Photosensitive resin composition, dry film, cured product, and printed wiring board

Abstract

To provide a photosensitive resin composition capable of efficiently forming a cured product that has both excellent dielectric properties and resolution in a short time. Solution: In a photosensitive resin composition containing a polyphenylene ether resin, a first photopolymerization initiator, a second photopolymerization initiator, and a radical-reactive monomer, the weight average molecular weight of the polyphenylene ether resin is adjusted to 250 to 10,000, the first photopolymerization initiator and the second photopolymerization initiator are different from each other, and the second photopolymerization initiator is set to a photopolymerization initiator having a 10-hour half-life temperature of 100 to 200°C.

Description

Technical Field

[0001] This invention relates to photosensitive resin compositions, and more particularly to photosensitive resin compositions suitable for forming insulating layers. Furthermore, this invention relates to a dry film having a resin layer composed of the photosensitive resin composition, a cured product of the resin layer of the photosensitive resin composition or the dry film, and a printed wiring board having the cured product. Background Technology

[0002] In recent years, with the increasing volume of information processing, the demand for miniaturized and high-density circuit wiring in circuit boards widely used in various electronic devices has increased to achieve miniaturization and high functionality. Furthermore, the widespread adoption of high-capacity, high-speed communication systems such as 5G and millimeter-wave radar for automotive ADAS (Advanced Driver Assistance Systems) has led to a continuous trend towards higher frequency signals in electronic devices. Therefore, the insulating film of the rewiring layer in the latest high-density semiconductor packages requires properties such as high resolution corresponding to the miniaturization and high integration, low dielectric constant for suppressing transmission losses in high-frequency bands, and excellent dielectric characteristics such as a low dielectric loss tangent.

[0003] Here, thermosetting resins or photosensitive resins are typically used as materials for forming the insulating film. However, thermosetting resins are advantageous in terms of dielectric properties because they facilitate the reduction of polar groups, making it easier to achieve a low dielectric constant in the cured insulating film. On the other hand, they have limitations in resolution, such as the long processing time required for laser processing during via formation and the need to minimize the via diameter. Photosensitive resins, on the other hand, allow for rapid via formation vias via photolithography, offering advantages in resolution. However, they also have limitations in dielectric properties because the resin composition needs to contain a certain amount of polar groups for alkaline development.

[0004] To address this problem, for example, Patent Document 1 proposes a technique that combines a polyphenylene ether having a specific weight-average molecular weight and synthesized under specific conditions with other polyphenylene ethers synthesized under other conditions and combines them with a photosensitive resin composition, thereby imparting excellent dielectric properties and development contrast to the insulating film as its cured product.

[0005] However, there is a growing demand for further miniaturization and high density of circuit wiring. To address this trend, there is a anticipated need for resin compositions that can efficiently form cured products that combine excellent dielectric properties and resolution in a short time.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent document 1: Japanese Patent Application Publication No. 2023-37449. Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] Under such circumstances, as an ongoing technical challenge, there exists a resin composition that can efficiently form a cured product that combines excellent dielectric properties and resolution in a short time.

[0011] Therefore, an object of the present invention is to provide a photosensitive resin composition capable of efficiently forming a cured material with both excellent dielectric properties and resolution in a short time. Furthermore, another object of the present invention is to provide a dry film having a resin layer composed of such a photosensitive resin composition, a cured product of the resin layer of the photosensitive resin composition or the dry film, and a printed wiring board having the cured product.

[0012] Methods for solving problems

[0013] The inventors conducted in-depth research and obtained the following insights: In a photosensitive resin composition comprising polyphenylene ether resin, a first photopolymerization initiator, a second photopolymerization initiator, and a free radical reactive monomer, by adjusting the weight-average molecular weight of the polyphenylene ether resin to 250–10,000, setting the first photopolymerization initiator to an oxime ester-based photopolymerization initiator, and setting the second photopolymerization initiator to a photopolymerization initiator having a 10-hour half-life temperature in the temperature range of 100–200°C, the aforementioned problems can be solved. In other words, the main points of this invention are as follows.

[0014] [1] A photosensitive resin composition comprising a polyphenylene ether resin, a first photopolymerization initiator, a second photopolymerization initiator, and a free radical reactive monomer, characterized in that, The aforementioned polyphenylene ether resin has a weight-average molecular weight of 250–10,000. The aforementioned first photopolymerization initiator and second photopolymerization initiator are different from each other. The aforementioned second photopolymerization initiator is a photopolymerization initiator with a 10-hour half-life temperature in the temperature range of 100-200°C.

[0015] [2] The photosensitive resin composition according to [1] further comprises a resin with a weight-average molecular weight of more than 10,000.

[0016] [3] According to the photosensitive resin composition of [2], wherein the aforementioned resin with a weight average molecular weight of more than 10,000 comprises a resin having free radical polymerizable groups.

[0017] [4] According to the photosensitive resin composition of [3], wherein the resin having free radical polymerizable groups comprises branched polyphenylene ether.

[0018] [5] A dry film, wherein the dry film has a first film and a resin layer formed on at least one side of the first film, which is composed of a photosensitive resin composition of any one of [1] to [4].

[0019] [6] A cured product, wherein the cured product is formed by curing the resin layer of any one of the photosensitive resin compositions of [1] to [4] or the dry film of [5].

[0020] [7] A printed wiring board, wherein the printed wiring board has the cured material described in [6].

[0021] Invention Effects

[0022] According to the present invention, a photosensitive resin composition capable of efficiently forming a cured material with both excellent dielectric properties and resolution in a short time can be provided. Furthermore, according to the present invention, a dry film having a resin layer composed of such a photosensitive resin composition, a cured product of the resin layer of the photosensitive resin composition or the dry film, and a printed wiring board having the cured product can be provided.

[0023] [Photosensitive Resin Composition]

[0024] According to one aspect of the present invention, a photosensitive resin composition (hereinafter also referred to as "the photosensitive resin composition of the present invention") is provided. The photosensitive resin composition of the present invention is preferably used for the formation of insulating layers in printed wiring boards, etc. In particular, the photosensitive resin composition of the present invention can be readily cured (e.g., an insulating layer) within a short time by irradiation with light such as ultraviolet light, and therefore can be preferably used for the efficient manufacture of cured products and printed wiring boards having the cured products.

[0025] The photosensitive resin composition of the present invention comprises a polyphenylene ether resin, a first photopolymerization initiator, a second photopolymerization initiator, and a free radical reactive monomer as essential components. The components of the photosensitive resin composition of the present invention will be described in detail below. It should be noted that commercially available products or appropriately synthesized substances can be used for each component.

