Cladding compositions, composition sets, optical waveguides, and electronic devices

Abstract

The present invention provides a cladding composition that can form a cladding layer with an improved balance of heat resistance and high refractive index properties. [Solution] A cladding composition that can be used as cladding for optical waveguides, comprising a solid epoxy resin (A) that is solid at 23°C, wherein when the total amount of resin components in the cladding composition is 100 parts by mass, the content of liquid epoxy resin that is liquid at 23°C is less than 5 parts by mass.

Description

Technical Field

[0001] The present invention relates to a composition for a cladding, a composition set, an optical waveguide, and an electronic device.

Background Art

[0002] In recent years, in information communication devices, there has been a demand for components that can achieve more advanced information communication such as a larger capacity of information and a higher speed of information communication. As one of such components, an optical waveguide has been studied.

[0003] As a technique of an optical waveguide, for example, the technique described in Patent Document 1 can be cited.

[0004] Patent Document 1 describes an optical waveguide formed by laminating a core layer made of a polymer and a cladding layer made of a polymer on a substrate, wherein a cladding layer having a refractive index smaller than that of the cladding layer sandwiching the core layer from a direction parallel to the surface of the substrate sandwiches the core layer from a direction perpendicular to the surface of the substrate. According to the optical waveguide of Patent Document 1, it is described that an optical waveguide with less polarization dependence can be realized even by using a polymer with a large birefringence such as polyimide.

Prior Art Documents

Patent Documents

[0008] [1] A cladding composition that can be used for cladding in optical waveguides, It contains a solid epoxy resin (A) that is solid at 23°C. A cladding composition wherein, when the total amount of resin components in the cladding composition is 100 parts by mass, the content of liquid epoxy resin that is liquid at 23°C is less than 5 parts by mass. [2] The cladding composition according to [1], wherein the solid epoxy resin (A) comprises a novolac-type epoxy resin (A1) and an alicyclic epoxy resin (A2). [3] The cladding composition according to [2], wherein the alicyclic epoxy resin (A2) has three or more epoxy groups in its molecule. [4] The cladding composition according to [2] or [3], wherein the mass ratio of the content of the alicyclic epoxy resin (A2) to the content of the novolac-type epoxy resin (A1) in the cladding composition is 0.3 or more and 2.0 or less. [5] The cladding composition according to any one of [1] to [4], wherein the glass transition temperature calculated from the top peak of tanδ by a thermomechanical analyzer (TMA) of a cured product comprising the cladding composition is 140°C or higher. [6] The cladding composition according to any one of [1] to [5], wherein the refractive index of the cladding composition at 25°C and a wavelength of 1310 nm is 1.45 or more and less than 1.57. [7] The cladding composition according to any one of [1] to [6], wherein the tensile elongation at break of the cladding composition according to the method 1 below is 10% or more and 80% or less. (Method 1) The cladding composition is cured at 170°C for 180 minutes to prepare a test specimen measuring 50 mm × 6.5 mm × 10 μm in thickness. The test specimen is stretched using a tensile testing machine at 23°C at a tensile speed of 5 mm / min in accordance with JIS K 7161:2014, and the elongation at break of the test specimen is measured. [8] The cladding composition according to any one of [1] to [7], wherein the coefficient of linear expansion of a cured product made from the cladding composition is 40 ppm / °C to 100 ppm / °C when measured using a thermomechanical analyzer under the conditions of a temperature range of 10°C to 400°C and a heating rate of 5°C / min, and is measured at 50°C to 100°C. [9] The cladding composition according to any one of [1] to [8], wherein the difference in the coefficient of linear expansion between the cured product made of the cladding composition and silicon at a temperature of 25°C or higher and below the glass transition temperature is 75 ppm / °C or less.

[10] The cladding composition according to any one of [1] to [9], wherein when the total amount of resin components in the cladding composition is 100 parts by mass, the content of the solid epoxy resin (A) is 50 parts by mass or more and 100 parts by mass or less.

[11] A cladding composition according to any one of [1] to

[10] , further comprising phenoxy resin (B).

[12] A cladding composition according to any one of [1] to

[11] , further comprising a photoacid generator (C).

[13] A cladding composition according to any one of [1] to

[12] , further comprising a surfactant (D).

[14] A cladding composition according to any one of [1] to

[13] , further comprising a silane coupling agent (E).

[15] A cladding composition according to any one of [1] to

[14] , further comprising an organic solvent (F).

[16] The clad composition according to any one of [1] to

[15] , wherein when the total amount of the resin component in the clad composition is 100 parts by mass, the amount of fluorine atoms contained in the resin component is less than 1 part by mass.

[17] The clad composition according to any one of [1] to

[16] , which is in a varnish form.

[18] A composition set comprising the clad composition according to any one of [1] to

[17] , and a core composition that can be used for the core of an optical waveguide.

[19] An optical waveguide comprising a clad made of the clad composition according to any one of [1] to

[17] .

