Patent Application
20230172035
The present disclosure relates to display devices.
Much attention has been paid to, for example, OLED (organic light-emitting diode) display devices and QLED (quantum-dot light-emitting diode) display devices (see, e.g., Patent Literature 1 listed below).
Patent Literature 1: PCT International Application Publication No. WO2018/179168 A1 (Publication Date: Oct. 4, 2018)
Patent Literature 1 describes a display device including a sealing layer in which a first inorganic sealing film, an organic sealing film, and a second inorganic sealing film, among others, are provided in this order on a light-emitting element layer. However, this sealing layer could in some cases exhibit poor adhesion between the organic sealing film and the first inorganic sealing film and between the organic sealing film and the second inorganic sealing film, so that an undesirable gap may develop between the organic sealing film and the first inorganic sealing film and between the organic sealing film and the second inorganic sealing film. It is therefore difficult to improve barrier properties in the conventional display device, which can pose an issue.
The present disclosure, in an aspect thereof, has been made in view of this issue and has an object to provide a display device with good barrier properties.
To address the issue, the present disclosure is directed to a display device including: a display area including a plurality of pixels; a frame area surrounding the display area; a thin film transistor layer; a light-emitting element layer on the thin film transistor layer in the display area, the light-emitting element layer including a plurality of light-emitting elements that each include a first electrode, a light-emitting layer, and a second electrode and that emit light of different colors; and a sealing layer disposed on the light-emitting element layer to seal the light-emitting element layer, wherein the sealing layer includes a first inorganic sealing film on the light-emitting element layer and an organic sealing film on the first inorganic sealing film, and the organic sealing film contains a polymer compound and a cyclic compound.
The present disclosure, in an aspect thereof, can provide a display device with good barrier properties.
Portion (a) of
The following will describe embodiments of the present invention with reference to
Portion (a) of
As shown in (a) of
As shown in (b) of
The present embodiment describes an example where each pixel P in the display device 1 includes a red subpixel RSUB, a green subpixel GSUB, and a blue subpixel BSUB, the red subpixel RSUB includes one of the red light-emitting elements 11R, the green subpixel GSUB includes one of the green light-emitting elements 11G, and the blue subpixel BSUB includes one of the blue light-emitting elements 11B. This is however not the only possible implementation of the invention. Alternatively, each pixel P in the display device 1 may include a subpixel of another color.
There is provided a light-emitting element layer 11 on the TFT layer 6 in the display area DA. The light-emitting element layer 11 includes: first electrodes 7; functional layers 9R, 9G, 9B each including a light-emitting layer; and a second electrode 10, and is a layer in which the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B, which emit different colors of light, are formed.
The substrate 4 and the lower substrate 17 are flexible substrates composed primarily of, for example, a resin such as a polyimide.
The barrier layer 5 is an inorganic insulation layer for preventing the intrusion of foreign materials such as water and oxygen and may be made of, for example, silicon nitride or silicon oxide.
The TFT layer 6 includes, among others: a plurality of thin film transistors; a plurality of capacitive elements; wiring lines for these transistors and elements; and various insulation films.
The red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B on the TFT layer 6 each include: one of the first electrodes 7 provided in an insular manner; the common, second electrode 10; and the functional layers 9R, 9G, 9B between the first electrode 7 and the second electrode 10. Note that the edge cover 8 is an insulation film for covering the edge of the first electrode 7.
The functional layer 9R in each red light-emitting element 11R includes a red light-emitting layer, the functional layer 9G in each green light-emitting element 11G includes a green light-emitting layer, and the functional layer 9B in each blue light-emitting element 11B includes a blue light-emitting layer.
The first electrodes 7 are anodes, and the second electrode 10 is a cathode, in the present embodiment. Therefore, the functional layer 9R, provided between the first electrode 7 and the second electrode 10 in each red light-emitting element 11R, includes a hole injection layer, a hole transport layer, a red light-emitting layer, an electron transport layer, and an electron injection layer, all of which are stacked in this order when viewed from the first electrode 7 side. In addition, the functional layer 9G, provided between the first electrode 7 and the second electrode 10 in each green light-emitting element 11G, includes a hole injection layer, a hole transport layer, a green light-emitting layer, an electron transport layer, and an electron injection layer, all of which are stacked in this order when viewed from the first electrode 7 side. Additionally, the functional layer 9B, provided between the first electrode 7 and the second electrode 10 in each blue light-emitting element 11B, includes a hole injection layer, a hole transport layer, a blue light-emitting layer, an electron transport layer, and an electron injection layer, all of which are stacked in this order when viewed from the first electrode 7 side. The functional layers 9R, 9G, 9B structured as described here are used in the present embodiment. This is however not the only possible implementation of the invention.