[0026] (Polyphenylene ether resin)

[0027] The photosensitive resin composition of the present invention comprises a polyphenylene ether resin. Due to the high symmetry of its molecular structure, the polyphenylene ether resin enables the cured photosensitive resin composition to achieve low dielectric properties. Furthermore, the polyphenylene ether resin is densely packed due to the interaction of its ring structures, resulting in a high crosslinking density. Therefore, by including the polyphenylene ether resin in the photosensitive resin composition, the water absorption rate of the cured photosensitive resin composition is suppressed, thus achieving low dielectric properties.

[0028] There are no particular limitations on the polyphenylene ether resin used, as long as it contains phenylene ether units as repeating structural units; any conventionally known type can be used. Specifically, examples of polyphenylene ether resins include polymers whose main chain has constituent units represented by the following structural formula (preferably polymers in which the structural units represented by the following structural formula account for 90 mol% or more of all constituent units except for the terminal groups). The polyphenylene ether resin can be a homopolymer or a copolymer. Furthermore, a single polyphenylene ether resin can be used, or two or more can be used in combination.

[0029] [Chemical Formula 1]

[0030] [In the formula, the two R's] a Each independently represents a hydrogen atom, halogen atom, primary or secondary alkyl group, aryl group, aminoalkyl group, haloalkyl group, alkyl group, or haloalkyloxy group. Two Rs b Each can be independently represented by a hydrogen atom, halogen atom, primary or secondary alkyl group, aryl group, haloalkyl group, alkyl group, or haloalkyl group.

[0031] Among them, two R a Not all of them will become hydrogen atoms.

[0032] As R a and R b Each of these is preferably a hydrogen atom, a primary or secondary alkyl group, or an aryl group. Examples of primary alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, isopentyl, 2-methylbutyl, 2,3-dimethylbutyl, 2-, 3-, or 4-methylpentyl or heptyl. Examples of secondary alkyl groups include isopropyl, sec-butyl, or 1-ethylpropyl. In particular, R... a Preferably, it is a primary alkyl group, secondary alkyl group, or phenyl group having 1 to 4 carbon atoms. Additionally, R... b Preferably, hydrogen atoms. As described above, by means of non-highly polar substituents in the polyphenylene ether resin, the dielectric properties of the photosensitive resin composition of the present invention are further improved (i.e., the photosensitive resin composition of the present invention is further improved by low dielectric loss tangent).

[0033] Examples of homopolymers of polyphenylene ether resins include polymers of 2,6-dialkylphenylene ethers such as poly(2,6-dimethyl-1,4-phenylene) ether, poly(2,6-diethyl-1,4-phenylene ether), poly(2,6-dipropyl-1,4-phenylene ether), poly(2-ethyl-6-methyl-1,4-phenylene ether), and poly(2-methyl-6-propyl-1,4-phenylene ether). In addition, examples of copolymers of polyphenylene ether resins include 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymers, 2,6-dimethylphenol / 2,3,6-triethylphenol copolymers, 2,6-diethylphenol / 2,3,6-trimethylphenol copolymers, 2,6-dipropylphenol / 2,3,6-trimethylphenol copolymers, and 2,6-dialkylphenol / 2,3,6-trialkylphenol copolymers, as well as graft copolymers formed by grafting poly(2,6-dimethyl-1,4-phenylene ether) with styrene, and graft copolymers formed by grafting 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymers with styrene.

[0034] The weight-average molecular weight of the polyphenylene ether resin is 250 to 10,000, preferably 500 to 8,000. By including the polyphenylene ether resin with a weight-average molecular weight within the above range in the photosensitive resin composition of the present invention, after exposure, the unexposed portion dissolves in the developer, but the molecular weight of the exposed portion increases, resulting in reduced solubility in the developer, thus appropriately creating a difference in solubility contrast.

[0035] In this invention, the molecular weights (number average molecular weight, weight average molecular weight) of various resin components, represented by polyphenylene ether resin, can be determined using gel permeation chromatography (GPC) in the form of polystyrene-converted molecular weight.

[0036] In polyphenylene ether resins, the main chain structure can have any structure, either linear or branched. Branched polyphenylene ether resins (hereinafter also referred to as "branched polyphenylene ethers") are described below.

[0037] Commercially available polyphenylene ether resins include, for example, Noryl (trademark) SA9000 and Noryl (trademark) SA90 (both manufactured by SHPP Japan LLC).

[0038] The content of polyphenylene ether resin with a weight average molecular weight of 250 to 10,000 in the photosensitive resin composition of the present invention is not particularly limited as long as the effects of the present invention are achieved. Relative to the total mass of the photosensitive resin composition, calculated in terms of solid content, it is preferably 10 to 80% by mass, more preferably 20 to 70% by mass. By making the content of polyphenylene ether resin with a weight average molecular weight of 250 to 10,000 10% by mass or more, a cured product with both good resolution and low dielectric properties can be formed by exposure. On the other hand, by making the content of polyphenylene ether resin with a weight average molecular weight of 250 to 10,000 80% by mass or less, good developability can be exhibited during exposure.

[0039] (First photopolymerization initiator)

