JP2011002689A - Active matrix organic el panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active matrix organic EL panel using an oxide, which has uniform optical effect in a pixel.SOLUTION: In one pixel P, at least a semiconductor layer 6 in an element forming area A1 where an active element 3 is formed, is formed of a transparent metal oxide, and a transparent metal oxide layer 16 is formed on the semiconductor layer 6 side of a non-element formation area A2 where no active element 3 is formed.

Description

  The present invention relates to an active matrix organic EL panel using an oxide TFT.

  Among organic EL (Electro Luminescence) (OLED: Organic Light-Emitting Diode) panels, active matrix (AM) driven organic EL panels with a bottom emission (BE) structure in which the light extraction direction of the light emitting layer is on the lower substrate side In order to operate the active elements, it is necessary to set a plurality of active elements per pixel (each sub-pixel), and the proportion of the active elements in one pixel is large.

  In addition, the semiconductor layer is opaque, and the bottom emission structure has a low aperture ratio because only a region where no active element exists is a light emitting pixel.

  Therefore, Patent Document 1 discloses a thin film transistor (TFT) and a driving circuit including a source wiring and a gate wiring having an electrical contact with the thin film transistor as a transparent metal oxide (ITO; Indium-Tin-). An active matrix organic EL panel in which the aperture ratio is increased by being formed of Oxide (indium tin oxide) is disclosed.

JP 2004-14982 A (paragraph 0043 column, FIG. 4)

  However, in Patent Document 1 described above, although the aperture ratio can be increased, an element formation region in which an active element is formed in one pixel is formed of a transparent metal oxide, while a planarization layer ( A non-element formation region where no active element is formed, such as an interlayer insulating film, is formed of a transparent resin material made of polymethyl methacrylate (PMMA), and light emitted from the light emitting layer is transmitted through both regions. Therefore, the spectrum differs due to the influence of the optical effect. Therefore, the light actually observed is a mixed spectrum of a plurality of spectra, which causes a decrease in color purity.

  FIG. 8 shows a cross-sectional configuration of the active matrix organic EL panel, in which A1 is an element formation region, A2 is a non-element formation region, B1 is light transmitted through the element formation region A1, and B2 is a non-element formation region A2. It is the light that passes through. 101 is a glass substrate which is a transparent base plate, 102 is an active element, 103 is a gate insulating film, 104 is a planarization layer (interlayer insulating film), 105 is a transparent electrode (pixel electrode), 106 is an organic EL layer, 107 is Upper electrode.

  The present invention has been made in view of such a point, and an object of the invention is to make the optical effect uniform in the pixel.

  In order to achieve the above object, the present invention is characterized in that, in Patent Document 1, a layer made of a transparent metal oxide is interposed in a non-element forming region where no active element is formed.

  Specifically, the present invention includes a transistor substrate in which an active element is formed on a transparent base plate, and an organic EL layer stacked on the transistor substrate, and the organic EL layer is operated by the operation of the active element. The following solution was taken for an active matrix organic EL panel having a bottom emission structure in which voltage is applied to extract light from the base substrate side.

  That is, in the first invention, in one pixel, at least a semiconductor layer in an element formation region where the active element is formed is formed of a transparent metal oxide, and a non-element formation in which the active element is not formed A transparent metal oxide layer is formed on the side of the semiconductor layer in the region.

  According to a second invention, in the first invention, a color filter layer is interposed between the base substrate, the active element, and the metal oxide layer.

  According to a third aspect, in the first aspect, the average transmittance in the visible light region of the semiconductor layer is 70% or more.

  In a fourth aspect based on the first aspect, the one pixel is composed of at least three sub-pixels, and the color filter layer is divided into at least three in accordance with the sub-pixels, and is different for each sub-pixel. The organic EL layer has an absorption characteristic, and emits light having a different emission wavelength for each sub-pixel so as to match the absorption characteristic of the sub-pixel overlapping the color filter layer.

  In a fifth aspect based on the first aspect, the one pixel includes at least three subpixels, and the color filter layer is partitioned into at least three according to the subpixels. The organic EL layer having different absorption characteristics is a white light-emitting element having at least two emission peaks.

  According to a sixth invention, in the first invention, a portion located in a pixel of the driving circuit having an electrical contact with the active element is formed to be transparent.

  According to the first invention, the light emitted from the light emitting layer of the organic EL layer is transmitted through the semiconductor layer made of a transparent metal oxide in the element forming region, while being transparent on the side of the semiconductor layer in the non-element forming region. A transparent metal oxide layer.

  As described above, since the light transmitted through the element formation region and the non-element formation region are both observed through the transparent metal oxide layer, the light is emitted regardless of whether the light is extracted through the semiconductor layer. There is almost no difference in spectrum, and a light-emitting element having no color mixture can be obtained, which has an advantage that color purity is improved.

