clear from FIG. 1, an insulating sealing film (21) made of a silicon oxide layer such as SiON or SiOx is provided so as to cover the entire organic EL element pair, and the organic EL element pair is made transparent. The substrate (20) is completely hermetically sealed. That is, the electrode of the organic EL element is not drawn out through the insulating sealing film (21). For this reason, the formation process of the insulation sealing film (21) with respect to the panel side transparent substrate (20) becomes easy, and the reliability of the insulation sealing process is also improved.
[0017]
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 components for one pixel in FIG. In FIG. 2, the same components as those in FIG. 1 described above are denoted by the same reference numerals, and the description of the components having the same reference numerals is omitted to avoid the redundant description.
[0018]
In the figure, a capacitor C1 (30) (hereinafter simply referred to as C1 (30)) and a capacitor C2 (40) (hereinafter simply referred to as C2 (40)) are embedded in the induction electrode side substrate (10). The capacitor is formed between the induction electrode (11) 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) is opposed to the cathode (metal electrode (22)) of the organic EL element with the insulating sealing film (21) interposed therebetween. Accordingly, 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 (22) of the organic EL element are made into two electrodes, and the insulating sealing film A type of capacitor is formed in which (21) is a dielectric sandwiched between both electrodes. In FIG. 2, such capacitors are represented as C1 and C2.
[0019]
In addition, between the anode (24) and the cathode (22) of the organic EL element provided on the panel-side transparent substrate (20), the same rectification characteristic as that of a general diode element is obtained in view of its electrical characteristics. . Therefore, in FIG. 2, these are referred to as EL1 (50) and EL2 (60), respectively, and are denoted by general diode symbols.
The metal electrode (22) constituting the C1 (30) described above also serves as the cathode of the EL1 (50). Similarly, the metal electrode (22) constituting C2 (40) also serves as the cathode of the EL2 (60). Needless to say. Further, since EL1 (50) and EL2 (60) are electrically connected to each other by the electrode connection line (25) as described above, their equivalent circuits are shown in FIG. Wiring will be done.
[0020]
Next, for convenience of explanation of the operation in the present embodiment, the equivalent circuit of FIG. 2 is further divided into two operation modes and shown in FIG.
First, FIG. 3A shows the function of the equivalent circuit in the operation mode 1. The operation mode 1 is an operation mode in which the phase of the AC voltage supplied from the drive power supply circuit 13 is positive on the side where the C1 (30) is connected and negative on the side where the C2 (40) is connected. Say. Therefore, in the operation mode 1, charges of opposite polarity are induced by the electrostatic induction phenomenon on the opposite electrode of each capacitor, that is, the electrode on the side where the organic EL element pair is connected. That is, a negative charge is induced in C1 (30) and a positive charge is induced in C2 (40).
[0021]
Then, the positive charge induced in C2 (40) moves from the anode of EL1 (50) through the cathode to C1 (30), and the negative charge induced in C1 (30) becomes EL1 (50). Each induced charge is neutralized by moving from the cathode to the C2 (40) via the anode. In this process, a so-called forward current flows in EL1 (50), and EL1 (50) emits light. Note that the direction of EL2 (60) is opposite to the forward current, so that no charge transfer occurs through EL2 (60). That is, no current flows through EL2 (60), and EL2 (60) does not emit light.
[0022]
Next, FIG. 3B shows the function of the equivalent circuit in the operation mode 2. In the operation mode 2, the phase of the AC voltage supplied from the drive power supply circuit 13 is negative, and C2 (40) is connected to the side to which C1 (30) is connected, contrary to the previous operation mode 1. An operation mode in which a plus appears on the side. Therefore, in this case, a positive charge is induced in C1 (30) and a negative charge is induced in C2 (40) on the opposite electrode of each capacitor due to the electrostatic induction phenomenon.
[0023]
The positive charge induced in C1 (30) moves from the anode of EL2 (60) to the C2 (40) through the cathode, and the negative charge induced in C2 (40) becomes the cathode of EL2 (60). Then, it moves to C1 (30) through the anode to neutralize each induced charge. As a result, the forward current flows in EL2 (60) as in the operation mode 1, and EL2 (60) emits light. In this case, since the direction of EL1 (50) is opposite to the forward current, no current flows through EL1 (50), and EL1 (50) does not emit light.
