JP5646893B2 - Organic EL display device - Google Patents

Description

  The present invention relates to an organic EL display device that controls display of pixels by causing an organic electroluminescence element (hereinafter referred to as an organic EL element) to emit light.

  As a kind of flat panel type display device, an organic EL display device which is a thin and light self-luminous display device has attracted attention. Organic EL display devices include a so-called bottom emission type and top emission type. In a bottom emission type organic EL display device, a transparent electrode (ITO, etc.), an organic multilayer film (organic light emitting layer) that emits light by applying an electric field, and a reflective metal electrode are sequentially formed on an insulating substrate such as a glass substrate. By laminating, an organic EL element (OLED element) which is a light emission mechanism is formed. A large number of organic EL elements are arranged in a matrix on an insulating substrate. Furthermore, the organic EL element is shielded from the external atmosphere by arranging a substrate called a sealing cap so as to cover these laminated structures. When an electric field is applied to the organic EL element between the transparent electrode and the metal electrode, carriers (holes and electrons) are injected into the organic multilayer film, and the organic multilayer film emits light. The bottom emission type organic EL display device emits light from the organic multilayer film to the outside from the glass substrate side.

  On the other hand, in contrast to the bottom emission type, the top emission type organic EL display device is formed by sequentially laminating a reflective metal electrode, an organic light emitting layer, and a transparent electrode such as ITO on a substrate. The organic multilayer film emits light by applying an electric field between the metal electrode and the transparent electrode, and the light is emitted from the transparent electrode side. In the top emission type, a transparent substrate (sealing substrate) suitable for a glass plate is used as a sealing can.

  The light emission principle of the organic EL element is as follows. That is, electrons as one carrier are injected from the cathode into the organic multilayer film containing the organic fluorescent material, and holes as the other carrier are injected from the anode. When both carriers recombine in the organic layer, excitons are generated. Light is emitted when the exciton returns to the ground state. This organic multilayer film is composed of multilayer organic layers stacked on a substrate, and is formed of, for example, four layers of a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer. Further, it may be formed of five organic layers further having an electron injection layer on the electron transport layer (see, for example, Patent Document 1).

JP 2007-95759 A

  The most important issue for organic EL devices is to extend their life. The reason why the luminance and voltage-current characteristics of the organic EL element are lowered as the lighting time elapses is still not fully elucidated. It is pointed out that the cause of deterioration is due to the material, the element structure, the vapor deposition process, etc., but the details are not well understood. An object of the present invention is to provide an organic EL display device using an organic EL element having a long lifetime.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

(1) An organic EL display device including an organic EL element in which a first electrode, an organic layer, and a second electrode are sequentially stacked on one surface of a substrate, wherein the organic layer includes a light emitting layer, A carrier transport layer adjacent to the second electrode side of the light emitting layer, and when the time-of-flight secondary ion mass spectrometry in the depth direction is performed on the organic EL element, the light emitting layer and the Between the maximum value V _Cl of the detection amount of chlorine ions detected in the carrier transport layer and the carbon ion detection amount V _c detected at the depth at which the maximum value is detected,
V _Cl / V _c ≦ 2.5 × 10 ⁻⁵
An organic EL display device characterized by the following relationship:

(2) In the organic EL display device of (1), the relationship of V _Cl / V _c ≦ 2.5 × 10 ⁻⁵ is such that the interface on the carrier transport layer side from the interface on the first electrode side of the light emitting layer. The organic EL display device is characterized in that it is close to the interface of the carrier transport layer and closer to the interface of the light emitting layer than the interface of the second electrode.

  (3) The organic EL display device according to (1), wherein the first electrode is an anode, the second electrode is a cathode, and the carrier transport layer is an electron transport layer. .

(4) An organic EL display device including an organic EL element in which a first electrode, an organic layer, and a second electrode are sequentially stacked on one surface of a substrate, wherein the organic layer includes a light emitting layer, A carrier transport layer adjacent to the second electrode side of the light emitting layer, and when performing time-of-flight secondary ion mass spectrometry in the depth direction for the organic EL element, the light emitting layer Detected amount of fluorine ions detected at a position closer to the carrier transport layer side interface than the first electrode side interface and closer to the light emitting layer side interface than the second electrode side interface of the carrier transport layer Between the maximum value V _F of the carbon ion and the carbon ion detection amount V _c detected at the depth at which the maximum value is detected,
V _F / V _c ≦ 1.0 × 10 ⁻⁴
An organic EL display device characterized by the following relationship:

  (5) In the organic EL display device according to (4), the first electrode is an anode, the second electrode is a cathode, and the carrier transport layer is an electron transport layer. .

