JP2024066347A - Photosensitive resin composition - Google Patents

Abstract

[Problem] To provide a photosensitive resin composition that can be used to manufacture an optical waveguide with excellent plating adhesion and core formability and small transmission loss. [Solution] A photosensitive resin composition containing (A) an epoxy resin, (B) a resin containing a carboxy group and an ethylenic double bond, (C) a photopolymerization initiator, and (D) a non-developable polymer having a solubility parameter (SP value) of 9 (cal/cm3)1/2 or more and 13 (cal/cm3)1/2 or less. [Selected Figure] None

Description

The present invention relates to a photosensitive resin composition, a resin sheet, a photosensitive resin composition set, an optical waveguide and its manufacturing method, and an optical/electrical hybrid board.

Technological advances such as 5G communications, autonomous driving, IoT, artificial intelligence, and big data are driving demands for ultra-high-speed and large-capacity communications. The semiconductor packages that underpin these technologies have traditionally supported high-speed communications by passing high-frequency currents through them. However, in recent years, issues such as noise generation, communication losses, and heat generation caused by high-speed communications have become evident. To solve these issues, active efforts have been made in recent years to implement optical circuits on electrical wiring boards and achieve energy savings and low-latency, high-speed communications (Patent Documents 1 and 2).

JP 2019-211540 A Patent No. 5771978

In data centers, where high-speed transmission is required, research into the introduction of silicon photonics is being actively conducted. Silicon photonics is highly compatible with conventional LSI manufacturing processes. Therefore, it is expected that the use of silicon photonics will enable the formation of nanometer-sized thin-wire waveguides at low cost, based on the technology cultivated in electronic circuit integration technology.

For example, silicon photonics is expected to form an optical integrated circuit on a chip using fine-wire waveguides. When manufacturing an optoelectronic hybrid board mounting this chip, it is required to provide an optical waveguide on the optoelectronic hybrid board in order to extract signal light from the fine-wire waveguide inside the chip to the outside of the chip and connect it to the wiring between chips. From the viewpoint of efficiently forming a fine optical waveguide, it is desirable to form the optical waveguide from a cured product of a photosensitive resin composition. For this reason, excellent core forming properties are desired to form a fine core layer. In addition, it is also desirable to suppress the transmission loss of the optical waveguide in order to suppress attenuation of the signal light.

In recent years, it has been envisaged to provide a conductor layer by subjecting the core layer of an optical waveguide to metal plating. One possible method for improving adhesion between the core layer and the conductor layer is to roughen the surface of the core layer to provide irregularities, but providing irregularities on the surface of the core layer can reduce the transmission loss of the optical waveguide, and may result in the loss of its function as an optical waveguide.

The present invention was devised in view of the above problems, and aims to provide a photosensitive resin composition that has excellent plating adhesion and core forming properties and can be used to manufacture optical waveguides with low transmission loss; a resin sheet containing the photosensitive resin composition; a photosensitive resin composition set; an optical waveguide; and an optical-electrical hybrid board.

The present inventors have conducted extensive research to solve the above problems, and as a result, have found that an optical waveguide having excellent plating adhesion, excellent core formability, and ^small transmission ^loss can be manufactured by using a photosensitive resin composition containing a combination of (A) an epoxy resin, (B) a resin containing a carboxy group and an ethylenic double bond, (C) a photopolymerization initiator, and (D) a non-developable polymer having a solubility parameter (SP value) of 9 (cal/cm3) ^1/2 or more and 13 (cal/ ^cm3 )1/2 or less, and have completed the present invention.

式（Ｄ－１）中、Ｒ^１は、それぞれ独立に水素原子又はメチル基を表し、Ｒ^２は、それぞれ独立に水素原子、又は炭素原子数１～２２のアルキル基を表す。ｐは、それぞれ独立に２～４の整数を表し、ｑは２～１００の整数を表す。
式（Ｄ－２）中、Ｒ^３は、それぞれ独立に水素原子又はメチル基を表し、Ｒ^４は、それぞれ独立に炭素原子数１～２２のアルキル基を表す。
［５］ （Ｂ）成分の溶解パラメータ（ＳＰ値）が、９（ｃａｌ／ｃｍ^３）^１／２以上１１（ｃａｌ／ｃｍ^３）^１／２以下である、［１］～［４］のいずれかに記載の感光性樹脂組成物。
［６］ さらに、（Ｅ）平均粒径が１００ｎｍ以下の無機充填材を含有する、［１］～［５］のいずれかに記載の感光性樹脂組成物。
［７］ 光導波路のコア層製造用である、［１］～［６］のいずれかに記載の感光性樹脂組成物。
［８］ 支持体と、該支持体上に形成された感光性樹脂組成物層と、を備え、
感光性樹脂組成物層が、［１］～［７］のいずれかに記載の感光性樹脂組成物からなる、樹脂シート。
［９］ 感光性樹脂組成物層の厚みが、１μｍ以上１５μｍ以下である、［８］に記載の樹脂シート。
［１０］ コア用感光性樹脂組成物とクラッド用樹脂組成物とを含む感光性樹脂組成物セットであって、
コア用感光性樹脂組成物が、［１］～［７］のいずれかに記載の感光性樹脂組成物を含む、感光性樹脂組成物セット。
［１１］ コア層及びクラッド層を備え、
コア層が、［１］～［７］のいずれかに記載の感光性樹脂組成物の硬化物を含む、光導波路。
［１２］ 波長１３００ｎｍ～１３２０ｎｍの光を伝送可能である、［１１］に記載の光導波路。
［１３］ シングルモードの光導波路である、［１２］に記載の光導波路。
［１４］ ［１１］～［１３］のいずれかに記載の光導波路を備えた光電気混載基板。 That is, the present invention includes the following.
[1] (A) an epoxy resin,
(B) a resin containing a carboxy group and an ethylenic double bond,
A photosensitive resin composition comprising: (C) a photopolymerization initiator; and (D) a non-developable polymer having a solubility parameter (SP value) of 9 (cal/cm ³ ) ^1/2 or more and 13 (cal/cm ³ ) ^1/2 or less.
[2] The photosensitive resin composition according to [1], wherein the weight average molecular weight of the component (D) is 3,000 or more and 100,000 or less.
[3] The photosensitive resin composition according to [1] or [2], wherein the component (D) contains an acrylic polymer.
[4] The photosensitive resin composition according to any one of [1] to [3], wherein the component (D) has a structural unit represented by the following formula (D-1) and a structural unit represented by the following formula (D-2):

In formula (D-1), R ¹ 's each independently represent a hydrogen atom or a methyl group, and R ² 's each independently represent a hydrogen atom or an alkyl group having 1 to 22 carbon atoms. p's each independently represent an integer of 2 to 4, and q's each independently represent an integer of 2 to 100.
In formula (D-2), R ³ 's each independently represent a hydrogen atom or a methyl group, and R ⁴ 's each independently represent an alkyl group having 1 to 22 carbon atoms.
[5] The photosensitive resin composition according to any one of [1] to [4], wherein the solubility parameter (SP value) of component (B) is 9 (cal/cm ³ ) ^1/2 or more and 11 (cal/cm ³ ) ^1/2 or less.
[6] The photosensitive resin composition according to any one of [1] to [5], further comprising (E) an inorganic filler having an average particle size of 100 nm or less.
[7] The photosensitive resin composition according to any one of [1] to [6], which is for producing a core layer of an optical waveguide.
[8] A photosensitive resin composition comprising a support and a photosensitive resin composition layer formed on the support,
A resin sheet, wherein the photosensitive resin composition layer comprises the photosensitive resin composition according to any one of [1] to [7].
[9] The resin sheet according to [8], wherein the photosensitive resin composition layer has a thickness of 1 μm or more and 15 μm or less.
[10] A photosensitive resin composition set including a core photosensitive resin composition and a clad resin composition,
A photosensitive resin composition set, wherein a core photosensitive resin composition comprises the photosensitive resin composition according to any one of [1] to [7].
[11] A core layer and a clad layer,
An optical waveguide, wherein a core layer comprises a cured product of the photosensitive resin composition according to any one of [1] to [7].
[12] The optical waveguide according to [11], capable of transmitting light having a wavelength of 1300 nm to 1320 nm.
[13] The optical waveguide according to [12], which is a single-mode optical waveguide.
[14] An optical/electrical hybrid board comprising the optical waveguide according to any one of [11] to [13].

The present invention provides a photosensitive resin composition that has excellent plating adhesion and core formation properties and can be used to manufacture optical waveguides with low optical transmission loss; a photosensitive resin composition set that includes the photosensitive resin composition; an optical waveguide; and an optical/electrical hybrid board.

FIG. 1 is a perspective view showing a schematic diagram of an optical waveguide according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view for explaining step (I) of the method for producing an optical waveguide according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view for explaining step (II) of the method for producing an optical waveguide according to one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view for explaining step (III) of the method for producing an optical waveguide according to one embodiment of the present invention. FIG. 5 is a schematic cross-sectional view for explaining step (IV) of the method for producing an optical waveguide according to one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view for explaining step (V) of the method for producing an optical waveguide according to one embodiment of the present invention. FIG. 7 is a schematic cross-sectional view for explaining step (VI) of the method for producing an optical waveguide according to one embodiment of the present invention. FIG. 8 is a schematic cross-sectional view for explaining step (VII) of the method for producing an optical waveguide according to one embodiment of the present invention. FIG. 9 is a schematic cross-sectional view for explaining step (VIII) of the method for producing an optical waveguide according to one embodiment of the present invention. FIG. 10 is a schematic cross-sectional view for explaining step (IX) of the method for producing an optical waveguide according to one embodiment of the present invention.

The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples given below, and may be modified as desired without departing from the scope of the claims and their equivalents.

[Photosensitive resin composition]
The photosensitive resin composition of the present invention contains (A) an epoxy resin, (B) a resin containing a carboxy group and an ethylenic double bond, (C) a photopolymerization initiator, and (D) a non-developable polymer having a solubility parameter (SP value) of 9 (cal/ ^cm3 ) ^1/2 or more and 13 (cal/ ^cm3 ) ^1/2 or less. The photosensitive resin composition of the present invention makes it possible to produce an optical waveguide which has excellent plating adhesion and core formability and has small optical transmission loss.

The photosensitive resin composition of the present invention may further contain optional components in combination with components (A) to (D). Examples of optional components include (E) an inorganic filler having an average particle size of 100 nm or less, (F) a reactive diluent, (G) a solvent, and (H) other additives. Each component contained in the photosensitive resin composition will be described in detail below.

In the following description, unless otherwise specified, the term "(meth)acrylic acid" includes acrylic acid, methacrylic acid, and combinations thereof, and the term "(meth)acrylate" includes acrylate, methacrylate, and combinations thereof.

In addition, in the present invention, the content of each component in the photosensitive resin composition is the value when the non-volatile components in the photosensitive resin composition are taken as 100 mass %, unless otherwise specified.

<(A) Epoxy Resin>
The photosensitive resin composition contains, as component (A), an epoxy resin (A). The epoxy resin (A) is a curable resin having an epoxy group.

(A) Examples of epoxy resins include bixylenol type epoxy resins; bisphenol type epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, and bisphenol AF type epoxy resins; dicyclopentadiene type epoxy resins; novolac type epoxy resins such as trisphenol type epoxy resins and phenol novolac type epoxy resins; tert-butyl-catechol type epoxy resins; naphthalene type epoxy resins, naphthol type epoxy resins, naphthol aralkyl type epoxy resins, naphthylene ether type epoxy resins, and naphthol novolac type epoxy resins. Examples of the epoxy resin include epoxy resins containing an amine skeleton, anthracene type epoxy resins, glycidylamine type epoxy resins, glycidyl ester type epoxy resins, cresol novolac type epoxy resins, phenol aralkyl type epoxy resins, biphenyl skeleton-containing epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, trimethylol type epoxy resins, tetraphenylethane type epoxy resins, isocyanurate type epoxy resins, and phenolphthalimidine type epoxy resins. Among these, the epoxy resin (A) preferably contains any one of naphthalene type epoxy resins, naphthol aralkyl type epoxy resins, biphenyl skeleton-containing epoxy resins, and bisphenol A type epoxy resins, from the viewpoint of obtaining the effects of the present invention significantly. The epoxy resin (A) may be used alone or in combination of two or more types.

The photosensitive resin composition of the present invention preferably contains, as the epoxy resin (A), an epoxy resin having two or more epoxy groups in one molecule. The ratio of the epoxy resin having two or more epoxy groups in one molecule relative to 100% by mass of the epoxy resin (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

The epoxy resin (A) may be an epoxy resin that is solid at a temperature of 20°C (hereinafter sometimes referred to as "solid epoxy resin") or an epoxy resin that is liquid at a temperature of 20°C (hereinafter sometimes referred to as "liquid epoxy resin"). The photosensitive resin composition of the present invention may contain only a liquid epoxy resin as the epoxy resin (A), or may contain only a solid epoxy resin, or may contain both a liquid epoxy resin and a solid epoxy resin, but it is particularly preferable that the photosensitive resin composition contains only a solid epoxy resin.

As the solid epoxy resin, a solid epoxy resin having three or more epoxy groups in one molecule is preferable, and an aromatic solid epoxy resin having three or more epoxy groups in one molecule is more preferable.

As solid epoxy resins, bixylenol type epoxy resins, naphthalene type epoxy resins, naphthalene type tetrafunctional epoxy resins, naphthol novolac type epoxy resins, cresol novolac type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol type epoxy resins, biphenyl type epoxy resins, naphthylene ether type epoxy resins, anthracene type epoxy resins, bisphenol A type epoxy resins, bisphenol AF type epoxy resins, phenol aralkyl type epoxy resins, tetraphenylethane type epoxy resins, and phenolphthalimidine type epoxy resins are preferred, and any of naphthalene type epoxy resins, naphthol type epoxy resins, and biphenyl type epoxy resins is more preferred, with naphthalene type epoxy resins being even more preferred.

Specific examples of solid epoxy resins include DIC's "HP4032H" (naphthalene type epoxy resin); DIC's "HP-4700" and "HP-4710" (naphthalene type tetrafunctional epoxy resin); DIC's "N-690" (cresol novolac type epoxy resin); DIC's "N-695" (cresol novolac type epoxy resin); DIC's "N-673" (cresol novolac type epoxy resin); DIC's "HP-7200", "HP-7200HH", "HP-7200H", and "HP-7200L" (dicyclopentadiene type epoxy resin); "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthylene ether type epoxy resin) manufactured by DIC Corporation; "EPPN-502H" (trisphenol type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC7000L" (naphthol novolac type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC3000H", "NC3000", "NC3000L", "NC3000FH", "NC3100" (biphenyl type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd. "ESN475V" and "ESN4100V" (naphthalene type epoxy resins) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN485" (naphthol type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN375" (dihydroxynaphthalene type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", "YX4000HK", and "YL7890" (bixylenol type epoxy resins) manufactured by Mitsubishi Chemical Co., Ltd.; "YL6121" (biphenyl type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "YX8800" (anthracene type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; Examples of such epoxy resins include "YX7700" (phenol aralkyl type epoxy resin) manufactured by Mikal Co., Ltd.; "PG-100" and "CG-500" manufactured by Osaka Gas Chemical Co., Ltd.; "YL7760" (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "YL7800" (fluorene type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "jER1010" (bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "jER1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; and "WHR991S" (phenolphthalimidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These may be used alone or in combination of two or more types.

Preferably, the liquid epoxy resin has two or more epoxy groups in one molecule.

Preferred liquid epoxy resins are glycirol type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane dimethanol type epoxy resins, cyclic aliphatic glycidyl ethers, and epoxy resins having a butadiene structure.

Specific examples of liquid epoxy resins include Nagase ChemteX's "EX-992L," Mitsubishi Chemical's "YX7400," DIC's "HP4032," "HP4032D," and "HP4032SS" (naphthalene-type epoxy resins); Mitsubishi Chemical's "828US," "jER828EL," "828EL," "825," and "Epicoat 828EL" (bisphenol A-type epoxy resins); Mitsubishi Chemical's "jER807" and "1750" (bisphenol A-type epoxy resins). phenol F type epoxy resin); Mitsubishi Chemical Corporation's "jER152" (phenol novolac type epoxy resin); Mitsubishi Chemical Corporation's "630", "630LSD", and "604" (glycidylamine type epoxy resin); ADEKA Corporation's "ED-523T" (glycilol type epoxy resin); ADEKA Corporation's "EP-3950L" and "EP-3980S" (glycidylamine type epoxy resin); ADEKA Corporation's "EP-4088S" (dicyclopentasiloxane type epoxy resin); bisphenol A type epoxy resin); "ZX1059" manufactured by Nippon Steel Chemical & Material Co., Ltd. (mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin); "EX-721" manufactured by Nagase ChemteX Corporation (glycidyl ester type epoxy resin); "EX-991L" manufactured by Nagase ChemteX Corporation (alkyleneoxy skeleton and butadiene skeleton-containing epoxy resin); "Celloxide 2021P" manufactured by Daicel Corporation (alicyclic epoxy resin having an ester skeleton) Examples include Daicel's "PB-3600," Nippon Soda's "JP-100" and "JP-200" (epoxy resins with butadiene structure); Nippon Steel Chemical & Material's "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane type epoxy resin); Osaka Gas Chemical's "EG-280" (fluorene structure-containing epoxy resin); and Nagase ChemteX's "EX-201" (cyclic aliphatic glycidyl ether).

