JP7533102B2 - Electronic Materials - Google Patents

Description

The present invention relates to an electronic material and a laminate using the same.

In recent years, the electronics field has seen remarkable development, particularly in the miniaturization, weight reduction, and high density of electronic devices, which has led to an increasing demand for electronic materials, including printed wiring boards, to be thinner, multi-layered, and highly precise. Specific examples of adhesives and coating agents used around such electronic materials include the following (1) to (6):

(1) Interlayer adhesive: Used to bond circuit boards together, it comes into direct contact with the copper or silver circuit. It is used between the layers of multilayer boards and is available in liquid and sheet form.

(2) Adhesives for coverlay films: These are used to bond a coverlay film (such as a polyimide film used to protect the top surface of a circuit) to the underlying circuit board, and many of them have the polyimide film and adhesive layer already integrated.

(3) Copper-clad film (CCL) adhesive: Used to bond polyimide film and copper foil. Etching and other processes are performed when forming the copper circuit.

(4) Coverlay: Used to protect the top surface of a circuit, it is formed by printing ink on the circuit or by attaching an adhesive sheet to it and then curing it. There are photosensitive and thermosetting types.

(5) Reinforcing plate adhesive: Used to attach part of a wiring board to a reinforcing plate made of metal, glass epoxy, polyimide, etc., in order to supplement the mechanical strength of the wiring board.

(6) Electromagnetic wave shielding adhesive: Attached to flexible printed wiring boards to block electromagnetic noise generated by electronic circuits.

These come in various forms, such as liquid (made into ink for printing) or sheet (made into a film in advance), with the appropriate form being selected depending on the application.

In order to meet these high demands for peripheral electronic materials, various polyimide resins are being investigated.

On the other hand, polyimide resins have low solvent solubility, making them difficult to handle, and in recent years, efforts have been made to develop polyimide resins that have good solvent solubility and dielectric properties.

For example, Patent Document 1 discloses that by incorporating dimer diamine into polyimide, a polyimide having good solvent solubility and good dielectric properties can be synthesized.
However, although the polyimide described in Patent Document 1 has a high thermal decomposition temperature, the Tg of the resin is low, so that the resin is prone to deformation when used at high temperatures, and the performance is not sufficient for electronic substrates.

Furthermore, Patent Document 2 discloses that the softening point can be improved by using a dimer diamine skeleton in combination with a phenylenediamine skeleton.
However, even in the invention described in Patent Document 2, the improvement in Tg is insufficient, and in addition, the phenylenediamine skeleton strengthens the interaction between polyimides, resulting in insufficient compatibility. As a result, when applied to a substrate such as an insulating sheet or Teflon (registered trademark) that does not have high wettability, the resin varnish does not wet and spread sufficiently, resulting in problems such as a decrease in specific properties such as dielectric properties and heat resistance.

JP 2018-168369 A JP 2020-117631 A

The object of the present invention is to provide an electronic material using polyimide that has good wettability to a substrate when applied, good dielectric properties, and a high Tg.

The present invention relates to the following inventions [1] to [9].

[1] An electronic material comprising a reaction product of an aromatic diamine (A-1) represented by the following general formula and a polycarboxylic acid.

(In the formula, X represents a single bond, —CH ₂ —, —SO ₂ —, —C(═O)—, —O—, —O—C ₆ H ₄ —C(CH ₃ ) ₂ —C ₆ H ₄ —O—, —COO—(CH ₂ )l-OCO—, or —COO—CH ₂ —CH(—O—C(═O)—CH ₃ )—CH ₂ —OCO—, and l represents 1 to 20.)

[2] The diamine further includes a dimer diamine,
The electronic material according to [1], wherein the amount of the dimer diamine is 10 to 200 parts by mass per 100 parts by mass of the aromatic diamine (A-1).

[3] The electronic material according to [1] or [2] further contains a crosslinking agent and/or an organic solvent.

[4] The electronic material according to any one of [1] to [3], which is an adhesive.

[5] An adhesive layer formed by heating the electronic material described in [4].

[6] An adhesive sheet comprising the adhesive layer and support film described in [5].

[7] A laminate comprising the adhesive layer described in [6] and a substrate.

[8] The laminate according to [7], in which the substrate is copper foil and/or an insulating sheet.

[9] A printed wiring board laminate comprising the laminate described in [7] or [8], which contains copper foil and further comprises a circuit pattern disposed on the copper foil.

The present invention makes it possible to provide electronic materials that have good wettability to substrates and combine high Tg and dielectric properties.

