JP2004287396A - Optical waveguide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide film which is excellent in flexibility and which has shorter manufacturing processes and whose manufacturing is easy and moreover which is excellent in propagation loss. <P>SOLUTION: This optical waveguide film is composed of a lower cladding, a core formed on the lower cladding, side claddings formed at the upper part of the lower cladding and at side parts of the core and upper claddings formed above the core and the side claddings, and the core consists of a photobleaching material and the side cladding consists of material whose refractive index is lowered by subjecting the photobleaching material exposed to ultraviolet rays and at least part of the lower cladding and the upper cladding comprises a polyimide resin. Thus, the optical waveguide film which is excellent in flexibility is obtained and the film whose manufacturing process is short and whose manufacture is easy is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical waveguide film using a polyimide resin and a photobleaching material, and a method for manufacturing the same.

  2. Description of the Related Art With the spread of personal computers and the Internet in recent years, demand for information transmission has been rapidly increasing. For this reason, it is desired that optical transmission with a high transmission speed be spread to terminal information processing devices such as personal computers. In order to realize this, it is necessary to manufacture inexpensively and in large quantities a small optical transceiver module that integrates the transmission function and the reception function using a high-performance optical waveguide for optical interconnection. .

  As materials for the optical waveguide, inorganic materials such as glass and semiconductor materials, and resins are known. Various resins are known as the resin constituting the optical waveguide (core) and the clad, but polyimide resins having a high glass transition temperature (Tg) and excellent heat resistance are particularly expected. When the core and the clad are formed of a polyimide resin, long-term reliability can be expected, and they can withstand soldering.

Conventionally, such an optical waveguide composed of a core and a clad is formed on a thick substrate made of an inorganic material such as glass or silicon or an organic material such as an acrylic resin, and therefore has no flexibility. For this reason, it has been difficult to use the optical fiber for flexible optical wiring and branching.
In view of this, a flexible polymer optical waveguide film composed of only a core and a clad made of a polyimide-based resin has been produced (see Patent Document 1). Such a polymer optical waveguide film is formed by providing a clad on a substrate of glass, silicon, or the like, providing a core layer on the clad, forming a core from this, and providing the clad so as to cover the core. And then peeling the film from the substrate. However, in order to form a core, complicated steps such as use of a photomask, development, and etching are required. Further, the optical waveguide film made of a polyimide resin has a problem that the propagation loss cannot be sufficiently reduced.

JP 2001-166166 A

  An object of the present invention is to provide an optical waveguide film having excellent flexibility, which has a short manufacturing process and is easy to manufacture, and a method for manufacturing the same. It is another object of the present invention to provide an optical waveguide film having further excellent propagation loss and a method for manufacturing the same.

The above object is constituted by a lower clad, a core formed on the lower clad, a side clad formed on the lower clad upper part and the core side part, and an upper clad formed on the core and the side clad. An optical waveguide film, wherein the core is made of a photobleaching material, and the side cladding is made of a material whose refractive index is reduced by UV exposure of the photobleaching material. It has been found that the problem is solved by an optical waveguide film at least partially made of a polyimide resin.
The object is also to provide a step of providing a lower clad on a silicon substrate on which a silicon oxide film is formed, a step of providing a core layer made of a photobleaching material on the lower clad, and a portion to be a core in the core layer. A step of forming a core and a side clad by exposing a part other than UV, and a step of providing an upper clad on the core and the side clad, provided that at least a part of the lower and upper clad is made of a polyimide resin. Is performed in this order to form an optical waveguide structure on a silicon substrate, and the optical waveguide structure is immersed in water and peeled off from the silicon substrate to solve the problem.

  According to the present invention, an optical waveguide film having excellent flexibility can be obtained, and an optical waveguide film having a short manufacturing process and easy manufacturing can be obtained. That is, since the core material of the optical waveguide film of the present invention uses a photobleaching material whose refractive index is reduced by UV exposure, after the core layer is formed, portions of the core layer other than the portion to be the core are exposed to UV. Exposure can form side cladding. Therefore, there is no need to form a core by etching the core layer or the like, so that the manufacturing process can be shortened, the manufacturing is easy, and the manufacturing cost is low. In addition, the optical waveguide film of the present invention has sufficient flexibility as a film because a polyimide resin is used for at least a part of the upper clad and the lower clad.