[20] Comprising a silicon photonics device, The silicon photonics device comprises the optical waveguide according to

[19] , an electronic device. [Effect of the Invention]

[0009] According to the present invention, a clad composition with an improved balance of heat resistance and high refractive index performance can be provided. [Brief Description of the Drawings] [[ID=३३]]

[0010] [Figure 1] It is a cross-sectional view schematically showing an example of the structure of the optical waveguide of the present embodiment. [Modes for Carrying Out the Invention]

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings are schematic diagrams and do not match the actual dimensional ratios. The numerical range "A to B" represents A or more and B or less unless otherwise specified. (Meth)acrylate is a concept that includes both acrylate and methacrylate. Also, the (meth)acryloyl group is a concept that includes both the acryloyl group and the methacryloyl group.

[0012] Optical waveguides may be formed on a chip (for example, a silicon chip). Since chips can generate heat, heat resistance may be required for optical waveguides formed on chips.

[0013] This invention provides a cladding composition that offers an improved balance between heat resistance and high refractive index.

[0014] [Composition for cladding] The cladding composition of this embodiment is a cladding composition that can be used for cladding optical waveguides, and contains a solid epoxy resin (A) that is solid at 23°C, and when the total amount of resin components in the cladding composition is 100 parts by mass, the content of liquid epoxy resin that is liquid at 23°C is less than 5 parts by mass.

[0015] When the total amount of resin components in the cladding composition is 100 parts by mass, from the viewpoint of further improving the balance between the heat resistance and high refractive index performance of the cladding composition, the content of liquid epoxy resin that is liquid at 23°C is preferably 0 parts by mass or more and 3 parts by mass or less, more preferably 0 parts by mass or more and 2 parts by mass or less, even more preferably 0 parts by mass or more and 1 part by mass or less, even more preferably 0.5 parts by mass or less, and even more preferably 0.1 parts by mass or less.

[0016] The refractive index of the cladding composition of this embodiment at 25°C and a wavelength of 1310 nm is preferably 1.45 or more and less than 1.57, more preferably 1.50 or more and 1.56 or less, and even more preferably 1.52 or more and 1.56 or less, from the viewpoint of further improving the optical propagation efficiency of the optical waveguide.

[0017] The glass transition temperature calculated from the top peak of tanδ by thermomechanical analysis (TMA) of the cured product made from the cladding composition of this embodiment is preferably 140°C or higher, more preferably 150°C or higher, and even more preferably 160°C or higher, from the viewpoint of further improving the heat resistance of the optical waveguide, and preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower, from the viewpoint of further improving the flexibility of the optical waveguide.

[0018] The tensile elongation at break of the cladding composition of this embodiment, obtained by Method 1 below, is 10% to 80%, more preferably 13% to 70%, even more preferably 15% to 60%, even more preferably 20% to 50%, even more preferably 23% to 40%, and even more preferably 25% to 35%, from the viewpoint of further improving the balance of heat resistance, high refractive index, and flexibility of the cladding composition. (Method 1) The cladding composition is cured at 170°C for 180 minutes to prepare a test specimen measuring 50 mm × 6.5 mm × 10 μm in thickness. The test specimen is stretched using a tensile testing machine at 23°C at a tensile speed of 5 mm / min in accordance with JIS K 7161:2014, and the elongation at break of the test specimen is measured.

[0019] When the cured product made from the cladding composition of this embodiment is measured using a thermomechanical analyzer under the conditions of a temperature range of 10°C to 400°C and a heating rate of 5°C / min, the coefficient of linear expansion at 50°C to 100°C is preferably 40 ppm / °C to 100 ppm / °C, more preferably 45 ppm / °C to 90 ppm / °C, even more preferably 50 ppm / °C to 80 ppm / °C, and even more preferably 55 ppm / °C to less than 75 ppm / °C, from the viewpoint of further improving the balance of performance of the cladding composition in terms of heat resistance, high refractive index, and thermal reliability.

[0020] The difference in the coefficient of linear expansion between the cured product made from the cladding composition of this embodiment and silicon at temperatures above 25°C and below the glass transition temperature is preferably 75 ppm / °C or less, more preferably 73 ppm / °C or less, even more preferably 72 ppm / °C or less, and preferably 50 ppm / °C or more, more preferably 60 ppm / °C or more, even more preferably 63 ppm / °C or more, and even more preferably 67 ppm / °C or more.

[0021] The shape of the cladding composition in this embodiment is not particularly limited and may be, for example, varnish-like, film-like, or sheet-like, but varnish-like.

[0022] The following describes each component of the cladding composition of this embodiment.

[0023] <Solid epoxy resin (A)> The cladding composition of this embodiment includes a solid epoxy resin (A). The solid epoxy resin (A) is solid at 23°C. This improves the balance between heat resistance and high refractive index performance of the cladding composition.

