JP2003323988A - Light emitting device and electric equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device using a light emitting element for long-life stable drive and an electric equipment using the same. <P>SOLUTION: The light emitting device comprises the light emitting element having a organic compound layer for developing light emission by applying voltage between a first electrode and a second electrode and bias applying means for applying a forward bias for light emission of the light emitting element and a reverse bias. The bias applying means is operated so that an absolute value for the maximum voltage Vf of the forward bias is larger than an absolute value for the maximum voltage Vr of the reverse bias in a cycle where the forward bias and the reverse bias are applied alternately. At this time, the Vr is preferably a quarter or greater of the Vf. A time Tr for applying the reverse bias in an alternating current cycle is preferably equal to or longer than a time Tf for applying the forward bias. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device having an anode and a cathode, and a layer containing an organic compound that emits light when an electric field is applied (hereinafter referred to as "organic compound layer"). The present invention particularly relates to a light emitting element having a longer driving life than ever, and a light emitting device using the organic light emitting element.

[0002]

2. Description of the Related Art An organic light emitting device is a device that emits light when an electric field is applied. The emission mechanism is that when an organic compound layer is sandwiched between electrodes and a voltage is applied, electrons injected from the cathode and holes injected from the anode are recombined at the emission center in the organic compound layer and excited. (Hereinafter, referred to as “molecular exciton”) and emits energy by releasing energy when the molecular exciton returns to the ground state.

The types of molecular excitons formed by an organic compound can be a singlet excited state and a triplet excited state. Here, it is assumed that either excited state contributes to light emission. .

In such an organic light emitting device, normally,
The organic compound layer is formed as a thin film having a thickness of less than 1 μm.
Further, since the organic light emitting element is a self-luminous element in which the organic compound layer itself emits light, a backlight as used in a conventional liquid crystal display is not necessary.
Therefore, it is a great advantage that the organic light emitting device can be manufactured to be extremely thin and lightweight.

Further, in an organic compound layer of, for example, about 100 to 200 nm, the time from injection of carriers to recombination is about several tens of nanoseconds considering the carrier mobility of the organic compound layer. Even if the process from recombination to light emission is included, light is emitted within a microsecond order. Therefore, one of the features is that the response speed is very fast.

Further, since the organic light emitting device is a carrier injection type light emitting device, it can be driven by a DC voltage,
Noise is unlikely to occur. Regarding the driving voltage, first, make the organic compound layer a uniform ultrathin film with a thickness of about 100 nm, and
100 cd / m ^{2 at} 5.5 V by selecting the electrode material that reduces the carrier injection barrier to the organic compound layer and by introducing the single hetero structure (double layer structure).
Sufficient brightness was achieved (see Non-Patent Document 1, for example).

[0007]

[Non-Patent Document 1] C.I. W. Tan (C.W. Tang)
Applied Physics Letters, 1987,
Vol. 51, No. 12,913-915

Due to such characteristics of thinness and light weight, high-speed response and direct current low voltage driving, the organic light emitting device has been attracting attention as a next-generation flat panel display device. In addition, since it is a self-luminous type and has a wide viewing angle, it has relatively good visibility and is considered to be effective as an element used for a display screen of a mobile device.

By the way, a major problem of such an organic light emitting device is the reliability of the device. In terms of reliability, the deterioration of luminance with time is remarkable, and a great improvement is required. Further, since it is an ultrathin film device, it is necessary to prevent defects such as morphology and point defects of the thin film, or short circuit of the element due to unevenness.

It is considered that the deterioration of luminance with time is basically a phenomenon derived from the material used, but it is possible to extend the half-life of luminance depending on the driving method of the element. For example, by inserting copper phthalocyanine as a hole injecting layer and further driving with a rectangular wave alternating current (constant current in forward bias (forward bias), constant voltage in reverse bias (reverse bias)) instead of direct current. There is an example in which the half-life of luminance is greatly improved (for example, see Non-Patent Document 2).

[0011]

[Non-Patent Document 2] A. VanSlyke et al., Outside 2
Name, Applied Physics Letters, 1996,
Vol. 69, No. 15,2160-2162

Non-Patent Document 2 succeeds in extending the luminance half-life to 4000 hours at an initial luminance of 510 cd / m ² .
The reasons for this include the excellent hole injection characteristics of copper phthalocyanine, which is the hole injection layer, the good heat resistance of NPB, which is the hole transport layer, and the fact that space charge could be eliminated by AC drive. There is. It should be noted that when the organic light emitting element is normally driven with a constant current, the driving voltage gradually rises as the luminance deteriorates, but it is shown that the driving voltage rise is suppressed by AC driving. .

It has been reported that such AC driving can eliminate defects such as short circuit of the element due to morphology and point defects (see, for example, Patent Document 1). In Patent Document 1, the element lives of DC drive and AC drive are compared, and in the case of DC drive, a short time (200 to 300
It is often pointed out that a short circuit is often seen during (time).

