Resin composition for optical waveguide, dry film using same, film with resin, liquid material, and optical waveguide

Abstract

This resin composition for an optical waveguide contains a low-refractive-index compound (A) having a refractive index of 1.52 or less and a high-refractive-index compound (B) having a refractive index of more than 1.52 and no more than 1.75, the low-refractive-index compound (A) includes at least one of an aliphatic epoxy compound, a silicon atom-containing epoxy compound and a fluorine atom-containing epoxy compound, the high-refractive-index compound (B) includes at least one of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound, the content of the high-refractive-index compound (B) is 7.5-55 parts by mass, and the value thereof calculated from the formula (Refractive index of low-refractive-index compound (A) × Content of low-refractive-index compound (A) + Refractive index of high-refractive-index compound (B) × Content of high-refractive-index compound (B)) / (Total content of low-refractive-index compound (A) and high-refractive-index compound (B)) is 1.52 or more and less than 1.60.

Description

Resin composition for optical waveguide, and dry film, resin-coated film, liquid material, and optical waveguide using the same

[0001] The present invention relates to a resin composition for optical waveguides, and to a dry film, a resin-coated film, a liquid material, and an optical waveguide using the same.

[0002] Optical fiber has traditionally been the mainstream transmission medium in the fields of FTTH (Fiber to the Home) and long-distance and medium-distance communications in the automotive field. In recent years, high-speed optical transmission over short distances of less than 1 meter has become necessary. In this area, optical waveguide-type optical wiring boards are suitable because they offer high-density wiring (narrow pitch, branching, crossing, multilayering, etc.), surface mountability, integration with electrical substrates, and small-diameter bending capabilities that are not possible with optical fiber.

[0003] An optical waveguide is obtained by forming a clad and a core using two types of ultraviolet (UV) curable optical waveguide resin compositions that are highly transparent and have different refractive indices. Generally, such optical waveguide resin compositions (hereinafter simply referred to as "resin compositions") contain a main resin, such as an epoxy resin, an acrylic resin, or a silicone resin, and a curing agent.

[0004] In recent years, optical fibers, planar waveguides, etc., with a high numerical aperture (NA) of about 0.2 to 0.4, calculated from the difference in refractive index between the core and cladding, have also come into use. The numerical aperture (hereinafter also simply referred to as "NA") is calculated using the formula: NA = ((refractive index of core layer) x (refractive index of core layer) - (refractive index of cladding layer) x (refractive index of cladding layer)). １／２ An optical waveguide connected to such a high NA optical fiber, high NA planar waveguide, or the like is similarly required to have a high NA of about 0.2 to 0.4 in order to suppress coupling loss.

[0005] Furthermore, increasing the refractive index difference between the core and the clad to design a high-NA optical waveguide can lead to the problem of delamination between the core layer and the clad layer. Regarding this delamination problem, for example, Patent Document 1 describes a curable resin composition containing 100 parts by mass of a fluorine-containing polymer (A) containing a specific fluorine-containing aromatic compound (X) and the like, 0.5 to 4 parts by mass of a polymerization initiator (B), and 3 to 20 parts by mass of a compound (C) having an isocyanurate skeleton. It is also described that this curable resin composition can suppress delamination of the core at the interface with the clad.

[0006] Japanese Patent Application Laid-Open No. 2021-134250

[0007] An object of the present invention is to provide a resin composition for optical waveguides that can be effectively used in designing high NA optical waveguides, can suppress optical loss at a wavelength of 1310 nm, and has heat resistance.

[0008] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention.

[0009] A resin composition for optical waveguides according to a first aspect of the present invention comprises a low refractive index compound (A) having a refractive index of 1.52 or less and a high refractive index compound (B) having a refractive index of more than 1.52 and less than 1.75, wherein the low refractive index compound (A) comprises at least one of an aliphatic epoxy compound, a silicon atom-containing epoxy compound, and a fluorine atom-containing epoxy compound, and the high refractive index compound (B) comprises at least one of a fluorene type epoxy compound, a biphenyl type epoxy compound, and a vinyl sulfide compound, the content of the high refractive index compound (B) is 7.5 parts by mass or more and 55 parts by mass or less per 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B), and a value calculated from the formula: (refractive index of the low refractive index compound (A) × content of the low refractive index compound (A) + refractive index of the high refractive index compound (B) × content of the high refractive index compound (B)) / (total content of the low refractive index compound (A) and the high refractive index compound (B)) is 1.52 or more and less than 1.60.

[0010] FIG. 1 is a cross-sectional view illustrating an example of a method for forming an optical waveguide using the dry film according to the present embodiment. Specifically, FIG. 1( a) is a schematic view illustrating a step in which a clad dry film is laminated onto a surface of a substrate. FIG. 1( b) is a schematic view illustrating a step in which an underclad is formed. FIG. 1( c) is a schematic view illustrating a step in which a core dry film is exposed with a core pattern. FIG. 1( d) is a schematic view illustrating a step in which a core is formed on the surface of the underclad. FIG. 1( e) is a schematic view illustrating a step in which a clad dry film is laminated to cover the underclad and the core. FIG. 1( f) is a schematic view illustrating a step in which an optical waveguide is formed.

[0011] As mentioned above, there is a demand for optical waveguides with a high NA of approximately 0.2 to 0.4. However, it is known that simply forming a core using a material with a high refractive index for the purpose of designing a high NA optical waveguide leads to an increase in optical loss at a wavelength of 1310 nm. Therefore, from the important perspective of suppressing optical loss at a wavelength of 1310 nm, there have not been many reports to date of resin compositions for optical waveguides that are well suited to the design of high NA optical waveguides.

[0012] For example, it is expected that the NA of a curable resin composition disclosed in Patent Document 1, which primarily contains 100 parts by mass of a fluorine-containing polymer (A) and 3 to 20 parts by mass of a compound (C) having an isocyanurate skeleton, can only be increased to approximately 0.12. Specifically, considering application to the design of high-NA optical waveguides, it is necessary to further increase only the content of the compound (C) having an isocyanurate skeleton in the curable resin composition described in Patent Document 1. However, increasing only the content of the compound (C) having an isocyanurate skeleton leads to significant optical loss. Therefore, such content adjustment is usually not possible. Therefore, it would be preferable to obtain a resin composition that can be effectively applied to the design of high-NA optical waveguides while suppressing optical loss.

[0013] In addition, in an optical waveguide type optical wiring board, in order to utilize light input / output from the optical waveguide, an electric circuit is also formed on the substrate on which the optical waveguide is formed, and for example, a light emitting element, a photoelectric conversion element, a semiconductor element, etc. are preferably mounted. When an electric circuit is formed on the substrate, the substrate is subjected to a reflow treatment using, for example, lead-free solder. Since such a reflow treatment is performed at high temperatures, it is preferable that the resin composition for the optical waveguide has heat resistance.

[0014] As a result of intensive research by the present inventors, it has been found that a resin composition for optical waveguides can be obtained that is well used in designing high NA optical waveguides, can suppress optical loss at a wavelength of 1310 nm, and has heat resistance, by containing one or more low refractive index compounds (A) and one or more high refractive index compounds (B), each selected from a predetermined group of compounds, and the content of the high refractive index compound (B) is within a predetermined range, and the value calculated from a predetermined formula using the refractive index and content of the low refractive index compound (A) and the refractive index and content of the high refractive index compound (B) is within a predetermined range.

[0015] As described above, according to the present invention, it is possible to provide a resin composition for optical waveguides which can be effectively used in designing high NA optical waveguides, can suppress optical loss at a wavelength of 1310 nm, and has heat resistance.

[0016] In this specification, the terms "compound," "low refractive index compound (A) (specifically, one type of low refractive index compound (A))," "high refractive index compound (B) (specifically, one type of high refractive index compound (B))," and "epoxy compound" refer to a concept that includes both a resin, a low refractive index resin, a high refractive index resin, or an epoxy resin as a polymer, and a monomer that can form the resin, the low refractive index resin, the high refractive index resin, or the epoxy resin.

[0017] In this specification, the terms "refractive index of a compound," "refractive index of a low refractive index compound (A) (specifically, the refractive index of one type of low refractive index compound (A))," and "refractive index of a high refractive index compound (B) (specifically, the refractive index of one type of high refractive index compound (B))" refer to the refractive index at a temperature of 25°C and a wavelength of 1,310 nm measured with an Abbe refractometer when an appropriate amount of a curing agent is added to each compound to form a cured product.

[0018] In this specification, by using the values ​​of such "refractive index of the low refractive index compound (A)" and "refractive index of the high / low refractive index compound (B)", a value calculated from the formula: (refractive index of the low refractive index compound (A) × content of the low refractive index compound (A) + refractive index of the high refractive index compound (B) × content of the high refractive index compound (B)) / (total content of the low refractive index compound (A) and the high refractive index compound (B)) is obtained. Hereinafter, this formula is also referred to as "the relationship formula between the refractive index and the content of this embodiment" or simply "the relationship formula between the refractive index and the content".

[0019] Here, when the resin composition for optical waveguides according to this embodiment contains two or more types of low refractive index compounds (A) as the low refractive index compound (A), the "refractive index of the low refractive index compound (A) x content of the low refractive index compound (A)" in the above-described relationship between the refractive index and content according to this embodiment means the sum of the multiplied values ​​of the refractive index and content of each low refractive index compound (A).

