JP4479250B2 - Display device manufacturing method and display device - Google Patents

Description

  The present invention relates to a method for manufacturing a display device and a display device obtained thereby, and particularly to a method for manufacturing a display device including an organic electroluminescent element (organic EL element) and the display device.

  In recent years, research and development of a flat display device that is lightweight and consumes little power has been performed as a display device that can replace a cathode ray tube. Among these, a display device including an organic EL element is attracting attention as a display device that is self-luminous, has a high response speed, and can be driven with low power consumption.

  As a configuration for making such an organic EL display device full color, there is a configuration in which organic EL elements that emit blue (B), red (R), and green (G) light are arranged. In this configuration, a configuration of a light emitting element in which an organic layer including a light emitting layer is sandwiched between an anode (anode) and a cathode (cathode) is adopted, and light generated in the light emitting layer is resonated between the anode and the cathode. A configuration in which a microcavity (micro optical resonator) structure is taken out from the anode side or the cathode side has been proposed. With such a configuration, it is possible to improve the color purity of the extracted light and to improve the intensity of the extracted light near the center wavelength of resonance.

Therefore, the optical distances L _B , L _R of the resonator structures in the organic EL elements of the respective colors are matched to the peak wavelengths λ _B , λ _R , λ _G of the extracted light spectrum in the _B , _R , _G organic EL elements. by setting the L _G, respectively, the color purity improvement is being performed. The optical distance L _B, L _R, L _G, in order to maximize the microcavity effect, the respective colors both are determined to be the zero-order interference conditions, long wavelength lambda _R, lambda _G , Λ _B , L _R > L _G > L _B. And the organic layer of the organic EL element of each color has a film thickness corresponding to this optical distance, and the film thickness is formed in the order of R, G, B.

  Here, in general, the organic layer of the organic EL element is separately applied for each color by vapor-depositing an organic layer of each color in a state where a vapor deposition mask is aligned with the substrate by a vacuum vapor deposition method. Thereby, the vapor deposition mask used when vapor-depositing an organic layer of a different color later comes into contact with the organic layer of the previously vapor-deposited color, and the organic layer of the previously vapor-deposited color is damaged, Foreign matter on the evaporation mask is transferred. For this reason, in the organic EL element which has the organic layer vapor-deposited previously, it becomes easy to produce a nonluminous defect, and an organic EL element which has an organic layer formed into a film later suppresses a nonluminous defect.

  In view of this, there is a method in which the organic layer is deposited in the order of decreasing luminance, that is, B, R, and G in consideration of the fact that the visibility of the non-emitting defect increases when the luminance around the non-emitting defect is high. In addition, when the thin organic layer is formed first, the vapor deposition mask comes into contact with the thin organic layer many times, so that non-luminous defects are likely to occur. As described above, a method for depositing an organic layer in the order of R, G, and B has also been reported. Furthermore, in order to prevent contact between the vapor deposition mask and the organic layer, an example in which a protrusion (spacer) is provided in a region where the organic layer is formed has been reported (for example, see Patent Document 1).

JP 2003-59671 A

  However, as described above, when the organic layers of the respective colors are formed in order of decreasing brightness, the thinnest organic layer of B is formed first, so that it is easily affected by the contact of the vapor deposition mask. Non-light emitting defects of the organic EL element increase. In addition, since the organic layer of B under the zero-order interference condition is thin, it tends to be affected by foreign matters on the substrate and irregularities on the electrodes, and there is a tendency for non-luminous defects to increase.

  In addition, when the organic layers of the respective colors are formed in order of film thickness, the organic layer of B is deposited last, so that non-light emitting defects of the organic EL element of B are suppressed, but the organic layer of G is B As a result, the non-light-emitting defect of the G organic EL element having the highest luminance is increased by the contact with the vapor deposition mask. Since the organic EL element of G has high luminance, the visibility of non-luminous defects is high. Furthermore, in the method in which the spacer is provided in the region where the organic layer is formed, the film formation region of the organic layer is reduced by the amount of the spacer. Therefore, when this display device is lit with the same luminance as that without the spacer, There is a problem that the light emission life is reduced.

  For this reason, there has been a demand for an organic EL display device capable of reducing non-light emitting defects in each color organic EL element without reducing the light emission lifetime.