[0014]

[Patent Document 1] Japanese Patent Laid-Open No. 8-180972

As a method of preventing a short circuit of the element due to the unevenness of the electrode, for example, a method of providing a conductive polymer buffer layer on the electrode has been devised (for example, see Non-Patent Document 3). Non-Patent Document 3 states that the surface roughness of ITO as an anode can be solved by introducing a polymer anode buffer layer, which leads to a reduction in short-circuit defects.

[0016]

[Non-patent document 3] Yoshiharu Sato, "Journal of the Organic Physics and Bioelectronics Subcommittee of the Japan Society of Applied Physics", 2000
Year, Vol.11, No.1, p.86-99

As described above, in order to improve the reliability of the organic light emitting device, not only the improvement of the material itself but also the driving method and the device structure are taken.

[0018]

A characteristic of the AC drive described in the above-mentioned Patent Document 1 is that the voltage applied to the device during reverse bias (hereinafter referred to as "Vr").
Is equal to or greater than the voltage applied to the device during forward bias (hereinafter referred to as “Vf”), and
The duration during reverse bias (hereinafter referred to as “Tr”) is shorter than the duration during forward bias (hereinafter referred to as “Tf”). That is, Vf ≦ Vr, Tf> Tr
Is. The voltages here are all treated as positive values.

Considering the effect that the reverse bias eliminates the accumulation of space charge, it is more effective that Vf ≦ Vr. However, in this case, it is necessary to pay attention to the dielectric breakdown strength of the element. That is, Vr must be set to be smaller than the dielectric breakdown voltage Vb. That is, Vf ≦ Vr <Vb.

However, when the luminance deteriorates with time, the current efficiency (ratio of luminance to current density) itself decreases as compared with the initial stage of driving, in other words, the leakage current that does not contribute to light emission increases. Vb in the long run
There is a possibility that dielectric breakdown will occur at a voltage lower than that.

That is, in the case of the AC driving method as described above, the half-life of the luminance can be extended as compared with DC, and a short circuit or the like that occurs in the initial stage of driving can be prevented. Even if the reverse bias voltage of Vr, which should not have been destroyed, there is a possibility of dielectric breakdown.

Therefore, in the present invention, the AC driving method of the light emitting element, which can alleviate the deterioration of the brightness and prevent the short circuit in the initial stage of driving, is further improved as compared with the conventional method, and is caused by the dielectric breakdown in the long term. It is an object of the present invention to provide a driving method that prevents destruction of elements. Another object of the present invention is to provide a light emitting device and a method for driving the light emitting device in which the deterioration of the luminance is small and the yield is high by combining the improved AC driving means and the light emitting element.

Further, it is an object of the present invention to provide an electric appliance which is superior in long-term reliability to the conventional one by manufacturing the electric appliance using the light emitting device.

[0024]

The present invention provides a light emitting device provided with an organic compound layer capable of emitting light by applying a voltage between a first electrode and a second electrode, and the organic light emitting device. A forward bias (forward bias) and a bias applying means for applying a reverse bias (reverse bias) having a polarity opposite to that of the forward bias, wherein the bias applying means comprises the forward bias. And in a cycle in which the reverse bias is alternately applied, the absolute value of the maximum voltage of the forward bias is
It is characterized in that it operates so as to be larger than the absolute value of the maximum voltage of the reverse bias. At this time, the absolute value of the maximum voltage of the reverse bias is preferably ¼ or more of the absolute value of the maximum voltage of the forward bias.

The present invention further includes a light emitting element provided with an organic compound layer capable of emitting light when a voltage is applied between the first electrode and the second electrode, and a forward bias (forward bias) is applied to the light emitting element. Bias) and a reverse bias (reverse bias) having a polarity opposite to that of the forward bias, the method of driving a light emitting device, wherein the forward bias and the reverse bias are alternately applied within a cycle. The absolute value of the maximum voltage of the forward bias is higher than the absolute value of the maximum voltage of the reverse bias. At this time, the absolute value of the maximum voltage of the reverse bias is preferably ¼ or more of the absolute value of the maximum voltage of the forward bias.

Further, it is preferable that the time for applying the reverse bias in the cycle is the same as or longer than the time for applying the forward bias. In this case, since the amount of light emission and the light emission time are reduced, it is preferable that the light-emitting element used emit light from a triplet excited state. Alternatively, it is preferable to emit light from rare earth metal ions.

Since almost no current flows when the reverse bias is applied, a certain voltage may be applied for the reverse bias. The forward bias may be a constant voltage, but driving in which a constant current flows is more preferable.

Therefore, the present invention is characterized in that both the forward bias and the reverse bias are applied so that a constant voltage is applied to the light emitting element. Further, the forward bias is applied so that a constant current flows to the light emitting element, and the reverse bias is applied so that a constant voltage is applied to the light emitting element.

By the way, it is preferable to use a polymer compound as the organic compound layer in the present invention. Therefore, the present invention is characterized in that the organic compound layer contains a polymer compound that emits light.

Further, in the present invention, it is preferable to provide a layer having a certain degree of conductivity between the organic compound layer and the electrode.

Therefore, in the present invention, a conductive layer containing an inorganic compound is provided between the organic compound layer and the first electrode or between the organic compound layer and the second electrode. And In this case, the conductivity of the conductive layer containing the inorganic compound is preferably 10 ^{-1 0} S / cm or more.