  Further, the optical waveguide film of the present invention shows a very excellent effect on the propagation loss as compared with the optical waveguide film composed of only the polyimide resin. One possible reason for this is that the flatness of the side surface of the core is maintained because there is no manufacturing process such as etching of the core layer. Also, when polysilane is used as the photobleaching material, it is preferable because it shows particularly excellent propagation loss.

  FIG. 1 shows a cross-sectional view of one embodiment of the optical waveguide film of the present invention. Referring to FIG. 1, one optical waveguide film of the present invention comprises a lower clad 2, a core 3 formed on the lower clad 2, a side clad 4 formed on the upper part of the lower clad 2 and a side of the core 3, and a core. 3. An optical waveguide film comprising an upper clad 5 formed on a side cladding 3 and a side cladding 4, wherein the core 3 is made of a photobleaching material, and the side cladding 4 is made by exposing the photobleaching material to UV light. Thus, the lower clad 2 and the upper clad 5 are made of a material whose refractive index is lowered, and the optical waveguide film is made of a polyimide resin.

As another embodiment of the optical waveguide film of the present invention, the lower clad 2, the core 3 formed on the lower clad 2, the side clad 4 formed on the upper part of the lower clad 2 and the side of the core 3, and the core 3. An optical waveguide film comprising an upper clad 5 formed on a side clad 4, wherein the core 3 is made of a photobleaching material, and the side clad 4 is configured to subject the photobleaching material to UV exposure. The lower clad 2 and the upper clad 5 are made of a material whose refractive index has been reduced, and at least a part of the lower clad 2 and the upper clad 5 is an optical waveguide film made of a polyimide resin.
“At least a part of the lower clad 2 and the upper clad 5 is made of a polyimide resin”. One of the lower clad 2 and the upper clad 5 may be made of a polyimide resin. Alternatively, a part of the upper clad 5 may be made of a polyimide resin. The case where a part of the lower clad 2 and / or the upper clad 5 is made of a polyimide resin is, for example, a case where the lower clad 2 and / or the upper clad 5 is made of two layers and one of them is made of a polyimide resin. No.

  Another preferred embodiment of the optical waveguide film of the present invention is an optical waveguide film in which the lower clad is made of a polyimide resin and the upper clad is made of polysilanes.

  Examples of the upper and lower cladding materials other than the polyimide resin include a photobleaching material, an acrylic resin, an epoxy resin, and the like, which will be described later.

  In the present invention, the “optical waveguide film” means a flat optical waveguide film having a core-clad structure, which does not include a substrate or a portion corresponding thereto.

  In the present invention, “photobleaching material” refers to a material whose refractive index changes by irradiation with light such as UV light. Specific examples include polysilane, a silicone compound to which a nitrone compound is added, polymethyl methacrylate containing (4-N, N-dimethylaminophenyl) -N-phenylnitrone, and a dye polymer.

  Polysilanes are particularly preferable as such a photobleaching material from the viewpoint of propagation loss. Examples of the polysilanes include branched or linear polysilanes. The branched polysilane refers to a polysilane containing Si atoms in which the number of bonds between Si atoms and adjacent Si atoms is 3 or 4. The linear polysilane refers to a polysilane in which the number of bonds between a Si atom and an adjacent Si atom is two.

  Since the valence of a Si atom is usually 4, the Si atom having a bond number of 3 or less present in the polysilane is bonded to a hydrocarbon group, an alkoxy group, an aryloxy group, or a hydrogen atom in addition to the Si atom. As such a hydrocarbon group, an aliphatic hydrocarbon group which may be substituted by a halogen having 1 to 10 carbon atoms and an aromatic hydrocarbon group having 1 to 14 carbon atoms are preferable. Specific examples of the aliphatic hydrocarbon group include a methyl group, a propyl group, a butyl group, an octyl group, a decyl group, a trifluoropropyl group, and a chain type such as a nonafluorohexyl group, and a cyclohexyl group and a methylhexyl group. And the like alicyclic type. Further, specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, a biphenyl group, and an anthracyl group.

