JP2008007756A - Viscoelastic resin composition, prepreg, conductor-clad laminate, resin-coated metal foil, and resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viscoelastic resin composition capable of being used for easily producing a wiring board material fully satisfying all of heat resistance, adhesion force, bending workability, and dimensional stability; and to provide a prepreg, a conductor-clad laminate, a resin-coated metal foil, and a resin film, all produced by using the viscoelastic resin composition. <P>SOLUTION: The viscoelastic resin composition contains an acrylic rubber polymer containing 1-15 mass% glycidyl methacrylate as monomer units and having a weight average molecular weight (Mw) of 300,000-1,000,000 and a glass transition temperature of -20°C to 0°C and a curing component other than the acrylic rubber polymer. The glass transition temperature of the resin composition after curing is in the range of 20°C to 60°C or 120°C to 160°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a viscoelastic resin composition, a prepreg, a conductor-clad laminate, a metal foil with resin, and a resin film.

  A wiring board material in which a glass cloth is impregnated with an epoxy resin is known. Such a wiring board material is inexpensive and can be bonded at a relatively low temperature. However, when the bending process is performed, a crack or the like is generated in the insulating layer portion, and the characteristic as the wiring board is remarkably deteriorated. Therefore, the usage is limited.

  Therefore, a polyester resin or a polyimide resin has been conventionally used as a wiring board material that can be bent. In recent years, copper-clad laminates using polyimide resins with good heat resistance and small heat shrinkage have become mainstream. However, copper-clad laminates using polyimide resin are superior in heat resistance at high temperatures, but have a large rate of dimensional change before and after moisture absorption and poor adhesion between the copper foil and the insulating layer. Wiring was easy to occur when receiving heat history.

  By the way, a copper clad laminate using polyimide resin is mainly a two-layer CCL type obtained by directly applying a polyimide precursor to a copper foil and condensing it at a high temperature, via a polyimide adhesive or other adhesive. And a three-layer CCL type in which a polyimide film is bonded together and a metalizing type in which a copper layer is deposited on a polyimide resin film by sputtering or plating. Although the two-layer CCL type is excellent in heat resistance, it requires a heating process at a high temperature for a long time, so that it is generally expensive and has poor productivity. The three-layer CCL type requires a high-temperature and high-pressure long-time bonding process at the time of bonding when a polyimide-based adhesive is used, resulting in poor productivity, and when other adhesives are used, the heat resistance is lowered. In addition, the metalizing type is disadvantageous in that it is difficult to increase the thickness of the copper foil due to the cost of forming the copper layer, it is difficult to obtain sufficient adhesion between copper and the insulating layer, and the adhesion reliability is poor. There is. Thus, the copper clad laminated board using a polyimide resin also has the problem that it is difficult to manufacture.

Recently, for the purpose of achieving both heat resistance and dimensional stability while enabling thermocompression bonding at a low temperature, a prepreg for a printed wiring board in which a fiber base material is impregnated with a resin composition comprising a specific polyimide resin and epoxy resin has been developed. It has been proposed (see, for example, Patent Document 1).
JP-A-8-193139

  However, even the prepreg described in Patent Document 1 does not have sufficient adhesion to the metal foil, and there is room for further improvement in order to obtain a high level of reliability as a wiring board material.

  The present invention has been made in view of the above circumstances, a viscoelastic resin composition capable of easily producing a wiring board material that sufficiently satisfies all of heat resistance, adhesion, bending workability, and dimensional stability, and It aims at providing the prepreg obtained using this viscoelastic resin composition, a conductor clad laminated board, metal foil with resin, and a resin film.

  In order to solve the above problems, the present inventors have intensively studied. As a result, an acrylic rubber polymer containing a specific amount of glycidyl methacrylate as a monomer unit, having a specific molecular weight and a specific glass transition temperature, and the acrylic rubber polymer. In the resin composition containing a curable component other than, by setting the acrylic rubber polymer and other curable components so that the glass transition temperature after curing is in a specific range, A viscoelastic resin composition excellent in impregnation into a substrate can be obtained, and a wiring board material produced from such a viscoelastic resin composition has sufficient heat resistance, adhesion, bending workability and dimensional stability. As a result, the present invention has been completed.