Further, a layer containing a conductive polymer compound is provided between the organic compound layer and the first electrode or between the organic compound layer and the second electrode. To do. In particular, from the viewpoint of improving conductivity, the layer containing the conductive polymer compound preferably further has an acceptor or a donor for the conductive polymer. Also in this case, the conductivity of the layer containing the conductive polymer compound is preferably 10 ^{-1 0} S / cm or more.

Further, a layer containing a π-conjugated organic compound is provided between the organic compound layer and the first electrode or between the organic compound layer and the second electrode. To do. In particular, from the viewpoint of improving conductivity, the layer containing the π-conjugated organic compound preferably further has an acceptor or a donor for the π-conjugated organic compound. Even in such a case, the conductivity of the layer containing the π-conjugated organic compound is preferably 10 ⁻¹⁰ S / cm or more.

By producing an electric appliance using the light emitting device as described above, it is possible to provide an electric appliance that is kept longer than before. Therefore, the present invention also includes electric appliances using the light-emitting device of the present invention.

The light emitting device in the present invention means an image display device or a light emitting device using a light emitting element. In addition, a connector such as a flexible printed circuit (FPC) or TAB (Tape Automated Bonding) tape or T is attached to the light emitting element.
A module with a CP (Tape Carrier Package) attached, a module with a printed wiring board in front of a TAB tape or TCP, or an IC (integrated circuit) directly mounted on a light emitting element by the COG (Chip On Glass) method All modules shall be included in the light emitting device.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In addition, in order to take out light emission, at least one of the first electrode and the second electrode may be transparent in the organic light emitting element, but a transparent first electrode (anode) is formed on the substrate,
A device structure in which light is extracted from the first electrode (anode) is general. In practice, a structure in which the first electrode is used as a cathode and light is extracted from the cathode and a structure in which light is extracted from the side opposite to the substrate are also applicable.

First, an outline of the driving method used in the present invention is shown in FIG. FIG. 1 (a) shows that when a forward bias for causing an organic light emitting element to emit light and a reverse bias having a polarity opposite to the forward bias are applied, the maximum voltage of the forward bias in the AC cycle composed of the forward bias and the reverse bias (that is,
Vf) is larger than the reverse bias maximum voltage (ie, Vr), which is the driving method of the present invention. The duty ratio is set to 50% here, but in practice, any value may be used as long as the image can be displayed.

When the organic light-emitting element emits light by the forward bias (voltage Vf), no dielectric breakdown occurs in the organic light-emitting element (if the dielectric breakdown occurs, light emission is not possible). That is, as long as the reverse bias voltage Vr is set to be lower than Vf, the possibility of dielectric breakdown during reverse bias is extremely small even in the long term. Specifically, it is preferable to set the maximum voltage Vr of the reverse bias to a quarter or more of the maximum voltage Vf of the forward bias.

The present inventor has found that even in the state of Vf> Vr, the life is sufficiently improved by the reverse bias. Especially, if Vf> Vr ≧ 1 / 4Vf, it has been confirmed that the life is sufficiently improved.

Further, since Vf> Vr, it is preferable that the time Tr for applying the reverse bias is equal to or longer than Tf in order to fully utilize the effect of improving the life by the reverse bias (ie, , Tf ≦ Tr). Figure 1
Shown in (b). In FIG. 1 (b), Tf = Tr.

When Tf becomes equal to or less than Tr in this way,
It is considered that the luminance usually decreases because the time period of light emission becomes short, but in reality, the luminance may not decrease so much.

FIG. 2 is used to explain the reason.
FIG. 2 is a diagram showing the energy levels, and 201 is the highest occupied molecular orbit (HOM) of the light emitter (here, it is assumed to be a fluorescent material).
O) and 202 represent the lowest unoccupied molecular orbit (LUMO) of the light emitter. In this case, if the luminescent material is extremely pure, the excited molecule releases energy in the form of emission 203 with the probability of fluorescence quantum yield Φ (the rest undergoes heat deactivation or intersystem crossing). .

However, when impurities or morphological defects are present, the impurity level 211
Carriers are trapped in the light emitting element 202 or energy transfer 212 occurs from the light emitting body 202. Then, the light emission 213 from the impurity level 211 does not occur, and the light is deactivated 214 without emitting light.

However, by carrying out the AC driving as in the present invention, it is possible to suppress the energy transition to the impurity level 211 due to impurities or morphological defects, and the emission 203 of the light emitting body can be suppressed as compared with the DC driving. There is a possibility that many can be taken out. Therefore, even if Tf ≦ Tr, no problem occurs as long as an image can be displayed.

Further, as a method of extracting a large amount of light emission even in the state of Tf ≦ Tr, a method of applying an organic light emitting element (hereinafter, referred to as “triplet light emitting element”) which emits light from a triplet excited state can be considered. .

