JP2007026862A - Luminescent panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a luminescent panel having an organic layer protected from current leakage. <P>SOLUTION: In this luminescent panel using an organic EL, an auxiliary electrode layer connected to a transparent electrode layer is arranged. As to the thickness of the auxiliary electrode layer, a part close to a luminescent area is thinner than that of an area far from the luminescent area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light-emitting panel including an organic electroluminescent element (also referred to as an organic EL element) used for a backlight or a lighting device.

  In recent years, light-emitting panels made of organic EL elements have been used as backlights for liquid crystal display screens in lighting equipment and electronic information equipment. FIG. 1 shows a schematic configuration of a cross section of an organic EL element used in an illuminating device or a backlight, and FIG. 2 shows a schematic configuration diagram viewed from above. In FIG. 1, a transparent electrode layer (hereinafter referred to as an anode) 2 is formed on the upper surface of a transparent substrate 1, and an organic EL layer 3 containing a compound that emits light is formed on the upper surface of the anode 2. Further, a metal electrode layer (hereinafter referred to as a cathode) 4 is formed on the upper surface of the organic layer 3. A light emission driving power source 6 is connected to the anode 2 and the cathode 4 via a switch 7. When the switch 7 is turned on, electrons and holes are injected into the organic layer 3, and recombination generates excitons. The entire light emitting area S emits light by using light emission (fluorescence / phosphorescence) when the exciton is deactivated, and can be used as a lighting fixture or a backlight. At this time, light can be emitted with a voltage of several volts to several tens of volts as the light emission driving voltage. Further, since it is a self-luminous type, it has a wide viewing angle and high visibility, and it is a space-saving type because it is a thin-film type completely solid element. Because of these characteristics, it has been attracting attention as a light emission source (see Patent Document 1).

However, in Patent Document 1, only one power receiving unit for supplying power to the anode is provided for one light emitting area. For this reason, there is a problem that luminance unevenness occurs between the light emitting portion close to the power receiving portion and the light emitting portion away from the power receiving portion. This is because the resistance of the transparent electrode layer used for the anode is large, the voltage drop increases as the distance from the anode-side power receiving unit increases, and the light emission luminance decreases. In order to solve such a problem, Patent Document 2 proposes to arrange a low-resistance auxiliary electrode layer in contact with the anode on the outer peripheral portion of the light emitting area.
Japanese Patent Laid-Open No. 10-247401 JP-A-10-199680

  However, in Patent Document 2, there is a problem that a large step is generated between the auxiliary electrode layer and the transparent electrode layer. Therefore, when the light emitting panel is formed, current leakage occurs in the step portion.

  The present invention has been made to solve such a problem, and an object thereof is to provide a light-emitting panel having an organic layer in which current leakage is prevented.

  The inventor conducted extensive research and was able to solve the above problems with any of the configurations described below.

  The light-emitting panel according to claim 1 is a light-emitting panel in which a transparent electrode layer, at least one organic layer including a light-emitting layer, and a metal electrode layer are laminated on a transparent substrate. A light-emitting panel that emits light from a light-emitting region of the light-emitting panel by applying a voltage between the auxiliary electrode layer and the auxiliary electrode layer that supplies power to the transparent electrode layer on the transparent electrode layer, The thickness of the layer is characterized in that the portion closer to the light emitting region is thinner than the portion away from the light emitting region.

  The light-emitting panel according to claim 2 is characterized in that, in the light-emitting panel according to claim 1, the film thickness of the auxiliary electrode layer changes stepwise as the distance from the light-emitting region increases. .

  The light-emitting panel according to claim 3 is the light-emitting panel according to claim 1 or 2, wherein the auxiliary electrode layer in contact with the light-emitting region is thinner than the organic layer. .

  A light-emitting panel according to a fourth aspect is the light-emitting panel according to any one of the first to third aspects, wherein the auxiliary electrode layer is made of the same material as the metal electrode layer.

  A light-emitting panel according to a fifth aspect is the light-emitting panel according to any one of the first to fourth aspects, wherein the auxiliary electrode layer includes aluminum or silver.

