JP2023518514A - Display element and display device - Google Patents

Abstract

A display element is provided in which a black PDL and an optical film are combined to reduce the surface reflectance and reduce the dimming of the OLED output. In a display element in which an organic light emitting diode (OLED) in which an anode, an organic light emitting layer and a cathode are laminated on a substrate is integrated, a partition wall (PDL) made of a black material surrounding the organic light emitting diode, the organic light emitting diode and the and an optical film covering the partition wall.

Description

TECHNICAL FIELD The present disclosure relates to a display element, and more particularly to a display element having an organic light-emitting layer and arranged in a matrix to constitute a display device.

In a display device including a plurality of pixels, which is a display element having an organic light emitting diode (OLED), a polarizer is attached in order to obtain high contrast. Thus, the polarizers dim about 60% of the OLED output, resulting in higher power consumption of the display element for a given amount of light. Increased power consumption shortens the life of OLEDs.

Polyimide substrates used in top-emission OLEDs have a surface reflectance of about 10% or more. is about 90% or more. Therefore, an OLED display element without a polarizing plate has a high reflectance, and the visibility is significantly reduced especially under sunlight.

In order to deal with such problems, a light-shielding film is provided in contact with the anode electrode, or a light-shielding film is used in a partition wall (PDL: pixel defining layer) that defines the OLED (see, for example, Patent Document 1). -3). When the aperture ratio of the RGB OLEDs is 40%, the surface reflectance of the polyimide substrate is 10%, and the reflectance of the anode electrode is 90%, the average surface reflectance is calculated to be about 45%. By providing the light-shielding film, the surface reflectance of the polyimide substrate is reduced by about 5% or more, the average surface reflectance is about 35%, and it can be confirmed that the average surface reflectance is improved by about 10%. However, the reflectance is still high for a practical display element, and a polarizing plate is actually required.

Bendable or foldable display elements are now becoming more and more popular. However, a polarizing plate is required to lower the reflectance. A polarizing plate is generally hard and easily broken when bent, and the alignment state of liquid crystal molecules is affected by bending, so it cannot be applied to a bendable display device.

JP 2002-033185 A JP 2011-034884 A JP 2015-008036 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a display element in which a black PDL and an optical film are combined to reduce the surface reflectance and suppress the dimming of the OLED output.

In order to achieve the object of this disclosure, one embodiment of the present disclosure provides a display element in which an organic light emitting diode (OLED) in which an anode, an organic light emitting layer and a cathode are fabricated on a substrate is integrated, A partition made of a black material surrounding the organic light emitting diode and an optical film covering the organic light emitting diode and the partition are provided.

According to the present embodiment, by combining the black barrier ribs and the optical film having the degree of polarization within a predetermined range, the average surface reflectance of the OLED display element can be reduced, and the effect of improving the EQE can be expected. Dimming of the output can be suppressed.

The barrier ribs preferably have a surface resistivity of 10 ¹⁴ Ω/cm ² or more and a volume resistivity of 10 ¹⁴ Ω/cm or more.

According to this form, leakage current can be suppressed, and surface reflection can be suppressed with high optical density.

It is preferable that the partition walls have an optical density of 1.0 or more.

According to this form, leakage light to adjacent OLEDs can be reduced.

The optical film may be a polarizing film with a degree of polarization of 60-90%.

According to this embodiment, the surface reflectance of 12.5% or less and the EQE improvement rate of 10% or more, which are requirements for application to an OLED display device, can be satisfied.

The optical film can be an ND filter with an optical density of 0.15-0.26.

According to this embodiment, the surface reflectance of 12.5% or less and the EQE improvement rate of 10% or more, which are requirements for application to an OLED display device, can be satisfied.

A portion of the substrate other than the partition wall (PDL) surrounding the organic light emitting diode is covered with the black material, and an opening is formed in a part of the covered portion.

According to this aspect, it is possible to provide an OLED with high transmittance and improved contrast due to the black PDL.