The light emission from the triplet excited state (phosphorescence) has a decay lifetime of the light emission from the singlet excited state (fluorescence).
Longer (specifically, the half-life of decay is about several nanoseconds for fluorescence, whereas the phosphorescence of a phosphorescent material applied to an organic light emitting device is about several hundred nanoseconds to several microseconds). Therefore, afterglow can be utilized even if Tf is small. Further, since the triplet light emitting element has higher current efficiency than the singlet light emitting element, sufficient light emission can be extracted even when Tf is small.

When a complex having a rare earth metal ion is used as a light-emitting body, this also emits light from the triplet excited state, but the half-life of its decay is on the order of several milliseconds. Therefore, an organic light emitting device that emits light from such rare earth metal ions is also suitable.

By the way, when the organic light emitting element is driven by direct current, there are constant voltage driving for applying a constant voltage to the organic light emitting element and constant current driving for flowing a constant current. May be applied to. That is, since almost no current flows during reverse bias, a constant voltage may be applied for the reverse bias, and the forward bias may be either a constant voltage or a constant current. From the viewpoint of device life, it is considered that a constant current is more preferable. From the viewpoint of preventing defects such as a short circuit in the long term, a constant voltage is preferable.

Next, regarding the organic light-emitting element applicable to the present invention, an organic compound layer which emits light by applying a voltage between the first electrode and the second electrode, as is conventionally used, is used. Any organic light emitting element may be used as long as it is provided. Any color of emission may be used,
When manufacturing a full-color display device, the method of combining the three primary colors of light (blue, red, and green), the method of combining a white organic light emitting element with a color filter, and the method of combining a blue organic light emitting element with a color conversion layer The method etc. are known.

Particularly in the present invention, it is preferable that the organic compound layer is composed of a polymer compound. When the driving of the present invention is carried out, it is considered that Vf higher than that of direct current driving may be required in some cases, but since an organic light emitting element using a polymer compound has a low driving voltage, light emission is performed at a lower voltage. It can be taken out and is useful. Further, since the driving voltage is low, the stress applied to the element can be reduced, so that the effect of further improving the life can be expected by the combination with the AC drive of the present invention.

In order to reduce the driving voltage in this sense, it is preferable to provide a layer having a certain degree of conductivity between the organic compound layer and the electrode. in this case,
Providing a layer having conductivity is also expected to have the effect of more efficiently eliminating the accumulation of space charges. An inorganic compound or an organic compound may be used as such a layer, but an organic compound is preferable from the viewpoint of adhesion.

When an inorganic compound is used for such a conductive layer, titanium nitride, calcium nitride, etc. may be mentioned. Titanium nitride has a large work function and is preferably applied to the anode side. Conversely, calcium nitride is preferably applied on the cathode side.

When an organic compound is used for such a conductive layer, a method of applying a conductive polymer compound can be considered. In particular, from the viewpoint of improving conductivity, a material to which an acceptor or a donor is added is preferable. Examples thereof include polyaniline, which is a water-soluble conductive polymer material, and PEDOT / PSS in which polystyrenesulfonic acid is added to polyethylenedioxythiophene. Since these are p-type semiconductors, they are mainly applied to the anode side.

Further, a monomolecular π-conjugated organic compound may be applied, and in this case also, from the viewpoint of improving the conductivity,
Those to which an acceptor or a donor is added are preferable. As an example, various carrier transport materials used in organic light emitting devices may be used as a monomolecular π-conjugated organic compound, and an acceptor or a donor may be added by co-evaporation or the like.

It has the conductivity as described above.
The conductivity of the layer is in terms of eliminating space charge accumulation.
The conductivity above the boundary between the edge body and the semiconductor is preferable.
Is 10 ^-TenIt is preferably S / cm or more.

A light-emitting device may be manufactured by combining these organic light-emitting elements with an AC driving means. The light emitting device has various applications such as illumination using simple planar light emission and a display device in which pixels are arranged in a matrix.

In the case of a display device in which pixels are arranged in a matrix, a passive matrix type and an active matrix type can be considered. The conceptual diagram is shown in FIG. 3 and FIG.

FIG. 3 is a conceptual diagram of the passive matrix type. FIG. 3 is a top view. That is, a stripe-shaped first electrode 302 is formed on a substrate 301, an organic compound layer is formed thereon, and a second electrode 303 is formed thereon in a form orthogonal to the first electrode. ing. The intersection is the pixel P. During driving, the first electrode 302 and the second electrode 303
AC drive can be performed by applying a forward bias and a reverse bias between the two.

FIG. 4 is a conceptual diagram of the active matrix type. FIG. 4 is a top view. That is, the island-shaped first electrode 402 is formed on the substrate 401, and the insulator partition wall 403 is formed so as to project above the first electrode 402 and surround the pixel portion. Then, the organic compound layer is formed thereon, and the second electrode is further formed thereon in a solid form.

Further, a data signal line 407, a scanning signal line 408, and a non-linear element 409 connected to the data signal line 407 and the scanning signal line 408 are provided,
The nonlinear element is connected to the first electrode 402 by the contact 410. This allows each pixel to be independently switched. The non-linear element 409 is typically
A combination of a thin film transistor and a capacitor connected to each other, or a combination of a thin film transistor and a parasitic capacitor of the thin film transistor.
During driving, AC driving can be performed by applying a forward bias and a reverse bias between the first electrode 402 and the second electrode.