When a combination of solid epoxy resin and liquid epoxy resin is used as the (A) epoxy resin, the mass ratio thereof (solid epoxy resin:liquid epoxy resin) is preferably 10:1 to 1:50, more preferably 5:1 to 1:20, and particularly preferably 2:1 to 1:10.

(A) The epoxy resin preferably contains an epoxy resin having a skeleton selected from a naphthalene skeleton and a biphenyl skeleton, and more preferably contains an epoxy resin having a naphthalene skeleton.

The epoxy equivalent of the (A) epoxy resin is preferably 50 g/eq. to 5,000 g/eq., more preferably 60 g/eq. to 2,000 g/eq., even more preferably 70 g/eq. to 1,000 g/eq., and even more preferably 80 g/eq. to 500 g/eq. The epoxy equivalent is the mass of the resin per equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

The weight average molecular weight (Mw) of the (A) epoxy resin is preferably 100 to 5,000, more preferably 250 to 3,000, and even more preferably 400 to 1,500. The weight average molecular weight of the resin can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

The content of (A) epoxy resin is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on 100% by mass of the non-volatile components of the photosensitive resin composition, from the viewpoint of obtaining a significant effect of the present invention, and is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less.

<(B) Resin containing a carboxy group and an ethylenic double bond>
The photosensitive resin composition of the present invention contains, as component (B), a resin containing a carboxy group and an ethylenic double bond (B). The resin containing a carboxy group and an ethylenic double bond (B) as component (B) does not include those corresponding to the above-mentioned component (A). One type of component (B) may be used alone, or two or more types may be used in combination.

Since the resin containing (B) a carboxy group and an ethylenic double bond contains a carboxy group, which is an acidic group, the photosensitive resin composition of the present invention can be soluble in an alkaline developer such as a 1% by mass aqueous solution of sodium carbonate. In the resin containing (B) a carboxy group and an ethylenic double bond, the number of carboxy groups in one molecule may be one or two or more.

(B) Resin containing a carboxy group and an ethylenic double bond contains an ethylenic double bond as an aliphatic carbon-carbon unsaturated bond. Therefore, (B) resin containing a carboxy group and an ethylenic double bond can undergo polymerization when (C) photopolymerization initiator generates radicals.

(B) The resin containing a carboxy group and an ethylenic double bond usually has a group containing the above-mentioned ethylenic double bond. This group generally has radical polymerizability, and is therefore hereinafter sometimes referred to as a "radical polymerizable group." Examples of radical polymerizable groups include (meth)acryloyl groups (acryloyl groups or methacryloyl groups), vinyl groups, allyl groups, propargyl groups, butenyl groups, ethynyl groups, phenylethynyl groups, maleimide groups, and nadimide groups, and from the viewpoint of radical polymerization reactivity, (meth)acryloyl groups are preferred.

(B) The number of radical polymerizable groups per molecule of the resin containing a carboxy group and an ethylenic double bond may be one or two or more.

In one embodiment, the resin (B) containing a carboxy group and an ethylenic double bond is preferably an acid-modified epoxy (meth)acrylate resin.

Since the acid-modified epoxy (meth)acrylate resin has a (meth)acryloyl group, in one embodiment, photoradical polymerization may be possible. The number of (meth)acryloyl groups per molecule of the acid-modified epoxy (meth)acrylate resin may be one or two or more.

The acid-modified epoxy (meth)acrylate resin preferably has both a (meth)acryloyl group and a carboxyl group, and is capable of photoradical polymerization and alkaline development.

The acid-modified epoxy (meth)acrylate resin can be produced by acid-modifying the epoxy (meth)acrylate resin by a known method. The epoxy (meth)acrylate resin can be produced, for example, by reacting the epoxy resin with acrylic acid or methacrylic acid.

The epoxy resin for producing the epoxy (meth)acrylate resin is not particularly limited as long as it is a compound having an epoxy group in the molecule, and examples thereof include bisphenol type epoxy resins such as bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol F type epoxy resin, bisphenol S type epoxy resin, and modified bisphenol F type epoxy resin obtained by reacting bisphenol F type epoxy resin with epichlorohydrin to modify it to have three or more functionalities; biphenol type epoxy resins such as biphenol type epoxy resin and tetramethylbiphenol type; novolac type epoxy resins such as phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A type novolac type epoxy resin, and alkylphenol novolac type epoxy resin; fluorine-containing epoxy resins such as bisphenol AF type epoxy resin and perfluoroalkyl type epoxy resin; naphthalene type epoxy resin, dihydroxynaphthalene type epoxy resin, polyhydroxybinaphthalene type epoxy resin, naphthol type epoxy resin, and naphthol aralkyl type epoxy resin. epoxy resins having a naphthalene skeleton, such as binaphthol type epoxy resins, naphthylene ether type epoxy resins, naphthol novolac type epoxy resins, and naphthalene type epoxy resins obtained by the condensation reaction of polyhydroxynaphthalene with aldehydes (epoxy resins containing a naphthalene skeleton); bixylenol type epoxy resins; dicyclopentadiene type epoxy resins; trisphenol type epoxy resins; tert-butyl-catechol type epoxy resins; epoxy resins containing a condensed ring skeleton, such as anthracene type epoxy resins; glycidylamine type epoxy resins resins; glycidyl ester type epoxy resins; biphenyl type epoxy resins; linear aliphatic epoxy resins; epoxy resins having a butadiene structure; alicyclic epoxy resins; heterocyclic epoxy resins; spiro ring-containing epoxy resins; cyclohexanedimethanol type epoxy resins; trimethylol type epoxy resins; tetraphenylethane type epoxy resins; glycidyl group-containing acrylic resins such as polyglycidyl (meth)acrylate and copolymers of glycidyl methacrylate and acrylic esters; fluorene type epoxy resins; halogenated epoxy resins, etc.

The epoxy resin for producing the epoxy (meth)acrylate resin is preferably an epoxy resin containing an aromatic skeleton, from the viewpoint of obtaining the effects of the present invention more significantly. Here, the aromatic skeleton is a concept including polycyclic aromatics and aromatic heterocycles. Among them, cresol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, and naphthol aralkyl type epoxy resin are preferred, and naphthol aralkyl type epoxy resin is more preferred.

In one embodiment, the acid-modified epoxy (meth)acrylate resin preferably contains an acid-modified epoxy (meth)acrylate resin having a skeleton selected from a naphthol aralkyl skeleton, a naphthalene skeleton, and a biphenyl skeleton, and particularly preferably contains an acid-modified epoxy (meth)acrylate resin having a naphthol aralkyl skeleton.

In one embodiment, the acid-modified epoxy (meth)acrylate resin preferably contains a resin selected from an acid-modified epoxy (meth)acrylate resin in which the hydroxyl group of the epoxy (meth)acrylate resin is esterified (hereinafter referred to as an "ester-type acid-modified epoxy (meth)acrylate resin") and an acid-modified epoxy (meth)acrylate resin in which the hydroxyl group of the epoxy (meth)acrylate resin is urethanized (hereinafter referred to as a "urethane-type acid-modified epoxy (meth)acrylate resin"), and particularly preferably contains an ester-type acid-modified epoxy (meth)acrylate resin.

The ester-type acid-modified epoxy (meth)acrylate resin can be produced, for example, by reacting an epoxy (meth)acrylate resin with a polycarboxylic acid anhydride. The ester-type acid-modified epoxy (meth)acrylate resin may be used alone or in combination of two or more types.

Examples of polyvalent carboxylic acid anhydrides include maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic dianhydride. Any one of these may be used alone, or two or more may be used in combination. Among these, succinic anhydride and tetrahydrophthalic anhydride are preferred, and tetrahydrophthalic anhydride is more preferred.

The ester-type acid-modified epoxy (meth)acrylate resin preferably contains a resin selected from a cresol novolac skeleton-containing ester-type acid-modified epoxy (meth)acrylate resin, a bisphenol A skeleton-containing ester-type acid-modified epoxy (meth)acrylate resin, a bisphenol F skeleton-containing ester-type acid-modified epoxy (meth)acrylate resin, a biphenyl skeleton-containing acid ester-type modified epoxy (meth)acrylate resin, and a naphthol aralkyl skeleton-containing ester-type acid-modified epoxy (meth)acrylate resin.

The ester-type acid-modified epoxy (meth)acrylate resin can be synthesized by a known method, but commercially available products may also be used. Specific examples of commercially available products include "CCR-1373H" (acid-modified epoxy acrylate resin containing a cresol novolac skeleton), "ZCR-8001H" (acid-modified epoxy acrylate resin containing a biphenyl skeleton), "ZCR-1569H" (acid-modified epoxy acrylate resin containing a biphenyl skeleton), "CCR-1171H" (acid-modified epoxy acrylate resin containing a cresol novolac skeleton), "ZCR-1797H", and "ZCR-1761H" (acid-modified epoxy acrylate resin containing a biphenyl skeleton), all manufactured by Nippon Kayaku Co., Ltd. modified epoxy acrylate resin), Nippon Kayaku's "ZAR-2000" (acid-modified epoxy acrylate resin containing bisphenol A skeleton), "ZFR-1491H", "ZFR-1533H" (acid-modified epoxy acrylate resin containing bisphenol F skeleton), Showa Denko's "PR-300CP" (cresol novolac-type acid-modified epoxy acrylate resin), Nippon Kayaku's "CCR-1179" (epoxy acrylate resin containing cresol novolac skeleton), etc.

The urethane-type acid-modified epoxy (meth)acrylate resin can be produced, for example, by reacting an epoxy (meth)acrylate resin with a diisocyanate compound and a carboxy group-containing diol compound. The urethane-type acid-modified epoxy (meth)acrylate resin may be used alone or in combination of two or more types.

Examples of diisocyanate compounds include aromatic diisocyanate compounds such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, diphenyl diisocyanate, and naphthalene diisocyanate; and aliphatic diisocyanate compounds such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, allylene sulfone ether diisocyanate, allyl cyanide diisocyanate, N-acyl diisocyanate, trimethylhexamethylene diisocyanate, and 1,3-bis(isocyanate methyl)cyclohexane.

Examples of carboxyl group-containing diol compounds include dimethylolpropionic acid, dimethylolbutanoic acid, and dimethylolnonanoic acid.

The urethane-type acid-modified epoxy (meth)acrylate resin preferably contains a resin selected from a cresol novolac skeleton-containing urethane-type acid-modified epoxy (meth)acrylate resin, a bisphenol A skeleton-containing urethane-type acid-modified epoxy (meth)acrylate resin, a bisphenol F skeleton-containing urethane-type acid-modified epoxy (meth)acrylate resin, a biphenyl skeleton-containing acid urethane-type modified epoxy (meth)acrylate resin, and a naphthol aralkyl skeleton-containing urethane-type acid-modified epoxy (meth)acrylate resin.

The urethane-type acid-modified epoxy (meth)acrylate resin can be synthesized by a known synthesis method, but a commercially available product may also be used. An example of a known synthesis method is the method described in JP 2016-199719 A. Specific examples of commercially available products include "UXE-3024", "UXE-3011", "UXE-3012", and "UXE-3024" manufactured by Nippon Kayaku Co., Ltd.

From the viewpoint of improving the alkaline developability of the photosensitive resin composition, the acid value of component (B) is preferably 0.1 mgKOH/g or more, more preferably 0.5 mgKOH/g or more, even more preferably 1 mgKOH/g or more, 10 mgKOH/g or more, even more preferably 20 mgKOH/g or more, 30 mgKOH/g or more, particularly preferably 40 mgKOH/g or more, 50 mgKOH/g or more. The upper limit of the acid value of component (B) is preferably 200 mgKOH/g or less, more preferably 150 mgKOH/g or less, even more preferably 120 mgKOH/g or less, particularly preferably 100 mgKOH/g or less.

The weight average molecular weight of component (B) is preferably 20,000 or less, more preferably 17,000 or less, and even more preferably 15,000 or less, and is preferably 500 or more, more preferably 750 or more, and even more preferably 900 or more. The weight average molecular weight is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

From the viewpoint of improving compatibility with the later-described component (D), it is preferable that the solubility parameter (SP value) of the component (B) is close to the SP value of the component (D). The SP value of the component (B) is preferably 9 (cal/ ^cm3 ) ^1/2 or more, more preferably 9.5 (cal/ ^cm3 ) ^1/2 or more, and preferably 11 (cal/ ^cm3 ) ^1/2 or less, more preferably 10.5 (cal/ ^cm3 ) ^1/2 or less. The SP value can be calculated using Fedors theory.

When the non-volatile components of the photosensitive resin composition are taken as 100% by mass, the content of component (B) is preferably 15% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 45% by mass or less, from the viewpoint of improving alkaline developability.

The mass ratio of the (B) component to the (A) epoxy resin (mass (% by mass) of the (B) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass/mass (% by mass) of the (A) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass) is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 1 or more. The upper limit is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less.

<(C) Photopolymerization initiator>
The photosensitive resin composition of the present invention contains a photopolymerization initiator (C) as the component (C). The photopolymerization initiator (C) is usually capable of generating radicals when exposed to light. The photopolymerization initiator (C) as the component (C) does not include those corresponding to the above-mentioned components (A) and (B). The component (C) may be used alone or in combination of two or more types.

As the (C) component, a photopolymerization initiator capable of efficiently photocuring the photosensitive resin composition can be used. Such a photopolymerization initiator preferably includes either (C1) a photopolymerization initiator having a molecular weight of 420 or more, or (C2) a photopolymerization initiator having a molecular weight of less than 420. Although the (C1) component and the (C2) component may be used in combination, from the viewpoint of obtaining the effects of the present invention significantly, the (C) component preferably includes either the (C1) component or the (C2) component, and more preferably includes the (C2) component.

-(C1) Photopolymerization initiator having a molecular weight of 420 or more-
The molecular weight of the component (C1), from the viewpoint of being able to form a fine core layer and producing an optical waveguide with small optical transmission loss, is usually at least 420, preferably at least 500, more preferably at least 600, or even more preferably at least 700. There is no particular upper limit, but it is preferably at most 3000, more preferably at most 2500, and even more preferably at most 2000.

（式中、Ｒ^１は活性光線吸収基を表し、Ｒ^２はそれぞれ独立に２価の炭化水素基を表す。ｎは１～１０の整数を表す。＊は結合手を表す。） As the component (C1), a compound having a molecular weight of 420 or more, containing a group that absorbs actinic rays such as ultraviolet rays, and capable of efficiently promoting photopolymerization can be used. As such a component (C1), for example, a compound containing a structural unit represented by formula (C-1) can be preferably used.

(In the formula, ^R1 represents an actinic ray absorbing group, each ^R2 independently represents a divalent hydrocarbon group, n represents an integer of 1 to 10, and * represents a bond.)

R ¹ represents an active light absorbing group. The active light absorbing group is a group that can absorb active light such as ultraviolet light. The active light absorbing group may be any functional group that can absorb active light, and examples thereof include a group having an aminoketone skeleton, a group having an anthraquinone skeleton, a group having a thioxanthone skeleton, a group having a ketal skeleton, a group having a benzophenone skeleton, a group having a xanthone skeleton, a group having an acetophenone skeleton, a group having a benzoin skeleton, a group having a thioxanthone skeleton, and a group having a benzoate skeleton.

Specific examples of the active light absorbing group include the following groups (i) to (vii). Among them, the active light absorbing group is preferably either (i) or (ii). In the formula, * represents a bond.

^Each R2 independently represents a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include a divalent aliphatic hydrocarbon group and a divalent aromatic hydrocarbon group. From the viewpoint of obtaining the effects of the present invention remarkably, a divalent aliphatic hydrocarbon group is preferable.

As the divalent aliphatic hydrocarbon group, a divalent saturated aliphatic hydrocarbon group is preferred, and examples thereof include an alkylene group and an alkenylene group, with an alkylene group being more preferred. The alkylene group may be linear, branched, or cyclic, with a linear group being preferred. As the alkylene group, an alkylene group having 1 to 10 carbon atoms is preferred, an alkylene group having 1 to 6 carbon atoms is more preferred, and an alkylene group having 1 to 5 carbon atoms or an alkylene group having 1 to 3 carbon atoms is even more preferred. Examples of such alkylene groups include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, and a cyclohexylene group, with a methylene group being preferred. The alkenylene group may be linear, branched, or cyclic, with a linear group being preferred. As the alkenylene group, an alkenylene group having 2 to 10 carbon atoms is preferable, an alkenylene group having 2 to 6 carbon atoms is more preferable, and an alkenylene group having 2 to 5 carbon atoms is even more preferable.

Examples of divalent aromatic hydrocarbon groups include arylene groups and heteroarylene groups. As the arylene group and heteroarylene group, an arylene group or heteroarylene group having 6 to 20 carbon atoms is preferable, and an arylene group or heteroarylene group having 6 to 10 carbon atoms is more preferable.

The divalent hydrocarbon group may have a substituent. Examples of the substituent include a halogen atom, an alkyl group, an alkoxy group, an aryl group, an arylalkyl group, a silyl group, an acyl group, an acyloxy group, a carboxy group, a sulfo group, a cyano group, a nitro group, a hydroxy group, a mercapto group, and an oxo group.

n represents an integer from 1 to 10, preferably an integer from 1 to 8, more preferably an integer from 1 to 5, and even more preferably an integer from 1 to 3.

（一般式（Ｃ－２）中、Ｒ^１１はそれぞれ独立に活性光線吸収基を表し、Ｒ^１２はそれぞれ独立に２価の炭化水素基を表し、Ｒ^１３はｍ価の炭化水素基を表す。ｎ１は１～１０の整数を表し、ｍは１～４の整数を表す。
一般式（Ｃ－３）中、Ｒ^２１、Ｒ^２３はそれぞれ独立に活性光線吸収基を表し、Ｒ^２２はそれぞれ独立に２価の炭化水素基を表す。ｎ２は１～１０の整数を表す。） The component (C1) preferably contains either a compound represented by the following general formula (C-2) or a compound represented by the following general formula (C-3).