[0024]
The operation mode 1 and the operation mode 2 described above are repeatedly performed according to the oscillation cycle by the AC voltage supplied from the drive power supply circuit 13. Accordingly, EL1 (50) and EL2 (60) emit light alternately, and if the oscillation frequency of the AC voltage is sufficiently high, the light-emitting pixels composed of EL1 (50) and EL2 (60) emit light continuously. Will look like this.
[0025]
Next, a second embodiment of the organic EL display panel according to the present invention is shown in the block diagram of FIG. The configuration and the operating principle of this embodiment are the same as those of the first embodiment described above, and a description thereof will be omitted.
As is clear from FIG. 4, the present example expands the area of the cathode (metal electrode (22)) of the organic EL element as compared with the anode (transparent electrode (24)), and accordingly, the metal electrode and The area of the induction electrode (11) provided oppositely is also characterized by an expansion.
[0026]
In general, the capacitance of a capacitor increases in proportion to its electrode area, and accordingly, the amount of electric charge induced in one electrode by an electrostatic induction phenomenon also increases. Therefore, in the embodiment shown in FIG. 4, the amount of neutralizing charge that moves through the organic EL element also increases compared to the first embodiment. As a result, the value of the forward current flowing through the organic EL element is increased, so that the light emission luminance of the organic EL element can be increased.
[0027]
Furthermore, 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), it is possible to simplify the alignment processing required between them. Therefore, the manufacturing cost of the display panel can be reduced.
Further, as a modification of the second embodiment, as shown in FIG. 5, another additional electrode (26) is electrically connected to the cathode (metal electrode (22)) of the organic EL element. May be. By adopting such a configuration, it is possible to further enhance the effects obtained in the second embodiment described above. In the embodiment shown in FIG. 5, it goes without saying that the capacitor between the drive power supply circuit 13 and the organic EL element is configured between the induction electrode (11) and the additional electrode (26).
[0028]
Next, a third embodiment of the organic EL display panel according to the present invention is shown in the block diagram of FIG. This embodiment is characterized in that one of the organic EL element pairs is replaced with a normal rectifying diode (70). As described above, since the organic EL element also has the same rectification characteristics as the diode, the operation in the present embodiment is the same as that in the first and second embodiments described above even in such a configuration.
[0029]
However, the organic EL element has an extremely large forward voltage drop compared to a general rectifying diode. For example, the forward voltage drop value (Vdof) of the rectifying diode is normally around Vdof = 0.6V, whereas the forward voltage drop value (Velf) of the organic EL element is around Vel = 6-8V. There are many. Note that the forward voltage drop value of an element having rectifying characteristics refers to a minimum forward voltage applied when a forward current flows through the element.
[0030]
That is, as shown in FIG. 7 (a), when one pixel of the display panel according to the present invention is composed of an element pair using an organic EL, the voltage of the drive power circuit 13 required in the operation mode 1 described above. The amplitude value needs to be larger than the forward voltage drop value (Velf) of EL1 (50), and the voltage amplitude value required in the operation mode 2 is also the forward direction of EL2 (60). It is necessary to make it larger than the voltage drop value (Velf).
[0031]
Therefore, in this case, the voltage waveform of the AC voltage supplied from the drive power supply circuit 13 requires a voltage equal to or higher than Vel + Velf = 2Velf in the peak-to-peak value of the voltage waveform as shown in FIG. In the figure, for convenience of explanation, the waveform of the AC voltage is indicated by a rectangular wave.
On the other hand, when one of the element pairs is replaced with a rectifying diode as in this embodiment, the AC voltage supplied to the element pair from the drive power supply circuit 13 is a voltage waveform as shown in FIG. Thus, the voltage of Vel + Vdof≈Vel is sufficient at the peak-to-peak value, and the output voltage amplitude from the drive power supply circuit 13 can be reduced.