[0061]

EXAMPLES Example 1 In this example, a polymer compound that emits light is applied as an organic compound layer, and a layer made of a conductive polymer compound is further provided between an anode and an organic compound layer. The light emitting element was measured for luminance deterioration when constant voltage AC driving (both forward bias and reverse bias were driving at constant voltage).

The device structure is shown in FIG. First, a glass substrate 501 on which ITO having a film thickness of 110 nm was formed as an anode 502, a 1.3 wt% aqueous solution of PEDOT / PSS was applied, and baked at 100 ° C. for 1 hour to obtain a conductive polymer compound. Including layer 50
Formed 3. The film thickness was about 30 nm.

Then, after vacuum baking at 80 ° C. for 3 minutes, 0.16 g of the poly (para-phenylene vinylene) derivative exhibiting yellow luminescence is applied to a toluene solution prepared by dissolving 40 ml of toluene, and dried by heating. To form an organic compound layer (in this case, only the light emitting layer) 504. The film thickness is 80n
It was about m.

Further, under a vacuum of 10 ^-4 Pa, Ca
m, and then Al was vapor-deposited at 200 nm to form a cathode 505. And
It was laminated with a counter glass coated with an ultraviolet curable resin and irradiated with ultraviolet rays for sealing.

Using this element, a forward bias of 3.7 [V], a reverse bias of 1.7 [V], a duty ratio of 50% by an AC power supply 506,
A reliability test was performed when a constant voltage AC drive with a frequency of 60 Hz was performed (initial brightness was about 400 cd / cm ² ). The result is shown in Fig. 6.
It is shown in the plot "AC". Even after about 700 hours, the half-life of brightness was not reached yet.

[Comparative Example 1]

For comparison, in the same device as in Example 1, the initial brightness was set to about 400 cd / cm ^2, which is the same as in Example 1,
A reliability test was performed when constant voltage DC drive was performed (drive voltage; 3.65 [V]). The results are shown in the plot "DC" in FIG. The brightness reached its half-life in just over 400 hours.

Compared with AC, it can be seen that the initial deterioration is particularly remarkable in the constant voltage DC drive. The element driving conditions of Example 1 and Comparative Example 1 are summarized in Table 1 below.

[0069]

[Table 1]

Example 2 In this example, an element similar to that of Example 1 was manufactured, and the reliability of the element was measured by slightly changing the driving conditions. The drive was a forward bias: 3.8 [V], a reverse bias: 1.4 [V], a duty ratio: 50%, a frequency: 600 Hz constant voltage AC drive (this initial brightness was about 300 cd / cm ² ). ). The results are shown in the plot "AC" in FIG. About 700
Even after a lapse of time, it still maintained about 60% of the initial brightness.

[Comparative Example 2]

For comparison, in the same device as in Example 2, the initial luminance was set to about 300 cd / cm ^2, which is the same as in Example 2,
A reliability test was performed when constant voltage DC drive was performed (current drive voltage: 3.65 [V]). The results are shown in the plot "D
"C". The brightness reached its half-life in about 500 hours.

Compared with AC, it can be seen that the initial deterioration is particularly remarkable in the constant voltage DC drive. The device driving conditions of Example 2 and Comparative Example 2 are summarized in Table 2 below.

[0074]

[Table 2]

[Embodiment 3] In this embodiment, a passive matrix light emitting device will be illustrated as an example of the light emitting device disclosed in the present invention. The top view is shown in FIG. 8 (a), and FIG.
FIG. 8 shows a sectional view taken along the line P-P 'in FIG. Although various configurations are possible as the element configuration of the organic light emitting element, for example, the structure of Example 1 or Example 2 may be applied.

In FIG. 8A, reference numeral 801 is a substrate, and a glass material is used here. It is also possible to use a plastic material, and as the plastic material, polyimide, polyamide, acrylic resin, epoxy resin, PES (polyether sulfone), PC (polycarbonate), PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) can be used. A plate-shaped or film-shaped one can be used.

Reference numeral 802 denotes a scanning line (anode) made of an oxide conductive film.
In this embodiment, indium tin oxide (ITO) is used. Reference numeral 803 is a data line (cathode) made of a metal film, and in this embodiment, a barium fluoride and aluminum laminate is used. Further, 804 is a bank made of acrylic resin and functions as a partition wall for dividing the data line 803. Both the scanning lines 802 and the data lines 803 are formed in a plurality of stripes and are provided so as to be orthogonal to each other. Although not shown in FIG. 8A, an organic compound layer is sandwiched between the scanning line 802 and the data line 803, and the intersection portion 805 becomes a pixel.

The scanning line 802 and the data line 803 are TA
It is connected to an external drive circuit via the B tape 807. Reference numeral 808 represents a wiring group formed by the scanning lines 802, and 809 represents a wiring group formed by a set of connection wirings 806 connected to the data lines 803. Also, although not shown, TAB
Instead of the tape 807, a TCP provided with an IC on a TAB tape may be connected.