In formula (C-2), R ¹¹ each independently represents an actinic ray absorbing group, R ¹² each independently represents a divalent hydrocarbon group, and R ¹³ represents an m-valent hydrocarbon group. n1 represents an integer from 1 to 10, and m represents an integer from 1 to 4.
In formula (C-3), R ²¹ and R ²³ each independently represent an actinic ray absorbing group, and R ²² each independently represent a divalent hydrocarbon group. n2 represents an integer of 1 to 10.

Each R ¹¹ independently represents an actinic ray absorbing group and is the same as the actinic ray absorbing group represented by R ¹ in formula (C-1).

Each R ¹² independently represents a divalent hydrocarbon group and is the same as the divalent hydrocarbon group represented by R ² in formula (C-1).

R ¹³ represents an m-valent hydrocarbon group. Examples of the m-valent hydrocarbon group include an m-valent aliphatic hydrocarbon group and an m-valent aromatic hydrocarbon group, and an m-valent aliphatic hydrocarbon group is preferred. For example, when m is 3, a trivalent group obtained by removing three hydrogen atoms from an alkane is preferred. Specific examples of the group represented by R ¹³ include the following. In the formula, "*" represents a bond.

n1 represents an integer from 1 to 10 and is the same as n in formula (C-1).

m represents an integer from 1 to 4, preferably an integer from 1 to 3, and more preferably 3.

R ²¹ and R ²³ each independently represent an actinic ray absorbing group and are the same as the actinic ray absorbing group represented by R ¹ in formula (C-1).

Each R ²² independently represents a divalent hydrocarbon group and is the same as the divalent hydrocarbon group represented by R ² in formula (C-1).

Specific examples of the component (C1) include the following compounds. However, the component (C1) is not limited to these specific examples. a, b, c, and d each represent an integer of 1 to 10.

Component (C1) may be a commercially available product. Examples of commercially available products include "Omnipol 910", "Omnipol TP", and "Omnipol 9210" manufactured by IGM.

From the viewpoint of obtaining a significant effect of the present invention, the content of component (C1) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, 1% by mass or more, and preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 5% by mass or less, based on 100% by mass of the non-volatile components of the photosensitive resin composition.

-(C2) Photopolymerization initiator having a molecular weight of less than 420-
From the viewpoint of obtaining the effects of the present invention prominently, the molecular weight of the (C2) component is less than 420, preferably 418 or less, and more preferably 415 or less. There is no particular lower limit, but it is preferably 100 or more, more preferably 200 or more, and even more preferably 300 or more.

Examples of component (C2) include oxime ester-based photopolymerization initiators, α-aminoketone-based photopolymerization initiators, phosphine oxide-based photopolymerization initiators, α-hydroxyketone-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl ketal-based photopolymerization initiators, and acylphosphine-based photopolymerization initiators.

Examples of oxime ester photopolymerization initiators include 2-(benzoyloxyimino)-1-[4-(phenylthio)phenyl]octan-1-one (OXE01), [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]ethylideneamino]acetate (OXE02), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), etc.

Examples of α-aminoketone photopolymerization initiators include 2-methyl-1-phenyl-2-morpholinopropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-methyl-1-(4-hexylphenyl)-2-morpholinopropan-1-one, 2-ethyl-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, 2-benzyl-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, 2-(dimethylamino)-2-(4-methylphenylmethyl)-1-(4-morpholinophenyl)butan-1-one, and 2-methyl-1-(9,9-dibutylfluoren-2-yl)-2-morpholinopropan-1-one.

Examples of phosphine oxide photopolymerization initiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, polyoxyethylene glycerin ether tris[phenyl(2,4,6-trimethylbenzoyl)phosphinate] (Polymeric TPO-L), etc.

Examples of α-hydroxyketone photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, etc.

Examples of benzoin-based photopolymerization initiators include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether. Examples of benzil ketal-based photopolymerization initiators include 2,2-dimethoxy-2-phenylacetophenone.

Examples of acylphosphine photopolymerization initiators include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

In one embodiment, from the viewpoint of obtaining the effects of the present invention more prominently, it is preferable that the (C2) component contains any one of an oxime ester-based photopolymerization initiator, an α-aminoketone-based photopolymerization initiator, and an acylphosphine-based photopolymerization initiator.

Component (C2) may be a commercially available product. Specific examples of commercially available products of component (C2) include "Omnirad 907", "Omnirad 369", "Omnirad 379", "Omnirad 379EG", "Omnirad 819", and "Omnirad TPO" manufactured by IGM, "Irgacure TPO", "Irgacure OXE-01", and "Irgacure OXE-02" manufactured by BASF, and "N-1919" manufactured by ADEKA.

From the viewpoint of obtaining a significant effect of the present invention, the content of component (C2) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, 1% by mass or more, and preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 5% by mass or less, based on 100% by mass of the non-volatile components of the photosensitive resin composition.

From the viewpoint of obtaining a significant effect of the present invention, the content of the (C) component (the total content of the (C1) component and the (C2) component) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, 1% by mass or more, and is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less, when the non-volatile components of the photosensitive resin composition are taken as 100% by mass.

The mass ratio of the (C) component to the (A) epoxy resin (mass (% by mass) of the (C) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass/mass (% by mass) of the (A) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass) is preferably 0.001 or more, more preferably 0.005 or more, and even more preferably 0.1 or more, from the viewpoint of obtaining a significant effect of the present invention. The upper limit is preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.3 or less.

The mass ratio of component (C) to resin (B) containing a carboxy group and an ethylenic double bond (mass (% by mass) of component (C) when the non-volatile components of the photosensitive resin composition are taken as 100% by mass/mass (% by mass) of component (B) when the non-volatile components of the photosensitive resin composition are taken as 100% by mass) is preferably 0.0001 or more, more preferably 0.001 or more, and even more preferably 0.01 or more, from the viewpoint of obtaining a significant effect of the present invention. The upper limit is preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.1 or less.

The photosensitive resin composition may contain, in combination with component (C), tertiary amines such as N,N-dimethylaminobenzoic acid ethyl ester, N,N-dimethylaminobenzoic acid isoamyl ester, pentyl-4-dimethylaminobenzoate, triethylamine, and triethanolamine as photopolymerization initiator assistants. One type of photopolymerization initiator assistant may be used alone, or two or more types may be used in combination.

<(D) Non-developable polymer having a solubility parameter (SP value) of 9 (cal/cm ³ ) ^1/2 or more and 13 (cal/cm ³ ) ^1/2 or less>
The photosensitive resin composition of the present invention contains, as the (D) component, a non-developable polymer having a (D) solubility parameter of 9 (cal/cm ³ ) ^1/2 or more and 13 (cal/cm ³ ) ^1/2 or less. The non-developable polymer is a polymer having a solubility parameter in a specific range of 9 (cal/cm ³ ) ^1/2 or more and 13 (cal/cm ³ ) ^1/2 or less, and is usually less soluble in a developer than the (A) component and the (B) component. This (D) component is usually highly compatible with the (A) component and the (B) component, and further, can have high solubility in a chemical solution used in the roughening treatment. The non-developable polymer having a (D) SP value of 9 (cal/cm ³ ) ^1/2 or more and 13 (cal/cm ³ ) ^1/2 or less as the (D) component does not include those corresponding to the above-mentioned (A) to (C) components. The component (D) may be used alone or in combination of two or more types.

From the viewpoint of obtaining a cured product of the photosensitive resin composition having excellent plating adhesion, the SP value of component (D) is 9 (cal/ ^cm3 ) ^1/2 or more, preferably 9.1 (cal/ ^cm3 ) ^1/2 or more, and more preferably 9.2 (cal/ ^cm3 ) ^1/2 or more. The upper limit of the SP value of component (D) is 13 (cal/ ^cm3 ) ^1/2 or less, preferably 12.9 (cal/ ^cm3 ) ^1/2 or less, and more preferably 12.8 (cal/ ^cm3 ) ^1/2 or less. The SP value can be calculated using Fedors theory.

As the component (D), a polymer having an SP value within the above range and insoluble in the developer can be used, for example, an acrylic polymer having an SP value of 9 (cal/cm ³ ) ^1/2 or more and 13 (cal/cm ³ ) ^1/2 or less.

From the viewpoint of obtaining a cured product with excellent plating adhesion, the acrylic polymer is preferably a copolymer containing structural units derived from an oxyalkylene group-containing alkyl (meth)acrylate monomer and structural units derived from an alkyl (meth)acrylate monomer.

The number of carbon atoms in the oxyalkylene group of the oxyalkylene group-containing alkyl (meth)acrylate monomer is preferably 2 or 3, and more preferably 2. The number of repeating units in the oxyalkylene group is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, and is preferably 50 or less, more preferably 40 or less, and even more preferably 30 or less.

The number of carbon atoms in the acrylic group of the alkyl (meth)acrylate monomer is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more, and is preferably 22 or less, more preferably 21 or less, and even more preferably 20 or less.

The acrylic polymer may be a copolymer containing structural units derived from an oxyalkylene group-containing alkyl (meth)acrylate monomer, structural units derived from an alkyl (meth)acrylate monomer, and structural units derived from a vinyl ether monomer.

The number of carbon atoms in the acrylic group of the vinyl ether monomer is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more, and is preferably 22 or less, more preferably 21 or less, and even more preferably 20 or less.

式（Ｄ－１）中、Ｒ^１は、それぞれ独立に水素原子又はメチル基を表し、Ｒ^２は、それぞれ独立に水素原子、又は炭素原子数１～２２のアルキル基を表す。ｐは、それぞれ独立に２～４の整数を表し、ｑは２～１００の整数を表す。
式（Ｄ－２）中、Ｒ^３は、それぞれ独立に水素原子又はメチル基を表し、Ｒ^４は、それぞれ独立に炭素原子数１～２２のアルキル基を表す。 The component (D) is preferably a copolymer having a structural unit represented by formula (D-1) and a structural unit represented by the following formula (D-2).

In formula (D-1), R ¹ 's each independently represent a hydrogen atom or a methyl group, and R ² 's each independently represent a hydrogen atom or an alkyl group having 1 to 22 carbon atoms. p's each independently represent an integer of 2 to 4, and q's each independently represent an integer of 2 to 100.
In formula (D-2), R ³ 's each independently represent a hydrogen atom or a methyl group, and R ⁴ 's each independently represent an alkyl group having 1 to 22 carbon atoms.

The structural unit represented by formula (D-1) is a structural unit derived from an oxyalkylene group-containing alkyl (meth)acrylate monomer. The structural unit represented by formula (D-2) is a structural unit derived from an alkyl (meth)acrylate monomer.

R ¹ and R ³ each independently represent a hydrogen atom or a methyl group, and preferably a hydrogen atom.

R ² each independently represents a hydrogen atom or an alkyl group having 1 to 22 carbon atoms, and preferably an alkyl group having 1 to 22 carbon atoms. The alkyl group may be linear, branched, or cyclic, and is preferably linear. The number of carbon atoms in the alkyl group is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 6. Examples of the alkyl group represented by R ² include a methyl group, an ethyl group, a propyl group, an n-butyl group, an iso-butyl group, a t-butyl group, an n-amyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, an isopropyl group, an isobutyl group, an isoamyl group, an isohexyl group, an isoheptyl group, an isooctyl group, an isononyl group, an isodecyl group, an isoundecyl group, an isododecyl group, a neopentyl group, a t-amyl group, a sec-amyl group, and a 2-ethylhexyl group.

Each R ⁴ independently represents an alkyl group having 1 to 22 carbon atoms and is the same as the alkyl group having 1 to 22 carbon atoms represented by R ² .

Each p independently represents an integer from 2 to 4, preferably 2 or 3, and more preferably 2.

q represents the number of repeats of the oxyalkylene group and is an integer from 2 to 100. q is preferably an integer from 3 to 50.

The content ratio of the structural unit represented by formula (D-1) and the structural unit represented by formula (D-2) in the (D) component (structural unit represented by formula (D-1):structural unit represented by formula (D-2)) is preferably 5:95 to 80:20.

式（Ｄ－３）中、Ｒ^５は、炭素原子数２～２２のアルキル基を表す。 The component (D) may be a copolymer containing a structural unit represented by formula (D-1), a structural unit represented by formula (D-2), and a structural unit represented by formula (D-3). The structural unit represented by formula (3) is a structural unit derived from a vinyl ether monomer.

In formula (D-3), R ⁵ represents an alkyl group having 2 to 22 carbon atoms.

^R5 represents an alkyl group having 2 to 22 carbon atoms. The alkyl group may be linear, branched, or cyclic, and is preferably linear. The number of carbon atoms in the alkyl group is preferably 2 to 20, more preferably 2 to 10, and even more preferably 2 to 6. Examples of the alkyl group represented by ^R5 include a methyl group, an ethyl group, an n-butyl group, an iso-butyl group, a t-butyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a hexyl group, an octadecyl group, a propyl group, an isopropyl group, a 2-ethylhexyl group, and a cyclohexyl group.

When component (D) is a copolymer containing a structural unit represented by formula (D-3), the content ratio (structural unit represented by formula (D-1) and structural unit represented by formula (D-2) below: structural unit represented by formula (D-3)) is preferably 100:1 to 45, and more preferably 100:5 to 40.

The component (D) may be a copolymer containing structural units other than the structural units represented by formula (D-1), the structural units represented by the following formula (D-2), and the structural units represented by formula (D-3) (structural units other than the structural units represented by formulas (D-1) to (D-3)) as necessary.

When component (D) is a copolymer containing structural units other than those represented by formulas (D-1) to (D-3), the content ratio (structural units represented by formulas (D-1) to (D-3):structural units other than those represented by formulas (D-1) to (D-3)) is preferably 100:1 to 40.

式（Ｄ－１ａ）中、Ｒ^１ａは、それぞれ独立に水素原子又はメチル基を表し、Ｒ^２ａは、水素原子、又は炭素原子数１～２２のアルキル基を表す。ｒは、それぞれ独立に２～４の整数を表し、ｓは２～１００の整数を表す。
式（Ｄ－２ａ）中、Ｒ^３ａは、それぞれ独立に水素原子又はメチル基を表し、Ｒ^４ａは、炭素原子数１～２２のアルキル基を表す。 The component (D) can be produced, for example, by copolymerizing an oxyalkylene group-containing alkyl (meth)acrylate monomer represented by the following formula (D-1a) and an alkyl (meth)acrylate monomer represented by the following formula (D-2a).

In formula (D-1a), R ^1a each independently represents a hydrogen atom or a methyl group, and R ^2a each independently represents a hydrogen atom or an alkyl group having 1 to 22 carbon atoms. Each r each independently represents an integer of 2 to 4, and s each independently represents an integer of 2 to 100.
In formula (D-2a), R ^3a each independently represents a hydrogen atom or a methyl group, and R ^4a represents an alkyl group having 1 to 22 carbon atoms.

Each R ^1a independently represents a hydrogen atom or a methyl group and is the same as R ¹ in formula (D-1). Each R ^3a independently represents a hydrogen atom or a methyl group and is the same as R ³ in formula (D-2).

R ^2a represents a hydrogen atom or an alkyl group having 1 to 22 carbon atoms and is the same as R ² in formula (D-1).

R ^4a represents an alkyl group having 1 to 22 carbon atoms and is the same as R ⁴ in formula (D-2).

Each r independently represents an integer from 2 to 4 and is the same as p in formula (D-1).

s represents an integer from 2 to 100 and is the same as q in formula (D-1).

Examples of the oxyalkylene group-containing alkyl (meth)acrylate monomer represented by formula (D-1a) include polyethylene glycol (meth)acrylate (polymerization number of ethylene glycol is 2 to 100) ester, polypropylene glycol (meth)acrylate (polymerization number of propylene glycol is 2 to 100) ester, poly(ethylene-propylene)glycol (ethylene glycol-propylene glycol polymerization number is 2 to 100) ester, poly(ethylene-tetramethylene)glycol (ethylene glycol-tetramethylene glycol polymerization number is 2 to 100) ester, methoxypolyethylene glycol (meth)acrylate (polymerization number of ethylene glycol is 2 to 100) ester, methoxypolypropylene glycol (meth)acrylate (polymerization number of propylene glycol is 2 to 100) ester, methoxypoly(ethylene-propylene)glycol (ethylene glycol-propylene glycol) (meth)acrylate (meth)acrylate Examples of ether group-containing alkyl (meth)acrylates include methoxypoly(ethylene-tetramethylene)glycol (ethylene glycol-tetramethylene glycol polymerization number 2-100) ester, butoxypoly(ethylene-propylene)glycol (ethylene glycol-propylene glycol polymerization number 2-100) ester, octoxypoly(ethylene-propylene)glycol (ethylene glycol-propylene glycol polymerization number 2-100) ester, lauroxypolyethylene glycol (meth)acrylate (ethylene glycol polymerization number 2-100) ester, stearoxypolyethylene glycol (meth)acrylate (ethylene glycol polymerization number 2-100) ester, and phenoxypolyethylene glycol (ethylene glycol polymerization number 2-100) ester.

Examples of the alkyl (meth)acrylate monomer represented by formula (D-2a) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-, iso-, or tert-butyl (meth)acrylate, n-amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isopropyl (meth)acrylate, Examples of the alkyl (meth)acrylates include isobutyl (meth)acrylate, isoamyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, neopentyl (meth)acrylate, tert-amyl (meth)acrylate, sec-amyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. The alkyl (meth)acrylate monomer may be used alone or in combination.

The oxyalkylene group-containing alkyl (meth)acrylate monomer is preferably used in an amount of 5 parts by mass or more and 80 parts by mass or less when the total amount of the oxyalkylene group-containing alkyl (meth)acrylate monomer and the alkyl (meth)acrylate monomer is 100 parts by mass.

The alkyl (meth)acrylate monomer is preferably used in an amount of 20 parts by mass or more and 95 parts by mass or less when the total amount of the oxyalkylene group-containing alkyl (meth)acrylate monomer and the alkyl (meth)acrylate monomer is 100 parts by mass.

式（Ｄ－３ａ）中、Ｒ^５ａは、炭素原子数２～２２のアルキル基を表す。 The component (D) may be produced by copolymerizing, in addition to the oxyalkylene group-containing alkyl (meth)acrylate monomer and the alkyl (meth)acrylate monomer, a vinyl ether monomer represented by the following formula (D-3a):

In formula (D-3a), R ^5a represents an alkyl group having 2 to 22 carbon atoms.

R ^5a represents an alkyl group having 2 to 22 carbon atoms and is the same as R ⁵ in formula (D-3).

Examples of the vinyl ether monomer represented by formula (D-3a) include alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-, iso-, or tert-butyl vinyl ether, octyl vinyl ether, nonyl vinyl ether, decyl vinyl ether, undecyl vinyl ether, dodecyl vinyl ether, hexavinyl ether, octadecyl vinyl ether, isopropyl vinyl ether, n-propyl vinyl ether, 2-ethylhexyl vinyl ether, and cyclohexyl vinyl ether. These vinyl ether monomers may be used alone or in combination.

When a vinyl ether monomer is copolymerized, the mass ratio of the total amount of the oxyalkylene group-containing alkyl (meth)acrylate monomer and the alkyl (meth)acrylate monomer to the vinyl ether monomer (total amount of the oxyalkylene group-containing alkyl (meth)acrylate monomer and the alkyl (meth)acrylate monomer:vinyl ether monomer) is preferably 100:1-45, more preferably 100:5-40.

Component (D) may be produced, if necessary, by copolymerizing a monomer other than an oxyalkylene group-containing alkyl (meth)acrylate monomer, an alkyl (meth)acrylate monomer, and a vinyl ether monomer.

Examples of such monomers include (meth)acrylic acids such as acrylic acid or methacrylic acid; (meth)acrylic acid aralkyl esters such as (meth)acrylic acid hydroxyalkyl esters, acrylic acid benzyl esters, polycaprolactone-modified hydroxyalkyl acrylic esters or methacrylic esters, and (meth)acrylic acid phenoxyethyl ester; (meth)acrylamides such as acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, diacetone acrylamide, and acroylmorpholine; aromatic hydrocarbon vinyl compounds such as styrene, α-methylstyrene, chlorostyrene, and vinyl toluene; vinyl esters such as vinyl acetate and vinyl propionate; allyl compounds such as diallyl phthalate; and aliphatic hydrocarbon vinyl compounds such as vinyl chloride, vinylidene chloride, chloroprene, propylene, butadiene, isoprene, and fluoroolefin maleimide. These may be used alone or in combination.

When such monomers are copolymerized, the ratio of the amounts is preferably such that the mass ratio of the total amount of the oxyalkylene group-containing alkyl (meth)acrylate monomer, the alkyl (meth)acrylate monomer, and the vinyl ether monomer to the monomer (total amount of the oxyalkylene group-containing alkyl (meth)acrylate monomer, the alkyl (meth)acrylate monomer, and the vinyl ether monomer:the monomer) is 100:1 to 40.

Methods for synthesizing component (D) include, for example, emulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization. Specifically, each monomer that is a copolymerization component is randomly copolymerized by dropping it into a solvent in the presence of a radical polymerization initiator and heating it. Alternatively, each monomer that is a copolymerization component may be block-copolymerized by dropping it in sequence into a solvent in the presence of a block copolymerization initiator and heating it. Component (D) may be any of a random copolymer, a block copolymer, and a graft copolymer.

The radical polymerization initiator is not particularly limited as long as it is an initiator generally used in radical polymerization. Examples of radical polymerization initiators include peroxides and azo compounds, such as Perbutyl D, Perbutyl O, and Perocta O manufactured by NOF Corporation. Examples of block copolymerization initiators include two-stage decomposition type bifunctional initiators, such as 1,1-bis-(tert-butylperoxy)-2-methylcyclohexane.

Component (D) may be a commercially available product. Examples of commercially available products include "Polyflow WS-314", "Polyflow No. 99C", "Polyflow No. 77", and "Polyflow No. 75" manufactured by Kyoeisha Chemical Co., Ltd.

From the viewpoint of obtaining a significant effect of the present invention, the weight average molecular weight of component (D) is preferably 3,000 or more, more preferably 3,500 or more, even more preferably 4,000, and is preferably 500,000 or less, more preferably 50,000 or less, even more preferably 25,000 or less. The weight average molecular weight can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

The content of component (D) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, from the viewpoint of improving plating adhesion, when the non-volatile components of the photosensitive resin composition are taken as 100% by mass, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

The mass ratio of the (D) component to the (A) epoxy resin (mass (% by mass) of the (D) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass/mass (% by mass) of the (A) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass) is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more, from the viewpoint of obtaining a significant effect of the present invention. The upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less.

The mass ratio of the (D) component to the (B) resin containing a carboxy group and an ethylenic double bond (mass (% by mass) of the (D) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass/mass (% by mass) of the (B) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass) is preferably 0.001 or more, more preferably 0.005 or more, and even more preferably 0.01 or more, from the viewpoint of obtaining a significant effect of the present invention. The upper limit is preferably 1 or less, more preferably 0.1 or less, and even more preferably 0.05 or less.

The mass ratio of the (D) component to the (C) photopolymerization initiator (mass (% by mass) of the (D) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass/mass (% by mass) of the (C) component when the non-volatile components of the photosensitive resin composition are taken as 100% by mass) is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.1 or more, from the viewpoint of obtaining a significant effect of the present invention. The upper limit is preferably 50 or less, more preferably 20 or less, and even more preferably 10 or less, 5 or less, 1 or less, 0.5 or less, or 0.1 or less.

<(E) Inorganic filler having an average particle size of 100 nm or less>
The photosensitive resin composition of the present invention may contain, as an optional component, (E) an inorganic filler having an average particle size of 100 nm or less. (E) The inorganic filler is contained in the photosensitive resin composition in the form of particles.

The average particle size of component (E) is 100 nm or less, preferably 90 nm or less, more preferably 80 nm or less, and is preferably 5 nm or more, more preferably 10 nm or more, from the viewpoint of suppressing light reflection during exposure and obtaining excellent core forming properties and developability.

The average particle size of the inorganic filler can be measured by a laser diffraction/scattering method based on the Mie scattering theory. Specifically, a particle size distribution of the inorganic filler is created on a volume basis using a laser diffraction/scattering particle size distribution measuring device, and the median diameter is taken as the average particle size. The measurement sample can be prepared by weighing 100 mg of inorganic filler and 10 g of methyl ethyl ketone into a vial and dispersing the mixture ultrasonically for 10 minutes. The measurement sample is measured using a laser diffraction particle size distribution measuring device with blue and red light wavelengths as the light source, and the volume-based particle size distribution of the inorganic filler is measured using a flow cell method, and the average particle size is calculated as the median diameter from the particle size distribution obtained. An example of a laser diffraction particle size distribution measuring device is the "LA-960" manufactured by Horiba, Ltd.

From the viewpoint of suppressing light reflection during exposure and obtaining excellent core formability, the specific surface area of component (E) is preferably 1 m ² /g or more, more preferably 3 m ² /g or more, and particularly preferably 5 m ² /g or more. There is no particular upper limit, but it is preferably 60 m ² /g or less, 50 m ² /g or less, or 40 m ² /g or less. The specific surface area is obtained by adsorbing nitrogen gas to the surface of a sample using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) according to the BET method, and calculating the specific surface area using the BET multipoint method.

As the material for component (E), an inorganic compound is used. Examples of the material for component (E) include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium zirconate titanate, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. Among these, silica is particularly suitable. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. In addition, spherical silica is preferable as the silica. Component (E) may be used alone or in any combination of two or more types in any ratio.

Component (E) can be a commercially available product. Examples of such commercially available products include the "Admanano series" manufactured by Admatechs, such as Y50SZ-AM1, the "UFP series" manufactured by Denki Kagaku Kogyo Co., Ltd., the "Sciqas series" manufactured by Sakai Chemical Industry Co., Ltd., the "Seahoster series" manufactured by Nippon Shokubai Co., Ltd., and the "BF series" manufactured by Sakai Chemical Industry Co., Ltd.

From the viewpoint of improving moisture resistance and dispersibility, it is preferable that component (E) is treated with a surface treatment agent. Examples of surface treatment agents include fluorine-containing silane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, alkoxysilanes, organosilazane compounds, and titanate coupling agents. In addition, the surface treatment agents may be used alone or in any combination of two or more types.

Examples of commercially available surface treatment agents include Shin-Etsu Chemical's "KBM403" (3-glycidoxypropyltrimethoxysilane), Shin-Etsu Chemical's "KBM803" (3-mercaptopropyltrimethoxysilane), Shin-Etsu Chemical's "KBE903" (3-aminopropyltriethoxysilane), Shin-Etsu Chemical's "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), Shin-Etsu Chemical's "SZ-31" (hexamethyldisilazane), Shin-Etsu Chemical's "KBM103" (phenyltrimethoxysilane), Shin-Etsu Chemical's "KBM-4803" (long-chain epoxy-type silane coupling agent), and Shin-Etsu Chemical's "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane).

From the viewpoint of improving the dispersibility of the inorganic filler, it is preferable that the degree of surface treatment with the surface treatment agent falls within a specified range. Specifically, it is preferable that 100% by mass of the inorganic filler is surface-treated with 0.2% to 5% by mass of the surface treatment agent, more preferably 0.2% to 3% by mass, and even more preferably 0.3% to 2% by mass.

The degree of surface treatment by the surface treatment agent can be evaluated by the amount of carbon per unit surface area of the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of the inorganic filler is preferably 0.02 mg/m ² or more, more preferably 0.1 mg/m ² or more, and even more preferably 0.2 mg/m ² or more. On the other hand, from the viewpoint of preventing an increase in the melt viscosity of the resin composition or the melt viscosity in the sheet form, it is preferably 1.0 mg/m ² or less, more preferably 0.8 mg/m ² or less, and even more preferably 0.5 mg/m ² or less.

The carbon amount per unit surface area of component (E) can be measured after the surface-treated inorganic filler is washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to the inorganic filler that has been surface-treated with the surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solids, the carbon amount per unit surface area of the inorganic filler can be measured using a carbon analyzer. An example of a carbon analyzer that can be used is the "EMIA-320V" manufactured by Horiba, Ltd.

The content of component (E) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on 100% by mass of non-volatile components in the photosensitive resin composition, from the viewpoint of obtaining a significant effect of the present invention, and is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.

<(F) Reactive Diluent>
The photosensitive resin composition of the present invention may contain a reactive diluent (F) as an optional component. The reactive diluent (F) as component (F) does not include those corresponding to the above-mentioned components (A) to (E). One type of component (F) may be used alone, or two or more types may be used in combination.

By adding a reactive diluent (F) to the photosensitive resin composition, the photoreactivity can be improved. As the reactive diluent (F), for example, a (meth)acrylate compound having one or more (preferably two or more) (meth)acryloyl groups in one molecule can be used.

Representative (meth)acrylate compounds include, for example, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxybutyl acrylate; mono- or diacrylates of glycols such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, and propylene glycol; acrylamides such as N,N-dimethylacrylamide and N-methylolacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate; polyhydric alcohols such as trimethylolpropane, pentaerythritol, and dipentaerythritol, or polyhydric acrylates of their ethylene oxide, propylene oxide, or ε-caprolactone adducts; phenols such as phenoxy acrylate and phenoxyethyl acrylate, or acrylates such as their ethylene oxide or propylene oxide adducts; epoxy acrylates derived from glycidyl ethers such as trimethylolpropane triglycidyl ether; modified epoxy acrylates; melamine acrylates; and/or methacrylates corresponding to the above acrylates. Among these, polyvalent acrylates or polyvalent methacrylates are preferred. For example, trivalent acrylates or methacrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane EO-added tri(meth)acrylate, glycerol PO-added tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, tetrafurfuryl alcohol oligo(meth)acrylate, ethyl carbitol oligo(meth)acrylate, 1,4-butanediol oligo(meth)acrylate, 1,6-hexanediol oligo(meth)acrylate, trimethylolpropane oligo(meth)acrylate, pentaerythritol oligo(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, Examples of the photosensitive (meth)acrylate compounds include hexa(meth)acrylate and (meth)acrylic acid ester of N,N,N',N'-tetrakis(β-hydroxyethyl)ethyldiamine, and examples of the trivalent or higher acrylates or methacrylates include phosphate triester (meth)acrylates such as tri(2-(meth)acryloyloxyethyl)phosphate, tri(2-(meth)acryloyloxypropyl)phosphate, tri(3-(meth)acryloyloxypropyl)phosphate, tri(3-(meth)acryloyl-2-hydroxyloxypropyl)phosphate, di(3-(meth)acryloyl-2-hydroxyloxypropyl)(2-(meth)acryloyloxyethyl)phosphate, and (3-(meth)acryloyl-2-hydroxyloxypropyl)di(2-(meth)acryloyloxyethyl)phosphate. Any one of these photosensitive (meth)acrylate compounds may be used alone, or two or more of them may be used in combination. "EO" refers to ethylene oxide.

(F) Commercially available reactive diluents can be used. Examples of commercially available products include "DPHA" manufactured by Nippon Kayaku Co., Ltd. and "EBECRYL3708" manufactured by Daicel Allnex Co., Ltd.

(F) The reactive diluent usually has a low viscosity. The specific viscosity of the (F) reactive diluent is usually less than 0.5 Pa·s. There is no particular limit to the lower limit of the viscosity of the (F) reactive diluent, and it may be, for example, 0.001 Pa·s or more, 0.005 Pa·s or more, 0.01 Pa·s or more, etc. The viscosity of the (F) reactive diluent may be measured using an E-type viscometer at 25±2°C.

The content of (F) reactive diluent is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of non-volatile components in the photosensitive resin composition, from the viewpoint of promoting photocuring, and is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less.

<(G) Solvent>
The photosensitive resin composition may contain a (G) solvent as a volatile component in combination with the above-mentioned (A) to (F) components as non-volatile components. The (G) solvent as the (G) component can adjust the viscosity of the photosensitive resin composition. Examples of the (G) solvent include organic solvents.

(G) Solvents include, for example, ketone solvents such as ethyl methyl ketone (MEK) and cyclohexanone; aromatic hydrocarbon solvents such as toluene, xylene, and tetramethylbenzene; glycol ether solvents such as methyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; ester solvents such as ethyl acetate, butyl acetate, butyl cellosolve acetate, carbitol acetate, and ethyl diglycol acetate; ether ester solvents such as propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate; aliphatic hydrocarbon solvents such as octane and decane; and petroleum-based solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. (G) Solvents may be used alone or in combination of two or more.

(G) The amount of solvent is preferably adjusted appropriately from the viewpoint of the coatability of the photosensitive resin composition.

<(H) Optional Additives>
The photosensitive resin composition of the present invention may further contain an optional additive (H) in combination with the above-mentioned components (A) to (G) as long as the effects of the present invention are not significantly impaired. The optional additive (H) does not include those that fall under the above-mentioned components (A) to (G). The optional additive (H) may be used alone or in combination of two or more types.

(H) Examples of optional additives include photosensitizers, ultraviolet absorbers, silane coupling agents, plasticizers, flame retardants, antistatic agents, antiaging agents, antibacterial agents, defoamers, leveling agents, thickeners, adhesion agents, thixotropy agents, release agents, surface treatment agents, dispersants, surface modifiers, stabilizers, etc.

The photosensitive resin composition can be produced as a resin varnish by mixing the above essential components (A) to (D) and the above optional components (E) to (H), and kneading or stirring the mixture as necessary using a kneading device such as a triple roll mill, ball mill, bead mill, or sand mill, or a stirring device such as a super mixer, planetary mixer, or high-speed rotary mixer.

<Properties and Applications of Photosensitive Resin Composition>
The above-mentioned photosensitive resin composition can be used to form a core layer of an optical waveguide. The core layer formed usually contains a cured product of the above-mentioned photosensitive resin composition. The photosensitive resin composition can usually be cured by light, and preferably by light and heat. In general, among the components contained in the photosensitive resin composition, the (G) solvent is a volatile component and can be volatilized by heat during curing, but the other non-volatile components do not volatilize by heat during curing. Therefore, the cured product of the photosensitive resin composition can contain the non-volatile components of the photosensitive resin composition or their reaction products. The core layer preferably contains only the cured product of the photosensitive resin composition.

The photosensitive resin composition contains a combination of components (A) to (D), and therefore exhibits the characteristic of excellent core forming properties. Specifically, when the photosensitive resin composition is exposed to light and developed to form a line layer corresponding to the core layer, a line layer with a small minimum fine forming width can be formed. For example, the photosensitive resin composition is exposed to light and developed to form line layers with L/S (line/space) of 10 μm/10 μm, 5 μm/5 μm, and 3 μm/3 μm. In this case, the aspect ratio of the line layer can be preferably 0.6 or more, more preferably 0.8 or more, in each line layer. Here, in L/S, L (line) represents the width of the line layer, and S (space) represents the interval between the lines. The aspect ratio of the line layer represents the ratio expressed by the "layer thickness/line width" of the line layer. According to the photosensitive resin composition having such excellent core forming properties, a core layer with a small width and interval can be formed, and the fineness of the optical waveguide can be achieved. The minimum fine forming width can be measured according to the method described in the examples below.

Since the photosensitive resin composition contains a combination of components (A) to (D), it usually exhibits the property that even if the arithmetic mean roughness (Ra) of the surface of the cured photosensitive resin composition after the roughening treatment is low, the plating adhesion is excellent. Therefore, even if the surface unevenness provided on the core layer is small, a cured product with excellent plating adhesion is obtained. The arithmetic mean roughness (Ra) of the surface of the cured photosensitive resin composition after the roughening treatment is preferably 500 nm or less, more preferably less than 400 nm, even more preferably 200 nm or less, more preferably less than 200 nm. There is no particular limit to the lower limit, and it can be, for example, 1 nm or more, 2 nm or more, etc. The arithmetic mean roughness (Ra) can be measured by the method described in the examples below.

The photosensitive resin composition contains a combination of components (A) to (D), and therefore exhibits the characteristic of excellent peel strength between the photosensitive resin composition and the plated conductor layer. Specifically, after the photosensitive resin composition is cured, the cured photosensitive resin composition is subjected to a roughening treatment. The roughened surface is subjected to a copper plating treatment, and a conductor layer is formed on the cured photosensitive resin composition to obtain a sample. The peel strength is measured using this sample. At this time, the peel strength is preferably 0.2 kgf/cm or more, more preferably 0.3 kgf/cm or more. There is no particular upper limit, but it may be 10 kgf/cm or less. The peel strength can be measured according to the method described in the examples below.

The photosensitive resin composition exhibits the characteristic of being able to reduce optical transmission loss because it contains a combination of components (A) to (D). Specifically, a test substrate having a cladding layer and a core layer formed using the photosensitive resin composition is prepared. The optical transmission loss is measured using this test substrate. At this time, the optical transmission loss is preferably less than 2 dB/cm, more preferably less than 1 dB/cm. There is no particular lower limit, but it may be 0 dB/cm or more, 0.1 dB/cm or more, etc. The optical transmission loss can be measured according to the method described in the examples below.

Since the photosensitive resin composition contains a combination of components (A) to (D), it usually exhibits the characteristic of obtaining a cured product with excellent absorbance at 1310 nm. Specifically, the photosensitive resin composition is dissolved in a solvent to prepare a photosensitive resin composition solution. The absorbance at 1310 nm of this photosensitive resin composition solution is measured using an ultraviolet-visible-near infrared spectrophotometer. At this time, the absorbance is preferably less than 0.0100, more preferably less than 0.0050, and even more preferably less than 0.0025. There is no particular lower limit, but it may be 0.0001 or more. The absorbance can be measured according to the method described in the examples below.

In the photosensitive resin composition of the present invention, the non-exposed areas that are not irradiated with light can usually be removed by a developer. In particular, the photosensitive resin composition of the present invention can be effectively removed by a sodium carbonate solution as an alkaline developer. Therefore, the photosensitive resin composition of the present invention can be suitably used for sodium carbonate development.

In addition, the photosensitive resin composition of the present invention has excellent core forming properties and can reduce optical transmission loss, so it can be suitably used as a photosensitive resin composition for forming a core layer of an optical waveguide. Therefore, the photosensitive resin composition of the present invention can be suitably used for manufacturing a core layer of an optical waveguide (photosensitive resin composition for forming a core layer of an optical waveguide) and for forming an optical waveguide capable of transmitting light with a wavelength of 1300 nm to 1320 nm (photosensitive resin composition for forming an optical waveguide capable of transmitting light with a wavelength of 1300 nm to 1320 nm). The photosensitive resin composition of the present invention is preferably used for forming a single-mode optical waveguide, for example, for forming a single-mode optical waveguide for light with a wavelength of 1310 nm.

[Resin sheet]
The photosensitive resin composition of the present invention can be suitably used in the form of a resin sheet in which a photosensitive resin composition layer is formed on a support. That is, the resin sheet includes a support and a photosensitive resin composition layer formed of the photosensitive resin composition of the present invention provided on the support.

Examples of the support include polyethylene terephthalate film, polyethylene naphthalate film, polypropylene film, polyethylene film, polyvinyl alcohol film, triacetyl acetate film, etc., with polyethylene terephthalate film being particularly preferred.

Examples of commercially available supports include, but are not limited to, polyethylene terephthalate films such as those manufactured by Oji Paper under the product names "Alphan MA-410" and "E-200C," polypropylene films manufactured by Shin-Etsu Film Co., Ltd., and those manufactured by Teijin under the product name "PS-25" and other PS series. These supports are preferably coated with a release agent such as a silicone coating agent on the surface in order to facilitate removal of the photosensitive resin composition layer. The thickness of the support is preferably in the range of 5 μm to 50 μm, and more preferably in the range of 10 μm to 25 μm. By making the thickness 5 μm or more, it is possible to prevent the support from breaking when peeling off the support before development, and by making the thickness 50 μm or less, it is possible to improve the resolution when exposing from above the support. In addition, supports with low fisheyes are preferred. Here, fisheyes are foreign matter, undissolved matter, oxidized deterioration products, etc. of the material that are incorporated into the film when the material is thermally melted and then kneaded, extruded, biaxially stretched, cast, etc. to produce a film.

In order to reduce light scattering during exposure to actinic rays such as ultraviolet rays, the support is preferably one with excellent transparency. Specifically, the support is preferably one with a turbidity (haze standardized by JIS-K6714), which is an index of transparency, of 0.1 to 5. Furthermore, the photosensitive resin composition layer may be protected by a protective film.

By protecting the photosensitive resin composition layer side of the resin sheet with a protective film, it is possible to prevent the adhesion of dirt and the like to the surface of the photosensitive resin composition layer and scratches. As the protective film, a film made of the same material as the support can be used. The thickness of the protective film is not particularly limited, but is preferably in the range of 1 μm to 40 μm, more preferably in the range of 5 μm to 30 μm, and even more preferably in the range of 10 μm to 30 μm. By making the thickness 1 μm or more, the handleability of the protective film can be improved, and by making the thickness 40 μm or less, the cost tends to be improved. In addition, it is preferable that the adhesive strength between the photosensitive resin composition layer and the protective film is smaller than the adhesive strength between the photosensitive resin composition layer and the support.

The resin sheet can be manufactured, for example, by preparing a resin varnish by dissolving the photosensitive resin composition of the present invention in an organic solvent, applying the resin varnish to a support, and drying the organic solvent by heating or blowing hot air to form a photosensitive resin composition layer. Specifically, first, bubbles in the photosensitive resin composition are completely removed by a vacuum defoaming method or the like, and then the photosensitive resin composition is applied to a support, the solvent is removed by a hot air oven or a far-infrared oven, the resin is dried, and then, as necessary, a protective film is laminated on the obtained photosensitive resin composition layer to manufacture a resin sheet. Specific drying conditions vary depending on the curability of the photosensitive resin composition and the amount of organic solvent in the resin varnish, but in the case of a resin varnish containing 30% to 60% by mass of organic solvent, it can be dried at 80°C to 120°C for 3 to 13 minutes. The amount of remaining organic solvent in the photosensitive resin composition layer is preferably 5% by mass or less, more preferably 2% by mass or less, based on the total amount of the photosensitive resin composition layer, in order to prevent the diffusion of the organic solvent in the subsequent process. Those skilled in the art can easily determine suitable drying conditions through simple experimentation.

The thickness of the photosensitive resin composition layer is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, from the viewpoint of improving handleability and suppressing a decrease in sensitivity and resolution inside the photosensitive resin composition layer, and is preferably 15 μm or less, more preferably 13 μm or less, and even more preferably 10 μm or less.

Examples of methods for applying the photosensitive resin composition include gravure coating, microgravure coating, reverse coating, kiss reverse coating, die coating, slot die, lip coating, comma coating, blade coating, roll coating, knife coating, curtain coating, chamber gravure coating, slot orifice coating, spray coating, and dip coating.

The photosensitive resin composition may be applied in several separate applications, or in one application, or a combination of different methods may be used. Among these, the die coating method is preferred, as it provides excellent uniformity of application. In addition, to avoid contamination by foreign matter, it is preferable to carry out the application process in an environment where foreign matter is unlikely to be generated, such as a clean room.

[Photosensitive resin composition set]
The photosensitive resin composition of the present invention can be suitably used as a photosensitive resin composition for forming a core layer of an optical waveguide. Thus, the photosensitive resin composition set includes the photosensitive resin composition of the present invention and a photosensitive resin composition for cladding. The photosensitive resin composition set can be used for the manufacture of an optical waveguide having a core layer containing a cured product of the photosensitive resin composition of the present invention and a cladding layer containing a cured product of the photosensitive resin composition for cladding. The photosensitive resin composition for cladding can be a known photosensitive resin composition. Since both the photosensitive resin composition of the present invention and the photosensitive resin composition for cladding are photosensitive resin compositions, it is usually possible to efficiently manufacture a fine optical waveguide by a method including exposure and development.

[Optical Waveguide]
The above-mentioned photosensitive resin composition, resin sheet, and photosensitive resin composition set can be used to manufacture an optical waveguide. Hereinafter, an embodiment of the optical waveguide will be described with reference to the drawings.

1 is a perspective view showing a schematic diagram of an optical waveguide 10 according to one embodiment of the present invention. As shown in FIG. 1, the optical waveguide 10 includes a core layer 100 and a clad layer 200. The core layer 100 includes a cured product of the photosensitive resin composition of the present invention, and preferably includes only the cured product of the photosensitive resin composition of the present invention. The clad layer 200 includes a cured product of the clad resin composition, and preferably includes only the cured product of the clad resin composition. As the clad resin composition, a resin composition that can give a cured product having a lower refractive index than the cured product of the photosensitive resin composition of the present invention can be used. As the clad resin composition, a photocurable resin composition or a thermosetting resin composition can be used.

The core layer 100 is provided in the clad layer 200. Thus, the core layer 100 is covered by the clad layer 200. Usually, the entire peripheral surface of the core layer 100 is covered by the clad layer 200. The core layer 100 and the clad layer 200 are in direct contact with each other without any other layer therebetween, and therefore an interface 100I can be formed between the core layer 100 and the clad layer 200. Usually, the core layer 100 has a higher refractive index than the clad layer 200, and therefore light (not shown) can be transmitted through the core layer 100 from one end (the end on the incident side) 100A of the core layer 100 to the other end (the end on the exit side) 100B.

The wavelength of light that can be transmitted by the optical waveguide 10 can be selected from a variety of wavelengths. For example, the preferred wavelength range of the transmitted light can be 840 nm to 860 nm (e.g., 850 nm), 1300 nm to 1320 nm (e.g., 1310 nm), 1540 nm to 1560 nm (e.g., 1550 nm), etc. Among these, the preferred wavelength range of light transmitted through the optical transmission path 10 is 1300 nm to 1320 nm.

The optical waveguide 10 may be a single-mode optical waveguide or a multimode optical waveguide, but is preferably a single-mode optical waveguide. In particular, the optical waveguide 10 is preferably a single-mode optical waveguide for light in the preferred wavelength range described above. For example, the optical waveguide 10 is preferably a single-mode optical waveguide for light of 1310 nm.

It is desirable to set the width L of the core layer 100 appropriately within the range in which light transmission is possible. A specific range of the line width L of the core layer 100 is preferably 0.5 μm or more, more preferably 1 μm or more, particularly preferably 2 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less, particularly preferably 20 μm or less, and may be 10 μm or less or 5 μm or less. The width L of the core layer 100 corresponds to the line width (line) of the core layer 100 when viewed from the thickness direction.

It is desirable to set the spacing S of the core layers 100 appropriately within the range in which light transmission is possible. A specific range of the spacing S of the core layers 100 is preferably 50 μm or more, more preferably 70 μm or more, particularly preferably 100 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less, particularly preferably 300 μm or less. The spacing S of the core layers 100 corresponds to the spacing (space) of the core layers as viewed in the thickness direction.

It is desirable to set the thickness T of the core layer 100 appropriately within the range in which light transmission is possible. A specific range of the thickness T of the core layer 100 is preferably 0.5 μm or more, more preferably 1 μm or more, particularly preferably 2 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less, particularly preferably 20 μm or less, and may be 10 μm or less.

The thickness of the cladding layer 200 is usually greater than the thickness of the core layer 100. The specific thickness of the cladding layer 200 is preferably 5 μm or more, more preferably 7 μm or more, particularly preferably 10 μm or more, and is preferably 40 μm or less, more preferably 30 μm or less, particularly preferably 20 μm or less.

The optical waveguide 10 may include any element other than the core layer 100 and the clad layer 200 as necessary. For example, the optical waveguide 10 may include a conductor layer (not shown) made of plating or the like on the core layer, and a substrate 300. In an optical waveguide 10 including a substrate 300, the clad layer 200 is typically provided on the substrate 300, and the core layer 100 is provided within the clad layer 200.

The substrate 300 may be a hard substrate such as a glass substrate, a metal substrate, a ceramic substrate, a wafer, or a circuit substrate. The wafer may be a semiconductor wafer such as a silicon wafer, a gallium arsenide (GaAs) wafer, an indium phosphide (InP) wafer, a gallium phosphide (GaP) wafer, a gallium nitride (GaN) wafer, a gallium telluride (GaTe) wafer, a zinc selenium (ZnSe) wafer, or a silicon carbide (SiC) wafer, or a pseudo wafer. The pseudo wafer may be, for example, a plate-shaped member having a mold resin and electronic components embedded in the mold resin. The circuit board may be, for example, a glass epoxy board, a metal board, a polyester board, a polyimide board, a BT resin board, or a thermosetting polyphenylene ether board. The circuit board here refers to a board on which a patterned conductor layer (circuit) is formed on one or both sides of the above-mentioned board. Furthermore, the substrate 300 may be a film formed of a plastic material such as polyethylene terephthalate, polyimide, or polyester. Furthermore, a flexible circuit board may be used as the substrate 300.

The optical waveguide 10 may also include, as an optional element, a protective layer (not shown) that protects the core layer 100 and the cladding layer 200. The protective layer may be provided, for example, so as to cover the surface of the cladding layer 200 opposite the substrate 300.

As described above, the optical waveguide 10 can have a small transmission loss. In addition, the core layer 100 of the optical waveguide 10 has excellent core forming properties, so that the occurrence of surface irregularities can be suppressed and the core layer can be finely wired, and it can be formed with a small line width L as described above.

The optical waveguide 10 can be manufactured using the photosensitive resin composition of the present invention. For example, the optical waveguide 10 is
A step (I) of forming a first composition layer containing a cladding resin composition;
A step (II) of curing the first composition layer;
A step (III) of forming a second composition layer containing the photosensitive resin composition of the present invention on the first composition layer;
A step (IV) of subjecting the second composition layer to an exposure treatment;
A step (V) of subjecting the second composition layer to a development treatment;
A step (VI) of curing the second composition layer;
A step (VIII) of forming a third composition layer containing a cladding resin composition on the second composition layer;
A step (IX) of curing the third composition layer;
In addition, if necessary, a step (VII) of forming a conductor layer on the core layer may be included after the step (VI) and before the step (VIII).

Figure 2 is a schematic cross-sectional view for explaining step (I) of the method for producing an optical waveguide according to one embodiment of the present invention. As shown in Figure 2, the method for producing an optical waveguide according to one embodiment of the present invention includes step (I) of forming a first composition layer 210 containing a photosensitive resin composition for cladding. In this embodiment, an example of forming the first composition layer 210 on a substrate 300 will be shown and explained.

There is no particular limitation on the method for forming the first composition layer 210. For example, the first composition layer 210 may be formed by applying the clad resin composition onto the substrate 300. From the viewpoint of smooth application, a varnish-like clad resin composition containing a solvent may be prepared, and the varnish-like clad resin composition may be applied.

Examples of coating methods include gravure coating, microgravure coating, reverse coating, kiss reverse coating, die coating, slot die, lip coating, comma coating, blade coating, roll coating, knife coating, curtain coating, chamber gravure coating, slot orifice, spin coating, slit coating, spray coating, dip coating, hot melt coating, bar coating, applicator, air knife coating, curtain flow coating, offset printing, brush coating, and screen printing.

The cladding resin composition may be applied in one application or in multiple applications. Different application methods may also be combined. To avoid contamination, it is preferable to apply the composition in an environment where foreign matter is unlikely to be generated, such as a clean room.

After application of the cladding resin composition, the first composition layer 210 may be dried as necessary. Drying can be performed using a drying device such as a hot air oven or a far infrared oven. It is preferable to set the drying conditions appropriately according to the composition of the cladding resin composition. To give a specific example, the drying temperature is preferably 50°C or higher, more preferably 70°C or higher, and particularly preferably 80°C or higher, and preferably 150°C or lower, more preferably 130°C or lower, and particularly preferably 120°C or lower. The drying time is preferably 30 seconds or higher, more preferably 60 seconds or higher, and particularly preferably 120 seconds or higher, and preferably 60 minutes or less, more preferably 20 minutes or less, and particularly preferably 5 minutes or less.

The first composition layer 210 may be formed, for example, using a clad resin sheet including a support and a clad photosensitive resin composition layer made of a clad photosensitive resin composition. As a specific example, the clad photosensitive resin composition layer of the clad resin sheet is laminated to the substrate 300 to form the first composition layer 210 on the substrate 300. The lamination is usually performed by pressing the clad photosensitive resin composition layer of the resin sheet to the substrate 300 while heating it. This lamination is preferably performed under reduced pressure by a vacuum lamination method. In addition, a preheat treatment may be performed before lamination to heat the resin sheet and the substrate, if necessary.

The lamination can be performed under conditions of, for example, a pressure bonding temperature (lamination temperature) of 70°C to 140°C, a pressure bonding pressure of 1 kgf/ ^cm2 to 11 kgf/ ^cm2 (9.8 x ¹⁰⁴ N/ ^m2 to 107.9 x ¹⁰⁴ N/ ^m2 ), and a pressure bonding time of 5 to 300 seconds. The lamination is preferably performed under reduced pressure with an air pressure of 20 mmHg (26.7 hPa) or less. The lamination may be performed in a batch manner or continuously using a roll.

The vacuum lamination method can be carried out using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include the vacuum applicator manufactured by Nikko Materials Co., Ltd., the vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., the roll-type dry coater manufactured by Hitachi Industries Co., Ltd., and the vacuum laminator manufactured by Hitachi AIC Co., Ltd.

When the first composition layer 210 is formed using a clad resin sheet having a support, the support is usually peeled off at an appropriate time prior to step (III).

The first composition layer 210 formed on the substrate 300 in step (I) typically contains a cladding resin composition, and preferably contains only a cladding resin composition.

The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (I), step (II) of curing the first composition layer 210. This step (II) may, for example, involve heat treating the first composition layer 210. The conditions for the heat treatment may be selected according to the type and amount of the resin component in the cladding oil composition, and may be preferably in the range of 150°C to 250°C for 20 minutes to 180 minutes, and more preferably in the range of 160°C to 230°C for 30 minutes to 120 minutes. The heat treatment is preferably carried out in an inert atmosphere such as a nitrogen atmosphere.

The first composition layer 210 may be cured by exposure treatment. In one example, the specific range of the exposure dose is preferably 10 mJ/cm ² or more, more preferably 50 mJ/cm ² or more, particularly preferably 200 mJ/cm ² or more, and preferably 10,000 mJ/cm ² or less, more preferably 8,000 mJ/cm ² or less, even more preferably 4,000 mJ/cm ² or less, particularly preferably 1,000 mJ/cm ² or less. The first composition layer 210 may be cured by combining the exposure treatment and the heat treatment.

Figure 3 is a schematic cross-sectional view for explaining step (II) of the method for producing an optical waveguide according to one embodiment of the present invention. By curing the first composition layer 210 in step (II), a cured first composition layer 220 is obtained on the substrate 300, as shown in Figure 3. This cured first composition layer 220 forms a part of the cladding layer 200, and may be referred to as the "lower cladding layer" 220 below.

Figure 4 is a schematic cross-sectional view for explaining step (III) of the method for producing an optical waveguide according to one embodiment of the present invention. The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (II), step (III) of forming a second composition layer 110 containing the photosensitive resin composition of the present invention on the lower clad layer 220 as the cured first composition layer, as shown in Figure 4.

There is no particular limitation on the method of forming the second composition layer 110. For example, the second composition layer 110 may be formed by applying the photosensitive resin composition of the present invention onto the lower clad layer 220. From the viewpoint of smooth application, a varnish-like photosensitive resin composition containing a solvent may be prepared and the varnish-like photosensitive resin composition may be applied. The application of the photosensitive resin composition of the present invention may be performed in the same manner as the application of the clad resin composition. In addition, after application of the photosensitive resin composition of the present invention, the second composition layer 110 may be dried as necessary. The second composition layer 110 may be dried using the same method and conditions as those for drying the first composition layer 210.

The second composition layer 110 may be formed, for example, by using a resin sheet. As a specific example, the second composition layer 110 can be formed on the lower clad layer 220 by laminating a photosensitive resin composition layer of a resin sheet onto the lower clad layer 220. The lamination of the resin sheet can be performed in the same manner as the lamination of the clad resin sheet. In addition, the support of the resin sheet is peeled off at an appropriate time before step (V).

The second composition layer 110 formed on the lower cladding layer 220 in step (III) typically contains the photosensitive resin composition of the present invention, and preferably contains only the photosensitive resin composition of the present invention.

Figure 5 is a schematic cross-sectional view for explaining step (IV) of the method for producing an optical waveguide according to one embodiment of the present invention. As shown in Figure 5, the method for producing an optical waveguide according to one embodiment of the present invention includes step (IV) of subjecting the second composition layer 110 to an exposure treatment after step (III).

In step (V), a latent image is formed in the second composition layer 110 by exposure treatment. Specifically, in the exposure treatment, light P is selectively irradiated to specific parts of the second composition layer 110. Thus, when the exposure treatment is performed, the second composition layer 110 is provided with an exposed part 111 that is irradiated with light and a non-exposed part 112 that is not irradiated with light. Typically, the core resin composition functions as a negative photosensitive resin composition, so that the exposed part 111 forms a latent image corresponding to the core layer.

From the viewpoint of selective exposure, the exposure process in step (V) is usually performed using a mask 400. Specifically, in this exposure process, light P is irradiated onto the second composition layer 110 through a mask 400 having a light-transmitting portion 410 and a light-shielding portion 420. The light P passes through the light-transmitting portion 410 and enters the exposed portion 111, but cannot pass through the light-shielding portion 420 and therefore cannot enter the non-exposed portion 112. Thus, the exposed portion 111 and the non-exposed portion 112 corresponding to the light-transmitting portion 410 and the light-shielding portion 420 can be provided in the second composition layer 110. The mask 400 may be brought into close contact with the second composition layer 110 as shown in FIG. 5 (contact exposure method), or exposure may be performed using parallel light without being in close contact (non-contact exposure method).

In general, the light-transmitting portion 410 of the mask 400 is formed to have a planar shape corresponding to the core layer of the optical waveguide. Therefore, the light-shielding portion 420 of the mask 400 is formed to have a planar shape corresponding to the portion of the optical waveguide where there is no core layer. Unless otherwise specified, the "planar shape" refers to the shape seen from the thickness direction. The light-transmitting portion 410 formed in a planar shape corresponding to the core layer may be referred to as the "mask pattern" below.

As the light P used in the exposure treatment in step (V), it is preferable to use an appropriate actinic ray according to the composition of the photosensitive resin composition of the present invention. The wavelength of the actinic ray is usually 190 nm to 1000 nm, preferably 240 nm to 550 nm, but light of other wavelengths may be used. Specific examples of the actinic light source include ultraviolet light, visible light, electron beams, X-rays, etc., and ultraviolet light is particularly preferred. The exposure dose of the light P is preferably set so that a desired core layer can be formed after curing in step (VII). In one example, the specific range of the exposure dose in step (V) is preferably 10 mJ/cm ² or more, more preferably 50 mJ/cm ² or more, particularly preferably 200 mJ/cm ² or more, and preferably 10,000 mJ/cm ² or less, more preferably 8,000 mJ/cm ² or less, even more preferably 4,000 mJ/cm ² or less, and particularly preferably 1,000 mJ/cm ² or less.

When the second composition layer 110 is formed using the resin sheet of the present invention, a support (not shown) may be present on the second composition layer 110 in step (IV). When a support is present on the second composition layer 110, exposure may be performed through the support, or exposure may be performed after peeling off the support.

The photosensitive resin composition of the present invention functions as a negative photosensitive resin composition, so that the exposed area 111 has reduced solubility in the developer. On the other hand, the non-exposed area 112 has high solubility in the developer. The difference in solubility between the exposed area 111 and the non-exposed area 112 is utilized to carry out the development process in the subsequent step (VI).

The method for producing an optical waveguide according to one embodiment of the present invention may include a step (IX) of heating the second composition layer 110 after step (IV) and before step (V) in order to harden the second composition layer 110. Step (IX) can quickly reduce the solubility of the exposed portion 111 in the developer. The heating in step (IX) may be performed using a hot plate or an oven. The heating temperature may be, for example, 40° C. or higher and 110° C. or lower. The heating time may be, for example, 30 seconds or higher and 60 minutes or lower.

Figure 6 is a schematic cross-sectional view for explaining step (V) of the method for producing an optical waveguide according to one embodiment of the present invention. The method for producing an optical waveguide according to one embodiment of the present invention includes step (V) of subjecting the second composition layer 110 to a development treatment after step (IV). The development treatment allows the latent image formed in step (IV) to be developed. Since the photosensitive resin composition of the present invention functions as a negative photosensitive resin composition, as shown in Figure 6, the exposed portion 111 is not removed by the development treatment, while the non-exposed portion 112 (see Figure 5) is removed. The exposed portion 111 of the second composition layer 110 remaining after development may have the same planar shape as the mask pattern of the light-transmitting portion 410 (see Figure 5) of the mask 400 used in step (IV).

The development method is usually a wet development method in which the second composition layer 110 is brought into contact with a developer. An alkaline aqueous solution is usually used as the developer.

Examples of alkaline aqueous solutions as developing solutions include aqueous solutions of alkali metal compounds. Examples of alkali metal compounds include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkali metal carbonates or bicarbonates such as sodium carbonate and sodium bicarbonate; alkali metal phosphates such as sodium phosphate and potassium phosphate; and alkali metal pyrophosphates such as sodium pyrophosphate and potassium pyrophosphate. Examples of alkaline aqueous solutions include aqueous solutions of organic bases that do not contain metal ions, such as tetraalkylammonium hydroxide. One type of alkaline aqueous solution may be used alone, or two or more types may be used in combination. Among these, from the viewpoint of obtaining the effects of the present invention significantly, an alkali metal carbonate or bicarbonate is preferred, and sodium carbonate is more preferred.

The developer may contain additives such as surfactants and defoamers to improve the developing action, if necessary.

The development time is preferably 10 seconds to 5 minutes. The temperature of the developer during development is not particularly specified, but is preferably 20°C or higher, and preferably 50°C or lower, and more preferably 40°C or lower.

Examples of development methods include the paddle method, spray method, immersion method, brushing method, slapping method, and ultrasonic method. Among these, the spray method is suitable for improving resolution. When using the spray method, the spray pressure is preferably 0.05 MPa to 0.3 MPa.

After development using the developer, the second composition layer 110 may be further rinsed. Rinsing is preferably performed with a solvent different from the developer. For example, rinsing may be performed with the same type of solvent contained in the core resin composition or with water. The rinsing time is preferably 5 seconds to 1 minute.

After development using a developer, a desmear process may be performed to remove unexposed areas that cannot be removed by development. The desmear process may be performed according to various methods known to those skilled in the art and used in the manufacture of printed wiring boards.

The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (V), step (VI) of curing the second composition layer 110. This step (VI) usually includes heat treating the second composition layer 110. The conditions for the heat treatment may be selected according to the type and amount of the resin component in the photosensitive resin composition of the present invention. For example, the conditions for the heat treatment in step (VI) may be the same as the conditions for the heat treatment of the first composition layer 210 in step (II).

Figure 7 is a schematic cross-sectional view for explaining step (VI) of the method for producing an optical waveguide according to one embodiment of the present invention. By curing the second composition layer 110 in step (VI), a core layer 100 is obtained as a cured second composition layer on the lower cladding layer 220, as shown in Figure 7.

8 is a schematic cross-sectional view for explaining step (VII) of the method for producing an optical waveguide according to one embodiment of the present invention. The method for producing an optical waveguide according to one embodiment of the present invention may include a step (VII) of forming a conductor layer on the core layer after the completion of step (VI) and before step (VIII). The conductor layer 500 formed on the core layer 100 is preferably formed by plating. In addition, before forming the conductor layer 500 by plating, the surface of the core layer 100 may be roughened. Since the core layer 100 contains the photosensitive resin composition of the present invention, it has high resistance to the chemical solution used in the roughening treatment, so that the arithmetic mean roughness (Ra) after the roughening treatment is small. This makes it possible to reduce the transmission loss. Furthermore, since the core layer 100 contains the photosensitive resin composition of the present invention, even if the arithmetic mean roughness (Ra) after the roughening treatment is small, it is also possible to improve the peel strength between the core layer 100 and the conductor layer 500.

The procedure and conditions for the roughening treatment are not particularly limited. For example, the insulating layer can be roughened by performing a swelling treatment using a swelling liquid, a roughening treatment using an oxidizing agent, and a neutralization treatment using a neutralizing liquid in this order.

Examples of the swelling liquid used in the roughening treatment include an alkaline solution, a surfactant solution, and the like, and an alkaline solution is preferred. As the alkaline solution, a sodium hydroxide solution and a potassium hydroxide solution are more preferred. Examples of commercially available swelling liquids include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan. The swelling treatment using the swelling liquid is not particularly limited, but can be performed by, for example, immersing the insulating layer in a swelling liquid at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of suppressing the swelling of the resin of the insulating layer to an appropriate level, it is preferable to immerse the insulating layer in a swelling liquid at 40°C to 80°C for 5 to 15 minutes.

The oxidizing agent used in the roughening treatment may be, for example, an alkaline permanganate solution in which potassium permanganate or sodium permanganate is dissolved in an aqueous solution of sodium hydroxide. The roughening treatment using an oxidizing agent such as an alkaline permanganate solution is preferably carried out by immersing the insulating layer in an oxidizing agent solution heated to 60°C to 100°C for 10 to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% by mass to 10% by mass. Commercially available oxidizing agents include, for example, alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securigans P" manufactured by Atotech Japan.

The neutralizing solution used in the roughening treatment is preferably an acidic aqueous solution, and a commercially available product is, for example, "Reduction Solution Securigant P" manufactured by Atotech Japan. Treatment with a neutralizing solution can be carried out by immersing the surface that has been roughened with an oxidizing agent in a neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, etc., it is preferable to immerse the object that has been roughened with an oxidizing agent in a neutralizing solution at 40°C to 70°C for 5 to 20 minutes.

The arithmetic mean roughness Ra of the core layer surface after the roughening treatment is as described above, and is preferably 500 nm or less, more preferably less than 400 nm, even more preferably 200 nm or less, and even more preferably less than 200 nm. There is no particular limit to the lower limit, and it can be, for example, 1 nm or more, 2 nm or more, etc.

After completion of the roughening treatment, the conductor layer 500 is formed on the core layer 100 that has been subjected to the roughening treatment. Specifically, the surface of the core layer 100 can be plated by a method such as a semi-additive method or a full-additive method to form the conductor layer 500 having the desired wiring pattern. From the viewpoint of ease of manufacture, it is preferable to form the conductor layer by the semi-additive method. Below, an example of forming the conductor layer by the semi-additive method is shown.

A plating seed layer is formed on the surface of the core layer 100 by electroless plating. Next, a mask pattern is formed on the formed plating seed layer to expose a portion of the plating seed layer corresponding to the desired wiring pattern. A metal layer is formed on the exposed plating seed layer by electrolytic plating, and then the mask pattern is removed. Thereafter, unnecessary plating seed layer is removed by etching or the like, and a conductor layer 500 having the desired wiring pattern can be formed.

9 is a schematic cross-sectional view for explaining step (VIII) of the method for producing an optical waveguide according to one embodiment of the present invention. As shown in FIG. 9, the method for producing an optical waveguide according to one embodiment of the present invention includes a step (VIII) of forming a third composition layer 230 containing a cladding resin composition on the core layer 100 and the conductor layer 500 after step (VII). The third composition layer 230 is usually formed so as to cover the entire surface of the core layer 100 and the conductor layer 500 that is not in contact with the lower cladding layer 220. Thus, the third composition layer 230 is formed so as to cover the core layer 100 and the conductor layer 500, and is also formed on the lower cladding layer 220.

There is no particular limitation on the method of forming the third composition layer 230. For example, the third composition layer 230 may be formed by applying a clad resin composition onto the core layer 100 and the conductor layer 500 (and, if necessary, onto the lower clad layer 220). The application of the clad resin composition for forming the third composition layer 230 may be performed in the same manner as the application of the clad resin composition for forming the first composition layer 210. Furthermore, after application of the clad resin composition, the third composition layer 230 may be dried, if necessary. The third composition layer 230 may be dried using the same method and conditions as those for drying the first composition layer 210.

The third composition layer 230 may be formed, for example, using a clad resin sheet. As a specific example, the photosensitive resin composition layer of the clad resin sheet is laminated to the core layer 100 and the conductor layer 500 (and, if necessary, the lower clad layer 220) to form the third composition layer 230 on the core layer 100. The lamination of the clad resin sheet to form the third composition layer 230 may be performed in the same manner as the lamination of the clad resin sheet to form the first composition layer 210. When the third composition layer 230 is formed using a clad resin sheet having a support, the support may be peeled off in any step.

The third composition layer 230 formed on the core layer 100 and the conductor layer 500 in step (VIII) typically contains a cladding resin composition, and preferably contains only a cladding resin composition.

The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (VIII), step (IX) of curing the third composition layer 230. The effect of the third resin composition layer 230 in step (IX) can usually be achieved in the same way as the curing of the first composition layer 210.

Figure 10 is a schematic cross-sectional view for explaining step (IX) of the method for producing an optical waveguide according to one embodiment of the present invention. By curing the third composition layer 230 in step (IX), a cured third composition layer 240 is obtained on the core layer 100 as shown in Figure 10. This cured third composition layer 240 forms a part of the cladding layer 200, and may be referred to as the "upper cladding layer" 240 below. The cladding layer 200 is formed from this upper cladding layer 240 and the lower cladding layer 220. Therefore, an optical waveguide 10 can be obtained that includes the cladding layer 200 including the lower cladding layer 220 and the upper cladding layer 240, and the core layer 100 provided within this cladding layer 200.

