KR102102705B1 - Organic Light Emitting Display Device - Google Patents

Abstract

The present invention is a display panel; And red, green, and blue sub-pixels formed on the display panel, wherein the red, green, and blue sub-pixels are located between the lower electrode and the light emitting layer and each include a mixed layer having hole injection capability and hole transport capability. The mixed layer includes an organic electroluminescence display device characterized in that at least three different materials are mixed.

Description

Organic Light Emitting Display Device

The present invention relates to an organic light emitting display device.

An organic light emitting device used in an organic light emitting display device is a self-emitting device in which a light emitting layer is formed between two electrodes. In the organic electroluminescent device, electrons and holes are injected into the emission layer from the electron injection electrode (cathode) and the hole injection electrode (anode), respectively, and the exciton in which the injected electrons and holes are combined is excited. It is a device that emits light when it falls from the ground to the ground.

An organic light emitting display device using an organic light emitting device includes a top-emission method, a bottom-emission method, and a dual-emission method according to the direction in which light is emitted, and a driving method. It is divided into passive matrix type and active matrix type.

In the organic light emitting display device, when a scan signal, a data signal, and a power supply are supplied to a plurality of sub-pixels arranged in a matrix form, the selected sub-pixel emits light to display an image.

As a method of manufacturing a display panel of an organic light emitting display device, there are a deposition method, a solution method, and a hybrid method in which a deposition method and a solution method are combined. The hybrid method means that when forming the organic light emitting diode included in the sub-pixel of the display panel, a solution or solution method is used from the hole injection layer to the light emitting layer, and a deposition method is used from the light emitting layer to the electron injection layer.

A buffer layer is present at the interface of the organic light-emitting diode formed of a hybrid structure, which is highly mobile to deliver electrons to the red and green light-emitting layers and to smoothly inject holes into the blue light-emitting layer. It must have the ability of a bipolar material with mobility.

As such, the buffer layer should have good mobility for both electrons and holes, but if either mobility is insufficient, the charge balance is displaced and electron or hole pairs are formed in the buffer layer rather than the light emitting layer to improve color purity and efficiency. Will fall. Therefore, the buffer layer existing at the interface of the organic light-emitting diode formed of the hybrid structure causes a decrease in light efficiency when injection of electrons or holes is not desired, so a method for improving it is required.

The present invention for solving the above-mentioned problems of the background art provides an organic electroluminescence display device that improves the light efficiency of the red, green, and blue sub-pixels and simplifies the process by providing ease of a solveable process.

The present invention as a means for solving the above problems is a display panel; And red, green, and blue sub-pixels formed on the display panel, wherein the red, green, and blue sub-pixels are located between the lower electrode and the light emitting layer and each include a mixed layer having hole injection capability and hole transport capability. The mixed layer includes an organic electroluminescence display device characterized in that at least three different materials are mixed.

The mixed layer may be made of a hole injection material, a hole transport material, and a transition metal compound material.

The mixing ratio of the hole injection material, the hole transport material and the transition metal compound material may have a relationship between the hole injection material> the hole transport material> the transition metal compound material.

The hole injection material may account for 50 to 60 parts by weight, the hole transport material may occupy 10 to 40 parts by weight, and the transition metal compound may occupy 0.1 to 5 parts by weight with respect to 100 parts by weight of the total mixed layer.

The hole injection material, the hole transport material and the transition metal compound material may be mixed in a ratio of 60: 35: 5.

The transition metal compound material may be an oxide.

The mixed layer and the light emitting layer may be formed by a solution process.

The present invention uses a mixed layer of a hole injection material, a hole transport material and a transition metal compound to form a blue light emitting layer in the same layer as the red and green light emitting layers without forming a blue common layer (BCL) structure. There is an effect of providing an organic light emitting display device that can give ease. In addition, the present invention has an effect of providing an organic light emitting display device capable of simplifying the process by improving the light efficiency of the red, green, and blue sub-pixels using only a single mixed layer through a solution process.