In particular, according to the second invention, since the metal oxide material can form a film having an electron mobility of 10 to 20 cm / Vm ² only by vapor deposition or sputtering, a high-temperature heat treatment is unnecessary and the film is formed on the color filter layer. In addition, the film can be formed without any problem, and the organic EL can be driven even when a large panel is formed.

  In other words, since the organic EL is a current element, it is necessary to produce an active element having an electron mobility sufficient to flow a large current in order to drive it. This becomes more significant as the panel becomes larger. For this reason, polysilicon and continuous grain silicon (CGS) that can increase the electron mobility as high as a single crystal are used as a semiconductor layer. However, in order to increase the electron mobility, polysilicon is used. When silicon, CGS, or the like is used as a semiconductor layer, a heat treatment such as laser aryl is required to produce a Si crystal, so that these active elements are formed on the color filter layer formed of resin. Is difficult to form. In the present invention, since the semiconductor layer is a metal oxide as described above, there is no such limitation.

  In organic EL, the thickness of the active element is strongly influenced by optical interference, and the emission color changes depending on the viewing angle. However, by adjusting the chromaticity using the color filter layer, there is no viewing angle dependency. Can be a panel.

  Furthermore, as described above, the light transmitted through the element formation region and the non-element formation region has almost no difference in emission spectrum, and thus has the advantage that the amount of light passing through the color filter layer is increased and the light emission efficiency is improved.

  According to the third invention, when the average transmittance in the visible light region of the semiconductor layer is 70% or more, the optical interference effect can be suppressed, and the luminescent color of the luminescent material itself can be extracted uniformly within the pixel. . Moreover, the angular dependence of the spectrum can be suppressed.

  According to the fourth aspect of the invention, the organic EL layer is color-separated with RGB and color-matched with the color filter layer, so that color display can be performed without reducing the light emission efficiency. Further, by passing through the color filter layer, the color purity can be improved and the viewing angle dependency of the color purity can be reduced.

  According to the fifth aspect of the invention, even if the organic EL layer is a white light emitting element having two light emission peaks, color display can be performed without reducing the light emission efficiency.

  According to the sixth invention, the aperture ratio of the pixel can be increased and the luminance can be increased by changing the wiring region of the wiring portion of the drive circuit to the pixel portion to the transparent metal oxide.

1 is a cross-sectional configuration diagram of an active matrix organic EL panel according to Embodiment 1. FIG. FIG. 3 is a plan view of subpixels in the first embodiment. FIG. 3 is an equivalent circuit diagram of an active element in the first embodiment. FIG. 3 is a diagram corresponding to FIG. FIG. 6 is a view corresponding to FIG. 2 of the third embodiment. FIG. 10 is a plan view of a state where pixel electrodes are removed in the third embodiment. It is sectional drawing in the VII-VII line of FIG. It is a figure equivalent to FIG. 1 of a conventional example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional configuration diagram of an active matrix organic EL panel according to the first embodiment.

  In FIG. 1, reference numeral 1 denotes a glass substrate which is a transparent base plate. On the glass substrate 1, a color filter comprising three primary color layers (red (R), green (G) and blue (B)) ( A CF (Color Filter) layer 2 is formed, and an active element 3 is formed thereon. The active element 3 includes a gate electrode 5 formed on the color filter layer 2 and covered with a gate insulating film 4, and a thin film transistor (TFT) as a switching element formed on the gate insulating film 4. A semiconductor layer 6, a source electrode 7 and a drain electrode 8 formed on both sides of the semiconductor layer 6, a channel protective film 9 located between the source electrode 7 and the drain electrode 8 and covering the semiconductor layer 6. Is covered with a planarizing layer (interlayer insulating film) 10 having a through hole 10a, which constitutes a transistor substrate 11. On the planarizing layer 10 of the transistor substrate 11, a transparent electrode (pixel electrode) 12 made of ITO (Indium-Tin-Oxide) is laminated, and between the drain electrode 8 of the active element 3. Contact is made through the through hole 10a. An organic EL layer 13 having a white light emitting layer is laminated on the transparent electrode 12, and an upper electrode 14 is further laminated thereon. That is, in the first embodiment, the light emitting layer is made of the all-pixel white light emitting material. Thereby, an active matrix organic EL panel having a bottom emission structure in which a voltage is applied to the organic EL layer 13 by the operation of the active element 3 to extract light from the glass substrate 1 side is configured.

  The transparent electrode 12 includes a large number of pixels P, each of which is divided into three subpixels p1, p2, and p3, arranged in a matrix, and has a size that matches the pixel size of the color filter layer 2. Patterned. That is, each color layer of the color filter layer 2 is bordered in order to obtain contrast in the black matrix (BM) layer 15, and the color filter layer 2 is divided into three in accordance with the sub-pixels p1, p2, and p3. So that the subpixels p1, p2, and p3 have different absorption characteristics.