In order to solve the above-described problems, a method for manufacturing a display device according to the present invention includes a step of forming blue, red, and green organic electroluminescent elements having an organic layer including a light emitting layer on a substrate. The step of forming the organic electroluminescent elements of the respective colors includes a step of forming an anode including a reflective layer having a resonator structure on the substrate, and an organic including a light emitting layer corresponding to each color formed on the anode. A step of forming a layer and a step of forming a cathode formed on the organic layer through an electron injection layer, and the organic layers of each organic EL element are made thicker in the order of blue, red, and green. And setting the optical distance between the reflective layer and the cathode to a value at which the emitted light can resonate for each light emitting layer of each color, and the optical distance between the red and green organic electroluminescent elements. Is set to the zeroth order interference condition, and the blue organic electric field Set the optical distance of the optical element to the primary of the interference condition, and at least a light-emitting layer of the organic layer of each organic EL device was blue, red, characterized in that sequentially formed green.

According to the method of manufacturing such a display device, blue, red, that is formed from the green organic layer in this order, the green organic layer to be finally deposited, the contact of the vapor deposition mask is suppressed, contact Damage and transfer of foreign matter are prevented. For this reason, the non-light-emitting defect of a green organic EL element is reduced. Moreover, since the film thickness of the organic layer is set to be thicker in the order of green, red, and blue, the influence of contact with the deposition mask is suppressed by increasing the film thickness of the blue organic layer, and on the substrate. It is also less susceptible to external factors such as foreign matter and electrode irregularities. Therefore, non-light emitting defects of the blue organic EL element are also reduced. Thus, as described in the background art, even if a spacer for preventing contact with the vapor deposition mask is not provided in the film formation region of the organic layer, the influence on the organic layer of the vapor deposition mask is suppressed, and the organic EL element Non-luminous defects are also reduced.

  As described above, according to the display device manufacturing method and the display device obtained thereby according to the present invention, it is possible to reduce non-light emitting defects of the organic EL element without reducing the film formation region of the organic layer. . Therefore, the display quality of the display device can be improved without reducing the light emission lifetime.

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

  FIG. 1 is a cross-sectional view schematically showing a configuration example of a display device obtained by the method for manufacturing a display device of the present invention. In the display device 10 shown in this figure, an organic EL element 12B from which blue (B) light is extracted, an organic EL element 12R from which red (R) light is extracted, and green (G) light are extracted on a substrate 11. This is a full-color display device in which organic EL elements 12G to be formed are arrayed as light emitting elements.

  The organic EL elements 12B, 12R, and 12G have a configuration in which an anode 13, an organic layer 14, an electron injection layer 15, and a cathode 16 are stacked in this order from the substrate 11 side. And it is comprised as a top emission type which takes out the emitted light h generated in the organic layer 14 from the cathode 16 side. Hereinafter, the detailed structure of each member is demonstrated in order of a manufacturing process.

  First, a thin film transistor (TFT) (not shown) is formed on a substrate 11 made of an insulating material such as glass. Then, although not shown here, a flattening film is formed by applying, exposing, developing, and baking, for example, polyimide on the substrate 11 on which the TFT is formed. By forming a contact hole in the planarizing film by this exposure, the anode 13 formed in a later process is connected to the above-described TFT through this contact hole.

  Next, for example, an indium tin oxide (ITO) film 13a, an Ag alloy film 13b, and an ITO film 13c are sequentially laminated from the substrate 11 side on a planarizing film (not shown) by, for example, sputtering in a vacuum atmosphere. A conductive layer is formed. Subsequently, a resist pattern (not shown) is formed on the conductive layer, and the anode 13 is formed by patterning by etching using the resist pattern as a mask. Thereafter, the resist pattern is removed. The Ag alloy film 13b in the anode 13 is used as a reflective layer having a resonator structure described in detail below.

Next, an insulating layer (not shown) for element isolation is formed on the anode 13 by an ordinary lithography technique, thereby separating the formation regions of the organic EL elements 12B, 12R, and 12G of the respective colors. Subsequently, baking is performed in a nitrogen (N ₂ ) atmosphere, and the substrate 11 is pretreated with oxygen (O ₂ ) plasma.