  That is, the present invention includes 1 to 15% by mass of glycidyl methacrylate as a monomer unit, has a weight average molecular weight (Mw) of 300,000 to 1,000,000 and a glass transition temperature in the range of −20 ° C. to 0 ° C. A viscoelastic resin composition containing an acrylic rubber polymer and a curable component other than the acrylic rubber polymer and having a glass transition temperature after curing in the range of 20 ° C to 60 ° C and 120 ° C to 160 ° C is provided. To do.

  Here, the content of glycidyl methacrylate is based on the total amount of the acrylic rubber polymer. Moreover, a weight average molecular weight means the value obtained by converting with the analytical curve which measured by gel permeation chromatography and created using standard polystyrene.

In the present invention, “after curing” means that the calorific value of the viscoelastic resin composition before curing measured using DSC (differential scanning calorimeter) is Q0 (J / g), DSC (differential scanning calorific value). The curing rate C defined by the following formula (1) is 98% or more when Q1 (J / g) is the calorific value of the viscoelastic resin composition after curing measured using Means.
C (%) = (Q0−Q1) / Q0 × 100 (1)

  In the present invention, the glass transition temperature Tg is a value measured using TMA (Thermo Mechanical Analysis) (for example, “Thermoplus TG8120 type” manufactured by Rigaku Corporation). “TMA” is a method of measuring the deformation of a substance as a function of temperature by applying a non-vibrating load while changing the temperature of the substance according to a controlled program. Since the slope corresponds to the thermal expansion coefficient, Tg can be obtained from the change in the slope.

  According to the viscoelastic resin composition of the present invention, heat resistance, adhesion, bending workability, and dimensional stability are achieved by including the above acrylic rubber polymer and having a Tg after curing within the above temperature range. It is possible to easily produce a wiring board material that sufficiently satisfies all of the properties.

  When the content of glycidyl methacrylate in the acrylic rubber polymer is outside the above range, for example, a wiring board material obtained by impregnating a fiber substrate with the viscoelastic resin composition of the present invention, or the viscoelastic resin of the present invention. In a wiring board material obtained by molding the composition into a film, etc., it tends to be difficult to satisfy all of heat resistance, adhesion and bending workability. If the weight average molecular weight (Mw) of the acrylic rubber polymer is less than 300,000, the viscosity of the viscoelastic resin composition tends to be too low to be suitable for use as a wiring board material. For example, when a fiber base material is impregnated with a viscoelastic resin composition, an appearance defect such as a streak is likely to occur because the resin flow tends to occur. When such a streak occurs, in a wiring board manufactured by a method such as pressing or laminating, there is a possibility that reliability may be lowered due to non-uniform resin flowability. On the other hand, if the weight average molecular weight exceeds 1,000,000, the viscosity of the viscoelastic resin composition becomes too high and tends to be unsuitable for use as a wiring board material. For example, when a fiber base material is impregnated with a viscoelastic resin composition, voids are likely to remain in the fiber base material due to a decrease in the impregnation property of the fiber base material, and the adhesion to the metal foil may be reduced. is there.

  By the way, the conventional wiring board material obtained by impregnating a glass cloth with an epoxy resin is likely to generate a large amount of dust when it is cut or trimmed, which may hinder work in a clean environment. It was. On the other hand, according to the viscoelastic resin composition of the present invention, it is possible to form a wiring board material that generates a sufficiently small amount of dust even when it is subjected to cutting or external cutting. In addition, such an effect is that the viscoelastic resin composition of the present invention is a mixed composition of the specific acrylic rubber polymer and other curable components, and Tg after curing is in the above two temperature ranges. The present inventors infer that it is possible to achieve both workability and dustproofness by being a product.