Further, in FIG. 8B, 810 is a sealing material,
Reference numeral 811 is a cover material that is attached to the substrate 801 by a seal material 810. As the sealant 810, a photocurable resin may be used, and a material that is less outgassed and has low hygroscopicity is desirable. The cover material is preferably the same material as the substrate 801, and glass (including quartz glass) or plastic can be used. Here, a glass material is used.

Next, an enlarged view of the structure of the pixel region 812 is shown in FIG.
Shown in (c). 813 is an organic compound layer. Note that FIG. 8 (c)
As shown in, the bank 804 has a shape in which the width of the lower layer is narrower than the width of the upper layer, and the data line 803 can be physically divided. Further, the pixel portion 814 surrounded by the sealant 810 is shielded from the outside air by the sealant 815 made of resin, and has a structure for preventing deterioration of the organic compound layer.

In the light emitting device of the present invention having the above structure, the pixel portion 814 has the scanning line 802, the data line 803, and the bank 804.
Since it is formed of the organic compound layer 813, it can be manufactured by a very simple process.

A polarizing plate may be provided on the display surface (image observing surface) of the light emitting device shown in this embodiment. This polarizing plate has an effect of suppressing reflection of light incident from the outside and preventing an observer from being reflected on the display surface. Generally, a circularly polarizing plate is used. However, in order to prevent the light emitted from the organic compound layer from being reflected by the polarizing plate and returning to the inside, it is preferable to adjust the refractive index so that the structure has less internal reflection.

[Embodiment 4] In this embodiment, a passive matrix type full-color light emitting device is illustrated as an example of the light emitting device disclosed in the present invention. Here, a configuration is shown in which light is extracted from the side opposite to the substrate. . 9 (a) shows a top view thereof, and FIG. 9 (b) shows a sectional view of FIG. 9 (a) taken along the line P-P '. The element structure of the organic light emitting element is as follows.
Here, a white light emitting element is used.

In FIG. 9A, reference numeral 901 is a substrate, and a glass material is used here. It is also possible to use plastic materials, such as polyimide, polyamide, acrylic resin,
Epoxy resin, PES (polyether sulfone), PC (polycarbonate), PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) in plate or film form can be used.

Reference numeral 902 denotes a scanning line (anode) made of an oxide conductive film.
Therefore, TiN is used in this embodiment. Reference numeral 903 denotes a data line (cathode) formed of a metal film. In this embodiment, barium fluoride is laminated with a semi-transmissive film of aluminum, and the IT
A stack of O layers is used. Light emission is taken out from the cathode side. A bank 904 made of acrylic resin functions as a partition for dividing the data line 903. Both the scanning lines 902 and the data lines 903 are formed in a plurality of stripes and are provided so as to be orthogonal to each other. Although not shown in FIG. 9 (a),
An organic compound layer is sandwiched between the scan line 902 and the data line 903, and the intersection portion 905 becomes a pixel.

The scanning line 902 and the data line 903 are TA
It is connected to an external drive circuit via the B tape 907. Reference numeral 908 represents a wiring group formed by the scanning lines 902, and 909 represents a wiring group formed by a set of connection wirings 906 connected to the data lines 903. Also, although not shown, TAB
Instead of the tape 907, a TCP provided with an IC on a TAB tape may be connected.

Further, in FIG. 9B, 910 is a sealing material,
Reference numeral 911 is a cover material that is attached to the substrate 901 by the seal material 910. As the sealing material 910, a photocurable resin may be used, and a material that is less outgassed and has low hygroscopicity is desirable. The cover material is preferably the same material as the substrate 901, and glass (including quartz glass) or plastic can be used. Here, a glass material is used. 92
0 is a color filter. Here, the cover material 911
The example formed in FIG.

Next, an enlarged view of the structure of the pixel region 912 is shown in FIG.
Shown in (c). Reference numeral 913 is an organic compound layer. Note that FIG. 9 (c)
As shown in, the bank 904 has a shape in which the width of the lower layer is narrower than the width of the upper layer, and the data line 903 can be physically divided. The pixel portion 914 surrounded by the sealing material 910 is shielded from the outside air by the sealing material 915 made of resin, and has a structure that prevents deterioration of the organic compound layer.

In the display device of the present invention having the above structure, the pixel portion 914 has the scanning lines 902, the data lines 903, and the banks 904.
Further, since the organic compound layer 913 is formed of the organic compound layer 913 and the organic compound layer only needs to emit white light, a full-color light emitting device can be manufactured by a very simple process.

[Embodiment 5] The light emitting device of the present invention described in the above embodiment has the advantages of good yield and long life. Therefore, an electric appliance including the light emitting device as a display unit or the like is an electric appliance that keeps longer than before.

Further, since the light emitting device is of a self-luminous type, it does not require a backlight like a liquid crystal display device,
Since the thickness of the organic compound layer is less than 1 μm, it can be made thin and lightweight. Therefore, an electric appliance including the light emitting device as a display unit or the like is thinner and lighter than the conventional electric appliance. This is also extremely useful, especially for electric appliances such as portable devices, because it is directly connected to convenience (lightness and compactness when carrying). Furthermore, in general electric appliances as well, thinness (not bulky) is undoubtedly useful in terms of transportation (capable of mass transportation) and installation (securing a space such as a room).