  According to the present invention, the lifetime of an organic EL element used in an organic EL display device can be extended. Since the lifetime of the organic EL display device is almost determined by the lifetime of the organic EL element, the lifetime of the organic EL display device can be extended by extending the lifetime of the organic EL element.

It is a schematic cross section explaining the structural example of an organic EL element. It is explanatory drawing of the exciton energy orbit of a dopant molecule. It is explanatory drawing of the exciton energy orbit of a dopant molecule. It is a figure explaining the light emission mechanism of the organic EL element in case a chlorine compound does not exist by an energy level. It is a figure explaining the light emission mechanism of an organic EL element in case a chlorine compound becomes a trap site of a carrier by an energy level. It is a figure which shows an example of the analysis result by TOF-SIMS analysis with respect to the depth direction of an organic EL element. It is a figure which shows the relationship between Cl ion index value and the relative luminance after electricity supply. It is a figure which shows the relationship between F ion parameter | index value and a relative luminance after electricity supply. It is a diagram showing the ratio of the Cl ion detection amount with respect to C ₂ ion detection amount at the interface between the organic layer and the anode, a current supply after the relative brightness, the relationship. It is a top view which shows the structure of the organic electroluminescent display apparatus which concerns on Example 1 of this invention. It is sectional drawing which shows the structure of the organic electroluminescence display which concerns on Example 1 of this invention. It is a figure explaining the comparison result of the element lifetime of the organic electroluminescence display which concerns on Example 1 of this invention, and the organic electroluminescence display which uses the dichloromethane as a mask washing | cleaning liquid. It is a figure which shows the result of the TOF-SIMS analysis of the organic electroluminescence display which concerns on Example 1 of this invention. It is a figure which shows the result of the TOF-SIMS analysis of the organic electroluminescence display which uses a dichloromethane as a mask washing | cleaning liquid. 1 is a cross-sectional view illustrating an example of a configuration near one pixel in a bottom emission type organic EL display device according to an embodiment of the present invention.

  First, the operation principle of the organic EL element will be described.

  FIG. 1 is a schematic cross-sectional view illustrating a structural example of an organic EL element. As shown in the figure, when an organic EL element is manufactured, a first electrode (here, an anode AND) is first formed on one surface (main surface) of an insulating substrate SUB1 formed of glass or the like. Is formed using ITO (Indium Tin Oxide) or the like. On the anode AND, the hole transport layer HTL, the light emitting layer EML, the electron transport layer ETL, and the electron injection layer EIL are sequentially formed by vapor deposition of an organic material or the like. An organic layer OL is formed by the hole transport layer HTL, the light emitting layer EML, the electron transport layer ETL, and the electron injection layer EIL. Further, a second electrode (here, cathode CTD) is formed on the organic layer OL. Here, the organic layer OL is formed of four layers, but the organic layer OL may further include a hole injection layer HIL below the hole transport layer HTL (insulating substrate SUB1 side). Further, the electron injection layer EIL may not be included.

  The hole injection layer HIL and the hole transport layer HTL have a function of transporting holes (holes) injected from the anode AND to the light emitting layer EML, and the electron injection layer EIL and the electron transport layer ETL are injected from the cathode CTD. A function of transporting electrons to the light emitting layer EML. The light emitting layer EML is generally an organic film in which a guest material (dopant) having a fluorescence emission function is co-deposited on a host material having a function of transporting carriers (holes, electrons), and holes injected from the hole transport layer HTL. The electrons injected from the electron transport layer ETL are recombined within the molecules in the light emitting layer EML. Here, when holes and carriers are recombined in the dopant molecule, direct excitons are formed. On the other hand, when the exciton of the host molecule is formed by recombination within the host molecule, the exciton of the dopant molecule is formed by transferring the energy to the dopant.