[0024] The content of the solid epoxy resin (A) in the cladding composition of this embodiment is preferably 50 parts by mass or more and 100 parts by mass or less, more preferably 60 parts by mass or more and 90 parts by mass or less, and even more preferably 70 parts by mass or more and 80 parts by mass or less, when the total amount of resin components in the cladding composition is 100 parts by mass.

[0025] From the viewpoint of improving the balance between heat resistance and high refractive index performance of the cladding composition, the solid epoxy resin (A) preferably uses an epoxy resin having two or more epoxy groups per molecule. Furthermore, the solid epoxy resin (A) can be a monomer, oligomer, or polymer in general.

[0026] The solid epoxy resin (A) includes, for example, one or more selected from the group consisting of novolac-type epoxy resin (A1), cresol naphthol-type epoxy resin, biphenyl-type epoxy resin, biphenyl aralkyl-type epoxy resin, naphthalene skeleton-type epoxy resin, bisphenol A-type epoxy resin, bisphenol A diglycidyl ether-type epoxy resin, bisphenol F-type epoxy resin, bisphenol F diglycidyl ether-type epoxy resin, bisphenol S diglycidyl ether-type epoxy resin, glycidyl ether-type epoxy resin, aromatic epoxy resin, aliphatic epoxy resin, and alicyclic epoxy resin (A2).

[0027] The solid epoxy resin (A) preferably comprises a novolac-type epoxy resin (A1) and an alicyclic epoxy resin (A2) from the viewpoint of further improving the balance between the heat resistance and high refractive index performance of the cladding composition.

[0028] (Novolac-type epoxy resin (A1)) The novolac-type epoxy resin (A1) includes, for example, one or more selected from the group consisting of phenol novolac-type epoxy resins and cresol novolac-type epoxy resins, and preferably includes a phenol novolac-type epoxy resin from the viewpoint of further improving the balance between the heat resistance and high refractive index performance of the cladding composition.

[0029] The novolac-type epoxy resin (A1) preferably contains a solid epoxy resin having two or more, preferably three or more, and more preferably five or more epoxy groups in its molecule. This allows for a better balance between the heat resistance and high refractive index performance of the cladding composition.

[0030] The novolac-type epoxy resin (A1) has a structure represented by the following general formula (1), for example.

[0031] [ka] In general formula (1), R is independently either a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is an integer from 1 to 20. In general formula (1), R is preferably a hydrogen atom or a C1-C4 alkyl group, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom, from the viewpoint of further improving the balance between the heat resistance and high refractive index performance of the cladding composition of this embodiment. In general formula (1), n ​​is preferably an integer from 1 to 15, more preferably an integer from 2 to 10, and even more preferably an integer from 3 to 8, from the viewpoint of further improving the balance between the heat resistance and high refractive index performance of the cladding composition of this embodiment.

[0032] The content of novolac-type epoxy resin (A1) in the cladding composition of this embodiment is preferably 15 parts by mass or more and 75 parts by mass or less, more preferably 20 parts by mass or more and 70 parts by mass or less, even more preferably 25 parts by mass or more and 65 parts by mass or less, and even more preferably 25 parts by mass or more and 60 parts by mass or less, when the total amount of resin components in the cladding composition is 100 parts by mass.

[0033] The novolac-type epoxy resin (A1) of the cladding composition in this embodiment is preferably solid at 23°C.

[0034] (Alicyclic epoxy resin (A2)) From the viewpoint of further improving the balance between heat resistance and high refractive index performance of cladding compositions, the alicyclic epoxy resin (A2) preferably contains three or more epoxy groups in its molecule, and more preferably contains three epoxy groups in its molecule.

[0035] The alicyclic epoxy resin (A2) has a structure represented by, for example, the following general formula (2).

[0036] [ka] In general formula (2), R1 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R2 to R4 are each independently an alkylene group having 1 to 4 carbon atoms, and n1 to n3 are each independently an integer from 1 to 5. In general formula (2), R1 is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably an ethyl group, from the viewpoint of further improving the balance between the heat resistance and high refractive index performance of the cladding composition of this embodiment. In general formula (2), R2 to R4 are, from the viewpoint of further improving the balance between heat resistance and high refractive index performance of the cladding composition of this embodiment, preferably alkylene groups having 1 to 3 carbon atoms, more preferably alkylene groups having 1 to 2 carbon atoms, and even more preferably methylene groups. In general formula (2), n1 to n3 are, from the viewpoint of further improving the balance between heat resistance and high refractive index performance of the cladding composition of this embodiment, preferably integers from 1 to 3, more preferably integers from 1 to 2, and even more preferably 1.

[0037] The content of alicyclic epoxy resin (A2) in the cladding composition of this embodiment is preferably 10 parts by mass or more and 70 parts by mass or less, more preferably 15 parts by mass or more and 65 parts by mass or less, and even more preferably 20 parts by mass or more and 60 parts by mass or less, when the total amount of resin components in the cladding composition is 100 parts by mass.

[0038] The mass ratio of the alicyclic epoxy resin (A2) content to the novolac-type epoxy resin (A1) content in the cladding composition of this embodiment is preferably 0.3 to 2.0, more preferably 0.35 to 1.75, and even more preferably 0.40 to 1.6.

