JP7540464B2 - Resin sheet with support - Google Patents

Description

The present invention relates to a resin sheet with a support having a resin composition layer containing a photopolymerizable resin.

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).

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 equipped with this chip, it is necessary to provide a fine 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. However, the finer the optical waveguide formed, the more likely it is to be dissolved in a developer, but on the other hand, there is a problem that the surface irregularities of the core of the optical waveguide become large, increasing transmission loss. Therefore, there is a demand for a resin sheet with a support that has high fine wiring formability due to better core formability, while being able to form an optical waveguide with reduced optical transmission loss.

JP 2019-211540 A Patent No. 5771978

The objective of the present invention is to provide a resin sheet with a support that has superior core forming properties and is capable of forming an optical waveguide with reduced optical transmission loss.

As a result of intensive research, the inventors have found that by using a resin sheet with a support having a support with a haze of 10% or less, or a support with an arithmetic mean roughness (Ra) of the contact surface of the support with the resin composition layer of 50 nm or less, it is possible to form an optical waveguide with better core forming properties and reduced optical transmission loss, and have completed the present invention.

That is, the present invention includes the following.
[1] A resin sheet with a support, comprising a support and a resin composition layer provided on the support,
the resin composition layer is a resin composition layer formed of a resin composition containing (A) an epoxy resin, (B) a photopolymerizable resin containing a carboxyl group, and (C) a photopolymerization initiator;
A resin sheet with a support for forming a core of an optical waveguide, which satisfies at least one of conditions (1) and (2).
Condition (1): The haze of the support measured in accordance with JIS K6714 is 10% or less.
Condition (2): The arithmetic mean roughness (Ra) of the contact surface of the support with the resin composition layer is 50 nm or less.
[2] The support-attached resin sheet according to the above [1], which satisfies the condition (1).
[3] The support-attached resin sheet according to the above [1], which satisfies both conditions (1) and (2).
[4] The support-attached resin sheet according to the above-mentioned [1], wherein the support is a polyethylene terephthalate film.
[5] The support-attached resin sheet according to the above [1], wherein the support has a thickness in the range of 10 μm to 50 μm.
[6] The support-attached resin sheet according to the above [1], wherein the thickness of the resin composition layer is in the range of 3 μm to 30 μm.
[7] The resin sheet with a support according to the above [1], wherein the component (A) contains an epoxy resin having a naphthol aralkyl skeleton.
[8] The supported resin sheet according to the above [1], wherein the component (B) contains a photopolymerizable resin containing an ethylenically unsaturated group and a carboxyl group.
[9] The support-attached resin sheet according to the above [1], wherein the component (B) contains a photopolymerizable resin having a naphthol aralkyl skeleton.
[10] The support-attached resin sheet according to the above [1], wherein the component (B) contains a carboxylic acid-modified epoxy (meth)acrylate resin.
[11] The support-attached resin sheet according to the above [1], wherein the weight average molecular weight (Mw) of the component (B) is 18,000 or less.
[12] The support-attached resin sheet according to the above [1], wherein the molecular weight of the component (C) is 400 or more.
[13] The supported resin sheet according to the above [1], wherein the component (C) contains at least one photopolymerization initiator selected from an α-aminoketone-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, and an oxime ester-based photopolymerization initiator.
[14] The resin sheet with a support according to the above [1], wherein the mass ratio of the component (A) to the component (B) in the resin composition forming the resin composition layer (component (A)/component (B)) is 0.1 to 3.
[15] The resin sheet with a support according to the above [1], wherein the mass ratio of the component (B) to the component (C) in the resin composition forming the resin composition layer (component (B)/component (C)) is 1 to 50.
[16] The resin sheet with a support according to the above [1], wherein the resin composition forming the resin composition layer further contains (D) a reactive diluent.
[17] The support-attached resin sheet according to the above [16], wherein the component (D) contains a difunctional or higher functional (meth)acrylate compound not containing a carboxyl group.
[18] The support-attached resin sheet according to the above [16], wherein the molecular weight of the component (D) is 1,000 or less.
[19] (III) a step of laminating the supported resin sheet according to any one of the above [1] to [18] onto a lower clad layer so that the resin composition layer is in contact with the lower clad layer to form a resin composition layer on the lower clad layer;
(IV) placing a mask on the support and subjecting a part of the resin composition layer to an exposure treatment through the mask and the support;
(V) removing the mask and the support;
(VI) subjecting the resin composition layer to a development treatment to form a resin composition pattern;
(VII) curing the resin composition pattern to form a core on the lower clad layer;
A method for manufacturing an optical waveguide comprising the steps of:

The resin sheet with support of the present invention has superior core forming properties and can form an optical waveguide with reduced optical transmission loss.

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

The present invention will be described in detail below based on its preferred embodiments. However, the present invention is not limited to the following embodiments and examples, and can be modified as desired without departing from the scope of the claims of the present invention and their equivalents.

<Resin sheet with support>
The resin sheet with a support of the present invention is a resin sheet with a support having a support and a resin composition layer provided on the support,
the resin composition layer is a resin composition layer formed of a resin composition containing (A) an epoxy resin, (B) a photopolymerizable resin containing a carboxyl group, and (C) a photopolymerization initiator;
At least one of the conditions (1) and (2) is satisfied.
Condition (1): The haze of the support measured in accordance with JIS K6714 is 10% or less.
Condition (2): The arithmetic mean roughness (Ra) of the contact surface of the support with the resin composition layer is 50 nm or less.

The resin sheet with support of the present invention is used to form the core of an optical waveguide in the manufacture of the optical waveguide.

The resin sheet with support of the present invention has superior core forming properties and can form an optical waveguide with reduced optical transmission loss.

In condition (1), the haze of the support measured in accordance with JIS K6714 is 10% or less, and from the viewpoint of achieving better core formability, it is preferably 9% or less, more preferably 8% or less, more preferably 7% or less, and particularly preferably 6% or less. The lower limit of the haze of the support is not particularly limited, but may be, for example, 0.1%.

In condition (2), the arithmetic mean roughness (Ra) of the contact surface of the support with the resin composition layer is 50 nm or less, and from the viewpoint of achieving better core formability, is preferably 40 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less, and particularly preferably 15 nm or less.

The resin sheet with a support of the present invention preferably satisfies condition (1), and particularly preferably satisfies both conditions (1) and (2).

From the viewpoint of achieving better core formability, it is preferable that the support-attached resin sheet of the present invention further satisfies the condition (3).
Condition (3): The total light transmittance measured in accordance with JIS K 7361-1 is 70% or more, preferably 80% or more, more preferably 85% or more, and further preferably 87% or more.

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 "Lumirror FB-40" and "QS63" manufactured by Toray Industries, Inc., and "S-25", "S-38", and "PET-12" manufactured by Unitika Ltd. These supports are preferably coated on the surface with a release agent such as a silicone coating agent to facilitate removal of the resin composition layer.

The thickness of the support is preferably in the range of 5 μm to 100 μm, and more preferably in the range of 10 μm to 50 μm. By making the thickness 5 μm or more, it is possible to prevent the support from being torn when the support is peeled off before development, and by making the thickness 100 μm or less, it is possible to improve the resolution when exposing from above the support.

In addition, a support with few fisheyes is preferred. Fisheyes here refer to foreign matter, undissolved matter, oxidized deterioration products, etc., that are introduced into the film when the material is thermally melted and then kneaded, extruded, biaxially stretched, cast, or other methods are used to produce the film.

The resin composition layer may be protected by a protective film. By protecting the resin composition layer side of the resin sheet with the support with a protective film, it is possible to prevent the adhesion of dirt and the like to the surface of the 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 resin composition layer and the protective film is smaller than the adhesive strength between the resin composition layer and the support.

The resin sheet with a support can be produced, for example, by applying the resin composition described below, either directly or in a varnish form dissolved in an organic solvent, onto a support, and then drying the organic solvent by heating or blowing hot air, etc., to form a resin composition layer. Specifically, first, bubbles in the resin composition are completely removed by a vacuum degassing method, etc., and then the resin composition is applied onto a support, the solvent is removed using a hot air oven or far-infrared oven, the support is dried, and then, if necessary, a protective film is laminated onto the resulting resin composition layer, thereby producing a resin sheet with a support.

Specific drying conditions vary depending on the curability of the resin composition and the amount of organic solvent in the resin composition, but for resin compositions containing 30% to 60% by mass of organic solvent, it is preferable to dry at 80°C to 120°C for 3 to 13 minutes, so that the content of the organic solvent (H) falls within the suitable range described below. Those skilled in the art can set suitable drying conditions by simple experimentation.

From the viewpoint of improving handleability and suppressing a decrease in sensitivity and resolution inside the resin composition layer, the thickness of the resin composition layer is preferably in the range of 1 μm to 500 μm, more preferably in the range of 1 μm to 100 μm, even more preferably in the range of 1 μm to 50 μm, even more preferably in the range of 1 μm to 40 μm, and particularly preferably in the range of 1 μm to 30 μm.

Examples of methods for applying the 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 resin composition may be applied to the support in several separate applications, in one application, or by a combination of different methods. Among these, the die coating method is preferred because of its 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.