  2A and 2B are explanatory diagrams of exciton energy trajectories of dopant molecules. As shown in FIG. 2A, the dopant exciton formed as described above has one electron in the highest occupied orbital HOMO (Highest Occupied Molecular Orbital) and one hole in the lowest unoccupied orbital LUMO (Lowest Unoccupied Molecular Orbital). Is an excited molecule. Here, since a material having a high fluorescence quantum yield is used as the dopant in the organic EL element, the dopant excitons emit fluorescence and return to the ground state. FIG. 2B shows the energy trajectories of the dopant molecules when returning to this ground state.

  The above is an example of a normal light emission process of the organic EL element. However, the current organic EL element has a problem that the efficiency gradually decreases when light is emitted for a long time, and solving this problem is the most important issue of the organic EL element.

  Hereinafter, the deterioration phenomenon of the organic EL element will be described in more detail. When the organic EL element emits light by continuously energizing with a constant current amount, two deterioration phenomena mainly occur. The first is a phenomenon in which the luminance gradually decreases, and the second is a phenomenon in which the voltage gradually increases. The first decrease in luminance is considered to be caused by a decrease in the efficiency of dopant exciton generation in the light emitting layer EML. The second voltage increase is considered to be caused by a decrease in mobility in each transport layer or an increase in the carrier injection barrier at the interface. However, the chemical reactions that cause these degradations are not well understood.

  The present inventors have found from experiments that one of the factors that cause deterioration of the organic EL element is contamination of halogen compounds in a clean room or a vapor deposition apparatus. The halogen compound here specifically refers to a chlorine compound and a fluorine compound. As the halogen compounds in the clean room, those derived from resins, tap water, human bodies and the like are conceivable. Moreover, as a halogen compound in a vapor deposition apparatus, what originates from the residue etc. of the used liquid and the washing | cleaning liquid for members is considered.

  As the chlorine compound contained in the organic layer OL, both an organic substance and an inorganic substance containing a chlorine atom in the molecule are conceivable, and there may be an organic hydrochloride, hydrochloric acid, and the like. Specific examples include vinyl chloride, vinylidene chloride, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, sodium chloride in a clean room, and chloromethane, dichloromethane, chloroform, trichloroethylene, tetrachloroethylene, etc. Is mentioned. As for the fluorine compound, both organic and inorganic substances containing fluorine atoms in the molecule can be contained in the organic layer OL. Specific examples include fluorine resins such as hydrogen fluoride and Teflon (registered trademark) in a clean room or a vapor deposition apparatus.

  When the halogen compound adhering to the insulating substrate SUB1 formed with ITO and the halogen compound incorporated in the vapor deposition film are energized to cause the organic EL element to emit light, the decomposition reaction gradually proceeds due to an electrochemical reaction, and the carrier It will be a trap site. Hereinafter, the difference in the light emission mechanism of the organic EL element depending on the presence or absence of the halogen compound will be described with reference to FIGS. In FIGS. 3 and 4, the organic layer OL is composed of four layers of a hole injection layer HIL, a hole transport layer HTL, a light emitting layer EML, and an electron transport layer ETL.

  FIG. 3 is a diagram for explaining the light emission mechanism of the organic EL element in the absence of a halogen compound by the energy level. When the organic EL element is energized, the hole injection layer material and the hole transport layer material are oxidized to radical cations, and the electron transport layer material is reduced to radical anions. When these radical cations and radical anions oxidize or reduce adjacent molecules, carriers are transported one after another. In FIG. 3, the radical anion indicating a hole is indicated by “-”, and the radical cation indicating an electron is indicated by “+”.

  In general, radical cations and radical anions are in a relatively unstable state, but as materials used for the organic EL element, stable materials that do not cause structural changes even in such radical ion states are selected. Therefore, in an organic EL element that does not contain impurities, as shown in FIG. 3, carriers are transported to the light emitting layer EML by repeating oxidation and reduction between adjacent molecules. However, when a halogen compound is contained in the organic layer OL, this halogen compound reacts with the radical cation of the hole injection layer material or the hole transport layer material and the radical anion of the electron transport layer material, and the following FIG. As shown, a level for trapping carriers is formed.