[0020] For example, the resin composition for an optical waveguide may contain the low refractive index compound (A) １ and a low refractive index compound (A) ２ and a low refractive index compound (A) ３ When the low refractive index compound (A) is contained, the relationship between the refractive index and the content in this embodiment is represented by the following formula 1. Formula 1: [(low refractive index compound (A) １ refractive index × low refractive index compound (A) １ + content of low refractive index compound (A) ２ refractive index × low refractive index compound (A) ２ + content of low refractive index compound (A) ３ refractive index × low refractive index compound (A) ３(content of high refractive index compound (B)) + (refractive index of high refractive index compound (B) × content of high refractive index compound (B)) / (low refractive index compound (A) １ , (A) ２ and (A) ３ and the high refractive index compound (B)

[0021] Similarly, when the resin composition for optical waveguide according to this embodiment contains two or more types of high refractive index compounds (B) as the high refractive index compound (B), the "refractive index of the high refractive index compound (B) x content of the high refractive index compound (B)" in the above-described relationship between the refractive index and content of this embodiment means the sum of the multiplied values ​​of the refractive index and content of each high refractive index compound (B).

[0022] For example, the resin composition for an optical waveguide may contain the high refractive index compound (B) １ and a high refractive index compound (B) ２ and a high refractive index compound (B) ３ When the composition contains the compound (B), the relationship between the refractive index and the content of the compound (B) is expressed by the following formula 2: [(refractive index of the compound (A) × content of the compound (A)) + (high refractive index compound (B))] １ Refractive index of the high refractive index compound (B) × １ + content of high refractive index compound (B) ２ Refractive index of the high refractive index compound (B) × ２ + content of high refractive index compound (B) ３ Refractive index of the high refractive index compound (B) × ３ (content of low refractive index compound (A) and high refractive index compound (B)) １ , (B) ２ and (B) ３ (total content of

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0024] 1. Resin Composition for Optical Waveguide The resin composition for optical waveguide according to this embodiment (hereinafter also simply referred to as "resin composition") contains a low refractive index compound (A) having a refractive index of 1.52 or less and a high refractive index compound (B) having a refractive index of more than 1.52 and 1.75 or less.

[0025] Hereinafter, the components contained in the resin composition and the values ​​calculated from the relational expression between the refractive index and the content in this embodiment will be described in detail.

[0026] [Low Refractive Index Compound (A)] The low refractive index compound (A) is not particularly limited as long as it is a compound having a refractive index of 1.52 or less that is generally used as a resin for optical waveguides, and includes at least one of an aliphatic epoxy compound, a silicon atom-containing epoxy compound (hereinafter also referred to as an "Si-containing epoxy compound"), and a fluorine atom-containing epoxy compound (hereinafter also referred to as an "F-containing epoxy compound").

[0027] In the resin composition according to the present embodiment, the low refractive index compound (A) may contain another low refractive index compound (A) other than the above. From the viewpoints of heat resistance and optical signal transmittance, the other low refractive index compound (A) is preferably an epoxy compound.

[0028] As used herein, the term "epoxy compound" includes both liquid and solid epoxy compounds. As used herein, with respect to an epoxy compound, "liquid" means that the epoxy compound is in a liquid state at room temperature, and "solid" means that the epoxy compound is in a solid state at room temperature.

[0029] These low refractive index compounds (A) will be described in detail below.

[0030] (Aliphatic Epoxy Compound) When the low refractive index compound (A) contains an aliphatic epoxy compound, it is possible to prevent the value calculated from the relationship between the refractive index and the content of this embodiment from becoming excessively large. Furthermore, when the low refractive index compound (A) contains an aliphatic epoxy compound, while satisfying the type and content of the high refractive index compound (B) according to this embodiment and the conditions of the relationship between the refractive index and the content of this embodiment, it is possible to obtain a resin composition having the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment.

[0031] The aliphatic epoxy compound may be either a solid aliphatic epoxy compound or a liquid aliphatic epoxy compound, but from the viewpoint of heat resistance, a solid aliphatic epoxy compound is preferred.

[0032] The aliphatic epoxy compound preferably has two or more epoxy groups in the molecule and two or more cyclohexane groups. When the low refractive index compound (A) contains such an aliphatic epoxy compound, the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment can be reliably obtained, while the type and content of the high refractive index compound (B) according to this embodiment and the conditions of the relationship between the refractive index and the content according to this embodiment are satisfied.

[0033] Such an aliphatic epoxy compound is not particularly limited, but an example thereof is a hydrogenated bisphenol A epoxy compound. When the resin composition contains a hydrogenated bisphenol A epoxy compound after satisfying the type and content of the high refractive index compound (B) according to this embodiment and the conditions of the relationship between the refractive index and the content according to this embodiment, the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment can be more reliably obtained.

[0034] The hydrogenated bisphenol A epoxy compound may be synthesized by a known method, or a commercially available product may be used. Examples of commercially available hydrogenated bisphenol A epoxy compounds include "YX8040" and "YX8034" manufactured by Mitsubishi Chemical Corporation, "ST-4000" manufactured by Nippon Steel Chemical & Material Co., Ltd., and "EP-4080E" manufactured by ADEKA Corporation.

[0035] The aliphatic epoxy compounds may be used alone or in combination of two or more.

[0036] The refractive index of the aliphatic epoxy compound is not particularly limited as long as it satisfies the conditions of the relational expression between the refractive index and the content of this embodiment, but is preferably 1.45 or more and 1.55 or less, more preferably 1.45 or more and 1.53 or less, and even more preferably 1.45 or more and 1.51 or less.

[0037] When the low refractive index compound (A) contains an aliphatic epoxy compound, the content of the aliphatic epoxy compound is not particularly limited as long as it satisfies the content of the high refractive index compound (B) according to this embodiment and the conditions of the relationship between the refractive index and the content according to this embodiment. Specifically, the content of the aliphatic epoxy compound must also take into account the content of the low refractive index compound (A) other than the aliphatic epoxy compound contained in the resin composition, but it may be 45 parts by mass or more and 92.5 parts by mass or less per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B). Furthermore, the content of the aliphatic epoxy compound is preferably 50 parts by mass or more and 90 parts by mass or less, more preferably 50 parts by mass or more and 80 parts by mass or less, per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B).

[0038] (Si-containing epoxy compound) When the low refractive index compound (A) contains a Si-containing epoxy compound, the value calculated from the relationship between the refractive index and the content of this embodiment can be prevented from becoming excessively large. Furthermore, when the low refractive index compound (A) contains a Si-containing epoxy compound, and the type and content of the high refractive index compound (B) according to this embodiment and the conditions of the relationship between the refractive index and the content of this embodiment are satisfied, a resin composition having the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment can be obtained.

[0039] The Si-containing epoxy compound is generally used as a resin for optical waveguides, and is not particularly limited as long as it is an epoxy compound containing a Si atom in its monomer structure, but is preferably a liquid Si-containing epoxy compound.

[0040] The Si-containing epoxy compound preferably has two or more epoxy groups in the molecule, and the silicon atom content per molecular weight is 10% by mass or more and 50% by mass or less. When the low refractive index compound (A) contains such a Si-containing epoxy compound, the effects of the high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment can be reliably obtained, while the type and content of the high refractive index compound (B) according to this embodiment and the relationship between the refractive index and the content are satisfied.

[0041] Such Si-containing epoxy compounds may be synthesized by known methods, or commercially available products may be used, such as "KR-470", "X-22-163", "X-40-2728", "X-40-2669", and "X-40-2678" manufactured by Shin-Etsu Chemical Co., Ltd., and "OX-SQ" manufactured by Toagosei Co., Ltd.

[0042] The Si-containing epoxy compounds may be used alone or in combination of two or more.

[0043] The refractive index of the Si-containing epoxy compound is not particularly limited as long as it satisfies the conditions of the relationship between the refractive index and the content of this embodiment, but is preferably 1.45 or more and 1.55 or less, more preferably 1.45 or more and 1.53 or less, and even more preferably 1.45 or more and 1.51 or less.

[0044] When the low refractive index compound (A) contains a Si-containing epoxy compound, the content of the Si-containing epoxy compound is not particularly limited as long as it satisfies the conditions of the content of the high refractive index compound (B) according to this embodiment and the relationship between the refractive index and the content. Specifically, the content of the Si-containing epoxy compound must also take into account the content of the low refractive index compound (A) other than the Si-containing epoxy compound contained in the resin composition, but it may be 45 parts by mass or more and 92.5 parts by mass or less per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B). In addition, the content of the Si-containing epoxy compound is preferably 47.5 parts by mass or more and 80 parts by mass or less, more preferably 50 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B).

[0045] (F-Containing Epoxy Compound) When the low refractive index compound (A) contains an F-containing epoxy compound, it is possible to prevent the value calculated from the relationship between the refractive index and the content of this embodiment from becoming excessively large. Furthermore, when the low refractive index compound (A) contains an F-containing epoxy compound while satisfying the conditions of the type and content of the high refractive index compound (B) according to this embodiment and the relationship between the refractive index and the content, it is possible to obtain a resin composition having the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment.

[0046] The F-containing epoxy compound is not particularly limited as long as it is an epoxy compound containing a fluorine atom that is generally used as a resin for an optical waveguide.

[0047] The F-containing epoxy compound preferably has two or more epoxy groups in the molecule and a fluorine atom content of 10% by mass to 50% by mass per molecular weight. When the low refractive index compound (A) contains such an F-containing epoxy compound while satisfying the conditions of the type and content of the high refractive index compound (B) according to this embodiment and the relationship between the refractive index and the content, the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment can be reliably obtained.

[0048] Examples of such F-containing epoxy compounds include bisphenol AF epoxy compounds, hydrogenated bisphenol AF epoxy compounds, and fluorine-containing alicyclic epoxy compounds. Of these, the resin composition preferably contains a bisphenol AF epoxy compound. When the resin composition contains a bisphenol AF epoxy compound while satisfying the conditions of the type and content of the high refractive index compound (B) according to this embodiment and the relationship between the refractive index and the content, the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment can be more reliably achieved.

[0049] The bisphenol AF epoxy compound may be synthesized by a known method, or a commercially available product may be used. For example, the commercially available bisphenol AF epoxy compound is not particularly limited, but an example thereof is "YX7760" manufactured by Mitsubishi Chemical Corporation.

[0050] The F-containing epoxy compounds may be used alone or in combination of two or more.

[0051] The refractive index of the F-containing epoxy compound is not particularly limited as long as it satisfies the conditions of the relationship between the refractive index and the content of this embodiment, but is preferably 1.45 or more and 1.55 or less, more preferably 1.45 or more and 1.53 or less, and even more preferably 1.45 or more and 1.51 or less.

[0052] When the low refractive index compound (A) contains an F-containing epoxy compound, the content of the F-containing epoxy compound is not particularly limited as long as it satisfies the conditions of the content of the high refractive index compound (B) according to this embodiment and the relationship between the refractive index and the content. Specifically, the content of the F-containing epoxy compound must also take into account the content of the low refractive index compound (A) other than the F-containing epoxy compound contained in the resin composition, but it may be 45 parts by mass or more and 92.5 parts by mass or less per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B). Furthermore, the content of the F-containing epoxy compound is preferably 47.5 parts by mass or more and 91 parts by mass or less, more preferably 50 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B).

[0053] (Other Low Refractive Index Compounds (A)) In the resin composition according to this embodiment, the low refractive index compound (A) may further include an epoxy compound other than an aliphatic epoxy compound, a Si-containing epoxy compound, or an F-containing epoxy compound, the epoxy compound having a refractive index of 1.52 or less.

[0054] Such other low refractive index compounds (A) are not particularly limited, but examples thereof include alicyclic epoxy compounds.

[0055] These other low refractive index compounds (A) may be used singly or in combination of two or more.

[0056] When the low refractive index compound (A) contains such other low refractive index compounds (A), the content of the other low refractive index compounds (A) (when two or more other low refractive index compounds (A) are contained, the total content thereof) may be an amount that satisfies the content of the high refractive index compound (B) according to this embodiment and the conditions of the relationship between the refractive index and the content according to this embodiment, and does not impair the effects of the high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment. For example, the content of the other low refractive index compounds (A) may be approximately 10 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B).

[0057] (Content of Low Refractive Index Compound (A)) The content of the low refractive index compound (A) (when two or more types of low refractive index compounds (A) are contained, the total content thereof) is also not particularly limited as long as the content of the high refractive index compound (B) according to this embodiment and the condition of the relationship between the refractive index and the content according to this embodiment are satisfied.

[0058] Specifically, the content of the low refractive index compound (A), which contains at least one of an aliphatic epoxy compound, a Si-containing epoxy compound, and an F-containing epoxy compound, may be 45 parts by mass or more and 92.5 parts by mass or less, relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B). The content of the low refractive index compound (A) is preferably 47.5 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more. The content of the low refractive index compound (A) is preferably 90 parts by mass or less, preferably 80 parts by mass or less, and more preferably 70 parts by mass or less.

[0059] [High Refractive Index Compound (B)] The high refractive index compound (B) is not particularly limited as long as it is a compound commonly used as a resin for optical waveguides and has a refractive index greater than 1.52 and not greater than 1.75, and includes at least one of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound. By including at least one of these compounds in the resin composition, optical loss at a wavelength of 1310 nm can be suppressed and heat resistance can be achieved, even when an optical waveguide with a high NA of approximately 0.2 to 0.4 is designed using the resin composition.

[0060] In the resin composition according to the present embodiment, the high refractive index compound (B) may contain other high refractive index compounds (B) other than those mentioned above. From the viewpoints of heat resistance and optical signal transmittance, the other high refractive index compounds (B) are preferably epoxy compounds.

[0061] These high refractive index compounds (B) will be described in detail below.

[0062] (Fluorene-type epoxy compound) When the high refractive index compound (B) contains a fluorene-type epoxy compound, the value calculated from the relationship between the refractive index and the content of this embodiment can be increased. In addition, the optical loss at a wavelength of 1310 nm of the resin composition can be suppressed, and the heat resistance of the resin composition can be improved. Therefore, when the type of low refractive index compound (A) according to this embodiment, the content of the high refractive index compound (B), and the conditions of the relationship between the refractive index and the content of this embodiment are satisfied, and the high refractive index compound (B) contains a fluorene-type epoxy compound, a resin composition having the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment can be obtained.

[0063] Fluorene-type epoxy compounds are generally used as resins for optical waveguides, and are not particularly limited as long as they are fluorene-type epoxy compounds (fluorene-type epoxy resins) having a fluorene skeleton in their monomer structure. The fluorene-type epoxy compound may be either a liquid fluorene-type epoxy compound or a solid fluorene-type epoxy compound.

[0064] The fluorene-type epoxy compound is not particularly limited, but an example thereof is a fluorene-type epoxy compound having a monomer structure represented by the following structural formula (1). [In formula (1), R １ ~R ４ are hydrogen atoms or alkyl groups having 1 to 6 carbon atoms, and may be the same or different. ５ and R ６ are hydrogen atoms or methyl groups and may be the same or different. Each n is independently an integer of 0 to 10.

[0065] The fluorene-type epoxy compound may be synthesized by a known method, or a commercially available product may be used. Examples of commercially available liquid fluorene-type epoxy compounds include "OGSOL-EG200" and "OGSOL-EG280" manufactured by Osaka Gas Chemicals Co., Ltd. Examples of commercially available solid fluorene-type epoxy compounds include "OGSOL-PG100" and "OGSOL-CG500" manufactured by Osaka Gas Chemicals Co., Ltd.

[0066] The fluorene-type epoxy compounds may be used alone or in combination of two or more.

[0067] The refractive index of the fluorene-type epoxy compound is not particularly limited as long as it satisfies the conditions of the relationship between the refractive index and the content of this embodiment, but is preferably 1.55 or more and 1.75 or less, more preferably 1.58 or more and 1.70 or less, and even more preferably 1.60 or more and 1.66 or less.

[0068] When the high refractive index compound (B) comprises a fluorene-type epoxy compound, the content of the fluorene-type epoxy compound is not particularly limited, as long as it satisfies the conditions of the content of the high refractive index compound (B) according to this embodiment and the relationship between the refractive index and the content.Specifically, the content of the fluorene-type epoxy compound needs to consider the content of the high refractive index compound (B) other than the fluorene-type epoxy compound contained in the resin composition, but it is sufficient that it is 7.5 parts by mass or more and 55 parts by mass or less relative to the total 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B).In addition, the content of the fluorene-type epoxy compound is preferably 9 parts by mass or more and 50 parts by mass or less, more preferably 10 parts by mass or more and 40 parts by mass or less relative to the total 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B).

[0069] (Biphenyl-type epoxy compound) When the high refractive index compound (B) contains a biphenyl-type epoxy compound, the value calculated from the relationship between the refractive index and the content of this embodiment can be increased. In addition, the optical loss at a wavelength of 1310 nm of the resin composition can be suppressed, and the heat resistance of the resin composition can be improved. Therefore, when the high refractive index compound (B) contains a biphenyl-type epoxy compound, and the conditions of the type of low refractive index compound (A), the content of the high refractive index compound (B), and the relationship between the refractive index and the content of this embodiment are satisfied, a resin composition having the effects of high NA optical waveguide design, optical loss suppression, and heat resistance of this embodiment can be obtained.

[0070] Biphenyl-type epoxy compounds are generally used as resins for optical waveguides, and are not particularly limited as long as they are biphenyl-type epoxy compounds (biphenyl-type epoxy resins) having a biphenyl skeleton in their monomer structure.

[0071] The biphenyl type epoxy compound may be synthesized by a known method, or a commercially available product may be used. Examples of commercially available biphenyl type epoxy compounds include "NC-3000", "NC-3000-H", "NC-3000-L", and "NC-3100" manufactured by Nippon Kayaku Co., Ltd., and "YX4000", "YX4000H", and "YL6121" manufactured by Mitsubishi Chemical Corporation.

[0072] The biphenyl type epoxy compounds may be used alone or in combination of two or more.

[0073] The refractive index of the biphenyl-type epoxy compound is not particularly limited as long as it satisfies the conditions of the relationship between the refractive index and the content of this embodiment, but is preferably 1.55 or more and 1.75 or less, more preferably 1.60 or more and 1.70 or less, and even more preferably 1.60 or more and 1.65 or less.

[0074] When the high refractive index compound (B) contains a biphenyl-type epoxy compound, the content of the biphenyl-type epoxy compound is not particularly limited as long as the content of the high refractive index compound (B) according to this embodiment and the conditions of the relationship between the refractive index and the content are satisfied. Specifically, the content of the biphenyl-type epoxy compound must also take into account the content of the high refractive index compound (B) other than the biphenyl-type epoxy compound contained in the resin composition, but it may be 7.5 parts by mass or more and 55 parts by mass or less per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B). Furthermore, the content of the biphenyl-type epoxy compound is preferably 30 parts by mass or more and 53 parts by mass or less, more preferably 40 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B).