In the present embodiment, since the first electrodes 7 are anodes, the first electrodes 7 may be made of, for example, a stack of ITO (indium tin oxide) and Ag (silver), so as to be reflective to visible light.
In the present embodiment, since the second electrode 10 is a cathode, the second electrode 10 may be made of, for example, a thin metal film of, for example, a magnesium-silver alloy, so as to be transmissive to visible light. The present embodiment describes an example where the second electrode 10 is a common electrode. This is however not the only possible implementation of the invention. Alternatively, the second electrode 10 may be provided in an insular manner, and the first electrode be provided as a common electrode.
The edge cover 8 is formed by, for example, applying an organic material such as a polyimide or an acrylic resin and subsequently patterning the applied organic material by photolithography.
The present embodiment describes an example where the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B are all OLEDs (organic light-emitting diodes). This is however not the only possible implementation of the invention. Alternatively, the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B may be all QLEDs (quantum-dot light-emitting diodes) each including a quantum-dot layer as a light-emitting layer. Additionally, some of the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B may be OLEDs, and the rest of the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B may be QLEDs.
The sealing layer 12 for covering the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B, that is, the sealing layer 12 provided on the light-emitting element layer 11 to seal the light-emitting element layer 11, prevents foreign materials such as water and oxygen from reaching inside the light-emitting elements of the associated color. Details will be given later.
The resin layer 13 may be made of an organic material such as a polyimide or an acrylic resin so as to cover the barrier layer 5 and the sealing layer 12.
The present embodiment describes an example where the sealing layer 12 covering the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B is a film including a first inorganic sealing film 12a, an organic sealing film 12b, and a second inorganic sealing film 12c, all of which are stacked in this order when viewed from the side of the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B, as shown in
The present embodiment describes an example where the first inorganic sealing film 12a and the second inorganic sealing film 12c shown in
The organic sealing film 12b shown in
In the present embodiment, the polymer compound is a methacrylic-based polymer (m=1 in chemical formula 3 below), and the cyclic compound is a cyclodextrin (chemical formula 2 below). The methacrylic-based polymer and the cyclodextrin therefore form an inclusion complex (chemical formula 1 below) of the methacrylic-based polymer and the cyclodextrin. Note that n is an integer greater than or equal to 1 in chemical formulas 1, 2, and 3 below and also that m is an integer greater than or equal to 1 in chemical formula 3 below.
In the present embodiment, a 1:1 (weight ratio) mixed solution of the cyclodextrin (chemical formula 2) and the methacrylic-based polymer (m=1 in chemical formula 3 above) in a mixed solvent of ethanol and THF is applied onto the first inorganic sealing film 12a, and the entire mixture is heated at 80° C. for 20 minutes to remove the solvent, to prepare the organic sealing film 12b with a 2-μm thickness.
The cyclodextrin (chemical formula 2) is more polar than the methacrylic-based polymer (chemical formula 3) and has good affinity with the first inorganic sealing film 12a or the second inorganic sealing film 12c (particularly with a silicon nitride film). In addition, the cyclodextrin (chemical formula 2) is not particularly very soluble in water and is for this reason capable of efficiently restraining permeability to moisture and organic impurities when used in combination with the methacrylic-based polymer (chemical formula 3).
The organic sealing film 12b has good affinity with the first inorganic sealing film 12a, thereby leaving no space between the first inorganic sealing film 12a and the organic sealing film 12b. The organic sealing film 12b therefore does not need to have an increased thickness. The thickness of the organic sealing film 12b is preferably from 0.2 μm to 2.3 μm, both inclusive, and more preferably from 0.2 μm to 2.0 μm, both inclusive.
The organic sealing film 12b is preferably formed to a thickness of at least 0.2 μm because otherwise there may exist no organic molecules, in other words, there may develop a region where there is no organic sealing film, which could reduce the water-barrier property, if the organic sealing film 12b is formed by applying a liquid.
The organic sealing film 12b is preferably formed to a thickness of at most 2.3 μm because light may leak in an oblique direction and/or color may change if the organic sealing film is excessively thick.
Note that in view of ease in forming the inclusion complex (chemical formula 1 above) of a methacrylic-based polymer and a cyclodextrin, it is preferable to select a cyclodextrin that has such an n that the cyclodextrin (chemical formula 2 above) has an inner diameter of at least 0.45 nm. Note that the present embodiment uses a cyclodextrin with an inner diameter of 0.45 nm.