  FIG. 4 is a diagram for explaining the light emission mechanism of the organic EL element when the halogen compound serves as a carrier trap site, based on energy levels. In the hole injection layer HIL and the hole transport layer HTL, holes are trapped by the trap sites and are positively charged, so that the mobility decreases. For this reason, a higher voltage is required to flow a constant current. Similarly, in the electron transport layer ETL, electrons are trapped by the trap sites and are negatively charged, so that the mobility is also lowered. For this reason, a higher voltage is required to flow a constant current.

As shown in FIG. 4, in an organic EL element in which a halogen compound serves as a trap site, the voltage applied between the cathode CTD and the anode AND may be ΔV ₀ shown in FIG. 3 in the initial state, but after deterioration, A voltage of ΔV ₁ shown in FIG. 4 is required. That is, the voltage to be applied increases by (ΔV ₁ −ΔV ₀ ). Also, when a trap is formed at the interface, the voltage rises because charge is accumulated. In addition, since both holes and electrons are injected into the light emitting layer EML, when the halogen compound in the light emitting layer EML is altered, both hole traps and electron traps are formed and the voltage rises. The trap formed in the light emitting layer EML due to the alteration of the halogen compound causes a decrease in luminance as well as an increase in voltage. That is, recombination of holes and electrons injected into the light emitting layer occurs in the altered halogen compound molecule. Since the altered halogen compound does not have the ability to emit fluorescence, the recombination energy is converted into heat. That is, the altered halogen compound becomes a heat deactivation site.

  The present inventors investigated how much the lifetime of the organic EL element is reduced when a halogen compound is incorporated into the organic EL element. Below, the investigation result about the organic EL element which contained the chlorine compound as a halogen compound first is shown.

Specifically, dichloromethane was used as a chlorine compound, and dichloromethane was co-evaporated at various concentrations to produce a plurality of organic EL devices having different chlorine compound contents. Each of these organic EL elements is analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) while performing ion milling, so that the depth of the organic EL element can be determined. The profile of the detected amount of Cl ion in the vertical direction was evaluated. Then, the correlation between the measured Cl ion intensity and the element lifetime was evaluated. Here, when performing TOF-SIMS, Bi ₃ ⁺⁺ ions were used as the primary ion source, Cs ⁺ ions were used as the ion milling species, and the acceleration voltages were 25 kV and 2 kV, respectively.

The results of the above measurement are shown in FIGS. FIG. 5 shows the detection time (intensity) of Cl ions (chlorine ions) and C ₂ ions (carbon ions) measured as a result of the TOF-SIMS analysis for one organic EL element, the processing time from the start of ion milling. Is a graph plotted against. The horizontal axis of the graph represents the processing time from the start of ion milling, and corresponds to the distance in the depth direction from the surface of the cathode CTD. In addition, the vertical axis of the graph represents the detected amount of each ion measured. The detected amount value is the number of ions detected per unit time and unit area. The larger the detected amount value of chlorine ions, the more chlorine compounds are contained at the position where the value is measured. It shows that.

As shown in FIG. 5, in the organic EL element containing a chlorine compound, Cl ions are observed in the organic layer OL. In particular, in the organic layer OL, near the interface between the light emitting layer EML and the electron transport layer ETL (that is, the interface far from the insulating substrate SUB1 of the light emitting layer EML) (Cl circle ion). The peak appears. That is, the position where the detected amount of Cl ions is maximum in the electron transport layer ETL and the light emitting layer EML is closer to the interface on the electron transport layer ETL side than the interface on the anode AND side of the light emitting layer EML, and the electron transport layer ETL. The cathode CTD side interface is closer to the light emitting layer EML side interface. In this embodiment, the vicinity of the interface between the electron transport layer ETL and the light emitting layer EML is ± 10 nm including the interface between the electron transport layer ETL and the light emitting layer EML (a depth of 10 nm from the interface to the electron transport layer ETL side, To the light emitting layer EML side). On the other hand, C ₂ ions attributed to the organic compound constituting the organic layer OL are also observed, but the detected amount of C ₂ ions is substantially constant in the organic layer OL. Therefore, hereinafter, in the organic layer OL, a position where a peak of the detected amount of Cl ions appears between the electron transport layer ETL and the light emitting layer EML (that is, detection of Cl ions in the electron transport layer ETL and the light emitting layer EML). The ratio (V _Cl / V _c ) of the maximum detection amount V _Cl of Cl ions to the detection amount V _c of C ₂ ions (V _Cl / V _c ) at the position where the amount is the maximum value) It is used as an index value indicating the Cl ion intensity at the interface between the two. This index value is hereinafter referred to as a Cl ion index value.