  Examples of the alkoxy group or the aryloxy group include those having 1 to 8 carbon atoms. Specific examples include a methoxy group, a phenoxy group, an octyloxy group and the like. Considering ease of synthesis, among these groups, a methyl group and a phenyl group are particularly preferred.

As the polyimide resin constituting at least a part of the upper and lower clads of the optical waveguide film of the present invention, a polyimide resin containing fluorine is particularly preferable from the viewpoint of heat resistance.
Examples of the polyimide resin containing fluorine include a polyimide resin containing fluorine, a poly (imide / isoindoloquinazolinedionimide) resin containing fluorine, a polyetherimide resin containing fluorine, and a polyamideimide resin containing fluorine.

  The precursor solution of the above-mentioned fluorine-containing polyimide resin is prepared by dissolving tetracarboxylic dianhydride and diamine in a polar solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, γ-butyrolactone, and dimethyl sulfoxide. It is obtained by reacting. Fluorine may be contained in both the tetracarboxylic dianhydride and the diamine, or may be contained in only one of them.

  In addition, the precursor solution of the above-mentioned polyimide resin containing no fluorine is prepared from a tetracarboxylic acid containing no fluorine in a polar solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, γ-butyrolactone, and dimethyl sulfoxide. It is obtained by reacting an acid dianhydride with a diamine containing no fluorine.

  Examples of acid dianhydrides containing fluorine include (trifluoromethyl) pyromellitic dianhydride, di (trifluoromethyl) pyromellitic dianhydride, di (heptafluoropropyl) pyromellitic dianhydride, Pentafluoroethyl pyromellitic dianhydride, bis {3,5-di (trifluoromethyl) phenoxy} pyromellitic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride 5,5'-bis (trifluoromethyl) -3,3 ', 4,4'-tetracarboxybiphenyl dianhydride, 2,2', 5,5'-tetrakis (trifluoromethyl) -3, 3 ', 4,4'-tetracarboxybiphenyl dianhydride, 5,5'-bis (trifluoromethyl) -3,3', 4,4'-tetracarboxydiphenyl Terdianhydride, 5,5'-bis (trifluoromethyl) -3,3 ', 4,4'-tetracarboxybenzophenone dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} benzene dianhydride, Bis {(trifluoromethyl) dicarboxyphenoxy} (trifluoromethyl) benzene dianhydride, bis (dicarboxyphenoxy) (trifluoromethyl) benzene dianhydride, bis (dicarboxyphenoxy) bis (trifluoromethyl) benzene Dianhydride, bis (dicarboxyphenoxy) tetrakis (trifluoromethyl) benzene dianhydride, 2,2-bis {(4- (3,4-dicarboxyphenoxy) phenyl} hexafluoropropane dianhydride, bis} (Trifluoromethyl) dicarboxyphenoxy dibiphenyl dianhydride Bis {(trifluoromethyl) dicarboxyphenoxy} bis (trifluoromethyl) biphenyl dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} diphenyl ether dianhydride, bis (dicarboxyphenoxy) bis (trifluoromethyl) Biphenyl dianhydride and the like.