  Next, the organic layer 14B of the organic EL element 12B, the organic layer 14R of the organic EL element 12R, and the organic layer 14G of the organic EL element 12G are formed on the anode 13 by, for example, vacuum deposition. In the present invention, it is characteristic that the film thickness of each organic layer 14B, 14R, and 14G is set in order from the color with the lowest brightness, and the color order with the lower brightness is B, R, and G. The film thicknesses are set in the order of the organic layers 14B, 14R, and 14G. The thicknesses of the organic layers 14B, 14R, and 14G are such that light having a target wavelength among the emitted light h generated in the organic layers 14B, 14R, and 14G is converted into an Ag alloy film 13b (reflective layer) in the anode 13. It is assumed that the film thickness is set so as to allow resonance between the cathode and the cathode 16.

  Here, the resonator structure for setting the film thickness of the organic layers 14B, 14R, and 14G in the display device 10 of the present embodiment will be described in detail. In this display device 10, as will be described later, a cathode 16 is formed on an organic layer 14 </ b> B, 14 </ b> R, 14 </ b> G formed on an anode 13 via an electron injection layer 15. Then, the resonance including the uppermost ITO film 13c in the anode 13, the organic layers 14B, 14R, and 14G and the electron injection layer 15 sandwiched between the Ag alloy film 13b and the cathode 16 in the anode 13 is combined. The part C is configured to resonate light having a target wavelength and extract it from the cathode 16 side.

In the display device 10, in order to obtain a full color display, the emitted light h generated in the light emitting layers 23B, 23R, and 23G has emission intensity in the B, R, and G wavelength regions. Then, the organic EL elements 12B, 12R, in 12G, the optical distance L _B, L _R, L _G between the Ag alloy film 13b and the cathode 16 was set each organic EL element 12B, 12R, the 12G Lights having desired wavelengths λ _B , λ _R , and λ _G are set to values that resonate in the resonance unit C, respectively. In conventional display devices, the optical distance L _B, L _R, L _G is set to be 0 order interference conditions, it has been a _{L R> L G> L B} .

In contrast, in the present embodiment, L _R, and L _G is set in the conventional still zero-order interference condition is set only to a first order interference condition L _B. Thereby, for example, the phase shift generated when the emitted light h generated in the light emitting layers 23B, 23R, and 23G of the organic EL elements 12B, 12R, and 12G is reflected by the Ag alloy film 13b and the cathode 16 is changed to Φ _B and Φ. _R , Φ _G (radian), and the optical distance between the Ag alloy film 13b and the cathode 16 in the organic EL elements 12B, 12R, and 12G is the spectrum of the light extracted from the L _B , L _R, L _G , and cathode 16 sides. When the peak wavelengths are λ _B , λ _R , and λ _G , the optical distances L _B , L _R , and L _G are set to satisfy Equation 3.

As a result, L _R and L _G are set in the q-order interference condition and L _B is set in the (q + 1) -order interference condition in a range where L _B > L _R > L _G. For example, L _R, and L _G a first order interference condition, the L _B may be the second-order interference condition. However, the optical distance L _B, L _R, L _G, like the optical distance L _R, L _G is the positive minimum value, i.e., L _R, and L _G a 0 order interference condition, L _B Is preferably the first order interference condition because the microcavity effect is high. Then, the optical distance L _B, L _R, depending on the L _G, the organic layer 14B, 14R, sets increasing the thickness in the order of 14G.

  Here, for example, the organic layer 14B is composed of a hole injection layer 21B, a hole transport layer 22B, a light emitting layer 23B, and an electron transport layer 24B, as will be described later, but the thickness of the organic layer 14B is set. The film thickness of any of the above layers may be adjusted, and it is set as appropriate depending on the constituent material of each layer. The same applies to the organic layers 14G and 14R.

  Then, the organic layers 14B, 14R, and 14G set in the order of film thickness as described above are formed in this order of film thickness, that is, in order from the color with the lowest luminance. Specifically, the film forming process is performed as follows.

  For example, an evaporation mask (not shown) is aligned on the substrate 11 in a vacuum atmosphere, and the hole injection layer 21B, the hole transport layer 22B, and the light emitting layer 23B are formed on the anode 13 in the formation region of the organic EL element 12B. The blue organic layer 14B is formed by sequentially depositing the electron transport layer 24B.