[0039] The alicyclic epoxy resin (A2) in the cladding composition of this embodiment is solid at 23°C. This improves the heat resistance of the cladding composition.

[0040] <Phenoxy resin (B)> The cladding composition of this embodiment preferably further comprises phenoxy resin (B).

[0041] The weight-average molecular weight of the phenoxy resin (B) is not particularly limited, but is preferably 10,000 to 100,000, and more preferably 20,000 to 80,000. By using such a relatively high molecular weight phenoxy resin, good flexibility can be imparted to the resin film, as well as sufficient solubility in the solvent.

[0042] In this embodiment, the weight-average molecular weight is measured, for example, as a polystyrene-converted value by gel permeation chromatography (GPC).

[0043] Furthermore, the phenoxy resin (B) may have reactive groups such as epoxy groups at both ends of the molecular chain or within the molecular chain. The reactive groups in the phenoxy resin are capable of crosslinking with the epoxy groups in the epoxy resin. By using such a phenoxy resin, the balance between the heat resistance and high refractive index performance of the cladding composition can be further improved.

[0044] Furthermore, the phenoxy resin (B) is preferably solid at 23°C. Specifically, a phenoxy resin with a non-volatile content of 90% by mass or more is more preferable. By using such a phenoxy resin, the mechanical properties of the cured product can be improved.

[0045] The phenoxy resin (B) includes, for example, one or more selected from the group consisting of bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, copolymer phenoxy resin of bisphenol A type and bisphenol F type, biphenyl type phenoxy resin, bisphenol S type phenoxy resin, and copolymer phenoxy resin of biphenyl type phenoxy resin and bisphenol S type phenoxy resin, and more preferably one or more selected from the group consisting of bisphenol A type phenoxy resin and copolymer phenoxy resin of bisphenol A type and bisphenol F type.

[0046] The lower limit of the phenoxy resin (B) content is, for example, 5 parts by mass or more, preferably 8 parts by mass or more, and more preferably 10 parts by mass or more, when the total amount of solid epoxy resin (A) in the cladding composition of this embodiment is 100 parts by mass. This can increase the flexibility of the resulting cladding. On the other hand, the upper limit of the phenoxy resin (B) content is, for example, 60 parts by mass or less, preferably 55 parts by mass or less, and more preferably 50 parts by mass or less. This can increase the solubility of the phenoxy resin (B) and improve the coatability of the cladding composition.

[0047] <Photoacid Generator (C)> The cladding composition of this embodiment preferably further comprises a photoacid generator (C).

[0048] Examples of photoacid generators (C) include onium salt compounds, and more specifically, iodonium salts such as diazonium salts and diaryliodonium salts, sulfonium salts such as triarylsulfonium salts, cationic photopolymerization initiators such as triarylpyrylium salts, benzylpyridinium thiocyanate, dialkylphenacylsulfonium salts, and dialkylhydroxyphenylphosphonium salts. Suitable counter anions for the above onium salt compounds include borate anions, sulfonate anions, gallate anions, phosphorus anions, and antimony anions.

[0049] The amount of photoacid generator (C) in the cladding composition of this embodiment is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 4.5 parts by mass or less, and even more preferably 1.0 part by mass or more and 4.0 parts by mass or less, when the total amount of resin components in the cladding composition is 100 parts by mass.

[0050] <Surfactant (D)> The cladding composition of this embodiment preferably further comprises a surfactant (D). By including a surfactant (D) in the cladding composition, the coatability of the composition can be further improved, and the flatness of the coating film made from the composition can be further improved.

[0051] The surfactant (D) includes, for example, at least one selected from the group consisting of fluorine-based surfactants, silicone-based surfactants, alkyl-based surfactants, and acrylic-based surfactants, and preferably includes a silicone-based surfactant.

[0052] The amount of surfactant (D) in the cladding composition of this embodiment is preferably 0.001 parts by mass or more and 1.0 part by mass or less, more preferably 0.003 parts by mass or more and 0.50 parts by mass or less, even more preferably 0.005 parts by mass or more and 0.10 parts by mass or less, even more preferably 0.008 parts by mass or more and 0.050 parts by mass or less, and even more preferably 0.010 parts by mass or more and 0.030 parts by mass or less, when the total amount of resin components in the cladding composition is 100 parts by mass.

[0053] <Silane coupling agent (E)> The cladding composition of this embodiment preferably further comprises a silane coupling agent (E). By including a silane coupling agent (E) in the cladding composition, for example, the adhesion between the cured product made from the composition and adjacent layers can be further improved.

[0054] The silane coupling agent (E) includes, for example, at least one selected from the group consisting of silane coupling agents having a cyclic anhydride structure, amino group-containing silane coupling agents, epoxy group-containing silane coupling agents, (meth)acryloyl group-containing silane coupling agents, mercapto group-containing silane coupling agents, vinyl group-containing silane coupling agents, ureido group-containing silane coupling agents, and sulfide group-containing silane coupling agents, and preferably includes a silane coupling agent having a cyclic anhydride structure.