Since the light emitting device is of a self-luminous type, it has characteristics that it is superior in visibility in a bright place and has a wide viewing angle as compared with a liquid crystal display device. Therefore, an electric appliance having the light emitting device as a display unit has a great merit in viewability of display.

That is, an electric appliance using the light emitting device of the present invention has advantages of a conventional organic light emitting element such as thinness, light weight, and high visibility, and also has a feature of long life and high yield, which is extremely useful. Is.

In this example, an electric appliance including the light emitting device of the present invention as a display portion is illustrated. Specific examples thereof are shown in FIGS. Note that any of the light emitting devices disclosed in the present invention may be used as the light emitting device included in the electric appliance of this embodiment. For example, the matrix display device shown in Embodiments 3 and 4 may be used.

FIG. 10A shows a display device using an organic light emitting element, which includes a housing 1001a, a support 1002a, and a display unit 10.
Including 03a. By manufacturing a display using the light-emitting device of the present invention as the display portion 1003a, a thin, lightweight, and long-lasting display can be realized. Therefore, transportation is simplified, space can be saved during installation, and the life is long.

FIG. 10B shows a video camera, which is a main body 100.
1b, display unit 1002b, voice input unit 1003b, operation switch 1004
b, a battery 1005b, and an image receiving unit 1006b are included. By manufacturing a video camera using the light-emitting device of the present invention as the display portion 1002b, a lightweight and long-life video camera can be realized.

FIG. 10 (c) shows a digital camera including a main body 1
001c, display 1002c, eyepiece 1003c, operation switch 1004c
including. By manufacturing a digital camera using the light-emitting device of the present invention as the display portion 1002c, a long-life and lightweight digital camera can be realized.

FIG. 10 (d) shows an image reproducing apparatus equipped with a recording medium, which includes a main body 1001d, a recording medium (CD, LD, DVD or the like) 1002d, operation switches 1003d, a display section (A) 1004d and a display section ( B) Including 1005d. The display unit (A) 1004d mainly displays image information, and the display unit (B) 1005d mainly displays character information. The light-emitting device of the present invention is provided with these display unit (A) 1004d and display unit
(B) By manufacturing the image reproducing device used as 1005d, it is possible to realize the image reproducing device that is lightweight and long-lasting. The image reproducing device provided with this recording medium includes a CD reproducing device, a game machine and the like.

FIG. 10 (e) shows a portable computer, which includes a main body 1001e, a display section 1002e, an image receiving section 1003e,
An operation switch 1004e and a memory slot 1005e are included. By manufacturing a portable computer using the light-emitting device of the present invention as the display portion 1002e, a thin, lightweight portable computer with a long life can be realized. It should be noted that this portable computer can record information on a recording medium in which a flash memory or a non-volatile memory is integrated and can reproduce the information.

FIG. 10 (f) shows a personal computer, which has a main body 1001f, a casing 1002f, a display unit 1003f, and a keyboard 1.
Includes 004f. By manufacturing a personal computer using the light-emitting device of the present invention as the display portion 1003f, a thin, lightweight personal computer with a long life can be realized. Especially when it is necessary to carry around like a laptop computer, it is a great advantage in terms of lightness.

Note that the above electric appliances often display information distributed through electronic communication lines such as the Internet and wireless communication such as radio waves, and in particular, opportunities to display moving image information are increasing. The response speed of the organic light emitting device is very fast, and it is suitable for such moving image display.

Next, FIG. 11 (a) shows a mobile phone, which has a main body 1
101a, voice output unit 1102a, voice input unit 1103a, display unit 1104
a, operation switch 1105a, and antenna 1106a are included. By manufacturing a mobile phone using the light-emitting device of the present invention as the display portion 1104a, a thin and lightweight mobile phone with a long life can be realized.

FIG. 11B shows a portable game machine, which is a main body 1
101b, display 1102b, main power supply 1103b, operation switch 1104b
And 1105b are included. By manufacturing a portable game device using the light-emitting device of the present invention as the display portion 1102b, a thin and lightweight portable game device with a long life can be realized. In addition, game machines often require moving images that move rapidly, but organic light-emitting devices have a fast response to input,
It is most suitable for such applications.

FIG. 11C shows an audio device (specifically, a car audio system), which includes a main body 1101c, a display section 1102c, and operation switches 1103c and 1104c. Display unit of light emitting device of the present invention
By manufacturing the audio device used as the 1102c, a lightweight audio device with a long life can be realized. Further, in the present embodiment, an on-vehicle audio is shown as an example, but it may be used for home audio.

In the electric appliance as shown in FIGS. 10 to 11, an optical sensor is further incorporated and a means for detecting the brightness of the usage environment is provided, so that the light emission brightness can be adjusted according to the brightness of the usage environment. It is effective to have a function to modulate the. If the user can secure a brightness of 100 to 150 in terms of contrast ratio compared to the brightness of the usage environment,
Can recognize images or text information without problems. That is, when the usage environment is bright, it is possible to increase the brightness of the image to make it easier to see, and when the usage environment is dark, it is possible to suppress the brightness of the image and suppress power consumption.

