JP2007308710A - Resin paste and flexible wiring board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin paste excellent in properties required for a protective film of a flexible wiring board such as low warpage, flexibility, adhesivity to a sealing material, solvent resistance, chemical resistance, heat resistance, electric characteristics, moisture resistance, workability and economical efficiency, which prevents plating components from penetrating to the edge of the protective film, and prevents a plating layer from diffusing to the wiring and disappearing; and to provide a flexible wiring board using the resin paste. <P>SOLUTION: This resin paste for a protective film of the flexible wiring board employing COF mounting system or the like for forming the protective film of a plate-treated wiring pattern comprises a resin of a thermosetting resin obtained by using diisocyanates expressed by formula (VI'), an inorganic microparticles including silica microparticles, an epoxy resin and an organic solvent including γ-butyrolactone, and gives a cured film having tensile modulus of elasticity of 0.5 GPa or lower, and tensile elongation of 50% or more when heated at 80-130°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a resin paste for a protective film of a flexible wiring board and a flexible wiring board using the same.

  Conventionally, in flexible wiring boards using mounting methods such as FC, TAB, and COF, a thermosetting resin paste is screen-printed except for rigid wiring boards, IC chips, electronic components, or wiring pattern portions connected to LCD panels. Then, after forming a protective film by thermosetting, the connected wiring pattern portion is generally plated with Au or Sn. However, in this plating step, the plating component permeates from the printed / cured protective film end, which causes problems such as corrosion of the wiring pattern and peeling of the protective film end.

  On the other hand, in recent years, the wiring pitch of flexible wiring boards has been further refined in response to miniaturization, thinning, and speeding up of electronic devices, and the above-described protective film end portions are used to maintain or improve reliability. There is a need for a thermosetting resin paste that does not allow any plating component to penetrate into the substrate and a flexible wiring board using such a thermosetting resin paste.

  As a method for solving this problem, all the wiring pattern portions of the flexible wiring board are pre-plated, and then the thermosetting resin paste is screen-printed and heat-cured except for the connected wiring pattern portions to form a protective film. There is a pre-plating method to obtain. In this method, since the protective film does not pass through the plating step, the plating component does not penetrate into the protective film end.

  However, since many conventional thermosetting resin pastes require a relatively high temperature (140 ° C. or higher) in order to form a protective film, in the pre-plating method, due to heat at the time of curing the paste, There is a problem that the plating layer diffuses into Cu of the wiring and is alloyed. On the other hand, when the pre-plating method is performed using a thermosetting resin paste that forms a protective film at a relatively low temperature (about 130 ° C.), the diffusion of the plating layer can be suppressed, but the warpage and flexibility of the protective film are suppressed. It was inferior to.

  The present invention eliminates the above-mentioned problems of the prior art, eliminates the penetration of the plating component into the edge of the protective film, and prevents the plating layer from diffusing into the wiring, and is necessary as a protective film for a flexible wiring board. Resin paste for protective films of flexible wiring boards with excellent low warpage, flexibility, adhesion to sealing materials, solvent and chemical resistance, heat resistance, electrical properties, moisture resistance, workability and economy It is to provide. The present invention is particularly useful as a resin paste for a protective film on the surface of a flexible wiring board in which all wiring patterns are plated. Furthermore, this invention provides the flexible wiring board using the resin paste for protective films of these flexible wiring boards.

  The present invention is a resin paste containing a resin and inorganic fine particles and / or organic fine particles. When the resin paste is heated at 80 to 130 ° C., the tensile elastic modulus at room temperature is 0.5 GPa or less, and A resin paste for a protective film of a flexible wiring board, wherein a cured film having a tensile elongation of 50% or more is obtained.

  Moreover, this invention is resin resin paste for said flexible wiring boards in which the said resin contains resin containing an imide bond, and resin containing the said imide bond is Formula (I):

A resin having a repeating unit represented by:
Formula (II):

A resin having a repeating unit represented by:
And formula (III):

A resin having a repeating unit represented by the formula:
A plurality of R's are each independently an alkylene group having 1 to 18 carbon atoms,
m and n are each independently an integer of 1 to 20,
X is a divalent organic group,
Y ¹ is —CH ₂ —, —CO—, —SO ₂ —, or —O—,
Y ² is a group:

The resin paste for a protective film of the flexible wiring board, which is at least one selected from the group consisting of:

  The present invention provides the flexible wiring, wherein the resin paste has a viscosity of 0.5 Pa · s to 500 Pa · s (rotary viscometer, 25 ° C., 10 rpm) and a thixotropic coefficient of 1.1 or more. A resin paste for a protective film of a board, a 5% thermal weight loss temperature of the cured film is a resin paste for a protective film of a flexible wiring board having a temperature of 250 ° C. or more, and the resin is a thermosetting resin This is a resin paste for a protective film of a flexible wiring board.

  Furthermore, the present invention is a flexible wiring board in which all of the wiring pattern portion using the cured film of the resin paste of the protective film resin paste of the flexible wiring board as a protective film is plated.

    The resin paste of the present invention has low warpage, flexibility and sealing required as a protective film for a flexible wiring board without the penetration of the plating component into the edge of the protective film and without the plating layer diffusing into the wiring. It has excellent adhesion to materials, solvent resistance and chemical resistance, heat resistance, electrical properties, moisture resistance, workability and economy.

  Moreover, the flexible wiring board using the resin paste of this invention is a flexible wiring board which has said outstanding characteristic.

  The resin paste of the present invention is characterized in that when heated at 80 to 130 ° C., a cured film having a tensile elastic modulus at normal temperature of 0.5 GPa or less and a tensile elongation of 50% or more is obtained. The temperature range in the production | generation of a cured film will not be specifically limited if it is in said range. The heating time is generally a time employed for forming the surface protective film of the flexible wiring board, and is, for example, 60 to 150 minutes, more preferably 80 to 120 minutes. The heating temperature and time can be, for example, 120 ° C. for 120 minutes. The above temperature range is a temperature range when a cured film is generated in order to measure the tensile modulus and tensile elongation, and is different from the conditions for forming the protective film on the surface of the flexible wiring board in the manufacturing process. May be. However, when the protective film of the wiring pattern plated in the above temperature range is formed using the resin paste of the present invention, the plating layer does not diffuse and disappear. Here, the fact that the plating layer does not diffuse means that the thickness of the plated layer after heating for forming the cured film is less than 50% of the thickness of the plated layer before heating.

  The resin paste of the present invention, which is a cured film under the above heating conditions, has a tensile elastic modulus of 0.5 GPa or less at room temperature, preferably 0.3 GPa or less, more preferably 0.2 GPa or less. In this specification, normal temperature is 25-40 degreeC, for example, can be set as the measured value in 25 degreeC. When the tensile modulus of the cured film is within this range, preferable warpage and flexibility as a protective film for a flexible wiring board can be obtained. Moreover, the resin paste of the present invention has a tensile elongation of 50% or more at room temperature, preferably 80% or more when it is a cured film under the above heating conditions. When the tensile elongation rate of the cured film is within this range, flexibility and folding resistance preferable as a protective film for a flexible wiring board can be obtained. The tensile modulus and the tensile elongation were obtained by forming a cured film having a film thickness of about 30 μm, a width of 1 mm, and a length of 60 mm under the above heating conditions, and using the obtained cured film, a length between chucks of 20 mm, The value obtained by conducting a tensile test under the condition of a pulling speed of 5 mm / min.

  The resin paste of the present invention contains (A) a resin and (B) inorganic and / or organic fine particles as essential components.

[(A) component: resin]
As the resin of component (A), epoxy resin having a butadiene structure or silicon structure, phenol resin, acrylic resin, polyurethane, polybutadiene, water-added polybutadiene, polyester, polycarbonate, polyether, polysulfone, polytetrafluororesin, polysilicone, Examples include melamine resin, polyamide, polyamideimide, and polyimide. These can be used alone or in combination of two or more. Among these resins, resins containing imide bonds such as polyimide and polyamideimide are preferable because they are excellent in heat resistance, electrical properties, moisture resistance, solvent resistance and chemical resistance.

  In the present invention, the resin containing an imide bond that can be used as the component (A) is a resin containing an imide bond as an essential component, and is not limited as long as it satisfies the object of the present invention. (A) one or more compounds selected from (a) trivalent polycarboxylic acids having acid anhydride groups and derivatives thereof, and tetravalent polycarboxylic acids having acid anhydride groups, and (b) isocyanate compounds or amines Obtained by reacting with a compound.

  The trivalent polycarboxylic acid having an acid anhydride group as the component (a) and a derivative thereof are not particularly limited, and examples thereof include formulas (I ′) and (II ′):

Wherein R ′ represents hydrogen, an alkyl group having 1 to 10 carbon atoms or a phenyl group, and Y ¹ represents —CH ₂ —, —CO—, —SO ₂ —, or —O—. The compounds shown can be used. Trimellitic anhydride is particularly preferable from the viewpoint of heat resistance and cost.

  Although the tetravalent polycarboxylic acid having an acid anhydride group is not particularly limited, for example, the formula (III ′):

Wherein Y ² is a group:

Can be used. These can be used alone or in combination of two or more.

  In addition to these, as necessary, an aliphatic dicarboxylic acid (succinic acid, glutaric acid, adipic acid, azelaic acid, suberic acid, sebacic acid, decanedioic acid, dodecanedioic acid, dimer acid, etc.) Aromatic dicarboxylic acids (isophthalic acid, terephthalic acid, phthalic acid, naphthalenedicarboxylic acid, oxydibenzoic acid, etc.) can be used in combination. In this case, an amide bond is also formed in the molecular chain.

The isocyanate compound as component (b) is, for example,
Formula (VI ′):

(Where
A plurality of R's are each independently an alkylene group having 1 to 18 carbon atoms,
m and n are each independently an integer of 1 to 20), and can be used (hereinafter referred to as (b-1) compound).

  The compound represented by the formula (VI ′) is represented by the formula (IV ′):

(In the formula, a plurality of R's are each independently an alkylene group having 1 to 18 carbon atoms,
m is an integer of 1 to 20, and carbonate diols represented by
Formula (V ′):
OCN-X-NCO (V ')
It is obtained by reacting diisocyanates represented by the formula (wherein X is a divalent organic group). X in the diisocyanate of the formula (V ′) is, for example, an arylene such as an alkylene group having 1 to 20 carbon atoms or a phenylene group that is unsubstituted or substituted with a lower alkyl group having 1 to 5 carbon atoms such as a methyl group. Groups. The number of carbon atoms of the alkylene group is more preferably 1-18. A group having two aromatic rings such as diphenylmethane-4,4′-diyl group and diphenylsulfone-4,4′-diyl group is also preferable.

Examples of the carbonate diol represented by the above formula (IV) include:
α, ω-poly (hexamethylene carbonate) diol, α, ω-poly (3-methyl-pentamethylene carbonate) diol, and the like are listed, and examples of commercially available products include trade name PLACEL manufactured by Daicel Chemical Industries, Ltd. CD-205, 205PL, 205HL, 210, 210PL, 210HL, 220, 220PL, 220HL. These can be used alone or in combination of two or more.

  Examples of the diisocyanate represented by the above formula (V ′) include diphenylmethane-2,4′-diisocyanate; 3,2′-, 3,3′-, 4,2′-, 4,3′- 5,2'-, 5,3'-, 6,2'- or 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate; 3,2'-, 3,3'-, 4,2 ' -, 4,3'-, 5,2'-, 5,3'-, 6,2'- or 6,3'-diethyldiphenylmethane-2,4'-diisocyanate; 3,2'-, 3,3 '-, 4,2'-, 4,3'-, 5,2'-, 5,3'-, 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate; diphenylmethane- 4,4'-diisocyanate; diphenylmethane-3,3'-diisocyanate; diphenyl Diphenyl ether-4,4'-diisocyanate; benzophenone-4,4'-diisocyanate; diphenylsulfone-4,4'-diisocyanate; tolylene-2,4-diisocyanate; tolylene-2,6 M-xylylene diisocyanate; p-xylylene diisocyanate; naphthalene-2,6-diisocyanate; in formula (V ′) such as 4,4 ′-[2,2bis (4-phenoxyphenyl) propane] diisocyanate , X is preferably an aromatic polyisocyanate having an aromatic ring. These can be used alone or in combination of two or more.