[0032]
The rectifying diode used in this embodiment may be a conventional silicon semiconductor diode, but this is an organic diode formed by joining a P-type organic layer and an N-type organic layer, or an organic layer and a metal material. Alternatively, a Schottky diode formed by bonding with a transparent electrode layer such as ITO may be used. By adopting such a configuration, such an organic diode or a Schottky diode can be formed simultaneously with the organic EL element in the manufacturing process of the organic EL element, and light emission sealed with an insulating film without increasing its thickness. Panels can be manufactured.
[0033]
By the way, in the case of the present embodiment, the number of light emitting elements is halved as compared with the first and second embodiments described above, and thus the physical luminance cannot be reduced. However, for example, by taking measures such as increasing the oscillation frequency of the AC voltage supplied from the drive power supply circuit 13, the number of excitations of the light emitting element increases, and desired luminance can be ensured.
[0034]
In the first to third embodiments described above, the induction electrode side substrate (10) is shown separated from the panel side transparent substrate (20). This is because the induction electrode side substrate (10) is manufactured separately from the panel side transparent substrate (20), and when both members are completed, the induction electrode side substrate (10) is placed on the panel side transparent substrate (20). It shows that a display panel in which both members are integrated can be created by pasting or pressing.
[0035]
However, these examples are not limited to such cases. For example, the induction electrode (11) is vapor-deposited or printed on the insulating sealing film (21) of the panel-side transparent substrate (20). It is good also as a structure formed directly by.
[0036]
【The invention's effect】
As described above in detail, according to the present invention, since it is not necessary to directly pull out the electrode from the light emitting element of the display panel, the hermetic sealing of the light emitting element becomes complete and the reliability of the display panel is improved. Further, since the drive unit and the panel unit can be manufactured independently, the manufacturing process is simplified. Further, even in the case of a display panel having a large area, useless space due to wiring drawing is not required, and the display panel can be miniaturized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the 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. 1;
FIG. 3 is an operation explanatory diagram for explaining the operation of the equivalent circuit shown in FIG. 2;
FIG. 4 is a block diagram showing the structure of a second embodiment according to the present invention.
FIG. 5 is a configuration diagram showing a structure of a modified example of the second embodiment shown in FIG. 4;
FIG. 6 is a block diagram showing an equivalent circuit of a third embodiment according to the present invention.
7 is an operation explanatory diagram for explaining a difference in operation in the equivalent circuit of the embodiment shown in FIGS. 2 and 6. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Induction electrode side board | substrate 11 ... Induction electrode 12 ... Connection line 13 ... Drive power supply circuit 20 ... Panel side transparent substrate 21 ... Insulation sealing film 22 ... Metal electrode (cathode)
23 ... Organic functional layer 24 ... Transparent electrode (anode)
25 ... Electrode connection line 26 ... Additional electrode (metal electrode)
30: Capacitor C1
40: Capacitor C2
50 ... Organic EL element EL1
60 ... Organic EL element EL2
70: Diode

Claims (5)

An organic EL display panel that uses an organic EL element as a pixel, causes the organic EL element to emit light with a driving voltage supplied from a driving power supply circuit, and displays an image on the panel.
At least one pair of organic EL elements per pixel;
A transparent substrate carrying the organic EL element pair from its anode side;
An insulating sealing film covering the organic EL element pair and insulatingly sealing it on the transparent substrate;
Including at least one pair of drive electrodes facing each of the cathodes of the pair of organic EL elements across the insulating sealing film,
An organic EL display panel, wherein one anode and the other cathode of the light emitting element pair are connected to each other. 2. The organic EL display panel according to claim 1, wherein an area of each cathode of the organic EL element pair is larger than each anode. An electrode pair consisting of separate electrodes connected to each cathode of the organic EL element pair is further provided,
The organic EL display panel according to claim 1, wherein the electrode pair is opposed to the drive electrode pair with the insulating sealing film interposed therebetween. 2. The organic EL display panel according to claim 1, wherein one organic EL element of the pair of organic EL elements is replaced with a diode element. The organic EL display panel according to claim 1, wherein one organic EL element of the pair of organic EL elements is replaced with an organic diode element.

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