  In the viscoelastic resin composition of the present invention, the acrylic rubber polymer is preferably polymerized in ion-exchanged water and washed with ion-exchanged water.

  Conventional resin compositions containing epoxy resins tend to have a significant decrease in resin flow when stored at room temperature to ensure sufficient adhesion required for wiring board materials. Had storage problems such as. On the other hand, the viscoelastic resin composition described above is polymerized in ion-exchanged water and contains an acrylic rubber polymer that has been washed with ion-exchanged water, thereby improving storage stability at room temperature. When stored at room temperature, the fluctuation of the resin flow amount is sufficiently small. Therefore, B-stage prepreg, copper foil with resin, adhesive film, etc. obtained using this viscoelastic resin composition are more effective for the problem that the flow rate of the resin decreases and the moldability deteriorates. It is possible to avoid it. The reason why such an effect can be obtained is that the reaction between glycidyl acrylate and ionic impurities in the acrylic rubber polymer, particularly positive ions, is reduced by reducing the ionic impurities in the acrylic rubber polymer. This is considered to be because it is possible to more effectively prevent the resin flow amount from being lowered by the above.

  Furthermore, in the viscoelastic resin composition of this invention, it is preferable that the ionic impurity in the said acrylic rubber polymer is 3 ppm or less. In this case, the resin flow maintainability at room temperature can be increased to a higher level. The content of ionic impurities is measured by atomic absorption analysis and / or inductively coupled plasma emission spectrometry.

  Moreover, in the viscoelastic resin composition of this invention, it is preferable that curable components other than the said acrylic rubber polymer are epoxy resins.

  Furthermore, the viscoelastic resin composition of the present invention preferably contains 60 to 120 parts by mass of the curable component with respect to 100 parts by mass of the acrylic rubber polymer. When the said curable component exceeds 120 mass parts with respect to 100 mass parts of acrylic rubber polymers, the storage elastic modulus of the hardened | cured material of a viscoelastic resin composition will become high too much, and it exists in the tendency for bending workability to fall. When the curable component is less than 60 parts by mass with respect to 100 parts by mass of the acrylic rubber polymer, the storage elastic modulus becomes excessively low, and sufficient curing strength cannot be obtained, resulting in a decrease in adhesion to copper foil or dimensional stability. There is a tendency for a decrease, and further a decrease in heat resistance.

  In the viscoelastic resin composition of this invention, it is preferable that the epoxy value of the said acrylic rubber polymer is 2-18. In this case, the viscoelastic resin composition has higher heat resistance and dimensional stability.

  The viscoelastic resin composition of the present invention preferably has a storage elastic modulus at 20 ° C. of 300 to 1700 MPa from the viewpoint of obtaining better bending workability.

  The present invention provides a prepreg obtained by impregnating a fiber base material with the above viscoelastic resin composition. Since the prepreg of the present invention comprises the viscoelastic resin composition of the present invention, it is possible to sufficiently satisfy all of heat resistance, adhesion, bending workability and dimensional stability. In addition, since the prepreg of the present invention contains the viscoelastic resin composition of the present invention, the generation of dust is sufficiently small even when cutting or external cutting is performed.

  In the prepreg of the present invention, from the viewpoint of handleability and processability, the fiber base material is preferably a glass cloth, and the thickness of the glass cloth is preferably 10 to 80 μm.

  Moreover, it is preferable that the prepreg of this invention contains the said viscoelastic resin composition 40-85 mass% from the point which makes adhesiveness with metal foil and dimensional stability more favorable.

  The present invention provides a substrate obtained by heating and pressurizing the prepreg. Since the substrate of the present invention is formed from the prepreg of the present invention, it is possible to sufficiently satisfy all of heat resistance, adhesion, bending workability, and dimensional stability. In addition, since the substrate of the present invention is formed from the prepreg of the present invention, the generation of dust is sufficiently small even when cutting or external cutting is performed.

