JP4069745B2 - Organic EL panel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electroluminescence (EL) panel, and in particular, an organic EL panel that performs multi-color display, and has excellent emission stability that suppresses display defects such as pixel defects and lines due to a short circuit between upper and lower electrodes during use. The present invention relates to an organic EL panel.
[0002]
[Prior art]
The organic EL panel has a plurality of pixels provided with an organic layer including a light emitting layer made of an organic EL material between a pair of electrodes, that is, a lower electrode and an upper electrode.
[0003]
Since such an organic EL panel is self-luminous, it has excellent visibility, and can be driven at a low voltage of several V to several tens V. Therefore, the organic EL panel can be reduced in weight including a driving circuit. Therefore, it can be expected to be used as a thin film display, lighting, and backlight.
[0004]
A multi-color organic EL panel that emits multi-color light is configured to have pixels having two or more different emission colors by disposing light-emitting layers having different emission colors in the same plane.
[0005]
As a conventional general multi-color type organic EL panel, FIG. 14 shows a schematic plan configuration of a two-color type organic EL panel of yellow (Y) and blue (B), and FIG. 15 shows a schematic cross-sectional configuration. Here, in FIG. 14, for identification, the boundaries of the pixels Y and B having different emission colors are indicated by solid lines, the lower electrode 10 is indicated by a one-dot chain line, and the upper electrode 60 is indicated by a broken line.
[0006]
As shown in FIG. 14, a yellow pixel Y having a yellow emission color and a blue pixel B having a blue emission color are arranged such that pixels Y and B having different emission colors are adjacent to each other such as YBYBYB. Are repeatedly arranged in the same plane. A portion U surrounded by a thick line in FIG. 14 is one unit of repetition.
[0007]
As shown in FIG. 14, each pixel Y and B has a vertical pitch of P1 and a horizontal pitch of (L1 + S1), and the light emitting area H in the pixels Y and B has a vertical size of L3 and a horizontal size. Is L1. The interval between the lower electrodes 10 is S1, and the interval between the upper electrodes 60 is (P1-L3).
[0008]
As shown in FIG. 15, the cross-sectional structure is such that a lower electrode 10 such as ITO is formed on a substrate 1 by a photolithographic method, and a hole transport layer 30, light emitting layers Y 40, B 40 are formed on the lower electrode 10. The organic layer 55 such as the electron transport layer 50 is sequentially stacked, and the upper electrode 60 is stacked thereon by a vapor deposition method. Here, the lower electrode 10 and the upper electrode 60 are striped and orthogonal to each other.
[0009]
Here, the hole transport layer 30 and the electron transport layer 50 in the plurality of pixels Y and B, that is, the organic layer 55 excluding the light-emitting layers Y40 and B40, are formed in a lump by vacuum deposition. It is comprised as a film | membrane integrated continuously between these pixels Y and B.
[0010]
On the other hand, the light emitting layers Y40 and B40 having different light emission colors are formed by vacuum deposition using a mask having an opening corresponding to the light emitting layer. For example, after forming one light emitting layer Y40 by vacuum deposition using a mask, the position of the mask is shifted and the other light emitting layer B40 is formed by vacuum deposition.
[0011]
In this way, the pixels Y and B are formed, and the region where the upper and lower electrodes 10 and 60 are opposed to each other is formed as the light emitting region H, as shown by the hatched area in FIG. That is, in the light emitting region H of each pixel Y and B, display is performed by applying a pulse voltage between the upper and lower electrodes 10 and 60 so that a forward bias voltage is applied during light emission and a reverse bias voltage is applied during non-light emission. Like to do.
[0012]
However, as shown in FIG. 15, between the adjacent pixels Y and B, the light emitting layers Y40 and B40 in the organic layer 55 become thinner and sometimes disappear in the periphery of the light emitting region H of each pixel. A thin film portion 55a that is thinner than the organic layer 55 in the light emitting region H may be formed.
[0013]
This is because, as described above, when a film is formed by vapor deposition using a mask for each of the light emitting layers Y40 and B40 having different emission colors, the vapor deposition depends on the alignment accuracy of the mask and the distance between the mask and the substrate. This is because a portion where the end portions of the light emitting layers Y40 and B40 become thin (including the case where they disappear) is generated due to the influence of the wraparound of the material.
[0014]
Then, in the thin film portion 55a formed between the adjacent pixels Y and B, a portion where the distance between the upper and lower electrodes 10 and 60 becomes narrower than necessary occurs, and a short circuit between the upper and lower electrodes 10 and 60 is likely to occur. For example, a short circuit occurs as shown by the zigzag line Zg in FIG.
[0015]
In order to deal with such a problem of short circuit between upper and lower electrodes caused by the thin film portion between pixels, conventionally, it has been mainly applied to an inorganic EL element, but a portion where a light emitting layer between adjacent pixels always overlaps is provided. Thus, a technique for increasing the film thickness of the layer in the overlapping portion and preventing the upper and lower electrodes from being short-circuited has been proposed (see, for example, Patent Document 1).
[0016]
Incidentally, in the past, although it was not a thin film part, as a countermeasure in the light emitting area of the pixel, a technique was proposed that self-repairs by open-breaking a defective part that is likely to be short-circuited due to the presence of conductive foreign substances in the light emitting area. (For example, refer to Patent Document 2).
[0017]
[Patent Document 1]
Japanese Patent Publication No. 7-118387 (2nd page, Fig. 1)
[0018]
[Patent Document 2]
Japanese Patent Laid-Open No. 11-162637 (page 3-6, FIG. 2-3)
[0019]
[Problems to be solved by the invention]
However, according to the study by the present inventors, it has been found that the following problem occurs in the above-described method in which the portion where the light emitting layers between adjacent pixels always overlap each other.
[0020]
That is, the overlapping portion becomes a non-light emitting portion because the film thickness is increased and electric field strength is not ensured. For this reason, the area of the light emitting region in the pixel is reduced as compared with the conventional general configuration in which the light emitting layer between adjacent pixels is not overlapped.
[0021]
In that case, it is necessary to increase the luminance of the light emitting region of the pixel in order to realize the light emission luminance necessary for the organic EL panel. Then, it is necessary to increase the driving voltage, and a decrease in luminance with the use time is promoted due to deterioration of the pixel or the like. This is not preferred.
[0022]
The present invention has been made on the basis of the novel problem found by the present inventors as described above, and in an organic EL panel in which pixels of different emission colors are arranged in the same plane, between adjacent pixels. The aim is to appropriately reduce the short circuit between the upper and lower electrodes caused by the thin film part of the organic layer existing between adjacent pixels, without necessarily reducing the area of the light emitting area of the pixel, without necessarily superposing the light emitting layer. And
[0042]
[Means for Solving the Problems]
  An organic EL panel has a pixel having an organic layer including a light emitting layer between a pair of electrodes, that is, a lower electrode and an upper electrode, and a forward bias voltage is applied to the pixel during light emission. In addition, the pulse voltage is applied so that a reverse bias voltage is applied when no light is emitted.
[0043]
As described above, in the light emitting region of the pixel, there is a conventional method for preventing the short circuit between the upper and lower electrodes by causing self-healing as in Patent Document 2 to open-break the defective portion of the light emitting region. The basic concept of this technique is that the upper electrode is scattered by the voltage energy of the reverse bias pulse.
