JP7810045B2 - Resin sheet, circuit board material using same, and method for cutting resin sheet - Google Patents

Description

The present invention relates to a resin sheet with excellent low dielectric properties, a circuit board material using the same, and a method for cutting the resin sheet.

Generally, the main circuit board materials used in electrical and electronic devices are copper-clad laminates (CCL), which are made by layering a resin-impregnated sheet (prepreg) on a substrate such as paper or glass, and then applying copper foil to the surface of the insulating plate obtained by heat and pressure treatment, or flexible printed circuit boards (FPC), which are made by forming an insulating adhesive layer on a base film and then laminating a conductive foil such as copper on top of that.

In recent years, communication frequencies have been increasing in order to improve the amount and speed of information transmission in electrical and electronic devices, and as a result, an increase in transmission loss (α) has become a major issue. The lower the value of this transmission loss (α), the less attenuation of the information signal, meaning that higher communication reliability can be ensured.
Since transmission loss (α) is proportional to frequency (f), α increases in high-frequency communications, leading to reduced reliability. One method for reducing transmission loss (α) is to reduce the dielectric loss tangent (tan δ), which is proportional to α, just like frequency (f). On the other hand, the relative dielectric constant is proportional to α as the square root. Therefore, in order to transmit communication signals at higher speeds, it is more effective to lower the dielectric loss tangent (tan δ) than to lower the relative dielectric constant, and materials with low dielectric loss tangents are in demand.

As a material having a low dielectric loss tangent, for example, a cyclic polyolefin resin having a specific structure has been proposed (Patent Documents 1 and 2).
Furthermore, an adhesive composition containing a crystalline acid-modified polyolefin (A) has been proposed as a technique for improving the adhesion of polyolefin resins having low dielectric properties to substrate films such as LCP (liquid crystal polymer) and metal substrates such as copper foil (Patent Document 3).

JP 2010-100843 A Japanese Patent Application Laid-Open No. 2020-117651 International Publication No. 2016/031342

Laser cutting is a well-known method for cutting resin sheets to the desired width and length. Generally, when a laser is applied to a material, if the material has absorption within the laser's oscillation wavelength range, the laser absorption within the material can be effectively utilized, allowing the material to be precisely processed.
However, the cyclic polyolefin resins described in Patent Documents 1 and 2 do not absorb light in the wavelength range of laser light, and therefore when a laser is applied to cut the resin, the laser passes through the sheet. Therefore, in order to cut a sheet made of such a resin with a laser, it has been necessary to use a special laser such as a YAG laser or an excimer laser.
Therefore, a light absorbing agent was added to a cyclic polyolefin resin to produce a sheet with absorption in the laser oscillation wavelength range. However, when an acid-modified resin was used as in Patent Document 3, the transparency of the resin sheet was sometimes reduced depending on the type of light absorbing agent.

The object of the present invention is to provide a resin sheet made of an acid-modified cyclic polyolefin resin that can be cut using a general-purpose laser and has good transparency, as well as a circuit board material made from the same.

The present invention has the following features.
[1] A resin sheet comprising a resin composition containing an acid-modified cyclic polyolefin resin (A) and a light absorber (B) having a maximum absorbance of 5% or more at a wavelength of 9.4 to 10.6 μm and having substantially no reactive functional groups in the molecule.
[2] The resin sheet according to the above [1], wherein the acid-modified cyclic polyolefin resin (A) is a resin having an alicyclic structure in a side chain of a polyolefin.
[3] The resin sheet according to the above [1] or [2], wherein the acid-modified cyclic polyolefin resin (A) is a resin having an alicyclic structure in the main chain of the polymer.
[4] The resin sheet according to any one of [1] to [3] above, wherein the acid-modified cyclic polyolefin resin (A) is a cyclic polyolefin containing at least one hydrogenated aromatic vinyl polymer block unit and at least one hydrogenated conjugated diene polymer block unit modified with an unsaturated carboxylic acid and/or an anhydride thereof.
[5] The resin sheet according to any one of the above [1] to [4], wherein the light absorber (B) is at least one selected from the group consisting of thioxanthone-based compounds, benzophenone-based compounds, acetophenone-based compounds, phosphorus-based compounds, and benzotriazole-based compounds.
[6] The resin sheet according to any one of the above [1] to [5], wherein the 10% weight loss temperature of the light absorber (B) is 165°C or higher.
[7] A circuit board material obtained by laminating an insulating layer made of the resin sheet according to any one of [1] to [6] above and a conductor.
[8] A method for cutting a resin sheet, comprising irradiating a resin sheet made of a resin composition containing an acid-modified cyclic polyolefin resin (A) and a light absorber (B) having a maximum absorbance of 5% or more at a wavelength of 9.4 to 10.6 μm and having substantially no reactive functional groups in the molecule with far-infrared laser light.

According to the present invention, resin sheets made from acid-modified cyclic polyolefin resins can be cut using a commonly used far-infrared laser, resulting in resin sheets with excellent transparency and circuit board materials made from such sheets.

The present invention will be described in detail below. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to the following description as long as it does not deviate from the gist of the present invention.
In the following, when the expression "~" is used, it is used as an expression including the numerical values or physical property values before and after it.

<<Resin sheet>>
The resin sheet of the present invention comprises a resin composition containing an acid-modified cyclic polyolefin resin (A) and a light absorber (B) having substantially no reactive functional groups in the molecule.

<Acid-modified cyclic polyolefin resin (A)>
The acid-modified cyclic polyolefin resin (A) of the present invention is a polyolefin resin having an alicyclic structure, which is modified with an acid. Suitable examples of the alicyclic structure include cycloalkanes, bicycloalkanes, norbornenes, polycyclic compounds, etc.
Examples of polyolefin resins having an alicyclic structure include resins having an alicyclic structure in the side chain of a polyolefin (hereinafter also referred to as "cyclic polyolefin (α-1)"), and resins having an alicyclic structure in the main chain of a polymer (hereinafter also referred to as "cyclic polyolefin (α-2)").

1. Cyclic polyolefin (α-1)
The cyclic polyolefin (α-1) is a resin having an alicyclic structure in a side chain of a polyolefin, and from the viewpoint of low dielectric tangent, a cyclic polyolefin resin copolymer (a-1) containing at least one type of hydrogenated aromatic vinyl polymer block unit and at least one type of hydrogenated conjugated diene polymer block unit is preferred.