The sealing layer 12 in the display device 1 in accordance with the present embodiment includes a stacked film in which the first inorganic sealing film 12a and the organic sealing film 12b are stacked in this order when viewed from the side of the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B. Specifically, since the sealing layer 12 is a film in which the first inorganic sealing film 12a, the organic sealing film 12b, and the second inorganic sealing film 12c are stacked in this order when viewed from the side of the red light-emitting elements 11R, the green light-emitting elements 11G, and the blue light-emitting elements 11B, the resultant display device 1 achieves zero retardation and both good barrier properties and good display performance. In other words, in the present embodiment, adherence can be improved both between the organic sealing film 12b and the first inorganic sealing film 12a and between the organic sealing film 12b and the second inorganic sealing film 12c, and a gap may be prevented from developing between these films. Therefore, erosion by, for example, water content and foreign materials can be prevented without having to increase the thickness of the organic sealing film 12b. Consequently, the occurrence of retardation due to an increase in the thickness of the organic sealing film 12b can be prevented, and the resultant display device 1 exhibits excellent viewing angle characteristics, in other words, excellent display performance.
Each sealing layer including a cyclodextrin listed in
Meanwhile, each sealing layer including no cyclodextrin listed in
Note that all evaluations were performed without providing the resin layer 13, the adhesion layer 16, and the lower substrate 17 shown in
In addition, the evaluations of driving lifespan of the blue light-emitting elements 11B and the red light-emitting elements 11R are results of a 50 mA/cm #<2># current driving test performed in an environment where the temperature was 45° C. and the humidity was 90%. The evaluations of driving lifespan of the green light-emitting elements 11G are results of a 30 mA/cm #<2># current driving test in the same environment.
Referring to
Referring to
Referring to
For the methacrylic-based polymer of chemical formula 3 above contained in the organic sealing film 12b, m in chemical formula 3 above is preferably an integer from 1 to 12, more preferably an integer from 1 to 8, and most preferably an integer from 1 to 3.
The present embodiment has so far discussed an example where the organic sealing film 12b contains a cyclodextrin as a cyclic compound. This is however not the only possible implementation of the invention. Alternatively, for example, a crown ether or a cycloawaodorin may be used so long as the substance is more polar than the polymer compound contained in the organic sealing film 12b and has good affinity to the first inorganic sealing film 12a or the second inorganic sealing film 12c. Note that the crown ether or the cycloawaodorin preferably has such an inner diameter as to readily form an inclusion complex with a polymer compound. Additionally, at least one species selected from a cyclodextrin, a crown ether, and a cycloawaodorin may be used as the cyclic compound contained in the organic sealing film 12b.
In addition, the present embodiment has so far discussed an example where the organic sealing film 12b contains a methacrylic-based polymer of chemical formula 3 above as a polymer compound. This is however not the only possible implementation of the invention. Alternatively, at least one species selected from a methacrylic-based polymer, an acrylic-based polymer, a polyimide, a parylene, a polyester, a polyamide, and a polyaramide may be used as the polymer compound contained in the organic sealing film 12b.
In addition, the present embodiment describes an example where the first inorganic sealing film 12a and the second inorganic sealing film 12c are silicon nitride (SiNx) films. This is however not the only possible implementation of the invention. Alternatively, a film containing at least one of silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy where x>y), and silicon nitroxide (SiNxOy where x>y) may be used as the first inorganic sealing film 12a or the second inorganic sealing film 12c.
In addition, the present embodiment has so far discussed an example of results in cases where a silicon nitride (SiNx) film is used as the first inorganic sealing film 12a and the second inorganic sealing film 12c. The same results as the above-described results are obtained even if a film is used in which a single-layered inorganic insulation film of, for example, silicon oxide (SiOx), silicon oxynitride (SiOxNy where x>y), or silicon nitroxide (SiNxOy where x>y) is formed and even if a film is used in which inorganic insulation films of, for example, silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy where x>y), or silicon nitroxide (SiNxOy where x>y) are stacked.
A description is now given of Embodiment 2 of the present invention with reference to
The sealing layer 12′ in the display device in accordance with the present embodiment shown in
Each sealing layer 12′ including a cyclodextrin listed in
Meanwhile, each sealing layer including no cyclodextrin listed in
Note that all evaluations were performed without providing the resin layer 13, the adhesion layer 16, and the lower substrate 17 shown in
In addition, the evaluations of driving lifespan are results of a 50 mA/cm #<2># current driving test performed in an environment where the temperature was 45° C. and the humidity was 90%.
Referring to
From the description so far, the weight ratio of the cyclic compound to the polymer compound in the organic sealing film 12b′ in the sealing layer 12′ in the display device in accordance with the present embodiment is preferably 0.25:1 or greater.
Since the display device in accordance with the present embodiment includes the sealing layer 12′, the display device can prevent the occurrence of retardation and achieve both good barrier properties and good display performance similarly to Embodiment 1.