[0075] (Vinyl sulfide compound) When the high refractive index compound (B) contains a vinyl sulfide compound, the value calculated from the relationship between the refractive index and the content of this embodiment can be increased. In addition, the optical loss at a wavelength of 1310 nm of the resin composition can be suppressed, and the heat resistance of the resin composition can be improved. Therefore, when the high refractive index compound (B) contains a vinyl sulfide compound after satisfying the conditions of the type of low refractive index compound (A) according to this embodiment, the content of the high refractive index compound (B), and the relationship between the refractive index and the content of this embodiment, a resin composition having the effects of high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment can be obtained.

[0076] The vinyl sulfide compound is not particularly limited as long as it is a vinyl sulfide compound that is generally used as a resin for optical waveguides.

[0077] Examples of such vinyl sulfide compounds include bis(4-vinylthiophenyl) sulfide, bis(3-methyl-4-vinylthiophenyl) sulfide, bis(3,5-dimethyl-4-vinylthiophenyl) sulfide, bis(2,3,5,6-tetramethyl-4-vinylthiophenyl) sulfide, bis(3-hexyl-4-vinylthiophenyl) sulfide, bis(3,5-dihexyl-4-vinylthiophenyl) sulfide, bis(3-chloro-4-vinylthiophenyl) sulfide, bis(3,5-dichloro-4-vinylthiophenyl) sulfide, bis(2,3,5,6-tetrachloro-4-vinylthiophenyl) sulfide, bis(3-bromo-4-vinylthiophenyl) sulfide, bis(3,5-dibromo-4-vinylthiophenyl) sulfide, and bis(2,3,5,6-tetrabromo-4-vinylthiophenyl) sulfide. Of these, the vinyl sulfide compound preferably contains one or more compounds selected from the group consisting of bis(4-vinylthiophenyl) sulfide, bis(3-methyl-4-vinylthiophenyl) sulfide, and bis(3,5-dimethyl-4-vinylthiophenyl) sulfide. Furthermore, of these, the vinyl sulfide compound more preferably contains bis(4-vinylthiophenyl) sulfide.

[0078] The vinyl sulfide compound may be synthesized by a known method, or a commercially available product may be used. The commercially available vinyl sulfide compound is not particularly limited, but an example thereof is "MPV" manufactured by Sumitomo Seika Chemicals Co., Ltd.

[0079] The vinyl sulfide compounds may be used alone or in combination of two or more.

[0080] The refractive index of the vinyl sulfide compound is not particularly limited as long as it satisfies the condition of the relational expression between the refractive index and the content of this embodiment; however, it is preferably 1.55 or more and 1.75 or less, more preferably 1.60 or more and 1.74 or less, and even more preferably 1.65 or more and 1.73 or less.

[0081] When the high refractive index compound (B) contains a vinyl sulfide compound, the content of the vinyl sulfide compound is not particularly limited as long as the content of the high refractive index compound (B) according to this embodiment and the conditions of the relationship between the refractive index and the content are satisfied. Specifically, the content of the vinyl sulfide compound must also take into account the content of the high refractive index compound (B) other than the vinyl sulfide compound contained in the resin composition, but it may be 7.5 parts by mass or more and 55 parts by mass or less per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B). Furthermore, the content of the vinyl sulfide compound is preferably 8 parts by mass or more and 30 parts by mass or less, more preferably 8.5 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the low refractive index compound (A) and the high refractive index compound (B).

[0082] (Other High Refractive Index Compounds (B)) In the resin composition according to this embodiment, the high refractive index compound (B) may further include an epoxy compound other than a fluorene-containing epoxy compound and a biphenyl-containing epoxy compound, the refractive index of which is greater than 1.52 and less than 1.75. In this case, the refractive index of the other high refractive index compound (B) is preferably greater than 1.52 and less than 1.58.

[0083] Such other high refractive index compounds (B) are not particularly limited, but examples thereof include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, polyfunctional epoxy compounds, bisphenol E type epoxy compounds, brominated epoxy compounds, aromatic epoxy compounds, novolac type epoxy compounds, and alicyclic epoxy compounds.

[0084] These other high refractive index compounds (B) may be used singly or in combination of two or more.

[0085] From the viewpoints of high transparency and ease of UV curing, the resin composition preferably contains, as the other high refractive index compound (B), a bisphenol A type epoxy compound having a refractive index of more than 1.52 and less than 1.58. The epoxy equivalent of the bisphenol A type epoxy compound is not particularly limited, but is preferably, for example, about 170 g / eq to 1200 g / eq.

[0086] The bisphenol A epoxy compound may be synthesized by a known method, or a commercially available product may be used. For example, commercially available solid bisphenol A epoxy resins include "1001," "1002," "1003," "1055," "1004," "1004AF," "1003F," "1004F," "1005F," "1004FS," "1006FS," and "1007FS" manufactured by Mitsubishi Chemical Group Corporation. Furthermore, commercially available liquid bisphenol A epoxy resins include "Epiclon (registered trademark) 850S" manufactured by DIC Corporation and "JER (registered trademark) 825" manufactured by Mitsubishi Chemical Corporation.

[0087] When the high refractive index compound (B) contains such other high refractive index compounds (B), the content of the other high refractive index compounds (B) (when two or more other high refractive index compounds (B) are contained, the total content thereof) may be any amount that satisfies the conditions of the content of the high refractive index compound (B) according to this embodiment and the relationship between the refractive index and the content, and does not impair the effects of the high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment. For example, the content of the other high refractive index compounds (B) is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 45 parts by mass or less, even more preferably 10 parts by mass or more and 43 parts by mass or less, and particularly preferably 20 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B).

[0088] (Content of high refractive index compound (B)) In the resin composition according to this embodiment, the content of the high refractive index compound (B) (when two or more types of high refractive index compounds (B) are contained, the total content thereof) is 7.5 parts by mass or more and 55 parts by mass or less per 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B).

[0089] Specifically, the content of the high refractive index compound (B) containing at least one of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound needs to be adjusted within a range of 7.5 parts by mass or more and 55 parts by mass or less so as to satisfy the condition of the relationship between the refractive index and the content of this embodiment.

[0090] When the content of the high refractive index compound (B) is 7.5 parts by mass or more relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B), the value calculated from the relationship between the refractive index and the content can be increased, and a resin composition that can be suitably used in the design of high NA optical waveguides can be obtained. When the content of the high refractive index compound (B) is 55 parts by mass or less relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B), the value calculated from the relationship between the refractive index and the content can be prevented from becoming excessively large, and a resin composition that can be suitably used in the design of high NA optical waveguides can be obtained.

[0091] The content of the high refractive index compound (B) is preferably 8 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 20 parts by mass or more, relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B). The content of the high refractive index compound (B) is preferably 53 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less, and particularly preferably 40 parts by mass or less, relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B).

[0092] [Value Calculated from Relationship Between Refractive Index and Content] In the resin composition according to this embodiment, the value calculated from the formula: (Refractive index of low refractive index compound (A) × Content of low refractive index compound (A) + Refractive index of high refractive index compound (B) × Content of high refractive index compound (B)) / (Total content of low refractive index compound (A) and high refractive index compound (B)) is 1.52 or more and less than 1.60.

[0093] Specifically, the value calculated from the relational expression between the refractive index and the content needs to be adjusted within the range of 1.52 or more and less than 1.60 so as to satisfy the content condition of the high refractive index compound (B) containing at least one of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound according to this embodiment.

[0094] When the value calculated from the relational expression between the refractive index and the content is within this range, the resin composition can be used to form a core and can be suitably used in designing an optical waveguide with a high NA of about 0.2 to 0.4.

[0095] The value calculated from the relational expression between the refractive index and the content is preferably 1.53 or more, more preferably 1.54 or more, and even more preferably 1.55 or more. The value calculated from the relational expression between the refractive index and the content is preferably 1.58 or less, more preferably 1.57 or less, and even more preferably 1.56 or less.

[0096] [Cationic Curing Catalyst (C)] The resin composition according to the present embodiment preferably further contains a cationic curing catalyst (C). By containing the cationic curing catalyst (C) in the resin composition, it is possible to improve the patterning properties. The type of cationic curing catalyst (C) is not particularly limited as long as it can promote the photocuring of the resin composition containing the low refractive index compound (A) and the high refractive index compound (B) described above.

[0097] The cationic curing catalyst (C) may be, for example, a polymerization initiator that causes ring-opening polymerization of the epoxy group of the epoxy compound of the low refractive index compound (A) and the high refractive index compound (B). An example of the polymerization initiator is a photoacid generator that can initiate a reaction by light such as ultraviolet light.

[0098] Specific examples of the cationic curing catalyst (C) include antimony-based curing agents, gallate-based curing agents, phosphorus-based curing agents, special phosphorus-based curing agents, and borate-based curing agents. Commercially available products can be used as these curing agents. Examples of commercially available curing agents include "CPI-101A" manufactured by San-Apro Co., Ltd., which is an antimony-based curing agent, "CPI-310FG" manufactured by San-Apro Co., Ltd., and "SP-170" manufactured by ADEKA Corporation, which are gallate-based curing agents. These curing agents may be used alone or in combination of two or more.

[0099] The content of the cationic curing catalyst (C) is not particularly limited as long as it does not impair the effects of the high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment. For example, the content of the cationic curing catalyst (C) is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 0.15% by mass or more and 3% by mass or less, and even more preferably 0.2% by mass or more and 2% by mass or less, relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B).

[0100] [Other Additives] In addition to the components described above, the resin composition may further contain other additives such as antioxidants, leveling agents, coupling agents (silane coupling agents), flame retardants, and inorganic fillers, as long as the effects of the high NA optical waveguide design, optical loss suppression, and heat resistance according to this embodiment are not impaired.

[0101] In particular, from the viewpoint of improving the heat resistance of the optical waveguide, it is preferable that the resin composition further contains an antioxidant. The antioxidant is not particularly limited, and phenol-based antioxidants, phosphite-based antioxidants, sulfur-based antioxidants, etc. can be used. Of these, the antioxidant is preferably a phenol-based antioxidant.

[0102] Commercially available phenolic antioxidants can be used, such as "AO-20," "AO-30," "AO-40," "AO-50," "AO-60," and "AO-80" manufactured by Adeka Corporation, and "SUMILIZER GA-80" manufactured by Sumitomo Chemical Co., Ltd.

[0103] The content of the antioxidant is not particularly limited, but is preferably (0 mass % or more) 5 mass % or less, and more preferably (0 mass % or more) 1 mass % or less, relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B).

[0104]

[0033] In this way, the resin composition for an optical waveguide according to this embodiment can be suitably used in the design of a high-NA optical waveguide, can suppress optical loss at a wavelength of 1310 nm, and has heat resistance. From the viewpoint that a higher refractive index is required for the core layer compared to the cladding layer, and that optical loss at a wavelength of 1310 nm occurs mainly in the core layer, the resin composition for an optical waveguide according to this embodiment can be suitably used, for example, as a material for a dry film for the core when manufacturing a high-NA optical waveguide on which electric circuits, optical elements, etc. are mounted.

[0105] 2. Dry Film and Resin-Coated Film The dry film according to this embodiment is not particularly limited as long as it includes a layer made of the resin composition for an optical waveguide according to the above-described embodiment. Specifically, the dry film includes a layer made of an uncured product of the resin composition for an optical waveguide according to the above-described embodiment or a semi-cured product of the resin composition for an optical waveguide according to the above-described embodiment (hereinafter also referred to as an "optical waveguide resin composition layer" or "resin composition layer").

[0106] In this specification, the term "semi-cured product" refers to a cured product that has been produced by applying a liquid material containing a resin composition in a varnish form as described below, followed by heating at an appropriate temperature and time as necessary, drying, and irradiation with light such as ultraviolet light, reducing or removing the solvent, and partially curing the resin. In other words, the term "semi-cured product" refers to a resin composition that is in a state where further curing can proceed.

[0107] In this specification, the term "uncured product" refers to a resin composition that has been heated and dried at an appropriate temperature and for an appropriate time as necessary, and in which the solvent and the like have been reduced or removed, and in which curing of the resin has not yet progressed.

[0108] In this specification, the term "cured product" refers to a resin layer in which the curing reaction of an uncured or semi-cured resin composition layer is promoted by irradiation with light such as ultraviolet light, causing the resin to crosslink, and thus the resin layer does not melt even when heated. The optical waveguide according to the embodiment described below includes a core layer that is a cured product of the resin composition for an optical waveguide.

[0109] The resin-supported film according to this embodiment includes a layer containing an uncured product of the resin composition for optical waveguides according to the above-described embodiment or a semi-cured product of the resin composition for optical waveguides according to the above-described embodiment, and a support film. That is, the resin-supported film is a film having a support film on at least one surface of the above-described dry film layer. Furthermore, the resin-supported film may have a protective film laminated on the other surface of the layer. The resin-supported film may also include other layers in addition to the layer, the support film, and an optional protective film.

[0110] The support film is not particularly limited, but examples thereof include polyethylene terephthalate (PET) film, biaxially oriented polypropylene film, polyethylene naphthalate film, polyimide film, etc. Among these, PET film is preferable. The protective film is not particularly limited, but examples thereof include polypropylene film, etc.

[0111] Methods for producing dry films and resin-attached films are not particularly limited, but include, for example, the following methods. First, a varnish-like liquid material containing the resin composition according to the above-described embodiment is prepared by adding a solvent or the like as needed. Next, the prepared liquid material is applied to a film substrate or a support film. This application can be performed using a comma coater or the like. The applied liquid material is then heated and dried at an appropriate temperature and time, and if necessary, irradiated with light, such as ultraviolet light, to form a layer containing an uncured or semi-cured resin composition on the film substrate or support film, thereby obtaining a dry film or resin-attached film. Furthermore, a protective film may be laminated on this layer. Examples of methods for laminating the protective film include thermal lamination.

[0112] The dry film and resin-coated film having the resin composition layer thus produced are used as materials for optical waveguides according to the embodiments described below. The dry film and resin-coated film according to this embodiment can be used particularly when producing the core layer of an optical waveguide. This is because, as mentioned above, the core layer is required to have a higher refractive index than the cladding layer, and optical loss at a wavelength of 1310 nm occurs mainly in the core layer.

[0113] It should be noted that the resin composition for an optical waveguide according to the above-described embodiment does not necessarily have to be used after forming the dry film according to this embodiment when producing an optical waveguide. For example, as described below, a varnish-like liquid material containing the resin composition for an optical waveguide according to the above-described embodiment may be prepared and used directly when producing a core layer (or clad layer) of an optical waveguide.

[0114] 3. Liquid Material The liquid material according to this embodiment contains the resin composition for an optical waveguide according to the above-described embodiment.

[0115] Specifically, as described above, the liquid material is a varnish-like resin composition for an optical waveguide according to the above-described embodiment, containing, as needed, a solvent, etc. The solvent is not particularly limited as long as it is a solvent for any resin known to those skilled in the art, and examples thereof include methyl ethyl ketone, toluene, xylene, gamma butyrolactone, acetone, methyl isobutyl ketone, cyclohexanone, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, ethyl lactate, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone.

[0116] The liquid material according to this embodiment can be used directly when manufacturing an optical waveguide, without going through a film formation process, to manufacture the core layer or clad layer, preferably the core layer, of the optical waveguide.

[0117] 4. Optical Waveguide The optical waveguide according to this embodiment is formed using the resin composition or dry film according to the above-described embodiment. Because the optical waveguide is formed using the resin composition, dry film, or dry film according to the above-described embodiment, it is possible to suppress optical loss at a wavelength of 1310 nm, making it extremely useful for industrial applications. Furthermore, by forming the core layer of the optical waveguide using the resin composition or dry film according to the above-described embodiment, the effects of achieving both high-NA optical waveguide design and optical loss suppression according to the present invention can be more efficiently achieved.

[0118] Specifically, the optical waveguide according to this embodiment is an optical waveguide including a core layer and a clad layer having a refractive index lower than that of the core layer, and the core layer or the clad layer is formed using the resin composition or the dry film according to the above-described embodiment. As described above, it is preferable that the core layer of the optical waveguide is formed using the resin composition or the dry film according to the above-described embodiment.

[0119] An example of a method for forming an optical waveguide on a substrate using the dry film according to the above embodiment as a core dry film will be described below with reference to Fig. 1. In Fig. 1(a) to Fig. 1(f), the reference characters respectively represent a cladding dry film 1, a core dry film 2, a cladding 3, an undercladding 3a, an overcladding 3b, a core 4, a substrate 10, an electric circuit 11, a slit 12, a mask 13, and an optical waveguide A.

[0120] In the example shown in Fig. 1, a clad dry film and a core dry film are used to form the core and clad, respectively, in order to form the optical waveguide. In the example shown in Fig. 1, the core dry film is the dry film according to the above-described embodiment, and the clad dry film is a dry film having a lower refractive index than the core film.

[0121] First, as shown in Fig. 1(a), a cladding dry film 1 is laminated onto the surface of a substrate 10 on which an electric circuit 11 has been formed, and then the cladding dry film 1 is cured by irradiation with light such as ultraviolet light, heating, or the like. The substrate 10 may be, for example, a flexible printed wiring board in which an electric circuit has been formed on one side of a transparent substrate such as a polyimide film, or a printed wiring board made of glass epoxy. Through this process, an undercladding 3a is formed and laminated on the surface of the substrate 10, as shown in Fig. 1(b).

[0122] 1(c), a core dry film 2 is laminated on the surface of the undercladding 3a, and then a mask 13 having slits 12 of a core pattern is placed over it. Then, photo-curable light such as ultraviolet light is irradiated through the slits 12, thereby exposing the core dry film 2 to the core pattern. The exposure method may be a selective exposure method using a mask 13, or a direct writing method in which a laser beam is scanned and irradiated along the pattern shape.

[0123] After the exposure, the core dry film 2 is developed using a developer such as an aqueous flux cleaner to remove the resin from the unexposed and uncured portions of the core dry film 2. As a result, a core 4 having a predetermined core pattern is formed on the surface of the underclad 3a, as shown in FIG.

[0124] Next, as shown in Fig. 1(e), a clad dry film 1 is laminated so as to cover the underclad 3a and the core 4. Then, the clad dry film 1 is cured by irradiation with light, heating, etc., to form an overclad 3b as shown in Fig. 1(f). In this way, an optical waveguide A is formed on the surface of the substrate 10, in which the core 4 is embedded in the clad 3 consisting of the underclad 3a and the overclad 3b.

[0125] In the optical waveguide A obtained in this manner, the dry film according to the above-described embodiment is used as the core dry film, and thus the optical loss at a wavelength of 1310 nm is suppressed, and good connection to a high NA optical fiber of about 0.2 to 0.4, a high NA planar waveguide, etc. is possible. Therefore, the substrate 10 on which such an optical waveguide A is formed is preferably used as an optical transmission printed wiring board, and is preferably used for, for example, switches in data centers, high performance computing (HPC) mobile phones, personal digital assistants, etc.