  Examples of the diamine containing fluorine include 4- (1H, 1H, 11H-eicosafluoroundecanooxy) -1,3-diaminobenzene and 4- (1H, 1H-perfluoro-1-butanoxy) -1. , 3-diaminobenzene, 4- (1H, 1H-perfluoro-1-heptanoxy) -1,3-diaminobenzene, 4- (1H, 1H-perfluoro-1-octanoxy) -1,3-diaminobenzene, 4-pentafluorophenoxy-1,3-diaminobenzene, 4- (2,3,5,6-tetrafluorophenoxy) -1,3-diaminobenzene, 4- (4-fluorophenoxy) -1,3-diamino Benzene, 4- (1H, 1H, 2H, 2H-perfluoro-1-hexanoxy) -1,3-diaminobenzene, 4- (1H, 1H, 2H, 2H- -Fluoro-1-dodecanoxy) -1,3-diaminobenzene, 2,5-diaminobenzotrifluoride, bis (trifluoromethyl) phenylenediamine, diaminotetra (trifluoromethyl) benzene, diamino (pentafluoroethyl) benzene, , 5-diamino (perfluorohexyl) benzene, 2,5-diamino (perfluorobutyl) benzene, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 3,3'-bis ( (Trifluoromethyl) -4,4'-diaminobiphenyl, octafluorobenzidine, 4,4'-diaminodiphenyl ether, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,3-bis (anilino) hexafluoro Propane, 1,4-bis (anilino) oct Fluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetradecafluoroheptane, 2,2′-bis (trifluoromethyl) -4,4′-diaminodiphenyl ether, 3, 3'-bis (trifluoromethyl) -4,4'-diaminodiphenyl ether, 3,3 ', 5,5'-tetrakis (trifluoromethyl) -4,4'-diaminodiphenyl ether, 3,3'-bis ( (Trifluoromethyl) -4,4'-diaminobenzophenone, 4,4'-diamino-p-terphenyl, 1,4-bis (p-aminophenyl) benzene, p-bis (4-amino-2-trifluoro) Methylphenoxy) benzene, bis (aminophenoxy) bis (trifluoromethyl) benzene, bis (aminophenoxy) tet Lakis (trifluoromethyl) benzene, 2,2-bis {4- (4-aminophenoxy) phenyl} hexafluoropropane, 2,2-bis {4- (3-aminophenoxy) phenyl} hexafluoropropane, 2, 2-bis {4- (2-aminophenoxy) phenyl} hexafluoropropane, 2,2-bis {4- (4-aminophenoxy) -3,5-dimethylphenyl {hexafluoropropane, 2,2-bis} 4- (4-aminophenoxy) -3,5-ditrifluoromethylphenyl @ hexafluoropropane, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) biphenyl, 4,4'-bis (4 -Amino-3-trifluoromethylphenoxy) biphenyl, 4,4'-bis (4-amino-2-trifluoromethylf Noxy) diphenylsulfone, 4,4'-bis (3-amino-5-trifluoromethylphenoxy) diphenylsulfone, 2,2-bis {4- (4-amino-3-trifluoromethylphenoxy) phenyl} hexafluoro Propane, bis {(trifluoromethyl) aminophenoxy} biphenyl, bis [{(trifluoromethyl) aminophenoxy} phenyl] hexafluoropropane, bis {2-[(aminophenoxy) phenyl] hexafluoroisopropyl} benzene and the like Can be Two or more of the above tetracarboxylic dianhydrides and diamines may be used in combination.

  FIG. 2 is a view showing one embodiment of the method for producing an optical waveguide film of the present invention. The manufacturing method of the present invention will be described with reference to FIG. A lower clad 2 (preferably 5 to 30 μm in thickness) made of a polyimide resin is provided on a silicon substrate 1 (preferably 0.5 to 10 μm in thickness) on which a silicon oxide film is formed (FIG. 2A). ). A core layer (preferably, 4 to 15 μm in thickness) made of a photobleaching material is provided on the lower clad 2 (FIG. 2B). The core layer is exposed to UV through a core-shaped mask (FIG. 2- (c)). The refractive index of the photobleaching material in the UV-exposed portion changes, and the core 3 and the side cladding 4 are formed (FIG. 2- (d)). An upper clad 5 (preferably 5 to 30 μm in thickness) made of a polyimide resin is provided so as to cover the core 3 and the side clad 4 (FIG. 2E).

Further, as another aspect of the present invention, in the above manufacturing method, one of the lower clad 2 and the upper clad 5 is provided using a material made of a polyimide resin, and any of the remaining clads is made of a material other than the polyimide resin. It is provided using a resin material, preferably a polysilane.
As another preferred embodiment of the present invention, in the above-described manufacturing method, the lower clad 2 is provided using a material made of a polyimide resin, and the upper clad 5 is provided using a polysilane material.

  The optical waveguide structure of the present invention is manufactured by immersing the optical waveguide structure thus manufactured on the silicon substrate in water and peeling it from the silicon substrate (FIG. 2- (f)).