  A light emitting panel according to claim 6 is the light emitting panel according to any one of claims 1 to 5, wherein the transparent substrate is a transparent film.

  A light-emitting panel according to a seventh aspect is the light-emitting panel according to any one of the first to sixth aspects, wherein the auxiliary electrode layer is formed in a multilayer structure.

  According to the present invention, the auxiliary electrode layer is connected to the transparent electrode layer, and the thickness of the auxiliary electrode layer is reduced at the portion in contact with the light emitting region. Therefore, the auxiliary electrode layer is disposed between the auxiliary electrode layer and the metal electrode layer. A light-emitting panel with low current leakage occurrence probability can be provided.

  A preferred embodiment of the light-emitting panel according to the present invention will be described below with reference to the drawings.

  FIG. 3 shows a schematic cross-sectional view of a light-emitting panel using the organic EL element according to the present invention.

  A transparent anode 2 is formed on the upper surface of the transparent substrate 1, and a hole transport layer 31 is provided on the upper surface of the anode 2. Further, a light emitting layer 30 is provided on the upper surface of the hole transport layer 31, and a hole blocking layer 32 is provided on the upper surface. An electron transport layer 33 is provided on the upper surface of the hole blocking layer 32, and a cathode 4 is further provided on the upper surface of the electron transport layer 33 to constitute an organic EL element. This organic EL element is sealed with a sealing can 5 by an adhesive 52 to constitute a light emitting panel. A water retention agent 51 is attached to the inner surface of the sealing can 5. The anode 2 and the cathode 4 are connected to a power supply unit 8 via a control IC 9.

  FIG. 4 shows an example of an electrode structure in one pixel of the light-emitting panel according to the present invention. The anode 2 formed on the transparent substrate 1, the auxiliary electrode layer 20 for supplying power to the anode 2, the organic EL layer 3, and the like. Sectional drawing of each shape and schematic arrangement | positioning of the cathode 4 is shown. The auxiliary electrode layer 20 includes a first auxiliary electrode layer 21, a second auxiliary electrode layer 22, and a third auxiliary electrode layer 23.

  FIG. 5 shows a plan view of the schematic arrangement shown in FIG. 4 as viewed from the upper surface on the cathode 4 side. S indicates the outer shape of the light emitting region.

  FIG. 6 is a plan view showing an example of the light-emitting panel according to the present invention, which is a light-emitting panel in which a large number of pixels shown in FIG. The anode 2 is formed in a line on the transparent substrate 1, and the cathode 4 is also formed in a line in the organic EL layer.

  The power supplied from the power supply unit 8 is connected to the cathode 4 on the negative electrode side via the control IC 9 and supplied to the anode 2 via the auxiliary electrode layer 20 on the positive electrode side.

  The AA cross section in FIG. 5 is shown in FIG. As for the thickness of the auxiliary electrode layer 20, the portion closest to the light emitting region S is t <b> 1, and as the distance from the light emitting region S increases, the thickness increases gradually from t <b> 2 to t <b> 3. In this way, by reducing the thickness of the portion of the auxiliary electrode layer 20 in contact with the light emitting region S, current leakage that occurs near the light emitting region S can be prevented, and the light emitting panel having uniform light emission luminance Can be obtained.

  The phenomenon of current leakage in the light-emitting panel having the auxiliary electrode layer 20 has not yet been fully elucidated, but can be considered as follows.

  FIG. 8 shows a schematic configuration diagram of a light emitting panel having a shape of a conventional auxiliary electrode layer 20 for comparison. It is considered that the current leak occurs at the portion indicated by the broken line, and occurs between the point B and the point C, where the electric field strength is strongest, between the auxiliary electrode layer 20 and the cathode 4. It is thought that. This is because the film resistance value of the organic EL layer in the light emitting region is substantially reduced by emitting light in the light emitting region, and dielectric breakdown occurs in a portion where the electric field strength is strong between the auxiliary electrode layer and the cathode in the light emitting region edge, It is presumed that current leakage has occurred. In view of this point, the inventor considered the prevention of current leakage by reducing the thickness of the auxiliary electrode layer at the edge of the light emitting region where breakdown is likely to occur.