[0044]
However, an example in which such a self-repair technique is applied to a thin film portion between pixels is not conventional.
[0045]
The inventors of the present invention focused on open breakdown of a defective portion of the thin film portion of the organic layer, that is, a portion that is easily short-circuited in the thin film portion, by applying the reverse bias voltage. As a result of intensive studies, it was found that the short circuit of the upper and lower electrodes caused by the thin film portion can be prevented by paying attention to the breakdown voltage of the thin film portion and adopting an element structure corresponding to the breakdown voltage.
[0046]
The breakdown voltage of the thin film portion was defined as follows. Basically, the withstand voltage of the thin film portion under the voltage application conditions during use was used. The breakdown voltage of the thin film portion is a breakdown voltage when a reverse bias voltage is applied, based on the principle of the organic EL panel. The breakdown voltage of the thin film portion depends on the reverse bias voltage application method.
[0047]
Therefore, in the evaluation of the withstand voltage, the reverse bias voltage should be set based on the voltage measured in the same state as the pulse width defined by the duty ratio, frequency, etc. when actually driving.
[0048]
For this reason, the evaluation of the breakdown voltage of the thin film portion is performed by applying a pulse voltage having a predetermined duty ratio and pulse width to the pixel, causing the current to flow in the forward direction, and emitting a reverse bias voltage when no light is emitted. It was performed under the voltage application condition at the time of use of applying (see FIG. 7).
[0049]
In this operation, while the forward current remains constant (that is, the light emission luminance is substantially constant), the reverse bias voltage at which light emission does not occur is increased while the reverse bias voltage is increased. The reverse bias voltage was changed by increasing the voltage by several volts while holding each voltage for 5 seconds or more and 1 minute or less (see FIG. 8).
[0050]
In this way, when the reverse bias voltage is increased, a part or all of the thin film portion is scattered. The value of the reverse bias voltage at this time is defined as the breakdown voltage of the thin film portion. According to this method, a substantially constant value can be obtained as the breakdown voltage of the thin film portion under the voltage application condition during use.
[0051]
  Claim1The invention described in 1 is created by obtaining the breakdown voltage of the thin film portion as described above in an organic EL panel and utilizing it.
[0052]
  That is, in the first aspect of the invention, a plurality of pixels (a plurality of pixels (55) sandwiching an organic layer (55) including at least a light emitting layer (Y40, B40) between the lower electrode (10) and the upper electrode (60). In the organic EL panel in which Y and B) are arranged in the same plane, the organic layer is a thin film portion in which the light emitting layer is thinner than the light emitting region in the periphery of the light emitting region (H) in the pixel ( 55a), and when a reverse bias voltage equal to or lower than the withstand voltage of the thin film part is applied under the voltage application conditions during use, the thin film part can be open broken.When the breakdown voltage of the thin film portion (55a) is expressed by the electric field strength per unit thickness of the thin film portion, the conductive organic film (20) is excluded from the thin film portion when calculating the electric field strength. Strength is 3.4 × 10 ⁶ V / cm or more, the reverse bias voltage is Vr, and the thickness of the thin film portion (55a) excluding the light emitting layer (Y40, B40) is Dy, and the ratio Vr of Vr and Dy is Vr. / Dy is Ya, the Ya is 1.4 × 10 ⁶ V / cm or more, and using the thickness Ty obtained by adding the thickness of the light emitting layer to the thickness Dy as the thickness of the organic layer (55) in the light emitting region (H), the ratio Vr / Ty of Vr and Ty is When Za is set, the Za is 1.4 × 10 ⁶ V / cm or more 2.4 × 10 ⁶ V / cm or lessIt is characterized by that.
[0053]
According to this, the value of the reverse bias voltage for causing the defective portion of the thin film portion to be open-destructed can be determined to an appropriate magnitude using the withstand voltage of the thin film portion under the voltage application condition during use as an index.
[0054]
In other words, when the voltage applied during use is set so that the reverse bias voltage applied during non-emission is less than the breakdown voltage of the thin film portion, the entire thin film portion, including the normal portion of the thin film portion, is scattered. Such an excessive reverse bias voltage setting can be prevented.
[0055]
Further, since the breakdown voltage of the thin film portion is used as an index, the reverse bias voltage is allowed to be smaller than the breakdown voltage. Therefore, it can be prevented that the reverse bias voltage is too small and the open breakdown becomes insufficient.
[0056]
As described above, according to the present invention, even when the thin film portion of the organic layer exists between adjacent pixels, the thin film portion is scattered by open-breaking and scattering the defective portion of the thin film portion at the time of use. In the portion, the upper and lower electrodes can be opened, and a short circuit can be prevented.
[0057]
Therefore, according to the present invention, it is not always necessary to adopt a configuration in which the light emitting layers are overlapped between adjacent pixels, and as a result, the area of the light emitting region of the pixel is not reduced. And the short circuit of the upper-lower electrode resulting from the thin film part of the organic layer which exists between adjacent pixels can be reduced appropriately.
[0058]
Here, the open breakdown referred to in the present invention means that a part of the thin film part, specifically, a part of the thin film part as a defective part that is easily short-circuited scatters, and the upper and lower electrodes are electrically connected in the scattered part. To be open.
[0060]
  In the organic EL panel, it was found that the breakdown voltage of the thin film portion in the organic layer can be defined by the total thickness regardless of the type of the organic material. And as an organic electroluminescent panel of this invention, the said electric field strength is 3.4x10.⁶V / cm or moreAndAccording to it,Of the present inventionThe effect can be exhibited effectively.
[0061]
Here, the film thickness of the thin film portion is the film thickness of the thin film portion (30, Y40, B40, 50) excluding the conductive film when the conductive organic film (30) such as copper phthalocyanine is included. . The reason why the conductive film is excluded is that the conductive film has a sufficiently small resistance value compared to other organic films, and an electric field is not applied so much.
[0062]
  Also bookIn the present invention, the reverse bias voltage is set to Vr, the thickness of the thin film portion (55a) excluding the light emitting layer (Y40, B40) is set to Dy, and the ratio Vr / Dy between these Vr and Dy is Ya. When Ya is 1.4 × 10⁶V / cm or more, and using the thickness Ty obtained by adding the thickness of the light emitting layer to the thickness Dy as the thickness of the organic layer (55) in the light emitting region (H), the ratio Vr / Ty of Vr and Ty is When Za is set, the Za is 1.4 × 10⁶V / cm or more 2.4 × 10⁶V / cm or lessIt is said.
[0063]
According to this, not only the defective portion of the thin film portion but also the defective portion of the light emitting region can be reliably open broken at the time of use, and by setting an upper limit to Za, all of the upper electrode including the normal portion in the light emitting region is scattered. Can be prevented.
[0064]
  Claim2In the invention described in the above, when the reverse bias voltage is Vr, the thickness of the upper electrode (60) is Da, and the ratio Vr / Da of these Vr and Da is Xa, the Xa is 2.2 × 10.⁶It is V / cm or more.