The resin composition layer is a resin composition layer formed of a resin composition containing (A) an epoxy resin, (B) a photopolymerizable resin containing a carboxyl group, and (C) a photopolymerization initiator. The resin composition forming the resin composition layer may further contain optional components in addition to (A) an epoxy resin, (B) a photopolymerizable resin containing a carboxyl group, and (C) a photopolymerization initiator. Examples of optional components include (D) a reactive diluent, (E) a photosensitizer, (F) an inorganic filler, (G) other additives, and (H) an organic solvent. Each component contained in the resin composition will be described in detail below.

<(A) Epoxy Resin>
The resin composition forming the resin composition layer contains 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 A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol novolac type epoxy resins, phenol novolac type epoxy resins, tert-butyl-catechol type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, anthracene type epoxy resins, glycidylamine type epoxy resins, glycidyl ether Examples of the epoxy resin include ester type epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, linear aliphatic epoxy resin, epoxy resin having a butadiene structure, alicyclic epoxy resin, heterocyclic epoxy resin, spiro ring-containing epoxy resin, cyclohexane type epoxy resin, cyclohexane dimethanol type epoxy resin, naphthylene ether type epoxy resin, trimethylol type epoxy resin, tetraphenylethane type epoxy resin, isocyanurate type epoxy resin, phenolphthalimidine type epoxy resin, etc. (A) The epoxy resin may be used alone or in combination of two or more types.

The resin composition forming the resin composition layer preferably contains, as the epoxy resin (A), an epoxy resin having two or more epoxy groups in one molecule. The proportion 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.

(A) Epoxy resins include epoxy resins that are liquid at a temperature of 20°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 20°C (hereinafter sometimes referred to as "solid epoxy resins"). The resin composition that forms the resin composition layer may contain only liquid epoxy resins as epoxy resins, or only solid epoxy resins, or both liquid and solid epoxy resins, but it is particularly preferable that the resin composition contains only solid epoxy resins or both liquid and solid epoxy resins.

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," DIC's "850" (bisphenol A-type epoxy resin); and Mitsubishi Chemical's "jER807." , "1750" (bisphenol F type epoxy resin); "jER152" (phenol novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630", "630LSD", and "604" (glycidylamine type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "ED-523T" (glycirol type epoxy resin) manufactured by ADEKA Corporation; "EP-3950L" and "EP-3980S" (glycidylamine type epoxy resin) manufactured by ADEKA Corporation; "EP-4088S" ( dicyclopentadiene 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) resin); 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); Nagase ChemteX's "EX-201" (cyclic aliphatic glycidyl ether), etc.

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.

Preferred solid epoxy resins are 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.

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 "HP-7200", "HP-7200HH", "HP-7200H", and "HP-7200L" (dicyclopentadiene type epoxy resin); and DIC's "EXA-7311". , "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthylene ether type epoxy resin); "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", "ESN4 100V (naphthalene type epoxy resin); "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 resin) 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.; "Y Examples of such epoxy resins include "X7700" (phenol aralkyl type epoxy resin); "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals; "YL7760" (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical; "YL7800" (fluorene type epoxy resin) manufactured by Mitsubishi Chemical; "jER1010" (bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical; "jER1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical; 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.

In one embodiment, the (A) epoxy resin preferably contains an epoxy resin having a skeleton selected from a naphthalene skeleton and a biphenyl skeleton, more preferably contains an epoxy resin having a naphthalene skeleton, and particularly preferably contains an epoxy resin having a naphthol aralkyl 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 the epoxy resin (A) in the resin composition forming the resin composition layer is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and particularly preferably 20% by mass or more, from the viewpoint of further improving mechanical strength and insulation reliability, assuming that the non-volatile components of the resin composition are 100% by mass. The upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less, from the viewpoint of improving alkaline developability.

<(B) Photopolymerizable resin containing a carboxyl group>
The resin composition forming the resin composition layer contains (B) a photopolymerizable resin containing a carboxyl group. The resin composition containing (B) a photopolymerizable resin containing a carboxyl group can be soluble in an alkaline developer (e.g., a 1% by mass aqueous sodium carbonate solution). The number of carboxyl groups per molecule of (B) the photopolymerizable resin containing a carboxyl group may be one or more.

(B) The photopolymerizable resin containing a carboxyl group preferably contains a photopolymerizable resin containing an ethylenically unsaturated group and a carboxyl group. The ethylenically unsaturated group is a photopolymerizable functional group having a carbon-carbon double bond, and examples thereof include a vinyl group, an allyl group, a propargyl group, a butenyl group, an ethynyl group, a phenylethynyl group, a maleimide group, a nadimide group, an acryloyl group, and a methacryloyl group. From the viewpoint of the reactivity of photoradical polymerization, an acryloyl group and a methacryloyl group are preferred. (B) The number of ethylenically unsaturated groups per molecule of the photopolymerizable resin containing a carboxyl group may be one or may be two or more. In addition, when (B) the photopolymerizable resin containing a carboxyl group contains two or more ethylenically unsaturated groups per molecule, the ethylenically unsaturated groups may be the same or different.

(B) The photopolymerizable resin containing a carboxyl group is preferably a resin that has both an ethylenically unsaturated group and a carboxyl group, and that allows photoradical polymerization and alkaline development.

In one embodiment, the photopolymerizable resin (B) containing a carboxyl group preferably contains a photopolymerizable resin having a skeleton selected from a naphthalene skeleton and a biphenyl skeleton, more preferably contains a photopolymerizable resin having a naphthalene skeleton, and particularly preferably contains a photopolymerizable resin having a naphthol aralkyl skeleton.

In one embodiment, it is particularly preferred that (B) the photopolymerizable resin containing a carboxyl group has the same backbone as (A) the epoxy resin.

(B) The photopolymerizable resin containing a carboxyl group preferably contains a resin selected from a carboxylic acid-modified epoxy (meth)acrylate resin and a carboxylic acid-containing (meth)acrylic (meth)acrylate resin, and more preferably contains a carboxylic acid-modified epoxy (meth)acrylate resin.

Carboxylic acid-modified epoxy (meth)acrylate resins can be produced using epoxy (meth)acrylate resins. Epoxy (meth)acrylate resins can be produced, for example, by reacting epoxy resins 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 reducing the average linear thermal expansion coefficient. Here, the aromatic skeleton is a concept that includes polycyclic aromatics and aromatic heterocycles. Among them, any of 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 is preferable.

Carboxylic acid-modified epoxy (meth)acrylate resins can be produced, for example, by reacting epoxy (meth)acrylate resins with polycarboxylic acid anhydrides.

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.

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

Carboxylic acid-modified epoxy (meth)acrylate resins can be synthesized by known methods, but commercially available products may also be used. Specific examples of commercially available products include "CCR-1373H" (acid-modified epoxy acrylate containing a cresol novolac skeleton), "ZCR-8001H" (acid-modified epoxy acrylate containing a biphenyl skeleton), "ZCR-1569H" (acid-modified epoxy acrylate containing a biphenyl skeleton), "CCR-1171H" (acid-modified epoxy acrylate containing a cresol novolac skeleton), and "ZCR-1797H" (acid-modified epoxy acrylate containing a biphenyl skeleton), all manufactured by Nippon Kayaku Co., Ltd. acrylate), 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" (cresol novolac skeleton-containing epoxy acrylate resin), etc. These may be used alone or in combination of two or more.

(B) The acid value of the photopolymerizable resin containing a carboxyl group 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, and particularly preferably 40 mgKOH/g or more, 50 mgKOH/g or more, from the viewpoint of improving the alkaline developability of the resin composition. (B) The upper limit of the acid value of the photopolymerizable resin containing a carboxyl group is preferably 200 mgKOH/g or less, more preferably 150 mgKOH/g or less, even more preferably 120 mgKOH/g or less, and particularly preferably 100 mgKOH/g or less, from the viewpoint of improving the insulation reliability.

(B) The weight average molecular weight of the photopolymerizable resin containing a carboxyl group is preferably 20,000 or less, more preferably 18,000 or less, and even more preferably 15,000 or less. (B) The lower limit of the weight average molecular weight of the photopolymerizable resin containing a carboxyl group is preferably 1000 or more, and more preferably 1,500 or more. The weight average molecular weight is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

The content of (B) photopolymerizable resin containing a carboxyl group in the resin composition forming the resin composition layer is preferably 1% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and particularly preferably 30% by mass or more, from the viewpoint of improving alkaline developability, when the non-volatile components of the resin composition are taken as 100% by mass. The upper limit is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less, from the viewpoint of improving heat resistance.

The mass ratio ((A) component/(B) component) of the epoxy resin (A) to the photopolymerizable resin (B) containing a carboxyl group in the resin composition forming the resin composition layer is preferably 0.03 or more, more preferably 0.1 or more, and even more preferably 0.3 or more. The upper limit is preferably 10 or less, more preferably 3 or less, and even more preferably 1 or less.

<(C) Photopolymerization initiator>
The resin composition that forms the resin composition layer contains a photopolymerization initiator (C).

Examples of the (C) photopolymerization initiator include α-aminoketone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, oxime ester-based photopolymerization initiators, α-hydroxyketone-based photopolymerization initiators, benzoin-based photopolymerization initiators, and benzyl ketal-based photopolymerization initiators. The (C) photopolymerization initiator preferably contains at least one photopolymerization initiator selected from α-aminoketone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and oxime ester-based photopolymerization initiators, and is particularly preferably an α-aminoketone-based photopolymerization initiator. The (C) photopolymerization initiator may be used alone or in combination of two or more types.

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, and 2-(dimethylamino)-2-(4-methylphenylmethyl)-1-(4-morpholinophenyl)butan-1-one (Omnirad). 379EG), polyethylene glycol di(β-4-[4-(2-dimethylamino-2-benzyl)butanoylphenyl]piperazine)propionate (Omnipol 910), etc. The photopolymerization initiator may be used alone or in combination of two or more.

Examples of acylphosphine 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) (Omnipol TP), etc.

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

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.

Benzyl ketal photopolymerization initiators include, for example, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, etc.

(C) The photopolymerization initiator preferably contains a structure selected from a polybutylene glycol structure, a polypropylene glycol structure, and a polyethylene glycol structure, and more preferably contains a polyethylene glycol structure.

The molecular weight of the photopolymerization initiator (C) is preferably 200 or more, more preferably 400 or more, even more preferably 600 or more, and particularly preferably 800 or more. There is no particular upper limit to the molecular weight of the photopolymerization initiator (C), but it is preferably 4,000 or less, more preferably 2,000 or less.

(C) The photopolymerization initiator is preferably a compound having a maximum absorption wavelength in the wavelength region of 200 nm to 450 nm, more preferably a compound having a maximum absorption wavelength in the wavelength region of 250 nm to 400 nm, and particularly preferably a compound having a maximum absorption wavelength in the wavelength region of 275 nm to 375 nm.

When the (C) photopolymerization initiator is taken as 100% by mass, the (C) photopolymerization initiator preferably contains 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more of an α-aminoketone-based photopolymerization initiator.

The content of the (C) photopolymerization initiator in the resin composition forming the resin composition layer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, when the non-volatile components of the resin composition are taken as 100% by mass. The upper limit is preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 10% by mass or less.

The mass ratio ((B) component/(C) component) of the photopolymerizable resin containing a carboxyl group (B) to the photopolymerization initiator (C) in the resin composition forming the resin composition layer is preferably 0.3 or more, more preferably 1 or more, and even more preferably 3 or more. The upper limit is preferably 200 or less, more preferably 50 or less, and even more preferably 15 or less.

<(D) Reactive Diluent>
The resin composition forming the resin composition layer may contain a reactive diluent (D) as an optional component. The reactive diluent (D) is a component that does not fall under the category of the photopolymerizable resin containing a carboxyl group (B). The reactive diluent (D) does not contain a carboxyl group.

The (D) reactive diluent preferably contains a compound having an ethylenically unsaturated group. The (D) reactive diluent preferably contains a compound having two or more ethylenically unsaturated groups in one molecule. Examples of the ethylenically unsaturated group include an acryloyl group (-CO-CH=CH ₂ ) and a methacryloyl group (-CO-C(CH ₃ )=CH ₂ ). The (D) reactive diluent may be used alone or in combination of two or more.

(D) Examples of reactive diluents include bifunctional (meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate; trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate. (meth)acrylate compounds such as trifunctional (meth)acrylate compounds, such as (meth)acrylate and dipentaerythritol tri(meth)acrylate; and (meth)acrylate compounds having tetrafunctional or more, such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrimethylolpropane hexa(meth)acrylate.

(D) The reactive diluent preferably contains a difunctional or higher (meth)acrylate compound that does not contain a carboxyl group, more preferably a trifunctional or higher (meth)acrylate compound that does not contain a carboxyl group, and particularly preferably a tetrafunctional or higher (meth)acrylate compound that does not contain a carboxyl group.

The molecular weight of the reactive diluent (D) is preferably 1,000 or less, more preferably 800 or less. The lower limit of the molecular weight of the reactive diluent (D) is not particularly limited, but may be, for example, 150 or more.

The content of the (D) reactive diluent in the resin composition forming the resin composition layer is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and particularly preferably 20% by mass or more, from the viewpoint of further improving the photocurability, assuming that the non-volatile components of the resin composition are 100% by mass. The upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less.

The mass ratio ((B) component/(D) component) of the photopolymerizable resin containing a carboxyl group (B) to the reactive diluent (D) in the resin composition forming the resin composition layer is preferably 0.1 or more, more preferably 0.3 or more, and even more preferably 1 or more. The upper limit is preferably 30 or less, more preferably 10 or less, and even more preferably 3 or less.

<(E) Photosensitizer>
The resin composition forming the resin composition layer may contain a photosensitizer (E) as an optional component. By containing the photosensitizer (E), photocurability can be improved.

(E) Examples of photosensitizers include thioxanthones, benzophenones, etc.

Specific examples of thioxanthones include 2-isopropylthioxanthone, 1-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone (DETX-S), 2,4-diisopropylthioxanthone, 2-chlorothioxanthone, polybutylene glycol bis(9-oxo-9H-thioxanthenyloxy)acetate (Omnipol TX), etc.

Specific examples of benzophenones include 4,4'-bis(diethylamino)benzophenone (EAB) and 4,4'-bis(dimethylamino)benzophenone.

In one embodiment, the photosensitizer (E) preferably contains a structure selected from a polybutylene glycol structure, a polypropylene glycol structure, and a polyethylene glycol structure, and more preferably contains a polybutylene glycol structure.

The molecular weight of the (E) photosensitizer is preferably 200 or more. There is no particular upper limit to the molecular weight of the (E) photosensitizer, but it is preferably 4,000 or less, more preferably 2,000 or less.

(E) The photosensitizer is preferably a compound having a maximum absorption wavelength in the wavelength region of 200 nm to 450 nm, more preferably a compound having a maximum absorption wavelength in the wavelength region of 300 nm to 400 nm, and particularly preferably a compound having a maximum absorption wavelength in the wavelength region of 325 nm to 375 nm.

From the viewpoint of efficiently transmitting energy to the photopolymerization initiator (C), the lowest excited triplet energy level of the photosensitizer (E) is preferably higher than the excited triplet energy level of the photopolymerization initiator (C). The lowest excited triplet energy level of the photosensitizer (E) is preferably 0.1 kcal/mol to 20 kcal/mol higher, more preferably 0.1 kcal/mol to 15 kcal/mol higher, and particularly preferably 0.1 kcal/mol to 10 kcal/mol higher than the excited triplet energy level of the photopolymerization initiator (C).

The content of the (E) photosensitizer in the resin composition forming the resin composition layer is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, when the non-volatile components of the resin composition are taken as 100% by mass. The lower limit is, for example, 0% by mass or more, 0.001% by mass or more, and from the viewpoint of further improving the photocurability, it is preferably 0.01% by mass or more, more preferably 0.05% by mass or more.

<(F) Inorganic filler>
The resin composition forming the resin composition layer may contain an inorganic filler (F) as an optional component. The inorganic filler (F) is contained in the resin composition in the form of particles.

(F) An inorganic compound is used as the material for the inorganic filler. (F) Examples of the material for the inorganic filler include silica, alumina, aluminosilicate, 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. (F) The inorganic filler may be used alone or in any combination of two or more types in any ratio.

(F) Commercially available inorganic fillers include, for example, "UFP-30" manufactured by Denka Chemical Industry Co., Ltd.; "SP60-05" and "SP507-05" manufactured by Nippon Steel & Sumitomo Metal Materials Co., Ltd.; "SC2500SQ", "SO-C4", "SO-C2", "SO-C1", "SC2300-SVJ", "SC2050-SXF", "YC100C", "YA050C", "YA050C-MJE", "YA010C", and "Y50SZ-AM1" manufactured by Admatechs Co., Ltd.; "UFP-30" manufactured by Denka Company; "Silfill NSS-3N", "Silfill NSS-4N", and "Silfill NSS-5N" manufactured by Tokuyama Corporation; and "DAW-03" and "FB-105FD" manufactured by Denka Company, Ltd.

(F) The average particle size of the inorganic filler is not particularly limited, but is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 1 μm or less, even more preferably 0.5 μm or less, and particularly preferably 0.1 μm or less. (F) The lower limit of the average particle size of the inorganic filler is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.02 μm or more, and even more preferably 0.03 μm or more. (F) The average particle size of the inorganic filler can be measured by a laser diffraction/scattering method based on the Mie scattering theory. Specifically, the 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 used as the average particle size. The measurement sample can be prepared by weighing 100 mg of the inorganic filler and 10 g of methyl ethyl ketone into a vial and dispersing it by ultrasonic waves for 10 minutes. The measurement sample was measured using a laser diffraction type particle size distribution measuring device with blue and red light source wavelengths and a flow cell method to measure the volumetric particle size distribution of the inorganic filler, and the average particle size was calculated as the median diameter from the obtained particle size distribution. An example of a laser diffraction type particle size distribution measuring device is the "LA-960" manufactured by Horiba, Ltd.

(F) The specific surface area of the inorganic filler is not particularly limited, but is preferably 1 m ² /g or more, more preferably 10 m ² /g or more, even more preferably 20 m ² /g or more, and particularly preferably 40 m ² /g or more. (F) The upper limit of the specific surface area of the inorganic filler is not particularly limited, but is preferably 160 m ² /g or less, more preferably 130 m ² /g or less, and even more preferably 100 m ² /g or less. The specific surface area of the inorganic filler is obtained by adsorbing nitrogen gas to the sample surface 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.

It is preferable that the inorganic filler (F) is surface-treated with an appropriate surface treatment agent. By being surface-treated, the moisture resistance and dispersibility of the inorganic filler (F) can be improved. Examples of the surface treatment agent include vinyl-based silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxy-based silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; styryl-based silane coupling agents such as p-styryltrimethoxysilane; methacryl-based silane coupling agents such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; acrylic-based silane coupling agents such as 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, amino-based silane coupling agents such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-8-aminooctyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane; isocyanurate-based silane coupling agents such as tris-(trimethoxysilylpropyl)isocyanurate; ureido-based silane coupling agents such as 3-ureidopropyltrialkoxysilane; mercapto-based silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; isocyanate-based silane coupling agents such as 3-isocyanatepropyltriethoxysilane; and acid anhydride-based silane coupling agents such as 3-trimethoxysilylpropylsuccinic anhydride. The surface treatment agent may be used alone or in any combination of two or more types in any ratio.

(F) It is more preferable that the inorganic filler contains an inorganic filler that has been surface-treated with a surface treatment agent selected from a vinyl-based silane coupling agent and an amino-based silane coupling agent, and it is particularly preferable that the inorganic filler contains an inorganic filler that has been surface-treated with an amino-based silane coupling agent.

Commercially available surface treatment agents include, for example, Shin-Etsu Chemical Co., Ltd.'s "KBM-1003" and "KBE-1003" (vinyl silane coupling agents); "KBM-303", "KBM-402", "KBM-403", "KBE-402", and "KBE-403" (epoxy silane coupling agents); "KBM-1403" (styryl silane coupling agent); and "KBM-502". ", "KBM-503", "KBE-502", "KBE-503" (methacrylic silane coupling agent); "KBM-5103" (acrylic silane coupling agent); "KBM-602", "KBM-603", "KBM-903", "KBE-903", "KBE-9103P", "KBM-573", "KBM5783", "KBM-575" (amino silane coupling agent) coupling agent); "KBM-9659" (isocyanurate-based silane coupling agent); "KBE-585" (ureido-based silane coupling agent); "KBM-802", "KBM-803" (mercapto-based silane coupling agent); "KBE-9007N" (isocyanate-based silane coupling agent); "X-12-967C" (acid anhydride-based silane coupling agent); "KBM-13", "KBM-22", "KBM-103", "KBE-13", "KBE-22", "KBE-103", "KBM-3033", "KBE-3033", "KBM-3063", "KBE-3063", "KBE-3083", "KBM-3103C", "KBM-3066", "KBM-7103" (alkylalkoxysilane compound), etc.

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.

(F) The amount of carbon per unit surface area of the inorganic filler 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 a surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solids, the amount of carbon 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 the inorganic filler (F) in the resin composition forming the resin composition layer is, for example, preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of further improving developability, assuming that the non-volatile components in the resin composition are 100% by mass. The lower limit is, for example, 0% by mass or more, 0.1% by mass or more, and from the viewpoint of further suppressing the average linear thermal expansion coefficient, it is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more.

<(G) Other Additives>
The resin composition forming the resin composition layer may further contain any additive. Examples of such additives include thermosetting resins other than epoxy resins such as epoxy acrylate resins, urethane acrylate resins, urethane resins, cyanate resins, benzoxazine resins, unsaturated polyester resins, phenolic resins, melamine resins, and silicone resins; thermoplastic resins such as phenoxy resins, polyvinyl acetal resins, polyolefin resins, and polysulfone resins; organic fillers such as rubber particles; organometallic compounds such as organocopper compounds, organozinc compounds, and organocobalt compounds; polymerization inhibitors such as hydroquinone, catechol, pyrogallol, and phenothiazine; leveling agents such as silicone leveling agents and acrylic polymer leveling agents; thickeners such as bentone and montmorillonite; defoamers such as silicone defoamers, acrylic defoamers, fluorine defoamers, and vinyl resin defoamers; ultraviolet absorbers such as benzotriazole ultraviolet absorbers; and urea silanes. Examples of the suitable additives include adhesion improvers; adhesion imparting agents such as triazole-based adhesion imparting agents, tetrazole-based adhesion imparting agents, and triazine-based adhesion imparting agents; antioxidants such as hindered phenol-based antioxidants; fluorescent brightening agents such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, and red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide); dispersants such as phosphate ester-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants; and stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic acid anhydride-based stabilizers. The other additives (G) may be used alone or in any combination of two or more kinds at any ratio. The content of the other additives (G) can be appropriately determined by a person skilled in the art.

<(H) Organic Solvent>
The resin composition forming the resin composition layer may further contain an organic solvent (H) as an optional component. The varnish viscosity can be adjusted by including the component (H). Examples of the organic solvent (H) include ketones such as methyl ethyl ketone (MEK) and cyclohexanone, aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene, glycol ethers 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, esters such as ethyl acetate, butyl acetate, butyl cellosolve acetate, carbitol acetate, and ethyl diglycol acetate, aliphatic hydrocarbons such as octane and decane, and petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. These are used alone or in combination of two or more. The content of the organic solvent when used can be appropriately adjusted from the viewpoint of the coatability of the resin composition.

The content of (H) organic solvent is not particularly limited, but is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, assuming that all components in the resin composition are 100% by mass.

<Method of producing resin composition>
The resin composition that forms the resin composition layer can be produced by appropriately mixing the respective components and, if necessary, kneading or stirring the components using a kneading means such as a three-roll mill, a ball mill, a bead mill, or a sand mill, or a stirring means such as a super mixer, a planetary mixer, or a high-speed rotating mixer.

<Features of Resin Sheet with Support>
The support-attached resin sheet of the present invention is characterized in that it has superior core-forming properties and is capable of forming an optical waveguide with reduced optical transmission loss.

The resin sheet with a support of the present invention has superior core formability, and therefore, in one embodiment, can be characterized in that the minimum fine line formation width of the core that can be formed when the resin sheet with a support of the present invention is used and exposed from the support side can be smaller. Therefore, in one embodiment, the minimum fine line formation width when evaluated as in Test Example 1 below can be preferably 10 μm or less, more preferably 8 μm or less, even more preferably 6 μm or less, and particularly preferably 5 μm or less.

The supported resin sheet of the present invention has a superior core-forming property, and therefore, in one embodiment, it can have a feature that the resist defects at the core formed when the supported resin sheet of the present invention is used and exposed from the support side can be suppressed to a small amount. Therefore, in one embodiment, when the resist defects at the core are evaluated as in the following Test Example 2, the number of resist defects per ^mm2 can be preferably less than 5.

The resin sheet with a support of the present invention can be characterized in that it is possible to form an optical waveguide with reduced optical transmission loss. Therefore, in one embodiment, the optical transmission loss when tested as in Test Example 3 below can be preferably less than 2.0 dB/cm, more preferably less than 1.0 dB/cm, and particularly preferably less than 0.5 dB/cm.

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

<Optical Waveguide>
The resin sheet with a support of the present invention can be used to form a core of an optical waveguide in the manufacture of the optical waveguide. The core of the optical waveguide is configured to be capable of transmitting light and is covered with a clad layer. Hereinafter, an embodiment of the optical waveguide will be described with reference to the drawings.

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

The core 100 is provided in the clad layer 200. The core 100 is covered by the clad layer 200. Usually, the entire circumferential surface of the core 100 is covered by the clad layer 200. The core 100 and the clad layer 200 are in direct contact with each other without any other layer therebetween, and an interface 100I may be formed between the core 100 and the clad layer 200. Light (not shown) is transmitted through the core 100 from one end (the end on the input side) 100A of the core 100 to the other end (the end on the output 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 100 appropriately within the range in which light transmission is possible. A specific range for the width L of the core 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 100 corresponds to the line width (line) of the core 100 when viewed in the thickness direction.

It is desirable to set the spacing S of the cores 100 appropriately within the range in which light transmission is possible. A specific range for the spacing S of the cores 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 cores 100 corresponds to the spacing (space) of the cores as viewed in the thickness direction.

It is desirable to set the thickness T of the core 100 appropriately within the range in which light transmission is possible. A specific range of the thickness T of the core 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 greater than the thickness of the core 100. The specific thickness of the cladding layer 200 is preferably 5 μm or more, more preferably 7 μm or more, and particularly preferably 10 μm or more, and is preferably 40 μm or less, more preferably 30 μm or less, and particularly preferably 20 μm or less.

The optical waveguide 10 may include any element other than the core 100 and the clad layer 200, as necessary. For example, the optical waveguide 10 may include a substrate 300. In an optical waveguide 10 including a substrate 300, typically, a clad layer 200 is provided on the substrate 300, and a core 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 made 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 100 and the cladding layer 200. The protective layer may be provided, for example, 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, since the optical waveguide 10 can be formed using a resin composition with excellent core forming properties, the core 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 resin sheet with a support of the present invention. For example, the optical waveguide 10 is
(I) forming a first clad composition layer formed from a clad composition on a substrate;
(II) curing the first cladding composition layer to form an undercladding layer on the substrate;
(III) a step of laminating the supported resin sheet of the present invention onto a lower clad layer so that the resin composition layer is in contact with the lower clad layer to form a resin composition layer on the lower clad layer;
(IV) placing a mask on the support and subjecting a part of the resin composition layer to an exposure treatment through the mask and the support;
(V) removing the mask and the support;
(VI) subjecting the resin composition layer to a development treatment to form a resin composition pattern;
(VII) curing the resin composition pattern to form a core on the lower clad layer;
(VIII) forming a second clad composition layer on the lower clad layer so as to cover the core, the second clad composition layer being made of a clad composition;
(IX) curing the second clad composition layer to form an upper clad layer on the lower clad layer so as to cover the core;
It can be produced by a process comprising the steps of:

Figure 2 is a schematic cross-sectional view illustrating step (I) in one embodiment of the method for producing an optical waveguide. As shown in Figure 2, in one embodiment, the method for producing an optical waveguide includes the step (I) of forming a first cladding composition layer 210 made of a cladding composition on a substrate 300.

There is no particular limitation on the method for forming the first clad composition layer 210. For example, the first clad composition layer 210 may be formed by applying the clad composition onto the substrate 300. From the viewpoint of smooth application, a varnish-like clad composition may be prepared and the varnish-like clad 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 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 composition, the first cladding 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 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 clad composition layer 210 may be formed, for example, using a clad resin sheet including a support and a clad composition layer formed of a clad composition provided on the support. As a specific example, the first clad composition layer 210 can be formed on the substrate 300 by laminating the clad composition layer of the clad resin sheet onto the substrate 300. The lamination is performed by pressing the clad composition layer of the clad resin sheet onto 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 clad 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 clad composition layer 210 is formed using a clad resin sheet having a support, the support is usually peeled off from the clad resin sheet at an appropriate time prior to step (III).

In one embodiment, the method for manufacturing an optical waveguide includes, after step (I), a step (II) of curing the first cladding composition layer 210 to form the lower cladding layer 220 on the substrate 300. This step (II) may be, for example, curing the first cladding composition layer 210 by heat treating it. The conditions for the heat treatment may be selected according to the type and amount of the resin component in the cladding 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 performed in an inert atmosphere such as a nitrogen atmosphere.

The first clad composition layer 210 may be cured by exposure treatment. In one example, the specific range of the exposure dose is preferably 10 mJ/ ^cm2 or more, more preferably 50 mJ/ ^cm2 or more, particularly preferably 200 mJ/ ^cm2 or more, and preferably 10,000 mJ/ ^cm2 or less, more preferably 8,000 mJ/ ^cm2 or less, even more preferably 4,000 mJ/ ^cm2 or less, particularly preferably 1,000 mJ/ ^cm2 or less. The first clad 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) in one embodiment of the method for manufacturing an optical waveguide. By curing the first cladding composition layer 210 in step (II), a lower cladding layer 220 is formed on the substrate 300 as shown in Figure 3. The lower cladding layer 220 forms a part of the cladding layer 200.

Figure 4 is a schematic cross-sectional view for explaining step (III) in one embodiment of the method for producing an optical waveguide. In one embodiment, the method for producing an optical waveguide includes, after step (II), a step (III) of laminating the support-attached resin sheet of the present invention onto the lower clad layer 220 so that the resin composition layer is in contact with the lower clad layer 220 to form the resin composition layer 110 on the lower clad layer 220, as shown in Figure 4.

The resin composition layer 110 is formed using the resin sheet with a support of the present invention. The resin composition layer of the resin sheet with a support of the present invention is brought into contact with the lower clad layer 220 and laminated, thereby forming the resin composition layer 110 on the lower clad layer 220. The lamination of the resin sheet with a support of the present invention can be performed under the same conditions as those for laminating the resin sheet for clad.

Figure 5 is a schematic cross-sectional view for explaining step (IV) in one embodiment of the method for producing an optical waveguide. In one embodiment, the method for producing an optical waveguide includes, after step (III), a step (IV) of placing a mask 400 on the support 120 and subjecting a part of the resin composition layer 110 to an exposure treatment through the mask 400 and the support 120, as shown in Figure 5.

In step (IV), a latent image is formed in the resin composition layer 110 by performing an exposure process on a part of the resin composition layer 110. The exposure process in step (IV) is performed by placing a mask 400 having a light-transmitting portion 410 and a light-shielding portion 420 on the support 120, and irradiating the resin composition layer 110 with light P through the mask 400 and the support 120. 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. The exposed portion 111 and the non-exposed portion 112 corresponding to the light-transmitting cured portion 410 and the light-shielding portion 420 can be provided in the resin composition layer 110.

The light-transmitting portion 410 of the mask 400 is formed to have a planar shape corresponding to the pattern of the cores of the optical waveguide. 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 are no cores. Unless otherwise specified, the "planar shape" refers to the shape as viewed from the thickness direction. The light-transmitting portion 410 formed in a planar shape corresponding to the cores may be referred to as the "mask pattern" below.

As the light P used in the exposure treatment in step (IV), it is preferable to use an appropriate actinic ray according to the composition of the resin composition. 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 can be formed after curing in step (VIII). In one example, the specific range of the exposure dose in step (VI) 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.

In one embodiment, the method for manufacturing an optical waveguide includes, after step (IV), a step (V) of removing the mask 400 and the support 120.

In one embodiment, the method for producing an optical waveguide may include a step (X) of preheating the resin composition layer 110 after step (IV) or step (V) and before step (VI). Step (X) can further reduce the solubility of the exposed portion 111 in the developer. The heating in step (X) 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 (VI) in one embodiment of the method for producing an optical waveguide. In one embodiment, the method for producing an optical waveguide includes a step of forming a resin composition pattern 110' by subjecting the resin composition layer 110 to a development process (VI) after step (V). The development process allows the latent image formed in step (IV) to be developed. Since the resin composition layer 110 functions as a negative photosensitive resin composition, as shown in Figure 6, the exposed portion 111 (see Figure 5) of the resin composition layer 110 is not removed by the development process and remains as a resin composition pattern 110', while the non-exposed portion 112 (see Figure 5) of the resin composition layer 110 is removed. The exposed portion 111 of the resin composition layer 110 remaining after development becomes a resin composition pattern 110' having 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 carried out using a wet development method in which the resin composition layer 110 is brought into contact with a developer. An alkaline aqueous solution can be used as the developer. As the alkaline aqueous solution, an inorganic base aqueous solution or an organic base aqueous solution can be used.

Examples of inorganic base aqueous solutions include aqueous solutions of alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; aqueous solutions of alkali metal carbonates such as sodium carbonate; aqueous solutions of alkali metal bicarbonates such as sodium bicarbonate; aqueous solutions of alkali metal phosphates such as sodium phosphate and potassium phosphate; and aqueous solutions of alkali metal pyrophosphates such as sodium pyrophosphate and potassium pyrophosphate. Examples of organic base aqueous solutions include aqueous solutions of tetraalkylammonium hydroxide. Among these, aqueous solutions of alkali metal carbonates are preferred, and aqueous solutions of sodium carbonate are more preferred. The alkaline aqueous solutions may be used alone or in combination of two or more.

Additives such as surfactants and defoamers may be mixed into the developer as necessary to improve the developing action.

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 resin 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 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 non-exposed 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.

In one embodiment, the method for manufacturing an optical waveguide includes, after step (VI), a step (VII) of curing the resin composition pattern 110' to form the core 100 on the lower cladding layer 220. This step (VII) may be, for example, curing the resin composition pattern 110' by heat treating it. The conditions for the heat treatment may be selected according to the type and amount of the resin component in the cladding 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 performed in an inert atmosphere such as a nitrogen atmosphere.

Figure 7 is a schematic cross-sectional view for explaining step (VII) in one embodiment of the method for manufacturing an optical waveguide. By curing the resin composition pattern 110' in step (VII), a core 100 is formed on the lower cladding layer 220 as shown in Figure 7.

In one embodiment, the method for manufacturing an optical waveguide includes, after step (VII), a step (VIII) of forming a second cladding composition layer 230 made of a cladding composition on the lower cladding layer 220 so as to cover the core 100.

Figure 8 is a schematic cross-sectional view illustrating step (VIII) in one embodiment of the method for manufacturing an optical waveguide. The second cladding composition layer 230 is formed on the lower cladding layer 220 so as to cover the entire peripheral surface of the core 100 that is not in contact with the lower cladding layer 220.

There is no particular limitation on the method of forming the second clad composition layer 230. For example, the second clad composition layer 230 may be formed by applying the clad composition onto the lower clad layer 220 so as to cover the core 100. The application of the clad composition for forming the second clad composition layer 230 may be performed in the same manner as the application of the clad composition for forming the first clad composition layer 210. In addition, after application of the clad composition, the second clad composition layer 230 may be dried as necessary. The second clad composition layer 230 may be dried using the same method and conditions as those for drying the first clad composition layer 210.

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

In one embodiment, the method for manufacturing an optical waveguide includes, after step (VIII), a step (IX) of curing the second cladding composition layer 230 to form an upper cladding layer 240 on the lower cladding layer 220 so as to cover the core 100. The curing of the second cladding composition layer 230 in this step (IX) can be carried out in the same manner as the curing of the first cladding composition layer 210.

Figure 9 is a schematic cross-sectional view for explaining step (IX) in one embodiment of the method for manufacturing an optical waveguide. By curing the second cladding composition layer 230 in step (IX), an upper cladding layer 240 is formed on the lower cladding layer 220 so as to cover the core 100, as shown in Figure 9. The upper cladding layer 240 forms a part of the cladding layer 200, and the cladding layer 200 is formed from this upper cladding layer 240 and the lower cladding layer 220.

The first cladding composition layer 210 and the second cladding composition layer 230 described above are not particularly limited as long as they function as optical waveguides, but are preferably composition layers formed from a cladding composition containing (A) an epoxy resin, (B) a photopolymerizable resin containing a carboxyl group, (C) a photopolymerization initiator, and (F) an inorganic filler. It is preferable that the first cladding composition layer 210 and the second cladding composition layer 230 are composition layers made of the same composition.

The content of the epoxy resin (A) in the clad composition forming the first clad composition layer 210 and the second clad composition layer 230 is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, assuming that the non-volatile components of the clad composition are 100% by mass. The upper limit is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less.

The content of the (B) carboxyl group-containing photopolymerizable resin in the clad composition forming the first clad composition layer 210 and the second clad composition layer 230 is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, assuming that the non-volatile components of the clad composition are 100% by mass. The upper limit is preferably 80% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, and particularly preferably 40% by mass or less.

The content of the (C) photopolymerization initiator in the clad composition forming the first clad composition layer 210 and the second clad composition layer 230 is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, assuming that the non-volatile components of the clad composition are 100% by mass. The upper limit is preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 10% by mass or less.

The content of the inorganic filler (F) in the clad composition forming the first clad composition layer 210 and the second clad composition layer 230 is, for example, preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less, assuming that the non-volatile components in the clad composition are 100% by mass. The lower limit is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more.

The cladding composition forming the first cladding composition layer 210 and the second cladding composition layer 230 may contain optional components in addition to (A) epoxy resin, (B) photopolymerizable resin containing carboxyl groups, (C) photopolymerization initiator, and (F) inorganic filler. Examples of optional components include (D) reactive diluent, (E) photosensitizer, (G) other additives, and (H) organic solvent.

The content of the (D) reactive diluent in the clad composition forming the first clad composition layer 210 and the second clad composition layer 230 is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of further improving the photocurability, assuming that the non-volatile components of the clad composition are 100% by mass. The upper limit is preferably 60% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less.

The optical waveguide 10 comprises a cladding layer 200 consisting of a lower cladding layer 220 and an upper cladding layer 240, and a core 100 provided within the cladding layer 200. The method for manufacturing the optical waveguide 10 may further include any optional 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. 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 (XI) may be repeated to manufacture an optical waveguide having a multilayer structure on the substrate 300, in which cores and clad layers are alternately arranged in the thickness direction.

<Opto-electrical hybrid board>
The optical/electrical hybrid board includes the optical waveguide described above. 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). The optical waveguide is preferably capable of transmitting light with wavelengths of 1310 nm and 1550 nm or close thereto, and is preferably capable of transmitting light with wavelengths of, for example, 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. 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 core width is small. For example, it is preferable to form a core with a width of 10 μm or less, or 5 μm or less. In addition, an optical waveguide having such a small core width is preferable from the viewpoint of increasing the degree of freedom in package design when the optical waveguide is applied to a semiconductor package. With the optical waveguide according to the above-mentioned embodiment, it is possible to reduce the core width 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 be applicable to both single mode and multimode. Furthermore, it is desirable to reduce the minimum width of the core of these optical waveguides to increase the degree of freedom of the core line width. According to the optical waveguide of the above-mentioned embodiment, the resin composition has excellent core forming properties and can achieve high fine wiring formation capabilities, so the minimum width of the core can be reduced. Furthermore, according to the optical waveguide of the above-mentioned embodiment, both single mode and multimode optical waveguides can be obtained. The optical waveguide of the above-mentioned embodiment can be applied in a wide range. Since it can be applied in such a wide range and can suppress the transmission loss of light, the optical waveguide of the above-mentioned embodiment is suitable for application to an optical-electrical hybrid board.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following description, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified. Unless otherwise specified, the temperature conditions are room temperature (23°C), and unless otherwise specified, the pressure conditions are atmospheric pressure (1 atm). The weight average molecular weight is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography.

Synthesis Example 1: Carboxylic Acid-Modified Epoxy Acrylate Resin Having a Naphthol Aralkyl Skeleton
325 parts of an epoxy resin having a naphthol aralkyl skeleton ("ESN-475V" manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent 325) 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. This mixture was heated to 95 to 105°C, and 72 parts of acrylic acid were gradually added dropwise and reacted for 16 hours. This reaction product was cooled to 80 to 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 (non-volatile content 70%) with an acid value of 60 mgKOH/g of solid matter. The weight average molecular weight was 1000.

Synthesis Example 2: Carboxylic Acid-Modified Epoxy Acrylate Resin Having a Methylenedianaphthol Skeleton
162 parts of 1,1'-bis(2,7-diglycidyloxynaphthyl)methane (Dainippon Ink & Chemicals, Inc. "EXA-4700", epoxy equivalent 162) 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, heated and dissolved, and 0.46 parts of hydroquinone and 1 part of triphenylphosphine were added. This mixture was heated to 95-105°C, 72 parts of acrylic acid were gradually added dropwise, and reacted for 16 hours. This reaction product was cooled to 80-90°C, 80 parts of tetrahydrophthalic anhydride were added, reacted for 8 hours, and cooled. In this way, a resin solution (70% non-volatile content) with an acid value of 90 mgKOH/g of solid matter was obtained. The weight average molecular weight was 2500.

<Example 1: Production of Support-Attached Resin Sheet 1>
25 parts of the carboxylic acid-modified epoxy acrylate resin (containing naphthol aralkyl skeleton, non-volatile content rate 70%) obtained in Synthesis Example 1, 10 parts of naphthol aralkyl type epoxy resin (manufactured by Nippon Steel Chemical & Material Co., Ltd., "ESN-475V", epoxy equivalent 330 g / eq.), 1.3 parts of an α-aminoketone-based photopolymerization initiator (manufactured by IGM Co., Ltd., "Omnipol 910", polyethylene glycol di(β-4-[4-(2-dimethylamino-2-benzyl)butanoylphenyl]piperazine)propionate), 10 parts of a reactive diluent (manufactured by Nippon Kayaku Co., Ltd., 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.

A polyethylene terephthalate film (Unitika's "S-25", thickness 25 μm) was uniformly coated with a release agent (Lintec's "AL-5") to a thickness of 1 μm using a die coater to prepare a support. The haze of the support prepared in accordance with JIS K6714 was measured to be 6%. The arithmetic mean roughness (Ra) of the side of the support on which the varnish-like resin composition was applied was measured to be 10 nm using a non-contact interference microscope (WYKO Bruker AXS). The total light transmittance of the support was measured in accordance with JIS K 7361-1 to be 87%.

A varnish-like resin composition was uniformly applied to the release agent-coated surface of the prepared support using a die coater so that the thickness of the resin composition layer after drying would be 10 μm, and the resin composition layer was formed by drying for 6 minutes at 80°C to 110°C (maximum temperature 110°C). Next, a cover film (biaxially oriented polypropylene film, Oji F-Tex's "MA-411") was placed on the surface of the resin composition layer and laminated at 80°C to produce a resin sheet with a support having a three-layer structure of support/resin composition layer/cover film.

Example 2: Production of Support-Attached Resin Sheet 2
A resin sheet with a support was produced in the same manner as in Example 1, except that 25 parts of the carboxylic acid-modified epoxy acrylate resin (containing a methylenediinaphthol skeleton, non-volatile content of 70%) obtained in Synthesis Example 2 was used in place of 25 parts of the carboxylic acid-modified epoxy acrylate resin (containing a naphthol aralkyl skeleton, non-volatile content of 70%) obtained in Synthesis Example 1.

Example 3: Production of resin sheet 3 with support
A resin sheet with a support was produced in the same manner as in Example 1, except that 25 parts of a carboxylic acid-modified epoxy acrylate resin ("CCR-1373H" manufactured by Nippon Kayaku Co., Ltd., containing a cresol novolac skeleton, acid value 99 mgKOH/g, non-volatile content 60%, solvent PGMEA, molecular weight 2800) was used in place of 25 parts of the carboxylic acid-modified epoxy acrylate resin (containing a naphthol aralkyl skeleton, non-volatile content 70%) obtained in Synthesis Example 1.

Example 4: Production of Support-Attached Resin Sheet 4
A resin sheet with a support was produced in the same manner as in Example 1, except that 25 parts of a carboxylic acid-modified epoxy acrylate resin ("CCR-1171H" manufactured by Nippon Kayaku Co., Ltd., containing a cresol novolac skeleton, acid value 99 mgKOH/g, non-volatile content 60%, solvent PGMEA, molecular weight 7500) was used in place of 25 parts of the carboxylic acid-modified epoxy acrylate resin (containing a naphthol aralkyl skeleton, non-volatile content 70%) obtained in Synthesis Example 1.

Example 5: Production of Support-Attached Resin Sheet 5
A resin sheet with a support was produced in the same manner as in Example 1, except that 25 parts of a carboxylic acid-modified epoxy acrylate resin ("ZCR-8001H" manufactured by Nippon Kayaku Co., Ltd., containing a biphenyl skeleton, acid value 109 mgKOH/g, non-volatile content 60%, solvent PGMEA, molecular weight 3700) was used in place of 25 parts of the carboxylic acid-modified epoxy acrylate resin (containing a naphthol aralkyl skeleton, non-volatile content 70%) obtained in Synthesis Example 1.

<Example 6: Production of Support-Attached Resin Sheet 6>
Further, a resin sheet with a support was produced in the same manner as in Example 1, except that 0.3 parts of an α-aminoketone-based photopolymerization initiator (IGM's "Omnirad 379EG", 2-(dimethylamino)-2-(4-methylphenylmethyl)-1-(4-morpholinophenyl)butan-1-one, molecular weight 380.5) was used.