[0055] The content of the silane coupling agent (E) in the cladding composition of this embodiment is preferably 0.10 parts by mass or more and 5.0 parts by mass or less, more preferably 0.20 parts by mass or more and 3.0 parts by mass or less, even more preferably 0.30 parts by mass or more and 2.0 parts by mass or less, even more preferably 0.40 parts by mass or more and 1.5 parts by mass or less, and even more preferably 0.50 parts by mass or more and 1.3 parts by mass or less, when the total amount of resin components in the cladding composition is 100 parts by mass.

[0056] <Organic solvent (F)> The cladding composition of this embodiment preferably further comprises an organic solvent (F). When the cladding composition contains an organic solvent (F), a varnish-like cladding composition is obtained.

[0057] Examples of organic solvents (F) include acetone, methyl ethyl ketone, toluene, propylene glycol methyl ethyl ether, propylene glycol dimethyl ether, propylene glycol 1-monomethyl ether 2-acetate, diethylene glycol ethyl methyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, benzyl alcohol, propylene carbonate, ethylene glycol diacetate, propylene glycol diacetate, propylene glycol monomethyl ether acetate, dipropylene glycol methyl-n-propyl ether, butyl acetate, and γ-butyrolactone. These may be used individually or in combination, and propylene glycol methyl ethyl ether is preferably used.

[0058] The content of the organic solvent (F) in the cladding composition of this embodiment is preferably 70 parts by mass or more and 300 parts by mass or less, more preferably 80 parts by mass or more and 250 parts by mass or less, and even more preferably 90 parts by mass or more and 200 parts by mass or less, when the total amount of resin components in the cladding composition is 100 parts by mass.

[0059] <Other ingredients> The cladding composition of this embodiment may further contain other components. Other components include, for example, water, polymerization inhibitors, sensitizers, fillers such as silica, and film-forming agents. The amount of these other components is appropriate. Furthermore, when the total amount of resin components in the cladding composition of this embodiment is 100 parts by mass, the amount of fluorine atoms contained in the resin components is preferably less than 1 part by mass, more preferably 0.5 parts by mass or less, even more preferably 0.3 parts by mass or less, even more preferably 0.1 parts by mass or less, and even more preferably 0 parts by mass, from the viewpoint of reducing environmental impact.

[0060] [Composition Set] The composition set of this embodiment includes the cladding composition of this embodiment and the core composition that can be used in the core of an optical waveguide.

[0061] The core composition of this embodiment is not particularly limited as long as it is a composition that can be used as the core of an optical waveguide, and may be, for example, a resin composition containing a resin used for the core of a known optical waveguide.

[0062] The shape of the core composition in this embodiment is not particularly limited and may be, for example, varnish-like, film-like, film-like, or sheet-like, but varnish-like is preferred.

[0063] The core composition of this embodiment preferably includes one or more selected from the group consisting of epoxy resins and phenoxy resins, from the viewpoint of improving the dimensional stability and optical propagation efficiency of the optical waveguide. When the total amount of resin components in the core composition of this embodiment is 100 parts by mass, the epoxy resin content is preferably 50 parts by mass or more and 100 parts by mass or less, more preferably 60 parts by mass or more and 90 parts by mass or less, and even more preferably 70 parts by mass or more and 80 parts by mass or less. When the total amount of resin components in the core composition of this embodiment is 100 parts by mass, the phenoxy resin content is preferably 5 parts by mass or more and less than 50 parts by mass, more preferably 10 parts by mass or more and 45 parts by mass or less, and even more preferably 15 parts by mass or more and 40 parts by mass or less, from the viewpoint of improving the dimensional stability of the optical waveguide.

[0064] The epoxy resin included in the core composition of this embodiment is not particularly limited, but preferably includes a solid epoxy resin. Examples include phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, dicyclopentadiene type epoxy resin, bisphenol A type epoxy resin, and tetramethylbisphenol F type epoxy resin, and one or more of these can be used. From the viewpoint of improving the dimensional stability of the optical waveguide, it is preferable to use the same type of solid epoxy resin (A) as included in the cladding composition of this embodiment.

[0065] The phenoxy resin included in the core composition of this embodiment is not particularly limited, but examples include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, copolymer phenoxy resin of bisphenol A type and bisphenol F type, biphenyl type phenoxy resin, bisphenol S type phenoxy resin, copolymer phenoxy resin of biphenyl type phenoxy resin and bisphenol S type phenoxy resin, and one or more of these can be used.

[0066] [Optical waveguide] The optical waveguide of this embodiment comprises a cladding made of the cladding composition of this embodiment.

[0067] Figure 1 is a schematic cross-sectional view showing an example of the structure of an optical waveguide according to this embodiment. An example of an optical waveguide according to this embodiment will be explained using Figure 1. In Figure 1, the optical waveguide 100 is formed on the wafer 50. The optical waveguide 100 comprises an undercladding 10, a core 20, and an overcladding 30.