1 is a diagram showing the structure of an OLED according to an embodiment of the present disclosure; FIG. FIG. 2 is a diagram showing a pixel structure of a display element using OLED of this embodiment; 1 is a diagram showing the configuration of a conventional polyimide PDL; FIG. 4 is a diagram showing the configuration of a black PDL according to this embodiment; FIG. FIG. 4 is a diagram showing an example of the relationship between the optical density of PDL and the surface reflectance; It is a figure which shows the structure of the optical film applied to OLED of this embodiment. It is a figure which shows an example of the characteristic of the LPE film of this embodiment. FIG. 4 is a diagram showing an output spectrum of a display element using the OLED of this embodiment; FIG. 5 is a diagram showing the effect of improving the OLED output by the LPE film of the present embodiment with respect to the conventional polarizing plate. It is a figure which shows an example of the characteristic of the ND filter of this embodiment.

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

FIG. 1 shows the structure of an OLED according to one embodiment of the invention. FIG. 1 is a cross-sectional view in which the emission direction of the OLED 100 (the display surface of the OLED display element) is on the upper side of the drawing, and schematically shows the layer structure. The OLED 100 has a backside barrier 110, a substrate 121, a backplane 122, a frontplane 130, and a thin film encapsulant (TFE) 140 which are stacked in order.

The backside barrier 110 comprises a first inorganic barrier layer 111 such as silicon nitride (SiNx), silicon oxynitride (SiNxOy) or silicon oxide (SiOx), an organic barrier layer 112 of organic resin, and a second barrier layer 112 of SiNx or SiOx. Inorganic barrier layers 113 are laminated in order to prevent entry of O ₂ and H ₂ O from the opposite side of the emission direction, that is, from the rear side.

In a backplane 122 on substrate 121, a thin film transistor (TFT) drive circuit is embedded directly under each pixel in order to apply a voltage or current to the selected pixel to operate it individually. The backplane 122 is flattened by embedding the TFTs and wiring on the substrate 121 with resin.

The frontplane 130 includes an anode 131, a hole injection layer (HIL) 132, a hole transport layer (HTL) 133, an organic light emitting layer (EML) 134, a hole blocking layer (HBL) 135, and an electron transport layer (ETL). A light-emitting layer including 136 and a cathode 137 are stacked in order.

TFE 140 comprises a first inorganic barrier layer 141 of SiNx/SiOx about 0.5 μm-1 μm thick, an organic barrier layer 142 about 7.5 μm-15 μm thick, and a SiNx/SiOx about 0.5 μm-1 μm thick. A second inorganic barrier layer 143 of SiOx is deposited in sequence. In addition, the film thickness of each TFE 140 can be arbitrarily set according to suitable light extraction conditions in terms of optical design, together with the laminated structure of the underlying OLED. Since it is determined by , it is not uniquely determined. TFE 140 prevents O ₂ and H ₂ O from entering from the display surface of the OLED display element.

The OLED 100 is a top-emission device in which light generated when holes injected from the anode 131 and electrons injected from the cathode 137 are recombined in the organic light-emitting layer 134 is extracted from the cathode 137 side opposite to the substrate 121. type OLED.

The substrate 121 is a support on which a plurality of OLEDs 100 are arranged and formed, and for example, quartz, glass, metal foil, or resin film or sheet is used. When the substrate 121 is made of resin, its material includes polyesters such as polybutylene naphthalate (PBN), methacrylic resins such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN). ), polyimide, polyamide (PA), polycarbonate resin, or the like is used.

For the anode 131, for example, an electrode material having a large work function from the vacuum level can be used in order to efficiently inject holes into the light-emitting layer. Specifically, the electrode material is a single metal such as chromium (Cr), gold (Au), platinum (Pt), nickel (Ni), copper (Cu), tungsten (W) or silver (Ag) or Alloys can be used. In addition, the anode 131 consists of a metal film made of these single metals or alloys, indium tin oxide (ITO), indium zinc oxide (InZnO), an alloy of zinc oxide (ZnO) and aluminum (Al), or the like. It may have a sputtered or vapor deposited laminated structure with a transparent conductive film.