  Moreover, this invention provides the conductor clad laminated board provided with the said board | substrate and the conductor layer provided on the at least one surface of this board | substrate. Since the conductor-clad laminate of the present invention is formed from the substrate of the present invention, it is excellent in heat resistance, adhesion, bending workability, and dimensional stability. In addition, since the conductor-clad laminate of the present invention is formed from the substrate of the present invention, the generation of dust is sufficiently small even when cutting or external cutting is performed.

  In the conductor-clad laminate of the present invention, the thickness of the substrate is preferably 20 to 100 μm from the viewpoint of bending workability and handleability.

  In the conductor-clad laminate of the present invention, the conductor layer is preferably a copper foil having a thickness of 3 to 35 μm from the viewpoint of bending workability.

  The conductor-clad laminate of the present invention preferably has a thickness of 200 μm or less from the viewpoint of bending workability.

  This invention provides the metal foil with resin provided with the resin layer which consists of the said viscoelastic resin composition, and the metal foil provided on the at least one surface of this resin layer. Since the metal foil with resin of the present invention includes the resin layer made of the viscoelastic resin composition of the present invention, it forms a wiring board material that sufficiently satisfies all of heat resistance, adhesion, bending workability and dimensional stability. Is possible. In addition, since the metal foil with resin of the present invention is provided with a resin layer made of the viscoelastic resin composition of the present invention, it forms a wiring board material that generates a sufficiently small amount of dust even when subjected to cutting or external cutting. can do.

  The metal foil with resin of the present invention is preferably a copper foil having a thickness of 3 to 35 μm from the viewpoint of bending workability.

  Moreover, as for the metal foil with resin of this invention, it is preferable that the thickness of the said resin layer is 5-90 micrometers from the point of bending workability.

  This invention provides a resin film provided with the resin layer which consists of the said viscoelastic resin composition, and the support film provided on the at least one surface of this resin layer. Since the resin film of the present invention includes the resin layer made of the viscoelastic resin composition of the present invention, a wiring board material that sufficiently satisfies all of heat resistance, adhesion, bending workability, and dimensional stability is formed. Is possible. In addition, since the resin film of the present invention is provided with the resin layer made of the viscoelastic resin composition of the present invention, a wiring board material that generates a sufficiently small amount of dust even when subjected to cutting or external cutting is formed. Can do.

  In the resin film of the present invention, the support film is preferably a polyethylene terephthalate film having a thickness of 5 to 200 μm.

  Moreover, it is preferable that the thickness of the said resin layer is 5-90 micrometers from the point of bending workability of the resin film of this invention.

  According to the present invention, a viscoelastic resin composition capable of easily producing a wiring board material that sufficiently satisfies all of heat resistance, adhesion, bending workability, and dimensional stability, and the viscoelastic resin composition are used. The obtained prepreg, conductor-clad laminate, resin-coated metal foil and resin film can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. Note that. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, it is not restricted to the dimension ratio of drawing.

  FIG. 1 is a perspective view showing an embodiment of a prepreg according to the present invention. A prepreg 100 shown in FIG. 1 is a sheet-like prepreg composed of a fiber base material and the viscoelastic resin composition of the present invention impregnated therein. This thickness is preferably 20 to 100 μm, and when the thickness of the prepreg is in this range, it has good bending workability.

  The fiber base material in the prepreg 100 is a flexible fiber base material that can be bent arbitrarily, and the thickness thereof is preferably 10 to 80 μm. Thereby, when combined with the viscoelastic resin composition of the present invention to be described later, the flexibility of the substrate obtained by heating and pressurizing this prepreg is increased synergistically, and it is extremely easy to bend arbitrarily. . Moreover, in order to further improve the bending workability of the prepreg, the thickness is more preferably 20 to 100 μm. Here, by using the fiber base material, the dimensional change accompanying heating, moisture absorption, etc. in the prepreg manufacturing process is further reduced.

  The form of the fiber base material can be appropriately selected from those generally used when producing metal foil-clad laminates and multilayer printed wiring boards, but usually fiber base materials such as woven fabrics and nonwoven fabrics are used. . As fibers constituting the fiber substrate, inorganic fibers such as glass, alumina, asbestos, boron, silica alumina glass, silica glass, tyrano, silicon carbide, silicon nitride, zirconia, aramid, polyether ketone, polyether imide, Examples thereof include organic fibers such as polyethersulfone, carbon and cellulose, and mixed papers thereof. Among these, glass fiber is preferable. In particular, a glass cloth (also referred to as “glass cloth”) that is a woven cloth of glass fibers is preferable as the fiber base material. Moreover, the glass cloth used for this invention can select various coupling processes, such as aminosilane and an epoxy silane, as surface treatment as needed.

  The viscoelastic resin composition of the present invention in the prepreg 100 contains 1 to 15% by mass of glycidyl methacrylate as a monomer unit, has a weight average molecular weight (Mw) of 300,000 to 1,000,000 and a glass transition temperature of −20. An acrylic rubber polymer in the range of 0 ° C to 0 ° C and a curable component other than the acrylic rubber polymer are contained, and the glass transition temperatures after curing are in the range of 20 ° C to 60 ° C and 120 ° C to 160 ° C. There is something.

In the present invention, “after curing” means Q0 (J / g), DSC (Differential Scanning Calorimeter) as the calorific value of the viscoelastic resin composition before curing measured using DSC (Differential Scanning Calorimeter). When the calorific value of the viscoelastic resin composition after curing measured by using Q1 (J / g), the curing rate C defined by the following formula (1) is 98% or more. To do.
C (%) = (Q0−Q1) / Q0 × 100 (1)

  In the present invention, the glass transition temperature Tg is a value measured using TMA (Thermo Mechanical Analysis) (for example, “Thermoplus TG8120 type” manufactured by Rigaku Corporation). “TMA” is a method of measuring the deformation of a substance as a function of temperature by applying a non-vibrating load while changing the temperature of the substance according to a controlled program. Since the slope corresponds to the thermal expansion coefficient, Tg can be obtained from the change in the slope.

  In the present specification, a value measured by the following method can be adopted as the glass transition temperature Tg. First, a viscoelastic resin composition is coated on a copper foil, and is cured by heating at 180 ° C. for 1 hour. Next, the copper foil is removed by etching, and the cured product of the obtained viscoelastic resin composition is cut into a 12.5 mm × 4 mm rectangle, which is used as a test piece for Tg measurement. Next, the test piece is set on a thermomechanical analyzer “TMA2940” (trade name, manufactured by TA Instruments). Cool the jacket with liquid nitrogen, raise the temperature from 25 ° C to 500 ° C (temperature increase rate: 10 ° C / min), then decrease the temperature from 500 ° C to 25 ° C (cooling rate: 40 ° C / min), load A TMA curve is obtained by measuring in the tensile mode at 40 g. The inflection point of the obtained TMA curve is obtained as Tg.

  Further, the glass transition temperature Tg of the acrylic rubber polymer can be calculated from the mixing ratio of each monomer constituting the polymer.

  The acrylic rubber polymer is preferably a rubber mainly composed of a polymer having (meth) acrylic acid alkyl ester as a monomer unit. In the present specification, the term “(meth) acrylate” means methacrylate or acrylate, and the term “(meth) acryl” means methacryl or acryl.

  Specific examples of the (meth) acrylic acid alkyl ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, ethylene glycol methyl ether acrylate, Cyclohexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, isobornyl acrylate, acrylate amide, isodecyl acrylate, octadecyl acrylate, lauryl acrylate, allyl acrylate, N-vinylpyrrolidone acrylate, methacryl Methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, isobutyl methacrylate, methacrylate Lenglycol methyl ether, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, isobornyl methacrylate, methacrylamide, isodecyl methacrylate, octadecyl methacrylate, lauryl methacrylate, allyl methacrylate, N methacrylate -Vinylpyrrolidone and dimethylaminoethyl methacrylate are mentioned. These are used singly or in combination of two or more.