The cyclic polyolefin (α-1) has an alicyclic structure in the side chain of the polyolefin, and therefore tends to have a crystalline melting peak temperature below 100° C. On the other hand, the cyclic polyolefin (α-2) described below does not have a crystalline melting peak temperature below 100° C., or tends to be amorphous.
The crystalline melting peak temperature of the cyclic polyolefin (α-1) is preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 65° C. or higher. The crystalline melting peak temperature is preferably 90° C. or lower, and more preferably 85° C. or lower.
The crystalline melting peak temperature in the present invention is the temperature at which a crystalline melting peak is detected in differential scanning calorimetry (DSC) measured at a heating rate of 10°C/min. The cyclic polyolefin (α-1) of the present invention may have a crystalline melting peak at less than 100°C, and may have a crystalline melting peak at two points, for example, less than 100°C and at 100°C or higher.

As used herein, "block" refers to a polymeric segment of a copolymer that exhibits microphase separation from structurally or compositionally distinct polymeric segments of the copolymer. Microphase separation occurs due to the immiscibility of polymeric segments in the block copolymer.
Microphase separation and block copolymers are extensively discussed in "Block Copolymers - Designer Soft Materials" on pages 32-38 of the February 1999 issue of PHYSICS TODAY.

(1) Cyclic polyolefin resin copolymer (a-1)
Examples of the cyclic polyolefin resin copolymer (a-1) include a diblock copolymer consisting of a hydrogenated aromatic vinyl polymer block unit (hereinafter also referred to as "block A") and a hydrogenated conjugated diene polymer block (hereinafter also referred to as "block B"), a triblock copolymer containing two or more of at least one of block A and block B, a tetrablock copolymer, and a pentablock copolymer.
The cyclic polyolefin resin copolymer (a-1) preferably contains at least two blocks A, and suitable examples thereof include ABA type, ABAB type, and ABABA type.

Furthermore, it is preferable that the cyclic polyolefin resin copolymer (a-1) contains a segment composed of an aromatic vinyl polymer at each end. Therefore, it is preferable that the hydrogenated block copolymer of the present invention has at least two hydrogenated aromatic vinyl polymer block units (block A), and that it has at least one hydrogenated conjugated diene polymer block unit (block B) between these two hydrogenated aromatic vinyl polymer block units (block A). From these viewpoints, the cyclic polyolefin resin copolymer (a-1) is more preferably an A-B-A type or an A-B-A-B-A type.

The content of the hydrogenated aromatic vinyl polymer block unit (block A) in the cyclic polyolefin resin copolymer (a-1) is preferably 30 to 99 mol %, more preferably 40 to 90 mol %, even more preferably 50 mol % or more, and even more preferably 60 mol % or more.
When the ratio of the hydrogenated aromatic vinyl polymer block unit (block A) is equal to or greater than the lower limit, the rigidity is not reduced and the heat resistance and the linear thermal expansion coefficient are also good. On the other hand, when the ratio is equal to or less than the upper limit, the flexibility is good.

The content of the hydrogenated conjugated diene polymer block unit (block B) in the cyclic polyolefin resin copolymer (a-1) is preferably 1 to 70 mol %, more preferably 10 to 60 mol %, even more preferably 50 mol % or less, and even more preferably 40 mol % or less.
When the ratio of the hydrogenated conjugated diene polymer block unit (block B) is equal to or greater than the lower limit, flexibility is improved, whereas when the ratio is equal to or less than the upper limit, rigidity is not reduced and heat resistance and linear thermal expansion coefficient are improved.

The hydrogenated aromatic vinyl polymer block units and hydrogenated conjugated diene polymer block units that make up the cyclic polyolefin resin copolymer (a-1) can be obtained by hydrogenating polymer blocks composed of aromatic vinyl monomers and conjugated diene monomers such as 1,3-butadiene, as described in detail below.

The monomers used to form the aromatic vinyl polymer block units and conjugated diene polymer block units before hydrogenation are described below.

(aromatic vinyl monomer)
The aromatic vinyl monomer serving as a raw material for the aromatic vinyl polymer block unit before hydrogenation is a monomer represented by the general formula (1).

In the above general formula (1), R is hydrogen or an alkyl group, and Ar is a phenyl group, a halophenyl group, an alkylphenyl group, an alkylhalophenyl group, a naphthyl group, a pyridinyl group, or an anthracenyl group.

When R is an alkyl group, the number of carbon atoms is preferably 1 to 6, and the alkyl group may be mono- or polysubstituted with functional groups such as halo groups, nitro groups, amino groups, hydroxy groups, cyano groups, carbonyl groups, and carboxyl groups.
Furthermore, Ar is preferably a phenyl group or an alkylphenyl group, and more preferably a phenyl group.

Examples of aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene (including all isomers, with p-vinyltoluene being particularly preferred), ethylstyrene, propylstyrene, butylstyrene, vinylbiphenyl, vinylnaphthalene, vinylanthracene (including all isomers), and mixtures thereof, with styrene being particularly preferred.

(Conjugated diene monomer)
The conjugated diene monomer that is the raw material for the conjugated diene polymer block unit before hydrogenation is not particularly limited as long as it is a monomer having two conjugated double bonds.
Examples of conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2-methyl-1,3-pentadiene and analogous compounds thereof, and mixtures thereof. Of these, 1,3-butadiene is preferred.

When 1,3-butadiene is used as the conjugated diene monomer, its polymer, polybutadiene, contains 1,4-bond units ([-CH ₂ -CH=CH-CH ₂ -]) and 1,2-bond units ([-CH ₂ -CH(CH=CH ₂ )-]), and upon hydrogenation, the former gives a structure similar to the repeating unit of polyethylene (ethylene structure), and the latter gives a structure similar to the repeating unit obtained when 1-butene is polymerized (1-butene structure). Therefore, the hydrogenated conjugated diene polymer block according to the present invention preferably contains at least either an ethylene structure or a 1-butene structure.
Furthermore, when isoprene is used as the conjugated diene monomer, its polymer, polyisoprene, contains 1,4-bond units ([-CH ₂ -C(CH ₃ )=CH-CH ₂ -]), 3,4-bond units ([-CH ₂ -CH(C(CH ₃ )=CH ₂ )-]), and 1,2-bond units ([-CH ₂ -C(CH ₃ )(CH=CH ₂ )-]), and contains at least one of the three types of repeating units obtained by hydrogenation.

(Block structure)
The cyclic polyolefin resin copolymer (a-1) is preferably produced by hydrogenation of a multiblock copolymer such as a triblock copolymer, tetrablock copolymer, or pentablock copolymer, such as SBS, SBSB, SBSBS, SBSBSB, SIS, SISIS, and SISBS (where S represents polystyrene, B represents polybutadiene, and I represents polyisoprene). The block may be a linear block or may be branched. When branched, the polymerization chain may be bonded at any position along the backbone of the copolymer. In addition to a linear block, the block may be a tapered block or a star block.

