Photosensitive resin composition, transfer film, resin pattern, and cured film pattern

Abstract

To provide a transfer film which enables lithography, and a photosensitive resin composition enabling acquisition of a cured film pattern excellent in low dielectric property, heat resistance, flame retardancy, and insulating property.SOLUTION: A photosensitive resin composition is provided, including (A) an alkali-soluble resin, (B) a polymerizable compound having an ethylenically unsaturated double bond, (C) a photopolymerization initiator, (D) polymer fine particles that is composed of a polymer having a dielectric constant at a frequency of 10 GHz of 2.8 or less and has an average particle diameter of 5 μm or less and a maximum particle diameter of 20 μm or less, and (E) a flame retardant that contains phosphorus or bromine and exhibits a solid property at 30°C, wherein the photosensitive resin composition has a haze of 15% or less when the photosensitive resin composition is coated onto a support thereby forming a transfer film having a thickness of 25 μm, and then the transfer film is laminated onto a glass substrate having a thickness of 1.1 mm at a roll temperature of 95°C by a hot roll laminator.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin composition, a transfer film, a resin pattern, and a cured film pattern, and more particularly to a transfer film, a resin pattern, and a cured film pattern suitable for a module for high-speed wireless communication. [Background technology]

[0002] In recent years, film-type printed circuit boards called flexible printed circuit boards (hereinafter referred to as "FPCs") have become popular. These FPCs have a structure in which a coverlay made of polyimide film and the like is provided on a wired flexible copper clad laminate (FCCL), and are mainly used in devices such as mobile phones, smartphones, tablet devices, notebook computers, and digital cameras. FPCs maintain their functionality even when bent, making them an essential material for making devices smaller and lighter. In particular, electronic devices such as smartphones and tablet devices have become smaller and lighter in recent years, and the use of FPCs in such products contributes to reducing the size and weight of the electronic devices, as well as reducing product costs and simplifying designs.

[0003] FPCs are applied with a coverlay, which is a layer of insulating material used to fully or partially cover the conductor patterns on the outer surface of the printed circuit board. The most basic coverlay is a film coverlay made of a reliable non-photosensitive punched material, but photosensitive coverlays are required for fine processing by lithography to miniaturize FPCs and simplify the manufacturing process. In addition, materials that are compatible with alkaline aqueous solution development are desired due to environmental considerations.

[0004] On the other hand, with the recent high performance of mobile terminal devices and the progress of network technology, the amount of information used in the world has increased explosively, and the electric signals used in information communication have shifted to high frequencies that enable high-speed and large-capacity transmission. Therefore, there is an increasing demand for low-dielectric materials (e.g., materials with low dielectric constant and low dielectric dissipation factor) that can reduce the transmission loss that is an issue when transmitting or processing high-frequency signals in the printed wiring boards used, and the coverlay in FPC is no exception. In this background, in addition to performance such as insulation reliability, heat resistance, and flame retardancy as a protective film, a coverlay with photosensitivity and low dielectric constant and dielectric dissipation factor in the high frequency band is required. In particular, regarding photodevelopability, polar groups are introduced into the composition to make it soluble in the developer, but since the introduction of polar groups is a composition design that is the exact opposite of low dielectric, high technology is required to achieve both performances.

[0005] Patent Documents 1 and 2 disclose photosensitive resin compositions as low dielectric materials. Patent Document 1 does not include any description of the insulating properties and flame retardancy required for coverlays, and the dielectric loss tangent value needs to be improved as a low dielectric material for recent high frequencies. Patent Document 2 includes a description of insulating properties, heat resistance, and flame retardancy, but as a low dielectric material, the dielectric constant and dielectric loss tangent values ​​do not meet the recent required levels. Furthermore, Patent Document 3 discloses a resin composition that exhibits a good dielectric tangent, but it is not possible to apply lithography to it. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-166472 A [Patent Document 2] Patent No. 6502733 [Patent Document 3] Patent No. 6546993 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, there is still room for improvement in the techniques described in Patent Documents 1 to 3. Therefore, the problem to be solved by the present invention is to provide a photosensitive resin composition capable of obtaining a transfer film capable of lithography, and a cured film pattern having excellent low dielectric constant, heat resistance, flame retardancy, and insulating properties. [Means for solving the problem]

[0008] As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by a photosensitive resin composition that contains an alkali-soluble polymer, polymer particles having a specific particle size, and a flame retardant, and that has a haze of 15% or less when the photosensitive resin composition is laminated on a glass substrate under specific conditions. Examples of embodiments of the present invention are listed below. [1] Ingredients include: (A) an alkali-soluble resin, (B) a polymerizable compound having an ethylenically unsaturated double bond, (C) a photopolymerization initiator, (D) polymer microparticles having an average particle size of 5 μm or less and a maximum particle size of 20 μm or less, the polymer microparticles being composed of a polymer with a dielectric constant of 2.8 or less at a frequency of 10 GHz; and (E) Flame retardants that contain phosphorus or bromine and are solid at 30°C; A photosensitive resin composition comprising: The photosensitive resin composition is characterized in that when the photosensitive resin composition is applied onto a support to form a transfer film having a thickness of 25 μm, and then laminated onto a glass substrate having a thickness of 1.1 mm at a roll temperature of 95° C. using a hot roll laminator, the haze is 15% or less. [2] The photosensitive resin composition according to [1], wherein the component (D) is polyphenylene ether fine particles having an average particle size of 2 μm or less. [3] The photosensitive resin composition according to [1] or [2], further comprising (F) a heterocyclic compound. [4] The photosensitive resin composition according to any one of [1] to [3], comprising, as the component (B), at least one kind of compound (b) having a molecular weight of 250 or less. [5] The photosensitive resin composition according to any one of [1] to [4], further comprising (G) a blocked isocyanate compound. [6] A transfer film comprising: a support; and a photosensitive resin layer formed on the support, the photosensitive resin layer being made of the photosensitive resin composition according to any one of [1] to [5]. [7] The transfer film according to [6], which is laminated on a substrate having wiring and used as a wiring protective film or insulating film. [8] A resin pattern formed from an exposed and developed product of the transfer film according to [6] or [7]. [9] A cured film pattern formed from a cured product of the resin pattern described in [8]. Effect of the Invention

[0009] According to the present invention, it is possible to provide a photosensitive resin composition that can provide a transfer film that can be patterned by exposure and development, and a cured film pattern that is excellent in low dielectric, heat resistance, flame retardancy, and insulation properties. The photosensitive resin composition of the present invention can be preferably used as a protective film or insulating film for wiring as a low dielectric material for high frequencies. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a detailed description will be given of an embodiment of the present invention (hereinafter, abbreviated as "embodiment"). Note that the present invention is not limited to the following embodiment, and can be modified in various ways within the scope of the present invention.

[0011] <(A) Alkali-soluble polymer> The alkali-soluble resin (A) according to the present embodiment is a polymer containing an acidic group, and the acidic group is preferably a carboxyl group. Examples of the alkali-soluble resin include acrylic copolymers such as (meth)acrylic acid, (meth)acrylic acid esters, (meth)acrylonitrile, and (meth)acrylamide, acid-modified epoxy resins, and polyimide precursors. Among these copolymers, it is preferable to include an acrylic copolymer and / or an acid-modified epoxy resin from the viewpoints of low dielectric constant, developability, and insulating properties.

[0012] Acrylic copolymer It is preferable to use a copolymer obtained by copolymerizing at least one monomer containing an acidic group in the molecule with at least one other monomer not containing an acidic group, which will be described later. Examples of monomers containing an acidic group include (meth)acrylic acid, fumaric acid, cinnamic acid, crotonic acid, itaconic acid, maleic anhydride, and maleic acid ester. Examples of monomers that do not have an acidic group include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylonitrile, vinyl alcohol esters such as vinyl acetate, (meth)acrylic acid aromatic esters such as benzyl (meth)acrylate, styrene and its polymerizable derivatives, etc. Among these copolymers, from the viewpoint of developability and dielectric properties, a copolymer containing a constitutional unit derived from (meth)acrylic acid and a constitutional unit derived from a (meth)acrylic acid aromatic ester or styrene and its derivatives is more preferred. From the viewpoint of achieving both developability and dielectric properties, it is more preferable that the toner contains 10% by mass or more and 30% by mass or less of a structure derived from (meth)acrylic acid and 50% by mass or more and 80% by mass or less of a structure derived from styrene or a derivative thereof.

[0013] Acid-modified epoxy resin Examples of acid-modified epoxy resins include those obtained by reacting an epoxy resin with an unsaturated carboxylic acid compound and then reacting with a polybasic acid anhydride. Examples of commercially available acid-modified epoxy (meth)acrylates containing a biphenyl skeleton include ZCR-1569H, ZCR-1761H, ZCR-1797H, and ZCR-1798H (manufactured by Nippon Kayaku Co., Ltd.), and examples of commercially available acid-modified epoxy (meth)acrylates containing a naphthalene skeleton include ZCR-1809H, ZCR-1835H, and ZCR-1834H (manufactured by Nippon Kayaku Co., Ltd.).

[0014] The weight average molecular weight of the (A) alkali-soluble resin is not limited, but is preferably 2,000 to 100,000, more preferably 4,000 to 60,000. If the weight average molecular weight of the (A) alkali-soluble polymer is 2,000 or more, the properties of the unexposed film, such as tackiness, edge fuse property, cut chip property, etc., when the film is made into a transfer film, and the mechanical properties of the cured film are good, and if the weight average molecular weight is 100,000 or less, the developability is good. From the viewpoint of developability, the weight average molecular weight is more preferably 60,000 or less. Here, tackiness indicates the adhesion when the photosensitive resin composition is made into a transfer film, and if the tackiness is too large, the cover film and the support will not peel properly, and if the tackiness is too weak, problems such as the cover film not being attached and the support peeling off in an unintended process will occur. Edge fuse property is a phenomenon in which the photosensitive resin composition layer protrudes from the end face of the roll when the transfer film is wound into a roll. Cut chipping is a phenomenon in which chips fly off when an unexposed film is cut with a cutter. If the scattered chips adhere to the top surface of the transfer film, they will be transferred to the mask in the subsequent exposure process, causing defects.

[0015] In this specification, the weight average molecular weight is measured using a gel permeation chromatography (GPC) manufactured by JASCO Corp. under the following conditions. The weight average molecular weight thus obtained is a polystyrene-equivalent value. Pump: Gulliver, PU-1580 type Column: Showa Denko K.K. Shodex (registered trademark) (KF-807, KF-806M, KF-806M, KF-802.5), 4 columns in series, Mobile phase solvent: tetrahydrofuran Calibration curve: Calibration curve determined using a polystyrene standard sample {Calibration curve using a polystyrene standard sample (Shodex STANDARD SM-105 manufactured by Showa Denko K.K.)}

[0016] The acid value (mgKOH / g) of the (A) alkali-soluble resin is not limited, but from the viewpoint of the dielectric characteristics and insulating properties of the cured film of the photosensitive resin composition, it is preferably 200 or less, from the viewpoint of improving the developability of the photosensitive resin composition layer, it is preferably 50 or more, and from the viewpoint of the balance between both performance properties, it is more preferably 60 to 150.

[0017] In this specification, the acid value is measured by potentiometric titration using 0.1 mol / L potassium hydroxide, using a Hiranuma automatic titrator (COM-555) manufactured by Hiranuma Sangyo Co., Ltd.

[0018] <(B) Polymerizable compound having an ethylenically unsaturated double bond> The polymerizable compound having an ethylenically unsaturated double bond (B) according to the present embodiment is a compound having polymerizability due to having at least one ethylenically unsaturated group in its structure. The compound having an ethylenically unsaturated double bond preferably includes a compound having three or more polymerizable groups in the molecule, and more preferably includes a compound having one polymerizable group in the molecule. In addition, the compound having an ethylenically unsaturated double bond can be used in combination with a compound other than the above.

[0019] By including a compound having three or more polymerizable groups in one molecule, the crosslink density of the cured film increases, and moisture and the like are less likely to permeate, improving the insulation reliability. A compound having three or more polymerizable groups in one molecule can be obtained by converting the hydroxyl of a polyhydric alcohol that serves as the central skeleton into a (meth)acrylate. Examples of compounds that can serve as the central skeleton include glycerin, trimethylolpropane, pentaerythritol, diglycerin, ditrimethylolpropane, dipentaerythritol, and an isocyanurate ring. An alcohol obtained by adding an alkylene oxide group such as an ethylene oxide group, a propylene oxide group, or a butylene oxide group to the central skeleton can also be converted into a (meth)acrylate, but from the viewpoint of insulation reliability, an unmodified product is preferred. From the viewpoint of dielectric properties, the compound having three or more polymerizable groups is preferably pentaerythritol hexa(meth)acrylate, pentaerythritol tetra(meth)acrylate (for example, in the case of acrylate, the product name "A-TMMT" available from Shin-Nakamura Chemical Co., Ltd.), dipentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, or ditrimethylolpropane tri(meth)acrylate.

[0020] By further including a compound having one polymerizable group in the molecule, the reaction rate of the entire compound having an ethylenically unsaturated double bond (B) is improved, and the insulating reliability can be expected to be improved. In addition, the developability is also improved. Examples of the compound having one polymerizable group in the molecule include a compound having (meth)acrylic acid added to one end of a polyalkylene oxide, a compound having (meth)acrylic acid added to one end and an alkyl ether or allyl ether at the other end, and the like. Examples of such acrylates include m-phenoxybenzyl acrylate (for example, product name "POB-A" available from Kyoeisha Chemical Co., Ltd.), o-phenylphenoxyethyl acrylate, 4-methacryloyloxybenzophenone, EO modified paracumylphenol acrylate, nonylphenoxyethyl acrylate, 4-nonylphenylheptaethylene glycol dipropylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, phenoxyhexaethylene glycol acrylate, 4-n-octylphenoxypentapropylene glycol acrylate, and 1,6-hexanediol (meth)acrylate. From the viewpoint of insulation reliability and dielectric properties, it is more preferable to include m-phenoxybenzyl acrylate, o-phenylphenoxyethyl acrylate, and 4-methacryloyloxybenzophenone.

[0021] Other (B) compounds having an ethylenically unsaturated double bond include compounds having two polymerizable groups in the molecule, such as a compound having (meth)acryloyl groups at both ends of a polyalkylene oxide chain, or a compound having (meth)acryloyl groups at both ends of an alkylene oxide chain in which a polyethylene oxide chain and a polypropylene oxide chain are randomly or block-bonded, a compound in which bisphenol A is modified with an alkylene oxide and has (meth)acryloyl groups at both ends, and a compound in which a diol having an aliphatic chain or an alicyclic structure has (meth)acryloyl groups at both ends. Specifically, other (B) compounds may be used, such as dimethacrylate of polyethylene glycol in which an average of 1 mole of ethylene oxide is added to each end of bisphenol A (for example, product name "SR-348" available from Arkema Co., Ltd.), and tricyclodecane dimethanol dimethacrylate (for example, product name "DCP" available from Shin-Nakamura Chemical Co., Ltd.).

[0022] Other examples of compounds having an ethylenically unsaturated double bond include urethane compounds which are reaction products of diisocyanate compounds and compounds having a hydroxyl group and a (meth)acrylic group in one molecule.

[0023] From the viewpoint of developability, it is more preferable that the (B) component contains at least one type of (b) compound having a molecular weight of 250 or less. Although the reason is unclear, it is considered that the inclusion of a low molecular weight component (1) makes it easier for the developer to penetrate, or (2) reduces the melt viscosity of the unexposed photosensitive resin composition, which increases the mobility of the additives and the carboxylic acid of the (A) component during lamination to the substrate, making it easier for them to interact with the substrate, thereby suppressing the generation of residues. There are no particular limitations as long as the composition has at least one ethylenically unsaturated group and a molecular weight of 250 or less, but from the viewpoint of developability and dielectric properties, triallyl isocyanurate and diallyl phthalate are preferred.

[0024] The content of the compound having an ethylenically unsaturated double bond (B) in the photosensitive resin composition is preferably 10% by mass to 60% by mass, more preferably 15% by mass to 50% by mass, based on the mass of the photosensitive resin composition, from the viewpoints of developability, insulating property, and dielectric properties. If it is within the range of 10% by mass to 60% by mass, photocuring is sufficient and good developability is obtained.

[0025] <(C) Photopolymerization initiator> In the present embodiment, the photopolymerization initiator (C) is a compound that generates radicals when exposed to actinic rays and can polymerize an ethylenically unsaturated group-containing compound or the like. (C) Examples of photopolymerization initiators include aromatic ketones such as benzophenone, N,N,N',N'-tetramethyl-4,4'-diaminobenzophenone (Michler's ketone), N,N,N',N'-tetraethyl-4,4'-diaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propanone-1, acrylated benzophenone, and 4-benzoyl-4'-methyldiphenyl sulfide; benzoin ether compounds such as benzoin methyl ether, benzoin ethyl ether, and benzoin phenyl ether; benzoin compounds such as benzoin, methylbenzoin, and ethylbenzoin; 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoylthio)phenyl]-2-morpholino-propanone-1, acrylated benzophenone, and 4-benzoyl-4'-methyldiphenyl sulfide; oxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), 1-[4-(phenylthio)phenyl]-3-cyclopentylpropane-1,2-dione-2-(o-benzoyloxime), 1,2-propanedione, 3-cyclohexyl-1-[9-ethyl-6-(2-furanylcarbonyl)-9H-carbazol-3-yl]-, 2-(O-acetyloxime), and other oxime ester compounds; benzyl derivatives such as benzyl dimethyl ketal; acridine derivatives such as 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane; N-phenylglycine derivatives such as N-phenylglycine; coumarin compounds; oxazole compounds; and phosphine oxide compounds such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. The photopolymerization initiators may be used alone or in combination of two or more.

[0026] Among these, from the viewpoint of insulation reliability, oxime ester compounds are preferred, and compounds with a high molar absorption coefficient at 365 nm are more preferred. By using an oxime initiator having a high absorption coefficient at a wavelength of 365 nm, a highly sensitive protective film can be obtained by exposure to i-line.

[0027] Specific examples of the oxime ester compound include 1,2-octanedione, 1-[(4-phenylthio)phenyl-, 2-(O-benzoyloxime)] (BASF Japan Ltd., product name: Irgacure Oxe01), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime) (BASF Japan Ltd., product name: Irgacure Oxe02), 1-[4-(phenylthio)phenyl]-3-cyclopentylpropane-1,2-dione-2-(O-benzoyloxime) (TR-PBG-305, product name, manufactured by Changzhou Powerful Electronic New Materials Co., Ltd.), and 1,2-propanedione, 3-cyclohexyl-1-[9-ethyl-6-(2-furanylcarbonyl)-9H-carbazol-3-yl]-, 2-(O-acetyloxime) (TR-PBG-326, product name, manufactured by Changzhou Powerful Electronic New Materials Co., Ltd.), (7-nitro-9,9-dipropyl-9H-fluoren-2-yl)(orthotolyl)methanone O-Acetyl oxime (Daito Chemistry Co., Ltd. DFI-020), 1,8-octanedione, 1,8-bis[9-(2-ethylhexyl)-6-nitro-9H-carbazol-3-yl]-, 1,8-bis(O-acetyl oxime), 3-cyclohexyl-1-(6-(2-(benzoyloxyimino)octanoyl)-9-ethyl-9H-carbazol-3-yl)-propane-1, Examples include 2-dione-2-(O-benzoyloxime) (product name TR-PBG-371, manufactured by Changzhou Powerful New Electronic Materials Co., Ltd.), 3-cyclohexyl-1-(6-(2-(benzoyloxyimino)hexanoyl)-9-ethyl-9H-carbazol-3-yl)-propane-1,2-dione-2-(O-benzoyloxime) (product name TR-PBG-391, manufactured by Changzhou Powerful New Electronic Materials Co., Ltd.), and the like.

[0028] The content of the (C) photopolymerization initiator in the photosensitive resin composition is preferably 0.1% by mass to 10% by mass based on the total mass of the solid content of the photosensitive resin composition, and more preferably 0.2% by mass to 5% by mass from the viewpoints of sensitivity and resolution. If the content of the photopolymerization initiator is within the range of 0.1% by mass to 10% by mass, the photosensitivity is sufficient, and problems such as insufficient internal photocuring due to increased absorption at the surface of the composition when irradiated with active light, and reduced visible light transmittance can be suppressed.

[0029] <(D) Polymer microparticles> In this embodiment, the (D) polymer fine particles are fine particles having an average particle size of 5 μm or less and a maximum particle size of 20 μm or less, and are composed of a polymer having a dielectric constant of 2.8 or less at a frequency of 10 GHz. Examples of the polymer fine particles having a dielectric constant of 2.8 or less at a frequency of 10 GHz include fine particles of polyphenylene ether (PPE), cycloolefin polymer, polyethylene, etc., and from the viewpoints of heat resistance and insulation reliability, PPE and cycloolefin polymer are preferred, and from the viewpoints of developability and dielectric properties, PPE is more preferred. Specific examples of PPE include poly(2,6-dimethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-6-phenyl-1,4-phenylene ether), poly(2,6-dichloro-1,4-phenylene ether), and the like, as well as copolymers of 2,6-dimethylphenol and other phenols (e.g., 2,3,6-trimethylphenol, 2-methyl-6-butylphenol, etc.), and polyphenylene ether copolymers obtained by coupling 2,6-dimethylphenol with biphenols or bisphenols, and the like, with a preferred example being poly(2,6-dimethyl-1,4-phenylene ether). Commercially available polyphenylene ether products include S202A, manufactured by Asahi Kasei Corporation, and the like.

[0030] From the viewpoints of heat resistance, uniformity of dielectric properties, and developability, the resin fine particles are fine particles having an average particle size of 5 μm or less and a maximum particle size of 20 μm or less. From the viewpoint of developability, the average particle size is more preferably 2 μm or less.

[0031] In this specification, the method for measuring the particle size will be described in detail in the Examples below, but the average particle size and maximum particle size of the resin fine particles were measured using a laser diffraction particle size measuring device. The particle size at 50% particle volume distribution (D50) was defined as the average particle size, and the particle size at 100% particle volume distribution (D100) was defined as the maximum particle size, with the smaller particle size being defined as 0.

[0032] The processing method for obtaining fine particles of the above particle size is not particularly limited, but examples thereof include a method of processing coarse resin particles by adding energy to the resin particles, such as dry grinding or wet grinding; a method of dissolving the resin in a heated solvent and then cooling at a constant rate to recrystallize; a method of dispersing a resin solution in water or the like containing a surfactant to form an emulsion, and then slowly heating to remove the solvent to form particles. Dry grinding is desirable from the viewpoint of cost or productivity. Examples of dry grinding include a jet mill, a ball mill, a turbo mill, and the like. In addition, in order to obtain fine particles of the desired particle size, after processing from raw material particles, classification with a sieve or the like may be performed to remove coarse or fine particles.

[0033] The content of the (D) polymer fine particles in the resin composition is preferably 5% by mass to 50% by mass based on the total mass of the solid content of the resin composition, and more preferably 10% by mass or more from the viewpoint of dielectric properties, and 25% by mass or less from the viewpoint of developability.

[0034] <(E) Flame retardant> The composition according to the present embodiment contains a flame retardant (E) from the viewpoint of imparting flame retardancy to the cured film. The flame retardant (E) according to the present embodiment is a compound that contains phosphorus or bromine in its structure and exhibits solid properties at 30°C. By using a flame retardant that exhibits solid properties at 30°C, good heat resistance and insulating reliability can be obtained. Furthermore, by containing the flame retardant (E), the photosensitive resin composition further improves the dielectric properties, developability, and insulating reliability.

[0035] Although the reason is unclear, it is believed that since a material that exhibits solid properties at 30° C. does not significantly lower the Tg of the cured film pattern of the resin composition according to this embodiment, it is possible to impart flame retardancy without impairing heat resistance or insulation reliability. It is believed that the Tg affects insulation reliability because the test is conducted under high temperature and high humidity conditions.

[0036] (E) flame retardants include, for example, bromine-based flame retardants and phosphorus-based flame retardants such as phosphazene, phosphate ester, and phosphite ester. In particular, from the viewpoint of compatibility with the resin composition and dielectric properties, bromine-based flame retardants or phosphate esters are preferably used. Examples of bromine-based flame retardants include Cytex 8010, which is ethylene bis(pentabromophenyl) manufactured by ALBEMARLE, and examples of phosphate esters include PX200 and PX202 manufactured by Daihachi Chemical Industry Co., Ltd. These flame retardants may be used alone or in combination of two or more kinds.

[0037] The content of the flame retardant (E) in the resin composition is 5% by mass to 40% by mass based on the total mass of the solid content of the resin composition, and from the viewpoints of developability and dielectric properties, it is more preferably 10% by mass to 30% by mass. If the content of the flame retardant (E) is within the range of 1% by mass to 40% by mass, the dielectric properties after thermal curing are good, and no adverse effects on developability are observed.

[0038] <(F) Heterocyclic compounds> In the composition according to the present embodiment, it is preferable to further contain a heterocyclic compound (F) from the viewpoint of developability. As the heterocyclic compound (F), from the viewpoint of compatibility with the photosensitive resin according to the present embodiment, a heterocyclic compound containing N, S, O, etc. is preferable, and examples thereof include tetrazole and its derivatives, triazole and its derivatives, imidazole and its derivatives, indazole and its derivatives, imidazoline and its derivatives, thiadiazole and its derivatives, thiazole and its derivatives, and isothiazole and its derivatives. The derivatives described here include compounds in which a substituent is introduced into the parent structure. For example, in the case of a tetrazole derivative, a compound in which a substituent is introduced into tetrazole is included. The substituent is not particularly limited, and examples thereof include a hydrocarbon group (which may be saturated or unsaturated, may be linear or branched, and may include a cyclic structure in the structure), or a substituent containing one or more functional groups having a heteroatom such as a hydroxyl group, a carbonyl group, a carboxyl group, an amino group, an amide group, a nitro group, a cyano group, a thiol group, and a halogen (fluorine, chlorine, bromine, iodine, etc.) group. Specific examples are shown below.

[0039] Specific examples of tetrazole include 1H-tetrazole, 5-amino-1H-tetrazole, 5-methyl-1H-tetrazole, 1-methyl-5-ethyl-1H-tetrazole, 1-methyl-5-mercapto-1H-tetrazole, 1-phenyl-5-mercapto-1H-tetrazole, 1-(dimethylaminoethyl)-5-mercapto-1H-tetrazole, 5-phenyl-1H-tetrazole, 5-benzyl-1H-tetrazole, and 1H-tetrazole-5-acetic acid.

[0040] Specific examples of triazoles include 1,2,3-triazole, 3-mercaptotriazole, 3-amino-5-mercaptotriazole, benzotriazole, 1H-benzotriazole-1-acetonitrile, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, 1-(2-di-n-butylaminomethyl)-5-carboxybenzotriazole, 1-(2-di-n-butylaminomethyl)-6-carboxybenzotriazole, 1H-benzotriazole-1-methanol, 5-methyl-1H-benzotriazole, 5-carboxybenzotriazole, 1-hydroxybenzotriazole, 5-chlorobenzotriazole, and 5-nitrobenzotriazole.

[0041] Specific examples of imidazole include undecylimidazole, benzimidazole, 5-carboxybenzimidazole, 6-bromobenzimidazole, 5-chlorobenzimidazole, 2-hydroxybenzimidazole, 2-(1-hydroxymethyl)benzimidazole, 2-methylbenzimidazole, 5-nitrobenzimidazole, 2-phenylbenzimidazole, 2-aminobenzimidazole, 5-aminobenzimidazole, and 5-amino-2-mercaptobenzimidazole.

[0042] Specific examples of indazole include 1H-indazole, 5-aminoindazole, 6-aminoindazole, 1-benzyl-3-hydroxy-1H-indazole, 5-bromoindazole, 6-bromoindazole, 6-hydroxyindazole, 3-carboxyindazole, and 5-nitroindazole.

[0043] Examples of imidazoline or imidazoline derivatives include 2-undecylimidazoline, 2-propyl-2-imidazoline, and 2-phenylimidazoline.

[0044] Specific examples of thiadiazole include 1,2,3-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 4-amino-2,1,3-benzothiadiazole, 2-amino-5-mercapto-1,3,4-thiadiazole, 2-amino-5-methyl-1,3,4-thiadiazole, 2-amino-1,3,4-thiadiazole, 5-amino-1,2,3-thiadiazole, and 2-mercapto-5-methyl-1,3,4-thiadiazole.

[0045] Specific examples of thiazoles include 2-amino-4-methylthiazole, 5-(2-hydroxyethyl)-4-methylthiazole, benzothiazole, 2-mercaptobenzothiazole, 2-aminobenzothiazole, 2-amino-6-methylbenzothiazole, (2-benzothiazolylthio)acetic acid, and 3-(2-benzothiazolylthio)propionic acid.

[0046] Examples of isothiazole or isothiazole derivatives include 3-chloro-1,2-benzisothiazole.

[0047] Among these, from the viewpoint of developability, tetrazole and its derivatives, and triazole and its derivatives are preferred, and 5-amino-1H-tetrazole, 1H-tetrazole-5-acetic acid, 5-carboxybenzotriazole, 5-aminoindazole, and 5-amino-1,2,3-thiadiazole are more preferred. The heterocyclic compounds may be used alone or in combination of two or more kinds.

[0048] Although the reason is unclear, it is believed that when a transfer film is formed from the resin composition according to this embodiment containing the heterocyclic compound (F) and laminated to a substrate for use, the heat of lamination causes the heterocyclic compound (F) to localize on the substrate surface. The localization of the heterocyclic compound on the substrate surface prevents the polymer fine particles (D) from remaining on the substrate surface during the development process, and furthermore, when the heterocyclic compound (F) has a carboxylic acid or amino group, it is easily removed by the developer, improving developability.

[0049] From the viewpoints of insulation reliability, developability, and dielectric properties, the content of the (F) heterocyclic compound in the composition is preferably 0.1% by mass to 10% by mass, more preferably 0.2% by mass to 5% by mass, and even more preferably 0.3% by mass to 3% by mass, based on the mass of the resin composition. If the content of the (F) heterocyclic compound is within the range of 0.1% by mass to 10% by mass, the insulation reliability, developability, and dielectric properties are good.

[0050] <(G) Blocked isocyanate compound> From the viewpoints of developability and insulation reliability, the composition according to the present embodiment preferably further contains a blocked isocyanate compound. The blocked isocyanate compound is a compound obtained by reacting an isocyanate compound having one or more isocyanate groups in the molecule with a blocking agent. Examples of the isocyanate compound include 1,6-hexane diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 4,4'-hydroxylated diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, 4,4-diphenyl diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, 1,4-phenylene diisocyanate, 2,6-phenylene diisocyanate, 1,3,6-hexamethylene triisocyanate, and hexamethylene diisocyanate. Examples of blocking agents include alcohols, phenols, ε-caprolactam, oximes, active methylenes, mercaptans, amines, imides, acid amides, imidazoles, ureas, carbamates, imines, and sulfites.Examples of the blocked isocyanate compound include hexamethylene diisocyanate-based blocked isocyanates (e.g., Duranate SBN-70D, SBB-70P, SBF-70E, TPA-B80E, 17B-60P, MF-B60B, E402-B80B, MF-K60B, and WM44-L70G manufactured by Asahi Kasei Corporation, Takenate B-882N manufactured by Mitsui Chemicals, Inc., and 7960, 7961, 7982, 7991, and 7992 manufactured by Baxenden), and tolylene diisocyanate-based blocked isocyanates (e.g., Takenate B-830 manufactured by Mitsui Chemicals, Inc.). , 4,4'-diphenylmethane diisocyanate-based blocked isocyanates (e.g., Takenate B-815N manufactured by Mitsui Chemicals, Inc., Bronate PMD-OA01 and PMD-MA01 manufactured by Daiei Sangyo Co., Ltd., etc.), 1,3-bis(isocyanatemethyl)cyclohexane-based blocked isocyanates (e.g., Takenate B-846N manufactured by Mitsui Chemicals, Inc., Coronate BI-301, 2507, and 2554 manufactured by Tosoh Corporation, etc.), and isophorone diisocyanate-based blocked isocyanates (e.g., 7950, 7951, and 7990 manufactured by Baxenden, etc.). The blocked isocyanate compounds may be used alone or in combination of two or more kinds. In addition, it is preferable to use them in combination with a diol compound described later in order to improve the mechanical strength of the cured film.

[0051] Although the reason is unclear, the present inventors speculate that the inclusion of a blocked isocyanate reduces the melt viscosity of the unexposed photosensitive resin composition, thereby improving the developability for the reasons described later in the section <Haze after lamination onto glass substrate>.

[0052] The content of the blocked isocyanate compound in the photosensitive resin composition is 1% by mass to 40% by mass based on the total mass of the solid content of the photosensitive resin composition, and from the viewpoints of developability, insulation reliability, and dielectric properties, it is more preferably 2% by mass to 30% by mass, and further preferably 5% by mass to 25% by mass.

[0053] <Other additives> Diol compounds The photosensitive resin composition preferably further contains a diol compound to improve the mechanical properties of the cured film and reduce cure shrinkage, and more preferably uses a blocked isocyanate and a diol compound in combination from the viewpoint of dielectric properties. The diol compound refers to one that contains two hydroxyl groups per molecular chain. Examples of the diol compound include those that contain a hydrocarbon group such as an aliphatic, aromatic, or alicyclic group in the skeleton. Specific examples of the diol compound include polytetramethylene diol (e.g., P4TMG650, PTMG850, PTMG1000, PTMG1300, PTMG1500, PTMG1800, PTMG2000, and PTMG3000 manufactured by Mitsubishi Chemical Corporation), polybutadiene diol (e.g., G-1000, G-2000, and G-3000 manufactured by Nippon Soda Co., Ltd.), hydrogenated polybutadiene diol (e.g., GI-1000, GI-2000, and GO-3000 manufactured by Nippon Soda Co., Ltd.), polycarbonate diol (e.g., Duranol T5651, Duranol T5652, Duranol T4671, Duranol G4672, Duranol G3452, and Duranol G3452 manufactured by Asahi Kasei Corporation), and 50J, and Kuraray Polyol C-590, Kuraray Polyol C-1090, Kuraray Polyol C-2090, and Kuraray Polyol C-3090 manufactured by Kuraray Co., Ltd.), polycaprolactone diols (e.g., Plaxel 205PL, Plaxel 210, Plaxel 220, and Plaxel 220PL manufactured by Daicel Co., Ltd.), polyester diols (e.g., Kuraray Polyol P-530, Kuraray Polyol P-2030, and Kuraray Polyol P-2050 manufactured by Kuraray Co., Ltd., and HS2N-220S manufactured by Toyokuni Oil Mills Co., Ltd.), bisphenols (e.g., Bisphenol A manufactured by Mitsubishi Chemical Co., Ltd.), and hydrogenated bisphenols (e.g., Rikavinoll HB manufactured by New Japan Chemical Co., Ltd.). These diol compounds may be used alone or in combination of two or more. In the heat treatment after the pattern formation by development, the hydroxyl group of the diol compound reacts with the blocked isocyanate compound, thereby improving the mechanical properties and dielectric properties of the cured film.

[0054] In addition, the photosensitive resin composition may contain a polymerization inhibitor such as an aluminum salt having 3 moles of nitrosophenylhydroxylamine added thereto, an antioxidant, an adhesion aid, a leveling agent, an antifoaming agent, and the like, which may be used alone or in combination of two or more kinds.

[0055] <Transfer film> Next, a transfer film using the above resin composition will be described. The transfer film includes a resin layer made of the resin composition and a temporary support, and in some cases further includes a protective film for protecting the resin layer. Specifically, the transfer film is a laminate formed by laminating a photosensitive resin layer made of the above-described photosensitive resin composition on a temporary support, and when a protective film is required, the photosensitive resin layer has a protective film on the surface opposite to the support side. The transfer film according to this embodiment can also be used to form a protective film or insulating film for the high frequency substrate described above.

[0056] The method for producing the transfer film includes a step of applying a coating liquid onto a temporary support such as a PET film, drying the coating liquid, and further includes a step of laminating a protective layer onto the resin layer as required. The coating liquid can be obtained by uniformly dissolving the photosensitive resin composition described above in a solvent.

[0057] The solvent for dissolving the resin composition varies depending on the resin used, but examples thereof include ketones such as methyl ethyl ketone (MEK), alcohols such as methanol, ethanol, or 1-methoxy-2-propanol, or aprotic solvents such as γ-butyrolactone (GBL) or N-methylpyrrolidone (NMP), etc. The solvent is preferably added to the resin composition so that the viscosity of the solution of the resin composition to be applied onto the temporary support is 10 mPa·s to 500 mPa·s at 25°C.

[0058] Examples of the coating method include doctor blade coating, Mayer bar coating, roll coating, screen coating, spinner coating, inkjet coating, spray coating, dip coating, gravure coating, curtain coating, die coating, etc. There are no particular limitations on the drying conditions of the coating liquid, but the drying temperature is preferably 50° C. to 130° C., and the drying time is preferably 30 seconds to 30 minutes.

[0059] The film thickness of the resin layer varies depending on the application, but from the viewpoint of conforming to the unevenness of the wiring and ensuring insulation reliability, the thickness after drying is preferably 5 μm or more, and from the viewpoint of the stability over time and developability of the transfer film, the thickness is preferably 50 μm or less, and more preferably 30 μm or less.

[0060] The support used in this embodiment is preferably transparent and transmits the light emitted from the exposure light source. Examples of such a temporary support include polyethylene terephthalate film, polyvinyl alcohol film, polyvinyl chloride film, vinyl chloride copolymer film, polyvinylidene chloride film, vinylidene chloride copolymer film, polymethyl methacrylate copolymer film, polystyrene film, polyacrylonitrile film, styrene copolymer film, polyamide film, and films made of cellulose and its derivatives. These films can also be stretched as necessary. The haze of the temporary support is preferably 5 or less. The smaller the thickness of the temporary support, the more advantageous it is in terms of resolution and economy, but it is preferably 10 μm to 30 μm in order to maintain strength.

[0061] An important characteristic of the protective layer used in the transfer film is that the adhesive strength between the protective layer and the photosensitive resin layer is sufficiently smaller than that of the temporary support, and the protective layer can be easily peeled off. For example, a polyethylene film, a polypropylene film, etc. can be preferably used as the protective layer. Also, a film with excellent peelability as shown in JP-A-59-202457 can be used as the protective layer. The thickness of the protective layer is preferably 10 μm to 100 μm, more preferably 10 μm to 50 μm.

[0062] <Haze after lamination on glass substrate> The photosensitive resin composition according to this embodiment is applied onto a support to form a transfer film having a thickness of 25 μm, and then laminated onto a glass substrate having a thickness of 1.1 mm at a roll temperature of 95° C. using a hot roll laminator. The haze is 15% or less when the film is laminated. Detailed measurement conditions are described in the Examples section, but these conditions have been found as an index for achieving both dielectric properties and developability. Developability tends to deteriorate in compositions containing (D) polymer fine particles due to dielectric properties, but compositions having a haze of 15% or less under the above conditions can obtain good developability.

[0063] Although the reason is unclear, the present inventors believe that the haze is low in compositions with a haze of 15% or less because the melt viscosity of the photosensitive resin composition is low and the composition easily conforms to a smooth glass substrate even at a lamination temperature of 95°C. It is believed that a composition with a low melt viscosity has high mobility of each compound in the photosensitive resin composition during lamination, and components advantageous for development are partially localized on the substrate surface, suppressing (D) polymer fine particles and the like from becoming development residues, thereby improving developability. Possible components advantageous for development include the carboxylic acid moiety of an alkali-soluble resin, a flame retardant, a heterocyclic compound, and the like. The haze increases when the amount of polymer fine particles (D) added is increased and / or the average particle size is increased, and decreases when the amount of flame retardant (E) added is increased. The haze can also be reduced by adding or increasing the amount of (b) a compound having a molecular weight of 250 or less and (G) a blocked isocyanate compound. When a large amount of polymer fine particles (D) is added for dielectric properties, a composition having excellent dielectric properties and good developability can be obtained by adjusting the haze to 15% or less by adding or increasing the amount of component (E), compound (b), and component (G). Although not limited to this range, in order to make the haze 15% or less, the amount of polymer fine particles (D) is preferably 25% by mass or less and the amount of flame retardant (E) is preferably 10% by mass or more based on the total mass of the solid content of the resin composition.

[0064] <Resin Pattern, Cured Film Pattern, and Methods for Producing the Same> The resin pattern of this embodiment is formed from the exposed and developed product of the transfer film of this embodiment. The formation of the resin pattern using the transfer film of this embodiment includes the following steps: A lamination step of laminating the transfer film (laminate) described above onto a substrate; an exposure step of exposing the laminated transfer film; and a developing step of developing the exposed transfer film; The resin pattern can be produced by a method for producing a resin pattern comprising the steps of: (a) forming a cured film pattern by subjecting the resin pattern to post-exposure treatment and / or heat treatment after the development step in order to use the resin pattern as a protective film for the conductor portion; (b) forming a cured film pattern by subjecting the resin pattern to post-exposure treatment and / or heat treatment after the development step. If the resin pattern does not have photodevelopability, the exposure step and development step are omitted, and the desired cured film can be obtained by laminating and heat treatment.