FIG. 6 shows the relationship between the relative luminance at the time when a predetermined energization time (here, 12 hours) has elapsed (that is, the ratio of the luminance after elapse of the predetermined time to the luminance at the start of energization) and the Cl ion index value. The plotted results are shown. In addition, the organic EL elements plotted in FIG. 6 use a plurality of organic EL elements having different detection amounts of Cl ions in the vicinity of the interface between the light emitting layer EML and the electron transport layer ETL, and each organic EL element has a predetermined time. Energized. In FIG. 6, for example, if the relative luminance is 1.0, there is no change in the luminance at the start of energization and the luminance after continuous energization. Usually, after energization, the organic EL element begins to deteriorate and the luminance decreases. The closer this relative luminance is to 1.0, the better the device lifetime. From the experiment, as shown in FIG. 6, it was found that the organic EL element having a larger Cl ion index value has a lower relative luminance after being energized for a predetermined time. This indicates that the organic EL element having a larger Cl ion index value in the vicinity of the interface between the light emitting layer EML and the electron transport layer ETL deteriorates the element lifetime. From the graph of FIG. 6, it can be seen that when the Cl ion index value exceeds 2.5 × 10 ⁻⁵ , the relative luminance rapidly deteriorates after energization. It can also be seen that when the Cl ion index value is 2.5 × 10 ⁻⁵ or less, the relative luminance after energization is about 1.0, and the lifetime of the organic EL element is significantly improved.

From the above results, when the TOF-SIMS analysis was performed on the organic EL element under the above-described measurement conditions, the maximum value V _Cl of the detected amount of Cl ions in the light emitting layer EML and the electron transport layer ETL, and the maximum value There the detection amount V _C of C ₂ ions detected at a position to be detected, by manufacturing the organic EL element the following relationship holds, it is possible to significantly improve the device life.
V _Cl / V _C ≦ 2.5 × 10 ⁻⁵

The same tendency was confirmed also about the organic EL element containing a fluorine compound. Here, similarly to the Cl ion index value, C ₂ ion detection at a depth at which the detected amount of F ions in the electron transport layer ETL and the light emitting layer EML is measured as a result of the TOF-SIMS analysis is maximum. the F ions to the amount _{V C} ratio of the maximum value _{V F} detected amount of (fluorine ion) _(V F / _{V C),} the index value indicating the F ionic strength at the interface between the light emitting layer EML and the electron transport layer ETL It will be used as (F ion index value). FIG. 7 shows the relationship between the relative luminance and the F ion index value when a predetermined energization time has elapsed after energizing each of a plurality of organic EL elements produced by changing the content of the fluorine compound. The results of plotting are shown. As shown in FIG. 7, as in the case of Cl ions, it was found that the organic EL element having a larger F ion index value has a worse element lifetime. From the graph of FIG. 7, it can be seen that the lifetime of the organic EL element is improved when the F ion index value decreases to the measurement limit (1.00 × 10 ⁻⁴ ) or less.

From the above, when the TOF-SIMS analysis is performed on the organic EL element under the above-described measurement conditions, the maximum value V _F of the detected amount of F ions in the light emitting layer EML and the electron transport layer ETL and the maximum value are detected. The lifetime of the element can be improved by producing an organic EL element that satisfies the following relationship with respect to the detected amount V _C of C ₂ ions detected at the position where it is detected.
V _F / V _C ≦ 1.0 × 10 ⁻⁴