[0040] In the photosensitive resin composition of the present invention, the first photopolymerization initiator containing the first photopolymerization initiator is not particularly limited as long as it is different from the second photopolymerization initiator described later. Examples include α-aminoacetophenone-based photopolymerization initiators such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butane-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholino)phenyl]-1-butanone, and N,N-dimethylaminoacetophenone; and 1-hydroxy-cyclohexylphenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl... Hydroxyacetophenone-based photopolymerization initiators include 2-hydroxy-1-propane-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propanoyl)-benzyl]phenyl}-2-methyl-propane-1-one, and 2-hydroxy-2-methyl-1-phenylpropane-1-one; bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and bis-(2 Acylphosphine oxide photoinitiators such as (6-dimethoxybenzoyl)-2,5-dimethylbenzylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,6-dimethoxybenzoyl diphenylphosphine oxide, 2,6-dichlorobenzoyl diphenylphosphine oxide, methyl 2,4,6-trimethylbenzoylphenylphosphine acid, ethyl 2,4,6-trimethylbenzoylphenylphosphine acid, 2-methylbenzoyl diphenylphosphine oxide, isopropyl terpentylphenylphosphine acid, and 2,4,6-trimethylbenzoyl diphenylphosphine oxide; benzoin-based photoinitiators such as benzoin, benzoyl, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether; benzoyl alkyl ether-based photoinitiators. Photopolymerization initiators; benzophenone-based photopolymerization initiators such as benzophenone, p-methylbenzophenone, michidone, methylbenzophenone, 4,4'-dichlorobenzophenone, and 4,4'-bis(diethylamino)benzophenone; acetophenone-based photopolymerization initiators such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone; thioxanone-based photopolymerization initiators such as thioxanone, 2-ethylthioxanone, 2-isopropylthioxanone, 2,4-dimethylthioxanone, 2,4-diethylthioxanone, 2-chlorothioxanone, and 2,4-diisopropylthioxanone.Anthraquinone-based photopolymerization initiators, including anthraquinones, chloroanthraquinones, 2-methylanthraquinones, 2-ethylanthraquinones, 2-tert-butylanthraquinones, 1-chloroanthraquinones, 2-pentylanthraquinones, and 2-aminoanthraquinones; ketal-based photopolymerization initiators, including acetophenone dimethyl ketal and benzyl dimethyl ketal; benzoate-based photopolymerization initiators, including ethyl-4-dimethylaminobenzoate, 2-(dimethylamino)ethylbenzoate, and ethyl p-dimethylbenzoate; 1,2-octanedione, 1-[4-(phenylthio)phenyl]-, 2-(o-benzoyl oxime), ethyl ketone, and 1-[9-ethyl [-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-, 1-(o-acetyloxime) and other oxime ester photopolymerization initiators; bis(n5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrolo-1-yl)phenyl)titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyrrolo-1-yl)ethyl)phenyl]titanium and other diacene-based photopolymerization initiators; phenyl disulfide 2-nitrofluorene, butylin, anisolein ether, azobisisobutyronitrile, tetramethylthiuram disulfide, etc. The first photopolymerization initiator can be used alone or in combination with two or more.

[0041] The first photopolymerization initiator preferably includes an oxime ester-based photopolymerization initiator or an acylphosphine oxide-based photopolymerization initiator. Examples of commercially available oxime ester-based photopolymerization initiators include Irgacure OXE02 (acetone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(o-acetyloxime)) (manufactured by BASF Japan Ltd.). Examples of commercially available acylphosphine oxide-based photopolymerization initiators include Omnirad TPO-L (ethyl 2,4,6-trimethylbenzoylphenylphosphonate) (manufactured by IGM Resins BV).

[0042] The content of the first photopolymerization initiator in the photosensitive resin composition of the present invention is not particularly limited as long as the effects of the present invention are achieved. Relative to the total mass of the photosensitive resin composition, in terms of solid content, it is preferably 0.1 to 15% by mass, more preferably 1 to 10%. By making the content of the first photopolymerization initiator 0.1% by mass or more and 15% by mass or less, the reactivity of the photopolymerizable components contained in the photosensitive resin composition can be improved.

[0043] (Second photopolymerization initiator)

[0044] The photosensitive resin composition of the present invention comprises a second photopolymerization initiator. The second photopolymerization initiator is a photopolymerization initiator having a 10-hour half-life temperature in the temperature range of 100–200°C, preferably in the temperature range of 120–180°C. As for the photopolymerization initiator having a 10-hour half-life temperature in the temperature range of 100–200°C, there is no particular limitation as long as the effects of the present invention are achieved; it is preferable to include a peroxide structure (-OO-). The second photopolymerization initiator can be used alone or in combination of two or more.

[0045] Examples of photopolymerization initiators with a 10-hour half-life temperature in the temperature range of 100–200 °C include 3,3,4,4-tetra(tert-butylperoxycarbonyl)benzophenone and 2-(1-tert-butylperoxy-1-methylethyl)-9H-thioxanthone-9-one.

[0046] The content of the second photopolymerization initiator in the photosensitive resin composition of the present invention is not particularly limited as long as the effects of the present invention are achieved. It is preferably 1 to 10% by mass relative to the total mass of the photosensitive resin composition, converted to solid content. By making the content of the second photopolymerization initiator 1% by mass or more and 10% by mass or less, the reactivity of the photopolymerizable components contained in the photosensitive resin composition can be improved.

[0047] It can also be used in combination with the first and second photopolymerization initiators mentioned above, employing photoinitiation aids or sensitizers. Examples of photoinitiation aids or sensitizers include benzoin compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, and xanthone compounds. Thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone are particularly preferred. One photoinitiation aid and one sensitizer can be used alone, or two or more can be used in combination.

[0048] The photosensitive resin composition of the present invention, by using the first and second photopolymerization initiators that are different from each other as described above, can impart excellent dielectric properties and resolution to the cured product of the photosensitive resin composition. The reason why the cured product of the photosensitive resin composition can be endowed with excellent dielectric properties and resolution by using the first and second photopolymerization initiators that are different from each other is not yet certain, but it is inferred as follows. Generally, in order to obtain high resolution (e.g., to achieve a small aperture), exposure is required until developability is achieved, suppressing the reaction around the exposed portion caused by halo (halos sometimes occur when the absorbance of the photosensitive resin composition is low and the amount of light reaching its bottom is excessive). Therefore, in order to exhibit developability with less light, it is necessary to use a photopolymerization initiator that promotes curing by exposure and to adjust the components so that light can properly pass through the bottom of the photosensitive resin composition. However, components adjusted to ensure proper light transmission to the bottom of the photosensitive resin composition can become unreacted if unhelpful components (such as UV absorbers or excessive photopolymerization initiators) are added, sometimes negatively impacting the properties of the cured product. Furthermore, excessive use of photopolymerization initiators can lead to unreacted portions due to exposure, thus limiting their application. Therefore, it is believed that combining a photopolymerization initiator with a 10-hour half-life temperature in the 100–200°C range (i.e., a second photopolymerization initiator) that exhibits photosensitivity and thermal decomposition properties with a first photopolymerization initiator different from the second photopolymerization initiator can appropriately eliminate the aforementioned trade-offs. Furthermore, by using a photopolymerization initiator that generates free radicals through heat, the curing reactivity during post-curing is improved, and a lower dielectric constant in the cured product can be expected. As a result, it is believed that excellent dielectric properties and resolution can be achieved in the cured product.

[0049] (Free radical reactive monomers)

[0050] The photosensitive resin composition of the present invention comprises a free radical reactive monomer. In this specification, "free radical reactive" refers to a monomer having a free radical polymerizable group. Any monomer known conventionally can be used as the free radical reactive monomer. Furthermore, as the free radical polymerizable group, a group having an unsaturated carbon bond is preferred, such as vinyl, allyl, maleimide, acryloyl, methacryl, styrene, etc. By including a free radical reactive monomer in the photosensitive resin composition of the present invention, the concentration of free radical polymerizable groups in the photosensitive resin composition is increased, and the crosslinking density is increased. As a result, development contrast can be easily imparted during exposure.

[0051] Examples of free radical reactive monomers include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and other (meth)acrylic acid and its esters; (meth)acrylamide, isopropylacrylamide, and other (meth)acrylamide derivatives; vinyl chloride, vinylidene chloride, vinyl acetate, methyl vinyl ether, styrene, divinylbenzene, (meth)acrylonitrile, and other ethylene monomers; compounds with unsaturated double bonds such as isoprene; multifunctional monomers such as pentaerythritol tri(meth)acrylate; and (meth)acryloylmorpholine. Free radical reactive monomers can be used alone or in combination of two or more.

[0052] As a free radical reactive monomer, monomers having two or more vinyl groups within their molecules are preferred. Examples of monomers having two or more vinyl groups within their molecules include triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, and diallyl isophthalate. By having two or more vinyl groups in the free radical reactive monomer, three-dimensional crosslinking is formed in the cured photosensitive resin composition of the present invention, thereby improving its mechanical properties. Furthermore, as a free radical reactive monomer, monomers having a triazine ring within their molecules are preferred. That is, as a free radical reactive monomer, monomers having a triazine ring within their molecules and having two or more vinyl groups are particularly preferred. By including highly reactive free radical reactive monomers, especially monomers having two or more vinyl groups within their molecules and having a triazine ring, the photosensitive resin composition of the present invention can improve the dielectric properties when exposing the photosensitive resin composition of the present invention to light.

[0053] Commercially available free radical reactive monomers include, for example, L-DAIC (manufactured by Shikoku Chemical Industry Co., Ltd.) and TAIC (trademark) (triallyl isocyanurate, manufactured by Mitsubishi Chemical Co., Ltd.).

[0054] The content of the free radical reactive monomer in the photosensitive resin composition of the present invention is not particularly limited as long as the effects of the present invention are achieved. Relative to the total mass of the photosensitive resin composition, in terms of solid content, it is preferably 5 to 50% by mass, more preferably 10 to 40% by mass. By having a free radical reactive monomer content of 5% by mass or more, the crosslinking density in the above-mentioned photosensitive resin composition is sufficiently increased, resulting in excellent development contrast during exposure. On the other hand, by making the free radical reactive monomer content 50% by mass or less, the photosensitive resin composition can be cured without hindering the effect of low dielectricization.

[0055] (Resins with a weight-average molecular weight exceeding 10,000)

[0056] The photosensitive resin composition of the present invention may further comprise a resin with a weight-average molecular weight exceeding 10,000. By comprising a resin with a weight-average molecular weight exceeding 10,000, the photosensitive resin composition of the present invention can mitigate residual stress caused by exposure, thereby suppressing the occurrence of cracks in the cured product.

[0057] As the resin with a weight average molecular weight exceeding 10,000, any conventionally known resin can be used, such as polyphenylene ether resin with a weight average molecular weight exceeding 10,000, and other resins. As the resin with a polymeric average molecular weight exceeding 10,000, it is preferable to include a resin having a free radical polymerizable group, and more preferably, it is preferable to include a polyphenylene ether resin with a polymeric average molecular weight exceeding 10,000. It should be noted that the free radical polymerizable group can be the free radical polymerizable group described in relation to the aforementioned free radical reactive monomer. A single resin with a weight average molecular weight exceeding 10,000 can be used, or two or more can be used in combination.

[0058] As a polyphenylene ether resin with a weight average molecular weight exceeding 10,000, the same resin as the aforementioned polyphenylene ether resin can be used, except that the weight average molecular weight exceeds 10,000, and branched polyphenylene ether is preferred.

[0059] Branched polyphenylene ethers are polyphenylene ether resins synthesized from phenolic raw materials containing hydrogen atoms at the ortho and para positions. Because these phenols have hydrogen atoms at the ortho position, ether bonds can form not only in situ and para positions but also at the ortho position during oxidative polymerization with phenols. Therefore, polyphenylene ether resins synthesized using such phenols as raw materials can form branched structures. Such branched polyphenylene ethers exhibit excellent solubility in solvents and excellent compatibility and reactivity with the components in photosensitive resin compositions.

[0060] Examples of branched polyphenylene ethers include, for instance, the polyphenylene ether resin disclosed in International Publication No. 2020 / 017570.

[0061] Branched polyphenylene ethers can be obtained by either (method 1) using phenols containing functional groups with unsaturated carbon bonds as raw material to synthesize polyphenylene ether resins, or (method 2) using phenols without functional groups with unsaturated carbon bonds as raw material to synthesize polyphenylene ether resins, and modifying the resulting polyphenylene ether resins to introduce functional groups with unsaturated carbon bonds into the polyphenylene ether resins.

[0062] Branched polyphenylene ethers can be mixtures of two or more polyphenylene ether resins with different types of raw material phenols.

[0063] The amount of functional groups with unsaturated carbon bonds in the branched polyphenylene ether is not particularly limited as long as the effects of the present invention are achieved. Preferably, it is an amount within a range that does not significantly alter the electrical properties of the polyphenylene ether structure and allows for the formation of an effective crosslinking structure. Specifically, the amount of functional groups with unsaturated carbon bonds, relative to the molar ratio of all monomers constituting the branched polyphenylene ether, is preferably 3% or more, more preferably 6% or more, and further preferably 50% or less, more preferably 25% or less. By keeping the amount of functional groups with unsaturated carbon bonds in the polyphenylene ether resin within the above range, the amount of unreacted unsaturated carbon bonds during the curing of the resin composition layer can be reduced, increasing the crosslinking density and improving the dielectric properties.

[0064] Furthermore, the higher the degree of branching in branched polyphenylene ethers, the more complex the entanglement of the molecular chains, resulting in a stronger and more robust coating film. Additionally, with a high degree of branching in the polyphenylene ether, the interactions between the ring structures in the polyphenylene ether resin within the photosensitive resin composition before curing are mitigated, increasing the degree of freedom of the polyphenylene ether resin molecular chains. This leads to increased reactivity and a higher reactivity rate of the polyphenylene ether resin. Consequently, a decrease in the dielectric constant of the resin composition or a stronger and more robust coating film can be expected.

[0065] In this invention, the branched structure (degree of branching) of branched polyphenylene ether can be confirmed by the following analytical steps.

[0066] (Analysis steps)

[0067] Chloroform solutions of branched polyphenylene ether were prepared at concentrations of 0.1 mg / mL, 0.15 mg / mL, 0.2 mg / mL, and 0.25 mg / mL. A graph showing the correlation between refractive index difference and concentration was plotted while the solution was fed at a rate of 0.5 mL / min, and the refractive index increment dn / dc was calculated from the slope. Then, the absolute molecular weight was determined under the apparatus operating conditions described below. Referring to the chromatograms from the RI (differential refractive index) detector and the MALS (multi-angle light scattering) detector, a regression line based on the least squares method was obtained from the logarithmic plot (conformation diagram) of absolute molecular weight versus radius of rotation, and its slope was calculated.

[0068] (Measurement conditions)

[0069] Device name: HLC-8320GPC (manufactured by Tosoh Corporation).

[0070] Mobile phase: chloroform.

[0071] Chromatographic column: TSKgel (registered trademark) guard column. HR -H+TSKgel (registered trademark) GMH HR-H (2 sticks) + TSKgel (registered trademark) G2500H HR (All are manufactured by Tosoh Corporation).

[0072] Flow rate: 0.6 mL / min.

[0073] Detectors: Multi-angle static light scattering (MALS) detector DAWN (registered trademark) HELEOS (registered trademark) + RI detector Optilab (registered trademark) rEX (wavelength 254nm) (all manufactured by WYATT TECHNOLOGY).

[0074] Sample concentration: 0.5 mg / mL.

[0075] Sample solvent: Same as mobile phase. Dissolve 5 mg of sample in 10 mL of mobile phase.

[0076] Injection volume: 200μL.

[0077] Filter: 0.45μm.

[0078] Standard reagent (STD): Standard polystyrene with a molecular weight of 37,900.

[0079] Standard concentration: 1.5 mg / mL.

[0080] Standard solvent: same as mobile phase. Dissolve 15 mg of sample in 10 mL of mobile phase.

[0081] Analysis time: 100 minutes.

[0082] In resins with the same absolute molecular weight, the higher the degree of branching of the polymer chains, the smaller the distance from the center of gravity to each chain segment (radius of gyration). Therefore, the slope calculated from the logarithmic graph of absolute molecular weight versus radius of gyration obtained by GPC-MALS indicates the degree of branching of branched polyphenylene ethers; the smaller the slope, the higher the degree of branching. That is, the smaller the slope calculated from the above conformational diagram, the more branches the branched polyphenylene ether has; the larger the slope, the fewer branches the branched polyphenylene ether has.

[0083] In branched polyphenylene ethers, the slope is preferably less than 0.6, more preferably less than 0.50, and even more preferably less than 0.40. When the slope is within the above range, the branched polyphenylene ether is considered to have sufficient branching. It should be noted that the lower limit of the slope is not particularly limited, and for example, it can be 0.05 or more, or 0.20 or more.

[0084] Other commonly known resins include isocyanate compounds, capped isocyanate compounds, amino resins, maleimide compounds, bismaleimide compounds, benzoxazine resins, carbodiimide resins, cyclic carbonate compounds, epoxy resins, oxetane compounds, cyclic sulfur resins, phenoxy resins, phenolic resins, polyvinyl alcohol acetal resins, polyamide resins, polyamide-imide resins, butadiene resins, and various copolymers.

[0085] The weight-average molecular weight of resins with a weight-average molecular weight exceeding 10,000 is preferably 15,000 to 100,000, and more preferably 20,000 to 80,000.

[0086] When the photosensitive resin composition of the present invention contains a resin with a weight-average molecular weight exceeding 10,000, its content is not particularly limited as long as the effects of the present invention are achieved. Relative to the total mass of the photosensitive resin composition, in terms of solid content, it is preferably 2 to 25% by mass, more preferably 3 to 20% by mass. By making the content of the resin with a weight-average molecular weight exceeding 10,000 2% by mass or more, it is expected to alleviate the residual stress caused by exposure. On the other hand, by making the content of the resin with a weight-average molecular weight exceeding 10,000 25% by mass or less, it is expected to achieve both the effects of alleviating the residual stress caused by exposure and improving solubility in the developer.

[0087] (Inorganic filler material)

[0088] The photosensitive resin composition of the present invention may further comprise an inorganic filler. Known inorganic fillers can be used as fillers, with barium sulfate, spherical silica, hydrotalcite, and talc being preferred. One inorganic filler may be used alone, or two or more may be used in combination. By including an inorganic filler in the photosensitive resin composition, the physical strength of the photosensitive resin composition and its cured product can be improved.

[0089] Spherical silica is particularly preferred as an inorganic filler material. Any spherical silica that can be used as a filler material for electronic applications can be used. The shape of the spherical silica is simply spherical and is not limited to a sphere. Examples of preferred spherical silica include those with a sphericity of 0.8 or higher as measured.

[0090] The sphericity of spherical silica is determined as follows: First, a photograph of the spherical silica is taken using a scanning electron microscope (SEM). The sphericity is then determined based on the area and perimeter of the particles observed in the photograph, using the formula (sphericity) = {4π × (area) ÷ (perimeter)}. 2The calculated value is then used for further calculations. Specifically, the average value measured from 100 particles using an image processing device can be employed.

[0091] The average particle size of the spherical silica is not particularly limited as long as the effects of the present invention are achieved, but is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm, and even more preferably 0.3 to 1 μm. The average particle size of the spherical silica refers to the average particle size (D50) including not only the particle size of primary particles but also the particle size of secondary particles (aggregates), and is the D50 value determined by laser diffraction. As a measuring device using laser diffraction, the Microtrac MT3300EXII manufactured by MicrotracBEL Corp. can be cited as an example. It should be noted that the maximum particle size (D100) and particle size (D10) can also be measured using the same device. Furthermore, the average particle size of the spherical silica contained in the photosensitive resin composition of the present invention refers to the value obtained by measuring the spherical silica as described above before adjusting (preparatory stirring, mixing) the photosensitive resin composition to form the insulating layer.

[0092] Commercially available spherical silica includes, for example, Admanano YA 050C-HHL (manufactured by Admatechs Co., Ltd.).