The block copolymer constituting the cyclic polyolefin resin copolymer (a-1) before hydrogenation may contain one or more additional block units other than the aromatic vinyl polymer block units and the conjugated diene polymer block units. For example, in the case of a triblock copolymer, these additional block units may be bonded to any position in the triblock polymer backbone.

A preferred example of the hydrogenated aromatic vinyl polymer block unit is hydrogenated polystyrene, and a preferred example of the hydrogenated conjugated diene polymer block unit is hydrogenated polybutadiene or hydrogenated polyisoprene, with hydrogenated polybutadiene being more preferred.
A preferred embodiment of the cyclic polyolefin resin copolymer (a-1) is a hydrogenated triblock or pentablock copolymer of styrene and butadiene, and it is preferable that the copolymer does not contain any other functional group or structural modifier.

(hydrogenation level)
The cyclic polyolefin resin copolymer (a-1) is substantially completely hydrogenated, with the aromatic rings derived from styrene and the like being hydrogenated in addition to the double bonds derived from conjugated dienes such as butadiene. Specifically, this refers to a copolymer that has achieved the following hydrogenation levels:
The hydrogenation level of the hydrogenated aromatic vinyl polymer block unit is preferably 90% or more, more preferably 95% or more, even more preferably 98% or more, and particularly preferably 99.5% or more.
The hydrogenation level of the hydrogenated conjugated diene polymer block unit is preferably 95% or more, more preferably 99% or more, and even more preferably 99.5% or more.
Such a high level of hydrogenation reduces dielectric loss and also improves stiffness and heat resistance.
The hydrogenation level of the hydrogenated aromatic vinyl polymer block unit refers to the proportion of the aromatic vinyl polymer block unit saturated by hydrogenation, and the hydrogenation level of the hydrogenated conjugated diene polymer block unit refers to the proportion of the conjugated diene polymer block unit saturated by hydrogenation.
The hydrogenation level of each block unit is determined using proton NMR.

The cyclic polyolefin resin copolymer (a-1) may be used alone or in combination of two or more kinds.
As the cyclic polyolefin resin copolymer (a-1) of the present invention, commercially available products can be used, and specific examples include TEFABLOC (registered trademark) and ZELAS (registered trademark) manufactured by Mitsubishi Chemical Corporation.

(Modification of cyclic polyolefin resin copolymer (a-1))
The acid-modified cyclic polyolefin resin (a'-1) can be obtained by acid-modifying the above-mentioned cyclic polyolefin resin copolymer (a-1).
When the cyclic polyolefin resin copolymer (a-1) is acid-modified, the polarity of the polymer increases, and therefore, improvement in adhesion to a metal layer such as a copper foil can be expected.
The modification of the cyclic polyolefin resin copolymer (a-1) is described below. This modification is preferably carried out by adding an unsaturated carboxylic acid and/or anhydride thereof as a modifier to the cyclic polyolefin resin copolymer (a-1) and reacting the mixture.

[Modifier]
Examples of the unsaturated carboxylic acid and/or anhydride thereof as the modifying agent include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, α-ethylacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, and nadic acids, and anhydrides thereof.
Specific examples of the acid anhydride include maleic anhydride, citraconic anhydride, and nadic anhydrides.
Examples of nadic acids or anhydrides thereof include endo-cis-bicyclo[2.2.1]hept-2,3-dicarboxylic acid (nadic acid), methyl-endo-cis-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid (methylnadic acid), and the like, and anhydrides thereof.

Among these unsaturated carboxylic acids and/or anhydrides thereof, acrylic acid, maleic acid, nadic acid, maleic anhydride, and nadic anhydride are preferred.
The unsaturated carboxylic acid and/or anhydride thereof may be used alone or in combination of two or more kinds.

[Modification method]
The cyclic polyolefin resin copolymer (a-1) can be modified by solution modification, melt modification, solid phase modification by irradiation with electron beams or ionizing radiation, modification in a supercritical fluid, or the like.
Among these, melt modification is preferred because of its superior equipment and cost competitiveness, and melt kneading modification using an extruder is more preferred because of its superior continuous productivity.
Examples of the apparatus that can be used here include a single-screw extruder, a twin-screw extruder, a Banbury mixer, and a roll mixer. Among these, a single-screw extruder and a twin-screw extruder are preferred because of their excellent continuous productivity.

In general, modification of the cyclic polyolefin resin copolymer (a-1) with an unsaturated carboxylic acid and/or anhydride thereof is carried out by a graft reaction in which a carbon-hydrogen bond of a hydrogenated conjugated diene polymer block unit, which is one of the block units constituting the cyclic polyolefin resin copolymer (a-1), is cleaved to generate a carbon radical, to which an unsaturated functional group is added.
As a source of carbon radicals, in addition to the above-mentioned electron beams and ionizing radiation, a method using high temperatures or radical generators such as organic peroxides, inorganic peroxides, azo compounds, etc. are also usable. As the radical generator, it is preferable to use organic peroxides from the viewpoints of cost and operability.

Examples of the azo compound include azobisisobutyronitrile, azobisdimethylvaleronitrile, azobis(2-methylbutyronitrile), and diazonitrophenol.
Examples of the inorganic peroxides include hydrogen peroxide, potassium peroxide, sodium peroxide, calcium peroxide, magnesium peroxide, and barium peroxide.

The organic peroxides include those belonging to the groups of hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, and ketone peroxides.
Specific examples include hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; dialkyl peroxides such as dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3; diacyl peroxides such as lauryl peroxide and benzoyl peroxide; peroxy esters such as t-butyl peroxyacetate, t-butyl peroxybenzoate and t-butylperoxyisopropyl carbonate; and ketone peroxides such as cyclohexanone peroxide.
These radical generators may be used alone or in combination of two or more.

[Melt-kneading modification]
A commonly used melt-kneading modification procedure involves blending a cyclic polyolefin resin copolymer (a-1), an unsaturated carboxylic acid and/or its anhydride, and an organic peroxide, feeding the mixture into a kneader and extruder, extruding the mixture while heating, melt-kneading, and cooling the molten resin emerging from a die in a water tank or the like to obtain a modified cyclic polyolefin (a'-1).