[0065]
If the reverse bias voltage is too small or the upper electrode is too thick, the upper electrode is difficult to scatter and difficult to self-repair. In that respect, the ratio Vr / Da = Xa between the reverse bias voltage Vr and the thickness Da of the upper electrode is 2.2 × 10.⁶V / cm or more is preferable because self-repair can be performed more appropriately (see FIG. 12).
[0066]
In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.
[0067]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below.
[0068]
(First embodiment)
1A and 1B are diagrams showing a schematic configuration of an organic EL panel according to a first embodiment of the present invention. FIG. 1A is a schematic plan view, and FIG. 1B is a schematic cross-sectional view. Here, in FIG. 1A, for identification, the boundaries of the pixels Y and B having different emission colors are solid lines, the lower electrode 20 is an alternate long and short dash line, the upper electrode 60 is a broken line, and the light emitting region H is hatched. Is shown. In the plan view of the present embodiment, the same lines and hatching as in FIG. 1A are employed.
[0069]
As shown in FIG. 1, this example includes a plurality of pixels Y and B each including a yellow pixel Y having a yellow emission color and a blue pixel B having a blue emission color. Of these pixels Y and B, two pixels Y and Y having the same emission color, and B and B are adjacently arranged in the same plane, such as YYBBYYBB. In addition, the part U enclosed with the thick line in Fig.1 (a) is 1 unit of repetition.
[0070]
As shown in FIG. 1A, for each pixel Y and B, the vertical pitch of one pixel is P1, the horizontal pitch is (L2 + S2) for pixels of the same color, and (L2 + S1) for pixels of different colors. ). Here, the magnitude relationship is S2 <S1. Further, the light emitting area H in the pixels Y and B has a vertical size L3 and a horizontal size L2. The interval between the lower electrodes 10 is S1, and the interval between the upper electrodes 60 is (P1-L3).
[0071]
As shown in FIG. 1B, the cross-sectional configuration of each pixel Y, B is formed on a glass substrate 1 with a lower electrode 10, a hole injection layer 20, a hole transport layer 30, light emitting layers Y40, B40, electrons. A transport layer 50 and a cathode 60 are sequentially formed. The organic layers 55 such as the organic layers 20, 30, Y 40, B 40, 50 are sandwiched between the electrodes 10, 60.
[0072]
And in this embodiment, the light emitting layer in the adjacent pixel of the same color is an integrated one that is continuous between the adjacent pixels of the same color. That is, as shown in FIG. 1B, the adjacent yellow pixels Y share approximately one half of the continuous integral yellow light emitting layer Y40, and the adjacent blue pixels B share the continuous integral blue light emission. The layer B40 is shared almost by half.
[0073]
The material of each layer 10-60 in this example is described. The lower electrode 10 can be made of ITO (indium tin oxide) or indium-zinc oxide, and has a thickness of, for example, about 100 nm to 1 μm. Here, it is made of ITO as a transparent electrode having a thickness of about 150 nm, formed by sputtering or the like, and patterned in a stripe shape by photoetching.
[0074]
Further, looking at the distances S1 and S2 between the lower electrodes 10, the distance S2 between the lower electrodes 10 between adjacent pixels having the same emission color is equal to the distance S1 between the lower electrodes 10 between pixels having different emission colors. It is narrower than.
[0075]
The hole injection layer 20 is made of copper phthalocyanine (CuPc) having a thickness of 10 nm, and the hole transport layer 30 is made of α-naphthylphenylbenzene having a thickness of 40 nm.
[0076]
The light emitting layer Y40 of the yellow pixel Y is a layer having a thickness of 40 nm made of Alq3 (aluminum quinolinol) which is a host and doped with 5% rubrene, and the light emitting layer B40 of the blue pixel B is formed of perylene on BAlq which is a host. This is a layer having a thickness of 40 nm and made of 1% doped with 1 wt.
[0077]
The electron transport layer 50 is made of Alq3 having a thickness of 20 nm. The cathode 60 is formed by sequentially laminating 0.5 nm thick LiF and 90 nm Al (aluminum) from the lower side. These hole injection layer 20 to cathode 60 are formed by vacuum deposition.
[0078]
The yellow light-emitting layer Y40 and the blue light-emitting layer B40 are formed by selectively depositing, for example, the yellow light-emitting layer Y using a mask made of a metal such as glass or stainless steel having openings corresponding to the light-emitting layers, and then the position of the mask. The film is formed by shifting and aligning and selectively depositing the blue light emitting layer B40.
[0079]
In contrast, the organic layers 20, 30, 50 above and below the light emitting layers Y 40, B 40, that is, the hole injection layer 20, the hole transport layer 30, and the electron transport layer 50 are collectively deposited on the entire surface of the substrate 1. Thus, the film is configured as a film that is continuously integrated between the plurality of pixels Y and B.
[0080]
In this example, the lower electrode 10 is configured as an anode, and the upper electrode 60 is configured as a cathode, both of which are striped. Here, as shown in FIG. 1, the upper and lower electrodes 10 and 60 are orthogonal to each other, and this orthogonal region is configured as a light emitting region H.
[0081]
In this organic EL panel, a forward bias voltage is applied between the upper and lower electrodes 10 and 60 in the light emitting region H of each pixel Y and B, and when no light is emitted, a reverse bias voltage is used to prevent crosstalk. By applying a pulse voltage such that is applied, each of the light emitting layers Y40 and B40 is caused to emit light and display.
[0082]
In this example, in addition to the yellow and blue emission colors, yellow and blue have a complementary color relationship, so that white emission by simultaneous emission of both colors is possible. Thus, in the pixels Y and B having two different luminescent colors, an organic EL panel capable of emitting white light can be realized if the luminescent colors are complementary to each other.
[0083]
By the way, according to the present embodiment, two or more pixels having the same emission color are adjacent to each other among the plurality of pixels Y and B, and the emission layers Y40 and B40 in the adjacent pixels having the same emission color are adjacent to each other. In this configuration, the pixels having the same emission color are continuously integrated. Hereinafter, this configuration is referred to as “same emission color adjacent configuration”.
[0084]
Conventionally, as shown in FIG. 14, pixels of different emission colors, for example, pixel Y and pixel B, are repeatedly arranged so that adjacent pixels have different emission colors such as YBYBYB. Was. In this case, as described above, a thin film portion is formed by thinning the end portions of the light emitting layers Y40 and B40 separately formed in the organic layer 55 between adjacent pixels, which may cause a short circuit. There is sex.
[0085]
On the other hand, according to the present embodiment, a thin film portion may occur between adjacent pixels Y and B having different emission colors, but adjacent pixels Y and Y, B having the same emission color. Since the light emitting layers Y40 and B40 are continuous and integrated between B, the thin film portion does not exist between the adjacent pixels having the same light emission color.
[0086]
Therefore, unlike the technique described in Patent Document 1, the occurrence probability of the thin film portion in the panel is reduced by the area of adjacent pixels of the same emission color without overlapping the light emitting layers between the pixels. The
[0087]
Therefore, according to the present embodiment, the light emitting layer is not necessarily overlapped between adjacent pixels, and the organic layer 55 existing between adjacent pixels is not reduced without reducing the area of the light emitting region H of the pixel. A short circuit between the upper and lower electrodes 10 and 60 due to the thin film portion can be appropriately reduced.