  Further, the diisocyanates represented by the formula (V ′) may be hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate within the scope of the object of the present invention. , Transcyclohexane-1,4-diisocyanate, hydrogenated m-xylylene diisocyanate, lysine diisocyanate, or other aliphatic or alicyclic isocyanates, or trifunctional or higher polyisocyanates can be used.

  As the diisocyanate represented by the formula (V ′), a diisocyanate stabilized with a blocking agent necessary for avoiding aging may be used. Examples of the blocking agent include alcohol, phenol and oxime, but there is no particular limitation.

  The blending amount of the carbonate diol represented by the above formula (IV ′) and the diisocyanate represented by the formula (V ′) is such that the ratio of the number of hydroxyl groups to the number of isocyanate groups is isocyanate group / hydroxyl group = 1.01 or more. It is preferable to make it.

  The reaction of the carbonate diols represented by the above formula (IV ′) and the diisocyanates represented by the formula (V ′) can be carried out without solvent or in the presence of an organic solvent. The reaction temperature is preferably 60 to 200 ° C, more preferably 80 to 180 ° C. The reaction time can be appropriately selected depending on the scale of the batch, the reaction conditions employed, and the like. For example, it can be 2 to 5 hours on a 1 to 5 L flask scale.

  The number average molecular weight of the isocyanate compound of the compound (b-1) thus obtained is preferably 500 to 10,000, more preferably 1,000 to 9,500, and 1,500 to Particularly preferred is 9,000. When the number average molecular weight is less than 500, the warping property tends to be deteriorated. When the number average molecular weight exceeds 10,000, the reactivity of the isocyanate compound is lowered, and it tends to be difficult to obtain a polyimide resin.

  In the present specification, the number average molecular weight is a value measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve.

  As the isocyanate compound of component (b), a compound other than compound (b-1) (hereinafter referred to as compound (b-2)) can also be used.

  The compound (b-2) is not particularly limited as long as it is an isocyanate compound other than the compound (b-1), and examples thereof include diisocyanates represented by the formula (V ′) and trivalent or higher polyisocyanates. It is done. These can be used alone or in combination of two or more. A preferred range of the number average molecular weight of the isocyanate compound of the compound (b-2) is the same as that of the compound (b-1).

  In particular, from the viewpoint of heat resistance, it is preferable to use the compound (b-1) and the compound (b-2) in combination. In addition, when using a compound (b-1) and a compound (b-2) each independently, a compound (b-1) is used from points, such as a softness | flexibility as a protective film for flexible wiring boards, and curvature property. It is preferable to do.

  As compound (b-2), 50 to 100% by weight of the total amount is preferably aromatic polyisocyanate, and considering the balance of heat resistance, solubility, mechanical properties, cost, etc., 4, 4 '-Diphenylmethane diisocyanate is particularly preferred.

  When the compound (b-1) and the compound (b-2) are used in combination, the equivalent ratio of compound (b-1) / compound (b-2) is 0.1 / 0.9 to 0.9 / 0.1. Is preferable, 0.2 / 0.8 to 0.8 / 0.2 is more preferable, and 0.3 / 0.7 to 0.7 / 0.3 is particularly preferable. When the equivalence ratio is within this range, film properties such as good warpage, adhesion and good heat resistance can be obtained.

  Among the components (b), examples of the amine compound include compounds obtained by converting the isocyanate group in the isocyanate compound of the component (b) to an amino group. Conversion of the isocyanato group to an amino group can be performed by a known method. The preferred range of the number average molecular weight of the amine compound is the same as that of the above compound (b-1).

  The blending ratio of the trivalent polycarboxylic acid having an acid anhydride group of component (a) or a derivative thereof and / or the tetravalent polycarboxylic acid having acid anhydride group is the isocyanate group in component (b). Preferably, the ratio of the total number of carboxyl groups and acid anhydride groups in component (a) to the total number of is 0.6 to 1.4, preferably 0.7 to 1.3. It is more preferable that the ratio is 0.8 to 1.2. When this ratio is less than 0.6 or exceeds 1.4, it tends to be difficult to increase the molecular weight of the resin containing polyimide bonds.

In the case where the compound represented by formula (I ′) is used as the component (a) and the compound (b-1) is used as the component (b),
Formula (I):

(Wherein R, X, m, and n are as defined above), a polyamideimide resin having a repeating unit can be obtained.

When the compound represented by the formula (II ′) is used as the component (a) and the compound (b-1) is used as the component (b),
Formula (II):

(Wherein R, X, m, n, and Y ¹ are as defined above), a polyamideimide resin having a repeating unit can be obtained.

When the compound represented by the formula (III ′) is used as the component (a) and the compound (b-1) is used as the component (b),
Formula (III):

(Wherein, R, X, m, n, and Y ² are as defined above) can be obtained.

  In the present invention, (a) a trivalent polycarboxylic acid having an acid anhydride group and a derivative thereof, and a tetravalent having an acid anhydride group in the process for producing a resin containing an imide bond used as the component (A) The reaction between one or more compounds selected from polycarboxylic acids and (b) an isocyanate compound or an amine compound is carried out by using a carbon dioxide gas generated free in the presence of an organic solvent, preferably a non-nitrogen-containing polar solvent. It can be carried out by heat condensation while removing from the reaction system.

  Examples of the non-nitrogen-containing polar solvent include ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether; sulfur-containing solvents such as dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfone, and sulfolane. Ester solvents such as γ-butyrolactone and cellosolve acetate; ketone solvents such as cyclohexanone and methyl ethyl ketone; aromatic hydrocarbon solvents such as toluene and xylene. These may be used alone or in combination of two or more. Can be used. It is preferable to select and use a solvent that dissolves the resin to be formed. After the synthesis, it is preferable to use a suitable paste solvent as it is. Γ-Butyrolactone is the most preferable because it is highly volatile, can impart low-temperature curability, and reacts efficiently in a homogeneous system. It is preferable that the usage-amount of a solvent shall be 0.8 to 5.0 times (weight ratio) of resin containing the imide bond to produce | generate. If it is less than 0.8 times, the viscosity at the time of synthesis is too high, and the synthesis tends to be difficult due to the inability to stir. If it exceeds 5.0 times, the reaction rate tends to decrease.

  The reaction temperature is preferably 80 to 210 ° C, more preferably 100 to 190 ° C, and particularly preferably 120 to 180 ° C. If it is less than 80 ° C., the reaction time becomes too long, and if it exceeds 210 ° C., a three-dimensional reaction occurs during the reaction and gelation tends to occur. The reaction time can be appropriately selected depending on the scale of the batch and the reaction conditions employed. If necessary, the reaction may be performed in the presence of a catalyst such as a tertiary amine, an alkali metal, an alkaline earth metal, a metal such as tin, zinc, titanium, cobalt, or a metalloid compound.

  The number average molecular weight of the resin containing an imide bond thus obtained is preferably 4,000 to 40,000, more preferably 5,000 to 38,000, and 6,000 to 36. Is particularly preferred. When the number average molecular weight is less than 4,000, film properties such as heat resistance tend to be lowered. When the number average molecular weight is more than 40,000, it is difficult to dissolve in a non-nitrogen-containing polar solvent and easily insolubilizes during synthesis. . In addition, workability tends to be inferior.

  In addition, the isocyanate group at the end of the resin can be blocked with a blocking agent such as alcohols, lactams, or oximes after completion of the synthesis.

  In addition, it is preferable to use a thermosetting resin as (A) component. In the case of the resin containing the imide bond, various epoxy resins can be added in addition to the component (A) in order to improve thermosetting. Examples of the epoxy resin include bisphenol A type epoxy resin (trade name Epicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd.), bisphenol F type epoxy resin (trade name YDF-170 manufactured by Toto Kasei Co., Ltd.), Phenol novolac type epoxy resin (trade name Epicoat 152, 154 of Yuka Shell Epoxy Co., Ltd .; trade name EPPN-201 manufactured by Nippon Kayaku Co., Ltd .; trade name DEN-438 manufactured by Dow Chemical Co., Ltd.), o -Cresol novolac type epoxy resins (trade names EOCN-125S, 103S, 104S, etc., manufactured by Nippon Kayaku Co., Ltd.), polyfunctional epoxy resins (trade names, Epon 1031S, manufactured by Yuka Shell Epoxy Co., Ltd .; Ciba Specialty Chemicals) Product name Araldite 0163 manufactured by Co., Ltd .; Product name Denacor E manufactured by Nagase Kasei Co., Ltd. -611, EX-614, EX-614B, EX-622, EX-512, EX-521, EX-421, EX-411, EX-321, etc.), amine type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) Product name Epicoat 604; Product name YH434 manufactured by Toto Kasei Co., Ltd. Product names TETRAD-X and TERRAD-C manufactured by Mitsubishi Gas Chemical Co., Ltd. Product names GAN manufactured by Nippon Kayaku Co., Ltd. (Trade name ELM-120 manufactured by Co., Ltd.), epoxy resin containing heterocyclic ring (trade name Araldite PT810 manufactured by Ciba Specialty Chemicals Co., Ltd.), alicyclic epoxy resin (ERL4234, 4299, 4221 manufactured by UCC) 4206 etc.) and the like can be used alone or in combination of two or more.

  Among these epoxy resins, amine-type epoxy resins having 3 or more epoxy groups in one molecule are particularly preferable in terms of improving solvent resistance, chemical resistance, and moisture resistance.

  These epoxy resins may contain an epoxy compound having only one epoxy group in one molecule. Such an epoxy compound is preferably used in the range of 0 to 20% by weight with respect to the total amount of the resin containing an imide bond as the component (A). Examples of such an epoxy compound include n-butyl glycidyl ether, phenyl glycidyl ether, dibromophenyl glycidyl ether, and dibromocresyl glycidyl ether. In addition, alicyclic epoxy compounds such as 3,4-epoxycyclohexyl and methyl (3,4-epoxycyclohexane) carboxylate can be used.

  The amount of these epoxy resins used is preferably 1 to 50 parts by weight, more preferably 2 to 45 parts by weight, and even more preferably 3 to 40 parts by weight with respect to 100 parts by weight of the resin containing an imide bond as the component (A). Part. When the compounding amount of the epoxy resin is less than 1 part by weight, the curability, solvent resistance, chemical resistance and moisture resistance tend to decrease, and when it exceeds 50 parts by weight, the heat resistance and viscosity stability tend to decrease. is there.

  As an addition method of the epoxy resin, the epoxy resin to be added may be added after being dissolved in the same organic solvent as the component (A) that dissolves the resin containing an imide bond, or added directly. May be.

[(B) component: inorganic and / or organic fine particles]
In addition, the inorganic and / or organic fine particles used as the component (B) in the present invention can be dispersed in the thermosetting resin or thermosetting resin solution of the component (A) to form a paste. There is no particular limitation.

Examples of the inorganic fine particles include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titania (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), zirconia (ZrO ₂ ), silicon nitride (Si ₃ N _4). ), Barium titanate (BaO · TiO ₂ ), barium carbonate (BaCO ₃ ), lead titanate (PbO · TiO ₂ ), lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT), gallium oxide (Ga ₂ O ₃ ), spinel (MgO.Al ₂ O ₃ ), mullite (3Al ₂ O ₃ .2SiO ₂ ), cordierite (2MgO.2Al ₂ O ₃ / 5SiO ₂ ), talc (3MgO.4SiO _2. H ₂ O), aluminum titanate _{(TiO 2 -Al 2 O 3)} , yttria-containing zirconia _{(Y 2 O 3 -ZrO 2)} , barium silicate (BaO · 8SiO ₂ ), Boron nitride (BN), calcium carbonate (CaCO ₃ ), calcium sulfate (CaSO ₄ ), zinc oxide (ZnO), magnesium titanate (MgO · TiO ₂ ), barium sulfate (BaSO ₄ ), organic bentonite, carbon ( C) etc. can be used and these 1 type (s) or 2 or more types can also be used.

  The organic fine particles are preferably heat-resistant resin fine particles having an amide bond, an imide bond, an ester bond or an ether bond. The heat resistant resin is preferably a polyimide resin or a precursor thereof, a polyamideimide resin or a precursor thereof, or fine particles of a polyamide resin from the viewpoint of heat resistance and mechanical properties.

  The heat resistant resin can be produced as follows. First, a polyimide resin can be obtained by reacting an aromatic tetracarboxylic dianhydride and an aromatic diamine compound.

  Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 2,2 ′, 3,3′-bisphenyl. Tetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 2,2-bis (3 , 4-Dicarboxyphenyl) propane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3 4-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxy) Phenyl) -Terdianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, 3,4,3 ', 4'-benzophenonetetracarboxylic dianhydride, 2,3,2', 3'- Benzophenone tetracarboxylic dianhydride, 2,3,3 ', 4'-benzophenone tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 2,3,6,7- Naphthalenetetracarboxylic dianhydride, 1,2,4,5-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,6-dichloronaphthalene-1, 4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-terolachlornaphthalene-1, 4,5,8-tetracarbo Acid dianhydride, phenanthrene-1,8,9,10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride, bis (3,4-dicarboxyphenyl) methylphenyl Silane dianhydride, bis (3,4-dicarboxyphenyl) diphenylsilane dianhydride, 1,4-bis (3,4-dicarboxyphenyldimethylsilyl) benzene dianhydride, 1,3-bis (3, 4-dicarboxyphenyl) -1,1,3,3-tetramethyldicyclohexane dianhydride, p-phenylenebis (trimellitic acid monoester anhydride), 2,2-bis (3,4-dicarboxy) Phenyl) hexafluoropropane dianhydride, 2,2-bis {4- (3,4-dicarboxyphenoxy) phenyl} hexafluoropropane dianhydride, 2 , 2-bis {4- (3,4-dicarboxyphenoxy) phenyl} propane dianhydride, 4,4-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 1,4-bis (2 -Hydroxyhexafluoroisopropyl) benzene bis (trimellitate anhydride), 1,3-bis (2-hydroxyhexafluoroisopropyl) benzene bis (trimellitate anhydride), 1,2- (ethylene) bis (trimellitate anhydride), 1 , 3- (trimethylene) bis (trimellitic anhydride), 1,4- (tetramethylene) bis (trimellitic anhydride), 1,5- (pentamethylene) bis (trimellitic anhydride), 1,6- (hexamethylene) ) Bis (trimellitate anhydride), 1,7- (heptamethylene) bis (trimellitate anhydride) 1,8- (octamethylene) bis (trimellitic anhydride), 1,9- (nonamethylene) bis (trimellitic anhydride), 1,10- (decamethylene) bis (trimellitic anhydride), 1,12- (dodeca) Methylene) bis (trimellitate anhydride), 1,16- (hexadecamethylene) bis (trimellitate anhydride), 1,18- (octadecamethylene) bis (trimellitate anhydride), etc. May be.

  In the aromatic tetracarboxylic dianhydride, a tetracarboxylic dianhydride other than the aromatic tetracarboxylic dianhydride may be added to the aromatic tetracarboxylic dianhydride in a range not exceeding 50 mol% of the aromatic tetracarboxylic dianhydride. Can be used. Examples of such tetracarboxylic dianhydrides include ethylene tetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic Acid dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, decahydronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 4,8-dimethyl-1,2 , 3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrrolidine-2, 3,4,5-tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, bis {exobicyclo [2,2,1] heptane-2,3-dicarboxylic anhydride Thing} sulfone, bishi Rho- (2,2,2) -oct (7) -ene-2,3,5,6-tetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3 -Cyclohexane-1,2-dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride and the like.

  Examples of the aromatic diamine compound include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3, 3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenyldifluoromethane, 4,4'-diaminodiphenyldifluoromethane, 3,3'-diaminodiphenylsulfone 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ketone, 3,4'-diaminodiphenyl ketone, 4,4 ' -Diaphragm Diphenyl ketone, 2,2-bis (3-aminophenyl) propane, 2,2-bis (3,4'-diaminophenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (3-aminophenyl) hexafluoropropane, 2,2-bis (3,4'-diaminophenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, 1,3-bis (3 -Aminophenyl) benzene, 1,4-bis (4-aminophenyl) benzene, 3,3 '-[1,4-phenylenebis (1-methylethylidene)] bisaniline, 3,4'-[1,4- Phenylenebis (1-methylethylidene)] bisaniline, 4,4 ′-[1,4-phenylenebis (1-methylethylidene)] bisaniline, 2,2-bis [ -(3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] hexafluoropropane, 2 , 2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4 There are-(3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, and the like, which may be used in combination.

  In the aromatic diamine compound, a diamine compound other than the aromatic diamine compound can be used in a range not exceeding 50 mol% of the aromatic diamine compound depending on the purpose. Examples of such diamine compounds include 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diamino. Heptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (3-aminopropyl) tetramethylpolysiloxane and the like.

  The aromatic tetracarboxylic dianhydride and the aromatic diamine compound are preferably reacted in an approximately equimolar amount from the viewpoint of film characteristics.

  The reaction between the aromatic tetracarboxylic dianhydride and the aromatic diamine compound is carried out in an organic solvent. Examples of the organic solvent include N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone, 1,3-dimethyl-2. -Nitrogen-containing compounds such as imidazolidinone; sulfur compounds such as sulfolane and dimethyl sulfoxide; γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-heptalactone, α-acetyl-γ-butyrolactone, ε-caprolactone, etc. Lactones; dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl (or diethyl, dipropyl, dibutyl) ether, triethylene glycol (or diethyl, dipropyl, dibutyl) ether, tetraethylene glycol dimethyl (or diethyl, dipropyl, dibutyl) E) ethers such as ether; ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetophenone; butanol, octyl alcohol, ethylene glycol, glycerin, diethylene glycol monomethyl (or monoethyl) ether, triethylene glycol monomethyl (or monoethyl) ether, Alcohols such as tetraethylene glycol monomethyl (or monoethyl) ether; phenols such as phenol, cresol, xylenol; esters such as ethyl acetate, butyl acetate, ethyl cellosolve acetate, butyl cellosolve acetate; toluene, xylene, diethylbenzene, cyclohexane, etc. Hydrocarbons: Halogenated charcoal such as trichloroethane, tetotachloroethane, monochlorobenzene Hydrogen fluorides and the like are used.

  These organic solvents are used alone or in combination. In consideration of solubility, low hygroscopicity, low temperature curability, environmental safety, etc., it is preferable to use lactones, ethers, ketones and the like.

  The reaction temperature is 80 ° C or lower, preferably 0 to 50 ° C. As the reaction proceeds, the reaction solution gradually thickens. In this case, polyamic acid which is a precursor of the polyimide resin is generated. This polyamic acid may be partially imidized, and this is also included in the polyimide resin precursor.