  Next, while maintaining a vacuum atmosphere, an evaporation mask (not shown) is aligned on the substrate 11, and a hole injection layer 21R, a hole transport layer 22R, a light emitting layer 23R, A red organic layer 14R is formed by sequentially depositing the electron transport layer 24R.

  Thereafter, while maintaining a vacuum atmosphere, an evaporation mask (not shown) is aligned on the substrate 11, and a hole injection layer 21G, a hole transport layer 22G, a light emitting layer 23G, The green organic layer 14G is formed by sequentially depositing the electron transport layer 24G.

  As described above, after the organic layers 14B, 14R, and 14G are formed, an evaporation mask (not shown) is aligned on the substrate 11 in a state where a vacuum atmosphere is maintained, and the organic layers 14B and 14R are formed by vacuum evaporation. , 14G, an electron injection layer 15 made of, for example, lithium fluoride (LiF) is formed. Thereafter, a cathode 16 made of, for example, an MgAg alloy is formed by vacuum deposition using this deposition mask. Since the cathode 16 is on the side from which the emitted light h generated in the organic layers 14B, 14R, and 14G is extracted, the light transmittance is adjusted by the film thickness and the like. A driving power source for current injection, not shown here, is connected between the cathode 16 and the anode 13 described above.

  Next, a deposition mask used for depositing the cathode 16 on the substrate 11 is aligned by sputtering, and a transparent conductive layer (illustrated indium zinc oxide (IZO)) made of, for example, indium zinc oxide (IZO) is formed on the cathode 16. (Omitted). This transparent conductive layer is formed to reduce the electrical resistance of the cathode 16.

Thereafter, a protective film (not shown) made of silicon nitride (SiN _x ) is formed on the transparent conductive layer by chemical vapor deposition (Chemical Vapor Deposition (CVD)) with the mask aligned. Next, resin sealing is performed by applying a thermosetting resin on the peripheral edge of the substrate 11 and heating the glass substrate (not shown) on the resin.

  According to the manufacturing method of such a display device and the display device obtained thereby, the film thicknesses of the organic layers 14B, 14R, and 14G of the organic EL elements 12B, 12R, and 12G are set to be thicker in the order of B, R, and G. The organic layers 14B, 14R, and 14G are formed in this order. Thereby, since the organic layer 14G of the organic EL element 12G is formed last, the contact of the vapor deposition mask is suppressed, and damage to the organic layer 14G and contamination by foreign matter due to this contact are prevented. Therefore, non-light emitting defects of the organic EL element 12G having high luminance can be reduced.

Also, the optical distance L _B of the organic EL element 12B by the first order interference conditions, the film thickness of the organic layer 14B is thinnest set in the case of the conventional zero-order interference conditions, thickest set Is done. As a result, even when the organic layer 14B having a low luminance is first formed, the film thickness is thicker than before, so that the influence of contact with the deposition mask, foreign matter on the substrate 11, irregularities of the anode 13, and the like are external. The influence of factors is suppressed. Therefore, non-light emitting defects of the organic EL element 12B can be reduced.

Furthermore, since the organic layer 14R of the organic EL element 12R is formed second, the optical distances L _B , L _G , and L _R are set as the 0th-order interference conditions as in the conventional case, and the color order in which the film thickness is large is used. That is, compared with the case where the organic layer 14R is formed first, the contact of the vapor deposition mask with the organic layer 14R is suppressed, and the influence of this contact is also suppressed. Therefore, non-light emitting defects of the organic EL element 12R can also be reduced.

  Therefore, the organic layers 14B, 14R, and 14G by the contact of the vapor deposition mask can be provided without providing a spacer for preventing the vapor deposition mask and the organic layers 14B, 14R, and 14G from contacting the film formation region of the organic layers 14B, 14R, and 14G. Can be suppressed, and non-luminous defects of the organic EL elements 12B, 12R, and 12G can be reduced. Therefore, the display quality of the display device 10 can be improved without reducing the light emission lifetime.