<Aromatic diamine (A-1)>
The present invention relates to an electronic material comprising a reaction product of a diamine and a polycarboxylic acid. The diamine comprises an aromatic diamine (A-1).
The aromatic diamine (A-1) includes those represented by the following structure:

(In the formula, X represents a single bond, —CH ₂ —, —SO ₂ —, —C(═O)—, —O—, —O—C ₆ H ₄ —C(CH ₃ ) ₂ —C ₆ H ₄ —O—, —COO—(CH ₂ )l-OCO—, or —COO—CH ₂ —CH(—O—C(═O)—CH ₃ )—CH ₂ —OCO—, and l represents 1 to 20.)

Specifically, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane,
Examples of the compound include 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenyl ether, 4,4'-3,3-diamino-3,3'-diethyl-5,5'-dimethyldiphenyl sulfone, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenyl ketone, and 2,2-bis(4-amino-3-ethyl-5-dimethylphenoxyphenyl)propane. Among these, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane is particularly preferred because it is excellent in improving wettability to the substrate and Tg.

The aromatic diamine (A-1) can be used alone or in combination of two or more types.

<Dimer diamine>
The amines reacted with the polycarboxylic acid may further include dimer diamines.
In the present invention, the dimer diamine is a cyclic or acyclic dimer acid obtained as a dimer of an unsaturated fatty acid, in which all the carboxyl groups have been substituted with primary amino groups.
Commercially available dimer diamine products include, for example, "Priamine 1071", "Priamine 1073", "Priamine 1074", and "Priamine 1075" manufactured by Croda Japan, and "Versamine 551" manufactured by BASF Japan.
The dimer diamines can be used alone or in combination of two or more kinds.

The content of dimer diamine is preferably 10 to 200 parts by mass, and more preferably 40% to 100% by mass, based on 100 parts by mass of the aromatic diamine (A-1), because it has excellent flexibility, adhesion, and compatibility.

The diamine used in the present invention may be a diamine other than the aromatic diamine (A-1) and dimer diamine. Diamines other than the aromatic diamine (A-1) and dimer diamine can be broadly classified into aromatic diamines, aliphatic diamines, alicyclic diamines, etc. Preferred examples include, but are not limited to, the following structures.

(l is an integer from 1 to 3)

<Polycarboxylic acid>
The present invention relates to an electronic material comprising a reaction product of a specific diamine and a polycarboxylic acid. The polycarboxylic acid may be in the form of an acid anhydride.
The polycarboxylic acids used in the present invention include 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylethertetracarboxylic dianhydride, 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride, 2,2-bis(3,3',4,4'-tetracarboxyphenyl)tetrafluoropropane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2' ... 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 9,9'-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 9,9'-bis(3,4-dicarboxyphenoxy)fluorene dianhydride, 1',2'-dianhydride;4,4'-[4,4'-(propane-2,2-diyl)diphenoxy]diphthalic dianhydride, and the like are exemplified.
The polycarboxylic acids may be used alone or in combination of two or more kinds.

The polycarboxylic acid component is preferably at least one selected from the group consisting of 2,2-bis(3,3',4,4'-tetracarboxyphenyl)tetrafluoropropane dianhydride, 9,9'-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 1',2'-dianhydride; 4,4'-[4,4'-(propane-2,2-diyl)diphenoxy]diphthalic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 2,3,3',4'-biphenyltetracarboxylic dianhydride, because of its excellent compatibility with the aromatic diamine (A-1), adhesion, and heat resistance.

The reaction between the polycarboxylic acid and the diamine can be carried out in an aprotic polar solvent by a known method. Examples of aprotic polar solvents include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), methyldiglyme, cyclohexanone, and 1,4-dioxane. Only one type of aprotic polar solvent may be used, or two or more types may be mixed together. In this case, there is no problem in mixing the above aprotic polar solvent with a nonpolar solvent that is compatible with it, and aromatic hydrocarbons such as toluene, xylene, mesitylene, and solvent naphtha are often used. The proportion of the nonpolar solvent in the mixed solvent is preferably 30% by mass or less. This is because if the nonpolar solvent is 30% by mass or more, the dissolving power of the solvent is improved and the polyamic acid is less likely to precipitate. The reaction between the tetracarboxylic dianhydride and the diamine component is preferably carried out by dissolving the well-dried diamine component in the aforementioned reaction solvent that has been dehydrated and purified, and then adding the well-dried polycarboxylic dianhydride to the solution.

The reaction between the polycarboxylic acid and the diamine may be either a random reaction or a block reaction. The reactants may be, for example, homogeneous reactants in which the diamine components are reacted separately, mixed together, or the reactants may be further reacted by recombination. For example, an acid-terminated oligomer prepared in advance with an excess of polycarboxylic dianhydride and an amine-terminated oligomer prepared with an excess of diamine may be mixed and further reacted.