The method for manufacturing the optical waveguide 10 may include any further steps in combination with the steps described above.

The method for manufacturing the optical waveguide 10 may include, for example, a step of forming a protective layer (not shown). The method for manufacturing the optical waveguide 10 may also include, for example, a step of dicing the manufactured optical waveguide 10.

The method for manufacturing the optical waveguide 10 may involve repeating the above-mentioned steps. For example, steps (I) to (IX) may be repeated to manufacture an optical waveguide having a multilayer structure on the substrate 300, in which core layers and clad layers are alternately arranged in the thickness direction.

[Optical/electrical hybrid board]
The optical/electrical hybrid board according to an embodiment of the present invention includes the optical waveguide described above. Typically, the optical/electrical hybrid board includes an optical waveguide and an electric circuit board. The electric circuit board may include electronic components and wiring connected to the electronic components. Examples of the electronic components include passive components such as capacitors, inductors, and resistors; active components such as semiconductor chips; and the like. The optical waveguide and the wiring of the electric circuit board may be connected via a photoelectric conversion element. The photoelectric conversion element may include a combination of a light-emitting element (e.g., a surface-emitting light-emitting diode) capable of converting electricity into light, and a light-receiving element (e.g., a photodiode) capable of converting light into electricity. Furthermore, the optical/electrical hybrid board may include an optical element such as a mirror for adjusting the optical path.

A preferred example of an opto-electrical hybrid board is one that includes a chip with an optical integrated circuit formed on a silicon wafer. This chip is expected to be put to practical use in the near future using silicon photonics, and is expected to be mounted, for example, in a semiconductor package. An opto-electrical hybrid board that includes this chip includes, for example, an electric circuit board, a chip mounted on the electric circuit board, and an optical waveguide. The optical waveguide can be used to connect the wiring of the electric circuit board to the chip, or to connect multiple chips together.

In chips manufactured using silicon photonics, light with wavelengths of 1310 nm and 1550 nm is generally used, with 1310 nm being the most common (Sho Yoshida, Daisuke Suganuma, Takaaki Ishigure, "Fabrication of Single-Mode Polymer Waveguides Using the Mosquito Method and Reducing Loss," 28th Japan Institute of Electronics Packaging Spring Conference, 2014). Therefore, it is preferable that the optical waveguide is capable of transmitting light with wavelengths of 1310 nm and 1550 nm or close thereto, and for example, it is preferable that it is capable of transmitting light with wavelengths of 1300 nm to 1320 nm. The optical waveguide according to the above-mentioned embodiment is capable of transmitting light with these wavelengths.

In general, the single mode can achieve faster transmission than the multimode. Therefore, from the viewpoint of high-speed transmission, a single mode optical waveguide is preferable as an optical waveguide to be applied to an optical-electrical hybrid circuit. In a single mode optical waveguide, it is preferable that the width of the core layer is small. For example, it is preferable to form a core layer with a width of 10 μm or less, or 5 μm or less. In addition, an optical waveguide having such a small core layer is preferable from the viewpoint of increasing the degree of freedom in package design when the optical waveguide is applied to a semiconductor package. According to the optical waveguide of the above-mentioned embodiment, it is possible to reduce the width of the core layer as described above.

On the other hand, when connecting multiple opto-electrical hybrid boards, the boards may be connected via optical fiber. For example, multiple opto-electrical hybrid boards may be placed on a rack and connected to each other via optical fiber. Multimode optical fibers are the mainstream for connecting boards in this way. Therefore, from the perspective of enabling connection to optical fiber, a multimode optical waveguide may be used as the optical waveguide provided in the opto-electrical hybrid board.

From the viewpoint of increasing versatility, it is desirable that the optical waveguide is applicable to both single mode and multimode. Furthermore, it is desirable to reduce the minimum width of the core layer of these optical waveguides to increase the degree of freedom in the line width of the core layer. According to the optical waveguide of the above-mentioned embodiment, by using the photosensitive resin composition of the present invention for the core, a fine core can be formed and the occurrence of surface irregularities of the core can be suppressed, so that the minimum width of the core layer can be reduced. Furthermore, according to the optical waveguide of the above-mentioned embodiment, both single mode and multimode optical waveguides can be obtained. Therefore, the optical waveguide of the above-mentioned embodiment can be applied in a wide range. And, since it can be applied in such a wide range and the transmission loss of light can be suppressed, the optical waveguide of the above-mentioned embodiment is suitable for application to an optical-electrical hybrid board.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following description, the terms "parts" and "%" used to indicate amounts refer to "parts by mass" and "% by mass", respectively, unless otherwise specified. Furthermore, the operations described below were carried out in the atmosphere at room temperature and normal pressure (23°C and 1 atm) unless otherwise specified.

Synthesis Example 1: Synthesis of resin containing carboxy group and ethylenic double bond
325 parts of an epoxy resin having a naphthol aralkyl skeleton with an epoxy equivalent of 325 g/eq. ("ESN-475V", manufactured by Nippon Steel Chemical & Material Co., Ltd.) was placed in a flask equipped with a gas inlet tube, a stirrer, a cooling tube and a thermometer, 340 parts of carbitol acetate was added, and the mixture was dissolved by heating, and 0.46 parts of hydroquinone and 1 part of triphenylphosphine were added. The mixture was heated to 95-105°C, and 72 parts of acrylic acid were gradually added dropwise and reacted for 16 hours. The reaction product was cooled to 80-90°C, and 80 parts of tetrahydrophthalic anhydride was added, reacted for 8 hours, and cooled. The amount of solvent was adjusted to obtain a resin solution (70% non-volatile content) with an acid value of 60 mgKOH/g of solid matter. The weight average molecular weight was 1000.

<Production Example 1: Production of Cladding Resin Composition>
A varnish-like resin composition was prepared by mixing 25 parts of the naphthol aralkyl skeleton-containing ester-type acid-modified epoxy acrylate resin (non-volatile content 70%) obtained in Synthesis Example 1, 12 parts of a naphthalene skeleton epoxy resin (DIC Corporation's "HP-4710", epoxy equivalent 170 g/eq.), 1.5 parts of a photopolymerization initiator (IGM Corporation's "Omnirad 379EG"), 13 parts of a reactive diluent (Nippon Kayaku Co., Ltd.'s "DPHA", dipentaerythritol hexaacrylate), and 30 parts of spherical silica surface-treated with an amino-based silane coupling agent (Admatechs Corporation's "180 nm SX-C1", specific surface area 20 m ² /g, average particle size 0.2 μm) with 10 parts of methyl ethyl ketone using a high-speed rotating mixer.

Example 1: Production of photosensitive resin composition
26 parts of the naphthol aralkyl skeleton-containing ester-type acid-modified epoxy acrylate resin (non-volatile content 70%) obtained in Synthesis Example 1, 12 parts of a naphthalene skeleton epoxy resin (DIC Corporation's "HP-4710", epoxy equivalent 170 g/eq.), 1.5 parts of a photopolymerization initiator (IGM Corporation's "Omnirad 379EG"), 0.5 parts of a non-developable polymer (Kyoeisha Chemical Co., Ltd.'s acrylic polymer "Polyflow WS-314", SP value: 11.5 (cal/cm ³ ) ^1/2 , molecular weight 20,000), 13 parts of a reactive diluent (Nippon Kayaku Co., Ltd.'s "DPHA", dipentaerythritol hexaacrylate), and 10 parts of methyl ethyl ketone were mixed and used to prepare a varnish-like resin composition using a high-speed rotating mixer.

<Examples 2 to 12 and Comparative Examples 1 and 2: Production of Photosensitive Resin Compositions>
A varnish-like photosensitive resin composition was prepared in the same manner as in Example 1, except that the components were mixed according to the composition shown in the following table. In the table, the amount of each component is indicated by parts by mass, and is the actual amount used.

・Ｉｒｇａｃｕｒｅ ＯＸＥ－０２：下記構造で表される化合物（ＢＡＳＦ社製、分子量は４１２．５、ｅｔｈａｎｏｎｅ， １－［９－ｅｔｈｙｌ－６－（２－ｍｅｔｈｙｌｂｅｎｚｏｙｌ）－９Ｈ－ｃａｒｂａｚｏｌ－３－ｙｌ］－， １－（ｏ－ａｃｅｔｙｌｏｘｉｍｅ））

・Ｏｍｎｉｒａｄ ８１９：下記構造で表される化合物（ＩＧＭ社製、分子量は４１８．５、Ｂｉｓ（２，４，６－ｔｒｉｍｅｔｈｙｌｂｅｎｚｏｙｌ）ｐｈｅｎｙｌｐｈｏｓｐｈｉｎｅ ｏｘｉｄｅ）

（Ｄ）成分
・ＷＳ－３１４：アクリルポリマー（共栄社化学社製「ポリフローＷＳ－３１４」、ＳＰ値：１１．５（ｃａｌ／ｃｍ^３）^１／２、分子量２万）
・Ｎｏ．９９Ｃ：アクリルポリマー（共栄社化学社製「ポリフローＮｏ．９９Ｃ」、ＳＰ値：９．７（ｃａｌ／ｃｍ^３）^１／２、分子量８０００）
（Ｅ）成分
・Ｙ５０ＳＺ－ＡＭ１：アミノ系シランカップリング剤で表面処理された球形シリカ（アドマテックス社製「Ｙ５０ＳＺ－ＡＭ１」、比表面積６０ｍ^２／ｇ、平均粒径０．０５μｍ、固形分率５０％
（Ｆ）成分
・ＤＰＨＡ：日本化薬社製、ジペンタエリスリトールヘキサアクリレート
（Ｇ）成分
・ＭＥＫ：メチルエチルケトン
（Ｈ）成分
・ＵＴ－１００１：アクリルポリマー（綜研化学社製「アクトフローＵＴ－１００１」、ＳＰ値：８．６（ｃａｌ／ｃｍ^３）^１／２、分子量３５００）
・ＡＣ－２３００Ｃ：ポリオレフィン（共栄社化学社製「フローレンＡＣ－２３００Ｃ」、ＳＰ値：８．４（ｃａｌ／ｃｍ^３）^１／２、分子量：３５００） The abbreviations in the table are as follows:
Component (A) HP-4710: naphthalene-type tetrafunctional epoxy resin (DIC Corporation's "HP-4710", epoxy equivalent 170 g/eq.)
ESN-475V: naphthol aralkyl skeleton epoxy resin ("ESN-475V" manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent: approximately 330 g/eq.)
NC3000H: biphenyl type epoxy resin ("NC3000H" manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 290 g/eq.)
850: Bisphenol A type epoxy resin (DIC Corporation "EPICLON 850", epoxy equivalent 183 to 193 g/eq.)
Component (B) Synthesis Example 1: Resin containing a carboxy group and an ethylenic double bond, synthesized in Synthesis Example 1, non-volatile content 70%
CCR-1171H: ("CCR-1171H" manufactured by Nippon Kayaku Co., Ltd., containing cresol novolac skeleton, acid value 99 mg KOH/g, non-volatile content 60%, solvent PGMEA, molecular weight 7500, SP value 9.5 (cal/cm ³ ) ^1/2 )
ZCR-1761H: ("ZCR-1761H" manufactured by Nippon Kayaku Co., Ltd., containing biphenyl skeleton, acid value 60 mg KOH/g, non-volatile content 70%, solvent PGMEA, molecular weight 3000, SP value 9.9 (cal/cm ³ ) ^1/2 )
Component (C) Omnirad 379EG: a compound represented by the following structure (manufactured by IGM, molecular weight 380.5, 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, CAS 119344-86-4)

Irgacure OXE-02: a compound represented by the following structure (manufactured by BASF, molecular weight 412.5, ethane, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(o-acetyloxime))

Omnirad 819: A compound represented by the following structure (manufactured by IGM, molecular weight 418.5, Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide)

Component (D) WS-314: acrylic polymer ("Polyflow WS-314" manufactured by Kyoeisha Chemical Co., Ltd., SP value: 11.5 (cal/cm ³ ) ^1/2 , molecular weight: 20,000)
No. 99C: Acrylic polymer ("Polyflow No. 99C" manufactured by Kyoeisha Chemical Co., Ltd., SP value: 9.7 (cal/cm ³ ) ^1/2 , molecular weight 8000)
Component (E) Y50SZ-AM1: Spherical silica surface-treated with an amino-based silane coupling agent ("Y50SZ-AM1" manufactured by Admatechs Co., Ltd., specific surface area 60 m ² /g, average particle size 0.05 μm, solid content 50%)
Component (F): DPHA: dipentaerythritol hexaacrylate manufactured by Nippon Kayaku Co., Ltd. Component (G): MEK: methyl ethyl ketone Component (H): UT-1001: acrylic polymer (Actflow UT-1001 manufactured by Soken Chemical & Engineering Co., Ltd., SP value: 8.6 (cal/cm ³ ) ^1/2 , molecular weight 3500)
AC-2300C: Polyolefin ("Florene AC-2300C" manufactured by Kyoeisha Chemical Co., Ltd., SP value: 8.4 (cal/cm ³ ) ^1/2 , molecular weight: 3500)

<Production of Resin Sheet>
Using the photosensitive resin compositions produced in the above-mentioned Examples 1 to 12 and Comparative Examples 1 to 3, a plurality of resin sheets having photosensitive resin composition layers with different thicknesses were produced by the following method.

A polyethylene terephthalate film (Toray Industries, Inc., "Lumirror T6AM", thickness 38 μm, softening point 130°C) was prepared as a support. The photosensitive resin compositions produced in Production Example 1, Examples 1 to 12, and Comparative Examples 1 to 3 were uniformly applied to the support using a die coater so that the thickness of the photosensitive resin composition layer after drying was 5 μm or 10 μm, and the support was dried at 80°C to 110°C (maximum temperature 110°C) for 6 minutes to form a photosensitive resin composition layer. Next, a cover film (biaxially oriented polypropylene film, Oji F-Tex Co., Ltd., "MA-411") was placed on the surface of the photosensitive resin composition layer and laminated at 80°C to produce a resin sheet with a three-layer structure of support/photosensitive resin composition layer/cover film.

A polyethylene terephthalate film (Toray Industries, Inc., "Lumirror T6AM," thickness 38 μm, softening point 130°C) was prepared as a support. The resin composition produced in Production Example 1 was uniformly applied with a die coater so that the thickness of the resin composition layer after drying would be 5 μm, 10 μm, or 20 μm, and dried at 80°C to 110°C (maximum temperature 110°C) for 6 minutes to form a photosensitive resin composition layer. Next, a cover film (biaxially oriented polypropylene film, Oji F-Tex Co., Ltd., "MA-411") was placed on the surface of the photosensitive resin composition layer and laminated at 80°C to produce a resin sheet with a three-layer structure of support/photosensitive resin composition layer/cover film.

[Evaluation of core formation]
(Evaluation of minimum fine line width)
A copper layer of a glass epoxy substrate (copper-clad laminate) having a thickness of 18 μm was roughened with a surface treatment agent (CZ8100, manufactured by MEC Co., Ltd.) containing an organic acid to prepare a substrate. A resin sheet having a thickness of 5 μm, manufactured using the resin composition prepared in Manufacturing Example 1, was laminated on the previous substrate at 80° C., and the support was peeled off to form a photosensitive resin composition layer. Thereafter, ultraviolet light exposure was performed using a projection exposure device (manufactured by Ushio Inc., “UFX-2240”) with an exposure energy that resulted in 8 gloss remaining steps of a 41-step tablet. A quartz glass mask without an exposure pattern was used. After standing at room temperature for 30 minutes, the support was peeled off. A 1% by mass aqueous solution of sodium carbonate at 30° C. was used as a developer for 1 minute for spray development at a spray pressure of 0.2 MPa on the entire surface of the photosensitive resin composition layer. After spray development, the coating was irradiated with ultraviolet light at 2 J/cm ² and then heat-treated at 170° C. for 1 hour in a nitrogen atmosphere to form a lower clad layer on the copper-clad laminate.

The cover film was peeled off from a resin sheet having a 10 μm thick photosensitive resin composition layer produced using the photosensitive resin composition produced in each of the above-mentioned Examples and Comparative Examples. A resin sheet was placed on the lower clad layer so that the photosensitive resin composition layer of the resin sheet and the lower clad layer were in contact with each other, and laminated using a vacuum laminator ("VP160" manufactured by Nikko Materials Co., Ltd.) to form a photosensitive resin composition layer on the lower clad layer. The lamination conditions were a vacuum drawing time of 30 seconds, a pressure bonding temperature of 100°C, a pressure bonding pressure of 0.7 MPa, and a pressure application time of 30 seconds. This resulted in a laminate having a copper-clad laminate, a lower clad layer, and a resin sheet in this order. The support was then peeled off to expose the photosensitive resin composition layer.

The photosensitive resin composition layer was exposed to ultraviolet light using a projection exposure device (Ushio Inc.'s "UFX-2240") with an exposure energy such that the number of gloss remaining steps of a 41-step tablet was 8. The exposure was performed using a quartz glass mask having a first mask pattern for drawing straight lines with L/S (line/space) 10 μm/10 μm, a second mask pattern for drawing straight lines with L/S (line/space) 5 μm/5 μm, and a third mask pattern for drawing straight lines with L/S (line/space) 3 μm/3 μm. After exposure, the substrate was left to stand at room temperature for 30 minutes, and then the support was peeled off. The entire surface of the photosensitive resin composition layer was spray-developed with a 1% by mass aqueous sodium carbonate solution at 30° C. as a developer at a spray pressure of 0.2 MPa for 1 minute. After spray development, the sample was irradiated with ultraviolet light at ² J/cm2, and then heat-treated at 170°C for 1 hour in a nitrogen atmosphere to obtain a sample having a copper-clad laminate, a lower clad layer, and a line layer (a layer formed of a cured product of the resin composition) in that order.