[0093] The aforementioned inorganic filler materials can be surface-treated. Examples of surface treatments include those using coupling agents and alumina treatment, which do not introduce organic groups. There are no particular limitations on the surface treatment method for inorganic filler materials; any known and commonly used method can be used. The surface of the inorganic filler material can be treated with surface treatment agents having curing reactive groups, such as coupling agents that have curing reactive groups as organic groups.

[0094] Surface treatment is preferably performed using a coupling agent. As coupling agents, silane-based, titanate-based, aluminate-based, and zirconate aluminate-based coupling agents can be used. Among these, silane-based coupling agents are preferred. Examples of such silane-based coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, N-(2-aminomethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-anilinepropyltrimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane. A single coupling agent can be used, or two or more can be used in combination.

[0095] The content of inorganic filler in the photosensitive resin composition is not particularly limited as long as the effects of the present invention are achieved. For example, it can be set to 10 to 60% by mass relative to the total mass of the photosensitive resin composition, in terms of solid content. By keeping the content of inorganic filler within the above range, excessive increase in the viscosity of the photosensitive resin composition can be suppressed, good coatability and moldability can be maintained, and the cured photosensitive resin composition can have sufficient strength.

[0096] (Organic solvent)

[0097] Organic solvents may be included in the photosensitive resin composition for purposes such as its preparation, viscosity adjustment when coating the photosensitive resin composition onto a substrate or film to form a resin layer. As organic solvents, commonly used organic solvents include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as anisole, cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, diethylene glycol monomethyl ether acetate, and tripropylene glycol monomethyl ether; esters such as ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbons such as octane and decane; and petroleum-based solvents such as petroleum ether, petroleum naphtha, and solvent naphtha. One organic solvent can be used alone, or two or more can be used in combination.

[0098] The evaporation and drying of organic solvents can be carried out using hot air circulating drying ovens, IR ovens (infrared heating ovens), hot plates, convection ovens, etc. (using a heat source with a heat source that utilizes steam to heat the air, and using a method of hot air convection contact within the dryer and a method of blowing the support body through nozzles).

[0099] (Other ingredients)

[0100] The photosensitive resin composition can be further formulated with, as needed, photoinitiators, cyanate compounds, mercapto compounds, urethane esterification catalysts, thixotropic agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, copper inhibitors, antioxidants, rust inhibitors, organobentonite, montmorillonite, and other tackifiers; at least one of silicone-based, fluorine-based, and polymer-based defoamers and leveling agents; imidazole-based, thiazole-based, and triazole-based silane coupling agents; phosphines; phosphate derivatives; phosphazene compounds, and other phosphorus compounds, and other flame retardants. These are substances known to be used in the field of electronic materials.

[0101] The photosensitive resin composition of the present invention can be used as a liquid or by dry film formation as described later. Furthermore, when used as a liquid, it can be a single liquid or two or more liquids.

[0102] [Dry film]

[0103] According to another aspect of the present invention, a dry film (hereinafter also referred to as "the dry film of the present invention") is provided, having a first film and a resin layer formed on the first film, which is composed of the photosensitive resin composition of the present invention. The first film in the dry film of the present invention refers to a film that is at least bonded to the resin layer when integrally formed by lamination on a substrate such as a substrate in contact with the resin layer formed on the dry film by the above-described photosensitive resin composition through heating or the like. The first film can be peeled off from the resin layer in a post-lamination process. In particular, the dry film of the present invention is preferably peeled off from the resin layer in a post-exposure process. During dry film formation, the photosensitive resin composition of the present invention is diluted with an organic solvent as described above to adjust to an appropriate viscosity, and coated on the first film with a uniform thickness using a comma coater, blade coater, lip coater, wire bar coater, extrusion coater, reverse coater, transfer roller coater, gravure coater, spray coater, etc., and typically dried at a temperature of 50–130°C for 1–30 minutes, thereby obtaining the film. There is no particular limitation on the coating thickness, but it is usually measured by the thickness of the dried film and can be appropriately selected in the range of 1 to 150 μm, preferably 5 to 60 μm.

[0104] As the first membrane, known membranes can be used without particular limitation, such as polyester membranes made of polyethylene terephthalate, polyethylene naphthalate, etc.; polyimide membranes; polyamide-imide membranes; polypropylene membranes; polystyrene membranes, etc., which are made of thermoplastic resins. Among these, polyester membranes are preferred from the viewpoints of heat resistance, mechanical strength, and operability. In addition, laminates of these membranes can also be used as the first membrane.

[0105] Furthermore, from the viewpoint of improving mechanical strength, the thermoplastic resin film described above is preferably a film stretched along a uniaxial direction or a biaxial direction.

[0106] The thickness of the first membrane is not particularly limited, but it can be set to, for example, 10 μm to 150 μm.

[0107] After forming the resin layer of the photosensitive resin composition of the present invention on the first film, for the purpose of further preventing dust from adhering to the surface of the resin layer, it is preferable to laminate a peelable second film on the surface of the resin layer. The second film refers to a film that is peeled off from the resin layer before lamination when integrally formed on a substrate such as a substrate by lamination with the resin layer side in contact with the dry film, by heating or the like. Examples of peelable second films include polyethylene film, polytetrafluoroethylene film, polypropylene film, and surface-treated paper, as long as the adhesive force between the resin layer and the second film is less than the adhesive force between the resin layer and the first film when the second film is peeled off.

[0108] The thickness of the second membrane is not particularly limited, but it can be set to, for example, 10 μm to 150 μm.

[0109] It should be noted that in the dry film of the present invention, a resin layer can be formed by coating the photosensitive resin composition of the present invention onto the second film and drying it, and then the first film is laminated on its surface. That is, either the first film or the second film can be used as the film on which the photosensitive resin composition of the present invention is coated when manufacturing the dry film of the present invention.

[0110] [cured material]

[0111] According to another aspect of the present invention, a cured product (hereinafter also referred to as "the cured product of the present invention") obtained by curing the photosensitive resin composition of the present invention or the resin layer of the dry film of the present invention is provided. The cured product of the present invention has excellent dielectric properties and high resolution.

[0112] Printed wiring board

[0113] According to another aspect of the present invention, a printed wiring board having the cured product of the present invention described above (hereinafter also referred to as "the printed wiring board of the present invention") is provided. That is, the printed wiring board of the present invention has a cured product obtained from the photosensitive resin composition of the present invention or the resin layer of the dry film of the present invention. As a method for manufacturing the printed wiring board of the present invention, for example, the photosensitive resin composition of the present invention is adjusted to a viscosity suitable for a coating method using an organic solvent as described above, and after being coated on a substrate by methods such as dip coating, flow coating, roller coating, bar coating, screen printing, curtain coating, etc., the organic solvent contained in the composition is evaporated and dried (temporarily dried) at a temperature of 60 to 100°C, thereby forming a surface-dried resin layer. Alternatively, in the case of a dry film, it is bonded to the substrate in such a way that the resin layer contacts the substrate using a laminator or the like, thereby forming a resin layer on the substrate.