  The polyimide resin is selected by dehydrating and ring-closing the reactant (polyamic acid). Dehydration ring closure can be performed by a method of heat treatment at 120 ° C. to 250 ° C. (thermal imidization) or a method of using a dehydrating agent (chemical imidization). In the case of the heat treatment at 120 ° C. to 250 ° C., it is preferable to carry out while removing water generated by the dehydration reaction out of the system. At this time, water may be removed azeotropically using benzene, toluene, xylene or the like.

  In the method of performing dehydration and ring closure using a dehydrating agent, it is preferable to use an acid anhydride such as acetic anhydride, propionic anhydride or benzoic acid, a carbodiimide compound such as dicyclohexylcarbodiimide, or the like as the dehydrating agent. At this time, if necessary, a dehydration catalyst such as pyridine, isoquinoline, trimethylamine, or aminopyridineimidazole may be used. The dehydrating agent or the dehydrating catalyst is preferably used in an amount of 1 to 8 moles per mole of aromatic tetracarboxylic dianhydride.

  Polyamideimide resin or precursor thereof is trimellitic anhydride or trimellitic anhydride derivative (trimellitic anhydride derivative) instead of aromatic tetracarboxylic dianhydride in the production of polyimide resin or precursor thereof. And the like, and trivalent tricarboxylic acid anhydrides or derivatives thereof. Moreover, it can also manufacture using the diisocyanate compound corresponding to the diamine compound in which residues other than an amino group replace with an aromatic diamine compound and another diamine compound. Diisocyanate compounds that can be used include those obtained by reacting the aromatic diamine compound or other diamine compounds with phosgene or thionyl chloride.

  Polyamide resins are produced by reacting aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and phthalic acid, derivatives of these dichlorides, acid anhydrides, etc. with the above-mentioned aromatic diamine compounds or other diamine compounds. be able to.

  Examples of the heat resistant resin having an ester bond include a polyester resin, and examples of the polyester resin include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and phthalic acid, derivatives of these dichlorides, acid anhydrides, and the like. There are those obtained by reacting aromatic diol compounds such as 1,4-dihydroxybenzene, bisphenol F, bisphenol A, and 4,4'-dihydroxybiphenyl.

  As the polyamideimide resin, a polyamideimide resin obtained by reacting an aromatic tetracarboxylic dianhydride and an aromatic diamine compound containing isophthalic acid dihydrazide as essential components is preferably used. As the aromatic tetracarboxylic dianhydride and the aromatic diamine compound, those described above are used. The molar ratio of isophthalic acid dihydrazide in the aromatic diamine compound is preferably 1 to 100 mol%. If it is less than 1 mol%, the solubility in the modified polyamideimide resin tends to decrease, and if the content of isophthalic acid dihydrazide is large, the moisture resistance of the layer formed by the paste of the present invention tends to decrease. 80 mol% is more preferable, and 20-70 mol% is used especially preferably. This polyamide-imide resin can be obtained in the same manner as the synthesis of the polyimide resin, with respect to the compounding ratio of the aromatic tetracarboxylic dianhydride and the aromatic diamine compound, the organic solvent used, the synthesis method, and the like.

  The polyamideimide resin obtained by reacting trimellitic anhydride and, if necessary, dicarboxylic acid and polyisocyanate is likely to become insoluble in organic solvents when heated, and organic fine particles made of this polyamideimide resin should be used. You can also. About the manufacturing method of this polyamide imide resin, it can manufacture similarly to the manufacturing method of an above described polyamide imide resin.

  Examples of the fine particle forming method include a non-aqueous dispersion polymerization method (Japanese Patent Publication No. 60-48531, Japanese Patent Laid-Open No. 59-230018), and a precipitation polymerization method (Japanese Patent Laid-Open No. 59-108030, Japanese Patent Laid-Open No. 60). No. -22425), a method of mechanically pulverizing powder modified from a resin solution, a method of finely pulverizing a resin solution while adding the resin solution to a poor catalyst, a method of obtaining fine particles by drying a spray solution of a resin solution, a detergent Alternatively, there is a method in which a resin having a temperature dependency of solubility in a solvent in a resin solution is formed into fine particles.

  As the inorganic and / or organic fine particles in the present invention, those having an average particle size of 50 μm or less and a maximum particle size of 100 μm or less are preferably used. When the average particle diameter exceeds 50 μm, it becomes difficult to obtain a paste having a thixotropic coefficient of 1.1 or more, which will be described later, and when the maximum particle diameter exceeds 100 μm, the appearance and adhesion of the coating film tend to be insufficient. The average particle size is more preferably 30 μm or less, further preferably 10 μm or less, particularly preferably 1 μm or less, and the maximum particle size is more preferably 80 μm or less, still more preferably 60 μm or less, particularly preferably 40 μm or less.

[Resin paste]
The resin paste of the present invention can be produced by dissolving the resin as component (A) in an organic solvent to obtain a resin solution and dispersing inorganic and / or organic fine particles as component (B).

  In the resin paste of the present invention, the amount of inorganic and / or organic fine particles used as the component (B) is 1 to 90 parts by weight, more preferably 2 to 70, with respect to 100 parts by weight of the component (A). It is preferable to set it as the range of 3-50. When the amount is smaller than this, the viscosity and thixotropy coefficient of the paste are lowered, the stringing of the paste is increased, the flow of the paste after printing is increased, and the film thickness tends to be reduced. On the other hand, when the amount is larger than this, the viscosity and the thixotropy coefficient of the paste increase, and the transferability of the paste to the substrate tends to decrease, and voids and pinholes in the printed film tend to increase.

  As the organic solvent for dissolving the resin of component (A), an ether solvent such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether; a sulfur-containing solvent; For example, dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfone, sulfolane; ester solvents such as γ-butyrolactone, cellosolve acetate; ketone solvents such as cyclohexanone, methyl ethyl ketone; aromatic hydrocarbon solvents such as toluene, xylene, etc. These may be used alone or in combination of two or more. Since the solubility varies depending on the resin to be produced, a solvent capable of dissolving the resin is selected and used.

  As a method of dispersing inorganic and / or organic fine particles in a thermosetting resin solution, roll kneading, mixer mixing, etc., which are usually performed in the paint field, are applied and sufficient dispersion is performed. good.

  In the resin paste of the present invention, surfactants such as antifoaming agents and leveling agents, colorants such as dyes or pigments, heat stability, etc. are provided to improve workability during coating and film properties before and after film formation. Agents, antioxidants, flame retardants, and lubricants can also be added.

  The resin paste of the present invention preferably has a viscosity with a rotary viscometer of 0.5 Pa · s to 500 Pa · s at 25 ° C. and a thixotropic coefficient of 1.1 or more. If the viscosity is less than 0.5 Pa · s, the flow of the paste after printing tends to increase and the film thickness tends to be reduced. If the viscosity exceeds 500 Pa · s, the transferability of the paste to the substrate decreases. At the same time, voids and pinholes in the printed film tend to increase. When the thixotropy coefficient is less than 1.1, the stringing of the paste increases, the flow of the paste after printing increases, and the film thickness also tends to be reduced. The viscosity is more preferably 1 to 250, and particularly preferably 10 to 100. Further, the thixotropic coefficient is more preferably 1.2 or more, and particularly preferably 1.4 or more.

  Here, the viscosity of the resin paste is expressed as a viscosity at a rotation speed of 10 rpm measured with a sample amount of 0.2 ml or 0.5 ml using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE80U type). Also, the thixotropy coefficient (TI value) of the paste was applied only to the paste at the rotation speeds of 1 rpm and 10 rpm measured with a sample amount of 0.2 ml or 0.5 ml using an E type viscometer (manufactured by Toki Sangyo Co., Ltd., model RE80U) Viscosity is expressed as the ratio η1 / η10 of η1 and η10.

  Further, the 5% thermal weight loss temperature of the resin paste of the present invention as a cured film is preferably 250 ° C. or higher. If the 5% thermal weight loss temperature is less than 250 ° C., the cured film may be deformed and decomposed due to heat applied at the time of connection with a rigid wiring board, IC chip, electronic component or LCD panel. The 5% weight loss temperature is the same as the generation of a cured film for measurement of tensile modulus and the like, that is, 80 to 130 ° C., and the time for forming a protective film on the surface of a normal flexible wiring board. It heats within the range, forms a cured film with a film thickness of about 30 μm, and takes a value measured by the TG-DTA method in an air atmosphere at a heating rate of 10 ° C./min.

  The present invention also provides a flexible wiring board in which the above resin paste is screen-printed on a wiring pattern of a flexible wiring board and then thermally cured to form a cured film to form a protective film. In particular, it is suitable for use as a protective film on the surface of a flexible wiring board in which all of the wiring pattern portion is plated. The conditions for thermosetting are preferably 80 ° C. to 130 ° C., particularly preferably 90 ° C. to 120 ° C., from the viewpoint of preventing the diffusion of the plating layer and obtaining warpage and flexibility suitable as a protective film. It is not limited to this range, For example, it can also be made to harden | cure in the range of 50-200 degreeC, especially 50-140 degreeC. The heating time is 60 to 150 minutes, preferably 80 to 120 minutes from the viewpoint of preventing diffusion of the plating layer and obtaining warpage and flexibility suitable as a protective film, but is limited to this range. However, it can be cured in the range of 1 to 1000 minutes, for example, 5 to 300 minutes, especially 10 to 150 minutes.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

Example 1
In a 5-liter four-necked flask equipped with a stirrer, a cooling pipe with an oil / water separator, a nitrogen inlet pipe and a thermometer, PLACECELCD-220 (trade name of 1,6-hexanediol-based polycarbonate diol manufactured by Daicel Chemical Industries, Ltd.) 1000.0 g (0.50 mol) and 4,4′-diphenylmethane diisocyanate 250.27 g (1.00 mol) and γ-butyrolactone 833.51 g were charged, heated to 140 ° C., and reacted at 140 ° C. for 5 hours. The diisocyanate of compound (b-1) was obtained.

Furthermore, 358.29 g (1.00 mol) of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride as component (a) was added to this reaction solution, and 4,4 ′ as compound (b-2). -125.14 g (0.50 mol) of diphenylmethane diisocyanate and 58.497 g of γ-butyrolactone were charged, and the temperature was raised to 160 ° C., followed by reaction for 5 hours to obtain a resin having a number average molecular weight of 17,000 (formula In (III), R is all a hexamethylene group, X is a diphenylmethane-4,4′-diyl group, Y ² is a diphenylsulfone-3,3 ′, 4,4′-tetrayl group, m Is a resin having a repeating unit in which n is 1 and n is 1. The obtained resin was diluted with γ-butyrolactone to obtain a polyimide resin solution having a viscosity of 40 Pa · s and a nonvolatile content of 40% by weight. In addition, the molar ratio of compound (b-1) / compound (b-2) is 0.5 / 0.5.

  31.5 g of Aerosil 380 (Nippon Aerosil Co., Ltd., trade name, average particle size of 0.2 μm or less, silica fine particles) is added to 1000 g of the obtained polyimide resin solution, first coarsely kneaded, and then using a high-speed three roll. The kneading was repeated three times to perform the main kneading to obtain a polyimide resin paste in which silica fine particles were uniformly dispersed. This paste had a viscosity of 60 Pa · s and a TI value of 2.4.

Example 2
YH-434 (trade name of amine type epoxy resin manufactured by Toto Kasei Co., Ltd., epoxy equivalent of about 120, 4 epoxy groups / molecule) with respect to 100 parts by weight of the resin content of the polyimide resin paste obtained in Example 1 10 Part by weight was added and diluted with γ-butyrolactone to obtain a polyimide resin paste having a viscosity of 35 Pa · s, a TI value of 2.4, and a nonvolatile content of 40% by weight.

Example 3
In Example 2, instead of 10 parts by weight of YH-434, Epicoat 828 (trade name of bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent of about 189, 2 epoxy groups / molecule) 10 weights Except for the use of parts, the same operation as in Example 1 was performed to obtain a polyimide resin paste having a viscosity of 34 Pa · s, a TI value of 2.4, and a nonvolatile content of 40% by weight.