[0068] <core> The material constituting the core 20 is not particularly limited; for example, a known material used to form the cladding of an optical waveguide can be used, and it may be an organic material or an inorganic material. The core 20 is preferably made of the core composition of this embodiment. The core composition forming the core 20 may be a cured product, a semi-cured product, or an uncured product, but is preferably a cured product.

[0069] The thickness and line width of the core 20 are not particularly limited, but are preferably dimensions that satisfy the single-mode condition. The single-mode conditions depend on the difference in relative refractive index between the core and cladding, as well as the waveguide wavelength. However, the thickness and linewidth of the core 20 are preferably 1 μm to 11 μm, and more preferably 2 μm to 10 μm.

[0070] <Clad> This section describes underclad 10 and overclad 30. Hereafter, when simply referred to as "clad," unless otherwise specified, it encompasses both underclad 10 and overclad 30.

[0071] At least one of the underclad 10 and the overclad 30 is made of the clad composition of this embodiment.

[0072] The cladding composition that forms the cladding may be a cured product, a semi-cured product, or an uncured product, but is preferably a cured product.

[0073] The underclad 10 and the overclad 30 may be made of the same material or of different materials.

[0074] The thickness of the underclad 10 is not particularly limited, but is preferably 1 μm to 25 μm, more preferably 3 μm to 20 μm, and even more preferably 5 μm to 15 μm. The thickness of the overclad 30 from the surface of the underclad 10 is not particularly limited, but is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, and even more preferably 10 μm to 30 μm. The thickness of the overclad 30 from the surface of the core 20 is not particularly limited, but is preferably 1 μm to 25 μm, more preferably 3 μm to 20 μm, and even more preferably 5 μm to 15 μm.

[0075] The optical waveguide 100 may further comprise components other than the undercladding 10, core 20, and overcladding 30.

[0076] The method for manufacturing the optical waveguide 100 is not particularly limited, but for example, it may include the following steps (i) to (iii). (i) A varnish-like cladding composition is applied to the wafer 50 and dried to form an undercladding layer, and the obtained undercladding layer is cured to form the undercladding 10. (ii) A varnish-like core composition is applied to the underclad 10, dried to form a core layer, and the core 20 is formed by curing the resulting core layer. (iii) A varnish-like cladding composition is applied to the core 20 and dried to form an overcladding layer, and the obtained overcladding layer is cured to form the overcladding 30. The method for applying the varnish-like composition is not particularly limited, but for example, a spin coating method can be used.

[0077] [Electronic equipment] The electronic device of this embodiment includes the optical waveguide of this embodiment, preferably a silicon photonic device, and the silicon photonic device includes the optical waveguide of this embodiment. Here, silicon photonics is a technology that integrates elements such as optical waveguides, optical switches, optical modulators, and photodetectors onto a silicon wafer, and a silicon photonics device refers to a device that utilizes silicon photonics technology.

[0078] A silicon photonics device is, for example, a device in which an optical waveguide 100 is formed on a wafer 50, as shown in Figure 1. In this case, the wafer 50 is a silicon wafer. The silicon photonics device may further include, for example, a silicon nanowire waveguide.

[0079] Examples of electronic devices in this embodiment include mobile phones, game consoles, routers, WDM devices, personal computers, televisions, home servers, and other electronic devices.

[0080] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. Furthermore, the present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0081] The embodiment will be described in detail below based on examples and comparative examples. However, this embodiment is not limited in any way to the descriptions of these examples.

[0082] [Raw materials] <Epoxy resin (A)> (A-1) EPPN201 (manufactured by Nippon Kayaku Co., Ltd., phenol novolac type epoxy resin, polyfunctional solid epoxy resin, solid at 23°C, n=5) [ka]

[0083] (A-2) EHPE3150 (manufactured by Daicel Corporation, solid at 23°C, alicyclic solid epoxy resin) [ka]

[0084] (A-3) Epolid GT-401 (manufactured by Daicel Corporation, liquid at 23°C, alicyclic liquid epoxy resin) [ka]

[0085] (A-4) Celoxide 2021P (manufactured by Daicel Corporation, liquid at 23°C, alicyclic liquid epoxy resin) [ka]

[0086] <Phenoxy resin (B)> (B-1) jER1256 (manufactured by Mitsubishi Chemical Corporation, Mw: 50,000, bisphenol A type solid phenoxy resin)

[0087] <Photoacid Generator (C)> (C-1) CPI-310B (manufactured by Sunapro, an onium salt compound)

[0088] <Surfactant (D)> (D-1) BYK-333 (manufactured by BYK, silicone-based surfactant)

[0089] <Silane coupling agent (E)> (E-1)X-12-967C (manufactured by Shin-Etsu Chemical Co., Ltd., 3-trimethoxysilylpropyl succinic anhydride, a silane coupling agent having a cyclic anhydride structure)

[0090] <Organic solvent (F)> (F-1)PGMEA (Propylene glycol monomethyl ether acetate)

[0091] [Examples 1-3, Comparative Examples 1-2] Each raw material, formulated according to Table 1, was stirred at room temperature until completely dissolved to obtain a solution. The solution was then filtered through a 0.2 μm pore polypropylene filter to obtain the varnish-like cladding compositions of Examples 1-3 and Comparative Examples 1-2. Hereinafter, the compositions of Examples 1-3 will also be referred to as compositions A-C, and the compositions of Comparative Examples 1-2 will be referred to as compositions D-E.