Also, various electric appliances using the light emitting device of the present invention as a light source are very useful because they have a long life and can be made thin and lightweight. Typically, it is an electric appliance including the light emitting device of the present invention as a light source such as a backlight or a front light of a liquid crystal display device or a light source of a lighting device.

Therefore, even when all the display parts of the electric appliances of FIGS. 10 to 11 shown in this embodiment are liquid crystal displays, the light emitting device of the present invention is used as the backlight or front light of the liquid crystal displays. By keeping the electric appliances that
A thin and lightweight appliance can be achieved.

[0108]

By implementing the present invention, the AC driving method of the organic light emitting device which can alleviate the deterioration of the brightness and prevent the short circuit in the initial stage of driving is further improved as compared with the conventional one, and can be seen in the long term. However, it is possible to prevent the breakdown of the element due to dielectric breakdown and the like, and by combining the improved AC driving means with the organic light emitting element, it is possible to provide a light emitting device with a small deterioration in luminance and a high yield. Furthermore, by manufacturing an electric appliance using the light emitting device, it is possible to provide an electric appliance that lasts longer than before.

[Brief description of drawings]

FIG. 1 is a diagram showing a concept of a driving method of the present invention.

FIG. 2 is a diagram showing a process of light emission.

FIG. 3 is a diagram showing a concept of a passive matrix display device.

FIG. 4 is a diagram showing a concept of an active matrix display device.

FIG. 5 is a diagram showing a structure of an organic light emitting device.

FIG. 6 is a diagram showing the results of Example 1 and Comparative Example 1.

FIG. 7 is a diagram showing the results of Example 2 and Comparative Example 2.

FIG. 8 illustrates a structure of a light emitting device.

FIG. 9 illustrates a structure of a light emitting device.

FIG. 10 is a diagram showing a specific example of an electric appliance.

FIG. 11 is a diagram showing a specific example of an electric appliance.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/22 H05B 33/22 BCD F term (reference) 3K007 AB11 BA06 DB03 GA02 5C080 AA06 BB05 DD18 DD29 FF09 JJ04 JJ05 JJ06 KK07 KK43 KK47

Claims (17)

[Claims] 1. A light emitting element provided with an organic compound layer capable of emitting light by applying a voltage between a first electrode and a second electrode, and a forward bias and a reverse bias for causing the light emitting element to emit light. And a bias applying unit that applies a bias, wherein the bias applying unit is configured such that an absolute value of a maximum voltage of the forward bias is within a cycle of alternately applying the forward bias and the reverse bias. A light emitting device which operates so as to be larger than an absolute value of the maximum voltage of the reverse bias. 2. The light emitting device according to claim 1, wherein the bias applying means sets the absolute value of the maximum voltage of the reverse bias to 4 of the absolute value of the maximum voltage of the forward bias.
A light-emitting device which operates so as to be one-third or more. 3. The light emitting device according to claim 1, wherein the bias applying unit applies the reverse bias within the cycle in the same time as the forward bias. A light-emitting device which operates so as to be long or long. 4. The light emitting device according to claim 3, wherein the light emitting element exhibits light emission from a triplet excited state. 5. The light emitting device according to claim 3, wherein the light emitting element emits light from rare earth metal ions. 6. The light emitting device according to claim 1, wherein the bias applying means applies a constant voltage to both the forward bias and the reverse bias to the light emitting element. A light-emitting device which operates in the following manner. 7. The light emitting device according to claim 1, wherein the bias applying means applies the forward bias to the light emitting element so as to flow a constant current.
A light emitting device, wherein the reverse bias is operated so that a constant voltage is applied to the light emitting element. 8. The light emitting device according to claim 1, wherein the organic compound layer contains a polymer compound that emits light. 9. The light emitting device according to claim 1, wherein between the organic compound layer and the first electrode, or between the organic compound layer and the second electrode, A light-emitting device comprising a conductive layer containing an inorganic compound. 10. The light emitting device according to claim 9, wherein the conductive layer containing the inorganic compound has a conductivity of 10 ⁻¹⁰ S / c.
A light emitting device having a length of m or more. 11. The light emitting device according to claim 1, wherein between the organic compound layer and the first electrode, or between the organic compound layer and the second electrode, A light-emitting device comprising a layer containing a conductive polymer compound. 12. The light emitting device according to claim 11,
The layer including the conductive polymer compound further has an acceptor or a donor for the conductive polymer compound. 13. The light emitting device according to claim 11, wherein the layer containing the conductive polymer compound has a conductivity of 10 ⁻¹⁰ S / cm or more. 14. The light emitting device according to claim 1, wherein between the organic compound layer and the first electrode, or between the organic compound layer and the second electrode, A light-emitting device having a layer containing a π-conjugated organic compound. 15. The light emitting device according to claim 14,
The layer containing the π-conjugated organic compound further has an acceptor or a donor for the π-conjugated organic compound. 16. The light emitting device according to claim 14 or 15, wherein the layer containing the π-conjugated organic compound has a conductivity of 10 ⁻¹⁰ S / cm or more. 17. An electric appliance using the light emitting device according to claim 1. Description: