Laminate for photoelectric fusion substrate and photoelectric fusion substrate

Abstract

The purpose of the present disclosure is to provide a laminate for a photoelectric fusion substrate, the laminate having excellent heat resistance, adhesion properties, and productivity and enabling the fusion of optical waveguides while reducing deterioration of an electronic substrate. The present invention is a laminate (100) for a photoelectric fusion substrate. The laminate has, in order, a core layer (10) that has an average thickness of 1 μm to 10 μm and is formed from a heat-resistant resin having a refractive index n1 with respect to light having a wavelength of 1310 nm or 1550 nm; an under-cladding layer (21) that has an average thickness of 5 µm to 25 µm and is formed from a heat-resistant resin having a refractive index n2 with respect to light having a wavelength of 1310 nm or 1550 nm; and an insulating adhesive layer (30) that has an average thickness of 10 µm to 200 µm and is formed from a thermosetting resin composition. The insulating adhesive layer (30) has a volume resistivity after curing of at least 108 Ω·cm. Refractive indices n1 and n2 satisfy the relationship of 0.1 < 100 x (n1-n2) / n1 < 5.

Description

Laminate for photoelectric fusion substrates, and photoelectric fusion substrates

[0001] This disclosure relates to a laminate for photoelectric fusion substrates and to photoelectric fusion substrates.

[0002] To realize next-generation optoelectronic integration technology, optoelectronic integration substrates are being developed that integrate optical waveguides, which enable high-speed transmission, high-capacity communication, and low power consumption, with electronic substrates such as semiconductor substrates. For this to work, it is important to perform the lamination of optical waveguides and electronic substrates, the formation of electrical wiring, and the lamination and optical bonding of optical waveguides and / or photoelectric conversion elements with high precision, and for example, heat resistance is required.

[0003] To date, fluorinated polyimides have been known to be useful as core materials due to their low transmission loss at wavelengths of 1310 nm or 1550 nm and their high heat resistance. Specifically, with the aim of providing a plastic material for optical communications that has heat resistance and low optical loss across the entire optical communication wavelength range of 1.0 to 1.7 μm, for example, a fully fluorinated polyimide having repeating units imidized with a fully fluorinated acid anhydride, 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride (10FDEA), and a fully fluorinated diamine has been reported (see, for example, Patent Document 1).

[0004] Japanese Patent Application Publication No. 5-001148

[0005] The present disclosure aims to provide a laminate for photoelectric fusion substrates that can fuse optical waveguides while reducing degradation of the electronic substrate, and that is excellent in heat resistance, adhesion, and productivity.

[0006] <1> A core layer made of a heat-resistant resin with an average thickness of 1 μm or more and a refractive index n1 at a wavelength of 1310 nm or 1550 nm; an underclad layer made of a heat-resistant resin with an average thickness of 5 μm or more and a refractive index n2 at a wavelength of 1310 nm or 1550 nm; and an insulating adhesive layer made of a thermosetting resin composition with an average thickness of 10 μm or more and a refractive index n2 at a wavelength of 1310 nm or 1550 nm, in this order, wherein the volume resistivity of the insulating adhesive layer after curing is 10 ８A laminate for a photoelectric fusion substrate characterized in that the refractive index is Ω·cm or more, and the refractive indices n1 and n2 satisfy the relationship: 0.1 < 100 × (n1 - n2) / n1 < 5. <2> The laminate for a photoelectric fusion substrate according to <1>, further comprising a heat-resistant resin layer between the underclad layer and the insulating adhesive layer, the heat-resistant resin having an average thickness of 15 μm or more and a glass transition temperature of 150°C or more. <3> The laminate for a photoelectric fusion substrate according to <2>, wherein the heat-resistant resin layer is made of polyimide resin. <4> The laminate for a photoelectric fusion substrate according to any one of <1> to <3>, wherein the core layer has an optical waveguide circuit pattern with a core diameter of 1 μm or more and 10 μm or less. <5> The laminate for a photoelectric fusion substrate according to any one of <1> to <4>, wherein the transmission loss of the core layer is 0.2 dB / cm or less. <6> The laminate for a photoelectric fusion substrate according to any one of <1> to <5>, wherein the coefficient of linear expansion of the underclad layer is 80 ppm / K or less. <7> The laminate for a photoelectric fusion substrate according to any one of <1> to <6>, wherein the thermosetting resin composition contains one or more selected from the group consisting of epoxy resin, epoxy / phenol resin, epoxy / cyanate resin, and epoxy / active ester resin. <8> The laminate for a photoelectric fusion substrate according to any one of <1> to <7>, wherein the core layer is made of a first polyimide having structural units represented by the following general formula (1), and the underclad layer is made of a second polyimide having structural units represented by the following general formula (1). In the above general formula (1), R １ This is a tetravalent group selected from the group consisting of the following: In the above general formula (1), R ２ This is a divalent group selected from the group consisting of the following: R ｆ Each of these is independently hydrogen or fluorine, and each of these is independently O, S, SO ２ , or C = O, and Y is independently O, S, SO ２ , or C=O, and in the first polyimide, at least one R ｆis hydrogen, and in the first polyimide, for R ｆ let the number of hydrogen atoms be N Ｈ , for R ｆ let the number of fluorine atoms be N Ｆ , and let the fluorine substitution rate be f ｃｏｒｅ = N Ｆ / (N Ｈ + N Ｆ ), and in the second polyimide, for R ｆ let the number of hydrogen atoms be N Ｈ , for R ｆ let the number of fluorine atoms be N Ｆ , and let the fluorine substitution rate be f ｃｌａｄ = N Ｆ / (N Ｈ + N Ｆ ), when the following formula: f ｃｌａｄ > f ｃｏｒｅ, satisfying the following. <9> The laminate for photoelectric fusion substrate according to <4>, further comprising an overclad layer made of a cured product of a photosensitive resin composition and having a refractive index n3 at a wavelength of 1310 nm or 1550 nm, wherein the average thickness of the overclad layer is 2 μm or more and 35 μm or less greater than the core diameter, and the refractive indices n1 and n3 satisfy the following relationship: 0.1 < 100 × (n1 - n3) / n1 < 5. <10> A laminate for a photoelectric fusion substrate, comprising: an overcladding layer made of a cured product of a photosensitive resin composition and having a refractive index n3 at a wavelength of 1310 nm or 1550 nm; a core layer having a core diameter of 1 μm or more and 10 μm or less, made of a heat-resistant resin with a refractive index n1 at a wavelength of 1310 nm or 1550 nm, and having an optical waveguide circuit pattern; and an undercladding layer having an average thickness of 5 μm or more and 25 μm or less, made of a heat-resistant resin with a refractive index n2 at a wavelength of 1310 nm or 1550 nm, wherein the average thickness of the overcladding layer is 2 μm or more and 35 μm or less greater than the core diameter, the refractive indices n1 and n2 satisfy the relationship: 0.1 < 100 × (n1 - n2) / n1 < 5, and the refractive indices n1 and n3 satisfy the relationship: 0.1 < 100 × (n1 - n3) / n1 < 5. <11> The laminate for photoelectric fusion substrate according to <10>, further comprising a heat-resistant resin layer having an average thickness of 15 μm or more and 150 μm or less, and a glass transition temperature of 150°C or higher, on the surface of the underclad layer opposite to the surface in contact with the core layer. <12> A photoelectric fusion substrate comprising an electronic substrate and a laminate for photoelectric fusion substrate according to any one of <1> to <11>, characterized in that the laminate for photoelectric fusion substrate is fused to the electronic substrate.

[0007] According to this disclosure, it is possible to provide a laminate for photoelectric fusion substrates that can fuse optical waveguides while reducing the degradation of the electronic substrate, and that is excellent in heat resistance, adhesion, and productivity.

[0008] Figure 1 is a cross-sectional view showing an example of a laminate for a photoelectric fusion substrate according to the first embodiment. Figure 2 is a cross-sectional view showing another example of a laminate for a photoelectric fusion substrate according to the first embodiment. Figure 3 is a cross-sectional view showing an example of a laminate for a photoelectric fusion substrate according to the second embodiment. Figure 4 is a cross-sectional view showing another example of a laminate for a photoelectric fusion substrate according to the second embodiment. Figure 5 is a cross-sectional view showing an example of a photoelectric fusion substrate according to the first embodiment. Figure 6 is a cross-sectional view showing another example of a photoelectric fusion substrate according to the first embodiment. Figure 7 is a cross-sectional view showing an example of a photoelectric fusion substrate according to the second embodiment. Figure 8 is a cross-sectional view showing another example of a photoelectric fusion substrate according to the second embodiment.

[0009] Hereinafter, embodiments of this disclosure will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0010] (Laminate for photoelectric fusion substrate) The laminate for photoelectric fusion substrate of the present disclosure comprises a core layer, an underclad layer, and an insulating adhesive layer, and in one embodiment further comprises a heat-resistant resin layer, and may further comprise other layers such as a protective layer as needed.

[0011] The core layer has an average thickness of 1 μm to 10 μm and is made of a heat-resistant resin with a refractive index n1 at a wavelength of 1310 nm or 1550 nm. The underclad layer has an average thickness of 5 μm to 25 μm and is made of a heat-resistant resin with a refractive index n2 at a wavelength of 1310 nm or 1550 nm. The insulating adhesive layer has an average thickness of 10 μm to 200 μm and is made of a thermosetting resin composition. Here, the volume resistivity of the insulating adhesive layer after curing is 10 ８ The refractive index is greater than or equal to Ω·cm, and the refractive indices n1 and n2 satisfy the following relationship: 0.1 < 100 × (n1 - n2) / n1 < 5.

[0012] When manufacturing an optical waveguide consisting of a core and cladding using the heat-resistant polyimide resin described in Patent Document 1, it is generally manufactured by layer coating. Specifically, first, a polyimide precursor for the undercladding is applied and then converted to polyimide by heating to form the undercladding layer. Next, a polyimide precursor for the core is applied and then converted to polyimide by heating to form the core layer. Furthermore, if necessary, the core layer is patterned and an overcladding layer is formed. When considering forming such an optical waveguide on an electronic substrate and fusing it with the electronic substrate, although polyimide itself has excellent heat resistance, the heating temperature required for imidization is high, at 300°C or more, which causes thermal damage to the electronic substrate and degrades the substrate. In particular, when incorporated into the process of electronic substrates that are multilayered by lamination or pressing of films, productivity is reduced, and there is also a problem that the optical properties may be impaired depending on the variation in the formation conditions of the core layer. On the other hand, when considering the use of photosensitive polyimide precursors, the resulting polyimide exhibits inferior heat resistance and transparency compared to thermosetting polyimide precursors, making it particularly difficult to ensure the transparency required for the core layer.

[0013] The present invention is based on the identification of the problems of the prior art described above. The inventors have conducted extensive research to solve the problems of the prior art and the aforementioned issues, and have found a solution comprising: a core layer made of a heat-resistant resin with an average thickness of 1 μm to 10 μm and a refractive index n1 at a wavelength of 1310 nm or 1550 nm; an underclad layer made of a heat-resistant resin with an average thickness of 5 μm to 25 μm and a refractive index n2 at a wavelength of 1310 nm or 1550 nm; and an insulating adhesive layer made of a thermosetting resin composition with an average thickness of 10 μm to 200 μm, in this order, wherein the volume resistivity of the insulating adhesive layer after curing is 10 ８ We have discovered that by using a laminate for photoelectric fusion substrates with a refractive index of Ω·cm or higher and refractive indices n1 and n2 satisfying the relationship: 0.1 < 100 × (n1 - n2) / n1 < 5, it is possible to fuse optical waveguides while reducing the degradation of the electronic substrate, and we can provide a laminate for photoelectric fusion substrates that is excellent in heat resistance, adhesion, and productivity, thus completing the present invention.

[0014] The laminate for photoelectric fusion substrates disclosed herein provides a laminate that ensures the optical performance of the optical waveguide and improves productivity on the optical waveguide side when manufacturing the photoelectric fusion substrate, as the core layer and underclad layer are already cured and have excellent heat resistance and are pre-formed. Furthermore, by incorporating an insulating adhesive layer, it can be easily fused with the electronic substrate via the insulating adhesive layer, resulting in excellent adhesion. In addition, there is no need to perform heat curing to form the core layer and underclad layer, which reduces the degradation of the electronic substrate and improves productivity on the electronic substrate side when manufacturing the photoelectric fusion substrate. Therefore, it is possible to fuse optical waveguides while reducing the degradation of the electronic substrate, and to provide a laminate for photoelectric fusion substrates that is excellent in heat resistance, adhesion, and productivity.

[0015] [Laminate for Photoelectron Fusion Substrate according to the First Embodiment] A laminate for a photoelectron fusion substrate according to the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view showing an example of a laminate for a photoelectron fusion substrate according to the first embodiment, and Figure 2 is a cross-sectional view showing another example of a laminate for a photoelectron fusion substrate according to the first embodiment.

[0016] The laminate 100 for photoelectric fusion substrate shown in Figure 1 has a core layer 10, an underclad layer 21, and an insulating adhesive layer 30, and further comprises an underclad layer 21, a core layer 10 disposed to cover at least a portion of the first surface of the underclad layer 21, and an insulating adhesive layer 30 disposed to cover at least a portion of the second surface of the underclad layer 21.

[0017] The laminate 110 for photoelectric fusion substrate shown in Figure 2 is an embodiment of the laminate 100 for photoelectric fusion substrate shown in Figure 1, further comprising a heat-resistant resin layer 40 between the underclad layer 21 and the insulating adhesive layer 30, and having a heat-resistant resin layer 40, an underclad layer 21 disposed to cover at least a portion of the first surface of the heat-resistant resin layer 40, a core layer 10 disposed to cover at least a portion of the first surface of the underclad layer 21, and an insulating adhesive layer 30 disposed to cover at least a portion of the second surface of the heat-resistant resin layer 40.

[0018] <Core layer and underclad layer> The core layer 10 is a layer made of heat-resistant resin, with an average thickness of 1 μm or more and 10 μm or less, and a refractive index n1 at a wavelength of 1310 nm or 1550 nm. The underclad layer 21 is a layer made of heat-resistant resin, with an average thickness of 5 μm or more and 25 μm or less, and a refractive index n2 at a wavelength of 1310 nm or 1550 nm.

[0019] The average thickness of the core layer 10 can be appropriately selected according to the desired embodiment and the characteristics of the optical waveguide, and may be 1 μm or more and less than 3 μm, or 3 μm or more and 10 μm or less.

[0020] The average thickness of the undercladding layer 21 can be appropriately selected according to the desired configuration and the characteristics of the optical waveguide, as long as it is between 5 μm and 25 μm. However, a thickness of 10 μm to 25 μm is preferable in terms of obtaining sufficient mechanical properties as a cladding layer and ease of processing when forming conductive parts with the electronic substrate.

[0021] The heat-resistant resins for the core layer 10 and the underclad layer 21 are not particularly limited as long as they are a combination of heat-resistant resins whose refractive indices n1 and n2 satisfy the following relationship: 0.1 < 100 × (n1 - n2) / n1 < 5, and can be appropriately selected according to the purpose. For the numerical value 100 × (n1 - n2) / n1, under single-mode (SM) conditions, with a core diameter of 1 μm or more and 10 μm or less and a wavelength of 1.3 μm, a value of 0.15 or more and 4.0 or less is preferred, a value of 0.20 or more and 1.0 or less is more preferred, and a value of 0.25 or more and 0.8 or less is even more preferred. The heat-resistant resins for each layer may be used individually or in combination of two or more types.

[0022] Examples of heat-resistant resins include polyimide resins, polyamide-imide, and aromatic ring-condensed resins such as polybenzoxazole (PBO); polyphenylsulfone, polysulfone, polyarylate, polyetherimide, polyethernitrile, and epoxy resins. Among these, polyimide resins and aromatic ring-condensed resins such as polybenzoxazole are preferred, and polyimide resins are preferred, due to their low coefficient of thermal expansion, excellent transparency, and strength. The higher of the glass transition temperature or melting point of the heat-resistant resin is preferably 150°C or higher, more preferably 200°C or higher, even more preferably 250°C or higher, and particularly preferably 300°C or higher, from the viewpoint of heat resistance of the core layer 10 and the undercladding layer 21.

[0023] -Refractive Index- The refractive index of the core layer 10 at a wavelength of 1310 nm or 1550 nm is preferably 1.500 or more and 1.650 or less, more preferably 1.640 or less, and even more preferably 1.630 or less, 1.625 or less, and 1.620 or less. The refractive index of the underclad layer 21 at a wavelength of 1310 nm or 1550 nm is preferably 1.450 or more and 1.649 or less, more preferably 1.625 or less, 1.620 or less, and 1.610 or less.

[0024] The refractive index may be a measured value obtained by a refractometer, or a calculated value obtained from the structural formula of the resin used. Specifically, the following procedure can be used to calculate the refractive index at a particular wavelength from the structural formula of polyimide. If the chemical structure of the polymer can be determined, the refractive index of the polymer (as amorphous material) can be calculated semi-empirically using the group contribution method (Reference 1: DW van Krevelen, et al., “Properties of Polymers”, Fourth Edition (2009)). The Lorentz-Lorentz equation, proposed in 1880, was used as the calculation formula for the group contribution method (Reference 2: Lorentz HA, Wied Ann Phys 9 (1880) 641).

[0025] -Glass Transition Temperature- The glass transition temperature of the core layer 10 is preferably 150°C or higher, more preferably 200°C or higher, even more preferably 250°C or higher, preferably 500°C or lower, more preferably 250°C to 450°C, and even more preferably 300°C to 400°C. The glass transition temperature of the underclad layer 21 is preferably 200°C to 400°C, more preferably 250°C to 400°C, and even more preferably 300°C to 400°C. When the glass transition temperature is 150°C or higher, a low refractive index material with good solder heat resistance and dimensional stability can be obtained.

[0026] -Transmission Loss- The transmission loss of the core layer 10 is preferably 0.3 dB / cm or less, and more preferably 0.2 dB / cm or less, under the condition of a wavelength of 1310 nm or 1550 nm.

[0027] - Haze - The haze of the heat-resistant resin is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less. When the haze is 20% or less, transparency is obtained when used as a core layer, cladding layer, and optical waveguide, making it suitable for use.

[0028] - Linear expansion coefficient - The linear expansion coefficient refers to the ratio of the deformation amount ΔL per 1 K (Kelvin) or 1°C change in temperature to the original length L. The linear expansion coefficient of the core layer 10 is preferably 80 ppm / K or less, more preferably 70 ppm / K or less, even more preferably 60 ppm / K or less, and particularly preferably 40 ppm / K or less. The linear expansion coefficient of the underclad layer 21 is preferably 80 ppm / K or less, more preferably 70 ppm / K or less, even more preferably 60 ppm / K or less, and particularly preferably 40 ppm / K or less.

[0029] If the coefficient of thermal expansion is too high, the difference in coefficient of thermal expansion between the substrate (or temporary substrate) and the laminate becomes large during the manufacturing process, causing warping and reducing yield. Furthermore, when the insulating adhesive layer is subjected to high temperatures during lamination or solder reflow processes, warping of the laminate itself or delamination of the interfaces between layers can occur, which is undesirable.

[0030] When the heat-resistant resin is polyimide, the coefficient of linear expansion can be measured specifically for a polyimide film obtained by the polyimide film manufacturing method described later, using a thermomechanical analyzer (EXSTAR6000TMA / SS6000, manufactured by SII Nanotechnology Co., Ltd.) under the following measurement conditions: --Measurement conditions-- Stage 1: Heat the sample to 150°C at a heating rate of 5°C / min to remove adsorbed water. Stage 2: Cool the sample to room temperature at a cooling rate of 5°C / min. Stage 3: Perform the measurement at a heating rate of 5°C / min. Determine the average value of the coefficient of linear expansion in the temperature range of 30°C to 200°C and use this as the coefficient of linear expansion of the target polyimide film.

[0031] When the heat-resistant resin is polyimide, the haze can be specifically measured using a spectroscopic haze meter (HSP-150Vis, manufactured by Murakami Color Technology Laboratory Co., Ltd.) on a polyimide film obtained by the polyimide film manufacturing method described later. The average thickness of the polyimide film used as the measurement sample is preferably 5 μm to 80 μm.

[0032] -Elongation at Break- The elongation at break of the polyimide is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more. When the elongation at break is 20% or more, tearing during film transport is less likely to occur in the polyimide film manufacturing process, and good productivity is maintained. Furthermore, bending resistance is maintained when made into a flexible printed circuit board, and cracking and wiring breakage are less likely to occur in the mounting process.

[0033] -Tensile Modulus- The tensile modulus of the heat-resistant resin is preferably 0.5 GPa or higher, more preferably 1 GPa or higher, and even more preferably 2 GPa or higher. When the tensile modulus is 2 GPa or higher, the amount of elongation of the film when tension is applied during film transport in the film manufacturing process is suppressed, and dimensional stability is maintained.

[0034] When the heat-resistant resin is polyimide, the elongation at break and tensile modulus can be measured using a polyimide film obtained by the polyimide film manufacturing method described later. The measurement sample is cut into strips 10 mm wide and 80 mm long, and measured using a Tensilon universal material tester (RTM-100, manufactured by Orientec Co., Ltd.) in accordance with the Japanese Industrial Standard (JIS K 7127:1999). The width of the measurement sample is 10 mm, the chuck spacing is 50 mm, the test speed is 50 mm / min, and the average value is calculated with n=10 measurements.

[0035] <Insulating Adhesive Layer> The insulating adhesive layer 30 is a layer made of a thermosetting resin composition, with an average thickness of 10 μm or more and 200 μm or less, and the volume resistivity of the insulating adhesive layer after curing is 10 ８ The density is Ω·cm or greater. Here, the cured insulating adhesive layer is the cured product of the insulating adhesive layer 30 and can function as an insulating layer.

[0036] The average thickness of the insulating adhesive layer 30 can be appropriately selected depending on the desired embodiment, as long as it is between 10 μm and 200 μm. However, from the viewpoint of dielectric strength and processability, 10 μm to 200 μm is preferred, 15 μm to 100 μm is more preferred, 20 μm to 50 μm is even more preferred, and 30 μm to 40 μm is particularly preferred.

[0037] The thermosetting resin composition contains a thermosetting resin having insulating and adhesive properties, and may also contain an inorganic filler, and further, if necessary, other components such as a curing agent and a solvent. Furthermore, the insulating adhesive layer 30 is preferably in sheet form for ease of manufacture.

[0038] Examples of thermosetting resins include epoxy resins, epoxy / phenol resins, epoxy / cyanate resins, and epoxy / activated ester resins. These may be used individually or in combination of two or more. Among these, epoxy resins are preferred because they have high mechanical strength, heat resistance, and electrical insulation properties, as well as excellent water resistance, chemical resistance, and adhesion.

[0039] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AF type epoxy resin, phenol novolac type epoxy resin, tert-butyl-catechol type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, naphthylene ether type epoxy resin, glycidylamine type epoxy resin, glycidyl ester type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin, anthracene type epoxy resin, linear aliphatic epoxy resin, epoxy resin having a butadiene structure, alicyclic epoxy resin, heterocyclic epoxy resin, spiroring-containing epoxy resin, cyclohexanedimethanol type epoxy resin, trimethylol type epoxy resin, and halogenated epoxy resin.

[0040] Among these, bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, naphthylene ether type epoxy resin, glycidyl ester type epoxy resin, anthracene type epoxy resin, and epoxy resins having a butadiene structure are preferred due to their superior heat resistance and electrical insulation properties.

[0041] Examples of inorganic fillers include silica, barium sulfate, silicon dioxide, calcined talc, zinc molybdenum-treated talc, barium titanate, titanium dioxide, clay, alumina, mica, boehmite, zinc borate, zinc stannate, other metal oxides or metal hydrates, aluminum hydroxide, calcium carbonate, magnesium hydroxide, magnesium silicate, glass fibers, aluminum borate whiskers, and silicon carbonate whiskers. These may be used individually or in combination of two or more. Among these inorganic fillers, those with silica as the main component are preferred.

[0042] Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, hollow silica, and spherical silica. Among these, spherical silica and fused silica are preferred.