  As mentioned above, although this invention was demonstrated by embodiment, this invention is not limited to said embodiment. For example, in the above-described embodiment, an example in which all the layers in the organic layers 14B, 14R, and 14G are formed according to colors in the order of low luminance has been described. However, at least the light-emitting layer 23B, the organic layers 14B, 14R, and 14G are described. 23R and 23G may be formed in order from the color with the lowest luminance. For example, the film thicknesses of the organic layers 14B, 14R, and 14G are different only in the film thickness differences of the light-emitting layers 23B, 23R, and 23G of the respective organic layers, and other than the light-emitting layers 23B, 23R, and 23G in the organic layers 14B, 14R, and 14G. When the layers are made of the same material and these layers can be formed in the same process, only the light emitting layers 23B, 23G, and 23R may be formed in order from the color with the lowest luminance.

  Further, in the above embodiment, the configuration is such that the emitted light h is reflected on the anode 13 side and taken out from the cathode 16 side, that is, the upper surface side formed of a semi-transmissive AgMg alloy. The light emitting light h may be extracted from the anode 13 side, that is, the lower surface side by forming the cathode 16 with a material having high reflectivity.

  Furthermore, by forming the anode 13 and the cathode 16 with a semi-transmissive material, it is possible to have a structure in which the emitted light h is extracted from both sides.

  Further, in the above embodiment, the organic layers 14B, 14R, and 14G are formed on the anode 13 formed on the substrate 11, and the cathode 16 is formed on the organic layers 14B, 14R, and 14G via the electron injection layer 15, and the cathode Although an example in which light is extracted from the 16 side has been described, the organic layers 14B, 14R, and 14G are disposed on the cathode 16 formed on the substrate 11 via the electron injection layer 15 in the reverse stacking order. After the formation, the anode 13 may be formed on these, and light may be extracted from the anode 13 side.

  Further, specific examples of the present invention will be described. In this example, a display device was manufactured by the same method as in the above embodiment.

  First, a planarization film (not shown) provided with a contact hole was formed on the substrate 11 on which the TFT was formed. Next, a conductive layer in which an ITO film 13a, an Ag alloy film 13b, and an ITO film 13c were sequentially laminated from the substrate 11 side was formed on the planarizing film. The film thickness here was ITO film 13a / Ag alloy film 13b / ITO film 13c = about 30 nm / about 100 nm / about 10 nm. Subsequently, the anode 13 was formed by patterning the conductive layer.

Next, an insulating layer (not shown) for element isolation was formed on the anode 13, and the formation regions of the organic EL elements 12B, 12R, and 12G for the respective colors were separated. Subsequently, baking was performed in an N ₂ atmosphere, and the substrate 11 was pretreated with O ₂ plasma.

Next, the substrate 11 is transported to a chamber for forming the organic layer 14B in a vacuum atmosphere, an evaporation mask (not shown) is aligned on the substrate 11, and holes are injected onto the anode 13 of the organic EL element 12B. The organic layer 14B was formed by sequentially depositing the layer 21B, the hole transport layer 22B, the light emitting layer 23B, and the electron transport layer 24B. The film thickness of the organic layer 14B was set according to the optical distance L _B of the first order interference condition, and was about 200 nm.

Next, in a state where the vacuum atmosphere is maintained, the organic layer 14R is transported to a chamber for film formation, an evaporation mask (not shown) is aligned on the substrate 11, and on the anode 13 in the formation region of the organic EL element 12R. The organic layer 14R was formed by sequentially depositing the hole injection layer 21R, the hole transport layer 22R, the light emitting layer 23R, and the electron transport layer 24R. The film thickness of the organic layer 14R was set according to the optical distance L _R of the zeroth-order interference condition, and was about 150 nm.

Thereafter, in a state where the vacuum atmosphere is maintained, the organic layer 14G is transferred to a chamber for film formation, an evaporation mask (not shown) is aligned on the substrate 11, and on the anode 13 in the formation region of the organic EL element 12G. The organic layer 14G was formed by sequentially depositing the hole injection layer 21G, the hole transport layer 22G, the light emitting layer 23G, and the electron transport layer 24G. The film thickness of the organic layer 14G is set according to the optical distance L _G 0 order interference conditions, was about 100 nm.

  Next, in a state where the vacuum atmosphere is maintained, the substrate 11 is transported to a chamber in which the electron injection layer 15 and the cathode 16 are deposited, an evaporation mask (not shown) is aligned on the substrate 11, and the organic layers 14B, 14R, On 14G, an electron injection layer 15 made of LiF was formed to a thickness of about 1 nm. Thereafter, a cathode 16 made of MgAg alloy was formed with a film thickness of about 100 nm using this vapor deposition mask.