In the above description, both the Cl ion and the F ion have a problem of a peak appearing at the interface between the light emitting layer EML and the electron transport layer ETL. Here, as shown in FIG. 5, a peak of the detected amount of Cl ions also appears at the interface between the hole transport layer HTL and the anode AND. However, the halogen compound present at the interface with the anode AND has a relatively small influence on the lifetime of the organic EL element as compared with the halogen compound present at the interface between the light emitting layer EML and the electron transport layer ETL. I understood that. 8, as in FIG. 6, each of the plurality of organic EL elements is energized, and the relative luminance and (Cl ion detection amount peak value) / (C ₂ ) when a predetermined energization time has elapsed. The result of plotting the relationship between the value of the detected ion amount and the value is shown. However, unlike FIG. 6, in FIG. 8, the value is calculated using the peak position of the detected amount of Cl ions appearing at the interface between the hole transport layer HTL and the anode AND. As can be seen from this figure, there is no clear correlation between the detected amount of Cl ions measured at the interface between the hole transport layer HTL and the anode AND and the element lifetime of the organic EL element. Thus, the correlation with the lifetime of the organic EL element is the Cl ion content (detected amount) in the vicinity of the interface between the light emitting layer EML and the electron transport layer ETL. The lifetime of the organic EL element can be improved by reducing the amount of Cl ions detected in the vicinity of the interface between the light emitting layer EML and the electron transport layer ETL. In the present embodiment, the maximum value V _Cl of the detected amount of Cl ions in the 20 nm depth direction region (in the range of ± 10 nm depth from the interface) including the interface between the electron transport layer ETL and the light emitting layer EML, The relationship of the detection amount V _C of C ₂ ions detected at the position where the maximum value is detected satisfies V _Cl / V _C ≦ 2.5 × 10 ⁻⁵ . Alternatively, in a 20 nm depth direction region (a range of ± 10 nm depth from the interface) including the interface between the electron transport layer ETL and the light emitting layer EML, the maximum value V _F of the detected amount of F ions and the maximum value are The relationship of the detection amount V _C of C ₂ ions detected at the detected position satisfies V _F / V _C ≦ 1.0 × 10 ⁻⁴ .

  Hereinafter, examples of the organic EL display device including the organic EL element having the above-described features will be described. FIG. 9A is a plan view schematically showing the structure of the organic EL display device according to the first embodiment. FIG. 9B is a cross-sectional view schematically showing the structure of the organic EL display device, and shows a state in which the organic EL display device shown in FIG. 9A is cut along the line IXB-IXB.

  The organic EL display device according to Example 1 was manufactured as follows. That is, first, a silicon oxide film was formed by CVD on one surface of a glass insulating substrate SUB1 having a plate thickness of 7 mm and a vertical and horizontal size of 50 mm × 50 mm. The silicon oxide film is a so-called base film. An ITO film serving as an anode was formed thereon by sputtering, and then a 1 mm wide stripe pattern was formed by a photo process, thereby forming an anode AND.

  NPD, Alq3 doped with coumarin, Alq3, and lithium were sequentially deposited on the 20 mm × 20 mm portion of the central portion of the insulating substrate SUB1 as an organic layer OL constituting the organic EL element to form an organic EL element structure. The thicknesses were 60 nm, 30 nm, 20 nm, and 1 nm, respectively. Next, aluminum having a width of 1 mm (thickness: 200 nm) was deposited so as to be orthogonal to the anode AND to form a cathode CTD. Finally, the sealing cap SUB2 loaded with the desiccant DCN was placed on the insulating substrate SUB1, and the periphery of the sealing cap SUB2 was sealed using the UV curable sealing material SL.

In this example, attention was focused on a mask for vapor deposition of an organic material (hereinafter referred to as vapor deposition mask) as a source of chlorine compounds mixed into the organic EL element. The vapor deposition mask is used particularly when the light emitting layer EML is formed in the organic layer OL. The light emitting layer EML is vapor-deposited separately for each of these emission colors in order to form pixels corresponding to each emission color such as red (R), green (G), and blue (B). For this reason, when vapor-depositing the second and subsequent light-emitting layers EML, a vapor deposition mask is disposed so as to cover the light-emitting layers EML of other colors already deposited on the insulating substrate SUB1. However, the vapor deposition mask is heated at the time of vapor deposition, so that the substance attached to the surface is likely to volatilize, and is a member closest to the insulating substrate SUB1. Therefore, it is considered that the vapor deposition mask is one of the members that most easily contaminate the organic EL element. Furthermore, since the vapor deposition mask is arranged so as to cover the light emitting layer EML as described above, in particular, the interface opposite to the insulating substrate SUB1 side of the light emitting layer EML (here, between the light emitting layer EML and the electron transport layer ETL). It is assumed that the interfacial interface is likely to be contaminated. In general, the deposition mask is washed with dichloromethane (chemical formula: CH ₂ Cl ₂ ) for the purpose of efficiently removing the attached organic material. Such a halogen compound is added to the organic EL element. When mixed, the organic material may be altered due to its high reactivity. From these, it was considered that by not using dichloromethane for cleaning the vapor deposition mask, mixing of dichloromethane into the organic EL device can be avoided and the device life can be improved. Note that when the first color light emitting layer EML is deposited, the interface between the light emitting layer EML and the hole transport layer HTL is contaminated with Cl in the second color to third color elements. However, it has been confirmed by experiments that there is no correlation between the Cl ion intensity at the interface between the light emitting layer EML and the hole transport layer HTL and the lifetime of the organic EL element.