Example 7: Production of Support-Attached Resin Sheet 7
Further, a resin sheet with a support was produced in the same manner as in Example 1, except that 0.01 part of an oxime ester-based photopolymerization initiator (BASF Corporation's "Irgacure OXE-02", [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]ethylideneamino]acetate, molecular weight 412.5) was used.

Example 8: Production of resin sheet 8 with support
Further, a resin sheet with a support was produced in the same manner as in Example 1, except that 2.6 parts of an acylphosphine oxide-based photopolymerization initiator (IGM's "Omnipol TP", polyoxyethylene glycerin ether tris[phenyl(2,4,6-trimethylbenzoyl)phosphinate], molecular weight 900 or more) was used.

<Example 9: Production of Support-Attached Resin Sheet 9>
Further, a resin sheet with a support was produced in the same manner as in Example 1, except that 0.1 parts of thioxanthones (IGM's "Omnipol TX", polybutylene glycol bis(9-oxo-9H-thioxanthenyloxy)acetate, molecular weight 790) were used.

Example 10: Production of resin sheet 10 with support
Further, a resin sheet with a support was produced in the same manner as in Example 1, except that 0.3 part of benzophenone ("EAB" manufactured by Tokyo Chemical Industry Co., Ltd., 4,4'-bis(diethylamino)benzophenone, molecular weight 343) was used.

Example 11: Production of Support-Attached Resin Sheet 11
Further, a resin sheet with a support was produced in the same manner as in Example 1, except that 10 parts of spherical silica ("Y50SZ-AM1" manufactured by Admatechs Co., Ltd., specific surface area ⁶⁰ m2/g, average particle size 0.05 μm, solid content 50%) that had been surface-treated with an amino-based silane coupling agent was used.

Example 12: Production of resin sheet 12 with support
A resin sheet with a support was produced in the same manner as in Example 1, except that a polyethylene terephthalate film ("PET-12" manufactured by Unitika Ltd., thickness 12 μm) was used as the support instead of a support formed by applying a release agent to a polyethylene terephthalate film ("S-25" manufactured by Unitika Ltd., thickness 25 μm). As in Example 1, the haze of the support was measured to be 3%, the arithmetic average roughness (Ra) was measured to be 30 nm, and the total light transmittance was measured to be 88%.

<Example 13: Production of Support-Attached Resin Sheet 13>
A resin sheet with a support was produced in the same manner as in Example 1, except that a polyethylene terephthalate film ("S-38" manufactured by Unitika Ltd., thickness 38 μm) was used as the support instead of a support formed by applying a release agent to a polyethylene terephthalate film ("S-25" manufactured by Unitika Ltd., thickness 25 μm). As in Example 1, the haze of the support was measured to be 3%, the arithmetic average roughness (Ra) was measured to be 35 nm, and the total light transmittance was measured to be 88%.

<Example 14: Production of Support-Attached Resin Sheet 14>
A resin sheet with a support was produced in the same manner as in Example 1, except that a polyethylene terephthalate film (Toray Industries, Inc., "Lumirror FB-40", thickness 16 μm) was used as the support instead of a support formed by applying a release agent to a polyethylene terephthalate film (Unitika Ltd., "S-25", thickness 25 μm). As in Example 1, the haze of the support was measured to be 1%, the arithmetic average roughness (Ra) was measured to be 8 nm, and the total light transmittance was measured to be 89%.

<Example 15: Production of Support-Attached Resin Sheet 15>
A resin sheet with a support was produced in the same manner as in Example 1, except that a polyethylene terephthalate film ("QS63" manufactured by Toray Industries, Inc., thickness 25 μm) was used as the support instead of a support in which a release agent was applied to a polyethylene terephthalate film ("S-25" manufactured by Unitika Ltd., thickness 25 μm). As in Example 1, the haze of the support was measured to be 0.5%, the arithmetic average roughness (Ra) was measured to be 7 nm, and the total light transmittance was measured to be 90%.

<Comparative Example 1: Production of Support-Attached Resin Sheet 16>
A resin sheet with a support was produced in the same manner as in Example 1, except that a filler-mixed polyethylene terephthalate film (Unitika Ltd.'s "PTH-25", thickness 25 μm) was used as the support instead of a support made of a polyethylene terephthalate film (Unitika Ltd.'s "S-25", thickness 25 μm) coated with a release agent. As in Example 1, the haze of the support was measured to be 25%, the arithmetic average roughness (Ra) was measured to be 260 nm, and the total light transmittance was measured to be 85%.

<Comparative Example 2: Production of Support-Attached Resin Sheet 17>
A resin sheet with a support was produced in the same manner as in Example 1, except that a sandblasted polyethylene terephthalate film ("T60" manufactured by Toray Industries, Inc., thickness 25 μm) was used as the support instead of a support made of a polyethylene terephthalate film ("S-25" manufactured by Unitika Ltd., thickness 25 μm) coated with a release agent. As in Example 1, the haze of the support was measured to be 70%, the arithmetic average roughness (Ra) was measured to be 300 nm, and the total light transmittance was measured to be 86%.

<Comparative Example 3: Production of Support-Attached Resin Sheet 18>
A resin sheet with a support was produced in the same manner as in Example 1, except that a roughened polyethylene terephthalate film ("S-25" manufactured by Unitika Ltd., thickness 25 μm) was used as the support instead of a support in which a release agent was applied to a polyethylene terephthalate film ("S-25" manufactured by Unitika Ltd., thickness 25 μm). As in Example 1, the haze of the support was measured to be 60%, the arithmetic average roughness (Ra) was measured to be 560 nm, and the total light transmittance was measured to be 87%.

<Production Example 1: Production of clad resin sheet>
25 parts of the carboxylic acid-modified epoxy acrylate resin obtained in Synthesis Example 1 (containing a bisnaphtholmethane skeleton, non-volatile content of 70%), 10 parts of naphthol aralkyl-type epoxy resin ("ESN-475V" manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent 330 g / eq.), 1.3 parts of an α-aminoketone-based photopolymerization initiator ("Omnipol 910" manufactured by IGM Co., Ltd., polyethylene glycol di(β-4-[4-(2-dimethylamino-2-benzyl)butanoylphenyl]piperazine)propionate), 10 parts of a reactive diluent ("DPHA" manufactured by Nippon Kayaku Co., Ltd., dipentaerythritol hexaacrylate), and 10 parts of spherical silica surface-treated with an amino-based silane coupling agent ("180 nm SX-C1" manufactured by Admatechs Co., Ltd., specific surface area 20 m ² A varnish-like clad composition was prepared by mixing 30 parts of cellulose acetate stearate (0.1/g, average particle size 0.2 μm, solid content 100%) and 10 parts of methyl ethyl ketone using a high-speed rotating mixer.

A polyethylene terephthalate film (Unitika's "S-25", thickness 25 μm) was uniformly coated with a release agent (Lintec's "AL-5") to a thickness of 1 μm using a die coater to prepare a support.

The varnish-like clad composition was uniformly applied to the release agent-coated surface of the prepared support using a die coater so that the resin composition layer would be 10 μm thick after drying, and then dried for 6 minutes at 80°C to 110°C (maximum temperature 110°C) to form a clad composition layer. Next, a cover film (biaxially oriented polypropylene film, Oji F-Tex's "MA-411") was placed on the surface of the resin composition layer and laminated at 80°C to produce a clad resin sheet with a three-layer structure of support/resin composition layer/cover film.

<Test Example 1: Evaluation of Minimum Thin Line Formation Width of Core>
A copper layer of a glass epoxy substrate (copper-clad laminate) having a copper layer of 18 μm in thickness was roughened with a surface treatment agent (CZ8100, manufactured by MEC Co., Ltd.) containing an organic acid to prepare a substrate. A resin sheet for cladding having a composition layer for cladding of 10 μm in thickness manufactured in Manufacturing Example 1 was laminated on the prepared substrate at 80° C. so that the composition layer for cladding was in contact with the substrate, forming a first composition layer for cladding on the substrate. Then, using a projection exposure device ("UFX-2240" manufactured by Ushio Inc.), ultraviolet light exposure was performed 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 development at a spray pressure of 0.2 MPa on the entire surface of the composition layer for first cladding. 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 the resin sheets 1 to 14 with a support and having a resin composition layer with a thickness of 10 μm produced in the examples and comparative examples. The resin sheet with a support was placed on the lower clad layer so that the resin composition layer of the resin sheet with a support was in contact with the lower clad layer, and laminated using a vacuum laminator ("VP160" manufactured by Nikko Materials Co., Ltd.) to form a 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 resin composition layer 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. Exposure was performed using a quartz glass mask having a mask pattern that draws straight lines with L/S (line/space) 10 μm/10 μm, 9 μm/9 μm, 8 μm/8 μm, 7 μm/7 μm, 6 μm/6 μm, 5 μm/5 μm, 4 μm/4 μm, and 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 resin composition layer was spray-developed with a 1% by weight 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 substrate 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 core (cured product of the resin composition pattern).

The obtained samples were observed under a scanning electron microscope (SEM) (magnification 2000x) and the minimum thin line formation width (the width of the smallest core that was formed) was measured.