The blending ratio of the cyclic polyolefin resin copolymer (a-1) and the unsaturated carboxylic acid and/or its anhydride is preferably 0.2 to 5 parts by mass of the unsaturated carboxylic acid and/or its anhydride per 100 parts by mass of the cyclic polyolefin resin copolymer (a-1).
When the blending ratio of the unsaturated carboxylic acid and/or its anhydride to the cyclic polyolefin resin copolymer (a-1) is equal to or greater than the lower limit, a predetermined modification rate necessary for achieving the effects of the present invention can be obtained. On the other hand, when the blending ratio is equal to or less than the upper limit, no unreacted unsaturated carboxylic acid and/or its anhydride remain, which is also preferable in terms of dielectric properties.

The blending ratio of the unsaturated carboxylic acid and/or its anhydride to the organic peroxide is preferably 20 to 100 parts by mass of the organic peroxide per 100 parts by mass of the unsaturated carboxylic acid and/or its anhydride.
When the blending ratio of the organic peroxide to the unsaturated carboxylic acid and/or its anhydride is equal to or greater than the lower limit, a predetermined modification rate necessary for achieving the effects of the present invention can be obtained, and when the blending ratio is equal to or less than the upper limit, the cyclic polyolefin resin copolymer (a-1) does not deteriorate, and the color does not deteriorate.

Furthermore, as for the melt-kneading modification conditions, it is preferable to extrude at a temperature of 150 to 300°C when using a single-screw extruder or twin-screw extruder.

[Modification rate]
The degree of modification of the modified cyclic polyolefin (a'-1) with the unsaturated carboxylic acid and/or anhydride thereof is preferably 0.1 to 2% by mass.
A modification rate of at least the lower limit is preferred because it increases the polarity of the polymer and improves adhesion to a metal layer such as a copper foil. A modification rate of at most the upper limit can prevent deterioration of the dielectric loss of the cyclic polyolefin resin copolymer (a-1). Furthermore, odor generation and color deterioration can be prevented.
The modification rate of the modified cyclic polyolefin (a'-1) can be measured by proton NMR after the modified cyclic polyolefin (a'-1) is subjected to a methyl esterification treatment.

2. Cyclic polyolefin (α-2)
The cyclic polyolefin (α-2) is a resin having an alicyclic structure in the main chain of the polymer, and examples thereof include a hydrogenated product of a ring-opening metathesis polymer of an unsaturated cyclic olefin monomer (hereinafter also referred to as "cyclic polyolefin (a-2)"), and a copolymer of ethylene and a norbornene-based monomer (hereinafter also referred to as "cyclic polyolefin (a-3)"). One type of cyclic polyolefin (α-2) may be used alone, or two or more types may be used in combination.

From the viewpoint of heat resistance, the cyclic polyolefin (α-2) preferably has a high glass transition temperature.
The glass transition temperature of the cyclic polyolefin (α-2) is preferably 100° C. or higher, more preferably 120° C. or higher, and even more preferably 140° C. or higher.
The glass transition temperature can be measured by the method described in the examples.

(1) Cyclic polyolefin (a-2)
The cyclic polyolefin (a-2) is a cyclic polyolefin resin having an alicyclic structure in the main chain of the polyolefin, and examples thereof include monocyclic cycloolefins and their derivatives having a substituent, and substituted and unsubstituted bicyclic, tricyclic or higher polycyclic olefin monomers having a norbornene ring (hereinafter also referred to as "norbornene-based monomers"), etc. Among these, norbornene-based monomers are preferred from the viewpoint of production suitability.

Examples of the monocyclic cycloolefin include cyclobutene, cyclopentene, cyclooctene, and cyclododecene.
Examples of norbornene-based monomers include bicyclic cycloolefins such as norbornene, norbornadiene, methylnorbornene, dimethylnorbornene, ethylnorbornene, chlorinated norbornene, chloromethylnorbornene, trimethylsilylnorbornene, phenylnorbornene, cyanonorbornene, dicyanonorbornene, methoxycarbonylnorbornene, pyridylnorbornene, nadic anhydride, and nadic imide; tricyclic cycloolefins such as dicyclopentadiene, dihydrodicyclopentadiene, and alkyl-, alkenyl-, alkylidene-, and aryl-substituted derivatives thereof; tetracyclic cycloolefins such as dimethanohexahydronaphthalene, dimethanooctahydronaphthalene, and alkyl-, alkenyl-, alkylidene-, and aryl-substituted derivatives thereof; pentacyclic cycloolefins such as tricyclopentadiene; and hexacycloheptadecene. Furthermore, compounds containing norbornene rings such as dinorbornene, compounds in which two norbornene rings are bonded together by a hydrocarbon chain or an ester group, and alkyl- or aryl-substituted products of these compounds can also be used.

The method for producing the cyclic polyolefin (a-2) is not particularly limited, and various known production methods can be employed. The cyclic polyolefin (a-2) can be produced, for example, by ring-opening polymerization of the above-mentioned unsaturated cyclic olefin monomer, followed by hydrogenation of the olefinically unsaturated bond moiety in the resulting polymer. The ring-opening polymerization can be carried out, for example, by subjecting the unsaturated cyclic olefin monomer to a catalyst system containing a transition metal compound or a platinum group metal compound and an organometallic compound such as an organoaluminum compound, in the presence of an additive such as an aliphatic or aromatic tertiary amine, at a temperature within the range of -20°C to 100°C and a pressure within the range of 0.01 to 50 kg/cm ² G. The hydrogenation can also be carried out in the presence of a conventional hydrogenation catalyst.

By acid-modifying the cyclic polyolefin (a-2), an acid-modified cyclic polyolefin resin (a'-2) can be obtained. As with the cyclic polyolefin (α-1) described above, the acid modification can be carried out by adding an unsaturated carboxylic acid and/or its anhydride as a modifier and allowing the reaction to proceed.

The cyclic polyolefin (a-2) of the present invention can be commercially available, and specific examples include Zeonex (registered trademark) and Zeonor (registered trademark) manufactured by Zeon Corporation, and ARTON (registered trademark) manufactured by JSR Corporation. Furthermore, examples of the acid-modified cyclic polyolefin resin (a'-2) include the ARTON (registered trademark) F series manufactured by JSR Corporation.

(2) Cyclic polyolefin (a-3)
As the norbornene-based monomer in the cyclic polyolefin (a-3), the norbornene-based monomers exemplified for the cyclic olefin (a-2) can be used.

By acid-modifying the cyclic polyolefin (a-3), an acid-modified cyclic polyolefin resin (a'-3) can be obtained. As with the cyclic polyolefin (α-1) described above, the acid modification can be carried out by adding an unsaturated carboxylic acid and/or its anhydride as a modifier and allowing the reaction to proceed.

Commercially available cyclic polyolefins (a-3) can be used in the present invention, including APEL (registered trademark) manufactured by Mitsui Chemicals, Inc. and TOPAS (registered trademark) manufactured by TOPAS Advanced Polymers.

[Physical properties]
The dielectric loss tangent of the acid-modified cyclic polyolefin resin (A) is preferably less than 0.05 at 10 GHz, more preferably less than 0.03, and even more preferably less than 0.01. Among these, it is preferably less than 0.005, and more preferably less than 0.001. The smaller the dielectric loss tangent, the smaller the dielectric loss, which is preferable because it can achieve higher transmission efficiency and speed of electrical signals when used as a circuit board material. The lower limit of the dielectric loss tangent is not particularly limited, and it is sufficient if it is 0 or more.

The melt flow rate (MFR) of the acid-modified cyclic polyolefin resin (A) is not particularly limited, but is usually 0.1 g/10 min or more, preferably 0.5 g/10 min or more from the viewpoint of the molding method and the appearance of the molded product, and is usually 50.0 g/10 min or less, preferably 30.0 g/10 min or less from the viewpoint of material strength.
The MFR can be determined in accordance with ISO R1133 by measuring under the conditions described in the examples.

<Light absorber (B)>
The light absorbent (B) of the present invention has a maximum absorbance of 5% or more at a wavelength of 9.4 to 10.6 μm. The resin sheet of the present invention contains such a light absorbent (B), and therefore can be processed with a far-infrared laser.
The maximum absorbance at wavelengths of 9.4 to 10.6 μm is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more, from the viewpoint of processability with a far-infrared laser.

The light absorber (B) preferably does not substantially have a reactive functional group in the molecule, so as not to react with the acid-modified cyclic polyolefin resin (A) and impair the transparency of the sheet.
The reactive functional group is a group that is composed of one or more atoms selected from carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen, and that can undergo a change in its chemical structure upon contact with another functional group or upon heating within the temperature range of normal use or molding in the atmosphere or in a solvent. Specifically, it is, for example, a functional group having an oxygen atom, nitrogen atom, sulfur atom, phosphorus atom, silicon atom, halogen, or a carbon-hydrogen multiple bond (i.e., an unsaturated bond such as a double bond or triple bond).
In the present invention, the phrase "substantially not having a reactive functional group in the molecule" means that the reactive functional group is not present, or the reactive functional group is inactivated by an intramolecular bond or the like, and does not react with the acid-modified cyclic polyolefin resin (A).

Examples of the light absorber (B) include thioxanthone compounds, benzophenone compounds, acetophenone compounds, phosphorus compounds, and benzotriazole compounds.
Among these, phosphorus compounds or benzotriazole compounds are more preferred from the viewpoint of heat resistance.

Examples of the thioxanthone compounds include thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone, 1-chloro-4-propoxythioxanthone, 2,7-dimethoxythioxanthone, and 2,7-diethoxythioxanthone.

Examples of the benzophenone compounds include benzophenone, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2-ethylbenzophenone, 3-ethylbenzophenone, 4-ethylbenzophenone, 2-propylbenzophenone, 3-propylbenzophenone, 4-propylbenzophenone, 2-butylbenzophenone, 3-butylbenzophenone, 4-butylbenzophenone, 2-methoxy-2-phenylacetophenone, 2-ethoxy-2-phenylacetophenone, 2 -propoxy-2-phenylacetophenone, 2-butoxy-2-phenylacetophenone, 2-pentoxy-2-phenylacetophenone, 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, 2,2-dipropoxyacetophenone, 2,2-dibutoxyacetophenone, p-methylbenzophenone, Michler's ketone, methylbenzophenone, dibenzoyl, benzoin, 2-methylbenzophenone, 4-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylbenzophenone 4-benzoylbenzophenone, 3,4-dimethylbenzophenone, 4,4'-dimethoxybenzoin, 4,4'-dimethoxybenzyl, methyl 2-benzoylbenzoate, methyl 4-benzoylbenzoate, ethyl 2-benzoylbenzoate, ethyl 4-benzoylbenzoate, propyl 2-benzoylbenzoate, propyl 4-benzoylbenzoate, butyl 2-benzoylbenzoate, butyl 4-benzoylbenzoate, 4-(p-tolylthio)benzophenone, 2-phenylbenzophenone, 3-phenylbenzophenone, 4-phenylbenzyl Examples include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2-(dimethylamino)benzophenone, 3-(dimethylamino)benzophenone, 4-(dimethylamino)benzophenone, 2-(diethylamino)benzophenone, 3-(diethylamino)benzophenone, 4-(diethylamino)benzophenone, and 4,4'-bis(diethylamino)benzophenone.

Examples of the acetophenone-based compounds include acetophenone, 2-methoxy-2-phenylacetophenone, 2-ethoxy-2-phenylacetophenone, 2-propoxy-2-phenylacetophenone, 2-isopropoxy-2-phenylacetophenone, 2-butoxy-2-phenylacetophenone, 2-isobutoxy-2-phenylacetophenone, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone, methyl benzoylformate, ethyl benzoylformate, 2,2'-dimethoxy-2-phenylacetophenone, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, 2-isonitrosopropiophenone, and 2,4-di-t-butylphenyl 3,5-di-t-butyl-4-hydroxybenzoate.

Examples of the phosphorus-based compounds include 9,10-bis(diethylphosphonomethyl)anthracene and tris(2,4-di-t-butylphenyl)phosphite.

Examples of the benzotriazole compounds include 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol], 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2-hydroxybenzotriazole)-4-(1,1,3,3-tetramethylbutyl)phenol, Examples include 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol, 2,4,6-tris(2-hydroxy-4-hexyloyl-3-methylphenyl)-1,3,5-triazine, and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol.

The light absorbent (B) preferably has heat resistance in order to prevent the light absorption property from being impaired by film formation.
More specifically, the 10% weight loss temperature of the light absorber (B) is preferably 165° C. or higher, more preferably 170° C. or higher, and even more preferably 200° C. or higher. The upper limit of the 10% weight loss temperature is not particularly limited, and may be, for example, 500° C. or lower.
The 10% weight loss temperature in the present invention is a value measured using a high-performance thermal analyzer NEXTA STA200RV (manufactured by Hitachi High-Tech Science Corporation) under the following conditions, but the measurement temperature range may be adjusted as appropriate.
Measurement temperature range: 35 to 300°C
Temperature increase rate: 10°C/min
Atmosphere: N2 flow Measurement sample mass: 2 to 7 mg

The amount of the light absorber (B) added is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.2 parts by mass or more and 25 parts by mass or less, and even more preferably 0.5 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the acid-modified cyclic polyolefin resin (A).
When the amount of the light absorber (B) added is equal to or greater than the lower limit, the far-infrared laser processability is good, whereas when the amount of the light absorber (B) added is equal to or less than the upper limit, the low dielectric properties are good, which is also preferable from the viewpoint of suppressing bleed-out of the light absorber (B).