The reaction can be carried out at a relatively low temperature, for example, about 10 to 80°C, to produce a polyamic acid, which can then be thermally or chemically imidized to produce the polyamic acid. Alternatively, the step of producing the polyamic acid can be omitted, and the polyamic acid can be produced by a one-step reaction in which polymerization and imidization are carried out in an organic solvent at a relatively high temperature, for example, about 130 to 250°C.

Thermal imidization can be carried out at temperatures of, for example, about 200°C to 400°C, while chemical imidization can be carried out in the presence of, for example, an organic base such as pyridine or triethylamine, and acetic anhydride. The temperature at this time can be selected from any temperature between -20°C and 200°C.

The electronic material of the present invention can be used as a polymerization solution of the polyimide polymer (A) obtained by thermally imidizing or chemically imidizing the polyamic acid. In addition, a poor solvent such as methanol or ethanol can be added to precipitate the resin, which can then be isolated, recovered, and used as a powder.

<Crosslinking Agent>
The electronic material of the present invention may further contain a crosslinking agent to improve heat resistance and adhesiveness. Examples of the crosslinking agent include epoxy-containing compounds and isocyanate-containing compounds.

<Epoxy group-containing compounds>
The epoxy group-containing compound contained in the present invention is not particularly limited as long as it has an epoxy group in the molecule, but it is preferable to use one having an average of two or more epoxy groups in one molecule. As the epoxy group-containing compound, for example, an epoxy resin such as a glycidyl ether type epoxy resin, a glycidyl amine type epoxy resin, a glycidyl ester type epoxy resin, or a cyclic aliphatic (alicyclic) epoxy resin can be used.

Examples of glycidyl ether type epoxy resins include cresol novolac type epoxy resins, phenol novolac type epoxy resins, and tetrakis(glycidyloxyphenyl)ethane. Examples of glycidyl ether type epoxy resins include tetraglycidyl diaminodiphenylmethane, tetraglycidyl metaxylylenediamine, 1,2,4-benzenetricarboxylic acid triglycidyl ester, 1,3,5-benzenetricarboxylic acid triglycidyl ester, 1,1,2,4,5-benzenetetracarboxylic acid tetraglycidyl ester, tri(carboxyethyl)isocyanurate triglycidyl ester, polyglycidyl esters derived from polycarboxylic acids such as polymerized fatty acids, cyclohexane-1,2,4-tricarboxylic acid triglycidyl ester, 1,2,4-cyclohexanetricarboxylic acid triglycidyl ester, 1,3,5-cyclohexanetricarboxylic acid triglycidyl ester, 2,4,5-cyclohexanetetracarboxylic acid tetraglycidyl ester, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and dicyclopentadiene type epoxy resins. Other examples include diglycidyl phthalate, diglycidyl hexahydrophthalate, diglycidyl tetrahydrophthalate, and 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate.

<Isocyanate group-containing compounds>
The isocyanate group-containing compound is not particularly limited as long as it has an isocyanate group in the molecule.
Specific examples of the isocyanate group-containing compound having one isocyanate group in one molecule include n-butyl isocyanate, isopropyl isocyanate, phenyl isocyanate, benzyl isocyanate, (meth)acryloyloxyethyl isocyanate, 1,1-bis[(meth)acryloyloxymethyl]ethyl isocyanate, vinyl isocyanate, allyl isocyanate, (meth)acryloyl isocyanate, and isopropenyl-α,α-dimethylbenzyl isocyanate.
Also, 1,6-diisocyanatohexane, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, xylylene diisocyanate, 2,4-tolylene diisocyanate, toluene diisocyanate, 2,4-toluene diisocyanate, hexamethylene diisocyanate, 4-methyl-m-phenylene diisocyanate, naphthylene diisocyanate, paraphenylene diisocyanate, tetramethylxylylene diisocyanate, cyclohexylmethane diisocyanate, water Compounds obtained by reacting a diisocyanate compound such as doped xylylene diisocyanate, cyclohexyl diisocyanate, tolidine diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylene diisocyanate, or dimer acid diisocyanate with a vinyl monomer containing a hydroxyl group, a carboxyl group, or an amide group in equimolar amounts can also be used as the isocyanate compound.

Specific examples of the isocyanate group-containing compound having two isocyanate groups in one molecule include aromatic diisocyanates such as 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4',4"-triphenylmethane triisocyanate;
Aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate;
Aromatic aliphatic diisocyanates such as ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate;
Alicyclic diisocyanates such as 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate [also known as isophorone diisocyanate], 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,3-bis(isocyanatemethyl)cyclohexane, and 1,4-bis(isocyanatemethyl)cyclohexane are included.

Specific examples of isocyanate group-containing compounds having three isocyanate groups per molecule include aromatic polyisocyanates, aliphatic polyisocyanates such as lysine triisocyanate, aromatic aliphatic polyisocyanates, and alicyclic polyisocyanates, as well as the trimethylolpropane adducts of diisocyanates described above, biuret products reacted with water, and trimers having an isocyanurate ring.

As the isocyanate group-containing compound, there can also be used a blocked isocyanate group-containing compound in which the isocyanate group in the various isocyanate group-containing compounds exemplified above is protected with ε-caprolactam, MEK oxime or the like.
Specific examples include compounds in which the isocyanate group of the isocyanate group-containing compound is blocked with ε-caprolactam, methyl ethyl ketone (hereinafter referred to as MEK) oxime, cyclohexanone oxime, pyrazole, phenol, etc. In particular, hexamethylene diisocyanate trimer having an isocyanurate ring and blocked with MEK oxime or pyrazole is highly preferred because it has excellent adhesive strength and heat resistance to polyimide and copper when used in the present invention.

From the viewpoint of durability and adhesion, the content of the epoxy resin and isocyanate compound is preferably 1 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of polyimide.

<Other additives>
The electronic material of the present invention may further contain additives such as antioxidants, ultraviolet absorbers, hydrolysis inhibitors, antifungal agents, thickeners, plasticizers, pigments, and fillers as necessary, and may also contain known catalysts, additives, etc. for adjusting the curing reaction.

<Adhesive>
The electronic material of the present invention can be in the form of an adhesive. The adhesive is obtained by applying an adhesive obtained by mixing the above-mentioned polyimide resin as a single resin, a curing agent, a filler, an additive, etc. in an arbitrary ratio to a suitable support film, heating to volatilize the organic solvent to cure the adhesive, and peeling it off from the support film. The thickness of the adhesive layer is preferably about 3 μm or more and 40 μm or less.

<Adhesive Layer>
When producing the adhesive layer, the above adhesive may be used in combination with various known adhesives other than the above adhesive.Similarly, the above adhesive may be used in combination with various known adhesives other than the above adhesive.

<Adhesive sheet>
The adhesive sheet of the present invention can be obtained, for example, as follows.
A thermosetting adhesive in a solution or dispersion state can be applied to at least one side of a support film and then dried, typically at 40 to 150° C., to obtain a thermosetting adhesive sheet in an uncured state (so-called B-stage state) with a sheet-like substrate attached. The other side of the thermosetting adhesive sheet can then be covered with another sheet-like substrate to obtain the thermosetting adhesive sheet with a support film of the present invention.
At least one of the support films used is preferably a peelable support film. That is, a thermosetting adhesive in a solution or dispersion state is applied to a peelable support film and dried to form a thermosetting adhesive sheet, and then the other side of the thermosetting adhesive sheet can be covered with another peelable support film, or can be covered with a non-peeling support film that serves as an adherend. Alternatively, a thermosetting adhesive in a solution or dispersion state can be applied to a non-peeling support film that serves as an adherend and dried to form a thermosetting adhesive sheet, and then the other side of the thermosetting adhesive sheet can be covered with another peelable sheet-like substrate.

The dry film thickness of the thermosetting adhesive sheet is preferably 5 to 500 μm, more preferably 10 to 100 μm, in order to ensure sufficient adhesiveness and solder heat resistance, and from the standpoint of ease of handling.
Examples of the coating method include comma coating, knife coating, die coating, lip coating, roll coating, curtain coating, bar coating, gravure printing, flexographic printing, dip coating, spray coating, and spin coating.

<Support film>
Among the support films that can be used, those having no peelability include various plastic films, such as polyimide films, polyester films, polyphenylene ether films, polyphenylene sulfide films, polystyrene films, polycarbonate films, and polyether ether ketone films.
Among the support films used, those having releasability include various plastic films that have been subjected to a release treatment, paper that has been subjected to a release treatment, etc. Examples of various plastic films that can be subjected to the release treatment include polyester films and polyolefin films.

<Sheet-shaped cured product>, <Printed wiring board with protective sheet>
The sheet-like cured product of the present invention is defined as a product obtained by thermally curing the thermosetting adhesive sheet of the present invention, for example, at a temperature of about 40 to 200°C.

<Laminate>
The laminate of the present invention is a laminate in which a polyimide resin adhesive, a film-like adhesive, or an adhesive sheet is laminated between at least two substrates. For example, it can be used when laminating a copper foil and a support film such as polyimide. For example, it is a laminate in which an adhesive layer is formed on a first substrate using an electronic material that is the adhesive of the present invention, or a laminate in which a second substrate is further laminated on the adhesive layer.
The substrate is not particularly limited and may be, for example, a sheet or plate-like substrate, and may include conventionally known plastic films, metal foils, etc. When two substrates are used, they may be the same or different.
The adhesive can also be impregnated into a fiber substrate, semi-cured (B-staged) by heating or the like, laminated to a metal foil or plastic film, and cured to be used as an adhesive sheet. As the fiber substrate, well-known materials used in various laminates for electrical insulating materials can be used. Examples of the material include inorganic fibers such as E-glass, S-glass, low dielectric glass, and Q-glass; organic fibers such as low dielectric glass polyimide, polyester, and tetrafluoroethylene; and mixtures thereof. In particular, from the viewpoint of dielectric properties, inorganic fibers are preferred, and low dielectric glass and Q-glass are more preferred.
In the electronic material of the present invention, when the adhesive is impregnated into a fiber substrate, which is a support film, the adhesive forms a continuous adhesive layer, and thus the adhesive layer has a substrate therein, which is one of the usage forms of the electronic material of the present invention. Of course, the adhesive sheet may be a laminate in which the sheet-like substrate and the adhesive layer are separate.

When the adhesive is thermosetting, the adhesive sheet using the adhesive is also called a thermosetting adhesive sheet, and the layer made of the adhesive is called a thermosetting adhesive layer.
The following describes the case where a thermosetting adhesive sheet with a release substrate is used, in which one side of the thermosetting adhesive sheet is covered with a release substrate and the other side is covered with a sheet-like substrate (e.g., a polyimide film or a polyester film).
The release substrate is peeled off from the thermosetting adhesive sheet with the release substrate. An adherend (for example, the circuit surface side of a printed wiring board having a conductive circuit) is placed on the exposed thermosetting adhesive layer. Next, the thermosetting adhesive layer sandwiched between the sheet-like substrate and the adherend is thermally cured by applying heat and pressure, and the thermosetting adhesive layer becomes a sheet-like cured product.
In this way, a printed wiring board with a protective sheet can be obtained in which the circuit surface of a printed wiring board having a conductive circuit is protected by a sheet-like base material (protective sheet) via the sheet-like cured product.

Next, a case where a thermosetting adhesive sheet with a release substrate, in which both sides of a thermosetting adhesive sheet are covered with two release substrates, will be described.
One of the release substrates is peeled off from the thermosetting adhesive sheet with the release substrate. An adherend (e.g., a polyimide film or a polyester film) is placed on the exposed thermosetting adhesive layer. The other release substrate that covered the other side of the thermosetting adhesive layer is peeled off. Another adherend (e.g., the circuit side of a printed wiring board having a conductive circuit) is placed on the exposed thermosetting adhesive layer. Next, the thermosetting adhesive layer sandwiched between the two adherends is thermally cured by applying heat and pressure. After the circuit side of a printed wiring board having a conductive circuit is placed on the side from which the release substrate was first peeled off, a polyimide film or a polyester film can also be placed on the other side of the thermosetting adhesive layer.

An example of a printed wiring board laminate having a conductive circuit (hereinafter also referred to as a wiring board) is a flexible printed wiring board in which a conductive circuit is formed on a flexible, insulating plastic film such as polyester or polyimide.
As a method for providing a conductive circuit, for example, a photosensitive etching resist layer can be formed on the copper foil of a flexible copper-clad board, which is made by providing copper foil on a base film with or without an adhesive layer, exposing it to light through a mask film having a circuit pattern to harden only the exposed areas, and then removing the copper foil in the unexposed areas by etching, and then peeling off the remaining resist layer, thereby forming a conductive circuit from the copper foil.
Alternatively, only the necessary circuits may be provided on a base film by means of sputtering, plating, or the like.
Alternatively, a conductive ink containing silver or copper particles may be used to form a conductive circuit on a base film by a printing technique.

<Multi-layering of multiple flexible printed wiring>
The thermosetting adhesive sheet of the present invention is preferably used for producing a printed wiring board with a protective sheet, and can also be used as follows.
The thermosetting adhesive sheet of the present invention can also be sandwiched between a plurality of flexible printed wirings and heated and pressed to cure the thermosetting adhesive sheet, thereby obtaining a multi-layer flexible printed wiring board.

<Lamination of base film and copper foil for flexible printed wiring boards>
For example, the thermosetting adhesive sheet of the present invention can be sandwiched between a polyimide film and a copper foil, and the thermosetting adhesive sheet can be cured by applying heat and pressure.

<Conductive adhesive sheet>
The thermosetting adhesive sheet of the present invention can be used as a conductive thermosetting adhesive sheet formed by dispersing a thermosetting composition containing a polyimide resin, a curing agent, a specific amount of an alkali metal compound, and a conductive metal filler such as copper or silver, or a conductive filler such as carbon, in the form of a sheet.

<Electromagnetic wave shield>
Furthermore, the thermosetting adhesive sheet of the present invention can be used as an electromagnetic wave shield by forming a multilayer structure with an insulating layer using the conductive thermosetting adhesive sheet prepared above. In addition to the conductive layer portion, the thermosetting adhesive sheet of the present invention can also be used as an insulating layer.

<Thermal conductive adhesive sheet>
Furthermore, the thermosetting adhesive sheet of the present invention can be used as a thermally conductive thermosetting adhesive sheet obtained by dispersing and blending a polyimide resin, a curing agent, a specific amount of an alkali metal compound, and a thermally conductive inorganic filler, a metal filler, etc., and forming the dispersed thermosetting composition into a sheet shape.

The present invention will be explained in more detail below with reference to examples and comparative examples. In the examples and comparative examples, parts and percentages refer to parts by mass and percentages by mass unless otherwise specified.

<Method of measuring number average molecular weight (Mn) and mass average molecular weight (Mw)>
The measurements of Mn and Mw were performed using a GPC (gel permeation chromatography) "HPC-8020" manufactured by Tosoh Corporation. GPC is a liquid chromatography that separates and quantifies substances dissolved in a solvent (THF; tetrahydrofuran) based on the difference in their molecular size. The measurements in the present invention were performed using two "LF-604" columns (manufactured by Showa Denko K.K.: GPC column for rapid analysis: 6 mm ID x 150 mm size) connected in series, at a flow rate of 0.6 ml/min and a column temperature of 40°C, and the number average molecular weight (Mn) and mass average molecular weight (Mw) were determined in terms of polystyrene.

The abbreviations of the compounds used in the examples are as follows.
MED-J: 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane Product name: Curehard MED-J (manufactured by Kumiai Chemical Co., Ltd.)
DMDO: 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenyl ether (Tokyo Chemical Industry Co., Ltd.)
ODA: 4,4'-diaminodiphenyl ether manufactured by Wakayama Seika Kogyo Co., Ltd. Dimer diamine: product name Priamine 1075 (manufactured by Croda Japan Co., Ltd.)
6FDA: 2,2-bis(3,3',4,4'-tetracarboxyphenyl) manufactured by Wakayama Seika Kogyo Co., Ltd. BPAF: 9,9'-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride manufactured by JFE Chemical Corporation BISDA: 1',2'-dianhydride;4,4'-[4,4'-(propane-2,2-diyl)diphenoxy]diphthalic dianhydride manufactured by SABIC Japan BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride manufactured by Mitsubishi Chemical Corporation α-BPDA: 2,3,3',4'-biphenyltetracarboxylic dianhydride manufactured by JFE Chemical Corporation

(Production Example 1) Production of polyimide resin (1) 483 parts of cyclohexanone and 119 parts of 6FDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 34 parts of dimer diamine were dropped over 1 hour, and then 54 parts of MED-J were dropped, and the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain a polyimide resin (1) having a number average molecular weight of about 16,929 and a mass average molecular weight of about 32,831. The resin solid content concentration was 30%.

(Production Example 2) Production of polyimide resin (2) 483 parts of cyclohexanone and 120 parts of BPAF were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 33 parts of dimer diamine were dropped over 1 hour, and then 52 parts of MED-J were dropped, and the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain polyimide resin (2) having a number average molecular weight of about 17,389 and a mass average molecular weight of about 34,331. The resin solid content concentration was 30%.

(Production Example 3) Production of polyimide resin (3) 483 parts of cyclohexanone and 126 parts of BISDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 31 parts of dimer diamine were dropped over 1 hour, and then 49 parts of MED-J were dropped, and the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain a polyimide resin (3) having a number average molecular weight of about 16,075 and a mass average molecular weight of about 32,621. The resin solid content concentration was 30%.

(Production Example 4) Production of polyimide resin (4) 483 parts of cyclohexanone and 97 parts of BPDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 42 parts of dimer diamine were dropped over 1 hour, and then 66 parts of MED-J were dropped, and the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain polyimide resin (4) having a number average molecular weight of about 12,929 and a mass average molecular weight of about 25,180. The resin solid content concentration was 30%.

(Production Example 5) Production of polyimide resin (5) 483 parts of cyclohexanone and 97 parts of α-BPDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 42 parts of dimer diamine were dropped over 1 hour, and then 66 parts of MED-J were dropped, and the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain polyimide resin (5) having a number average molecular weight of about 13,156 and a mass average molecular weight of about 26,735. The resin solid content concentration was 30%.

(Production Example 6) Production of polyimide resin (6) 483 parts of cyclohexanone and 125 parts of BISDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100 ° C. while stirring under a nitrogen stream. 30 parts of dimer diamine were dropped over 1 hour, and then 51 parts of DMDO were dropped, and the temperature was raised to 140 ° C. and a dehydration reaction was carried out for 14 hours to obtain a polyimide resin (6) having a number average molecular weight of about 13,489 and a mass average molecular weight of about 26,809. The resin solid content concentration was 30%.