[0114] Examples of substrates for the printed wiring board constituting the present invention include printed wiring boards with circuits pre-formed from copper, flexible printed wiring boards, and copper-clad laminates of all grades (FR-4, etc.) made of materials such as paper phenolic resin, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / non-woven epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluoropolymer-polyethylene-polyphenylene ether, and polyphenylene ether-cyanate ester. Other examples include metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, and wafer boards.

[0115] The lamination of the dry film onto the resin layer substrate is preferably performed under pressure and heat using a vacuum laminator or similar device. By using such a vacuum laminator, even when a circuit-formed substrate is used, the dry film adheres tightly to the substrate, preventing air bubbles from entering and improving the filling of recesses on the substrate surface. The pressure is preferably around 0.1 to 2.0 MPa, and the heating is preferably 40 to 120°C.

[0116] The evaporation drying of the photosensitive resin composition of the present invention after coating it onto a substrate can be performed using a hot air circulating drying oven, an IR oven, a hot plate, a convection oven, etc. (using a device with a heat source that uses steam to heat the air, a method of making hot air in the dryer convect and contact, and a method of blowing the support through a nozzle).

[0117] After forming a resin layer on a substrate, a photomask with a predetermined pattern is selectively exposed using active energy rays. Unexposed areas are then developed using an organic solvent to form a patterned cured material. In the case of a dry film, after exposure, a first film is peeled off from the dry film and developed, thereby forming a patterned cured material on the substrate. It should be noted that, as long as the properties are not compromised, the first film can be peeled off from the dry film before exposure, and the exposed resin layer can be exposed and developed. Furthermore, by irradiating the cured material with active energy rays followed by heat curing (e.g., 100–250°C), or by irradiating with active energy rays after heat curing, or by heat curing alone for final finishing (formal curing), a cured material with excellent adhesion, hardness, and other properties can be formed.

[0118] As for the exposure machine used in the aforementioned active energy ray irradiation, any device equipped with a high-pressure mercury lamp, ultra-high-pressure mercury lamp, metal halide lamp, or mercury short-arc lamp that irradiates ultraviolet light in the range of 350–450 nm is acceptable. Furthermore, a direct drawing device (e.g., a laser direct imaging device that directly draws images using laser light from CAD data from a computer) can also be used. The maximum wavelength of the lamp or laser source for the direct drawing machine should be in the range of 350–450 nm. The exposure dose used for image formation varies depending on the film thickness, but is typically set to 10–1000 mJ / cm². 2 The optimal value is set at 20–800 mJ / cm². 2 Within the range.

[0119] As for the above-mentioned developing methods, immersion, spraying, spraying, brushing, etc. can be used. As for the developing solution, a wide variety of organic solvents can be used, such as ester solvents, ketone solvents, alcohol solvents, amide solvents, ether solvents, hydrocarbon solvents, etc.

[0120] Example

[0121] The following examples illustrate the present invention in more detail, but the present invention is not limited to these examples. It should be noted that, unless otherwise specified, the numerical values ​​of each component in the examples represent parts by mass.

[0122] (Synthesis of branched polyphenylene ethers for resins with a weight average molecular weight exceeding 10,000)

[0123] Before preparing the photosensitive resin composition, a branched polyphenylene ether, which is one of its components, is synthesized according to the following steps.

[0124] 19.8 g of 2,6-dimethylphenol and 2.42 g of 2-allylphenol were added to a 500 mL separable flask and mixed. 261 g of toluene was then added to dissolve the resulting mixture. Further, 0.18 wt% of di-μ-hydroxy-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II)]chloride (Cu / TMEDA) and 0.16 wt% of tetramethylethylenediamine (TMEDA) were added to allow the mixture to react. Dry air was blown into the reaction solution at a flow rate of 75 mL / min, and the mixture was stirred at 200 rpm using four paddle stirrers while heating to 40 °C for a specified time to obtain a reaction solution containing polyphenylene ether. Then, heating of the obtained reaction solution was stopped, and the blowing of drying air was further stopped. The reaction solution was filtered to remove di-μ-hydroxy-bis[(N,N,N',N'-tetramethylethylenediamine)copper(II))chloride (Cu / TMEDA). A mixture of 1200 mL methanol, 4.0 mL concentrated hydrochloric acid, and 27.0 mL water was added to allow it to precipitate again. The precipitate was then filtered under reduced pressure, washed with methanol, and dried at 80 °C for 24 hours to obtain branched polyphenylene ether. The number-average molecular weight of the obtained branched polyphenylene ether was 13,000, the weight-average molecular weight was 45,000, and the slope calculated from the conformation diagram was 0.31. It should be noted that the number-average molecular weight and weight-average molecular weight of branched polyphenylene ethers are converted from polystyrene molecular weight. The assay apparatus used was a high-speed GPC device (HLC-8320GPC, manufactured by Tosoh Corporation), the eluent was chloroform, and the detector was an RI detector. The determination was performed by gel permeation chromatography (GPC).

[0125] [Preparation of photosensitive resin composition]

[0126] The components shown in Tables 1 and 2 below were mixed in the amounts (solid component amounts) indicated in the tables, and then mixed using a mixer to prepare the photosensitive resin compositions of Examples 1-16 and Comparative Examples 1-4. It should be noted that the details of each component in Tables 1 and 2 are as follows.

[0127] Polyphenylene ether resin: Noryl (trademark) SA9000 (weight average molecular weight: 1700, manufactured by SHPP JAPAN).

[0128] First photopolymerization initiator 1: Irgacure OXE02 (acetone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-, 1-(o-acetyl oxime)) (manufactured by BASF Japan).

[0129] First photopolymerization initiator 2: Omnirad TPO-L (manufactured by IGM Resins BV).

[0130] Second photopolymerization initiator: 2-(1-tert-butylperoxy-1-methylethyl)-9H-thioxanth-9-one (manufactured by Nippon Oil Co., Ltd.).

[0131] Free radical reactive monomer 1: L-DAIC (manufactured by Shikoku Chemical Industry Co., Ltd.).