In particular, in the case of a top-emission display element, the anode 131 uses an electrode of the OLED 100 with high reflectance, thereby improving the light extraction efficiency to the outside due to the interference effect and the high reflectance effect. For example, the anode 131 has a structure in which a first layer having excellent light reflectivity and a second layer having light transmittance and a large work function provided thereon are sputtered or deposited. The first layer can use an alloy containing Al or Ag as a main component, and a material having a work function relatively smaller than that of Al, which is the main component with high reflectance, can be used as an auxiliary component. Lanthanide series elements can be used as such subcomponents. Although the work function of the lanthanide series elements is not large, the inclusion of these elements improves the stability of the anode 131 and satisfies the hole injection properties of the anode 131 . In addition to elements of the lanthanide series, elements such as silicon (Si) and copper (Cu) may be used as subcomponents.

The second layer can use Al alloy oxide, molybdenum (Mo) oxide, zirconium (Zr) oxide, Cr oxide, and tantalum (Ta) oxide. For example, if the second layer is an Al alloy oxide layer (including a natural oxide film) containing a lanthanoid element as an accessory component, the lanthanide element oxide has a high transmittance, so the second layer containing the lanthanoid element oxide has a high transmittance. The transmittance of the two layers becomes good. This maintains a high reflectance on the surface of the first layer. Also, the characteristics of the anode 131 are improved by using a transparent conductive layer such as ITO for the second layer. Since ITO has a large work function, the use of ITO in the first layer, i.e., the side in contact with the substrate 121 can improve the carrier injection efficiency and the adhesion between the anode 131 and the substrate 121 .

In addition, when the driving method of the display element configured using the OLED 100 is the active matrix method, after forming the anode 131, the pixel portion is patterned with a pixel definition layer (PDL), and the driving method provided on the substrate 121 is formed. The anode 131 is connected to the TFT for use.

HIL 132, HTL 133, EML 134, HBL 135, and ETL 136 included in the emissive layer are organic layers. These organic layers are composed of an acrylic compound and hexamethyldisiloxane (HMDSO) as well as materials described later. The organic layer is formed, for example, by an inkjet printer or the like. Although the film thickness and constituent materials of each layer constituting the organic layer are not particularly limited, an example is shown below.

The HIL 132 is a buffer layer for increasing the efficiency of hole injection into the EML 134 and preventing leakage. The thickness of the HIL 132 is, for example, 5 nm-200 nm, more preferably set in the range of 8 nm-150 nm. The constituent material of HIL 132 may be appropriately selected in relation to the materials of the electrodes and adjacent layers, for example polyaniline, polythiophene, polypyrrole, polyphenylene vinylene, polythienylene vinylene, polyquinoline, polyquinoxaline and derivatives thereof, aromatic amine Conductive polymers such as polymers containing structures in the main chain or side chains, metal phthalocyanines (copper phthalocyanine, etc.), carbon, and the like are included. Specific examples of conductive polymers include oligoanilines and polydioxythiophenes such as poly(3,4-ethylenedioxythiophene) (PEDOT).

HTL 133 is an organic layer for enhancing hole transport efficiency to EML 134 . The thickness of the HTL 133 can be set in the range of 5 nm to 200 nm, for example, depending on the overall structure of the device. If desired, the thickness of HTL 133 can range from 8 nm-150 nm. Materials constituting HTL133 include light-emitting materials soluble in organic solvents, such as polyvinylcarbazole, polyfluorene, polyaniline, polysilane or derivatives thereof, polysiloxane derivatives having aromatic amines in side chains or main chains, polythiophenes and Derivatives thereof such as polypyrrole or triphenylamine derivatives can be used.

In the EML 134, recombination of electrons and holes occurs when an electric field is applied, and light is emitted. The thickness of the EML 134 can be set to, for example, 10 nm-200 nm, depending on the overall configuration of the device. The thickness of the EML 134 can be 20 nm-150 nm, if desired. Each EML 134 may be a single layer or a laminate structure.

The material constituting the EML 134 may be selected according to each emission color. Examples include coumarin dyes, rhodamine dyes, triphenylamine derivatives, and the above polymers doped with organic EL materials. Examples of dope materials that can be used include rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, and triphenylamine derivatives. As for the material constituting the EML 134, two or more of the above materials may be mixed and used. Further, the material for the organic light-emitting layer 134 is not limited to the high-molecular-weight materials described above, and low-molecular-weight materials may be used in combination. Examples of small molecule materials include anthracene, benzine, styrylamine, triphenylamine, porphyrin, triphenylene, azatriphenylene, tetracyanoquinodimethane, triazole, imidazole, oxadiazole, polyarylalkane, phenylenediamine, arylamine, Examples include oxazole, fluorenone, hydrazone, stilbene, triphenylamine derivatives thereof, and heterocyclic conjugated monomers or oligomers such as polysilane compounds, vinylcarbazole compounds, thiophene compounds, and aniline compounds.