[0043] The median diameter of silica is preferably 2 μm or less, more preferably 1 μm or less, even more preferably 0.8 μm or less, and particularly preferably 0.6 μm or less, from the viewpoint of electrical insulation and surface smoothness. Furthermore, from the viewpoint of improving the dispersibility of silica, it is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more. The median diameter of silica can be measured by laser diffraction and scattering method based on Mie scattering theory. Specifically, it can be measured by a laser diffraction and scattering particle size distribution analyzer (for example, LA-950, manufactured by Horiba, Ltd.).

[0044] When a thermosetting resin composition contains an inorganic filler, the inorganic filler content is preferably 30 parts by mass or more and 80 parts by mass or less per 100 parts by mass of resin. When the content is 30 parts by mass or more, a sufficient effect of reducing the coefficient of thermal expansion can be obtained. When the content is 80 parts by mass or less, sufficient moldability of the thermosetting resin composition can be obtained.

[0045] <Heat-resistant resin layer> The heat-resistant resin layer 40 is a layer made of a heat-resistant resin having a glass transition temperature of 150°C or higher, and has an average thickness of 15 μm or more and 150 μm or less. As for the heat-resistant resin, there are no particular restrictions as long as the glass transition temperature is 150°C or higher, and it can be appropriately selected according to the purpose. Examples include polyimide resin, aromatic ring condensation resins such as polybenzoxazole (PBO); polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; polyolefin resins such as polyethylene, polypropylene, polystyrene; polycarbonate, polyether sulfide, polyether sulfone, polyether ketone, polyphenylene ether, polyphenylene sulfide, polyarylate, polysulfone, and liquid crystal polymers. These may be used individually or in combination of two or more. Among these, polyimide resin is preferred because it has a low coefficient of thermal expansion and excellent strength.

[0046] The coefficient of linear expansion of the heat-resistant resin layer 40 is preferably 80 ppm / K or less, more preferably 60 ppm / K or less, and even more preferably 40 ppm / K or less. The glass transition temperature of the heat-resistant resin layer 40 is 150°C or higher, preferably 200°C to 500°C, and more preferably 300°C to 400°C.

[0047] There are no particular limitations on the method for manufacturing a laminate for a photoelectric fusion substrate according to the first embodiment, and it can be appropriately selected depending on the purpose. For example, the following (I) to (II) are examples: (I) A manufacturing method comprising the steps of: applying and drying a composition containing a heat-resistant resin precursor for an underclad layer onto a heat-resistant resin layer 40 or a temporary substrate, and then thermally curing the obtained coating film to form an underclad layer 21; applying and drying a composition containing a heat-resistant resin precursor for a core layer onto the underclad layer 21, and then thermally curing the obtained coating film to form a core layer 10; and, if necessary, peeling off the temporary substrate to form an insulating adhesive layer 30. (II) A manufacturing method comprising the steps of: applying and drying a composition containing a heat-resistant resin precursor for an underclad layer onto a heat-resistant resin layer 40 or a temporary substrate, applying and drying a composition containing a heat-resistant resin precursor for a core layer onto the obtained coating film, and then thermally curing the obtained coating film to form an underclad layer 21 and a core layer 10; and, if necessary, peeling off the temporary substrate to form an insulating adhesive layer 30. Alternatively, a method can be appropriately selected in which a composition containing a heat-resistant resin precursor is cast onto a heated heat-resistant resin layer 40 or a temporary substrate and then heat-cured.

[0048] There are no particular restrictions on the temporary substrate, and it can be appropriately selected according to the purpose. Examples include glass substrates; metal substrates such as stainless steel drums, endless stainless steel belts, and aluminum foil.

[0049] [Laminate for Photoelectron Fusion Substrate according to the Second Embodiment] A laminate for a photoelectron fusion substrate according to the second embodiment will be described with reference to Figures 3 and 4. Figure 3 is a cross-sectional view showing an example of a laminate for a photoelectron fusion substrate according to the second embodiment, and Figure 4 is a cross-sectional view showing another example of a laminate for a photoelectron fusion substrate according to the second embodiment.

[0050] The laminate 200 for photoelectric fusion substrate shown in Figure 3 is an embodiment of the laminate 100 for photoelectric fusion substrate shown in Figure 1, in which an optical waveguide circuit pattern is formed on the core layer, and comprises an underclad layer 21, a core layer 11 having an optical waveguide circuit pattern arranged to cover at least a portion of the first surface of the underclad layer 21, and an insulating adhesive layer 30 arranged to cover at least a portion of the second surface of the underclad layer 21.

[0051] The laminate 210 for photoelectric fusion substrate shown in Figure 4 is an embodiment of the laminate 110 for photoelectric fusion substrate shown in Figure 2, in which an optical waveguide circuit pattern is formed on the core layer, and comprises a heat-resistant resin layer 40, an underclad layer 21 disposed to cover at least a portion of the first surface of the heat-resistant resin layer 40, a core layer 11 having an optical waveguide circuit pattern disposed to cover at least a portion of the first surface of the underclad layer 21, and an insulating adhesive layer 30 disposed to cover at least a portion of the second surface of the heat-resistant resin layer 40.

[0052] There are no particular limitations on the method for manufacturing the laminate for the photoelectric fusion substrate according to the second embodiment, and it can be appropriately selected depending on the purpose. Specifically, in the method for manufacturing the laminate for the photoelectric fusion substrate according to the first embodiment, one method is to form an optical waveguide circuit pattern on the core layer 10 in a step prior to attaching the insulating adhesive layer 30.

[0053] The core layer 11 having an optical waveguide circuit pattern can be formed, for example, by patterning the core layer 10 in the laminate 100 for the photoelectric fusion substrate shown in Figure 1, and can be carried out by dry etching such as reactive ion etching (RIE). Specifically, a resist is applied to the core layer 10 formed on the underclad layer 21 and mask exposure is performed to form a patterned resist layer. Next, the parts of the core layer where the resist layer is not formed are dry etched and the resist layer is peeled off to form the core layer 11 having an optical waveguide circuit pattern. At this time, the underclad layer 21 may be provided on a heat-resistant resin layer 40 or a temporary substrate and pattern formation may be performed, or after pattern formation, it may be peeled off from the temporary substrate and an insulating adhesive layer 30 may be provided. Alternatively, a dry mask (such as a sputtered film of ZnO, CrO, etc.) may be formed between the resist layer and the core layer, and specifically, a dry mask may be patterned using the resist pattern as a mask, and the formed dry mask pattern may be used as a mask to perform dry etching and pattern the core layer.

[0054] The core diameter of the core layer 11 having an optical waveguide circuit pattern is 1 μm or more and 10 μm or less, and can be appropriately selected depending on the purpose. If the core diameter is 1 μm or more, the alignment tolerance can be increased when coupling with the light-emitting / receiving element or optical fiber after optical waveguide formation, and if the core diameter is 10 μm or less, the refractive index difference between the core and cladding in single mode can be increased, and bending loss can be reduced as an optical waveguide. Here, core diameter refers to the fiber diameter in a fibrous core layer, or the diameter of the fiber cross-section.

[0055] [Laminate for Photoelectron Fusion Substrate according to the Third Embodiment] A laminate for a photoelectron fusion substrate according to the third embodiment will be described with reference to Figures 5 and 6. Figure 5 is a cross-sectional view showing an example of a laminate for a photoelectron fusion substrate according to the third embodiment, and Figure 6 is a cross-sectional view showing another example of a laminate for a photoelectron fusion substrate according to the third embodiment.

[0056] The laminate 300 for photoelectric fusion substrate shown in Figure 5 is an embodiment of the laminate 200 for photoelectric fusion substrate shown in Figure 3, further comprising an overcladding layer 22, and includes an undercladding layer 21, a core layer 11 having an optical waveguide circuit pattern disposed to cover at least a portion of the first surface of the undercladding layer 21, an overcladding layer 22 that covers the side surface of the core layer 11 having the optical waveguide circuit pattern together with the first surface of the undercladding layer 21, and an insulating adhesive layer 30 disposed to cover at least a portion of the second surface of the undercladding layer 21. Here, the undercladding layer 21 and the overcladding layer 22 form a cladding layer 20 that covers the side surface of the core layer 11 having the optical waveguide circuit pattern.

[0057] The laminate 210 for photoelectric fusion substrate shown in Figure 6 is an embodiment of the laminate 210 for photoelectric fusion substrate shown in Figure 4, further comprising an overclad layer 22, and includes a heat-resistant resin layer 40, an underclad layer 21 disposed to cover at least a portion of the first surface of the heat-resistant resin layer 40, a core layer 11 having an optical waveguide circuit pattern disposed to cover at least a portion of the first surface of the underclad layer 21, an overclad layer 22 that covers the side surface of the core layer 11 having the optical waveguide circuit pattern together with the first surface of the underclad layer 21, and an insulating adhesive layer 30 disposed to cover at least a portion of the second surface of the heat-resistant resin layer 40. Here, the underclad layer 21 and the overclad layer 22 form a clad layer 20 that covers the side surface of the core layer 11 having the optical waveguide circuit pattern.

[0058] <Overclad layer> The overclad layer 22 is made of a cured product of the photosensitive resin composition and has a refractive index n3 at a wavelength of 1310 nm or 1550 nm. The photosensitive resin contained in the photosensitive resin composition may be a positive-type photosensitive resin whose solubility in the developer solution is improved when exposed to energy rays such as ultraviolet rays and in which the exposed areas can be removed, or a negative-type photosensitive resin which hardens when exposed to energy rays and in which the unexposed areas can be removed by the developer solution, and either can be selected as appropriate.

[0059] The cured product of the photosensitive resin composition of the overcladding layer 22 is not particularly limited as long as the refractive indices n1 and n3 are a combination of heat-resistant resins that satisfy the relationship: 0.1 < 100 × (n1 - n3) / n1 < 5, and can be appropriately selected according to the purpose. For the numerical value 100 × (n1 - n3) / n1, under single-mode (SM) conditions, with a core diameter of 1 μm or more and 10 μm or less and a wavelength of 1.3 μm, it is preferably 0.15 or more and 4.0 or less, more preferably 0.20 or more and 1.0 or less, and even more preferably 0.25 or more and 0.8 or less.

[0060] The cured product of the photosensitive resin composition of the overclad layer 22 may be the same as or of the same type as the heat-resistant resin of the underclad layer 21, as long as it satisfies the above formula, or it may be different from each other. In addition, the refractive index difference between the refractive indices n3 and n2 (|n3-n2|) may or may not be present, but |n3-n2| is preferably 0 or more and 0.10 or less, and more preferably 0 or more and 0.05 or less.

[0061] The average thickness of the overcladding layer 22 is sufficient to cover the sides of each fiber-shaped core of the core layer 11 having the optical waveguide circuit pattern, and is 2 μm to 35 μm greater than the core diameter, for example, 3 μm to 45 μm. The thickness of the overcladding layer 22 is the value from the boundary between the core layer 11 having the optical waveguide circuit pattern and the undercladding layer 21 to the upper surface of the overcladding layer 22.

[0062] The photosensitive resin composition contains a photosensitive resin, may also contain an inorganic filler, and may further contain other components such as a curing agent and a solvent as needed.

[0063] Examples of photosensitive resins include photosensitive polyimide resins, photosensitive acrylic resins, and photosensitive epoxy resins. These may be used individually or in combination of two or more types.

[0064] The overcladding layer 22 can be formed by applying a photosensitive resin composition to cover the side surface of the core layer 11 having an optical waveguide circuit pattern, together with the first surface of the undercladding layer 21, and curing the photosensitive resin composition by light irradiation.

[0065] [Laminate for Photoelectron Fusion Substrate according to the Fourth Embodiment] A laminate for a photoelectron fusion substrate according to the fourth embodiment will be described with reference to Figures 7 and 8. Figure 7 is a cross-sectional view showing an example of a laminate for a photoelectron fusion substrate according to the fourth embodiment, and Figure 8 is a cross-sectional view showing another example of a laminate for a photoelectron fusion substrate according to the fourth embodiment.

[0066] The laminate 400 for photoelectric fusion substrate shown in Figure 7 is an embodiment having an overclad layer 22, a core layer 11 having an optical waveguide circuit pattern, and an underclad layer 21, wherein the underclad layer 21 has an underclad layer 21, a core layer 11 having an optical waveguide circuit pattern arranged to cover at least a portion of the first surface of the underclad layer 21, and an overclad layer 22 that covers the side surface of the core layer 11 having the optical waveguide circuit pattern together with the first surface of the underclad layer 21.

[0067] The laminate 410 for photoelectric fusion substrate shown in Figure 8 is an embodiment of the laminate 400 for photoelectric fusion substrate shown in Figure 7, further having a heat-resistant resin layer 40 on the second surface side of the underclad layer 21, and comprises a heat-resistant resin layer 40, an underclad layer 21 disposed to cover at least a portion of the first surface of the heat-resistant resin layer 40, a core layer 11 having an optical waveguide circuit pattern disposed to cover at least a portion of the first surface of the underclad layer 21, and an overclad layer 22 that covers the side surface of the core layer 11 having an optical waveguide circuit pattern together with the first surface of the underclad layer 21.

[0068] There are no particular limitations on the method for manufacturing the laminate for the photoelectric fusion substrate according to the fourth embodiment, and it can be appropriately selected depending on the purpose. Specifically, it can be carried out in the same manner as the method for manufacturing the laminate for the photoelectric fusion substrate according to the second embodiment, except that the insulating adhesive layer 30 is not attached.

[0069] [Embodiment in which the core layer and underclad layer are polyimide] In the laminate for photoelectric fusion substrate and the photoelectric fusion substrate of this embodiment, in terms of having a low coefficient of thermal expansion, excellent transparency and strength, the heat-resistant resin of the core layer 10 and the underclad layer 21 is preferably an aromatic ring condensation resin such as polyimide resin or polybenzoxazole (PBO), more preferably a fluorine-substituted aromatic ring condensation resin, and even more preferably a fluorine-substituted polyimide resin.

[0070] Among fluorine-substituted polyimide resins, a more preferable embodiment is one in which the core layer consists of a first polyimide having structural units represented by the following general formula (1), and the undercladding layer consists of a second polyimide having structural units represented by the following general formula (1). The general formula (1) is specified by the following formula: f ｃｌａｄ > f ｃｏｒｅ By having a combination of a first polyimide and a second polyimide that satisfy the above conditions, it is possible to achieve excellent transmission loss reduction, heat resistance, and low birefringence, and specifically, it can be applied as a laminate for optical waveguides suitable for single-mode optical wavelengths of 1310 nm and 1550 nm.

[0071] In the above general formula (1), R １ This is a tetravalent group selected from the group consisting of the following:

[0072] In the above general formula (1), R ２ This is a divalent group selected from the group consisting of the following:

[0073]

[0074] In the above general formula (1), R ｆ Each of these is independently hydrogen or fluorine, and each of these is independently O, S, SO ２ , or C=O, and Y is independently O, S, SO ２ , or C=O. In the first polyimide, at least one R ｆ is hydrogen. In the first polyimide, R ｆ The number of hydrogen atoms in N Ｈ , Rｆ The number of fluorine atoms in N Ｆ , the fluorine substitution rate is f ｃｏｒｅ = N Ｆ / (N Ｈ +N Ｆ ) and in the second polyimide, R ｆ The number of hydrogen atoms in N Ｈ , R ｆ The number of fluorine atoms in N Ｆ , the fluorine substitution rate is f ｃｌａｄ = N Ｆ / (N Ｈ +N Ｆ When we consider the following equation: f ｃｌａｄ > f ｃｏｒｅ It satisfies the condition.

[0075] Here, R ｆ X and Y are CF ３ By not containing Cl or Br, it has the advantage of reducing birefringence and thus reducing transmission loss.

[0076] In the first polyimide, R derived from the diamine ２ at least one R in ｆ In one embodiment, it is preferable that the R is fluorine, and R is derived from an acid anhydride. １ at least one R in ｆ In other embodiments, it is preferable that the substance is fluorine, and in further embodiments, it is preferable that both conditions are met.

[0077] In the second polyimide, R derived from the diamine ２ at least one R in ｆ In one embodiment, it is preferable that the R is fluorine, and R is derived from an acid anhydride. １ at least one R in ｆ In other embodiments, it is preferable that the substance is fluorine, and in further embodiments, it is preferable that both conditions are met.