[0088]
Further, in this embodiment, as shown in FIG. 1A, the spacing S2 of the lower electrode 10 between adjacent pixels Y and Y of the same emission color, and B and B is adjacent to the pixel Y of different emission color. Is smaller than the interval S1 of the lower electrode 10 between B and B. Such a configuration is brought about by the above-described adjacent configuration of the same emission color.
[0089]
Since the light emitting layers Y40 and B40 are integrated without being separated between adjacent pixels Y and Y, and B and B having the same light emitting color, the interval S2 of the lower electrode 10 between the pixels is equal to the light emitting layer Y40, It is not necessary to secure an interval corresponding to the mask film formation of B40.
[0090]
However, since the light emitting layer Y40 and the light emitting layer B40 are separately formed between adjacent pixels Y and B having different light emitting colors, the interval S1 of the lower electrode 10 between them corresponds to the mask formation of the light emitting layer. It is necessary to secure the interval.
[0091]
That is, the interval S1 of the lower electrode 10 between pixels of different emission colors is defined in consideration of the alignment accuracy of the mask when depositing different emission layers, the wraparound of the vapor deposition material under the mask, and the like. On the other hand, the interval S2 of the lower electrode 10 between pixels of the same emission color is defined by the photoetching accuracy of the lower electrode.
[0092]
The accuracy of photoetching is generally higher than the deposition accuracy of the vapor deposition method using a mask. Therefore, the interval S2 between the lower electrodes 10 can be made narrower between adjacent pixels having the same light emission color in accordance with the photoetching accuracy than between pixels having different light emission colors.
[0093]
In addition, since the interval S2 can be made narrower than S1 as described above, there is an advantage that the aperture ratio of the pixel, that is, the light emitting region can be increased as compared with the conventional case. This will be described with reference to FIG. 1A and FIG. 14 with an example of specific dimensions.
[0094]
First, in the conventional device shown in FIG. 14, the spacing S1 of the lower electrodes 10 is 40 μm, the vertical pitch P1 of one pixel is 240 μm, the horizontal pitch (L1 + S1) is 120 μm, the vertical size L3 of the light emitting region H is 200 μm, and the horizontal size. L1 is designed to be 80 μm.
[0095]
On the other hand, in the present example shown in FIG. 1A, the distance S1 = 40 μm between the lower electrodes 10 between the pixels having different emission colors is the same, but the distance between the lower electrodes 10 between the pixels having the same emission color. S2 can be narrowed to 20 μm. In this example, the vertical pitch P1 of one pixel is 240 μm, the horizontal pitch {L1 + (S1 + S2) / 2} = 120 μm, the vertical size L3 of the light emitting region H is 200 μm, and the horizontal size L2 is 90 μm.
[0096]
In this example, the horizontal pitch of one pixel is an average value of two pixels, which is one unit. Further, the lateral size L2 of the light emitting region H can be designed to be wide because the interval S2 of the lower electrode 10 between pixels of the same light emitting color is narrower than the conventional electrode interval.
[0097]
Here, the aperture ratio is expressed as a percentage obtained by dividing “the area of the light emitting region H” by “the area of one pixel (that is, the product of the vertical pitch and horizontal pitch of one pixel)”. In the above dimensional example, the aperture ratio is 56% in the conventional example, whereas it is 63% in this example, and an increase in the aperture ratio of 7% can be obtained even at the initial design level.
[0098]
Furthermore, in the present embodiment, a case where one light emitting layer is partially overlapped with the other light emitting layer due to an error in film formation between adjacent pixels Y and B having different light emission colors is considered. However, it is more advantageous than the conventional one in terms of the aperture ratio.
[0099]
For example, in the thing of FIG. 14, suppose that blue light emitting layer B40 overlapped with the width | variety of 5 micrometers at the left-right both ends of the yellow light emitting layer Y40. When the same error occurs in this example shown in FIG. 1A, the blue light emitting layer B40 overlaps with a width of 5 μm only at one end of the left and right ends of the yellow light emitting layer Y40.
[0100]
That is, conventionally, an overlapping portion having a total width of 10 μm is generated, and the overlapping portion becomes a non-light emitting portion, whereas in this example, the reduction of the light emitting region H is half that of 5 μm. Then, if the aperture ratio at the design level is integrated with the influence of the reduction of the light emitting area due to this overlapping portion, the aperture ratio is 49% in the conventional art and 59% in this example, and the deviation of 5 μm during film formation becomes the aperture ratio. A difference of 10%.
[0101]
As described above, according to the present embodiment, there is an advantage that the area of the light emitting region H can be increased rather than reducing the area of the light emitting region H of the pixel.
[0102]
Further, in the example shown in FIG. 1A, the shape of each pixel Y, B is a rectangle, and pixels having the same emission color in a narrow direction, that is, a horizontal direction in the figure, as the aspect ratio of the rectangular pixel. Y and Y, B and B are adjacent to each other.
[0103]
As described above, the light emitting layers Y40 and B40 are usually formed by a vacuum deposition method using a mask having an opening. And the thickness of this mask is prescribed | regulated by the minimum dimension width | variety of an opening part. That is, the narrower the width, the thinner the mask, and the wider, the thicker.
[0104]
As in this example, if pixels having the same light emission color are adjacent to each other in the narrow width direction as the aspect ratio of the rectangular pixels Y and B, the minimum dimension width of the opening of the mask for forming the light emitting layer is increased. be able to. When two pixels are adjacent to each other, the width of the light emitting layer having the same light emission color is widened by two pixels as compared to the conventional case (see FIGS. 1A and 14), and the thickness of the mask can be increased.
[0105]
The fact that the thickness of the mask can be increased means that the rigidity of the mask can be increased. And it becomes easy to use as a mask for large area panels, and there exists an advantage that the enlargement of a panel can be aimed at.
[0106]
Incidentally, pixels having the same emission color may be adjacent to each other in a wide direction as the aspect ratio of the rectangular pixels, for example, in the vertical direction of FIG. However, in this case, the lengths of the light emitting layers Y40 and B40 in the vertical direction are increased, but the lengths of the light emitting layers Y40 and B40 in the horizontal direction are not changed. Therefore, the minimum dimension width of the opening of the mask for forming the light emitting layer does not change, and the thickness of the mask cannot be increased.
[0107]
Further, in this example, the plurality of pixels Y and B are composed of the two different colors Y and B, but the luminance reduction characteristic is good among the two colors Y and B. It is preferable that the other pixel emits light with high luminance.
[0108]
In an organic EL panel, generally, the luminance decreases faster as the luminance is increased, that is, the luminance life is shortened. Therefore, if the pixel having the better luminance reduction characteristic among the two color pixels Y and B is made to emit light with high luminance, the degree of reduction in the luminance characteristic between the two different color pixels can be made similar. This is preferable.
[0109]
In this example, initial 300 cd / m²The blue light emitting layer B40 has a luminance half life of 2000 hours, whereas the yellow light emitting layer Y40 has a luminance half life of 10,000 hours. Therefore, by driving the yellow light emission luminance to be set to 5 times the blue light emission luminance as the single color light emission luminance, the luminance life of both colors can be adjusted to the same level and display with less burn-in can be realized. Become.
[0110]
Next, a modification of this embodiment will be shown. FIG. 2 is a schematic plan view of an organic EL panel as a first modification of the present embodiment.