1 is a block diagram schematically showing an organic light emitting display device according to a first embodiment of the present invention.
FIG. 2 is an exemplary view of the sub-pixel shown in FIG. 1.
3 is a view schematically showing a cross-section of the display panel shown in FIG. 1;
4 is a first exemplary view showing a part of FIG. 3 in detail;
5 is a second exemplary view showing a part of FIG. 3 in detail;
6 is a cross-sectional structure diagram of a sub-pixel for explaining a conventional hybrid scheme.
7 is a view showing some layers of an organic emission layer included in a subpixel according to an embodiment of the present invention.
8 is a characteristic graph for an experimental example in which a hole injection material and a hole transport material are mixed.
9 is a characteristic graph for an embodiment of the present invention in which a hole injection material, a hole transport material and a transition metal compound are mixed.
10 is a configuration diagram of a sub-pixel according to an embodiment of the present invention.
11 is a cross-sectional view of a sub-pixel according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, specific content for the practice of the present invention will be described.

1 is a block diagram schematically showing an organic light emitting display device according to an embodiment of the present invention, FIG. 2 is an exemplary view of a sub-pixel shown in FIG. 1, and FIG. 3 is a view of the display panel shown in FIG. 1. FIG. 4 is a first exemplary view showing a part of FIG. 3 in detail, FIG. 5 is a second exemplary view showing a part of FIG. 3 in detail, and FIG. 6 shows a hybrid scheme proposed in the related art. It is a cross-sectional structure diagram of a sub pixel for explanation.

As illustrated in FIG. 1, the organic light emitting display device according to an exemplary embodiment of the present invention includes a timing control unit 120, a scan driving unit 130, a data driving unit 140, and a display panel 150.

The timing control unit 120 collects device information (Extended Display Identification Data; EDID) including the resolution, frequency, and timing information of the display panel 150 from the external memory unit through an I2C interface or the like, or compensation data. The timing controller 120 outputs a gate timing control signal GDC for controlling the operation timing of the scan driver 130 and a data timing control signal DDC for controlling the operation timing of the data driver 140. The timing controller 120 supplies the data signal DATA with the data timing control signal DDC to the data driver 140.

The data driver 140 samples, latches, and converts and outputs the data signal DATA into a gamma reference voltage in response to the data timing control signal DDC supplied from the timing controller 120. The data driver 140 may be formed of an integrated circuit (IC) and mounted on the display panel 150 or an external substrate connected to the display panel 150. The data driver 140 supplies a data signal DATA to the sub pixels SP included in the display panel 150 through the data lines DL.

The scan driver 130 outputs a scan signal while shifting the level of the gate voltage in response to the gate timing control signal GDC supplied from the timing controller 120. The scan driver 130 may be formed of an integrated circuit and mounted on the display panel 150 or may be mounted on an external substrate connected to the display panel 150. Also, the scan driver 130 may be formed on the display panel 150 in the form of a gate in panel. The scan driver 130 supplies a scan signal to sub-pixels SP included in the display panel 150 through scan lines GL.

The display panel 150 displays an image in response to the scan signal supplied from the scan driver 130 and the data signal DATA supplied from the data driver 140. The display panel 150 includes sub-pixels SP controlling light to display an image. The display panel 150 is implemented in a top-emission method, a bottom-emission method, or a dual-emission method according to the structure of the sub-pixels SP.

As shown in FIG. 2, one sub-pixel SP is supplied corresponding to the scan signal supplied through the switching transistor SW and the switching transistor SW connected to the scan line GL1 and the data line DL1. A pixel circuit PC operating in response to the data signal DATA is included.

The pixel circuit PC includes a driving transistor, a capacitor, and an organic light emitting diode. When a driving transistor, a capacitor, and an organic light-emitting diode are included in the pixel circuit PC, the sub-pixel SP has a 2T (Transistor) 1C (Capacitor) structure. However, when a compensation circuit for compensating a driving transistor, as well as a driving transistor, a capacitor, and an organic light emitting diode is added to the pixel circuit PC, it is composed of 3T1C, 4T1C, and 5T2C.