[0078] In the first polyimide represented by the general formula (1), or the second polyimide represented by the general formula (1), R derived from acid anhydride １As such, a tetravalent group represented by the following formula (1-1) is preferred, and a tetravalent group represented by the following formula (1-2), a tetravalent group represented by the following formula (1-3), etc. are more preferred. In the above general formula (1), R １ It may be used alone, or two or more may be used in combination to form a copolymer, and in embodiments in which two or more are used in combination, it is preferable that it further has a tetravalent group represented by the following formula (1-4).

[0079]

[0080] In the above formula (1-1), R ｆ Each of these is independently hydrogen or fluorine, and each of these is independently O or S. ｆ The number of hydrogen atoms in N Ｈ , R ｆ The number of fluorine atoms in N Ｆ When R is set to R １ Fluorine substitution rate N Ｆ / (N Ｈ +N Ｆ The ratio is 0.2 or more and 0.9 or less, preferably 0.4 or more and 0.9 or less, more preferably 0.4 or more and 0.8 or less, and even more preferably 0.4 or more and 0.7 or less.

[0081]

[0082] In the above formula (1-2), R ｆ X and the fluorine substitution rate can be appropriately selected from the items described in formula (1-1) above.

[0083]

[0084] In the above formula (1-3), X can be appropriately selected to describe the matters described in formula (1-1).

[0085]

[0086] In the above general formula (1), R ２ The divalent group can be selected as appropriate for the purpose, as long as it contains an aromatic ring in its main skeleton, without any particular restrictions, but it is preferable that it be a divalent group selected from the group consisting of the following.

[0087] As one embodiment, in the first polyimide represented by the general formula (1) or the second polyimide represented by the general formula (1), R １ is selected from the group consisting of the following, and it is preferable that R ２ is selected from the group consisting of the following.

[0088]

[0089]

[0090] Also, in the first polyimide represented by the general formula (1) or the second polyimide represented by the general formula (1), R derived from diamine ２ is preferably a divalent group represented by the formula (2-1), and a divalent group represented by the following formula (2-2), a divalent group represented by the following formula (1-3), a divalent group represented by the following formula (2-4), a divalent group represented by the following formula (2-5), a divalent group represented by the following formula (2-6), a divalent group represented by the following formula (2-7), etc. are more preferable. In the general formula (1), R ２ may be used alone or in combination of two or more to form a copolymer.

[0091]

[0092] In the formula (2-1), R ｆ is each independently hydrogen or fluorine, and Y is each independently O or S. When the number of hydrogen atoms in R ｆ is N Ｈ and the number of fluorine atoms in R ｆ is N Ｆ , the fluorine substitution rate N １ in R Ｆ / (N Ｈ + N Ｆ ) is 0.15 or more and 1.0 or less, preferably 0.3 or more and 1.0 or less, and more preferably 0.5 or more and 1.0 or less.

[0093]

[0094] In the formula (2-2), R ｆ , and the fluorine substitution rate can be appropriately selected from the matters described for the formula (2-1).

[0095]

[0096]

[0097] In the formula (2-4), R ｆ , and the fluorine substitution rate can be appropriately selected from the matters described for the formula (2-1).

[0098]

[0099] In the formula (2-5), R ｆ , and the fluorine substitution rate can be appropriately selected from the matters described for the formula (2-1).

[0100]

[0101] In the formula (2-6), R ｆ , and the fluorine substitution rate can be appropriately selected from the matters described for the formula (2-1).

[0102]

[0103] In the formula (2-7), R ｆ , and the fluorine substitution rate can be appropriately selected from the matters described for the formula (2-1).

[0104] - Relationship with fluorine substitution rate - The fluorine substitution rate of the first polyimide is, in the first polyimide, when the number of hydrogen atoms in R ｆ is N Ｈ , the number of fluorine atoms in R ｆ is N Ｆ , it is defined as f ｃｏｒｅ = N Ｆ / (N Ｈ + N Ｆ ). The fluorine substitution rate of the second polyimide is, in the second polyimide, when the number of hydrogen atoms in R ｆ is N Ｈ , the number of fluorine atoms in R ｆ is N Ｆ , it is defined as f ｃｌａｄ = N Ｆ / (N Ｈ + N Ｆ ).

[0105] Here, the following equation: f ｃｌａｄ > f ｃｏｒｅ The transmission loss can be reduced by satisfying the following conditions, that is, by having a fluorine substitution rate of the second polyimide greater than that of the first polyimide. ｃｌａｄ and f ｃｏｒｅ The relationship is given by the following equation: 0.005 ≤ f ｃｌａｄ -f ｃｏｒｅ It is preferable that the value < 0.5 be satisfied.

[0106] The fluorine substitution rate f of the first polyimide ｃｏｒｅ There are no particular restrictions on this, and it can be selected as appropriate depending on the purpose, but from the viewpoint of transparency of the core layer, a value of 0.50 or more and 0.97 or less is preferred, with a lower limit of 0.55 or more being more preferred, 0.60 or more being even more preferred, and 0.65 or more being particularly preferred, and an upper limit of 0.95 or less being more preferred, and 0.90 or less being even more preferred.

[0107] Furthermore, the number of modes in an optical waveguide can be predicted by calculation. For example, when the core diameter is 6 μm or more, it can be calculated using the following formula (1).

[0108] a: Waveguide core radius [μm] λ: Free-space wavelength [μm] NA: Numerical aperture V: Normalized frequency

[0109] For single-mode emission to be valid, the normalized frequency V ≤ 2.405. Specifically, by substituting the free-space wavelength λ = 1.31 [μm] or 1.55 [μm], the waveguide core radius a = 3 [μm], and the normalized frequency V = 2.405, the numerical aperture NA at a wavelength of 1.31 [μm] or 1.55 [μm] can be calculated. Then, using the following equation (2), the refractive index n of the core layer that gives the numerical aperture NA can be calculated. ｃｏｒｅ , and the refractive index n of the cladding layer ｃｌａｄ We can find the combinations.

[0110]

[0111] -Method for the Synthesis of Polyimides- First polyimides, second polyimides, and other polyimide resins are collectively referred to as polyimides. There are no particular restrictions on the method for synthesizing the polyimides, and a known method can be appropriately selected depending on the purpose. For example, polyamic acid (polyamic acid), which is a precursor of polyimides, can be synthesized by polymerizing equimolar amounts of acid anhydride and diamine. The obtained polyamic acid can then be heated at a temperature of 200°C or higher, or an imidation (dehydration and cyclization) reaction can be carried out using a catalyst to obtain polyimides.

[0112] The acid anhydride and diamine corresponding to the polyimide represented by the general formula (1) are the acid anhydride represented by the general formula (3) and the diamine represented by the general formula (4) below. In the general formula (3), R １ R in the general formula (1) is １ This is equivalent to the above general formula (4) R ２ R in the general formula (1) is ２ This is synonymous with the above. A tetracarboxylic acid corresponding to the above acid anhydride may be used instead of, or in combination with, the above acid anhydride.

[0113]

[0114] When multiple acid anhydrides and / or multiple diamines are used, the resulting polyamic acid and polyimide may be random copolymers, block copolymers, or mixtures thereof.

[0115] The polyamic acid and the composition containing the polyamic acid can be synthesized, for example, by the following procedure. A thermometer and a stirring rod with stirring blades are set in a 300 mL four-neck separable flask. Next, a solvent (e.g., dimethylacetamide, DMAC) is added under a stream of dry nitrogen and the temperature is raised to 60°C. After the temperature is raised, the diamine is added and dissolved while stirring. Then, equimolar amounts of acid anhydride are added and stirred to polymerize the acid anhydride and the diamine. After that, the mixture is cooled to room temperature, and if necessary, a solvent is added and the mixture is filtered to obtain a composition containing polyamic acid.

[0116] The reaction temperature for polymerizing the acid anhydride and the diamine is preferably -20°C to 150°C, and more preferably 0°C to 100°C. The reaction time is preferably 0.1 hours to 168 hours, and more preferably 0.5 hours to 96 hours. It is also preferable that the number of moles of acid anhydride and the number of moles of diamine used in the reaction are equal. Polyamic acids in which the amounts of acid anhydride and diamine are close to equal tend to yield polyimide films with high mechanical properties.