As the material constituting the EML 134, in addition to the materials described above, a material with high luminous efficiency such as a low-molecular fluorescent material, a phosphorescent dye, or an organic luminescent material such as a metal complex can be used as a luminescent guest material. The EML 134 may be, for example, a hole-transporting organic light-emitting layer that also serves as the HTL 133 described above, or may be an electron-transporting organic light-emitting layer that also serves as the ETL 136 described later.

HBL 135 blocks the influx of holes to cathode 137, and may be BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), for example. The thickness of HBL 135 can be, for example, 0.1 nm-100 nm.

ETL 136 is an organic layer for enhancing electron transport efficiency to EML 134 . The thickness of the ETL 136 can be set to, for example, 5 nm-200 nm depending on the overall device configuration. If desired, the thickness of ETL 136 can be set to 10 nm-180 nm. As a material for the ETL 136, an organic material having excellent electron transport ability is preferably used. By increasing the transport efficiency to the EML 134, the change in emission color due to the electric field intensity, which will be described later, is suppressed. Specifically, it is preferable to use an arylpyridine derivative, a benzimidazole derivative, or the like. As a result, high electron supply efficiency is maintained even at a low drive voltage. In addition, alkali metals, alkaline earth metals, rare earth metals and their oxides, composite oxides, fluorides, carbonates and the like are included.

The ETL 136 has an electron-donating property, and as its material, for example, an electron-transporting material doped with an n-type dopant, specifically the materials listed above can be used. Examples of n-type doping materials include alkali metals, alkaline earth metals, oxides, composite oxides, fluorides and organic complexes thereof. In particular, when the electron mobility of ETL136 is relatively high, materials with low electronegativity and excellent electron donating properties can be used. Among these materials, materials having low light absorption in the visible light region in a film state are preferable. Specifically, alkali metals such as Li, Na, K, Rb and Cs, alkaline earth metals such as Be, Mg, Ca, Sr, Ba and Ra, lanthanide metals such as Sm, Yb, Ga and La, etc. metal materials with low electronegativity.

The cathode 137 has a thickness of about 10 nm, for example, and is made of a material with good light transmittance and a small work function. Moreover, light extraction can be ensured also by forming a transparent conductive film using an oxide. In this case, ZnO, ITO, InZnO, InSnZnO, etc. can be used. Further, the cathode 137 may be a single layer, but may have a structure in which a plurality of layers are laminated in order from the anode 131 side, for example. The cathode 137 may be a mixed layer containing an organic light-emitting material such as an aluminumquinoline complex, a styrylamine derivative, a phthalocyanine derivative, or the like. In this case, further layers of Al--Li and Mg--Ag may be provided. Also, the cathode 137 may have an optimum combination and laminated structure depending on the structure of the device to be manufactured.

FIG. 2 shows the pixel structure of the display element using the OLED of this embodiment. It shows one pixel in which OLEDs of each color of RGB are integrated. A front plane 130 is formed on the back plane 122, and PDLs 180a to 180d are patterned to define front planes 130a to 130c of respective RGB colors. Anode 131 of frontplane 130 is connected to a wire in backplane 122 .

A TFE 140 (first inorganic barrier layer 141, organic barrier layer 142 and inorganic barrier layer 143) is laminated to cover the front planes 130a-130c and PDLs 180a-180d to seal the OLED. Furthermore, an optical film 160 of this embodiment described below is laminated via an adhesive layer 150 .

By using a black PDL instead of the conventional polyimide PDL, the black PDL directly absorbs ambient light from the outside (A in FIG. 2) or partially absorbs the light reflected by the anode 131 (FIG. 2). B). Furthermore, it can also absorb leaked light from adjacent OLEDs (C in FIG. 2). Therefore, conventional polyimide PDL with black PDL can be suppressed at high optical density (OD). Also, as will be described later, the black material can suppress leakage current.