[0111]
In the example of FIG. 2, the plurality of pixels includes a green pixel G having a green emission color and a red pixel R having a red emission color, which are colors that are not complementary to each other. Of these plural pixels G and R, two pixels G and G having the same emission color, R and R are adjacently arranged in the same plane, such as GGRRGGRR. A portion U surrounded by a thick line in FIG. 2 is one unit of repetition.
[0112]
In the example of FIG. 1, one light emitting layer is formed in units of two pixels in the horizontal direction and one pixel unit in the vertical direction. However, in the example of FIG. The pixel unit is formed in a stripe shape so as to extend over all pixels in the vertical direction. That is, a film having a stripe-shaped opening may be used as a light-emitting layer deposition mask.
[0113]
In this first modification, for example, a green light emitting layer in which 1% coumarin is doped in aluminum quinolinol (Alq3), and 1% 4- (dicyanomethylene) -2-methyl-6- (p-dimethylamino) in Alq3. A combination of a red light emitting layer doped with styryl) -4H-pyran (DCM1) and the like can be employed.
[0114]
For example, when used for in-vehicle use, red display of a warning display and green display indicating that the function is normal are possible. Furthermore, the display which calls attention can be achieved by yellow which mixed these red and green light and mixed color.
[0115]
FIG. 3 is a schematic plan view of an organic EL panel as a second modification of the present embodiment. In the example of FIG. 3, the plurality of pixels includes a red pixel R having a red emission color, a green pixel G having a green emission color, and a blue pixel B having a blue emission color.
[0116]
Of these pixels R, G, and B, two pixels R and R, B, and B having the same emission color are adjacently arranged in the same plane as RRGBBGRRGBB. A portion U surrounded by a thick line in FIG. 3 is one unit of repetition.
[0117]
In the second modification, the effect of the present embodiment is expressed for the pixels R and B. Further, when determining this arrangement, it is desirable to bring the green pixel G in FIG. 3 with a color having a long luminance life and a color with high luminous efficiency and a required luminance.
[0118]
FIG. 4 is a schematic plan view of an organic EL panel as a third modification of the present embodiment and a color filter combined therewith. In FIG. 4, (a) is a color filter 70, (b) is an organic EL panel, and the color filter 70 is bonded to the organic EL panel shown in (b) in this arrangement.
[0119]
In the example of FIG. 4, the plurality of pixels includes a red pixel R having a red emission color and a blue pixel B having a blue emission color. Of these plural pixels R and B, two pixels R and R having the same emission color, and B and B are adjacently arranged repeatedly in the same plane as RRBBRRBBB.
[0120]
Also in this example, as in FIG. 2, each light emitting layer has a stripe shape in the vertical direction. The color filter 70 is provided with a green filter portion 71 that transmits green and a yellow filter portion 72 that transmits yellow, and other regions are transparent.
[0121]
When this color filter 70 is arranged on the organic EL panel of FIG. 4B, the green filter portion 71 overlaps part of the blue pixel B and the yellow filter portion 72 overlaps part of the red pixel R. To do.
[0122]
The half width of the emission spectrum of the organic EL material is wide. For example, even red emission has yellow and orange components. Therefore, as in the third modified example, by combining the color filter 70, the emission color of the pixels can be made different.
[0123]
In this example, as shown in a schematic chromaticity diagram in FIG. 5, four colors of red, blue, yellow, and green and a mixed color thereof can be emitted. In this way, even if the light emission color of a pixel is two colors, further multicolor light emission is possible, and as a result, it is possible to support full color. The same effect can be obtained by using a color conversion filter made of a phosphor instead of the color filter.
[0124]
In the present embodiment, two pixels having the same light emission color are adjacent to each other, for example, YYBBYYBBYYB..., But may be three or more adjacent to each other, for example, YYYBBBYYYBBB.
[0125]
In these methods, attention must be paid to the fact that if the repeating unit is too large, the quality of the display such as shakiness is deteriorated, and furthermore, the luminescent colors are mixed and difficult to recognize. In general, it is said that the color mixing distance should be 200 times as long as the repeating unit, and is considered depending on the setting of the display to be used. For example, when the repeating unit is 1 mm, it is necessary to look at a distance of 200 mm (20 cm) or more. With this in mind, it is necessary to set the maximum value of the repeating unit.
[0126]
(Second Embodiment)
FIG. 6 is a schematic cross-sectional view of an organic EL panel according to the second embodiment of the present invention. The outline of the planar configuration of the organic EL panel shown in FIG. 6 can be the same as that shown in FIG.
[0127]
In other words, in this example, the yellow pixel Y having a yellow emission color and the blue pixel B having a blue emission color are adjacent to each other in pixels Y and B having different emission colors such as YBYBYB. It is repeatedly arranged in the same plane.
[0128]
As shown in FIG. 6, each pixel Y, B has a lower electrode 10, a hole injection layer 20, a hole transport layer 30, a light emitting layer Y40, B40, an electron transport layer 50 on the glass substrate 1, The cathode 60 is formed sequentially. The organic layers 55 such as the organic layers 20, 30, Y 40, B 40, 50 are sandwiched between the electrodes 10, 60.
[0129]
The material of each layer 10-60 in this example is described. The lower electrode 10 can be made of ITO (indium tin oxide) or indium-zinc oxide, and has a thickness of, for example, about 100 nm to 1 μm.
[0130]
Here, the lower electrode 10 is made of ITO as a transparent electrode having a thickness of about 150 nm, is formed by sputtering or the like, and is patterned by stripes extending in the direction perpendicular to the paper surface in FIG. 6 by photoetching. It is.
[0131]
The hole injection layer 20 is made of copper phthalocyanine (CuPc) having a thickness of 10 nm, and the hole transport layer 30 is made of α-naphthylphenylbenzene having a thickness of 40 nm.
[0132]
The light emitting layer Y40 of the yellow pixel Y is a layer having a thickness of 40 nm made of Alq3 which is a host doped with 5% of rubrene, and the light emitting layer B40 of the blue pixel B is doped with 1% of perylene to the host BAlq. This is a layer of 40 nm thickness.
[0133]
The electron transport layer 50 is made of Alq having a thickness of 20 nm. The cathode 60 is formed by sequentially laminating 0.5 nm thick LiF and 90 nm Al (aluminum) from the lower side. These hole injection layer 20 to cathode 60 are formed by vacuum deposition.
[0134]
The yellow light-emitting layer Y40 and the blue light-emitting layer B40 are formed by selectively depositing, for example, the yellow light-emitting layer Y using a mask made of a metal such as glass or stainless steel having openings corresponding to the light-emitting layers, and then the position of the mask. The film is formed by shifting and aligning and selectively depositing the blue light emitting layer B40.
[0135]
In contrast, the organic layers 20, 30, 50 above and below the light emitting layers Y 40, B 40, that is, the hole injection layer 20, the hole transport layer 30, and the electron transport layer 50 are collectively deposited on the entire surface of the substrate 1. Thus, the film is configured as a film that is continuously integrated between the plurality of pixels Y and B.
[0136]
In this example, the lower electrode 10 is configured as an anode, and the upper electrode 60 is configured as a cathode, both of which are striped. The upper electrode 60 has a stripe shape extending in the left-right direction in FIG. 6 by vapor deposition using a mask.