[0065] A specific example of the method is shown below. The substrate may be a substrate in which copper wiring is formed on a flexible copper-clad laminate, or a substrate in which a metal layer of copper, nickel, silver, copper alloy, or the like is formed on a flexible film. The above-mentioned film may be, for example, a film made of a film material such as polyimide, polyester (PET, PEN), or cycloolefin polymer (COP). The thickness of the above-mentioned film is preferably 10 μm to 100 μm. The above-mentioned copper alloy may be an alloy containing copper as a main component. Here, the term "main component" means that at least 50 mass % of the alloy is copper. The alloy metal may be, for example, an alloy of copper with nickel, palladium, silver, titanium, molybdenum, or the like. The thickness of the copper layer is preferably 50 nm to 2 μm. From the viewpoint of uniformity of the copper layer, the thickness of the copper layer is more preferably 100 nm or more.

[0066] A resin layer is formed on the copper layer of the substrate by laminating the transfer film on the substrate. When the resin layer has a protective layer, the protective layer is peeled off, and then the transfer film is laminated on the substrate surface by heat and pressure using a laminator. In this case, the transfer film may be laminated on only one side of the substrate surface, or on both sides. The heating temperature is generally about 40°C to 160°C. The heat and pressure bonding may be performed using a two-stage laminator equipped with two rolls, or may be performed by repeatedly passing the transfer film and the substrate through the rolls multiple times. In addition, when a vacuum laminator is used, the protective film has good conformability to unevenness due to wiring on the substrate, and the defect of air being mixed between the transfer film and the substrate can be prevented.

[0067] Next, an exposure step is performed using an exposure machine. If necessary, the temporary support is peeled off from the transfer film, and the transfer film is exposed to active light through a photomask. The exposure amount is determined by the light source illuminance and exposure time. The exposure amount may be measured using an actinometer. Examples of the exposure machine include a scattered light exposure machine using an ultra-high pressure mercury lamp as a light source, a parallel light exposure machine with adjusted parallelism, and a proximity exposure machine with a gap between the mask and the workpiece. Further, examples of the exposure machine include a projection type exposure machine with a mask to image size ratio of 1:1, a reduction projection exposure machine called a high-illuminance stepper (registered trademark), or an exposure machine using a concave mirror called a mirror projection aligner (registered trademark).

[0068] In addition, in the exposure step, a direct writing exposure method may be used. Direct writing exposure is a method of directly writing and exposing a substrate without using a photomask. As a light source, for example, a solid-state laser, a semiconductor laser, or an ultra-high pressure mercury lamp having a wavelength of 350 nm to 410 nm is used. The drawing pattern is controlled by a computer. In this case, the exposure amount is determined by the illuminance of the light source and the moving speed of the substrate.

[0069] Next, a development step is performed using a developing device. After exposure, if there is a temporary support on the photosensitive resin layer, the temporary support is removed as necessary, and then the unexposed portion is developed and removed using an alkaline aqueous developer to obtain a resin pattern. As the alkaline aqueous solution, it is preferable to use an aqueous solution of Na2CO3 or K2CO3 (alkaline aqueous solution). The alkaline aqueous solution is appropriately selected according to the characteristics of the photosensitive resin layer, but an aqueous Na2CO3 solution with a concentration of about 0.2% by mass to 2% by mass and at about 20°C to 40°C is generally used. A surfactant, an antifoaming agent, a small amount of an organic solvent for promoting development, etc. may be mixed into the alkaline aqueous solution. In consideration of the influence on the substrate, an amine-based alkaline aqueous solution such as an aqueous tetramethylammonium hydroxide (TMAH) solution can also be used. The concentration of the alkaline compound in the aqueous solution can be appropriately selected according to the development speed. From the viewpoints of low odor, excellent handling, and easy management and post-treatment, an aqueous Na2CO3 solution of 1% by mass and 30°C to 35°C is particularly preferable. The developing method may be a known method such as alkaline water spray, shower, shaking immersion, brushing, scraping, etc.

[0070] After development, the base of the alkaline aqueous solution remaining in the resin pattern can be acid-treated (neutralized) using an organic acid, an inorganic acid, or an aqueous solution of these acids by a known method such as spraying, rocking immersion, brushing, scraping, etc. Furthermore, after the acid treatment (neutralization), a step of washing with water can also be carried out.

[0071] Although a resin pattern can be obtained through each of the above steps, a post-exposure step and / or a heating step may be further carried out. By carrying out a post-exposure step and / or a heating step, the insulation reliability, heat resistance and dielectric properties are further improved. The exposure dose in the post-exposure treatment is 200 mJ / cm 2 ~1000mJ / cm 2is preferable, and in the heating step, it is preferable to perform the treatment at 40°C to 200°C. From the viewpoint of the manufacturing process, the heat treatment time is preferably 60 minutes or less. As the heat treatment method, a heating furnace of an appropriate method such as hot air, infrared rays, far-infrared rays, etc. can be used, and as the atmosphere for the heat treatment, an N2 atmosphere or an N2 / O2 atmosphere can be mentioned.

[0072] According to the present embodiment, it is possible to provide a low dielectric resin composition and a transfer film that are both excellent in dielectric properties, heat resistance, flame retardancy, and insulation, and are suitable for a protective material for FPC and an insulating layer of a printed wiring board.

Examples

[0073] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited thereto.

[0074] 1. Regarding the (A) alkali-soluble polymer component As (A-1) used in the present example and comparative examples, commercially available ZCR-1797H (acid-modified product of epoxy acrylate having a biphenyl skeleton, manufactured by Nippon Kayaku Co., Ltd.), weight average molecular weight (Mw) 6500, acid value 98 mgKOH / g was used. (A-2) was prepared by the following method.

[0075] <Method for preparing A-2> Into a 2L flask equipped with a stirrer, a reflux condenser, an inert gas inlet, and a thermometer, methyl ethyl ketone was charged at 100% by mass, and the temperature was raised to 75°C under a nitrogen gas atmosphere. 24% by mass of acrylic acid, 73% by mass of styrene, 3% by mass of n-butyl acrylate, and an azo-based polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd., V-601) were uniformly added dropwise over 2 hours. After the addition, stirring was continued at 75°C for 10 hours. After the reaction was completed, the resin solution obtained using methyl ethyl ketone was diluted to obtain an alkali-soluble resin solution (solid content 50% by mass) (A-2) having an acid value of 187 mgKOH / g and an Mw of about 29,000. The measurement of the weight average molecular weight and acid value of the alkali-soluble polymer was carried out by the method described in detail in <(A) Alkali-soluble polymer> above.

[0076] 2. (D) Particle size measurement of polymer microparticles The average particle size and maximum particle size of the crushed resin microparticles (D-1) were measured using a laser diffraction / scattering particle size distribution analyzer (LA950V2, manufactured by HORIBA Corporation). Based on the data obtained by the operation described below, the particle size at 50% particle volume distribution (D50) was set as 0, and the particle size at 100% particle volume distribution (D100) was set as the average particle size, and the particle size at 100% particle volume distribution (D100) was set as the maximum particle size. A polymer microparticle dispersion solution with a solid content of 15 wt% was prepared using propylene glycol monomethyl ether acetate (PGMEA) as a solvent. As a pretreatment, a measurement sample was prepared by ultrasonic treatment for 5 minutes. Using this measurement sample, the conditions were set as follows: PPE particle refractive index: 1.60, solvent: PGMEA, refractive index: 1.40, and the particle size was measured. The measured particle sizes are shown in Tables 1 and 2.

[0077] 3. Preparation of photosensitive resin composition solution According to the compositions shown in Tables 1 and 2 below (where the numbers for each component indicate the amount (parts by mass) of solid content), each component other than component (D) was weighed out into a 250 ml plastic bottle, methyl ethyl ketone was added so that the solid content concentration was 60 to 65 mass%, and dissolution and mixing were performed for 5 hours using a stirrer. After mixing, component (D) (the 15 wt% PGMEA dispersion solution described in the previous section was used) was added in the amount shown in Table 1, and methyl ethyl ketone was further added so that the final solid content concentration was 32%, and the mixture was stirred for 5 hours using a stirrer. In this way, photosensitive resin composition preparations (Examples 1 to 13 and Comparative Examples 1 to 6) were obtained. The names of the material components in the photosensitive resin composition preparations shown in Tables 1 and 2 are shown in Table 3.