  A more preferred embodiment of the manufacturing method of the present invention further includes a step of performing post-baking after the step of exposing a portion other than a portion to be a core to UV exposure in the above-described manufacturing method. The post-bake step is preferable because the relative refractive index is stabilized. Post-baking is preferably performed at 300 to 400 ° C. for about 10 to 60 minutes (hour).

  The step of exposing a portion other than a portion to be a core to UV exposure is more specifically performed by applying a mask to a portion corresponding to the core and irradiating a portion of the unmasked portion with UV from above the mask to form a photobleaching material. Changing the refractive index includes changing the original refractive index, that is, the refractive index lower than the refractive index of the portion remaining as the core.

The UV light source used for UV exposure of the core layer includes a light source having an ultraviolet region, preferably a wavelength region of 250 nm or less, and specifically includes a xenon-mercury lamp. The irradiation intensity is about 0.2 J / cm ² per 1 μm, but can be appropriately changed depending on the film thickness.

  The polyimide-based resin precursor solution is applied on the substrate surface by a method such as spinner or printing, and heat-treated at a final temperature of 200 to 400 ° C. to be cured to form a polyimide-based resin film. Resins other than the polyimide resin can be formed according to a known method.

  In the present invention, the elastic modulus of the film means a value measured by an indentation method described below. The indentation method is a method of continuously loading and unloading an indenter on a sample, and quantitatively evaluating characteristics relating to elasto-plastic deformation such as hardness and elastic modulus of the material from the obtained load-mutation curve. In the indentation method, the measurement is carried out by a nano indenter which measures a press-fit depth on the order of 1 nm to 1 μm and a load on the order of 1 μN to 1 mN. Briefly, a square pyramid (Vickers) indenter is pushed into the sample, the press-fit load (P) and press-fit depth (h) are measured, and P and h are changed until the elastic modulus becomes constant (saturated). Then, the elastic modulus is obtained. Specifically, for example, using an ultra-light load thin film hardness tester (Hysitron Inc., Triboscope system + Digital Instruments Nanoscope-III-D3100 attached), press in with an indenter (Berkovic) having a radius of curvature of about 150 nm. Measure at a speed of 100 μN / sec.

Hereinafter, examples of the present invention will be described.
Example 1
A fluorine-containing polyimide resin precursor solution for cladding formation (manufactured by Hitachi Chemical Co., Ltd.) on a silicon wafer substrate having a diameter of about 12.7 cm and a thickness of about 1 mm having a ₂ μm thick SiO ₂ film formed on its surface. (Trade name: OPI-N1005) was dropped and spin coated (1500 rpm / 30 seconds), and then cured in an oven (100 ° C./30 minutes + 200 ° C./30 minutes + 350 ° C./60 minutes) to form a lower cladding layer (film thickness: approx. 10 μm).

Next, Gracia WG-004 (manufactured by Nippon Paint Co., Ltd.) for forming a core was dropped, spin-coated (2000 rpm / 30 seconds), and then cured in an oven (100 ° C./30 minutes + 200 ° C./30 minutes) to form a core layer. (Thickness: about 6.5 μm).
This core layer was exposed to UV through a mask having a core pattern by a xenon-mercury lamp (0.4 mW / cm ² , 60 minutes). Thereafter, post-baking was performed at 100 ° C./30 minutes + 200 ° C./30 minutes + 350 ° C./30 minutes.

  Next, a polyimide-based resin precursor solution containing fluorine (OPI-N1005 manufactured by Hitachi Chemical Co., Ltd.) for forming the upper clad is dropped and spin-coated (1200 rpm / 30 seconds), and then oven (100 ° C.) / 30 minutes + 200 ° C./30 minutes + 350 ° C./60 minutes) to form an upper clad layer (thickness: about 10 μm immediately above the core).