<Other ingredients>
If necessary, the resin composition of the present invention may contain thermoplastic resins other than the acid-modified cyclic polyolefin resin (A), thermosetting resins, flame retardants, heat stabilizers, weather stabilizers, antistatic agents, fillers, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, organic fillers, flow improvers, plasticizers, dispersants, glass fibers, carbon fibers, and the like, to the extent that the object of the present invention is not impaired, and the blending ratios of these are appropriate amounts.

The thermoplastic resin other than the acid-modified cyclic polyolefin resin (A) is preferably at least one thermoplastic resin selected from the group consisting of a styrene-based thermoplastic elastomer, an olefin-based thermoplastic elastomer, and an ethylene-based polymer. By incorporating such a thermoplastic resin, the toughness of the resin composition is improved.
The content of the thermoplastic resin in 100% by mass of the resin composition is preferably 0% by mass or more and 40% by mass or less, more preferably 1% by mass or more and 30% by mass or less, and even more preferably 5% by mass or more and 20% by mass or less. When the content is within the above range, both toughness and low dielectric properties can be achieved.
As the thermoplastic resin, commercially available products can be used, and specific examples thereof include Tuftec (registered trademark) manufactured by Asahi Kasei Chemicals Corporation, Septon (registered trademark) manufactured by Kuraray Co., Ltd., Kraton (registered trademark) manufactured by Shell Japan, Mirastomer (registered trademark) manufactured by Mitsui Chemicals, Inc., Tafmer (registered trademark) manufactured by Mitsui Chemicals, Inc., and EXCELINK (registered trademark) manufactured by JSR Corporation.

Specific examples of stabilizers that may be added as optional ingredients other than those mentioned above include phenolic antioxidants such as tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, β-(3,5-di-t-butyl-4-hydroxyphenyl)propionic acid alkyl ester, and 2,2'-oxamidobis[ethyl-3(3,5-di-t-butyl-4-hydroxyphenyl)]propionate; fatty acid metal salts such as zinc stearate, calcium stearate, and calcium 12-hydroxystearate; and polyhydric alcohol fatty acid esters such as glycerin monostearate, glycerin monolaurate, glycerin distearate, and pentaerythritol tristearate. These may be blended alone or in combination; for example, a combination of tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane with zinc stearate and glycerin monostearate is an example.

<<Resin sheet>>
The resin sheet of the present invention can be obtained by forming the above-mentioned resin composition into a sheet.
The method for producing the resin sheet is not particularly limited, but known methods such as extrusion molding, injection molding, blow molding, vacuum molding, pressure molding, and press molding can be used.

The resin sheet of the present invention may be a uniaxially or biaxially stretched sheet that has been stretched in one or two directions. Stretched sheets can be produced by producing an unstretched precursor sheet by a T-die casting method, a press method, a calendar method, or the like, followed by stretch molding by a roll stretching method, a tenter stretching method, or the like, or by performing melt extrusion and stretch molding in one step by an inflation method, a tubular method, or the like.

The molding temperature in the press method or extrusion casting method using a T-die is adjusted appropriately depending on the flow characteristics and film-forming properties of the resin composition used, but is generally between 200°C and 260°C. For melt kneading, commonly used single-screw extruders, twin-screw extruders, kneaders, mixers, etc. can be used, and there are no particular limitations.

The thickness of the resin sheet is preferably 10 μm or more and 500 μm or less, more preferably 30 μm or more and 400 μm or less, and even more preferably 50 μm or more and 300 μm or less. By keeping the thickness within the above range, it is possible to obtain a circuit board material that can accommodate the miniaturization of electrical and electronic devices while maintaining appropriate strength.

The relative dielectric constant of the resin sheet at 10 GHz is preferably less than 3, more preferably less than 2.5, and even more preferably less than 2.3. The smaller the relative dielectric constant, the smaller the dielectric loss, and therefore the higher the transmission efficiency and speed of electrical signals when used as a circuit board material. There is no particular lower limit for the relative dielectric constant, and it is sufficient as long as it is 1 or greater.

The dielectric dissipation factor of the resin sheet at 10 GHz is preferably less than 0.03, more preferably less than 0.02, even more preferably less than 0.01, even more preferably less than 0.005, even more preferably less than 0.003, and even more preferably less than 0.001. The smaller the dielectric dissipation factor, the smaller the dielectric loss, and therefore the higher the electrical signal transmission efficiency and speed when used as a circuit board material. There is no particular lower limit for the dielectric dissipation factor, as long as it is equal to or greater than 0.

The relative permittivity and dielectric loss tangent of the present invention were measured in TE mode at 23°C and 10 GHz using a cavity resonator (manufactured by AET) and a network analyzer MS46 122B (manufactured by Anritsu Corporation).

<<Applications of resin sheets>>
Examples of applications of the resin sheet of the present invention include, but are not limited to, circuit board materials including circuit board materials for electric and electronic devices such as copper foil laminates, flexible printed circuit boards, multilayer printed wiring boards, and capacitors, underfill materials, interchip fills for 3D-LSIs, insulating sheets, and heat dissipation substrates.

<Circuit board materials>
The resin sheet of the present invention can be used as an insulating layer to form a circuit board material by laminating it with a conductor.

The conductor can be a metal foil made of a conductive metal such as copper or aluminum, or an alloy containing these metals, or a metal layer formed by plating or sputtering.

When used as a circuit board material for electrical and electronic devices, the thickness of the insulating layer made of the resin composition is preferably 10 μm or more and 500 μm or less, more preferably 50 μm or more and 400 μm or less, and even more preferably 100 μm or more and 300 μm or less. Furthermore, the thickness of the conductor is preferably 0.2 μm or more and 70 μm or less.

The circuit board material of the present invention is characterized by a sufficiently low dielectric loss tangent.
The dielectric loss tangent of the circuit board material at 10 GHz is preferably less than 0.03, more preferably less than 0.02, even more preferably less than 0.01, even more preferably less than 0.005, even more preferably less than 0.003, and even more preferably less than 0.001. The smaller the dielectric loss tangent, the smaller the dielectric loss, which is preferable because it can achieve higher transmission efficiency and speed of electrical signals in the circuit board. There is no particular limitation on the lower limit of the dielectric loss tangent, and it is sufficient as long as it is 0 or more.