[0117] A method for synthesizing polyimide from polyamic acid by imidation reaction can be, for example, the following procedure: The composition containing the obtained polyamic acid is applied to a substrate (e.g., by spin coating). Then, it is dried using a hot plate (e.g., at 70°C for 5 minutes). Subsequently, a film-like polyimide can be formed on the substrate by heating at a temperature of 200°C or higher. A method for heating at a temperature of 200°C or higher can be, for example, using an oven under a nitrogen atmosphere (oxygen concentration of 20 ppm or less), raising the temperature from 50°C at a rate of 4°C / min, heating at 180°C for 30 minutes, and then continuing to heat at 350°C for 30 minutes.

[0118] -Method for Identifying Polyimides- There are no particular limitations on the method for identifying the polyimides, and any method can be appropriately selected depending on the purpose. For example, one method is to analyze the polyimides using the infrared total reflection attenuation method (IR-ATR method) with a Fourier transform infrared spectrometer (FT-IR) to identify constituent components such as acid anhydrides and diamines. FT-IR measurements can be performed, for example, using a Nicolet 6700 (manufactured by Thermo Fisher Scientific Co., Ltd.).

[0119] (Photoelectric Fusion Substrate) The photoelectric fusion substrate of the present disclosure comprises an electronic substrate and a laminate for the photoelectric fusion substrate of the present disclosure as described above, wherein the laminate for the photoelectric fusion substrate is fused to the electronic substrate. Another embodiment of the photoelectric fusion substrate comprises a photoelectric conversion element and / or an electro-to-photoelectric conversion element and a laminate for the photoelectric fusion substrate of the present disclosure as described above, wherein the laminate for the photoelectric fusion substrate is fused to the photoelectric conversion element and / or an electro-to-photoelectric conversion element.

[0120] One method for electrically joining a laminate for photoelectric integration substrates to an electronic substrate is to create through-holes in the planned joining area of ​​the laminate for photoelectric integration substrates, which will be placed at the joining portion of the electronic substrate, by laser processing, place it on the electronic substrate, and then form copper wiring by copper plating or the like to create through-holes.

[0121] As a method for forming an optical junction between a laminate for photoelectric fusion substrates and a photoelectric conversion element and / or an electro-optical conversion element, for example, when curing the overcladding layer, the area to be bonded is left unexposed, exposing a part of the core layer without forming the overcladding layer, the junction of the photoelectric conversion element and / or electro-optical conversion element is bonded to the exposed portion, and then sealed with underfill.

[0122] The photoelectric integration substrate disclosed herein has a laminate for photoelectric integration substrates in which a core layer and an underclad layer are already cured and have excellent heat resistance, thereby ensuring the optical performance of the optical waveguide and improving productivity on the optical waveguide side when manufacturing the photoelectric integration substrate. Furthermore, by combining it with an insulating adhesive layer, it can be easily fused with an electronic substrate via the insulating adhesive layer, resulting in excellent adhesion. In addition, when manufacturing the photoelectric integration substrate, there is no need to perform thermal curing to form the core layer and underclad layer, which reduces the degradation of the electronic substrate and improves productivity on the electronic substrate side. Therefore, it is possible to fuse optical waveguides while reducing the degradation of the electronic substrate, and a photoelectric integration substrate with excellent heat resistance, adhesion, and productivity can be provided.

[0123] The present invention will be described more specifically below based on examples, but the present invention is not limited to the following examples.

[0124] <Example of Synthesis of Polyamic Acid for Core Layer> A polyamic acid for the core layer satisfying the above general formula (1) was synthesized by the following procedure. 25 mol% of 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride (10FEDA), 25 mol% of benzene-1,2,4,5-tetracarboxylic acid dianhydride, 50 mol% of tetrafluoro-1,3-phenylenediamine (4FMPD), and the equivalent of 2500 mol% of N,N-dimethylacetamide (DMAc) were added to a flask. This solution was stirred in a nitrogen atmosphere at room temperature for 7 days to obtain polyamic acid for the core layer as a DMAc solution of partially fluorinated polyamic acid. The fluorine substitution rate of the polyamic acid for the core layer was 90%.

[0125] <Example of Synthesis of Polyamic Acid for Undercladding Layers> A polyamic acid for undercladding layers satisfying the above general formula (1) was synthesized by the following procedure. 50 mol% of 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride (10FEDA), 50 mol% of tetrafluoro-1,3-phenylenediamine (4FMPD), and the equivalent of 2500 mol% of N,N-dimethylacetamide (DMAc) were added to a flask. This solution was stirred in a nitrogen atmosphere at room temperature for 7 days to obtain polyamic acid for undercladding layers as a DMAc solution of totally fluorinated polyamic acid.

[0126] (Example 1) <Manufacturing of laminate 1 for photoelectric fusion substrate> A laminate 1 for photoelectric fusion substrate having the configuration shown in Figure 2 was manufactured by following the procedure below.

[0127] <<Formation of the Underclad Layer>> A polyamic acid for the underclad layer was spin-coated onto a polyimide film (Kapton® film, size: 100 mm x 100 mm, average thickness 25 μm, manufactured by Toray DuPont Co., Ltd.) as a heat-resistant resin layer. The film was then heated under a nitrogen atmosphere at 70°C for 2 hours, 160°C for 1 hour, 250°C for 30 minutes, and 350°C for 1 hour to convert it to polyimide by imidization, forming an underclad layer with an average thickness of 10 μm.

[0128] <<Formation of the core layer>> Next, polyamic acid for the core layer was spin-coated onto the underclad layer, and heated under a nitrogen atmosphere at 70°C for 2 hours, 160°C for 1 hour, 250°C for 30 minutes, and 350°C for 1 hour to convert it to polyimide by imidation, forming a core layer with an average thickness of 5 μm.

[0129] <<Formation of insulating adhesive layer>> Next, a build-up film (ABF film, average thickness 30 μm, manufactured by Ajinomoto Co., Inc.) was placed on the surface of the underclad layer opposite to the core layer formation surface as an insulating adhesive layer, and laminated by vacuum lamination to produce a laminate 1 for the photoelectric fusion substrate of Example 1 having the configuration shown in Figure 2.

[0130] <Evaluation> The glass transition temperature of the underclad layer, the refractive index of the core layer and underclad layer, and the coefficient of linear thermal expansion (CTE) of the underclad layer were measured and evaluated using the following procedure.

[0131] <<Measurement of Glass Transition Temperature>> After preparing a film-like sample, dynamic viscoelasticity was measured from room temperature to 380°C at a rate of 2°C / min using a rheometer HR20 manufactured by TA Instruments under conditions of 0.1% strain and 1 Hz. The peak temperature of the obtained tanδ was defined as the glass transition temperature. The results are shown in Table 1.

[0132] <<Measurement of Refractive Index at Wavelength 1550 nm>> Polyamic acid for the undercladding layer was spin-coated onto a silicon wafer, and a cladding film with an average thickness of approximately 8 μm was formed by imidization by heating at 70°C for 2 hours, 160°C for 1 hour, 250°C for 30 minutes, and 350°C for 1 hour under a nitrogen atmosphere. The refractive index of the formed cladding film was measured using a prism coupler apparatus (Model 2010 / M, manufactured by Metricon) under the following measurement conditions. The results are shown in Table 1. -Measurement Conditions- ・Temperature 25°C ・Prism 200-P-1 prism for low refractive index measurement n < 1.80 ・Single film mode: refractive index and film thickness, wavelength: 1550 nm ・TE mode ・Step size Half (high resolution)

[0133] <<Measurement of Linear Thermal Expansion Coefficient (CTE)>> The linear thermal expansion coefficient (CTE) of the underclad layer was measured using TMA measurement in tensile mode with a TMA-7100 (manufactured by Hitachi High-Tech Science Corporation). First, the underclad film with an average thickness of approximately 8 μm was formed on the silicon wafer by spin coating and heating in a nitrogen atmosphere at 70°C for 2 hours, 160°C for 1 hour, 250°C for 30 minutes, and 350°C for 1 hour, through imidization. Next, the formed film was peeled from the silicon wafer by immersion in water, and the peeled film was cut into strips 20 mm long and 5 mm wide. The cut polyimide film sheets were used as measurement samples, the chuck spacing was set to 10 mm, and the CTE (linear expansion coefficient) was determined from the displacement of the sample from 0°C to 200°C at a heating rate of 2°C / min while applying a load of 49 mN. The results are shown in Table 1.