[0092] [Reference example 1] Each raw material, formulated according to Table 1, was stirred at room temperature until completely dissolved to obtain a solution. The solution was then filtered through a 0.2 μm pore size polypropylene filter to obtain the varnish-like core composition of Reference Example 1. Hereinafter, the composition of Reference Example 1 will also be referred to as Composition F.

[0093] [Example 4] <Manufacturing of optical waveguides> (Underclad formation) A liquid film obtained by spin-coating composition A onto an 8-inch silicon wafer was heated at 100°C for 3 minutes to dry and form a 10 μm thick undercladding layer. Next, the obtained undercladding layer was exposed to a 365 nm i-line at 600 mJ / cm using an automated exposure machine. 2 The entire surface was exposed to light at the specified exposure level and heated on a hot plate at 70°C for 5 minutes in air. Next, the undercladding was formed by heating in a nitrogen atmosphere at 170°C for 180 minutes.

[0094] (Core formation) Composition F was spin-coated onto the undercladding to obtain a liquid coating. The resulting coating was then heated at 100°C for 3 minutes to dry and form a core layer with a thickness of 7 μm. Next, the obtained core layer was exposed to a 365nm i-line at 600mJ / cm using an automated exposure machine. 2 The sample was exposed to light, heated on a hot plate at 70°C for 5 minutes in air, and then immersed in PGMEA for 20 seconds. Next, it was heated at 170°C for 180 minutes in a nitrogen atmosphere to form a core with a line width of 10 μm.

[0095] (Overcladding) Composition A was spin-coated onto the core to obtain a liquid coating. The resulting coating was then heated at 100°C for 3 minutes to dry, forming an overcladding layer with a thickness of 17 μm. Next, the obtained overcladding layer was exposed to a 365 nm i-line at 600 mJ / cm using an automated exposure machine. 2The entire surface was exposed to light at the specified exposure level and heated on a hot plate at 70°C for 5 minutes in air. Next, the overcladding was formed by heating at 170°C for 180 minutes in a nitrogen atmosphere.

[0096] [Examples 5-6, Comparative Examples 3-4, Reference Example 2] Optical waveguides were fabricated in the same manner as in Example 4, except that the compositions used for the core and cladding were changed according to Table 2.

[0097] [Evaluation and Measurement] <Measuring the refractive index of the composition> The refractive index of the compositions in Examples 1-3, Comparative Examples 1-2, and Reference Example 1 was measured using a prism coupler (manufactured by Metricon) under the following conditions. The refractive index at 25°C and a wavelength of 1310 nm was calculated from the refractive index values ​​at the three measurement wavelengths listed below using Cauchy's dispersion formula. The refractive index at 25°C and a wavelength of 1310 nm for each example is shown in Table 1. Substrate: Si wafer Film thickness: 5 μm Measurement temperature: 25℃ Measurement wavelength: 404nm, 633nm, 832nm

[0098] <Measurement of linear thermal expansion coefficient and glass transition temperature of the composition> The glass transition temperatures of the cured products obtained from the compositions of Examples 1-3, Comparative Examples 1-2, and Reference Example 1 were measured as follows. First, the compositions of Examples 1-3, Comparative Examples 1-2, and Reference Example 1 were cured at 170°C for 180 minutes to prepare test specimens measuring 50 mm × 6.5 mm × 10 μm in thickness. Next, the obtained test specimens were post-cured at 175°C for 4 hours, and then measurements were performed using a thermomechanical analyzer (TMA100, manufactured by Seiko Electronics Industries, Ltd.) under the conditions of a measurement temperature range of 10°C to 400°C and a heating rate of 5°C / min. From these measurement results, the glass transition temperature and the coefficient of linear expansion (α1) in the measurement temperature range of 50°C to 100°C were calculated. The results are shown in Table 1.

[0099] <Measurement of tensile elongation at break of composition> The compositions of Examples 1-3, Comparative Examples 1-2, and Reference Example 1 were cured at 170°C for 180 minutes to prepare test specimens measuring 50 mm × 6.5 mm × 10 μm in thickness. For each test specimen, the tensile elongation at break was measured using a tensile testing machine (STB-1225S, manufactured by A&D Company, Limited) at a temperature of 23°C and in accordance with JIS K 7161:2014, at a tensile speed of 5 mm / min. The results are shown in Table 1.