[0126] As described above, this specification discloses various aspects of the technology, the main aspects of which are summarized below.

[0127] A resin composition for optical waveguides according to a first aspect of the present invention comprises a low refractive index compound (A) having a refractive index of 1.52 or less and a high refractive index compound (B) having a refractive index of more than 1.52 and 1.75 or less, wherein the low refractive index compound (A) comprises at least one of an aliphatic epoxy compound, a silicon atom-containing epoxy compound, and a fluorine atom-containing epoxy compound, and the high refractive index compound (B) comprises at least one of a fluorene type epoxy compound, a biphenyl type epoxy compound, and a vinyl sulfide compound, the content of the high refractive index compound (B) being 7.5 parts by mass or more and 55 parts by mass or less relative to 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B), and the value calculated from the formula: (refractive index of the low refractive index compound (A) × content of the low refractive index compound (A) + refractive index of the high refractive index compound (B) × content of the high refractive index compound (B)) / (total content of the low refractive index compound (A) and the high refractive index compound (B)) is 1.52 or more and less than 1.60.

[0128] A resin composition for optical waveguides according to a second aspect of the present invention is the resin composition for optical waveguides of the first aspect, wherein the low refractive index compound (A) includes the aliphatic epoxy compound, and the aliphatic epoxy compound has two or more epoxy groups and two or more cyclohexanes in the molecule.

[0129] A resin composition for optical waveguides according to a third aspect of the present invention is the resin composition for optical waveguides according to the first or second aspect, wherein the low refractive index compound (A) comprises the silicon atom-containing epoxy compound, and the silicon atom-containing epoxy compound has two or more epoxy groups in the molecule and has a silicon atom content of 10% by mass or more and 50% by mass or less per molecular weight.

[0130] A resin composition for optical waveguides according to a fourth aspect of the present invention is the resin composition for optical waveguides according to any one of the first to third aspects, and further comprises the fluorine atom-containing epoxy compound, which has two or more epoxy groups in the molecule and has a fluorine atom content of 10% by mass or more and 50% by mass or less per molecular weight.

[0131] A resin composition for optical waveguides according to a fifth aspect of the present invention is the resin composition for optical waveguides according to any one of the first to fourth aspects, wherein the high refractive index compound (B) further comprises an epoxy compound other than the fluorene-containing epoxy compound and the biphenyl-containing epoxy compound, the epoxy compound having a refractive index greater than 1.52 and less than 1.58.

[0132] A resin composition for an optical waveguide according to a sixth aspect of the present invention is the resin composition for an optical waveguide according to any one of the first to fifth aspects, further comprising a cationic curing catalyst (C).

[0133] A resin composition for optical waveguides according to a seventh aspect of the present invention is the resin composition for optical waveguides according to the sixth aspect, wherein the content of the cationic curing catalyst (C) is 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B).

[0134] A dry film according to an eighth aspect of the present invention comprises a layer containing an uncured product of the resin composition for an optical waveguide according to any one of the first to seventh aspects or a semi-cured product of the resin composition for an optical waveguide.

[0135] A resin-coated film according to a ninth aspect of the present invention comprises a resin layer containing an uncured product of the resin composition for optical waveguides of any one of the first to seventh aspects or a semi-cured product of the resin composition for optical waveguides, and a support film.

[0136] A liquid material according to a tenth aspect of the present invention contains the resin composition for an optical waveguide according to any one of the first to seventh aspects.

[0137] An optical waveguide according to an eleventh aspect of the present invention is an optical waveguide comprising a core layer and a clad layer having a refractive index lower than that of the core layer, and the core layer is formed using the resin composition for an optical waveguide according to any one of the first to seventh aspects (or the dry film according to the eighth aspect).

[0138] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0139] In this example, various low refractive index compounds (A) and high refractive index compounds (B) were used to prepare various resin compositions for optical waveguides by varying their content ratios, and core dry films were produced using these compositions. Furthermore, various waveguide samples were produced using the core dry films produced, and the coupling loss with high NA fibers, the optical loss at a wavelength of 1310 nm, and heat resistance were evaluated, and the patterning ability of some of the dry films was evaluated.

[0140] The raw materials used in preparing the resin compositions for optical waveguides in the present examples are summarized below.

[0141] [Low refractive index compounds (A)] "YX8040": hydrogenated bisphenol A type epoxy compound (solid aliphatic epoxy compound), manufactured by Mitsubishi Chemical Corporation; "KR-470": Si-containing epoxy compound, manufactured by Shin-Etsu Chemical Co., Ltd.; "YX7760": bisphenol AF type epoxy compound (F-containing epoxy compound), manufactured by Mitsubishi Chemical Corporation

[0142] [High refractive index compounds (B)] "OGSOL-CG500": solid fluorene-type epoxy compound, manufactured by Osaka Gas Chemicals Co., Ltd. (epoxy equivalent: 310 g / eq) "OGSOL-EG200": liquid fluorene-type epoxy compound, manufactured by Osaka Gas Chemicals Co., Ltd. (epoxy equivalent: 290 g / eq) "NC-3000": biphenyl-type epoxy compound, manufactured by Nippon Kayaku Co., Ltd. (epoxy equivalent: 276 g / eq) "MPV": bis(4-vinylthiophenyl) sulfide (vinyl sulfide compound), manufactured by Sumitomo Seika Chemicals Co., Ltd. "850S": bisphenol A-type epoxy compound (liquid epoxy compound), manufactured by DIC Corporation (epoxy equivalent: 183 g / eq to 193 g / eq) "1001": bisphenol A type epoxy compound (solid epoxy compound), manufactured by Mitsubishi Chemical Corporation (epoxy equivalent weight: 450 g / eq to 500 g / eq) "1006FS": bisphenol A type epoxy compound (solid epoxy compound), manufactured by Mitsubishi Chemical Corporation (epoxy equivalent weight: 900 g / eq to 1100 g / eq)

[0143] [Cationic curing catalyst (C)] "CPI-101A": photocationic curing agent, manufactured by San-Apro Co., Ltd.

[0144] [Antioxidant] "AO-60": phenolic antioxidant, manufactured by ADEKA Corporation

[0145] Of the above raw materials, "KR-470" (Si-containing epoxy compound) has a monomer structure represented by the following structural formula (2).

[0146] "NC-3000" (biphenyl-type epoxy compound) is a compound having a monomer structure represented by the following structural formula (3): In structural formula (3), n represents an integer of 0 to 5.

[0147] First, the method for preparing the resin composition (resin varnish) for the core optical waveguide in each example and each comparative example, the method for manufacturing the core dry film and the method for calculating the value calculated from the relationship between the refractive index and the content, the method for manufacturing the clad dry film used in common in each example and each comparative example, and the method for calculating the NA will be described in detail below.

[0148] <Method of Preparing Resin Composition (Resin Varnish) for Core Optical Waveguide> In each Example and Comparative Example, the components were blended according to the blending compositions (parts by mass) shown in Tables 1 to 3 below, and the mixed solvent of MEK and toluene was adjusted to 60 parts by mass per 100 parts by mass of the total resin, and these were mixed while heating to 50° C. to 80° C. Next, the mixture was filtered through a membrane filter with a pore size of 0.2 μm and then degassed, thereby preparing resin compositions (resin varnishes) for core optical waveguides of Examples 1 to 17 and Comparative Examples 1 to 7.

[0149] <Method for manufacturing core dry film> The resin composition for optical waveguides (resin varnish) of each example and comparative example was applied to a PET film (product number A4100) manufactured by Toyobo Co., Ltd. using a multi-coater with a comma coater head manufactured by Hirano Tecseed Co., Ltd. The PET film was then dried at 130°C for 10 minutes to a predetermined thickness, and a release film, OPP-MA420 manufactured by Oji Specialty Paper Co., Ltd., was thermally laminated to obtain a core dry film with a thickness of approximately 5 μm.

[0150] <Method for Calculating Values ​​Calculated from the Relationship Between Refractive Index and Content> [Measurement of the Refractive Index of Each Low-Refractive Index Compound (A) and Each High-Refractive Index Compound (B)] In order to calculate values ​​calculated from the relationship between refractive index and content in each Example and Comparative Example, the refractive index of each low-refractive index compound (A) and each high-refractive index compound (B) were first measured. Specifically, the refractive index of a cured product using each low-refractive index compound (A) or each high-refractive index compound (B) as the base resin was measured. Specifically, 100 parts by mass of each compound was first blended with 1 part by mass of a photocationic curing agent ("CPI-101A," manufactured by San-Apro Co., Ltd.) and 1 part by mass of a phenolic antioxidant ("AO-60," manufactured by ADEKA Corporation). The amount of a mixed solvent of MEK and toluene was adjusted to 55 parts by mass relative to 100 parts by mass of the compound, and the mixture was mixed while heating to 50°C to 80°C. Next, the mixture was filtered through a membrane filter with a pore size of 0.5 μm and then degassed to prepare a resin varnish. The prepared resin varnish was applied to a PET film (product number A4100) manufactured by Toyobo Co., Ltd. using a multi-coater with a comma coater head manufactured by Hirano Tecseed Co., Ltd. The PET film was then dried at 130°C for 10 minutes to a predetermined thickness, and a release film, OPP-MA420 manufactured by Oji Specialty Paper Co., Ltd., was thermally laminated to obtain a dry film with a thickness of approximately 20 μm.