Comparative Example 1
In a flask similar to that in Example 1, 700 g (0.50 mol) of silicone diol BX16-001 (a trade name of dimethylpolysiloxane diol manufactured by Toray Dow Corning Silicone Co., Ltd.) and 4,4′-diphenylmethane diisocyanate 250 .27 g (1.00 mol), γ-butyrolactone (316.76 g) and N-methyl-2-pyrrolidone (316.76 g) were charged, the temperature was raised to 140 ° C., and the mixture was reacted at 140 ° C. for 3 hours. Furthermore, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride 358.29 g (1.00 mol) and 4,4′-diphenylmethane diisocyanate 125.14 g (0.50 mol) were added to this reaction solution. In addition, 269.75 g of γ-butyrolactone and 269.75 g of N-methyl-2-pyrrolidone were charged, heated to 160 ° C., and reacted for 4 hours to obtain a resin having a number average molecular weight of 15,000. The obtained resin was diluted with γ-butyrolactone to obtain a polyimide resin solution having a viscosity of 30 Pa · s and a nonvolatile content of 52% by weight.

  36.4 g of Aerosil 380 (Nippon Aerosil Co., Ltd., trade name, average particle size of 0.2 μm or less, silica fine particles) is added to 1000 g of the obtained polyimide resin solution, first coarsely kneaded, and then using a high-speed three roll. The kneading was repeated three times to perform the main kneading to obtain a polyimide resin paste in which silica fine particles were uniformly dispersed. This paste had a viscosity of 43 Pa · s and a TI value of 2.1.

Comparative Example 2
10 parts by weight of YH-434 is added to 100 parts by weight of the resin content of the polyimide resin paste obtained in Comparative Example 1, and diluted with γ-butyrolactone to obtain a polyimide resin having a viscosity of 25 Pa · s and a nonvolatile content of 52% by weight. A paste was obtained.

Comparative Example 3
Except for the flask being 3 L, in the same flask as in Example 1, 537.44 g (1.50 mol) 3,4′-diphenylmethane 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride 382.9 g (1.53 mol) of diisocyanate and 1380.51 g of γ-butyrolactone were charged, and the temperature was raised to 160 ° C. During the reaction, the varnish became cloudy and a uniform polyimide solution could not be obtained.

  The characteristics of the polyimide resin pastes obtained in the above examples and comparative examples were measured by the following methods, and the results are shown in Table 1.

(1) Tensile modulus and tensile elongation rate A cured film of polyimide resin paste having a film thickness of about 30 μm, a width of 1 mm, and a length of 60 mm was formed under heating conditions at 120 ° C. for 120 minutes, and the obtained cured film was used. A tensile test was performed at 25 ° C. under the conditions of a length between chucks of 20 mm and a tensile speed of 5 mm / min, and the tensile elastic modulus and tensile elongation were evaluated.

(2) Warpage property A two-layer flexible substrate made of a polyimide film having a thickness of 38 μm and Cu having a thickness of 12 μm is Sn-plated and cut into a size of 35 mm in length and 20 mm in width. On this base material, the obtained polyimide resin paste was printed, dried at 90 ° C. for 15 minutes, and then heated at 120 ° C. for 120 minutes in an air atmosphere. The obtained test piece (coating thickness: 15 μm) Was placed on a surface plate with the coated surface down, and the warp height was evaluated.

(3) Solvent resistance (2) The polyimide resin paste obtained on the substrate used for warpage is printed, dried at 90 ° C for 15 minutes, and then heated at 120 ° C for 120 minutes in an air atmosphere. About the obtained test piece (coating film thickness: 15 micrometers), the cured film was immersed in acetone at room temperature for 1 hour, and the following reference | standard evaluated the change of the coating film external appearance.
○: No change in appearance △: Partial change in appearance ×: Change in overall appearance

(4) Adhesiveness to the sealing material (2) The polyimide resin paste obtained is printed on the substrate used for warpage, dried at 90 ° C. for 15 minutes, and then heated at 120 ° C. for 120 minutes in an air atmosphere. Then, 0.06 g of epoxy-based sealing material (trade name CEL-C-5020 manufactured by Hitachi Chemical Co., Ltd.) was potted on the obtained test piece (coating film thickness: 15 μm), and 120 ° C. was 120 ° C. Heat at 150 ° C. for 120 minutes. The obtained test piece was bent so that the sealing material side was the outside, and the peeling mode was evaluated according to the following criteria.
○: Interfacial peeling of substrate / coating film Δ: Interfacial peeling of coating film / encapsulant ×: No adhesion

(5) Moisture resistance (pressure cooker test)
(2) After printing the polyimide resin paste obtained on the base material used for warpage and drying at 90 ° C. for 15 minutes, it was heated at 120 ° C. for 120 minutes in an air atmosphere. The film appearance change after a pressure cooker test (abbreviated as PCT, conditions 121 ° C., 2.0265 × 10 ⁵ Pa, 100 hours) was evaluated according to the following criteria.
○: No change in appearance △: Partial change in appearance ×: Change in overall appearance

(6) Change of Sn plating thickness (2) The obtained polyimide resin paste is printed so that an uncoated part is obtained on the base material used for warpage, dried at 90 ° C. for 15 minutes, and then air atmosphere Under heating at 120 ° C. for 120 minutes, a test piece having a coating thickness of 15 μm was obtained. The Sn plating thickness of the uncoated portion of the test piece was measured and evaluated according to the following criteria. The reduction rate of the Sn plating thickness is the rate of change of the Sn plating thickness before and after the paste is cured.
○: Reduction rate of Sn plating thickness is less than 50% ×: Reduction rate of Sn plating thickness is 50% or more

Claims (2)

Formula (VI ′) below:

(In the formula, each R is independently an alkylene group having 1 to 18 carbon atoms, X is a divalent organic group, and m and n are each independently an integer of 1 to 20) and a resin in a thermosetting resin obtained by using a diisocyanate represented, and inorganic fine particles comprising silica fine particles, an epoxy resin, seen containing an organic solvent containing γ- butyrolactone, the amount of the inorganic fine particles Is a resin paste of 1 to 90 parts by weight with respect to 100 parts by weight of the resin, and when the resin paste is heated at 80 to 130 ° C., the tensile elastic modulus at room temperature is 0.5 GPa or less, and the tensile elongation, characterized in that the resulting 50% or more in which the cured film, for forming a protective film of plated the wiring pattern, FC, a flexible wiring board using the TAB or COF mounting system A protective film for the resin paste. The flexible wiring board by which the wiring pattern part which used the cured film of the resin paste for protective films of the flexible wiring board of Claim 1 as the protective film was plated.