(Production Example 7) Production of polyimide resin (7) 483 parts of cyclohexanone and 126 parts of 6FDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 8 parts of dimer diamine were dropped over 1 hour, and then 72 parts of MED-J were dropped, and the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain a polyimide resin (7) having a number average molecular weight of about 11,832 and a mass average molecular weight of about 23,154. The resin solid content concentration was 30%.

(Production Example 8) Production of polyimide resin (8) 483 parts of cyclohexanone and 109 parts of 6FDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100 ° C. while stirring under a nitrogen stream. 64 parts of dimer diamine were dropped over 1 hour, and then 32 parts of MED-J were dropped, and the temperature was raised to 140 ° C. and a dehydration reaction was carried out for 14 hours to obtain a polyimide resin (8) having a number average molecular weight of about 14,320 and a mass average molecular weight of about 28,920. The resin solid content concentration was 30%.

(Production Example 9) Production of polyimide resin (9) 483 parts of cyclohexanone and 129 parts of 6FDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 77 parts of MED-J was dropped, the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain polyimide resin (9) having a number average molecular weight of about 11,562 and a mass average molecular weight of about 23,145. The resin solid content concentration was 30%.

(Production Example 10) Production of polyimide resin (10) 483 parts of cyclohexanone and 144 parts of 6FDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 62 parts of ODA were dropped, the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain a polyimide resin (10) having a number average molecular weight of about 13,533 and a mass average molecular weight of about 27,513. The resin solid content concentration was 30%.

(Production Example 11) Production of polyimide resin (11) 483 parts of cyclohexanone and 131 parts of 6FDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 30 parts of dimer diamine were dropped over 1 hour, and then 45 parts of ODA were dropped, and the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain a polyimide resin (11) having a number average molecular weight of about 11,966 and a mass average molecular weight of about 23,682. The resin solid content concentration was 30%.

(Production Example 12) Production of polyimide resin (12) 483 parts of cyclohexanone and 150 parts of BISDA were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas inlet tube, and the temperature was raised to 100°C while stirring under a nitrogen stream. 56 parts of ODA were dropped, the temperature was raised to 140°C and a dehydration reaction was carried out for 14 hours to obtain a polyimide resin (12) having a number average molecular weight of about 14,344 and a mass average molecular weight of about 28,690. The resin solid content concentration was 30%.

[Example 1]
The polyimide resin (1) obtained in Production Example 1 was uniformly coated on a polyester film that had been subjected to a release treatment using a blade coater so that the film thickness after drying would be 50 μm, and then dried. After drying, the film-like polyimide resin was peeled off from the polyester film to obtain an adhesive sheet.
[Examples 2 to 9, Comparative Examples 1 to 3]
An adhesive sheet was obtained in the same manner as in Example 1, except that the materials and amounts thereof shown in Table 1 were used.

(Measurement of glass transition temperature Tg)
For the obtained adhesive sheet, a "Differential Scanning Calorimeter DSC-60 PLUS" manufactured by Shimadzu Corporation was used under conditions of a starting temperature of 25°C, an ending temperature of 250°C, and a heating rate of 10.0°C/min. After the first heating, the sample was rapidly cooled to the starting temperature, and measurements were made from the peak value measured in the second cycle under the same conditions, using 10 mg of the sample.

(Evaluation of wettability)
The appearance of the obtained adhesive sheet was visually observed and evaluated according to the following criteria.
◎: No small air bubble patterns with a diameter of 1 mm or less are observed (very good)
○: Some small bubbles with a diameter of 1 mm or less are observed (good)
△: Numerous small bubble-like patterns with a diameter of 1 mm or less are observed (usable)
×: Numerous large bubble-like patterns with a diameter of 1 mm or more are observed (unusable)

(Evaluation of relative dielectric constant)
Three test pieces were set in a dielectric constant measuring device "ADMS01Oc" manufactured by AET Corporation, and the dielectric constant was determined by a cavity resonator method at a measurement temperature of 23°C and a measurement frequency of 10 GHz, and was evaluated according to the following criteria.
◎: Dielectric constant less than 2.7 (very good)
○: Dielectric constant is 2.7 or more and less than 2.8 (good)
△: Dielectric constant is 2.8 or more and less than 3.1 (usable)
×: Relative permittivity 3.1 or more (unusable)

(Evaluation of dielectric tangent)
Three test pieces were set in a dielectric constant measuring device "ADMS01Oc" manufactured by AET Corporation, and the dielectric loss tangent at a measurement temperature of 23°C and a measurement frequency of 10 GHz was determined by a cavity resonator method, and evaluated according to the following criteria.
◎: Dielectric loss tangent less than 0.005 (very good)
○: Dielectric loss tangent 0.005 or more and less than 0.007 (good)
△: Dielectric loss tangent 0.007 or more and less than 0.015 (usable)
×: Dielectric tangent 0.015 or more (unusable)

(Preparation of adhesive sheet with copper foil substrate)
An adhesive sheet with a substrate was produced by overlapping the treated side of an 18 μm thick electrolytic copper foil (product name "F2-WS", manufactured by Furukawa Circuit Foil Co., Ltd.) on the adhesive surface of the adhesive sheet produced in Example 1, hot pressing the foil under conditions of a pressure of 10 MPa, 180° C., and 1 minute, and then further heating the foil at 200° C. for 1 hour.