<Method of manufacturing circuit board materials>
The circuit board material of the present invention can be produced, for example, by the following method.
After preparing an insulating layer made of the resin sheet of the present invention, a conductor is laminated on the insulating layer, and a circuit is formed using a photoresist or the like, and the required number of such layers are laminated.
The lamination of the insulating layer and the conductor may be performed by directly laminating a conductive metal foil on the insulating layer, by bonding the insulating layer and the conductive metal foil with an adhesive, by forming a conductive metal layer by plating or sputtering, or by combining these methods.

<Method of cutting resin sheet>
As described above, the resin sheet of the present invention can be cut using a general-purpose far-infrared laser.
That is, the present invention also provides a method for cutting a resin sheet, which comprises irradiating, with far-infrared laser light, a resin sheet made of a resin composition containing an acid-modified cyclic polyolefin resin (A) and a light absorber (B) having a maximum absorbance of 5% or more at a wavelength of 9.4 to 10.6 μm and having substantially no reactive functional groups in the molecule.

The acid-modified cyclic polyolefin resin (A) alone does not have absorption in the oscillation wavelength range of the far-infrared laser, but by adding a light absorber (B) having a maximum absorbance of 5% or more in the wavelength range of 9.4 to 10.6 μm, cutting processing becomes possible.
When the resin sheet of the present invention is irradiated with laser light, the irradiated area is heated by the energy of the laser light, causing thermal melting or abrasion, and therefore the resin sheet is cut in the irradiated area.
In the present invention, "cutting" refers to cutting a resin sheet into a desired shape, and includes punching and the like.

The cutting process is performed by irradiating the surface of the resin sheet with a laser and sequentially moving the irradiation position. The movement of the irradiation position is relative; for example, the position of the resin sheet may be fixed and the laser emitted from the laser oscillator may be moved, or the position of the laser emitted from the laser oscillator may be fixed and the resin sheet may be moved. Alternatively, both the resin sheet and the laser emitted from the laser oscillator may be moved in opposite directions.
When performing drilling, a laser is irradiated onto the surface of the resin sheet, and the irradiation position is moved sequentially to form through-holes. For example, in a multilayer substrate, vias or through-holes are formed as through-holes. The diameter of the via is not particularly limited, but is preferably about 10 μm to 1 mm.

The wavelength of the far-infrared laser is generally 9.4 to 10.6 μm, which is the oscillation wavelength of a _CO2 laser, but is not limited to this as long as it is in the far-infrared region. For example, it may be 5.3 to 5.9 μm, which is the oscillation wavelength of a CO2 laser, or 1.15 to 5.4 μm, which is the oscillation wavelength of an infrared HeNe laser.
The output of the laser light is preferably 1 W or more but less than 50 W, more preferably 10 W or more but 40 W or less. When the output is equal to or greater than the lower limit, the cutting speed can be increased, resulting in good productivity. When the output is equal to or less than the upper limit, the amount of melted resin is large, preventing the cut surface from becoming too wide, or preventing the edges from swelling due to the accumulation of heat-molten resin on the cut surface. In addition, thermal damage to areas other than the cut surface and the generation of decomposition products are also suppressed. When it is desired to suppress thermal damage and increase the cutting speed at the same time, it is advisable to repeatedly irradiate the laser with the laser output reduced.
The cutting speed, i.e., the moving speed of the laser irradiation position, depends on the thickness of the resin sheet to be cut, but if the thickness of the resin sheet is in the range of 0.1 to 500 μm, it is 1 m/min or more, preferably 5 to 60 m/min.

The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention. The values of various production conditions and evaluation results in the following examples represent preferred upper or lower limit values in the embodiments of the present invention, and preferred ranges may be defined by combining the above-mentioned upper or lower limit values with the values in the following examples or values between the examples.
In the following examples and comparative examples, various physical properties were measured by the following methods.

<Measurement method>
(1) Maximum Absorbance The maximum absorbance of the light absorber (B) at wavelengths of 9.4 to 10.6 μm was measured by preparing a 0.02 mg/mL DMSO solution and using a Fourier transform infrared spectrometer Nicolet iS5 (manufactured by Thermo Fisher Scientific) by reflection ATR.

(2) Far-infrared laser ( _CO2 laser) processability For the resin sheets of the examples and comparative examples, a _CO2 laser processing machine Etcher Laser Pro (manufactured by smartDIYs) was used to trace the outer diameter of a 12 mm diameter at a speed of 6000 mm/min to evaluate laser processability. The wavelength was 9.4 to 10.6 μm, the laser output was 27 W, and the evaluation criteria were as follows.
A (good): A circle with a diameter of 12 mm was cut completely.
B (poor): Some parts are not cut (some parts cannot be cut).
C (very poor): Almost no penetration and cannot be cut.

(3) Dielectric Properties Using a cavity resonator method, the relative permittivity and dielectric loss tangent at 23°C and 10 GHz in the in-plane direction of the resin sheet were measured in TE mode using a cavity resonator (manufactured by AET Co., Ltd.) and a network analyzer MS46 122B (manufactured by Anritsu Co., Ltd.).

(4) Transparency The appearance (transparency) of the resin sheet was evaluated according to the following criteria.
A (good): The sheet is transparent and not discolored or whitened.
B (poor): Coloring or whitening is observed on the sheet.

(5) Crystalline Melting Peak Temperature and Glass Transition Temperature For the acid-modified cyclic polyolefin resin (A), in accordance with JIS K7121:2012, a differential scanning calorimeter Pyris1 DSC (manufactured by PerkinElmer) was used in a temperature range of 25 to 300°C and a heating rate of 10°C/min. The crystal melting peak temperature was determined from the endothermic peak of the DSC curve detected during the reheating process, and the glass transition temperature was determined from the inflection point.