[0100] <Evaluation of propagation loss in optical waveguides> (Environmental testing) The optical waveguides fabricated in Examples 4-6 and Comparative Examples 3-4 were subjected to environmental testing by heating them in an oven under conditions of 85°C, 85% RH humidity, and 1000 hours, and the optical waveguides after the environmental testing were obtained.

[0101] (Propagation loss evaluation) The propagation loss was measured using the cutback method for both the optical waveguide before and after environmental testing. Specifically, the propagation loss was measured using the following procedure. A laser beam with a wavelength of 1310 nm was incident on the core of the test specimen via a single-mode optical fiber. The propagation loss per unit length of the optical waveguide was calculated by obtaining the intensity of the light emitted from the core of the test specimen while varying the length of the specimen. The propagation loss of the optical waveguide was evaluated based on the following evaluation criteria. Table 2 shows the propagation loss results before and after the environmental test.

[0102] [Table 1]

[0103] [Table 2]

[0104] Table 1 shows that all cladding compositions in the examples exhibited an improved balance of heat resistance and high refractive index performance. Furthermore, Table 2 shows that all optical waveguides in the examples showed good results in propagation loss evaluation. In other words, it can be understood that it is possible to obtain optical waveguides with improved thermal reliability using the cladding compositions of this embodiment. [Explanation of symbols]

[0105] 10 Underclad 20 cores 30 Overclad 50 wafers 100 optical waveguide

Claims

1. A cladding composition that can be used for cladding in optical waveguides, It contains a solid epoxy resin (A) that is solid at 23°C. A cladding composition wherein, when the total amount of resin components in the cladding composition is 100 parts by mass, the content of liquid epoxy resin that is liquid at 23°C is less than 5 parts by mass.

2. The cladding composition according to claim 1, wherein the solid epoxy resin (A) comprises a novolac-type epoxy resin (A1) and an alicyclic epoxy resin (A2).

3. The cladding composition according to claim 2, wherein the alicyclic epoxy resin (A2) has three or more epoxy groups in its molecule.

4. The cladding composition according to claim 2 or 3, wherein the mass ratio of the content of the alicyclic epoxy resin (A2) to the content of the novolac-type epoxy resin (A1) in the cladding composition is 0.3 or more and 2.0 or less.

5. The cladding composition according to claim 1 or 2, wherein the glass transition temperature calculated from the top peak of tanδ by thermomechanical analysis (TMA) of a cured product made from the cladding composition is 140°C or higher.

6. The cladding composition according to claim 1 or 2, wherein the refractive index of the cladding composition at 25°C and a wavelength of 1310 nm is 1.45 or more and less than 1.

57.

7. The cladding composition according to claim 1 or 2, wherein the tensile elongation at break of the cladding composition by the following method 1 is 10% or more and 80% or less. (Method 1) The cladding composition is cured at 170°C for 180 minutes to prepare a test specimen measuring 50 mm × 6.5 mm × 10 μm in thickness. The test specimen is stretched at a tensile speed of 5 mm / min at a temperature of 23°C using a tensile testing machine, in accordance with JIS K 7161:2014, and the elongation at break of the test specimen is measured.

8. The cladding composition according to claim 1 or 2, wherein the coefficient of linear expansion of a cured product made from the cladding composition is 40 ppm / °C or more and 100 ppm / °C or less, when measured using a thermomechanical analyzer under the conditions of a temperature range of 10°C or more and 400°C or less and a heating rate of 5°C / min, at a temperature of 50°C or more and 100 ppm / °C or less.

9. The cladding composition according to claim 1 or 2, wherein the difference in the coefficient of linear expansion between the cured product made from the cladding composition and silicon at a temperature of 25°C or higher and below the glass transition temperature is 75 ppm / °C or less.

10. The cladding composition according to claim 1 or 2, wherein when the total amount of resin components in the cladding composition is 100 parts by mass, the content of the solid epoxy resin (A) is 50 parts by mass or more and 100 parts by mass or less.

11. The cladding composition according to claim 1 or 2, further comprising phenoxy resin (B).

12. The cladding composition according to claim 1 or 2, further comprising a photoacid generator (C).

13. The cladding composition according to claim 1 or 2, further comprising a surfactant (D).

14. The cladding composition according to claim 1 or 2, further comprising a silane coupling agent (E).

15. The cladding composition according to claim 1 or 2, further comprising an organic solvent (F).

16. The cladding composition according to claim 1 or 2, wherein when the total amount of resin components in the cladding composition is 100 parts by mass, the amount of fluorine atoms contained in the resin components is less than 1 part by mass.

17. The cladding composition according to claim 1 or 2, which is varnish-like.

18. A cladding composition according to claim 1 or 2, A composition set comprising a core composition that can be used in the core of an optical waveguide.

19. An optical waveguide comprising a cladding made of the cladding composition according to claim 1 or 2.

20. Equipped with silicon photonics devices, The silicon photonic device is an electronic device comprising an optical waveguide as described in claim 19.

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