(Preparation of adhesive sheet with polyimide film substrate)
Each of the polyimide resins obtained in Production Examples 1 to 12 was applied to Kapton® H type (manufactured by DuPont-Toray Co., Ltd.) using a blade coater so that the thickness after drying was 30 μm, and then heated at 200° C. for 30 minutes to obtain an adhesive sheet. The obtained adhesive sheet with polyimide film substrate was evaluated for wettability in the same manner as for the polyester film that had been subjected to the release treatment described above. The results are shown in Table 1.

(Preparation of Laminate)
The treated side of the electrolytic copper foil (F2-WS) was placed on the adhesive side of the polyimide film-backed adhesive sheet, and then hot-pressed at a pressure of 10 MPa and 200° C. for 1 minute to produce a laminate.

As shown in Table 1, the adhesive sheet obtained from the electronic material of the present invention has good wettability, which makes it easy to prepare a uniform polyimide resin, good workability, excellent dielectric properties such as relative dielectric constant and dielectric loss tangent, and a relatively high glass transition temperature.
In particular, Examples 1 to 8 in which 10 to 200 parts of dimer diamine was used in combination with the aromatic amine (A-1) exhibited excellent dielectric properties.
Among them, Examples 1 to 5, in which the content is 40% by mass or more and 100% by mass or less, achieve both excellent dielectric properties and a high glass transition temperature.
Among them, Example 1, which used a fluorine-containing polycarboxylic anhydride, had particularly excellent dielectric properties.

(Printed circuit board manufacturing)
The adhesive composition according to Example 1 was applied to Kapton (R) H type with a blade coater so that the thickness after drying was 30 μm, and dried at 180 ° C for 3 minutes to obtain an adhesive sheet. Next, the treated surface of the electrolytic copper foil (F2-WS) was superimposed on the adhesive surface of the adhesive sheet, and the laminate was pressed with a laminating roll at 180 ° C, and then treated at 200 ° C for 2 hours to obtain a laminate. The copper surface of this laminate was soft etched to form a copper circuit, and the polyimide surface of the adhesive sheet with the substrate obtained by the above method was further superimposed thereon, and the circuit was hot-pressed under conditions of a pressure of 10 MPa, 180 ° C, and 1 minute, and then further heated at 200 ° C for 1 hour, thereby producing a flexible printed wiring board. It was also confirmed that flexible printed wiring boards could be produced in the same manner for the adhesive compositions of other Examples.

Claims (8)

The reaction product comprises an aromatic diamine (A-1) represented by the following general formula, a diamine including a dimer diamine , and a polycarboxylic acid ,
the amount of the dimer diamine is 10 to 200 parts by mass relative to 100 parts by mass of the aromatic diamine (A-1);
The electronic material includes at least one polycarboxylic acid selected from the group consisting of 2,2-bis(3,3',4,4'-tetracarboxyphenyl)tetrafluoropropane dianhydride, 9,9'-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 1',2'-dianhydride;4,4'-[4,4'-(propane-2,2-diyl)diphenoxy]diphthalic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 2,3,3',4'-biphenyltetracarboxylic dianhydride.
(In the formula, X represents a single bond, —CH ₂ —, —SO ₂ —, —C(═O)—, —O—, —O—C ₆ H ₄ —C(CH ₃ ) ₂ —C ₆ H ₄ —O—, —COO—(CH ₂ )l-OCO—, or —COO—CH ₂ —CH(—O—C(═O)—CH ₃ )—CH ₂ —OCO—, and l represents 1 to 20.) The electronic material according to claim 1 , further comprising a crosslinking agent and/or an organic solvent. The electronic material according to claim 1 or 2 , which is an adhesive. An adhesive layer formed by heating the electronic material according to claim 3 . An adhesive sheet comprising the adhesive layer according to claim 4 and a support film. A laminate comprising the adhesive layer according to claim 4 and a substrate. 7. The laminate according to claim 6 , wherein the substrate is a copper foil and/or an insulating sheet. 8. A printed wiring board laminate comprising the laminate according to claim 6 or 7 , which further comprises a copper foil and further comprises a circuit pattern provided on said copper foil.