[0078] 4. Preparation of evaluation film The evaluation films in the examples and comparative examples were prepared as follows. <Preparation of transfer film> The photosensitive resin composition preparation liquid was uniformly applied to the surface of a 16 μm thick polyethylene terephthalate film (Mitsubishi Chemical Corporation, R310-16B) serving as a support film using a blade coater, and dried in a dryer at 95° C. for 5 minutes to form a uniform photosensitive resin layer on the temporary support. The thickness of the photosensitive resin layer after drying was 25 μm. Next, a 33 μm thick polyethylene film (Tamapoly Corporation, GF-858) was laminated as a protective film on the surface of the photosensitive resin layer to obtain a transfer film. The obtained transfer film for evaluation was evaluated by the following method, and the evaluation results are shown in Tables 1 and 2.

[0079] 5. Haze measurement While peeling off the protective film of the photosensitive resin laminate having a thickness of 25 μm, the laminate was laminated on a glass substrate (SCHOTT, TEMPAX Float) having a thickness of 1.1 mmt using a hot roll laminator (TAISEI LAMINATOR CO., LTD., VA-400III) to obtain a laminate having a three-layer structure of temporary support film / photosensitive resin layer / glass substrate from the top (lamination conditions were roll temperature 95° C., air pressure 0.4 MPa, and speed 1.0 m / min). After that, the temporary support film was peeled off, and the film was left to stand for 1 hour, and then the haze was measured using a haze meter (Nippon Denshoku Industries Co., Ltd., NDH2000) according to a method corresponding to JIS K7136. The measurement results were judged as follows, and the results are shown in Tables 1 to 2. ○: Haze is 15% or less ×: Haze exceeds 15% In the haze measurement results, ◯ is an index of practically good developability.

[0080] 6. Evaluation of developability While peeling off the protective film from the photosensitive resin laminate having a photosensitive resin layer thickness of 25 μm prepared above, lamination was performed on a flexible copper-clad laminate measuring 10 cm x 15 cm (Nippon Steel Chemical & Material Co., Ltd., Espanex: MC12-25-00HRM) using a hot roll laminator (Taisei Laminator Co., Ltd., VA-400III), to obtain a laminate consisting of a three-layer structure of temporary support film / photosensitive resin layer / flexible copper-clad laminate from the top (lamination conditions were roll temperature 125°C, air pressure 0.4 MPa, and speed 1.0 m / min). After leaving it for 15 minutes, a PET mask and a Stoufer 21-step step tablet (a step tablet with an optical density of 0.00 as the first step and an optical density of 0.15 increasing for each step) were placed side by side on the temporary support film, and the optimal exposure amount for each composition was determined from the PET mask and step tablet side, and exposed using a parallel light exposure machine (Oak Manufacturing Co., Ltd., HMW-801). The PET mask used had a pattern in which the unexposed parts were circular holes. After leaving it for 15 minutes or more, the temporary support was peeled off, and a 1% by mass Na2CO3 aqueous solution at 30°C was sprayed with a full cone type nozzle at a development spray pressure of 0.14 MPa using a Fuji Kiko Co., Ltd. developing device for development, for a development time twice the time until the photosensitive resin layer was completely dissolved (break point), and the unexposed parts of the photosensitive resin layer were dissolved and removed. At that time, the water washing step was performed with a flat type nozzle at a water washing spray pressure of 0.08 MPa for the same time as the development step, and the washed sample was dried by air blowing to prepare a sample for developing property evaluation. The above-mentioned optimum exposure amount means an exposure amount at which the number of steps remaining in the film when exposed through a Stoufer 21-step step tablet is 7 to 8 steps. The circular hole portions removed by development of the samples thus prepared were observed under an optical microscope, and the smallest circular hole size that could be developed without leaving any residue was evaluated as follows. ◎: The minimum opening diameter of the circular hole is 150 μm or less. ○: The minimum opening diameter of the circular hole is greater than 150 μm and less than 300 μm. ×: Openings of 300 μm or less are not possible. In the evaluation of developability, ⊚ and ◯ are considered to be good results in practical use.

[0081] 7. Dielectric Characterization While peeling off the protective film of the photosensitive resin laminate with a thickness of 25 μm, the laminate was laminated on an easily peelable PET (X-25, manufactured by Lintec Corporation) with a size of 10 cm × 15 cm using a hot roll laminator (VA-400III, manufactured by Taisei Laminator Co., Ltd.), and a laminate consisting of a three-layer structure of temporary support film / photosensitive resin layer / easily peelable PET was obtained from the top (lamination conditions were roll temperature 125 ° C, air pressure 0.4 MPa, and speed 1.0 m / min). After leaving it for 15 minutes, the entire surface was exposed from the temporary support film side to the optimal exposure amount (the definition is the same as in "6. Development evaluation" above) for each composition using a parallel light exposure machine (HMW-801, manufactured by Oak Manufacturing Co., Ltd.). After leaving it for 15 minutes or more, it was developed, washed with water, and dried in the same manner as in "6. Development evaluation". Then, a scattered light exposure machine (Oak Manufacturing Co., Ltd., HMW-201KB) was used to expose the photosensitive layer at 300 mJ / cm 2 Then, the whole surface was exposed to light at an exposure amount of 175° C. for 60 minutes in a hot air circulating oven. After that, the easily peelable PET was peeled off to obtain a single film of a cured photosensitive resin layer.

[0082] The sample thus prepared was conditioned for 24 hours in an environment of 23° C. and 50% RH, and the dielectric loss tangent at 10 GHz was measured using the measuring device described below, and the sample was evaluated as follows. Network analyzer: PNA Network Analyzer E8362B (Keysight Technologies) Resonator: Split cylinder resonator 10GHz (EM Lab, CR-710) ◎: Dielectric tangent is 0.005 or less ○: Dielectric tangent is greater than 0.005 and less than 0.0075 ×: The dielectric tangent exceeds 0.0075. In the dielectric loss tangent measurement results, ⊚ and ◯ are considered to be good results for practical use.

[0083] 8.Insulation reliability evaluation The photosensitive resin laminate with a thickness of 25 μm prepared above was laminated onto the conductor of a flexible copper-clad laminate (ESPANEX: MC12-25-00HRM, product name of Nippon Steel Chemical & Material Co., Ltd.) on which a comb-shaped wiring for evaluating ion migration had been patterned in advance with L / S = 50 / 50 μm, using a roll-type thermal vacuum laminator (MCK Corporation, MVR-250) while peeling off the protective film, to obtain a laminate consisting of a three-layer structure of temporary support film / photosensitive resin layer / flexible copper-clad laminate from the top (lamination conditions were roll temperature 80°C, air pressure 0.4 MPa, vacuum degree = 100 Pa, and speed 1.0 m / min). After leaving it to stand for 15 minutes, a PET mask was placed on the support film so that only the electrode parts would be opened by development to allow for later electrical continuity, and the optimal exposure amount for each composition (defined as in 6. Evaluation of developability) was exposed using a parallel light exposure machine (Oak Manufacturing Co., Ltd., HMW-801). After leaving it to stand for 15 minutes or more, the temporary support was peeled off, and the film was developed, washed, and dried in the same manner as in "6. Evaluation of developability". Then, the film was exposed to 300 mJ / cm2 from the photosensitive layer side using a scattered light exposure machine (Oak Manufacturing Co., Ltd., HMW-201KB). 2 Then, the whole surface was exposed to light at an exposure dose of 100 nm, and then heated in a hot air circulation oven at 175°C for 60 minutes to obtain a laminate of flexible printed wiring boards. Then, an electromagnetic wave shielding film (SF-PC5600-C, manufactured by Tatsuta Electric Wire Co., Ltd.) was aligned so as to be partially connected to the cathode side electrode of the photosensitive resin layer of the flexible printed wiring board, and laminated using a vacuum press (manufactured by Kitagawa Seiki Co., Ltd.) under conditions of 170°C, 3 MPa, and 5 minutes, and then heated in a hot air circulation oven at 150°C for 60 minutes to perform curing.

[0084] The interlayer insulation resistance between the printed wiring board with the electromagnetic shielding film produced by the above method and the shielding film was measured using the following equipment and conditions, and the insulation reliability was evaluated by checking the time until the insulation resistance value decreased. A voltage of 50 VDC was applied to the printed wiring board continuously for 1000 hours using the following equipment and conditions. Ion migration device: AMI-050-U-5 (manufactured by Espec Corporation) Constant temperature and humidity oven: PR-2KT (manufactured by Espec Corporation) Temperature and humidity conditions: 85℃ / 85%RH Voltage: 50VDC The results of the insulation reliability test were evaluated as follows. ◎: The time until the insulation resistance value changes is 500 hours or more. ○: The time until the insulation resistance value changes is 300 hours or more but less than 500 hours. ×: Insulation resistance value changes in less than 300 hours. In the insulation reliability test results, ⊚ and ◯ are considered to be good results for practical use.