  FIG. 9 shows a schematic configuration diagram as an embodiment of the present invention in which the number of steps shown in FIG. The thickness t3 ′ of the auxiliary electrode layer 20 was the same as that of the conventional configuration in FIG. 8 from the viewpoint of power supply to the anode. In FIG. 9, by reducing the thickness of the auxiliary electrode layer closest to the light emitting region, the electric field strengths at points B ′ and C ′ become smaller than the electric field strengths at points B and C shown in FIG. I understand that. By doing so, it is considered that the dielectric breakdown between the auxiliary electrode layer 20 and the cathode 4 that occurs in the vicinity of the light emitting region is prevented, and current leakage does not occur.

  Further, it is preferable that the height of each step of the auxiliary electrode layer 20 is lower than the thickness of the organic EL layer, so that current leakage is further prevented.

  Hereinafter, the structure of the light emission panel of embodiment is demonstrated concretely.

  The transparent substrate 1 may be a transparent material, and transparent glass or transparent plastic can be used. For example, a transparent plastic substrate such as polycarbonate (PC), polyethersulfone (PES), polyarylate (PAR), or polyethylene terephthalate (PET) can be used. If the transparent substrate 1 is a transparent plastic film, it can be said that it is more preferable because it is resistant to deformation and impact due to external force, is difficult to break, is lightweight, and is highly portable.

  As the anode 2 that is a transparent electrode, for example, a transparent conductive film such as Indium Tin Oxide (ITO: Indium Tin Oxide) or Indium Zinc Oxide (IZO: Indium Zinc Oxide) can be used. Such a material can be formed on the transparent substrate 1 by mask deposition by vapor deposition, full vapor deposition or coating, and then patterned by photolithography, or by screen printing. The film thickness of the anode 2 is not particularly limited, but is usually 10 nm to 2 μm, preferably 20 nm to 1 μm.

  The auxiliary electrode layer 20 is not particularly limited as long as it is a metal material having a resistance lower than that of the anode 2, but is preferably the same as the material used for the cathode 4. If the material of the auxiliary electrode layer 20 is the same material as that of the cathode 4, it is not necessary to prepare many electrode materials, and the productivity is high. Further, by using a material having a resistance lower than that of the anode 2, it is possible to supply power to the anode with almost no voltage drop.

  In particular, if the auxiliary electrode layer 20 contains aluminum or silver, it is good from the viewpoint of conductivity and ease of handling.

  Examples of the method for forming the auxiliary electrode layer 20 include a sputtering method, a resistance heating vapor deposition method, and an electron beam vapor deposition method. Using a metal mask, the first auxiliary electrode layer can be formed to a predetermined thickness, and then the second auxiliary electrode layer 22 and the third auxiliary electrode layer 23 can be formed by a similar method.

  The hole transport layer 31 has a function of transporting holes from the anode 2 to the light emitting layer 30. As a hole transport material in the hole transport layer 31, any material generally used for an organic EL element can be used. For example, a triazole derivative, an oxadiazole derivative, an imidazole derivative, an aromatic tertiary amine compound, and the like. Can be used. This hole transport material can be formed on the upper surface of the anode 2 by making it into a thin film by a known method such as a vacuum deposition method, a spin coating method, a casting method, an ink jet method, or an LB method. Although there is no restriction | limiting in particular as a film thickness of the positive hole transport layer 31, Usually, it is about 5 nm-5000 nm.

  The light emitting layer 30 is composed of at least one kind of organic compound involved in the light emitting function. The light emitting layer 30 has a hole and electron injection function, a transport function thereof, and a function of generating excitons by recombination of holes and electrons. As the material of the light emitting layer 30, known materials generally used in organic EL elements can be used. For example, quinolinolato complexes are known. Specifically, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis (benzo {f} -8-quinolinolato) zinc, bis (2-methyl-8-quinolinolato) aluminum oxide, tris (8 -Quinolinolato) indium, tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-8-quinolinolato) gallium, bis (5-chloro-8-quinolinolato) calcium, 7-dichloro-8-quinolinolato aluminum, tris (5,7-dibromo-8-hydroxyquinolinolato) aluminum, poly [zinc (II) -bis (8-hydroxy-5-quinolinyl) methane], etc. . Although there is no restriction | limiting in particular as the film thickness of the light emitting layer 30, Usually, it is about 5 nm-5000 nm.