[0137]
As shown in FIG. 6, the upper and lower electrodes 10 and 60 are orthogonal to each other, and the orthogonal region is configured as a light emitting region H. That is, the planar pixel arrangement configuration is a dot matrix type pixel configuration.
[0138]
In this organic EL panel, in the light emitting region H of each pixel Y and B, a forward bias voltage is applied between the upper and lower electrodes 10 and 60 when light is emitted, and a reverse bias voltage is applied to prevent crosstalk when light is not emitted. By applying a pulse voltage to be applied, each light emitting layer Y40, B40 is caused to emit light and display.
[0139]
By the way, as shown in FIG. 6, since the light emitting layers Y40 and B40 are separated and formed, the end portions of the light emitting layers Y40 and B40 are thinned. Therefore, a thin film portion 55 a in which the light emitting layers Y 40 and B 40 are thinner than the light emitting region H is formed in the organic layer 55 in the periphery of the light emitting region H in the pixels Y and B. Note that the light emitting layer is thin also includes the case where the light emitting layer is eliminated.
[0140]
This is because, as described above, when a film is formed by vapor deposition using a mask for each of the light emitting layers Y40 and B40 having different emission colors, the vapor deposition depends on the alignment accuracy of the mask and the distance between the mask and the substrate. This is because a portion where the end portions of the light emitting layers Y40 and B40 become thin (or disappear) is generated due to the influence of the wraparound of the material.
[0141]
Then, in the thin film portion 55a formed between the adjacent pixels Y and B, a portion where the distance between the upper and lower electrodes 10 and 60 becomes narrower than necessary occurs, and a short circuit between the upper and lower electrodes 10 and 60 is likely to occur.
[0142]
With respect to such a problem, in the organic EL panel of the present embodiment, when a reverse bias voltage equal to or lower than the withstand voltage of the thin film portion 55a in the voltage application condition at the time of use is applied, the thin film portion 55a can be open broken. A unique configuration is adopted.
[0143]
Specifically, in the dot matrix type organic EL panel of this example, a pulse voltage of a driving waveform having a predetermined duty ratio and pulse width as shown in FIG. 7 is applied to one pixel Y or B. The When the forward bias voltage (forward pulse) is applied, the light emitting layer Y40 or B40 emits light, and when the reverse bias voltage (reverse bias pulse) is applied, the light emitting layer Y40 or B40 is in a non-light emitting state.
[0144]
The drive waveform as shown in FIG. 7 is a voltage application condition at the time of use in the organic EL panel. In this embodiment, a reverse bias voltage equal to or lower than the withstand voltage of the thin film portion 55a in the voltage application condition at the time of use is applied. Sometimes, the thin film portion 55a can be broken open.
[0145]
The breakdown voltage of the thin film portion 55a is determined based on the voltage measured in the same state as the pulse width defined by the duty ratio, frequency, etc. when actually driving. That is, in the drive waveform shown in FIG. 7, the reverse bias voltage that stops emitting light is set as the breakdown voltage while the forward current remains constant (that is, the light emission luminance is substantially constant) and the magnitude of the reverse bias voltage is increased.
[0146]
Here, as shown in FIG. 8, the reverse bias voltage is changed by a method of increasing the holding time for each voltage by several V while keeping the holding time for each voltage between 5 seconds and 1 minute. In this way, when the reverse bias voltage is increased, a part or all of the thin film portion 55a is scattered. The value of the reverse bias voltage when this scattering occurs is defined as the breakdown voltage of the thin film portion 55a.
[0147]
According to this method, a substantially constant value can be obtained as the withstand voltage of the thin film portion 55a under the voltage application condition during use. Although not limited, in this example, the forward bias voltage is fixed at 10 V, and the holding time is 5 seconds at each reverse bias voltage, and the voltage is increased by 1 V from 20 V, thereby reducing the breakdown voltage of the thin film portion 55 a. Can be sought.
[0148]
Furthermore, since the organic EL panel S1 of this example has a plurality of pixels Y and B, there are a plurality of thin film portions 55a, and the breakdown voltage of the thin film portions 55a has a certain distribution.
[0149]
Specifically, in this example, as a result of examining the breakdown voltage of the thin film portion 55a for the plurality of thin film portions 55a, the distribution shown in FIG. 9 was obtained. The breakdown voltage of the thin film portion 55a in this example is the average value, that is, the average breakdown voltage (26V in FIG. 9).
[0150]
Thus, in the organic EL panel in which the withstand voltage of the thin film portion 55a is defined in the voltage application condition at the time of use, in this embodiment, when a reverse bias voltage equal to or lower than the withstand voltage of the thin film portion 55a is applied, the thin film portion 55a can be broken open.
[0151]
According to this, the value of the reverse bias voltage for self-repair can be determined to an appropriate magnitude using the withstand voltage of the thin film portion 55a under the voltage application condition during use as an index.
[0152]
That is, in the voltage condition applied during use (see FIG. 7 above), the reverse bias voltage applied during non-light emission is set to a magnitude equal to or lower than the breakdown voltage of the thin film portion 55a, thereby including the normal portion of the thin film portion 55a. It is possible to prevent an excessive reverse bias voltage from being set such that the entire thin film portion 55a is scattered.
[0153]
Even if the reverse bias voltage has a magnitude equal to or smaller than the breakdown voltage of the thin film portion 55a, the self-repair can be sufficiently performed. This is because the portion of the thin film portion 55a that is broken open is a defective portion that is likely to cause a short circuit, so that even if a reverse bias voltage lower than the breakdown voltage of the thin film portion 55a is applied, the thin film portion 55a of the defective portion is scattered. This is considered to be because sufficient voltage energy and Joule heat can be generated.
[0154]
Further, since the breakdown voltage of the thin film portion 55a is used as an index, the reverse bias voltage is allowed to be smaller than the breakdown voltage. Therefore, it can be prevented that the reverse bias voltage is too small and the open breakdown becomes insufficient.
[0155]
Specifically, when the thin film portion 55a is broken open, a part of the thin film portion 55a, specifically, a portion of the thin film portion 55a as a defective portion that is easily short-circuited is scattered, and the upper and lower electrodes 10 are scattered in the scattered portion. Between 60 is to be electrically open. Actually, the upper electrode 60 on the upper portion of the thin film portion 55a is scattered along with the scattered thin film portion 55a.
[0156]
As described above, according to the present embodiment, the defective portion of the thin film portion 55a in use can be open-destructed, so that it is not necessary to adopt a configuration in which the light emitting layer is necessarily overlapped between adjacent pixels. The area of the region is not reduced. And the short circuit of the upper and lower electrodes 10 and 60 resulting from the thin film part 55a of the organic layer 55 which exists between adjacent pixels can be reduced appropriately.
[0157]
[Preferred means]
Next, preferred means in the present embodiment will be listed. In the organic EL panel of the present embodiment, when the breakdown voltage of the thin film portion 55a is expressed by the electric field strength per unit thickness of the thin film portion 55a, the conductive organic film is removed from the thin film portion 55a when calculating the electric field strength. And the field strength is 3.4 × 10⁶It is preferable that it is V / cm or more.