  For the organic EL display device according to this example, a measurement was performed to compare the difference in the lifetime of the organic EL element depending on whether or not dichloromethane was used as a mask cleaning liquid. The element lifetime was evaluated by the amount of change in luminance when the organic EL element was energized with a constant direct current. The result is shown in the graph of FIG. In this graph, the plots marked with ◯ show the measurement results of the organic EL display device of this example in which dichloromethane was not used as the mask cleaning liquid, and the plots marked with X were organic manufactured using dichloromethane as a comparative example for mask cleaning. The measurement result of the EL display device is shown. As is clear from this figure, the organic EL display device of this example, in which dichloromethane was not used as a mask cleaning liquid, had less luminance deterioration than the case where dichloromethane was used, and the lifetime was improved. It was confirmed. For example, even when dichloromethane is used, in order to remove foreign matter on the deposition mask immediately before the introduction of the apparatus, the deposition mask is washed with pure water for a long time to remove dichloromethane and reduce Cl ions in the organic EL element. it can.

  Further, the difference in the detected amount of Cl ions in the organic EL element depending on whether or not dichloromethane was used as a mask cleaning solution was compared. As the analysis method for this evaluation, the above-described TOF-SIMS was used. That is, the ion intensity profile in the depth direction of the organic EL element was measured by performing TOF-SIMS analysis while performing ion milling. The measurement results are shown in the graphs of FIGS. 11A and 11B. FIG. 11A shows the measurement result of the organic EL display device according to Example 1, and FIG. 11B shows the measurement result of the organic EL display device manufactured by using dichloromethane for mask cleaning as a comparative example. When both results were compared, when dichloromethane was not used as the mask cleaning liquid, the peak of the detected amount of Cl ions appearing at the interface between the light emitting layer EML and the electron transport layer ETL was smaller than when using dichloromethane. From the above, it was confirmed that by changing the cleaning method of the vapor deposition mask, the amount of chlorine compound mixed in the organic EL element can be reduced and the life of the organic EL display device can be improved. Note that the plurality of organic EL elements having different Cl ion index values shown in the graph of FIG. 6 are also manufactured by changing the cleaning conditions of the vapor deposition mask.

  FIG. 12 is a cross-sectional view illustrating a configuration example near one pixel in a bottom emission type organic EL display device according to an embodiment of the present invention. One pixel includes one organic EL element. Furthermore, the organic EL display device according to the present embodiment is an active matrix type, and a thin film transistor TFT is formed on the main surface of a glass insulating substrate SUB1. A light emitting section is constituted by the anode AND being one electrode driven by the thin film transistor TFT, the cathode CTD being the other electrode, and the organic layer OL sandwiched between these electrodes. The thin film transistor TFT includes a polysilicon semiconductor layer PSI, a gate insulating layer ISI, a gate line (gate electrode) GL, a source / drain electrode SD, and interlayer insulating layers IS2 and IS3.

  The organic layer OL is formed by stacking, for example, a hole transport layer HTL, a light emitting layer EML, an electron transport layer ETL, and an electron injection layer EIL sequentially from the anode AND side. A hole injection layer HIL may be provided below the hole transport layer HTL.

  The anode AND which is a pixel electrode is composed of a transparent conductive layer (ITO or the like) formed on the passivation layer PSV, and the source of the thin film transistor TFT via a contact hole formed in the passivation layer PSV and the interlayer insulating layer IS3. -It is electrically connected to the drain electrode SD. Further, a bank BNK is formed by applying an insulating layer on the anode AND, and an organic layer OL is deposited in a recess surrounded by the bank BNK. The organic layer OL may be formed by a coating means such as inkjet. A cathode CTD is formed of a solid film so as to cover the organic layer OL and the bank BNK.