[0132] Free radical reactive monomer 2: TAIC (trademark) (triallyl isocyanurate, manufactured by Mitsubishi Chemical Corporation).

[0133] Resin 1 with a weight average molecular weight exceeding 10,000: Branched polyphenylene ether (weight average molecular weight: 45,000) synthesized according to the above steps.

[0134] Resin 2 with a weight average molecular weight exceeding 10,000: LBR-305 (butadiene homopolymer, weight average molecular weight: 26,000, manufactured by Kuraray Co., Ltd.).

[0135] Inorganic filler material: Spherical silica slurry Admanano YA050C-HHL (40% by weight of solids, manufactured by Admatechs Co., Ltd.).

[0136] Thermosetting catalyst: Perbutyl (registered trademark) P40 (manufactured by Nippon Oil Co., Ltd.)

[0137] [Table 1]

[0138] [Table 2]

[0139] [Evaluation of Dry Film Preparation 1]

[0140] The photosensitive resin compositions of the examples and comparative examples obtained according to the above steps were coated onto a first film (polyethylene terephthalate film, film thickness: 50 μm) with a dried film thickness of 25 μm. The film was then heated at 80°C for 20 minutes to dry it and form a resin layer, thus producing dry films for evaluating dielectric properties.

[0141] [Evaluation of dielectric properties]

[0142] The resin layers of each dry film used for evaluating dielectric properties, prepared according to the above steps, are laminated onto copper foil at a temperature of 90°C. This process is repeated twice to form a resin layer with a thickness of 50 μm. Then, a contact exposure machine is used at 600 mJ / cm².2 Exposure was performed under the following conditions. Then, a UV transfer oven was used with a cumulative exposure of 1000 mJ / cm². 2 The product was subjected to ultraviolet irradiation under certain conditions and heated at 200°C for 60 minutes to form a cured product. The cured product peeled off from the copper foil was then dried at 105°C for 60 minutes to obtain the evaluation cured product. For each of the obtained evaluation cured products, the dielectric loss tangent was measured within 1 hour using an SPDR dielectric resonator and network analyzer manufactured by Agilent Technologies, Inc. at 25°C and 10 GHz. The dielectric loss tangent of the resin layer (i.e., the cured product of each photosensitive resin composition) of each dry film was evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2.

[0143] ◎: The dielectric loss tangent is below 0.005, indicating excellent dielectric properties.

[0144] ○: The dielectric loss tangent is below 0.006 and above 0.005, indicating excellent dielectric properties.

[0145] ×: The dielectric loss tangent exceeds 0.006, indicating insufficient dielectric properties.

[0146] [Evaluation of Dry Film Preparation 2]

[0147] The photosensitive resin compositions of the examples and comparative examples obtained according to the above steps were coated onto a first film (polyethylene terephthalate film, film thickness: 50 μm) with a dried film thickness of 10 μm. The film was then heated at 80°C for 20 minutes to dry it and form a resin layer, thus producing dry films for evaluating resolution and crack resistance.

[0148] [Fabrication of CZ Processing Substrate]

[0149] On both sides of a substrate (copper-clad laminate, CCL-HL832NX, Type A Series, 0.4mm thick, manufactured by Mitsubishi Gas Chemical Company, Inc.), a roughening agent (MEC etch BOND series CZ-8100, manufactured by MEC Co., Ltd.) was used to roughen the substrate to an etching depth of approximately 1μm, thus creating a CZ-treated substrate.

[0150] [Resolution Evaluation]

[0151] The resin layers of each dry film used for evaluating resolution and crack resistance, prepared according to the above steps, are laminated onto the CZ-treated substrate prepared according to the above steps at a temperature of 90°C. Then, through-holes with opening diameters of 10–30 μm (10 μm intervals) are formed using a projection exposure machine at 100 mJ / cm². 2 Exposure was performed under the specified conditions, followed by development with propylene glycol monomethyl acetate for 20 seconds to form through-holes. The formed through-holes were observed using an optical microscope (magnification: 2000x), and the resolution of the photosensitive resin composition constituting each dry film was evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2.

[0152] ○: Through-holes with an opening diameter of less than 20μm, free of developing residue.

[0153] ×: Through holes with an opening diameter of less than 20μm are not open or have development residue even though they are open.

[0154] [Evaluation of crack resistance]

[0155] Similar to the resolution evaluation described above, each dry film layer used for evaluation was laminated onto a CZ-processed substrate, and then through-holes were formed. The formed through-hole portions and their peripheries were observed using an optical microscope (magnification: 2000x), and the crack resistance of the photosensitive resin composition constituting each dry film was evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2.

[0156] ◎: There are no cracks in the through hole and its surrounding area.

[0157] ○: There is a crack at one point in the through hole or around the through hole.

[0158] ×: There are more than 2 cracks in the through hole or the area around the through hole.

[0159] As shown in Tables 1 and 2, the photosensitive resin compositions of Examples 1 to 16 exhibit excellent dielectric properties, thus enabling the formation of cured products with high resolution. Furthermore, the cured products formed from the photosensitive resin compositions of Examples 1 to 16 demonstrate high crack resistance. On the other hand, it can be seen that the photosensitive resin compositions of Comparative Examples 1 to 4 have poor resolution and cannot simultaneously achieve the excellent dielectric properties of the cured products.

Claims

1. A photosensitive resin composition comprising a polyphenylene ether resin, a first photopolymerization initiator, a second photopolymerization initiator, and a free radical reactive monomer, characterized in that, The polyphenylene ether resin has a weight-average molecular weight of 250–10000. The first photopolymerization initiator and the second photopolymerization initiator are different from each other. The second photopolymerization initiator is a photopolymerization initiator with a 10-hour half-life temperature in the temperature range of 100-200°C.

2. The photosensitive resin composition according to claim 1, wherein, The photosensitive resin composition further comprises a resin with a weight-average molecular weight of more than 10,000.

3. The photosensitive resin composition according to claim 2, wherein, The resin with a weight average molecular weight exceeding 10,000 includes resins having free radical polymerizable groups.

4. The photosensitive resin composition according to claim 3, wherein, The resin having free radical polymerizable groups comprises branched polyphenylene ether.

5. A dry film, wherein, The dry film has a first film and a resin layer formed on at least one side of the first film, which is composed of the photosensitive resin composition of claim 1.

6. A solidified material, wherein, The cured product is formed by curing the resin layer of the photosensitive resin composition of claim 1 or the dry film of claim 5.

7. A printed wiring board, wherein, The printed wiring board has the cured material as described in claim 6.

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