[0158]
FIG. 10 is a diagram showing the relationship between the thickness (nm) of the organic layer 55 and the average breakdown voltage (V) of the organic layer 55 investigated by the inventors in the example of the material described above in the present embodiment. . In FIG. 10, the thickness of the organic layer 55 excludes the thickness of the hole injection layer 20 made of CuPc, which is a conductive organic film.
[0159]
In FIG. 10, in the example of the film thickness described in the present embodiment, the value of the organic layer 55 in the light emitting region H and the value of the thin film portion 55a of the organic layer 55 are also shown by a black circle plot and a white circle plot, respectively. is there.
[0160]
As shown in FIG. 10, since the thickness and the breakdown voltage of the organic layer 55 are in a substantially linear relationship, in the organic EL panel, the breakdown voltage of the thin film portion 55a is applied to the thin film portion 55a regardless of the type of organic material. When a conductive film exists, it can be seen that the thin film portion 55a excluding the thickness of the conductive film can be defined by the total thickness.
[0161]
And about the thin film part 55a, it is 3.4x10.⁶It was experimentally confirmed that the open breakdown of the thin film portion 55a described above can be appropriately realized when the electric field strength is V / cm or more. Incidentally, the breakdown voltage of the thin film portion 55a is 3.4 × 10 4 at the above electric field strength.⁶It has also been found that when it is less than V / cm, problems such as scattering of the upper electrodes of all the pixels are likely to occur.
[0162]
The reverse bias voltage is Vr, and the thickness of the thin film portion 55a is the thickness obtained by removing the light emitting layers Y30 and B30 from the thin film portion 55a. That is, as the thickness of the thin film portion 55a, the thickness of the thin film portion 55a including only the other organic layers 20, 30, and 50 without the light emitting layer is defined as Dy. The ratio Vr / Dy between Vr and Dy is Ya.
[0163]
Further, as the thickness of the organic layer 55 in the light emitting region H, a thickness Ty obtained by adding the thickness of the light emitting layers Y40 and B40 to the thickness Dy of the thin film portion 55a is used, and the ratio Vr / Ty between these Vr and Ty. Is Za.
[0164]
In this embodiment, the value Ya is 1.4 × 10 4 for the value Ya (= Vr / Dy) and the value Za (= Vr / Ty).⁶V / cm or more and the value Za is 1.4 × 10⁶V / cm or more 2.4 × 10⁶V / cm or less is preferable.
[0165]
When these values Ya and Za are small, when the same reverse bias voltage Vr is considered, the thin film portion 55a and the organic layer 55 in the light emitting region H are thick, and when these values Ya and Za are large, the thin film portion 55a and the light emission. The case where the organic layer 55 of the area | region H is thin is shown.
[0166]
A constant electric field strength is required to open and destroy the defective portion of the light emitting region H together with the thin film portion 55a, but if it is too high, the upper electrodes of all the pixels will not emit light due to scattering. On the other hand, regarding the thin film portion 55a, even if the upper electrode 60 in that portion scatters, the thin film portion 55a is a peripheral portion of the pixel, so that there is no problem with light emission.
[0167]
Therefore, the inventors examined the relationship between the value Ya (= Vr / Dy) and the value Za (= Vr / Ty) and the short-circuit rate of the upper and lower electrodes 10 and 60 in the organic EL panel of the present embodiment. . The result is shown in FIG.
[0168]
In FIG. 11, the upper and lower electrodes 10 and 60 generated in the thin film portion 55 a and the light emitting region H after the endurance time as the usage time is 1000 hours, that is, after the organic EL panel is driven for 1000 hours. The occurrence rate of short circuits (for example, line defects) is shown.
[0169]
The horizontal axis represents the reverse bias / organic film thickness (V / cm) as a notation including the value Ya (= Vr / Dy) and the value Za (= Vr / Ty). In FIG. 11, the solid line graph indicates the value Ya (= Vr / Dy), and the broken line graph indicates the value Za (= Vr / Ty). Actually, these two graphs overlap each other, and both values Ya and Za have the same tendency in relation to the short-circuit rate of the upper and lower electrodes.
[0170]
From FIG. 11, the ratio Vr / Dy = Ya is 1.4 × 10.⁶In the case of less than V / cm, it can be seen that the thin film portion 55a is too thick or the reverse bias voltage is too small, and the thin film portion 55a is not sufficiently scattered and is not easily broken open.
[0171]
The ratio Vr / Ty = Za is 1.4 × 10⁶In the case of less than V / cm, the organic layer 30 in the light emitting region H is too thick or the reverse bias voltage is too small, and the scattering of the organic layer 30 and the upper electrode 40 becomes insufficient. I find it difficult.
[0172]
On the other hand, the ratio Vr / Ty = Za is 2.4 × 10.⁶If it is larger than V / cm, the organic layer 30 in the light emitting region H is scattered too much, which causes a significant deterioration in display quality.
[0173]
From such examination results, the value Ya is 1.4 × 10 4 for the value Ya (= Vr / Dy) and the value Za (= Vr / Ty).⁶V / cm or more and the value Za is 1.4 × 10⁶V / cm or more 2.4 × 10⁶It has been found that if it is V / cm or less, not only the defective portion of the thin film portion 55a but also the defective portion of the light emitting region H can be reliably broken open and self-repaired.
[0174]
In the organic EL panel of the present embodiment, when the reverse bias voltage is Vr, the thickness of the upper electrode 60 is Da, and the ratio Vr / Da between these Vr and Da is Xa, Xa (= Vr / The value of Da) is 2.2 × 10⁶It is preferable that it is V / cm or more.
[0175]
In the open breakdown of the thin film portion 55a, the upper electrode 60 on the upper portion of the thin film portion 55a is also scattered along with the scattered thin film portion 55a. Therefore, if the reverse bias voltage is too small or the upper electrode 60 is too thick, the upper electrode 60 is unlikely to scatter and is difficult to break open. That is, if the value of Xa (= Vr / Da) is too small, open breakage is difficult.
[0176]
Therefore, the inventors examined the relationship between the ratio Vr / Da = Xa and the short-circuit rate of the upper and lower electrodes 10 and 60 in the organic EL panel of the present embodiment. The result is shown in FIG. In FIG. 12, the short-circuit rate of the upper and lower electrodes has the same definition as in FIG.
[0177]
From FIG. 12, the ratio Vr / Da = Xa is 2.2 × 10.⁶In the case of less than V / cm, the upper electrode 60 is too thick or the reverse bias voltage is too small and the scattering of the upper electrode 60 is insufficient and the thin film portion 55a is not easily broken open, but the ratio Vr / Da = Xa is 2.2 × 10⁶It can be seen that if V / cm or more, the open break can be appropriately performed.
[0178]
Note that, as described above, even if the upper electrode 60 in the thin film portion 55a is scattered, the thin film portion 55a is a peripheral portion of the pixel, so that there is no problem with light emission. For this reason, the reverse bias voltage may be increased if only the thin film portion 55a is broken open. However, depending on the arrangement form of the upper and lower electrodes, if the thin film portion 55a is scattered too much, the upper electrode is disconnected, so care must be taken.