(6) 10% Weight Loss Temperature The 10% weight loss temperature of the light absorber (B) was measured under the following conditions using a high-performance thermal analyzer NEXTA STA200RV (manufactured by Hitachi High-Tech Science Corporation).
Measurement temperature range: 35 to 300°C
Temperature increase rate: 10°C/min
Atmosphere: N2 flow Measurement sample mass: 2 to 7 mg

<Raw materials>
[Acid-modified cyclic polyolefin resin (A)]
A-1: "TEFABLOCK (registered trademark) CP MC940AP" manufactured by Mitsubishi Chemical Corporation was used as an acid-modified cyclic polyolefin resin (a'-1).
Crystal melting peak temperature: 75°C
Density (ASTM D792): 0.94g/ ^cm3
MFR (230°C, 2.16 kg): 3 g/10 min Hydrogenated aromatic vinyl polymer block unit: hydrogenated polystyrene with a content of 67 mol% and a hydrogenation level of 99.5% or more Hydrogenated conjugated diene polymer block unit: hydrogenated polybutadiene with a content of 33 mol% and a hydrogenation level of 99.5% or more Block structure: pentablock structure, total hydrogenation level: 99.5% or more Maleic acid modification rate: 1.2 mass%
Mw: 68,000

[Light absorber (B)]
B-1: Thioxanthone (manufactured by Tokyo Chemical Industry Co., Ltd., maximum absorbance at wavelengths of 9.4 to 10.6 μm: 26%, 10% weight loss temperature: 216° C.)
B-2: 2-isopropylthioxanthone (manufactured by Tokyo Chemical Industry Co., Ltd., maximum absorbance at wavelengths of 9.4 to 10.6 μm: 28%, 10% weight loss temperature: 236° C.)
B-3: 2,2-dimethoxy-2-phenylacetophenone (IGM Resins "Omnirad 651", maximum absorbance at wavelengths of 9.4 to 10.6 μm: 79%, 10% weight loss temperature: 172° C.)
B-4: Tris(2,4-di-t-butylphenyl)phosphite (BASF "Irgafos 168", maximum absorbance at wavelengths of 9.4 to 10.6 μm: 92%, 10% weight loss temperature: 265° C.)
B-5: 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol] (ADEKA Corporation "ADEKA STAB LA-31RG", maximum absorbance at wavelengths of 9.4 to 10.6 μm: 29%, 10% weight loss temperature: 300°C or higher)
B-101: 2-hydroxythioxanthone (Seiko Chemical Co., Ltd., maximum absorbance at wavelengths of 9.4 to 10.6 μm: 7%, 10% weight loss temperature: 267° C.)
B-102: 4-hydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd., maximum absorbance at wavelengths of 9.4 to 10.6 μm: 16%, 10% weight loss temperature: 224° C.)
Note that B-1 to B-4 are compounds that do not have a reactive functional group. B-5 has a hydroxyl group, but it is thought to be inactivated by forming an intramolecular bond with the nitrogen atom of the triazole, so it is a compound that does not substantially have a reactive functional group. B-101 and B-102 are compounds that have a hydroxyl group.

<Examples 1 to 10 and Comparative Examples 1 to 3>
The raw materials were blended in the proportions shown in Table 1 and melt-kneaded for 10 minutes at 230°C and 60 rpm using a Laboplastograph (manufactured by Toyo Seiki Seisakusho, Ltd.) to produce a resin composition. The prepared resin composition was spread on a polyimide film (manufactured by Ube Industries, product name: Upilex), held for 3 minutes at 230°C under a pressure of 0.2 MPa using a heat press, and then slowly cooled to obtain a 300 μm thick resin sheet. The dielectric properties and transparency of the 300 μm thick resin sheet were evaluated. The obtained resin sheet was subjected to the above evaluations.

As shown in Examples 1 to 10, since the light absorber (B) does not substantially have a reactive functional group in the molecule, it does not react with the acid-modified cyclic polyolefin resin (A) during film formation, and highly transparent films were obtained. These resin sheets also had excellent low dielectric properties.
Furthermore, the light absorbents (B) of Examples 1 to 10 had a maximum absorbance of 5% or more at wavelengths of 9.4 to 10.6 μm, and therefore had good far-infrared laser processability.
In addition, the light absorber (B) used in Examples 1 to 10 had a 10% weight loss temperature of 165°C or higher, so it did not decompose during film formation and was able to impart far-infrared laser processability to the film.
Such a resin composition can provide a film that exhibits excellent dielectric properties when used as a circuit board material and can be cut or drilled with a general-purpose far-infrared laser or the like.

On the other hand, in Comparative Example 1, the resin itself cannot absorb far-infrared laser light, so although the dielectric properties and transparency are excellent, processing with a far-infrared laser is not possible. Furthermore, in Comparative Examples 2 and 3, when the light absorber has a hydroxyl group as a reactive functional group, a reaction with the acid-modified cyclic polyolefin resin (A) occurs during film formation, presumably resulting in coloration and whitening of the film.

Claims (8)

A resin sheet made of a resin composition containing an acid-modified cyclic polyolefin resin (A) and a light absorber (B) ,
the acid-modified cyclic polyolefin resin (A) is a crystalline resin having an alicyclic structure in a polyolefin side chain and having a crystalline melting peak temperature of less than 100°C;
The resin sheet, wherein the light absorber (B) has substantially no reactive functional groups in the molecule and has a maximum absorbance of 5% or more at a wavelength of 9.4 to 10.6 μm . 2. The resin sheet according to claim 1, wherein the acid-modified cyclic polyolefin resin (A) is a cyclic polyolefin containing at least one hydrogenated aromatic vinyl polymer block unit and at least one hydrogenated conjugated diene polymer block unit modified with an unsaturated carboxylic acid and/or an anhydride thereof. 3. The resin sheet according to claim 1, wherein the light absorber (B) is at least one selected from the group consisting of a thioxanthone-based compound, a benzophenone-based compound, an acetophenone-based compound, a phosphorus-based compound, and a benzotriazole-based compound. The resin sheet according to any one of claims 1 to 3 , wherein the light absorber (B) has a 10% weight loss temperature of 165°C or higher. The resin sheet according to any one of claims 1 to 4, having a relative dielectric constant of less than 2.5 and a dielectric loss tangent of less than 0.003 at 10 GHz. The resin sheet according to any one of claims 1 to 5, wherein the resin composition further contains at least one thermoplastic resin selected from the group consisting of a styrene-based thermoplastic elastomer, an olefin-based thermoplastic elastomer, and an ethylene-based polymer. A circuit board material comprising an insulating layer made of the resin sheet according to any one of claims 1 to 6 and a conductor laminated together. A method for cutting a resin sheet, comprising irradiating a resin sheet made of a resin composition containing an acid-modified cyclic polyolefin resin (A) and a light absorber (B) with far-infrared laser light ,
the acid-modified cyclic polyolefin resin (A) is a crystalline resin having an alicyclic structure in a polyolefin side chain and having a crystalline melting peak temperature of less than 100°C;
The method for cutting a resin sheet, wherein the light absorber (B) has substantially no reactive functional groups in the molecule and has a maximum absorbance of 5% or more at a wavelength of 9.4 to 10.6 μm.