The sub pixels SP include a red sub pixel, a green sub pixel, and a blue sub pixel. However, the structure including white sub-pixels, red sub-pixels, green sub-pixels, and blue sub-pixels may be configured to increase luminance of the display panel 150 and prevent deterioration of luminance and color deterioration of pure colors. In this case, the white sub-pixel, the red sub-pixel, the green sub-pixel, and the blue sub-pixel are implemented by using a white organic light emitting diode and an RGB color filter, or the white, red, green, and blue light emitting materials included in the organic light emitting diode are used. It is implemented in a manner that is formed by dividing.

As shown in FIG. 3, the display panel 150 includes a lower substrate 151 and an upper substrate 152. The lower substrate 151 and the upper substrate 152 are bonded by an adhesive such as sealant. However, when the upper substrate 152 is formed in a film form, it is formed on the lower substrate 151 in the form of a deposition.

Sub-pixels including an organic light emitting diode and the like are formed on one surface of the lower substrate 151. Sub-pixels including organic light emitting diodes are vulnerable to external air such as oxygen and moisture. Accordingly, an upper substrate 152 capable of sealing sub-pixels is formed on the lower substrate 151.

A protective film 155 protecting the upper surface of the display panel 150 is formed on the upper substrate 152. The protective film 155 serves to prevent damage to the display panel 150 from external stimuli or impact that may be applied to the upper surface of the display panel 150, which may be omitted.

4 and 5, a switching transistor (not shown), a driving transistor DR, a capacitor (not shown), and an organic light emitting diode (OLED) are formed on one surface of the lower substrate 151. The switching transistor (not shown), the driving transistor DR, the capacitor (not shown), and the organic light emitting diode OLED are connected to various wirings formed on one surface of the lower substrate 151.

The driving transistor DR includes a gate electrode 161, a semiconductor layer 163, a source electrode 164a and a drain electrode 164b. The gate electrode 161 is formed on one surface of the lower substrate 151. The first insulating layer 162 is formed on the gate electrode 161. The semiconductor layer 163 is formed on the first insulating film 162. The source electrode 164a and the drain electrode 164b are formed to contact one side and the other side of the semiconductor layer 163. A second insulating film 165 is formed on the source electrode 164a and the drain electrode 164b.

The organic light emitting diode (OLED) includes a lower electrode 166, an organic emission layer 168, and an upper electrode 169. The lower electrode 166 is formed on the second insulating film 165. The lower electrode 166 is formed to be connected to the drain electrode 164b of the driving transistor DR exposed through the second insulating layer 165. The lower electrode 166 is formed separately for each sub-pixel. The lower electrode 166 is selected as the anode electrode (or cathode electrode). The bank layer 167 is formed on the lower electrode 166. The bank layer 167 is a layer that defines the opening area of the sub-pixel. The organic emission layer 168 is formed on the lower electrode 166.

The organic emission layer 168 includes a hole injection layer (HIL), a hole transport layer (HTL), a light emitting layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL). However, at least one of the functional layers HIL, HTL, ETL, and EIL other than the emission layer EML of the organic emission layer 168 may be omitted. The upper electrode 169 is formed on the organic emission layer 168. The upper electrode 169 is formed in the form of a face electrode commonly connected to all sub-pixels. The upper electrode 169 is selected as a cathode electrode (or anode electrode).

4, the upper substrate 152 may be formed in a multi-layer film form or a single film form, although not shown. When the upper substrate 152 is formed in the form of a multilayer film, it may be formed of an organic film and an inorganic film, and when the upper substrate 152 is formed in a single-layer film form, it may be formed of an organic film or an inorganic film.

As illustrated in FIG. 5, the upper substrate 152 may be formed in an N (N is an integer of 3 or more) layer film. In this case, the upper substrate 152 may be formed of an organic / inorganic composite layer composed of an organic layer 152a, an inorganic layer 152b, an organic layer 152c, and an inorganic layer 152d. Although not shown, the inside of the organic-inorganic composite layer may further include a moisture absorbing layer that absorbs moisture or oxygen.

On the other hand, the organic light emitting diode included in the sub-pixel of the display panel is formed in a hybrid method, and the problems of the conventional hybrid method will be described below.

As shown in FIG. 6, the conventional hybrid method uses a solution or solution process from the hole injection layer 168_HIL to the red and green light emitting layers 168R and 168G, and the buffer layer 168BUF) and blue color. From the light emitting layer 168B to the upper electrode 169, an evaporation process is used.