FIG. 3 shows the configuration of a conventional polyimide PDL. It shows an example of one pixel 201 in which four OLEDs with R=1, G=2, B=1 are integrated. Parts other than the partition walls surrounding the OLEDs, for example, the upper part 202 of the backplane 122 where the TFTs and wiring are buried, are also desirably covered with a black material in order to reduce reflection from the front. That is, in order to improve the contrast, it is generally preferable to cover the areas other than the aperture areas where the pixels 201 are arranged with the same material as the black PDL. However, if it is desired to increase the transmittance of the OLED display element itself, it is preferable to provide areas not covered with the material.

FIG. 4 shows the configuration of the black PDL of this embodiment. In this embodiment, the black PDL material is patterned to form openings in portions other than the black PDL surrounding the OLEDs of the pixels 211, such as portions 212 of the backplane 122 where the TFTs and wiring are embedded. do. This makes it possible to provide an OLED with high transmittance and improved contrast due to the black PDL. Furthermore, since it can be a transparent OLED, it becomes possible to install a sensor or a camera under the OLED display element.

The black material has low resistivity and causes defects due to leakage current from adjacent pixels and dust from carbon particles added to add conductivity. Many black materials, such as carbon, have a surface resistivity (sheet resistance) of about 10 ¹⁶ Ω/cm ² or less. On the other hand, the surface resistivity of the PDL of the OLED should be 10 ¹⁴ Ω/cm ² or more. Thereby, a black material can be applied, and the leakage current can be suppressed by the black PDL. The volume resistivity (electrical resistivity, specific resistance) of the black material is about 10 ¹⁶ Ω/cm or less. For OLEDs, 10 ¹⁴ Ω/cm or more is sufficient, and the volume resistivity is also sufficient.

Specific examples of black materials include carbon black, acetylene black, lamp black, manganese ferrite, acrylic group-containing resins, polyimide group-containing resins, silicone group-containing resins, fluorine group-containing resins, urethane group-containing resins, and epoxy group-containing resins. At least one. A material containing at least one of manganese ferrite, bone black, graphite, iron black, aniline black, cyanine black, titanium black, aniline black, or iron oxide black pigment may be used as the black material.

Examples of the base material of the black material include acrylic group-containing resins, polyimide group-containing resins, silicone group-containing resins, fluorine group-containing resins, urethane group-containing resins, epoxy group-containing resins, and the like. A mixture in which two or more resins are mixed is preferably used as the base material. Additionally, a black material can be used as the coloring material mixed with the substrate. Examples of black colorants include manganese ferrite, carbon black, acetylene black, lamp black, bone black, graphite, iron black, aniline black, cyanine black, titanium black, aniline black, and iron oxide black pigments.

As the coloring substance mixed in the substrate described above, not only the above black substance but also a mixture of different colored substances having the same light shielding properties as the black substance may be used. For example, such coloring substances are Victoria Pure Blue (42595), Auramine O (41000), Catilone Brilliant Flavin (Basic 13), Rhodamine 6 GCP (45160), Rhodamine B (45170), Safranin OK 70:100 (50240 ), Erio Glausan X (42080), No.120 / Lionol Yellow (21090), Lonar Yellow GRO (21090), Shimla Fast Yellow 8GF (21105), Benzidine Yellow 4T-564D (21095), Shimla Fast Red 4015 (12355) ), Lionol Red 7B4401 (15850), Fastgen Blue TGR-L (74160), Lionol Blue SM (26150), etc. Examples of CI (color index) of applicable pigments are C.I.I. yellow pigments 20, 24, 86, 93, 109, 110, 117, 125, 137, 138, 147, 148, 150, 153, 154, 166, C.I. I. orange pigments 36, 43, 51, 55, 59, 61, C.I. I. red pigment 9, 97, 122, 123, 149, 168, 177, 180, 192, 215, 216, 217, 220, 224, 226, 227, 228, 240, 254, C.I. I. Violet pigment 19, 23, 29, 30, 37, 40, 50, C.I. I. blue pigment 15, 15:1, 15:4, 15:6, 22, 60, 64, C.I. I. Green Pigment 7, 36, C.I. Brown Pigment 23, 25, 26.