The propagation loss of the obtained optical waveguide was measured by a cutback method, and the measured value was defined as the propagation loss of the optical waveguide film. Specifically, a loss in an optical waveguide having a length of 3 cm, 2 cm, and 1 cm was measured, and a slope of the loss was measured as a propagation loss. As a result, a good propagation loss was obtained.
When the obtained optical waveguide on the substrate was immersed in water (temperature: 100 ° C.) for 30 minutes, the optical waveguide was easily peeled off from the substrate, and an optical waveguide film was obtained.

  In addition, when the elastic modulus of the film was measured by the method and the apparatus described above, a favorable elastic modulus was shown. The measurement conditions are as follows: Using an ultra-light load thin film hardness tester (Hysitron Inc., Triboscope system + Digital Instruments Nanoscope-III-D3100 attached), indentation speed of 100 μN / The measurement was performed in sec.

Example 2
A lower clad layer and a core layer were formed on a silicon wafer substrate in exactly the same manner as in Example 1.
Next, a material for forming an upper clad, Gracia WG-005 (manufactured by Nippon Paint Co., Ltd.), was dropped, and spin coating (1000 rpm / 30 seconds) was performed. ) To form an upper cladding layer (film thickness: about 20 μm).
When the propagation loss of the obtained optical waveguide was measured in the same manner, similarly good propagation loss was obtained.

  Next, the obtained optical waveguide was immersed in water (temperature: 100 ° C.) for 30 minutes, and the optical waveguide was peeled off from the substrate to produce an optical waveguide film. When the elastic modulus of the obtained film was measured in the same manner as in Example 1, it showed a good elastic modulus.

FIG. 2 is a cross-sectional view showing one embodiment of the optical waveguide of the present invention. FIG. 3 is a view showing one embodiment of a method for manufacturing an optical waveguide of the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate 2 ... Lower clad 3 ... Core 4 ... Side clad 5 ... Upper clad

Claims (11)

An optical waveguide comprising a lower clad, a core formed on the lower clad, a side clad formed on the lower clad upper part and the core side part, and an upper clad formed on the core and the side clad; A film, wherein the core is made of a photobleaching material, the side cladding is made of a material whose refractive index is reduced by UV-exposing the photobleaching material, and at least a part of the lower and upper claddings is An optical waveguide film made of a polyimide resin. The optical waveguide film according to claim 1, wherein the photobleaching material is a polysilane. The optical waveguide film according to claim 1, wherein the polyimide resin is a polyimide resin containing fluorine. The fluorine-containing polyimide resin is a fluorine-containing polyimide resin, a fluorine-containing poly (imide / isoindoloquinazolinedionimide) resin, a fluorine-containing polyetherimide resin, a fluorine-containing polyamideimide resin, and two kinds thereof. The optical waveguide film according to claim 3, wherein the optical waveguide film is selected from the group consisting of the above mixture. The optical waveguide film according to any one of claims 1 to 4, wherein the lower clad is made of a polyimide resin, and the upper clad is made of a polysilane. A step of providing a lower clad on the silicon substrate on which the silicon oxide film is formed, a step of providing a core layer made of a photobleaching material on the lower clad, and applying UV to a portion of the core layer other than a portion to be a core. Exposing to form a core and side cladding, and providing an upper cladding on the core and the side cladding, provided that at least a portion of the lower and upper cladding is made of a polyimide resin, A method of producing an optical waveguide film by forming an optical waveguide structure on a silicon substrate by immersing it in water and peeling the optical waveguide structure from the silicon substrate. The manufacturing method according to claim 6, further comprising a step of performing post-baking after a step of exposing a portion other than a portion to be a core to UV exposure and before a step of providing an upper clad. The method according to claim 6 or 7, wherein the photobleaching material is a polysilane. The method according to any one of claims 6 to 8, wherein the polyimide resin is a polyimide resin containing fluorine. The fluorine-containing polyimide resin is a fluorine-containing polyimide resin, a fluorine-containing poly (imide / isoindoloquinazolinedionimide) resin, a fluorine-containing polyetherimide resin, a fluorine-containing polyamideimide resin, and two kinds thereof. The method according to claim 9, wherein the method is selected from the group consisting of the above mixtures. The method according to any one of claims 7 to 10, wherein the lower clad is made of a polyimide resin, and the upper clad is made of polysilanes.

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