  Since this organic EL display device is a bottom emission type, light L emitted from the light emitting layer EML is emitted from the surface of the insulating substrate SUB1 to the outside, as indicated by a two-dotted line arrow in the drawing. Therefore, the cathode CTD is formed of a material having light reflectivity. A sealing cap SUB2 (sealing glass substrate) is bonded to the main surface side of the insulating substrate SUB1, and the inside of the seal that goes around a peripheral portion (not shown) is sealed in a vacuum state.

  In the above description, the bottom emission type organic EL display device has been described. However, the organic EL display device according to the embodiment of the present invention may be a top emission type. In the above description, the anode AND is disposed on the insulating substrate SUB1 side and the cathode CTD is disposed on the sealing cap SUB2 side with respect to the organic layer OL. However, the anode AND and the cathode CTD are reversed. May be arranged. Also in this case, the Cl ion index value and the F ion index value measured in the vicinity of the interface opposite to the insulating substrate SUB1 side of the light emitting layer EML (here, the interface between the light emitting layer EML and the hole transport layer HTL) The lifetime of the organic EL display device can be extended by manufacturing the organic EL display device so as to be a predetermined value or less.

  SUB1 insulating substrate, AND anode, OL organic layer, HIL hole injection layer, HTL hole transport layer, EML emission layer, ETL electron transport layer, EIL electron injection layer, CTD cathode, SUB2 sealing cap, DCD desiccant, SL seal material .

Claims (5)

An organic EL display device including an organic EL element in which a first electrode, an organic layer, and a second electrode are sequentially stacked on one surface of a substrate,
The organic layer includes a light emitting layer, a carrier transport layer adjacent to the second electrode side of the light emitting layer,
Including
The light emitting layer includes at least a first light emitting layer that emits light in a first light emitting color, and a second light emitting layer that emits light in a second light emitting color,
The first light emitting layer and the second light emitting layer are deposited separately,
At least one of the first light emitting layer and the second light emitting layer is vapor-deposited using a vapor deposition mask washed with pure water,
When performing time-of-flight secondary ion mass spectrometry in the depth direction with respect to the organic EL element, the maximum value V _Cl of the detected amount of chlorine ions detected in the light emitting layer and the carrier transport layer, Between the carbon ion detection amount V _c detected at the depth at which the maximum value is detected,
V _Cl / V _c ≦ 2.5 × 10 ⁻⁵
An organic EL display device characterized by the following relationship: The organic EL display device according to claim 1,
The relationship of V _Cl / V _c ≦ 2.5 × 10 ⁻⁵ is closer to the interface on the carrier transport layer side than the interface on the first electrode side of the light emitting layer, and the second of the carrier transport layer. An organic EL display device characterized by being formed at a position closer to the light emitting layer side interface than the electrode side interface. The organic EL display device according to claim 1,
The first electrode is an anode;
The second electrode is a cathode;
The organic EL display device, wherein the carrier transport layer is an electron transport layer. An organic EL display device including an organic EL element in which a first electrode, an organic layer, and a second electrode are sequentially stacked on one surface of a substrate,
The organic layer includes a light emitting layer, a carrier transport layer adjacent to the second electrode side of the light emitting layer,
Including
The light emitting layer includes at least a first light emitting layer that emits light in a first light emitting color, and a second light emitting layer that emits light in a second light emitting color,
The first light emitting layer and the second light emitting layer are deposited separately,
At least one of the first light emitting layer and the second light emitting layer is vapor-deposited using a vapor deposition mask washed with pure water,
When performing time-of-flight secondary ion mass spectrometry in the depth direction for the organic EL element, the interface is closer to the carrier transport layer side interface than the first electrode side interface of the light emitting layer, and Detected at a maximum value V _F of the detected amount of fluorine ions detected at a position closer to the interface on the light emitting layer side than the interface on the second electrode side of the carrier transport layer, and at a depth at which the maximum value is detected. Between the detected amount of carbon ions V _c ,
V _F / V _c ≦ 1.0 × 10 ⁻⁴
An organic EL display device characterized by the following relationship: 5. The organic EL display device according to claim 4, wherein the first electrode is an anode.
The second electrode is a cathode;
The organic EL display device, wherein the carrier transport layer is an electron transport layer.

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