  The hole blocking layer 32 has a function of transporting electrons and transporting holes significantly, and improves the recombination probability of electrons and holes by blocking holes while transporting electrons. Can do.

  As the hole blocking layer 32, for example, JP-A-11-204258, JP-A-11-204359, and “Organic EL element and its forefront of industrialization (November 30, 1998, NTS light emission)” Can be applied as the hole blocking layer 32 according to the present invention.

  The electron transport layer 33 is only required to have a function of transmitting electrons injected from the cathode 4 to the light emitting layer 30. The electron transport material is arbitrarily selected from known materials generally used for organic EL elements. You can choose. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, aromatic tetracarboxylic anhydrides such as naphthalene and perylene, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives Etc. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. The electron transport layer 33 can be formed by thinning the electron transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of the electron carrying layer 33, Usually, it is about 5-5000 nm.

  As the cathode 4, a normal metal can be used. Among these, from the viewpoint of conductivity and ease of handling, one or more metal elements selected from Al, Ag, In, Ti, Cu, Au, Mg, Mo, W, and Pt are preferable. Examples of the method for forming the cathode 4 include sputtering, resistance heating vapor deposition, and electron beam vapor deposition. By using a metal mask, it can be formed so as to overlap with the region of the first auxiliary electrode layer 21 and not overlap with the region of the second auxiliary electrode layer 22. Although there is no restriction | limiting in particular about the film thickness of the cathode 4, Usually, it is about 5-500 nm.

  The organic EL device produced as described above was adhered and sealed to the glass sealing can 5 by irradiating an ultraviolet lamp with an ultraviolet curable adhesive 52 to produce a light emitting panel according to the present invention. At this time, the organic EL element and the sealing can 5 are preferably bonded in a nitrogen atmosphere so as not to come into contact with the air. This is because the moisture in the air and the organic EL layer such as the light emitting layer are prevented from deteriorating due to the reaction. Moreover, it is preferable to put a water replenisher 51 inside the sealing can 5. This is because the influence of a minute amount of moisture remaining in the sealing can is collected to prevent the deterioration of the organic EL layer.

  Next, a driving method of the light emitting panel according to the present invention will be described.

  The power supply unit 8 outputs potentials + V1 and −V1 for driving the organic EL element. This output voltage is applied to the anode 2 and the cathode 4 through the auxiliary electrode layer 20 using the control IC 9. By doing so, current leakage between the auxiliary electrode layer 20 and the cathode can be prevented, and a light emitting panel with excellent productivity can be provided.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.
Example 1
The electrode configuration shown in FIGS. 5 and 7 was produced. FIG. 10 shows a flow of manufacturing the light emitting panel. An anode 2 was formed on the substrate 1, and a first auxiliary electrode layer 21, a second auxiliary electrode layer 22, and a third auxiliary electrode layer were formed thereon. Next, after forming four layers of a hole transport layer 31, a light emitting layer 30, a hole blocking layer 32, and an electron transport layer 33, the cathode 4 was formed. This will be described in more detail below.

  As the substrate 1 and the anode 2, a substrate (made by NH Techno Glass Co., Ltd .: NA-45) in which ITO was deposited to a thickness of 150 nm on 75 mm × 75 mm glass was used.

  Next, this transparent support substrate was ultrasonically cleaned with iso-propyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.