[0085] 9.Heat resistance evaluation While peeling off the protective film of the photosensitive resin laminate with a thickness of 25 μm, a 10 cm x 15 cm flexible copper-clad laminate (Nippon Steel Chemical & Material Co., Ltd., Espanex: MC12-25-00HRM) was laminated using a hot roll laminator (Taisei Laminator Co., Ltd., VA-400III) to obtain a laminate consisting of a three-layer structure of temporary support film / photosensitive resin layer / flexible copper-clad laminate from the top (lamination conditions were roll temperature 125°C, air pressure 0.4 MPa, and speed 1.0 m / min). After leaving it for 15 minutes, the optimal exposure amount (defined as in "6. Development Evaluation") for each composition was exposed over the entire surface using a parallel light exposure machine (Oak Manufacturing Co., Ltd., HMW-801). After that, after leaving it to stand for 15 minutes or more, the temporary support was peeled off, and the development, washing, and drying were carried out in the same manner as in "6. Evaluation of developability". Then, the sample was exposed to 300 mJ / cm2 from the photosensitive layer side using a scattered light exposure machine (Oak Manufacturing Co., Ltd., HMW-201KB). 2 Then, the laminate was heated in a hot air circulating oven at 175° C. for 60 minutes to obtain a laminate.

[0086] The laminate thus produced was dipped three times in a solder bath at 320° C. for 5 seconds each, and then the appearance was observed under an optical microscope and judged as follows. ○: No abnormalities in appearance ×: The film peeled off or there was some swelling on the surface. In the heat resistance evaluation, a rating of ◯ is considered to be a good result for practical use.

[0087] 10.Flame retardancy evaluation While peeling off the protective film of the photosensitive resin laminate with a photosensitive resin layer thickness of 25 μm prepared above, lamination was performed on both sides of Kapton 100EN (manufactured by Toray DuPont) using a hot roll laminator (manufactured by Taisei Laminator Co., Ltd., VA-400III) to obtain a double-sided laminate film (lamination conditions were roll temperature 125°C, air pressure 0.4 MPa, and speed 1.0 m / min). After leaving it to stand for 15 minutes, both sides were exposed to the entire surface with the optimal exposure amount (defined as in "6. Development evaluation") for each composition using a parallel light exposure machine (manufactured by Oak Manufacturing Co., Ltd., HMW-801). After leaving it to stand for 15 minutes or more, the temporary support was peeled off, and development, washing, and drying were performed in the same manner as in "6. Development evaluation". Then, 300 mJ / cm2 was applied from the photosensitive layer side using a scattered light exposure machine (manufactured by Oak Manufacturing Co., Ltd., HMW-201KB). 2 Subsequently, the laminate was heated in a hot air circulating oven at 175° C. for 60 minutes to obtain a laminate.

[0088] This laminate was subjected to a thin material vertical flame test in accordance with the UL 94 standard. The evaluation was based on the UL 94 standard and was rated as follows, from "VTM-0" to "flammable". ◎: VTM-0, burning time less than 5 seconds 〇: VTM-0, burning time 10 seconds or less ×: Fail In the flame retardancy evaluation, ⊚ and ◯ are considered to be good results for practical use.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] The results shown in Tables 1 and 2 indicate that Examples 1 to 13 satisfy the requirements defined in the present invention and are therefore excellent in developability, dielectric properties, heat resistance, flame retardancy, and insulation reliability. On the other hand, Comparative Examples 1 to 6 do not satisfy any of the requirements defined in the present invention and are therefore inferior in any of developability, dielectric properties, heat resistance, flame retardancy, and insulation reliability.

[0093] Comparative Example 1 has the same composition as Example 1 except that it does not contain component (D), but has inferior dielectric properties. Comparative Example 2 differs from Example 1 only in that it uses component (D) with an average particle size of more than 5 μm, but has inferior developability. This shows that by using the specified component (D) of the present invention, a photosensitive resin composition with excellent dielectric properties and developability can be obtained.

[0094] In addition, it is found that Comparative Examples 3 and 4, which are compositions that do not contain the flame retardant component (E) compared to Examples 1 and 2, have deteriorated dielectric properties, insulating reliability, developability, and flame retardancy. On the other hand, Comparative Example 5 contains a flame retardant, but is liquid at 30°C and does not meet the requirements of the present invention, and therefore has inferior insulating reliability and heat resistance compared to Example 2. From this, it is found that by using the specified (E) component of the present invention, a photosensitive resin composition excellent in dielectric properties, insulating reliability, developability, and flame retardancy can be obtained. Regarding the improvement in developability, it is possible that the melt viscosity of the unexposed photosensitive resin composition is reduced by adding the (E) component, and it is presumed that not only is the (E) component itself easily removed by alkali, but this also affects the improvement in developability.

[0095] In addition, in Comparative Examples 2, 4, and 6, the haze after lamination did not satisfy the specified conditions, and therefore the developability deteriorated. It can be seen that when fine particles are added as a low dielectric component, the haze becomes an index of developability.

[0096] Next, the Examples are compared. Example 3 is inferior to Example 2 in developability because it uses component (D) with a particle size exceeding 2 μm. Also, Example 6 is inferior to Example 5 in developability because it does not contain a heterocyclic compound (F), and Example 7 is inferior to Example 5 in developability because it does not contain a polymerizable compound (b) having an ethylenically unsaturated double bond with a molecular weight of 250 or less. Furthermore, Example 8 is inferior to Example 5 in developability and insulation reliability because it does not contain a blocked isocyanate (G).

[0097] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the spirit of the invention. [Industrial Applicability]

[0098] According to the present invention, it is possible to provide a photosensitive resin composition that can provide a transfer film that can be patterned by exposure and development, and a cured film pattern that is excellent in low dielectric, heat resistance, flame retardancy, and insulation properties. For example, the cured film pattern of the present invention can be widely used as a low dielectric material for high frequencies, and as a protective film or insulating film for wiring such as a coverlay in an FPC.

Claims

1. Ingredients below: (A) an alkali-soluble resin, (B) a polymerizable compound having an ethylenically unsaturated double bond, (C) a photopolymerization initiator, (D) Polyphenylene ether fine particles composed of a polymer having a relative dielectric constant of 2.8 or less at a frequency of 10 GHz, and having an average particle size of 2 μm or less and a maximum particle size of 20 μm or less, as measured by Method 1 described below; and (E) a flame retardant containing phosphorus or bromine and exhibiting solid properties at 30°C; A photosensitive resin composition comprising: The photosensitive resin composition has a haze of 15% or less, as measured by the following method 2. (Method 1): Using a laser diffraction / scattering type particle size distribution measuring device, the smaller particle size is taken as 0, and the particle size at 50% particle volume distribution (D50) is taken as the average particle size, and the particle size at 100% particle volume distribution (D100) is taken as the maximum particle size. (Method 2): The components other than the component (D) are added to a solvent and dissolved and mixed. After mixing, the component (D) is added and stirred for 5 hours to obtain a photosensitive resin composition preparation. The photosensitive resin composition preparation is uniformly applied to the surface of a temporary support film and dried at 95°C to form a photosensitive resin layer having a thickness of 25 μm. The prepared photosensitive resin layer is laminated on a glass substrate having a thickness of 1.1 mm using a hot roll laminator at a roll temperature of 95°C, an air pressure of 0.4 MPa, and a speed of 1.0 m / min to obtain a laminate consisting of a three-layer structure of temporary support film / photosensitive resin layer / glass substrate in order from the top. Thereafter, the temporary support film is peeled off, and the mixture is left to stand for 1 hour, and then the haze is measured using a haze meter according to a method corresponding to JIS K7136.

2. The photosensitive resin composition according to claim 1 , further comprising (F) a heterocyclic compound.

3. 3. The photosensitive resin composition according to claim 1, further comprising, as the component (B), at least one kind of compound (b) having a molecular weight of 250 or less.

4. The photosensitive resin composition according to any one of claims 1 to 3, further comprising (G) a blocked isocyanate compound.

5. A transfer film comprising a support and a photosensitive resin layer formed from the photosensitive resin composition according to any one of claims 1 to 4 and provided on the support.

6. The transfer film according to claim 5 , which is laminated on a substrate having wiring and is used as a wiring protective film or insulating film.

7. A resin pattern formed from an exposed and developed product of the transfer film according to claim 5 or 6.

8. A cured film pattern formed from a cured product of the resin pattern according to claim 7.

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