  Next, in a state where the vacuum atmosphere is maintained, the substrate 11 is transported to a chamber in which a transparent conductive layer (not shown) is formed by sputtering, and the deposition mask used when the cathode 16 is deposited on the substrate 11 is aligned. A transparent conductive layer made of IZO was formed on the cathode 16 to a thickness of about 100 nm.

Thereafter, in a state where the vacuum atmosphere is maintained, the substrate 11 is transferred to a chamber for forming a protective film (not shown) by the CVD method, and a protective film made of SiN _{x is formed} on the transparent conductive layer with the mask aligned. The film was formed with a film thickness of about 1 μm. Next, a thermosetting resin was applied onto the peripheral edge of the substrate 11, and a resin substrate was sealed by heating in a state where a glass substrate (not shown) was laminated on the resin.

As a comparative example for the present embodiment, as described in the background art, the optical distance L _B, L _R, and L _G a 0 order interference conditions, accordingly, about 70nm film thickness of the organic layer 14B, The film thickness of the organic layer 14R was about 150 nm, and the film thickness of the organic layer 14G was about 100 nm. And it formed into a film for each color in order from the color with a thick film thickness, ie, organic layers 14R, 14G, and 14B. In addition, it carried out by the method similar to an Example except the film-forming process of organic layer 14R, 14G, 14B, and set it as the same structure.

  With respect to the display devices of the obtained examples and comparative examples, the time-dependent change of non-light emitting defects was examined when the display devices were continuously lit at a predetermined current value. The result is shown in FIG. In the graph of FIG. 2, when the number of non-light emitting defects of the blue organic EL element 12B in the comparative example when lit continuously for 340 hours is 100, the organic EL elements 12B, 12R, and 12G of the respective colors in the examples and comparative examples are taken as 100. The time-dependent change of the non-luminous defect is represented.

As shown in this graph, when the change over time of the non-light emitting defects when continuously lit is compared, it is confirmed that the organic EL elements 12B, 12R, and 12G of this example have reduced non-light emitting defects for each color. It was done. In particular, in the comparative example, the non-light-emitting defects of the organic EL element 12B and the organic EL element 12G increased remarkably over time, whereas in the present example, the non-light-emitting defects of the organic EL element 12B and the organic EL element 12G were almost none. It did not increase and was able to improve significantly. That is, only the organic layer 14B and the thickness corresponding to the optical distance L _B of the primary of the interference condition, by depositing in ascending order of brightness, the organic EL element 12B, 12R, the non-emission defects 12G are reduced It was confirmed that

It is typical sectional drawing for demonstrating embodiment which concerns on the manufacturing method of the display apparatus of this invention, and the display apparatus obtained by this. It is a graph which shows the time-dependent change of the non-light-emitting defect number of the organic EL element of each color in the Example and comparative example of this invention.

Explanation of symbols

10 ... display, 11 ... substrate, 12B, 12R, 12G ... organic EL device, 13 ... anode, 14B, 14R, 14G ... organic layer, 16 ... _{cathode, L B, L R, L} G ... optical distance, 23B , 23R, 23G ... light emitting layer

Claims (1)

A step of forming a blue, red, and green organic electroluminescent element having an organic layer including a light emitting layer on a substrate;
The step of forming the organic electroluminescent element of each color,
Forming an anode including a reflective layer having a resonator structure on the substrate;
Forming an organic layer including a light emitting layer corresponding to each color formed on the anode;
Forming a cathode formed on the organic layer through an electron injection layer,
The thickness of the organic layer of each organic electroluminescent element is set to be thicker in the order of blue, red, and green,
The optical distance between the reflective layer and the cathode is set to a value at which the emitted light can resonate for each light emitting layer of each color,
An optical distance between the red and green organic electroluminescent elements is set to a zero-order interference condition; an optical distance between the blue organic electroluminescent elements is set to a first-order interference condition;
A method for manufacturing a display device, wherein at least a light emitting layer of an organic layer of each organic electroluminescent element is formed in the order of blue, red, and green.

Images