Thereafter, this transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, and stainless steel is processed on the anode 2 so as to have the shape of the first auxiliary electrode layer 21 (opening is 45 mm × 45 mm). On the other hand, 3 g of aluminum was put into a molybdenum resistance heating boat and attached to a vacuum deposition apparatus. Next, after reducing the pressure of the vacuum chamber to 4 × 10 ⁻⁴ Pa, the heating boat containing aluminum was energized and heated, and the deposition rate was 1.5 nm / second to 2.0 nm / second through a metal mask. Vapor deposition was performed to a thickness of 50 nm, and the first auxiliary electrode layer 21 was provided.

Next, the vacuum chamber is opened, and the shape of the second auxiliary electrode layer 22 having an opening larger than that of the first auxiliary electrode layer 21 is formed on the first auxiliary electrode layer 21 (the opening is 46 mm × 46 mm). A stainless steel mask processed so as to be installed was installed, and on the other hand, 3 g of aluminum was put in a resistance heating boat made of molybdenum and attached to a vacuum deposition apparatus. Next, after reducing the pressure of the vacuum chamber to 4 × 10 ⁻⁴ Pa, the heating boat containing aluminum was energized and heated, and the deposition rate was 1.5 nm / second to 2.0 nm / second through a metal mask. The second auxiliary electrode layer 22 was provided by vapor deposition so as to have a film thickness of 50 nm.

Next, the vacuum chamber is opened, and the shape of the third auxiliary electrode layer 23 having an opening larger than that of the second auxiliary electrode layer 22 is formed on the second auxiliary electrode layer 22 (opening is 47 mm × 47 mm). A stainless steel mask processed so as to be installed was installed, and on the other hand, 3 g of aluminum was put in a resistance heating boat made of molybdenum and attached to a vacuum deposition apparatus. Next, after reducing the pressure of the vacuum chamber to 4 × 10 ⁻⁴ Pa, the heating boat containing aluminum was energized and heated, and the deposition rate was 1.5 nm / second to 2.0 nm / second through a metal mask. Vapor deposition was performed to a thickness of 50 nm, and a third auxiliary electrode layer 23 was provided.

Next, the vacuum chamber is opened and a stainless steel mask is installed. On the other hand, α-NPD, CBP, Ir-1, BCP, and Alq ₃ shown in the following structure are placed in five resistance heating boats made of molybdenum. It was attached to a vacuum evaporation system.

Next, after reducing the vacuum tank to 4 × 10 ⁻⁴ Pa, the heating boat containing α-NPD was heated by heating to form a transparent support substrate at a deposition rate of 0.1 nm / second to 0.2 nm / second. The hole transport layer 31 was provided by vapor deposition so as to have a thickness of 50 nm.

  Further, the heating boat containing CBP and the boat containing Ir-1 are energized independently to adjust the deposition rate of CBP and Ir-1 as the light emitting materials to 100: 7, so that the film thickness is 30 nm. The light emitting layer 30 was provided by vapor deposition so as to have a thickness.

Next, the heating boat containing BCP was energized and heated to provide a hole blocking layer 32 having a thickness of 10 nm at a deposition rate of 0.1 nm / second to 0.2 nm / second. Further, the heating boat containing Alq ₃ was heated by energization to provide an electron transport layer 33 having a film thickness of 40 nm at a deposition rate of 0.1 nm / second to 0.2 nm / second.

Next, the vacuum chamber is opened, and a stainless steel mask for cathode is placed on the electron transport layer 33. On the other hand, 3 g of aluminum is put into a molybdenum resistance heating boat, and the vacuum chamber is again 2 × 10 ^−4. After reducing the pressure to Pa, a boat containing aluminum was energized to deposit aluminum at a deposition rate of 1.5 nm / second to 2.0 nm / second, thereby preparing a cathode 4 (thickness 200 nm).

  Further, the organic EL element was transferred to a glove box under nitrogen atmosphere (a glove box substituted with high-purity nitrogen gas having a purity of 99.999% or more) without being brought into contact with the atmosphere, and a schematic diagram shown in FIG. A light emitting panel using an organic EL element was manufactured in a sealed structure.