Optical density (OD) as an index for specifying PDL is a logarithmic representation of the opacity of a medium, and has the following relationship with transmittance T.
OD=log10(1/T)
For example, OD=1 when T=0.1 (10%) and OD=2 when T=0.01 (1%). The larger the OD, the smaller the T.

FIG. 5 shows an example of the relationship between PDL (OD) and surface reflectance. According to this case, it can be seen that the surface reflectance is saturated at 6% when the OD of the PDL is 1 or more. The surface reflectance is an optical parameter determined by the overall configuration, and it does not univocally saturate at an absolute value of 6%. various relationships. Therefore, the PDL of this embodiment can reduce leakage light to the adjacent OLED by using a material with an OD of 1 or more.

However, part of the light reflected by the anode 131 is still emitted to the outside. Furthermore, in order to reduce the surface reflectance, it is conceivable to add a high OD optical film to the display surface of the OLED display element. However, the OLED output is further reduced and the power consumption of the OLED display element is further increased for a given amount of light. Adding a color filter (CF) may be considered, but it is necessary to match the output spectrum of the OLED and the transmission spectrum of the CF over the visible light range. A surface reflectance of about 7% remains even after alignment, and the effect is low with respect to an increase in manufacturing cost. Although it is conceivable to use an electrode material with a low reflectance for the anode 131, the efficiency of the top emission type OLED is lowered, and the microcavity effect is weakened at a low reflectance.

Therefore, in this embodiment, as shown in FIG. 2, an optical film 160 that reduces the surface reflectance is added. In general use of polarizing plates, the degree of polarization (PE) should be high, for example, PE=100%. On the other hand, in the present embodiment, if the optical film 160 has PE within a predetermined range by combining with black PDL, the average surface reflectance of the OLED display element can be reduced to 10% or less. Furthermore, the optical film 160 with a low PE can be expected to have an effect of improving EQE, so that dimming of the OLED output can be suppressed.

(Example 1)
FIG. 6 shows the structure of the optical film applied to the OLED of this embodiment. Specifically, an LPE (low polarized efficiency) film with PE=65-80% is applied. FIG. 6 is a cross-sectional view in which the emission direction of the OLED 100 (the display surface of the OLED display element) is the upper side of the drawing. It consists of a polarizing coating 162 about 4 μm thick, an adhesive layer (PSA) 163 about 5 μm thick, a quarter-wave plate 164 about 2 μm thick, and an adhesive layer (PSA) 165 about 15 μm thick. In Example 1, as an example, a liquid crystal polarizing plate coated with a so-called liquid crystal is used, and a polarizing film having PE within a predetermined range is obtained by adjusting the concentration of the dichroic dye.

FIG. 7 shows an example of the properties of the LPE film of this embodiment. The solid line is the potential EQE improvement rate by the optical film with low PE and is shown on the left vertical axis scale, and the dashed line is the surface reflectance and is shown on the right vertical axis scale. If the requirements for the OLED display element are a surface reflectance of 10% or less and an EQE improvement rate of 20% or more, the PE of the optical film 160 is in the range of 65% to 80%. Furthermore, if the requirements for a practical OLED display element are relaxed to a surface reflectance of 12.5% or less and an EQE improvement rate of 10% or more, the PE of the optical film 160 is in the range of 60% to 90%.

FIG. 8 shows the output spectrum of the display element using the OLED of this embodiment. Fig. 4 is an output spectrum of an OLED display element with RGB colored OLEDs; The solid line is the case of applying the optical film 160 with PE = 75%, the reflectance of 5.8%, and the expected EQE improvement rate of 30%, and the dashed line is the case of applying the conventional polarizing plate (PE = 99.96%). is. FIG. 9 shows the effect of improving the OLED output by the LPE film of this embodiment compared to the conventional polarizing plate. It can be seen that the LPE film of this embodiment has improved EQE and increased OLED output over the entire visible light range.

(Example 2)
Instead of the liquid crystal polarizing plate, an iodine polarizing plate in which iodine compound molecules are adsorbed and oriented in polyvinyl alcohol (PVA) may be used. By adjusting the concentration of iodine, it is possible to obtain PE within a predetermined range in which the surface reflectance is 10% or less.