A buffer layer 168_BUF exists at an interface of an organic light emitting diode formed of a conventional hybrid structure, which transfers electrons to the red and green light emitting layers 168R and 168G, and a blue light emitting layer 168B. It must have the ability of a bipolar material with high mobility to allow smooth injection of holes.

As such, the buffer layer 168_BUF should have good mobility for both electrons and holes, but if either mobility is insufficient, the charge balance is displaced and the electron or hole pair has a light emitting layer (168R, 168G, 168B). Instead, it is formed on the buffer layer 168_BUF, thereby reducing color purity and light efficiency.

As a result of the experiment using the conventional hybrid structure shown in FIG. 6, a color interference phenomenon in which blue peaks occur in the spectrum for red and green was observed. The color interference phenomenon in which red and green peaks occur is because the buffer layers 168_BUF do not smoothly transfer electrons to the red and green emission layers 168R and 168G.

On the other hand, when the buffer layer 168_BUF interposed in the conventional hybrid structure is not used, the problem of color interference between red and green and blue can be reduced. However, in the case of the blue light emitting layer 168B, when the buffer layer 168_BUF is not used, a recombination region of electrons and holes is formed at an interface between the soluble layer and the deposition layer, thereby reducing the efficiency and lifetime of the device.

7 is a view showing some layers of an organic light emitting layer included in a sub-pixel according to an embodiment of the present invention, FIG. 8 is a characteristic graph for an experimental example in which a hole injection material and a hole transport material are mixed, and FIG. 9 It is a characteristic graph for an embodiment of the present invention in which a hole injection material, a hole transport material and a transition metal compound are mixed.

As shown in FIG. 7, an embodiment of the present invention is a mixture of at least three different materials between the lower electrode 166 and the red, green and blue light emitting layers 168RGB to overcome and overcome the above-described problems. A mixed layer 168_MIX is formed.

The mixed layer 168_MIX is made of a hole injection material, a hole transport material, and a transition metal compound material. The mixed layer 168_MIX in which the hole injection material, the hole transport material, and the transition metal compound is mixed can serve as the hole injection layer and the hole transport layer, thereby simplifying the process while improving the characteristics of the device. That is, the mixed layer 168_MIX has hole injection capability and hole transport capability.

In addition, it has been found that a previously proposed buffer layer can be deleted (or omitted) by configuring the mixed layer 168_MIX in which a hole injection material, a hole transport material, and a transition metal compound are mixed to have the above characteristics. It is explained by the experimental results.

As shown in FIG. 8, the voltage current (VJ plot), luminance and brightness (Lum. Vs cd) for the comparative examples (Ref.) And the experimental examples (HIL + HTL) in which the hole injection material and the hole transport material were mixed. / A) and Spectrum graphs are shown.

The comparative example (Ref.) Corresponds to the sub-pixel described with reference to FIG. 6. Experimental examples (HIL + HTL) are the first experimental example (HIL + HTL (10%), hole transporting material mixed with 20% of the hole transporting material for the hole injection material 10% Experimental Example (HIL + HTL (20%), hole transporting material 30% mixed with hole transporting material 3 Experimental Example (HIL + HTL (30%), hole transporting material transporting 40% mixed hole transporting material It is divided into the fourth experimental example (HIL + HTL (40%)).

As can be seen from the experimental examples (HIL + HTL), while increasing the mixing ratio of the hole transport material to the hole injection material to 10-40%, their properties were observed in comparison with the comparative example (Ref.).

As can be seen from the experimental examples (HIL + HTL), when the hole injection material and the hole transport material are mixed, it can be seen that the light efficiency decreases while the driving voltage increases compared to the comparative example (Ref.). In addition, even if the proportion of the hole injection material was increased, the injection rate of the hole did not increase much. As a result, it was found that it is difficult to greatly improve the performance of the device by mixing only the hole injection material and the hole transport material.

However, it was confirmed that the hole injection layer and the hole transport layer can serve as a hole injection layer and a single mixed layer in which the hole injection material and the hole transport material are mixed. We can infer that we can be satisfied.