[0134] (Example 2) <Manufacturing of laminate 2 for photoelectric fusion substrate> A laminate 2 for photoelectric fusion substrate, further having an overcladding layer 22 on the core layer 10 of the laminate 1 for photoelectric fusion substrate, was manufactured by the following procedure.

[0135] <<Formation of Overclad Layer>> On the core layer of the laminate 1 for the photoelectric fusion substrate of Example 1, an acrylic hard coat (Beamset 575CB, manufactured by Arakawa Chemical Industries, Ltd.; refractive index n3: 1.51 at a wavelength of 1550 nm of the cured product) was applied as a photosensitive resin composition for forming the overclad layer. Then, 600 mJ / cm was applied. ２ The material was cured to form an overcladding layer that covers the first surface of the undercladding layer and the side surface of the core layer having an optical waveguide circuit pattern.

[0136] Furthermore, in order to form the connection part with the photoelectric conversion element, the overclad layer was cured by leaving unexposed areas during UV irradiation, and then washed with MEK (methyl ethyl ketone) as a solvent to expose a part of the core.

[0137] <<Formation of insulating adhesive layer>> An OPP (MA-411, manufactured by Oji F-Tex Co., Ltd.) protective layer was applied to the overclad layer for protection. After peeling off the laminate obtained from the glass substrate, a build-up film (ABF film, average thickness 30 μm, manufactured by Ajinomoto Co., Inc.) was placed on the surface of the underclad layer opposite to the core layer formation surface as an insulating adhesive layer, and laminated by vacuum lamination to produce laminate 2 for the photoelectric fusion substrate of Example 2.

[0138]

[0139] (Example 3) <Manufacturing of laminate 3 for photoelectric fusion substrate> In Example 1, a 1 mm thick glass plate was used instead of the polyimide film as the heat-resistant resin layer, and an underclad layer and a core layer were formed on the glass plate in the same manner as in Example 1. The obtained laminate was then immersed in 60°C hot water and peeled off from the glass plate. An insulating adhesive layer was laminated on the underclad layer side of the obtained two-layer laminate to manufacture a laminate 3 for photoelectric fusion substrate having the configuration shown in Figure 2.

[0140] (Example 4) <Manufacturing of laminate 4 for photoelectric fusion substrate> An overclad layer was formed on the core layer of the photoelectric fusion substrate laminate obtained in Example 3 using a photosensitive resin composition, similar to Example 3, to manufacture a laminate 4 for photoelectric fusion substrate having an overclad layer on the core layer of the laminate 2 for photoelectric fusion substrate.

[0141] As a result, it is possible to fuse optical waveguides while reducing the degradation of the electronic substrate, and the laminate for photoelectric fusion substrates and photoelectric fusion substrates can be applied, exhibiting excellent heat resistance, adhesion, and productivity.

[0142] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0143] This application claims priority based on Japanese Patent Application No. 2024-231623, filed on 27 December 2024, which is incorporated herein by reference to the entire contents of Japanese Patent Application No. 2024-231623.

[0144] 10 Core layer 11 Core layer with optical waveguide circuit pattern 20 Cladding layer 21 Undercladding layer 22 Overcladding layer 30 Insulating adhesive layer 40 Heat-resistant resin layer 100, 110, 200, 210 Laminate for photoelectric fusion substrate 300, 310, 400, 410 Laminate for photoelectric fusion substrate

Claims

1. The material comprises, in this order: a core layer made of a heat-resistant resin with an average thickness of 1 μm to 10 μm and a refractive index n1 at a wavelength of 1310 nm or 1550 nm; an underclad layer made of a heat-resistant resin with an average thickness of 5 μm to 25 μm and a refractive index n2 at a wavelength of 1310 nm or 1550 nm; and an insulating adhesive layer made of a thermosetting resin composition with an average thickness of 10 μm to 200 μm, wherein the volume resistivity of the insulating adhesive layer after curing is 10 ８ A laminate for photoelectric fusion substrates, characterized in that it has a refractive index of Ω·cm or more, and the refractive indices n1 and n2 satisfy the following relationship: 0.1 < 100 × (n1 - n2) / n1 < 5.

2. The laminate for photoelectric fusion substrate according to claim 1, further comprising a heat-resistant resin layer between the underclad layer and the insulating adhesive layer, the heat-resistant resin having an average thickness of 15 μm or more and a glass transition temperature of 150°C or higher.

3. The laminate for photoelectric fusion substrate according to claim 2, wherein the heat-resistant resin layer is made of polyimide resin.

4. The laminate for photoelectric fusion substrate according to any one of claims 1 to 3, wherein the core layer has an optical waveguide circuit pattern with a core diameter of 1 μm or more and 10 μm or less.

5. The laminate for photoelectric fusion substrate according to any one of claims 1 to 4, wherein the transmission loss of the core layer is 0.2 dB / cm or less.

6. The laminate for photoelectric fusion substrate according to any one of claims 1 to 5, wherein the coefficient of linear expansion of the undercladding layer is 80 ppm / K or less.

7. The laminate for a photoelectric fusion substrate according to any one of claims 1 to 6, wherein the thermosetting resin composition contains one or more selected from the group consisting of epoxy resin, epoxy / phenol resin, epoxy / cyanate resin, and epoxy / active ester resin.

8. The core layer is made of a first polyimide having a structural unit represented by the following general formula (1), and the underclad layer is made of a second polyimide having a structural unit represented by the following general formula (1). The laminate for an optoelectronic fusion substrate according to any one of claims 1 to 7. In the general formula (1), R １ is a tetravalent group selected from the group consisting of the following: In the general formula (1), R ２ is a divalent group selected from the group consisting of the following: R ｆ are each independently hydrogen or fluorine, X is each independently O, S, SO ２ , or C=O, Y is each independently O, S, SO ２ , or C=O. In the first polyimide, at least one R ｆ is hydrogen. In the first polyimide, the number of hydrogen atoms in R ｆ is N Ｈ , the number of fluorine atoms in R ｆ is N Ｆ , the fluorine substitution rate is f ｃｏｒｅ = N Ｆ / (N Ｈ + N Ｆ ). In the second polyimide, the number of hydrogen atoms in R ｆ is N Ｈ , the number of fluorine atoms in R ｆ is N Ｆ , the fluorine substitution rate is f ｃｌａｄ = N Ｆ / (N Ｈ + N Ｆ ). When the following formula: f ｃｌａｄ > f ｃｏｒｅ is satisfied.

9. The laminate for a photoelectric fusion substrate according to claim 4, further comprising an overclad layer on the underclad layer and the core layer, the overclad layer being made of a cured product of a photosensitive resin composition and having a refractive index n3 at a wavelength of 1310 nm or 1550 nm, wherein the average thickness of the overclad layer is 2 μm or more and 35 μm or less greater than the core diameter, and the refractive indices n1 and n3 satisfy the relationship: 0.1 < 100 × (n1 - n3) / n1 < 5.

10. A laminate for a photoelectric fusion substrate, comprising: an overcladding layer made of a cured product of a photosensitive resin composition and having a refractive index n3 at a wavelength of 1310 nm or 1550 nm; a core layer having an optical waveguide circuit pattern and made of a heat-resistant resin with a core diameter of 1 μm or more and a refractive index n1 at a wavelength of 1310 nm or 1550 nm; and an undercladding layer having an average thickness of 5 μm or more and a thermal refractive index n2 at a wavelength of 1310 nm or 1550 nm, wherein the average thickness of the overcladding layer is 2 μm or more and 35 μm greater than the core diameter; refractive indices n1 and n2 satisfy the relationship: 0.1 < 100 × (n1 - n2) / n1 < 5; and refractive indices n1 and n3 satisfy the relationship: 0.1 < 100 × (n1 - n3) / n1 < 5.

11. The laminate for photoelectric fusion substrate according to claim 10, further comprising a heat-resistant resin layer on the surface of the underclad layer opposite to the surface in contact with the core layer, the heat-resistant resin having an average thickness of 15 μm or more and a glass transition temperature of 150°C or more.

12. A photoelectric fusion substrate comprising an electronic substrate and a laminate for a photoelectric fusion substrate according to any one of claims 1 to 11, characterized in that the laminate for the photoelectric fusion substrate is fused to the electronic substrate.

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