[0151] The obtained dry films were then laminated using a vacuum laminator "V-130" to a thickness of approximately 50 μm to 80 μm. The laminated dry films were irradiated with ultraviolet light at an exposure dose equivalent to 2000 mJ, and then the PET film of the dry films was peeled off and cured by heat treatment at 140°C for 30 minutes, yielding cured products containing each compound as a base resin. The refractive index of the obtained cured products at a wavelength of 1310 nm at a temperature of 25°C was measured using an Abbe refractometer. The measured refractive indexes of each compound are summarized in Tables 1 to 3 below.

[0152] [Calculation of Values ​​Calculated from the Relationship Between Refractive Index and Content] In each Example and Comparative Example, the values ​​(at a wavelength of 1,310 nm) calculated from the relationship between refractive index and content were calculated using the refractive index of each low-refractive index compound (A) and the refractive index of each high-refractive index compound (B) measured by the method described above. Specifically, the values ​​calculated from the relationship between refractive index and content were obtained using the formula: (refractive index of low-refractive index compound (A) × content of low-refractive index compound (A) + refractive index of high-refractive index compound (B) × content of high-refractive index compound (B)) / (total content of low-refractive index compound (A) and high-refractive index compound (B)). When the resin composition contained two or more high-refractive index compounds (B) as the high-refractive index compound (B), the values ​​calculated from the relationship between refractive index and content were obtained according to the method of Equation 2 described above. The values ​​(refractive index of the core cured product) calculated from the relationship between refractive index and content for each Example and Comparative Example are summarized in Tables 1 to 3 below.

[0153] <Method for Manufacturing Cladding Dry Film> For the cladding dry film, an F-containing epoxy compound ("YX7760" manufactured by Mitsubishi Chemical Corporation) was used as the base epoxy compound. Specifically, 100 parts by mass of the F-containing epoxy compound, 1 part by mass of a photocationic curing agent ("CPI-101A" manufactured by San-Apro Co., Ltd.), and 1 part by mass of a phenolic antioxidant ("AO-60" manufactured by ADEKA Corporation) were first blended together, and the amount of a mixed solvent of MEK and toluene was adjusted to 55 parts by mass relative to 100 parts by mass of the F-containing epoxy compound. These were then mixed while heating to 50°C to 80°C. Next, the mixture was filtered through a membrane filter with a pore size of 0.5 μm and degassed to prepare a resin varnish. The prepared resin varnish was applied to a PET film (product number A4100) manufactured by Toyobo Co., Ltd. using a multi-coater with a comma coater head manufactured by Hirano Tecseed Co., Ltd. The PET film was then dried at 130°C for 10 minutes to a predetermined thickness, and a release film, OPP-MA420 manufactured by Oji Specialty Paper Co., Ltd., was thermally laminated to obtain a dry film for cladding having a thickness of approximately 20 μm. The refractive index of the cured cladding material was measured at a wavelength of 1310 nm at a temperature of 25°C using the same method as described above, and was found to be 1.51.

[0154] <Method of Calculating NA> The numerical aperture (NA) was calculated from the value (refractive index of the cured core product) calculated from the relationship between the refractive index and content in each Example and Comparative Example calculated by the method described above, and the measured refractive index of the cured cladding product (1.51) using the following formula. The calculated numerical apertures (NA) for each Example and Comparative Example are summarized in Tables 1 to 3 below. NA = ((value calculated from the relationship between the refractive index and content) x (value calculated from the relationship between the refractive index and content) - (refractive index of the cured cladding product) x (refractive index of the cured cladding product)). １／２

[0155] Next, the following evaluation test 1 was carried out using the core dry films of each of the examples and comparative examples and the common clad dry film produced by the above-mentioned method.

[0156] <Evaluation Test 1> [Evaluation of Coupling Loss with High NA Fiber] (Fabrication of Waveguide Samples) Whether or not the dry film can be effectively used in designing a high NA optical waveguide was evaluated based on the coupling loss with a high NA fiber. To evaluate the coupling loss with a high NA fiber, first, a waveguide sample was fabricated using the core dry film and the common cladding dry film of each Example and Comparative Example fabricated by the above-described method.

[0157] First, the cladding dry film was laminated onto the substrate using a vacuum laminator "V-130" at 65°C and 0.3 MPa. Then, an ultra-high pressure mercury lamp was used to irradiate the film with 2 J / cm. ２ After irradiation, the release film of the clad dry film was peeled off, and the clad dry film was heat-treated at 160° C. for 30 minutes to harden the clad dry film and form an underclad.

[0158] Thereafter, the core dry film in each Example and Comparative Example was laminated onto the surface of the underclad using a vacuum laminator "V-130" in the same manner and under the same conditions as above. After peeling off the release film from the core dry film, the film was heat-treated at 150°C for 15 minutes, and a mask capable of forming a 5 μm-wide pattern was placed on top, followed by irradiating the film with 2 J / cm using an ultra-high pressure mercury lamp. ２ The dry film was exposed to light at a light intensity of 1000 W and further heat-treated at 160°C for 30 minutes. The unexposed portions of the dry film were then dissolved and removed by development using a water-based flux cleaner (Pine Alpha ST-100SX, manufactured by Arakawa Chemical Industries, Ltd.) adjusted to 55°C as the developer. After dissolution and removal, the core portion was finish-washed with water, air-blown, and dried at 120°C for 15 minutes to form a core.

[0159] Furthermore, a dry film for cladding was laminated onto the formed core using a vacuum laminator "V-130" under conditions of 80°C and 0.3 MPa. After peeling off the release film from the laminated dry film for cladding, the core was heat-treated at 140°C for 20 minutes and then irradiated with 2 J / cm using an ultra-high pressure mercury lamp. ２The cladding dry film was irradiated with ultraviolet light at a light intensity of 1000 nm. The laminated film was then further heat-treated at 160°C for 30 minutes to cure the cladding dry film and form an overclad, thereby obtaining a waveguide sample with a 5 μm core size for evaluation. In each example and comparative example, samples with waveguide lengths of 5.0 cm, 4.4 cm, 3.8 cm, 2.6 cm, and 2.0 cm were manufactured as the waveguide samples.

[0160] (Measurement and Calculation of Coupling Loss with High NA Fiber) The coupling loss with a high NA fiber was determined using the cutback method. Specifically, the insertion loss (dB) at a wavelength of 1310 nm was measured and calculated using the waveguide samples of each Example and Comparative Example with waveguide lengths of 5.0 cm, 4.4 cm, 3.8 cm, 2.6 cm, and 2.0 cm obtained by the above method. More specifically, light from a 1310 nm LED light source was first passed through a high NA fiber ("UHNA1" manufactured by THORLABS) and incident on the end of the manufactured waveguide sample via matching oil (silicone oil). Furthermore, an optical fiber with a core diameter of 50 μm and NA of 0.21 was passed through the same matching oil, and the other end of the waveguide sample was connected to a power meter to measure the power (P1) when an optical circuit was inserted. The power (P0) measured by butting two similar fibers together without an optical circuit was also measured. From the measured values, the insertion loss (dB) at a wavelength of 1310 nm was calculated using the formula -10 log (P1 / P0). This measurement and calculation was performed on samples of all of the aforementioned waveguide lengths in each Example and Comparative Example. When the measured values ​​were plotted with the waveguide length (cm) on the horizontal axis and the measured and calculated insertion loss (dB) at a wavelength of 1310 nm on the vertical axis, the insertion loss (dB) for each waveguide length was plotted on a straight line. The coupling loss (dB / cm) was then calculated from the intercept of the insertion loss (dB) line. The evaluation criteria for coupling loss with high NA fibers are shown below. The calculated values ​​and evaluation results for coupling loss with high NA fibers at a wavelength of 1310 nm in each Example and Comparative Example are summarized in Tables 1 to 3 below. Evaluation criteria: A: Loss value is 0.2 dB / cm or less B: Loss value is more than 0.2 dB / cm and less than 1.0 dB / cm C: Loss value is 1.0 dB / cm or more

[0161] [Evaluation of optical loss at wavelength 1310 nm] Whether or not optical loss at wavelength 1310 nm was suppressed was evaluated by the following method. The optical loss (propagation loss) (dB / cm) at wavelength 1310 nm was taken as the slope of the line finally obtained when the coupling loss with a high NA fiber was calculated using the cutback method described above. The evaluation criteria for optical loss (propagation loss) at wavelength 1310 nm are shown below. The optical loss (propagation loss) values ​​and evaluation results at wavelength 1310 nm for each example and each comparative example are summarized in Tables 1 to 3 below. Evaluation criteria: A Loss value is 0.30 dB / cm or less B Loss value is greater than 0.30 dB / cm and less than 0.35 dB / cm C Loss value is greater than 0.35 dB / cm

[0162] [Evaluation of Heat Resistance] As an evaluation test of heat resistance, the optical loss at a wavelength of 1310 nm after reflow treatment was evaluated and peeling between the clad and the core was observed.