As shown in Figure 9, an embodiment of the present invention is a method of mixing a hole injection material, a hole transport material and a transition metal compound to form a single mixed layer, an experiment of mixing a hole injection material and a hole transport material The defects occurring in the mixed layer of the examples (HIL + HTL) were improved.

As can be seen from the voltage current (VJ plot) graph of FIG. 9, the driving voltage slightly increased compared to the comparative example (Ref.) As the mixed layer (HIL + HTL + α) according to an embodiment of the present invention was applied. It was found to be lower than the examples (HIL + HTL).

As can be seen from the luminance and brightness (Lum. Vs. cd / A) graph of FIG. 9, as compared to the experimental examples (HIL + HTL) as the mixed layer (HIL + HTL + α) according to an embodiment of the present invention is applied The luminance and brightness were improved to a fairly high level, and it was found that the luminance and brightness of the comparative example (Ref.) Were almost similar.

As can be seen through the spectrum (Spectrum) graph of Figure 9, as compared to the comparative example (Ref.) Or experimental examples (HIL + HTL) as a mixed layer (HIL + HTL + α) according to an embodiment of the present invention applied It was shown that the spectrum showed almost the same level without any problems.

In one embodiment of the present invention, based on the previous experimental examples, a transition metal compound material corresponding to a powder type oxide was added. As a result, as can be seen through the graph of FIG. 9, the mixed layer (HIL + HTL + α) constructed according to an embodiment of the present invention exhibited superior performance compared to the experimental examples (HIL + HTL).

If it is described in relation to the mixing ratio between the hole injection material, hole transport material and the transition metal compound used in the Examples.

8 and 9, the basic material of the mixed layer (HIL + HTL + α) corresponds to the hole injection material, and the hole transport material and the transition metal compound material correspond to the additive material. Therefore, when the mixing ratio between the hole injection material, the hole transport material and the transition metal compound is described in a relational expression, it is expressed as hole injection material> hole transport material> transition metal compound.

Since the hole injection material corresponds to the basic material of the mixed layer (HIL + HTL + α), it must be accounted for more weight than the sum of the hole transport material and the transition metal compound, so that hole injection can be smoothly performed. If the proportion of the hole injection material is too small or too large, the injection capacity of the hole may be reduced, and the proportion of other additives may be reduced, thereby reducing the transport capacity of the hole. Therefore, it is preferable that the hole injection material accounts for 50 to 60 parts by weight based on 100 parts by weight of the mixed layer.

As can be seen through Figures 8 and 9, the hole transport material showed a tendency to increase the voltage when the ratio is increased compared to the hole injection material and the hole is not injected well. However, as the transition metal compound was added, this tendency was not observed, but gradually decreased in the driving voltage direction similar to that of the comparative example. However, as the ratio of the hole transport material increases, the light efficiency greatly decreases, so the mixing ratio of the transition metal compound material should be considered. Therefore, it is preferable that the hole transport material occupies 10 to 40 parts by weight based on 100 parts by weight of the mixed layer.

As can be seen through Figures 8 and 9, the transition metal compound material serves to lower the driving voltage by improving the hole injection ability to compensate and improve defects caused by the mixing of the hole injection material and the hole transport material. The transition metal compound is only included in a trace amount since the mixed layer needs to be modified in a form that can improve the hole injection ability. When the transition metal compound is mixed at a high ratio, the mixed layer can be modified with only one function without simultaneously serving as the hole injection and hole transport layer. Therefore, the transition metal compound material preferably accounts for 0.1 to 5 parts by weight based on 100 parts by weight of the mixed layer.

Meanwhile, the mixed layer (HIL + HTL + α) according to the embodiment of FIG. 9 is an experiment result when a hole injection material, a hole transport material, and a transition metal compound are formed in a ratio of 60: 35: 5. Therefore, the characteristics of the mixed layer (HIL + HTL + α) are not limited thereto, and it is apparent that mixing with a ratio as described above may exhibit different characteristics from FIG. 9. Therefore, the characteristics of the sub-pixel to which the mixed layer (HIL + HTL + α) according to an embodiment of the present invention is applied are not limited thereto.