[0179]
For example, when the planar configuration of the organic EL panel of the present embodiment is the pixel layout shown in FIG. 14, the thin film portion 55 a crosses the width direction of the upper electrode 60. In this case, if the thin film portion 55a is scattered too much, the upper electrode 60 may be disconnected.
[0180]
On the other hand, FIG. 13 is a schematic plan view showing an organic EL panel as a modification of the present embodiment. Here, for identification, the boundaries of the pixels Y and B having different emission colors are indicated by solid lines, the lower electrode 20 is indicated by an alternate long and short dash line, the upper electrode 60 is indicated by a broken line, and the light emission region H is indicated by hatching.
[0181]
In this example, the plurality of pixels are composed of a yellow light emitting layer and a blue light emitting layer extending in the vertical direction, and are composed of a yellow pixel Y having a yellow light emission color and a blue pixel B having a blue light emission color. Become. Then, as shown in FIG. 13, the plurality of pixels Y and B are repeatedly arranged in the same plane so as to be adjacent to each other such as YYBBYYBB...
[0182]
The upper electrode 60 has a stripe shape extending in the vertical direction along the light emitting layer. In such a layout, since the thin film portion exists along the left and right end portions of the upper electrode 60, even if the thin film portion is scattered too much, there is very little possibility that the upper electrode 60 is disconnected.
[0183]
As described above, when the planar configuration of the organic EL panel is the pixel layout shown in FIG. 14, a reverse bias voltage for open breakdown of the thin film portion 55a is applied as compared with the layout of FIG. It is necessary to suppress the excessive scattering of the thin film portion 55a.
[0184]
For example, the organic EL panel adopting the example of the material and film thickness of the present embodiment described above, and having the layout shown in FIG. 14 and the layout shown in FIG. I will show you.
[0185]
In the former, when the thickness of the upper electrode 60 is 60 nm and the reverse bias voltage is relatively low 14 V, the value Xa (= Vr / Da) is 2.3 × 10.⁶V / cm, value Ya (= Vr / Dy) is 2.3 × 10⁶V / cm, value Za (= Vr / Ty) is 1.4 × 10⁶V / cm.
[0186]
In the latter case, the reverse bias voltage can be made relatively high, and when it is 20 V, the value Xa (= Vr / Da) is 2.6 × 10 6.⁶V / cm, value Ya (= Vr / Dy) is 3.3 × 10⁶V / cm, value Za (= Vr / Ty) is 2 × 10⁶V / cm.
[0187]
Thus, when there is a possibility that the upper electrode 60 is disconnected due to the open breakdown of the thin film portion 55a, the ratio Vr / Dy = Ya indicating the breakdown voltage of the thin film portion 55a is 1.4 × 10.⁶It is preferable to set a relatively low reverse bias voltage in the range of V / cm or more.
[0188]
In this embodiment, for example, the pixels Y and B having different emission colors are arranged as YBYBYB..., But the arrangement form is not particularly limited. For example, FIG. As shown in the above, it may be arranged such that pixels of the same emission color are adjacent, such as YYBBYYBB.
[0189]
Of course, the emission colors of the plurality of pixels are not limited to the above colors. Furthermore, the plurality of pixels may be an organic EL panel that emits light of the same color, that is, a single color. In short, the present invention is applicable as long as a thin film portion is formed around the pixel by forming the light emitting layer separately.
[0190]
(Other embodiments)
In each of the above embodiments, the material, size, shape, and the like constituting the upper and lower electrodes and each organic layer are not limited to the examples described above, and the design is appropriately changed to the material, size, etc. that can constitute the organic EL panel. You may do it.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a multi-color type organic EL panel according to a first embodiment of the present invention, where (a) is a schematic plan view and (b) is a schematic cross-sectional view.
FIG. 2 is a schematic plan view of an organic EL panel as a first modification of the first embodiment.
FIG. 3 is a schematic plan view of an organic EL panel as a second modification of the first embodiment.
FIG. 4 is a schematic plan view of an organic EL panel as a third modification of the first embodiment.
FIG. 5 is a schematic chromaticity diagram showing an effect of a color filter in the third modified example.
FIG. 6 is a schematic cross-sectional view of an organic EL panel according to a second embodiment of the present invention.
FIG. 7 is a diagram illustrating an example of a drive waveform as a voltage application condition when used in an organic EL panel.
FIG. 8 is a diagram showing a method of increasing the reverse bias voltage in order to determine the breakdown voltage of the thin film portion.
FIG. 9 is a diagram illustrating an example of a breakdown voltage distribution obtained by examining the breakdown voltage of a thin film portion for a plurality of thin film portions.
FIG. 10 is a diagram showing the relationship between the thickness of the organic layer and the average breakdown voltage of the thin film portion investigated by the present inventors.
FIG. 11 is a diagram showing the relationship between the reverse bias / organic film thickness and the short-circuit rate of the upper and lower electrodes.
FIG. 12 is a diagram showing the relationship between reverse bias / upper electrode thickness and upper and lower electrode short-circuit rates.
FIG. 13 is a schematic plan view of an organic EL panel as a modification of the second embodiment.
FIG. 14 is a schematic plan view of a conventional general multi-color type organic EL panel.
FIG. 15 is a schematic cross-sectional view of a conventional general multi-color type organic EL panel.
[Explanation of symbols]
10 ... lower electrode, 20 ... hole injection layer, Y40 ... yellow light emitting layer,
B40 ... Blue light emitting layer, 55 ... Organic layer, 55a ... Thin film part, 60 ... Upper electrode,
70: Color filter, H: Light emitting area, Y: Yellow pixel, B: Blue pixel.

Claims (2)

A plurality of pixels (Y, B) having an organic layer (55) including at least a light emitting layer (Y40, B40) between the lower electrode (10) and the upper electrode (60) are arranged in the same plane. In the organic EL panel formed,
In the periphery of the light emitting region (H) of the pixel, the organic layer forms a thin film portion (55a) in which the light emitting layer is thinner than the light emitting region,
When applying a reverse bias voltage equal to or lower than the withstand voltage of the thin film portion in the voltage application conditions at the time of use, the thin film portion can be open broken ,
When the breakdown voltage of the thin film portion (55a) is expressed by the electric field strength per unit thickness of the thin film portion, the conductive organic film (20) is excluded from the thin film portion when calculating the electric field strength, The electric field strength is 3.4 × 10 ⁶ V / cm or more,
The reverse bias voltage is Vr, the thickness of the thin film portion (55a) excluding the light emitting layer (Y40, B40) from the thin film portion is Dy, and the ratio Vr / Dy between these Vr and Dy is Vr / Dy. When Ya is used, the Ya is 1.4 × 10 ⁶ V / cm or more,
The thickness Ty obtained by adding the thickness of the light emitting layer to the thickness Dy is used as the thickness of the organic layer (55) in the light emitting region (H), and the ratio Vr / Ty of the Vr and Ty is defined as Za. The organic EL panel is characterized in that the Za is 1.4 × 10 ⁶ V / cm or more and 2.4 × 10 ⁶ V / cm or less. When the reverse bias voltage is Vr, the thickness of the upper electrode (60) is Da, and the ratio Vr / Da of these Vr and Da is Xa, the Xa is 2.2 × 10 ⁶ V / cm or more. The organic EL panel according to claim 1 , wherein:

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