The obtained sample was observed with a scanning electron microscope (SEM) (magnification 2000 times) and the minimum fine line width (the width of the line layer with the smallest width among the line layers that were formed) was measured. The aspect ratio was calculated by dividing the thickness of the line layer by the minimum fine line width. The minimum fine line width in core formability was evaluated according to the following criteria. The line width refers to the width of the line layer.
◯: The aspect ratio is 0.8 or more for all line layers having a line width of 10 μm or less.
Δ: The aspect ratio is 0.6 or more and less than 0.8 in all line layers having a line width of 10 μm or less.
×: At least one aspect ratio of the line layers having a line width of 10 μm or less is less than 0.6.

[Optical transmission loss measurement]
(1-1. Formation of Lower Clad Layer)
The cover film was peeled off from the resin sheet having a 10 μm thick photosensitive resin composition layer produced using the resin composition produced in Production Example 1. The resin sheet was placed on a 4-inch silicon wafer so that the photosensitive resin composition layer and the silicon wafer were in contact with each other, and laminated using a vacuum laminator ("VP160" manufactured by Nikko Materials Co., Ltd.). The lamination conditions were a vacuum drawing time of 30 seconds, a pressure bonding temperature of 100° C., a pressure bonding pressure of 0.7 MPa, and a pressure application time of 30 seconds. Thereafter, the support was peeled off to obtain an intermediate laminate I having a silicon wafer and a photosensitive resin composition layer.

The photosensitive resin composition layer of the intermediate laminate I was exposed to ultraviolet light using a projection exposure device (Ushio Inc.'s "UFX-2240") with an exposure energy such that the number of gloss remaining steps of a 41-step tablet was 8. After exposure, ultraviolet light was irradiated at 2 J/ ^cm2 . The intermediate laminate I was placed in a clean oven and heated from room temperature to 170°C. After reaching 170°C, a heat treatment was performed for 60 minutes in a nitrogen atmosphere to cure the photosensitive resin composition layer. A lower clad layer was formed by curing the photosensitive resin composition layer, and an intermediate laminate II including a silicon wafer and a lower clad layer was obtained.

(1-2. Formation of Core Layer)
The cover film was peeled off from the resin sheet having a 5 μm thick photosensitive resin composition layer produced using the photosensitive resin composition produced in the examples and comparative examples. A resin sheet was placed on the surface of the lower clad layer of the intermediate laminate II so that the photosensitive resin composition layer and the lower clad layer were in contact with each other, and laminated using a vacuum laminator ("VP160" manufactured by Nikko Materials Co., Ltd.). The lamination conditions were a vacuum drawing time of 30 seconds, a pressure bonding temperature of 100° C., a pressure bonding pressure of 0.7 MPa, and a pressure application time of 30 seconds. Thereafter, the support was peeled off to obtain an intermediate laminate III having a silicon wafer, a base clad layer, and a photosensitive resin composition layer in this order.

The photosensitive resin composition layer of the intermediate laminate III was exposed to ultraviolet light using a projection exposure device (Ushio Inc.'s "UFX-2240") with an exposure energy that resulted in 8 gloss remaining steps of a 41-step tablet. The exposure was performed using a quartz glass mask having a mask pattern capable of drawing a plurality of straight lines with a length of 1 cm at L/S (line/space) 5 μm/100 μm, a mask pattern capable of drawing a plurality of straight lines with a length of 2 cm at L/S (line/space) 5 μm/100 μm, and a mask pattern capable of drawing a plurality of straight lines with a length of 3 cm at L/S (line/space) 5 μm/100 μm. In the L/S of this quartz glass mask, the line corresponds to the width of the core layer, and the space corresponds to the interval between the core layers. After exposure, the substrate was left to stand at room temperature for 30 minutes, and then the support was peeled off. The entire surface of the photosensitive resin composition layer was spray-developed with a 1% by mass aqueous sodium carbonate solution at 30° C. as a developer at a spray pressure of 0.2 MPa for 1 minute. After the spray development, ultraviolet irradiation was performed at 2 J/cm ^2. Thereafter, the intermediate laminate III was placed in a clean oven and heated from room temperature to 170° C. After reaching 170° C., a heat treatment was performed for 60 minutes in a nitrogen atmosphere to cure the photosensitive resin composition layer.

The photosensitive resin composition layer was cured to form a core layer, yielding intermediate laminate IV having a silicon wafer, a lower clad layer, and a core layer in this order.

(1-3. Formation of upper cladding layer)
The cover film was peeled off from the resin sheet having a 20 μm thick photosensitive resin composition layer produced using the resin composition produced in Production Example 1. A resin sheet was placed on the core layer of the intermediate laminate IV so that the photosensitive resin composition layer and the core layer were in contact with each other, and laminated using a vacuum laminator ("VP160" manufactured by Nikko Materials Co., Ltd.). The lamination conditions were a vacuum drawing time of 30 seconds, a pressure bonding temperature of 100° C., a pressure bonding pressure of 0.7 MPa, and a pressure application time of 30 seconds. Thereafter, the support was peeled off to obtain an intermediate laminate V having a silicon wafer, a lower clad layer, a core layer, and a photosensitive resin composition layer in this order.

The photosensitive resin composition layer of the intermediate laminate V was exposed to ultraviolet light using a projection exposure device (Ushio Inc.'s "UFX-2240") with an exposure energy such that the number of gloss remaining steps of a 41-step tablet was 8. After exposure, ultraviolet light irradiation was performed at 2 J/ ^cm2 . The intermediate laminate V was placed in a clean oven and heated from room temperature to 170°C. After reaching 170°C, a heat treatment was performed for 60 minutes in a nitrogen atmosphere to cure the photosensitive resin composition layer. An upper clad layer was formed by curing the photosensitive resin composition layer, and a sample laminate having a silicon wafer, a lower clad layer, a core layer, and an upper clad layer in this order was obtained.

In this sample laminate, the combination of the lower cladding layer and the upper cladding layer constituted the cladding layer. Thus, an optical waveguide was obtained that included the cladding layer and a core layer within the cladding layer. In addition, in this sample laminate, the core layer had linear patterns of lengths of 1 cm, 2 cm, and 3 cm that corresponded to the mask pattern of the quartz glass mask, and the width (line width) and interval (space) of the core layer included in these patterns matched the width (line width) and interval (space) of the mask pattern.

[Evaluation of Optical Waveguides]
(Measurement of optical transmission loss of a calibration optical system)
The transmission loss of an optical system was measured, which was configured by removing the test substrate and the light collecting module from the optical system for measuring the transmission loss of the test substrate described later. That is, a light source (1310 nm light source, THORLABS's "LPSC-1310-FC") and a light receiver (Keysight's optical power meter "N7742") were connected via an optical fiber (input fiber) on a vibration isolation table covered with a blackout curtain to obtain an optical system for calibration. The light source was made to emit light, and the intensity of the light that entered the light receiver was measured by the light receiver, and the loss of this optical system for calibration was measured.

(Preparation of test board)
From the sample laminates produced using the photosensitive resin compositions of the Examples and Comparative Examples, the core layer and the surrounding clad layer were cut out at the portion where the core layer was formed, to obtain a test substrate equipped with an optical transmission path.

(Optical transmission loss measurement)
A test substrate was placed on a vibration isolation table covered with a blackout curtain. A light collecting module (numerical aperture 0.18) was connected to one end (incoming end) of the optical waveguide of the test substrate, and a light source (1310 nm light source, THORLABS's "LPSC-1310-FC") was connected to the light collecting module via an optical fiber (incoming fiber). Another light collecting module (numerical aperture 0.18) was connected to the other end (outgoing end) of the optical waveguide of the test substrate, and a light receiver (Keysight's optical power meter "N7742") was connected to the light collecting module via an optical fiber (outgoing fiber). By the above operations, an optical system was obtained in which light emitted from the light source passes through the optical fiber (incoming fiber), the light collecting module, the optical waveguide, the light collecting module, and the optical fiber (outgoing fiber) in this order, and then enters the light receiver. Hereinafter, this optical system may be referred to as a sample optical system. The light source was turned on and the intensity of the light that entered the receiver was measured by the receiver to measure the loss of the sample optical system.

The loss of the optical waveguide included in the test substrate was calculated by subtracting the loss of the calibration optical system from the loss of the sample optical system.

(Measurement of Transmission Loss (dB/cm) of Optical Waveguide)
The loss of the optical waveguide was measured for each of an optical waveguide having a length of 1 cm, an optical waveguide having a length of 2 cm, and an optical waveguide having a length of 3 cm. The measurement results were plotted on a coordinate system with the length of the optical waveguide on the horizontal axis and the loss of the optical waveguide on the vertical axis to obtain three coordinates representing the measurement results. An approximation line of these three points was calculated by the least squares method, and the slope of the approximation line was calculated as the loss (transmission loss) per unit distance of the optical waveguide, and was evaluated according to the following criteria.
◎: Optical transmission loss less than 0.5 dB/cm ◯: Optical transmission loss 0.5 dB/cm or more and less than 1.0 dB/cm △: Optical transmission loss 1.0 dB/cm or more and less than 2.0 dB/cm ×: Optical transmission loss 2.0 dB/cm or more

(Check the mode)
The receiver was removed and replaced with an infrared camera (InGaAs camera with 100x objective lens). The light source was turned on and the light emitted from the end of the optical fiber (output fiber) was photographed with the infrared camera. When only one circular light edge was observed, it was determined to be single mode. When multiple edges were observed, it was determined to be multimode.
In the table, "S" means single mode and "M" means multimode.

[Measurement of absorbance of photosensitive resin composition solution]
Solutions of the photosensitive resin compositions produced in the Examples and Comparative Examples were prepared, and the absorbance of the solutions was measured by the following method. That is, a mixed solvent of MEK (methyl ethyl ketone) and cyclopentanone (MEK:pentanone=1:1) was mixed with the photosensitive resin compositions produced in the Examples and Comparative Examples to prepare a photosensitive resin composition solution with a concentration of 20% by mass. This solution was placed in a 1 cm quartz cell, and the absorbance Abs at a wavelength of 1310 nm was measured using a UV-Vis-NIR spectrophotometer (V-770, manufactured by JASCO Corporation), and evaluated according to the following criteria.
◎: absorbance less than 0.0025 ◯: absorbance 0.0025 or more and less than 0.0050 △: absorbance 0.0050 or more and less than 0.0100 ×: absorbance 0.0100 or more

<Evaluation of arithmetic mean roughness and peel strength of copper-plated conductor layer>
(Preparation of Evaluation Laminate A and Sample A)
The copper layer of a glass epoxy board (copper-clad laminate) on which a circuit patterned with a copper layer having a thickness of 18 μm was formed was roughened by treatment with a surface treatment agent containing an organic acid (CZ8100, manufactured by MEC Co., Ltd.). Next, a resin sheet manufactured in advance was placed so that the photosensitive resin composition layer was in contact with the copper circuit surface, and laminated using a vacuum laminator (manufactured by Nikko Materials Co., Ltd., VP160), and the copper-clad laminate, the photosensitive resin composition layer, and the support were laminated in this order to prepare an evaluation laminate A. The pressure bonding conditions were a vacuum drawing time of 30 seconds, a pressure bonding temperature of 80° C., a pressure bonding pressure of 0.7 MPa, and a pressure application time of 30 seconds. After preparing the evaluation laminate A, it was left to stand at room temperature (25° C.) for 30 minutes or more.

Using a pattern forming device, ultraviolet exposure was performed from the support of the evaluation laminate A at an exposure energy such that the number of gloss remaining steps of the 41-step step tablet was 8. A quartz glass mask without an exposure pattern was used. After leaving it at room temperature for 30 minutes, the support was peeled off from the evaluation laminate A. A 1% by mass aqueous sodium carbonate solution at 30 ° C. was used as a developer on the entire surface of the photosensitive resin composition layer on the evaluation laminate A for 1 minute for spray development at a spray pressure of 0.2 MPa. After spray development, ultraviolet irradiation at 2 J / cm ² was performed, and further heat treatment at 170 ° C. for 1 hour was performed to cure the photosensitive resin composition layer.

The evaluation laminate A was immersed in a swelling liquid, Swelling Dip Securigand P containing diethylene glycol monobutyl ether manufactured by Atotech Japan, at 60°C for 10 minutes, then in a roughening liquid, Concentrate Compact P (aqueous solution of KMnO4: 60 g/L, NaOH: 40 g/L) manufactured by Atotech Japan, at 80°C for 10 minutes, and finally in a neutralizing liquid, Reduction Showreusin Securigant P manufactured by Atotech Japan, at 40°C for 5 minutes. The laminate after this roughening treatment was designated as Sample A.

(Evaluation of arithmetic mean roughness (Ra))
For sample A, the arithmetic mean roughness (Ra) was calculated using a non-contact surface roughness meter (WYKO NT3300 manufactured by Veeco Instruments) in VSI mode with a 50x lens over a measurement range of 121 μm × 92 μm. The average of 10 points was calculated as the measured value, and the results were evaluated according to the following criteria.
◯: arithmetic mean roughness is less than 200 nm △: arithmetic mean roughness is 200 nm or more and 400 nm or less ×: arithmetic mean roughness is greater than 400 nm

(Evaluation of the peel strength of the copper-plated conductor layer)
In order to form a circuit on the insulating layer surface, sample A was immersed in an electroless plating solution containing _PdCl2 , and then immersed in an electroless copper plating solution. After heating at 150 ° C for 30 minutes to perform an annealing treatment, an etching resist was formed, and after forming a pattern by etching, copper sulfate electroplating was performed to form a conductor layer with a thickness of 25 μm. Next, an annealing treatment was performed at 180 ° C for 60 minutes. The sample obtained in this manner was designated as sample B.

A cut was made in the conductor layer of Sample B having a width of 10 mm and a length of 100 mm, and one end of the cut was peeled off and held with a gripper (Autocom type testing machine, AC-50C-SL, manufactured by TSE Corporation). The load (kgf/cm) when 35 mm was peeled off in the vertical direction at a speed of 50 mm/min at room temperature was measured and the result was evaluated according to the following criteria.
◯: Peel strength is 0.3 kgf/cm or more △: Peel strength is less than 0.3 kgf/cm, 0.2 kgf/cm or more ×: Peel strength is less than 0.2 kgf/cm

REFERENCE SIGNS LIST 10 Optical waveguide 100 Core layer 110 Second composition layer 111 Exposed portion 112 Non-exposed portion 200 Cladding layer 210 First composition layer 220 Cured first composition layer (lower cladding layer)
230 Third composition layer 240 Cured third composition layer (upper clad layer)
300: Substrate 400: Mask 410: Light-transmitting portion 420: Light-shielding portion 500: Conductive layer

Claims (14)

(A) an epoxy resin,
(B) a resin containing a carboxy group and an ethylenic double bond,
A photosensitive resin composition comprising: (C) a photopolymerization initiator; and (D) a non-developable polymer having a solubility parameter (SP value) of 9 (cal/cm ³ ) ^1/2 or more and 13 (cal/cm ³ ) ^1/2 or less. The photosensitive resin composition according to claim 1, wherein the weight average molecular weight of component (D) is 3,000 or more and 100,000 or less. The photosensitive resin composition according to claim 1, wherein component (D) includes an acrylic polymer. 2. The photosensitive resin composition according to claim 1, wherein the component (D) has a structural unit represented by the following formula (D-1) and a structural unit represented by the following formula (D-2):

In formula (D-1), R ¹ 's each independently represent a hydrogen atom or a methyl group, and R ² 's each independently represent a hydrogen atom or an alkyl group having 1 to 22 carbon atoms. p's each independently represent an integer of 2 to 4, and q's each independently represent an integer of 2 to 100.
In formula (D-2), R ³ 's each independently represent a hydrogen atom or a methyl group, and R ⁴ 's each independently represent an alkyl group having 1 to 22 carbon atoms. 2. The photosensitive resin composition according to claim 1, wherein the component (B) has a solubility parameter (SP value) of 9 (cal/cm ³ ) ^1/2 or more and 11 (cal/cm ³ ) ^1/2 or less. The photosensitive resin composition according to claim 1, further comprising (E) an inorganic filler having an average particle size of 100 nm or less. The photosensitive resin composition according to claim 1, which is used for producing a core layer of an optical waveguide. A support and a photosensitive resin composition layer formed on the support,
A resin sheet, wherein the photosensitive resin composition layer comprises the photosensitive resin composition according to any one of claims 1 to 7. The resin sheet according to claim 8, wherein the thickness of the photosensitive resin composition layer is 1 μm or more and 15 μm or less. A photosensitive resin composition set including a core photosensitive resin composition and a clad resin composition,
A photosensitive resin composition set, comprising a core photosensitive resin composition comprising the photosensitive resin composition according to any one of claims 1 to 7. A core layer and a clad layer are provided.
An optical waveguide, wherein a core layer comprises a cured product of the photosensitive resin composition according to any one of claims 1 to 7. The optical waveguide according to claim 11, capable of transmitting light having a wavelength of 1300 nm to 1320 nm. The optical waveguide of claim 12, which is a single-mode optical waveguide. An optical/electrical hybrid board comprising the optical waveguide according to claim 13.

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