A description is now given of Embodiment 3 of the present invention with reference to
In the sealing layer 12″ in the display device in accordance with the present embodiment shown in
Each sealing layer 12″ including a cyclodextrin listed in
Note that all evaluations were performed without providing the resin layer 13, the adhesion layer 16, and the lower substrate 17 shown in
In addition, the evaluations of driving lifespan are results of a 50 mA/cm #<2># current driving test performed in an environment where the temperature was 45° C. and the humidity was 90%.
Referring to
For the acrylic-based polymer of chemical formula 4 above contained in the organic sealing film 12b″, m in chemical formula 4 above is preferably an integer from 1 to 12, more preferably an integer from 1 to 8, and most preferably an integer from 1 to 3.
Since the display device in accordance with the present embodiment includes the sealing layer 12″, the display device can prevent the occurrence of retardation and achieve both good barrier properties and good display performance similarly to Embodiment 1.
Note that the lifespan was shorter when the acrylic-based polymer of chemical formula 4 above was used as the polymer compound in the organic sealing film of the sealing layer than when the methacrylic-based polymer of chemical formula 3 above was used as the polymer compound. This is presumably because the acrylic-based polymer has higher moisture permeability than the methacrylic-based polymer.
A display device including:
a display area including a plurality of pixels;
a frame area surrounding the display area;
a thin film transistor layer;
a light-emitting element layer on the thin film transistor layer in the display area, the light-emitting element layer including a plurality of light-emitting elements that each include a first electrode, a light-emitting layer, and a second electrode and that emit light of different colors: and
a sealing layer disposed on the light-emitting element layer to seal the light-emitting element layer, wherein
the sealing layer includes a first inorganic sealing film on the light-emitting element layer and an organic sealing film on the first inorganic sealing film, and
the organic sealing film contains a polymer compound and a cyclic compound.
The display device of aspect 1, wherein the sealing layer further includes a second inorganic sealing film on the organic sealing film.
The display device of aspect 1 or 2, wherein the first inorganic sealing film contains at least one of silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy where x>y), and silicon nitroxide (SiNxOy where x>y).
The display device of aspect 2, wherein the second inorganic sealing film contains at least one of silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy where x>y), and silicon nitroxide (SiNxOy where x>y).
The display device of any one of aspects 1 to 4, wherein the organic sealing film contains an inclusion complex of the polymer compound and the cyclic compound.
The display device of any one of aspects 1 to 5, wherein the cyclic compound is at least one species selected from a cyclodextrin, a crown ether, and a cycloawaodorin.
The display device of any one of aspects 1 to 6, wherein the polymer compound is at least one species selected from a methacrylic-based polymer, an acrylic-based polymer, a polyimide, a parylene, a polyester, a polyamide, and a polyaramide.
The display device of any one of aspects 1 to 6, wherein the polymer compound is a methacrylic-based polymer of chemical formula 3 where m is an integer from 1 to 12 and n is an integer greater than or equal to 1.
The display device of aspect 8, wherein in chemical formula 3, m is an integer from 1 to 8.
The display device of aspect 9, wherein in chemical formula 3, m is an integer from 1 to 3.
The display device of any one of aspects 1 to 6, wherein the polymer compound is an acrylic-based polymer of chemical formula 4 where m is an integer from 1 to 12 and n is an integer greater than or equal to 1.
The display device of aspect 11, wherein in chemical formula 4, m is an integer from 1 to 8.
The display device of aspect 12, wherein in chemical formula 4, m is an integer from 1 to 3.
The display device of any one of aspects 1 to 13, wherein the first inorganic sealing film has a thickness of from 0.4 μm to 0.6 μm, both inclusive.
The display device of any one of aspects 3 to 14, wherein
the sealing layer further includes a second inorganic sealing film on the organic sealing film, and
the second inorganic sealing film has a thickness of from 0.4 μm to 0.6 μm, both inclusive.
The display device of any one of aspects 1 to 15, wherein the organic sealing film has a thickness of from 0.2 μm to 2.3 μm, both inclusive.
The display device of any one of aspects 1 to 15, wherein the cyclic compound and the polymer compound in the organic sealing film have a weight ratio of 0.25:1 or greater.
The display device of any one of aspects 1 to 17, wherein the plurality of light-emitting elements are organic light-emitting diodes or quantum-dot light-emitting diodes.
The present invention is not limited to the description of the embodiments above and may be altered within the scope of the claims. Embodiments based on a proper combination of technical means disclosed in different embodiments are encompassed in the technical scope of the present invention. Furthermore, new technological features can be created by combining different technical means disclosed in the embodiments.
The present invention is applicable to display devices.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/019598 | 5/18/2020 | WO |