In one pixel P, at least the semiconductor layer 6 in the element formation region A1 where the active element 3 is formed is composed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), oxide A transparent metal oxide layer 16 is formed on the side of the semiconductor layer 6 in the non-element formation region A2 which is formed of a transparent metal oxide such as tin (SnO ₂ ) and in which the active element 3 is not formed. ing. Thus, the color filter layer 2 is interposed between the glass substrate 1 and the active element 3 and the metal oxide layer 16.

  Here, the average transmittance in the visible light region (wavelength of 400 to 780 nm) of the semiconductor layer (metal oxide) 6 forming the active element 3 is 70% or more.

  Therefore, the transparent metal oxide is formed in a wide area over almost the entire transparent electrode 12 (in the pixel P).

  FIG. 2 is a plan view of the sub-pixel p1 (p2, p3) in the first embodiment, in which 17 is a data (source) line, 18 is a scanning (gate) line, 19 is a current supply line, and C is a capacitor. Yes, the other symbols correspond to the symbols used in the description of FIG.

  FIG. 3 shows an example of an equivalent circuit of the active element 3 according to the first embodiment. In the figure, T1 is a switching TFT, T2 is a driving TFT, C is a capita, and O is an organic EL element. Here, the minimum unit of the structure of 2 transistors (2Tr) +1 capacitor (1C): 2Tr1C is illustrated, but not limited to this example, the operation uniformity of the organic EL element and the uniformity of the active element 3 itself are improved. Therefore, a complicated circuit structure including a compensation circuit may be used. Even in this case, the transparent metal oxide is formed in a region other than that used as the active element 3.

  In the active matrix organic EL panel configured as described above, the light emitted from the light emitting layer of the organic EL layer 13 is transmitted through the semiconductor layer 6 made of a transparent metal oxide in the element formation region A1, while the non-element formation region. In A2, the transparent metal oxide layer 16 on the side of the semiconductor layer 6 is transmitted.

  As described above, since light transmitted through the element formation region A1 and the non-element formation region A2 is observed through the layer made of a transparent metal oxide, whether or not the light is transmitted through the semiconductor layer 6 and extracted. Regardless of this, there is almost no difference in emission spectrum, and there can be obtained a light-emitting element having no color mixture, which has the advantage that the color purity is improved.

In addition, since a film having an electron mobility of 10 to 20 cm / Vm ² can be formed only by vapor deposition or sputtering, the metal oxide material can be formed on the color filter layer without any high temperature heat treatment. The organic EL can be driven even when a large panel is formed.

  In other words, since the organic EL is a current element, in order to drive it, it is necessary to produce the active element 3 having an electron mobility that allows a large current to flow. This becomes more prominent as the panel becomes larger. . For this reason, polysilicon or continuous grain silicon (CGS) that can increase the electron mobility as high as that of a single crystal is used as a semiconductor layer. However, in order to increase the electron mobility, poly-silicon is used. When silicon, CGS, or the like is used as the semiconductor layer 6, a heat treatment such as laser aryl is required to produce the Si crystal, and therefore, these are formed on the color filter layer 2 formed of resin. It is difficult to form the active element 3. In the present invention, since the semiconductor layer 6 is a metal oxide as described above, there is no such limitation.

  In the organic EL, the film thickness of the active element 3 is strongly influenced by optical interference, and the emission color changes depending on the viewing angle. However, by adjusting the chromaticity by using the color filter layer 2, the viewing angle dependence is improved. It can be a panel without.

  Further, as described above, the lights B1 and B2 that pass through the element formation region A1 and the non-element formation region A2 have almost no difference in emission spectrum, so that the amount of light passing through the color filter layer 2 is increased and the light emission efficiency is improved. It has the merit that.

  Furthermore, since the average transmittance in the visible light region of the semiconductor layer 6 is 70% or more, the optical interference effect is suppressed, and the luminescent color of the luminescent material itself is made uniform within the pixel P (subpixels p1p2, p3). It can be taken out. Moreover, the angular dependence of the spectrum can be suppressed.

  In addition, by using white light emission, the element is completed by forming the organic EL layer 13 by coating without coating the organic EL layer 13, and color display is possible by combining with the color filter layer 2 in terms of process. A color display element can be easily formed.

(Embodiment 2)
FIG. 4 is a cross-sectional configuration of an active matrix organic EL panel according to the second embodiment. The difference from the first embodiment is that the white light emitting material for all pixels is applied in the first embodiment to the light emitting layer, but in the second embodiment, RGB is separately applied. The other parts are the same as those in the first embodiment, and therefore, the same components are denoted by the same reference numerals and the description thereof is omitted.