<Test Example 2: Evaluation of resist defects in core>
The core of the sample obtained in Test Example 1 was observed using a scanning electron microscope (SEM), and the number of resist defects per ¹ mm2 of the sample was evaluated based on the following evaluation criteria.
"Good": Less than 5 resist defects "Poor": 5 or more resist defects

<Test Example 3: Measurement of optical transmission loss>
The cover film was peeled off from the clad resin sheet having a clad composition layer with a thickness of 10 μm produced in Production Example 1. The resin sheet was placed on a 4-inch silicon wafer so that the clad 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 first clad composition layer.

The first clad composition layer of the obtained 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 first clad composition layer. A lower clad layer was formed by curing the first clad composition layer, and an intermediate laminate II comprising a silicon wafer and a lower clad layer was obtained.

The cover film was peeled off from the resin sheets 1 to 14 with a support and having a resin composition layer with a thickness of 10 μm produced in the examples and comparative examples. The resin sheet with a support was placed on the surface of the lower clad layer of the intermediate laminate II so that the 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 compression temperature of 100°C, a compression pressure of 0.7 MPa, and a pressure time of 30 seconds. An intermediate laminate III was obtained, which had a silicon wafer, a lower clad layer, and a resin composition layer in this order.

The 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 would result in 8 gloss remaining steps on a 41-step tablet. The exposure was performed using a quartz glass mask having a mask pattern capable of drawing multiple straight lines with a length of 1 cm at L/S (line/space) 5 μm/100 μm, a mask pattern capable of drawing multiple straight lines with a length of 2 cm at L/S (line/space) 5 μm/100 μm, and a mask pattern capable of drawing multiple 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, and the space corresponds to the distance between the cores. After exposure, the substrate was left to stand at room temperature for 30 minutes, and then the support was peeled off. A 1% by mass aqueous solution of sodium carbonate at 30° C. was used as a developer on the entire surface of the resin composition layer, and spray development was performed for 1 minute at a spray pressure of 0.2 MPa to form a resin composition pattern. After spray development, ultraviolet irradiation was performed at 2 J/cm ^2. The intermediate laminate III was then placed in a clean oven, heated from room temperature to 170° C., and after reaching 170° C., a heat treatment was performed for 60 minutes in a nitrogen atmosphere to harden the resin composition pattern.

The resin composition pattern was cured to form a core, yielding intermediate laminate IV, which had a silicon wafer, a lower clad layer, and a core in that order.

The cover film was peeled off from the clad resin sheet having a clad composition layer with a thickness of 10 μm produced in Production Example 1. The clad resin sheet was placed on the core of the intermediate laminate IV so that the clad composition layer and the core were in contact, 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 bonding temperature of 100°C, a bonding pressure of 0.7 MPa, and a pressurization time of 30 seconds. The support was then peeled off to obtain an intermediate laminate V having a silicon wafer, a lower clad layer, a core, and a second clad composition layer in this order.

The second clad 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 was irradiated 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 second clad composition layer. An upper clad layer was formed by the curing of the second clad composition layer, and a sample laminate including a silicon wafer, a lower clad layer, a core, and an upper clad layer was obtained.

In the obtained sample laminate, the combination of the lower cladding layer and the upper cladding layer constitutes the cladding layer. An optical waveguide was obtained that includes a cladding layer and a core in the cladding layer. In addition, in this sample laminate, the core has linear patterns of lengths of 1 cm, 2 cm, and 3 cm corresponding to the mask pattern of the quartz glass mask, and the width (line width) and interval (space) of the cores included in these patterns match the width (line width) and interval (space) of the mask pattern.

From the obtained sample laminate, the core and the surrounding cladding layer were cut out at the portion where the core was formed to obtain a test substrate equipped with an optical transmission path.

The obtained test substrate was placed on a vibration-proof table covered with a blackout curtain. A light-collecting module (numerical aperture 0.18) was connected to one end (input 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 (input fiber). Another light-collecting module (numerical aperture 0.18) was connected to the other end (output 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 (output fiber). Through the above operations, an optical system was obtained in which light emitted from the light source passes through the optical fiber (input fiber), the light-collecting module, the optical waveguide, the light-collecting module, and the optical fiber (output fiber) in this order, and then enters the light receiver. Hereinafter, this optical system may be referred to as the 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 in 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.

The loss of the optical waveguide was measured for an optical waveguide with a length of 1 cm, an optical waveguide with a length of 2 cm, and an optical waveguide with a length of 3 cm. The measurement results were then 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 for these three points was calculated using the least squares method, and the optical transmission loss (dB/cm) per unit distance of the optical waveguide was calculated as the slope of the approximation line, and evaluated based on the following evaluation 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 "X": Optical transmission loss 2.0 dB/cm or more

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. If only one circular edge of the light was observed, it was judged as single mode "S". If multiple edges were observed, it was judged as multimode "M".

The amounts of raw materials used in the manufacture of the resin sheets with supports in the examples and comparative examples, the measurement results of the supports, and the evaluation results of the test examples are summarized in Table 1 below.

The results shown in Table 1 above show that by using a resin sheet with a support having a support with a haze of 10% or less, or a support with an arithmetic mean roughness (Ra) of the contact surface of the support with the resin composition layer of 50 nm or less, it is possible to form an optical waveguide with better core formation properties and reduced optical transmission loss.

REFERENCE SIGNS LIST 10 Optical waveguide 100 Core 110 Resin composition layer 110' Resin composition pattern 111 Exposed portion 112 Non-exposed portion 120 Support 200 Cladding layer 210 First cladding composition layer 220 Lower cladding layer 230 Second cladding composition layer 240 Upper cladding layer 300 Substrate 400 Mask 410 Light-transmitting portion 420 Light-shielding portion

Claims (16)

A resin sheet with a support, the resin sheet having a support and a resin composition layer provided on the support,
the resin composition layer is a resin composition layer formed of a resin composition including (A) an epoxy resin, (B) a photopolymerizable resin containing a carboxyl group , ( C) a photopolymerization initiator , and (D) a reactive diluent ;
a mass ratio of the photopolymerizable resin (B) containing a carboxyl group to the reactive diluent (D) in the resin composition forming the resin composition layer (content of the photopolymerizable resin (B) containing a carboxyl group/content of the reactive diluent (D)) is 0.1 to 3;
A resin sheet with a support for forming a core of an optical waveguide, which satisfies both conditions (1) and (2).
Condition (1): The haze of the support measured in accordance with JIS K6714 is 10% or less.
Condition (2): The arithmetic mean roughness (Ra) of the surface of the support that comes into contact with the resin composition layer is 50 nm or less. The support-attached resin sheet according to claim 1 , wherein the support is a polyethylene terephthalate film. The support-attached resin sheet according to claim 1, wherein the support has a thickness in the range of 10 μm to 50 μm. The support-attached resin sheet according to claim 1, wherein the resin composition layer has a thickness in the range of 3 μm to 30 μm. The resin sheet with a support according to claim 1 , wherein the epoxy resin (A) contains an epoxy resin having a naphthol aralkyl skeleton. 2. The supported resin sheet according to claim 1, wherein the (B) photopolymerizable resin containing a carboxyl group comprises a photopolymerizable resin containing an ethylenically unsaturated group and a carboxyl group. The resin sheet with a support according to claim 1 , wherein the (B) photopolymerizable resin containing a carboxyl group includes a photopolymerizable resin having a naphthol aralkyl skeleton. The resin sheet with a support according to claim 1 , wherein the (B) photopolymerizable resin containing a carboxyl group contains a carboxylic acid-modified epoxy (meth)acrylate resin. 2. The resin sheet with a support according to claim 1, wherein the weight average molecular weight (Mw) of the photopolymerizable resin containing a carboxyl group (B) is 18,000 or less . The support-attached resin sheet according to claim 1 , wherein the molecular weight of the photopolymerization initiator (C) is 400 or more. The resin sheet with a support according to claim 1, wherein the (C) photopolymerization initiator contains at least one photopolymerization initiator selected from an α-aminoketone-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, and an oxime ester-based photopolymerization initiator. 2. The resin sheet with a support according to claim 1 , wherein a mass ratio of the epoxy resin (A) to the photopolymerizable resin (B) containing a carboxyl group in the resin composition forming the resin composition layer ( content of the epoxy resin (A) / content of the photopolymerizable resin (B) containing a carboxyl group ) is 0.1 to 3. 2. The resin sheet with a support according to claim 1, wherein a mass ratio of the photopolymerizable resin containing a carboxyl group (B) to the photopolymerization initiator (C) in the resin composition forming the resin composition layer ( content of the photopolymerizable resin containing a carboxyl group (B) / content of the photopolymerization initiator (C)) is 1 to 50. The support-attached resin sheet according to claim 1 , wherein the reactive diluent (D) contains a di- or higher functional (meth)acrylate compound not containing a carboxyl group. The support-attached resin sheet according to claim 1 , wherein the molecular weight of the reactive diluent (D) is 1,000 or less. (III) a step of laminating the supported resin sheet according to any one of claims 1 to 15 onto a lower clad layer so that a resin composition layer of the supported resin sheet is in contact with the lower clad layer, thereby forming a resin composition layer of the supported resin sheet on the lower clad layer;
(IV) placing a mask on the support of the supported resin sheet and exposing a part of the resin composition layer formed on the lower clad layer through the mask and the support;
(V) removing the mask and the support of the support-attached resin sheet ;
(VI) a step of subjecting the resin composition layer formed on the lower clad layer to a development treatment to form a resin composition pattern;
(VII) curing the resin composition pattern to form a core of an optical waveguide on the lower clad layer;
A method for manufacturing an optical waveguide comprising the steps of:

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