On the other hand, the hole transport material used in the experimental examples and examples of FIGS. 8 and 9 are the hole transport material A (HTL A), the hole transport material B (HTL B) and the hole transport C described in Table 1 below. It is selected as one of the substances (HTL C).

In Table 1 "HOMO / LUMO" is the homo rumo level, "T1" is triplet level, "Tg" is the glass transition temperature, "μ _h" is the hole mobility, "Morphology" refers to the morphology.

Hereinafter, a sub-pixel including a mixed layer (HIL + HTL + α) according to an embodiment of the present invention will be described.

10 is a configuration diagram of a sub-pixel according to an embodiment of the present invention, and FIG. 11 is a cross-sectional view of a sub-pixel according to an embodiment of the present invention.

As illustrated in FIG. 10, a sub-pixel according to an embodiment of the present invention includes a lower electrode 166, an organic emission layer 168, and an upper electrode 169. The lower electrode 166 is selected as the anode electrode, and the upper electrode 169 is selected as the cathode electrode.

The organic emission layer 168 includes a mixed layer 168_MIX, red, green, and blue emission layers 168RGB and an electron transport layer 168_ETL. The mixed layer 168_MIX is composed of a layer in which a hole injection material, a hole transport material, and a transition metal compound material are mixed, as revealed in the experiment example described above.

11, the mixed layer 168_MIX is formed on the lower electrode 166, and the red, green, and blue emission layers 168RGB are formed on the mixed layer 168_MIX. The electron transport layer 168_ETL is formed on the red, green, and blue emission layers 168RGB. The electron injection layer and the upper electrode 169 are formed on the electron transport layer 168_ETL.

The mixed layer 168_MIX and the red, green, and blue emission layers 168RGB are formed in a solution or solution method, and the electron transport layer 168_ETL, the electron injection layer, and the upper electrode 169 are evaporation processes. Is formed by. The solution or solution process includes inkjet printing, nozzle printing, transfer, slit coating, gravure printing and thermal jet printing as a solution process.

As described above, the present invention does not form a blue light emitting layer in a blue common layer (BCL) structure by using a mixed layer in which a hole injection material, a hole transport material, and a transition metal compound are mixed. There is an effect of providing an organic light emitting display device that can give ease of use. In addition, the present invention has an effect of providing an organic light emitting display device capable of simplifying the process by improving the light efficiency of the red, green, and blue sub-pixels using only a single mixed layer through a solution process.

The embodiments of the present invention have been described above with reference to the accompanying drawings, but the technical configuration of the present invention described above is in other specific forms without changing the technical spirit or essential features of the present invention by those skilled in the art to which the present invention pertains. It will be understood that it can be practiced. Therefore, the embodiments described above are to be understood in all respects as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the claims below, rather than the detailed description. In addition, all modifications or variations derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

120: timing control unit 130: scan driver
140: data driving unit 150: display panel
166: lower electrode 168: organic light emitting layer
168_MIX: mixed layer 168R, 168G, 168B: emitting layer
168_ETL: electron transport layer 169: upper electrode

Claims (8)

Display panel; And
Red, green, and blue sub-pixels formed on the display panel,
The red, green and blue sub-pixels
Located between the lower electrode and the light emitting layer and includes a mixed layer each having a hole injection ability and hole transport ability,
The mixed layer is a hole injection material, hole transport material and a transition metal compound is mixed,
For the total 100 parts by weight of the mixed layer
The hole injection material occupies 50 to 60 parts by weight,
The hole transport material occupies 10 to 40 parts by weight,
The transition metal compound is an organic electroluminescent display device, characterized in that occupies 0.1 to 5 parts by weight. delete delete delete According to claim 1,
The hole injection material, the hole transport material and the transition metal compound material
60: 35: 5 organic light emitting display device, characterized in that mixed in a ratio. According to claim 1,
The transition metal compound is an organic electroluminescent display device, characterized in that the oxide. According to claim 1,
The mixed layer and the light emitting layer
An organic electroluminescent display device, characterized in that formed by the solution process. According to claim 1,
The mixed layer and the light emitting layer are formed by a solution process,
An organic electroluminescent display device formed by an electron injection layer on the light emitting layer and an upper electrode on the electron injection layer by a deposition process.

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