  That is, in the color display method using white + CF according to the first embodiment, the light emission of each pixel P (sub-pixels p1p2, p3) is all white, so that approximately one third of the light emission amount is cut by the CF. As a result, the luminous efficiency is greatly reduced.

  Therefore, the RGB pixels P (sub-pixels p1p2, p3) are separately applied as described above, and the light emission color of each pixel P (sub-pixel p1p2, p3) and the color filter layer 2 of each pixel P (sub-pixel p1p2, p3). By matching the absorption colors, the light emission of each pixel P (sub-pixels p1p2, p3) almost passes through the color filter layer 2 and can be displayed in color without reducing the light emission efficiency.

  Further, since the emission color of the organic EL light is broadened by the fluctuation of the organic material, the color purity can be improved by transmitting the color filter layer 2. Furthermore, the viewing angle dependence of color purity can be reduced. Other effects are the same as those of the first embodiment.

  The organic EL layer 13 may be a white light emitting element having at least two light emission peaks. That is, even if the organic EL layer 13 is a white light emitting element having two light emission peaks, color display can be performed without reducing the light emission efficiency.

(Embodiment 3)
5 to 7 are equivalent circuit diagrams of the active element 3 according to the third embodiment. Since the basic configuration is the same as that of the first embodiment, the same components are denoted by the same reference numerals and the description thereof is omitted. Yes. Although not shown, the cross-sectional configuration of the active matrix organic EL panel is the same as in the first and second embodiments. Differences from the first embodiment are as follows.

  That is, in the third embodiment, in the pixel P (sub-pixels p1p2, p3) of the drive circuit (data (source) line 17, scanning (gate) line 18, current supply line 19) having electrical contacts with the active element 3. The portion located at is also made transparent with a transparent metal oxide such as ITO, thereby further increasing the opening in the pixel P (sub-pixels p1p2, p3). A metal such as Al is used for a portion of the wiring electrode that does not cover the pixel. In each drawing, a dotted area is a transparent portion in the pixel P (subpixels p1p2, p3) which is the most characteristic of the third embodiment. In FIG. 7, the right side of the alternate long and short dash line is a pixel P (subpixel p1p2, p3) region.

  Therefore, by making all the electrodes in the pixel P (sub-pixels p1p2, p3) ITO, a decrease in the aperture ratio due to the routing of the wiring resistance that has been left slightly into the pixel is eliminated, and the aperture ratio is further increased. Improvement can be realized and luminance can be increased. Other effects are the same as those of the first embodiment.

  The present invention is useful for an active matrix organic EL panel using an oxide TFT.

1 Glass substrate (base plate)
2 Color filter layer 3 Active element 11 Transistor substrate 13 Organic EL layer 16 Metal oxide layer 17 Data (source) line (drive circuit)
18 Scanning (Gate) Line (Drive Circuit)
19 Current supply line (drive circuit)
A1 Element formation region A2 Non-element formation region P Pixel p1, p2, p3 Subpixel

Claims (6)

A transistor substrate having an active element formed on a transparent base plate and an organic EL layer laminated on the active element side of the transistor substrate, and applying a voltage to the organic EL layer by the operation of the active element An active matrix organic EL panel having a bottom emission structure for extracting light from the base substrate side,
The semiconductor layer of the active element is formed of a transparent metal oxide,
In one pixel, at least the semiconductor layer in the element formation region where the active element is formed is formed of a transparent metal oxide, and is located on the side of the semiconductor layer in the non-element formation region where the active element is not formed. Is an active matrix organic EL panel in which a transparent metal oxide layer is formed. The active matrix organic EL panel according to claim 1,
An active matrix organic EL panel, wherein a color filter layer is interposed between the base substrate, the active element, and the metal oxide layer. The active matrix organic EL panel according to claim 1,
An active matrix organic EL panel, wherein the semiconductor layer has an average transmittance of 70% or more in a visible light region. The active matrix organic EL panel according to claim 1,
The one pixel is composed of at least three subpixels,
The color filter layer is divided into at least three according to the sub-pixel and has different absorption characteristics for each sub-pixel,
2. The active matrix organic EL panel according to claim 1, wherein the organic EL layer emits a different emission wavelength for each of the sub-pixels so as to match the absorption characteristics of the sub-pixel overlapping the color filter layer. The active matrix organic EL panel according to claim 1,
The one pixel is composed of at least three subpixels,
The color filter layer is divided into at least three according to the sub-pixel and has different absorption characteristics for each sub-pixel,
2. The active matrix organic EL panel according to claim 1, wherein the organic EL layer is a white light emitting element having at least two light emission peaks. The active matrix organic EL panel according to claim 1,
An active matrix organic EL panel, wherein a portion of the driving circuit having an electrical contact with the active element is formed transparent.

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