  In FIG. 3, barium oxide 51, which is a water replenisher, is a high-purity barium oxide powder manufactured by Aldrich, a fluororesin semipermeable membrane with adhesive (Microtex: S-NTF8031Q (Nitto Denko)). What was affixed on the glass sealing can 5 was prepared and used beforehand. A UV curable adhesive 52 was used for bonding between the sealing can and the organic EL element, and a light emitting panel was fabricated by adhering and sealing both by irradiating an ultraviolet lamp.

Ten samples of the light-emitting panel thus prepared were prepared, each sample was caused to emit light by passing a current with a current density of 25 A / m ² , and light emission of each sample was performed using a luminance meter (CS1000A) manufactured by Konica Minolta Sensing. In-plane brightness unevenness was measured. In each sample, no leakage of current was observed, and the yield rate was 100%.
(Comparative Example 1)
Ten samples were produced under the same conditions except that the first auxiliary electrode layer 21 in Example 1 was formed to a thickness of 150 nm and the second auxiliary electrode was not provided. When light was emitted by applying a current density of 25 A / m ^{2 to} each sample, current leakage occurred in 5 samples and no light was emitted. The yield rate was 50%.
(Examples 2 to 8)
Examples 2 to 8 were made under the same conditions except that the film thicknesses of the first auxiliary electrode layer 21, the second auxiliary electrode layer 22, and the third auxiliary electrode layer 23 in Example 1 were changed to the values shown in Table 1. 10 samples of each light emitting panel were prepared. The non-defective rate at this time is shown in Table 1.

  From these results, it can be said that the thickness of the first auxiliary electrode layer 21 is more preferably lower than the thickness of the organic layer.

It is a schematic block diagram of the organic EL element used for an illuminating device or a backlight. It is the schematic block diagram which looked at the organic EL element from the upper surface. It is the figure which showed typically sectional drawing of the light emission panel which concerns on this invention. It is sectional drawing which showed typically an example of the electrode structure in 1 pixel of the light emission panel which concerns on this invention. It is the top view which showed typically an example of the electrode structure in 1 pixel of the light emission panel which concerns on this invention. It is a top view which shows an example of the light emission panel which concerns on this invention. It is a figure which shows the AA cross section in FIG. The schematic block diagram of the auxiliary electrode layer of the conventional light emission panel is shown. It is sectional drawing which showed typically an example of the electrode structure in 1 pixel of the light emission panel which concerns on this invention. It is the schematic diagram which showed an example of the manufacturing flow of the light emission panel which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Anode 20 Auxiliary electrode layer 21 1st auxiliary electrode layer 22 2nd auxiliary electrode layer 23 3rd auxiliary electrode layer 3 Organic layer 30 Light emitting layer 31 Hole transport layer 32 Hole blocking layer 33 Electron transport layer 4 Cathode 5 Sealing can 51 Water replenisher 52 Adhesive 6 Light emission drive power supply 7 Switch 8 Power supply unit 9 Control IC

Claims (7)

Applying a voltage between the transparent electrode layer and the metal electrode layer of a light-emitting panel in which a transparent electrode layer, at least one organic layer including a light-emitting layer, and a metal electrode layer are laminated on a transparent substrate In the light-emitting panel in which the light-emitting region of the light-emitting panel is caused to emit light, an auxiliary electrode layer that supplies power to the transparent electrode layer is provided on the transparent electrode layer, and the thickness of the auxiliary electrode layer is separated from the light-emitting region A light emitting panel characterized in that a portion closer to the light emitting region is formed thinner than the other. The light emitting panel according to claim 1, wherein the thickness of the auxiliary electrode layer changes stepwise as the distance from the light emitting region increases. 3. The light-emitting panel according to claim 1, wherein a thickness of the auxiliary electrode layer in contact with the light-emitting region is thinner than a thickness of the organic layer. 4. The light-emitting panel according to claim 1, wherein the auxiliary electrode layer is made of the same material as the metal electrode layer. 5. 5. The light-emitting panel according to claim 1, wherein a material of the auxiliary electrode layer includes aluminum or silver. The light emitting panel according to claim 1, wherein the transparent substrate is a transparent film. The light emitting panel according to claim 1, wherein the auxiliary electrode layer is formed in a multilayer structure.

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