(Example 3)
An ND (Neutral Density) filter can also be applied instead of the polarizing plate described above. FIG. 10 shows the characteristics of the neutral density (ND) filter added to the OLED of this embodiment. The solid line is the potential EQE improvement rate by the optical film with low PE and is shown on the left vertical axis scale, and the dashed line is the surface reflectance and is shown on the right vertical axis scale. Assuming that the surface reflectance of 10% or less and the EQE improvement rate of 20% or more are requirements for the OLED display element, the transmittance of the ND filter is in the range of 60-65%. At this time, the OD of the ND filter is 0.22-0.18. As described above, if the surface reflectance is reduced to 12.5% or less and the EQE improvement rate is relaxed to 10% or more, the transmittance of the ND filter will be in the range of 55-70%, and the OD will be 0.26-0.15. .

Comparing FIG. 7 and FIG. 10, it can be seen that the ND filter has a low EQE improvement probability in the desired PE range and a narrow applicable range.
(Example 4)
In addition to Examples 1-3, the configuration of the black PDL shown in FIG. 4 can also be applied. This makes it possible to provide an OLED with high transmittance and improved contrast due to the black PDL and the optical film.

By using a black PDL instead of the conventional polyimide PDL, the black PDL directly absorbs ambient light from the outside (A in FIG. 2) or partially absorbs the light reflected by the anode 131 (FIG. 2). B). Furthermore, it can also absorb leaked light from adjacent OLEDs (C in FIG. 2). Therefore , black PDL, which replaces conventional polyimide PDL, can be suppressed at a high optical density (OD). Also, as will be described later, the black material can suppress leakage current.

FIG. 3 shows the configuration of a conventional polyimide PDL. It shows an example of one pixel 201 in which four OLEDs with R=1, G=2, B=1 are integrated. Parts other than the partition walls surrounding the OLEDs, for example, the upper part 202 of the backplane 122 where the TFTs and wiring are buried, are also desirably coated with the black material 200 in order to reduce reflection from the front. That is, in order to improve the contrast, it is generally preferable to cover the areas other than the aperture areas where the pixels 201 are arranged with the same material as the black PDL. However, if it is desired to increase the transmittance of the OLED display element itself, it is preferable to provide areas not covered with the material.

FIG. 4 shows the configuration of the black PDL of this embodiment. In this embodiment, the black PDL material 210 is patterned to form openings 213 in portions other than the black PDL surrounding the OLEDs of the pixels 211, such as portions 212 of the backplane 122 where TFTs and wiring are embedded. to form This makes it possible to provide an OLED with high transmittance and improved contrast due to the black PDL. Furthermore, since it can be a transparent OLED, it becomes possible to install a sensor or a camera under the OLED display element.

FIG. 5 shows an example of the relationship between the optical density (OD) of PDL and the surface reflectance. According to this case, it can be seen that the surface reflectance is saturated at 6% when the OD of the PDL is 1 or more. The surface reflectance is an optical parameter determined by the overall configuration, and it does not univocally saturate at an absolute value of 6%. various relationships. Therefore, the PDL of this embodiment can reduce leakage light to the adjacent OLED by using a material with an OD of 1 or more.

Claims (6)

In a display element in which an organic light emitting diode (OLED) in which an anode, an organic light emitting layer and a cathode are laminated on a substrate is integrated,
a partition made of a black material surrounding the organic light emitting diode;
and an optical film covering the organic light-emitting diode and the partition wall. The display element according to claim 1, wherein the barrier ribs have a surface resistivity of ¹⁰¹⁴ Ω/cm2 ^or more and a volume resistivity of ¹⁰¹⁴ Ω/cm or more. 3. The display element according to claim 1, wherein the optical density of the partition is 1.0 or more. 4. The display element according to any one of claims 1 to 3, wherein the optical film is a polarizing film having a degree of polarization of 60 to 90%. 4. The display element according to any one of claims 1 to 3, wherein the optical film is a neutral density (ND) filter with an optical density of 0.15-0.26. 2. A portion of the substrate other than the partition surrounding the organic light emitting diode is covered with the black material, and an opening is formed in a part of the covered portion. 6. The display device according to any one of 1 to 5.

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