[0163] (Evaluation of Optical Loss at a Wavelength of 1310 nm After Reflow Treatment) First, the waveguide samples of each example and comparative example manufactured by the method described above and having each waveguide length were subjected to reflow treatment five times (five passes) under the reflow conditions for lead-free solder. Then, in the same manner as described above, the optical insertion loss (dB) at a wavelength of 1310 nm was calculated for the waveguide samples of all waveguide lengths in each example and comparative example. Next, in the same manner as described above, a straight line was created by plotting the waveguide length (cm) versus the insertion loss (dB), and the slope of the line was taken as the optical loss (propagation loss) (dB / cm) at a wavelength of 1310 nm after reflow treatment. In addition, the loss increase rate (%) after reflow treatment was also calculated based on the optical loss at a wavelength of 1310 nm measured above (before reflow treatment). The evaluation criteria for the optical loss (propagation loss) at a wavelength of 1310 nm after reflow treatment are shown below. The optical loss (propagation loss) values ​​at a wavelength of 1310 nm after reflow treatment and the evaluation results for each example and comparative example are summarized in Tables 1 to 3 below. Evaluation criteria: A Loss value is 0.30 dB / cm or less, and the loss increase rate is 6% or less B Loss value is more than 0.30 dB / cm and 0.35 dB / cm or less, and the loss increase rate is 6% or less C Loss value is more than 0.35 dB / cm, and / or the loss increase rate is more than 6%

[0164] (Observation of delamination between cladding and core after reflow treatment) The presence or absence of delamination between the cladding and core was visually observed for waveguide samples of each waveguide length in each example and each comparative example, which had undergone reflow treatment five times (five passes) using the method described above. If delamination was not observed in any of the waveguide samples of any of the waveguide lengths, delamination was recorded as "absent." On the other hand, if delamination was observed in waveguide samples of one or more of the waveguide lengths, delamination was recorded as "present."

[0165] The evaluation, measurement and calculation results for each of the above examples and comparative examples, along with the blended compositions, are summarized in the following Tables 1 to 3. In the following Tables 1 to 3, "-" indicates that the composition is not blended.

[0166]

[0167]

[0168]

[0169] <Discussion> As shown in Tables 1 to 3 above, the resin compositions in Examples 1 to 17 contained at least one of an aliphatic epoxy compound, a Si-containing epoxy compound, and an F-containing epoxy compound as the low refractive index compound (A), and at least one of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound as the high refractive index compound (B), the content of the high refractive index compound (B) being in the range of 7.5 parts by mass or more and 55 parts by mass or less, and the value calculated from the relationship between the refractive index and the content being in the range of 1.52 or more and less than 1.60. In Examples 1 to 17 which satisfied all of these conditions according to the present invention, the coupling loss with the high NA fiber and the light loss at a wavelength of 1310 nm were suitably suppressed, and the heat resistance was also good in evaluations of both the light loss after reflow treatment and the presence or absence of delamination.

[0170] On the other hand, in Comparative Example 1, in which the content of the high refractive index compound (B) was less than 7.5 parts by mass and the value calculated from the relationship between the refractive index and the content was less than 1.52, the coupling loss with the high NA fiber was large. This is thought to be because the content of the high refractive index compound (B) was small, so the value calculated from the relationship between the refractive index and the content did not increase much, and therefore the NA did not increase to the desired value.

[0171] In Comparative Example 2, in which the content of the high refractive index compound (B) was more than 55 parts by mass and the value calculated from the relationship between the refractive index and the content was more than 1.60, the coupling loss with the high NA fiber was also large. This is thought to be because the content of the high refractive index compound (B) was so high that the value calculated from the relationship between the refractive index and the content became excessively large, and therefore the NA also increased beyond the desired value.

[0172] In Comparative Examples 3 to 5, which did not contain any of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound as the high refractive index compound (B) and in which the content of the high refractive index compound (B) was more than 55 parts by mass, the optical loss at a wavelength of 1310 nm was large and the heat resistance was also poor in both the evaluation of the optical loss after reflow treatment and the presence or absence of peeling. In Comparative Examples 6 and 7, which did not contain any of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound as the high refractive index compound (B) but in which the content of the high refractive index compound (B) was in the range of 7.5 parts by mass or more and 55 parts by mass or less, the optical loss at a wavelength of 1310 nm was large and the heat resistance was poor in the evaluation of the optical loss after reflow treatment.

[0173] From the results of Comparative Examples 3 to 7, it was found that even when the content of the high refractive index compound (B) is set within the range of 7.5 parts by mass or more and 55 parts by mass or less, and the value calculated from the relationship between the refractive index and the content is set within the range of 1.52 or more and less than 1.60, unless the resin composition contains at least one of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound as the high refractive index compound (B), it is not possible to suppress light loss, and from the viewpoint of light loss and / or peeling, heat resistance is also inferior.

[0174] Furthermore, the dry films of the respective examples produced by the above method were subjected to the following evaluation test 2.

[0175] <Evaluation Test 2> [Evaluation of Patterning Ability] The patterning ability was evaluated as follows. Specifically, a 7 μm-thick core dry film for each Example was obtained by the same method as the core dry film manufacturing method described above, except that the thickness was varied. Next, the 7 μm-thick core dry film for each Example was laminated onto the underclad by the same method as the waveguide sample manufacturing method described above. Subsequently, a core was formed by exposure, heat treatment, development, and the like, by the same method as the waveguide sample manufacturing method described above, except that a mask for forming a 7 μm-wide core was used. Thereafter, the shape of the formed core, specifically the core width, was measured using a confocal microscope ("HYBRID," manufactured by Lasertec Corporation), and the patterning ability was evaluated based on the measured value. The core width measurement value was the average value measured at five random locations. The evaluation criteria for patterning ability are shown below. The measured core width values ​​and evaluation results for each Example after curing are summarized in Tables 4 and 5 below. Evaluation criteria: A: The measured core width is 6.5 μm or more and 7.5 μm or less. B: The measured core width is 6.0 μm or more and less than 6.5 μm, or more than 7.5 μm and 8.0 μm or less. C: The measured core width is less than 6.0 μm or more than 8.0 μm (not applicable).

[0176] The measurement results and evaluation of the patterning properties in each of the above examples, along with the blended compositions, are summarized in the following Tables 4 and 5. In the following Tables 4 and 5, "-" indicates that the composition is not blended, as in the above Tables 1 to 3.

[0177]

[0178]

[0179] <Discussion> As shown in Tables 4 and 5 above, the resin compositions in Examples 1 to 17 generally had good patterning properties. Note that the results of Example 6 show that when the amount of cationic curing catalyst (C) is large, the core width becomes slightly wider, although within the allowable range.

[0180] This application is based on Japanese Patent Application No. 2024-126518 filed on August 2, 2024, the contents of which are incorporated herein by reference.

[0181] The embodiments and examples disclosed herein should be understood to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0182] According to the present invention, it is possible to provide a resin composition for optical waveguides that is suitable for use in designing high NA optical waveguides, that can suppress optical loss at a wavelength of 1310 nm, and that has heat resistance. Therefore, the resin composition is suitable for use in designing high NA optical waveguides and is therefore extremely useful industrially.

Claims

1. A resin composition for optical waveguides, comprising: a low refractive index compound (A) having a refractive index of 1.52 or less; and a high refractive index compound (B) having a refractive index of more than 1.52 and less than 1.75; wherein the low refractive index compound (A) comprises at least one of an aliphatic epoxy compound, a silicon atom-containing epoxy compound, and a fluorine atom-containing epoxy compound; and the high refractive index compound (B) comprises at least one of a fluorene-type epoxy compound, a biphenyl-type epoxy compound, and a vinyl sulfide compound; the content of the high refractive index compound (B) is 7.5 parts by mass or more and 55 parts by mass or less per 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B); and the value calculated from the formula: (refractive index of the low refractive index compound (A) × content of the low refractive index compound (A) + refractive index of the high refractive index compound (B) × content of the high refractive index compound (B)) / (total content of the low refractive index compound (A) and the high refractive index compound (B)) is 1.52 or more and less than 1.

60.

2. The resin composition for optical waveguides according to claim 1, wherein the low refractive index compound (A) contains the aliphatic epoxy compound, and the aliphatic epoxy compound has two or more epoxy groups and two or more cyclohexane groups in the molecule.

3. The resin composition for optical waveguides according to claim 1, wherein the low refractive index compound (A) comprises the silicon atom-containing epoxy compound, and the silicon atom-containing epoxy compound has two or more epoxy groups in the molecule and has a silicon atom content of 10% by mass or more and 50% by mass or less per molecular weight.

4. The resin composition for optical waveguides according to claim 1, wherein the low refractive index compound (A) comprises the fluorine atom-containing epoxy compound, and the fluorine atom-containing epoxy compound has two or more epoxy groups in the molecule and has a fluorine atom content of 10% by mass or more and 50% by mass or less per molecular weight.

5. The resin composition for optical waveguides according to claim 1, wherein the high refractive index compound (B) further comprises an epoxy compound other than the fluorene-containing epoxy compound and the biphenyl-containing epoxy compound, the epoxy compound having a refractive index greater than 1.52 and less than 1.

58.

6. The resin composition for an optical waveguide according to claim 1, further comprising a cationic curing catalyst (C).

7. A resin composition for optical waveguides according to claim 6, wherein the content of the cationic curing catalyst (C) is 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the total of the low refractive index compound (A) and the high refractive index compound (B).

8. A dry film comprising a layer containing an uncured product of the resin composition for an optical waveguide according to any one of claims 1 to 7 or a semi-cured product of the resin composition for an optical waveguide.

9. A resin-coated film comprising a layer containing an uncured or semi-cured product of the resin composition for optical waveguides according to any one of claims 1 to 7, and a support film.

10. A liquid material comprising the resin composition for optical waveguides according to any one of claims 1 to 7.

11. An optical waveguide comprising a core layer and a clad layer having a refractive index lower than that of the core layer, wherein the core layer is formed using the resin composition for an optical waveguide according to any one of claims 1 to 7.

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