  The acrylic rubber polymer used in the present invention is obtained by copolymerizing glycidyl (meth) acrylate in which the alkyl group of (meth) acrylic acid alkyl ester is substituted with a glycidyl group with another monomer copolymerizable therewith. It is done.

  Furthermore, the acrylic rubber polymer is preferably polymerized in ion exchange water and washed with ion exchange water. By using ion-exchanged water as the water for polymerization reaction when producing acrylic rubber polymer and water used for washing water for the purpose of removing impurities from the polymer, the ionic impurities in the polymer are greatly reduced. Can do. By impregnating the fiber base material with the viscoelastic resin composition containing the acrylic rubber polymer thus obtained, the room temperature storage stability of the prepreg is improved, and the fluctuation of the resin flow amount when stored at room temperature is sufficient. Can be small. Thereby, for example, when the prepreg in the B stage state is stored at room temperature, it is possible to more effectively avoid the problem that the flow amount of the resin is reduced and the moldability is deteriorated. Moreover, also when producing metal foil with resin and a resin film, the storage stability at normal temperature can be significantly improved by using the above viscoelastic resin composition.

  From the viewpoint of obtaining the above effect more reliably, the ion-exchanged water preferably has an electrical conductivity at 25 ° C. of 5 μS / cm or less, and more preferably 2 μS / cm or less.

  From the viewpoint of increasing the resin flow maintainability at room temperature to a higher level, the ionic impurities in the acrylic rubber polymer are preferably 3 ppm or less, and more preferably 1 ppm or less. An acrylic rubber polymer having an ionic impurity of 1 ppm or less can be obtained, for example, by increasing the number of washings with ion-exchanged water. The ionic impurities in the acrylic rubber polymer can be measured by atomic absorption analysis and / or inductively coupled plasma emission spectroscopy.

  The acrylic rubber polymer contains 1 to 15% by mass of glycidyl (meth) acrylate as a monomer unit based on the total amount. When the content of glycidyl (meth) acrylate is less than 1% by mass, the Tg of the cured product of the resulting viscoelastic resin composition tends to decrease and heat resistance tends to be insufficient. When the content of glycidyl (meth) acrylate exceeds 15% by mass, the storage elastic modulus of the cured product of the obtained viscoelastic resin composition is increased, and it becomes difficult to obtain sufficient adhesion and is difficult to bend. Tend to be.

  The acrylic rubber polymer has a weight average molecular weight (Mw) of 300,000 to 1,000,000. When the weight average molecular weight is less than 300,000, the viscosity of the viscoelastic resin composition decreases, and the resin flow tends to occur when the fiber base material is impregnated. Therefore, the dimensional stability tends to deteriorate. When the weight average molecular weight exceeds 1,000,000, the viscosity of the viscoelastic resin composition is high and the impregnation property to the fiber base material becomes insufficient, so that voids remain in the fiber base material and adhesion to the metal foil is increased. The dimensional stability tends to deteriorate.

Here, the above-described weight average molecular weight is determined by gel permeation chromatography (GPC) analysis under the following conditions and converted using a standard polystyrene calibration curve.
(GPC conditions)
Detector: HLC-8120GPC (manufactured by Tosoh Corporation)
Column: GMH _XL equivalent (3) (manufactured by Tosoh Corporation, trade name “TSKgel G5000H”)
Column size: 7.5mmφ × 300mm
Eluent: THF
Sample concentration: 5 mg / 1 mL
Injection volume: 50 μL
Pressure: 50 kgf / cm ²
Flow rate: 1.0 mL / min

  Moreover, the acrylic rubber polymer used in the present invention preferably has an epoxy value of 2 to 18, and more preferably has an epoxy value of 2 to 10. When the epoxy value is less than 2, the Tg of the obtained viscoelastic resin composition is reduced as compared with the case where the epoxy value is in the above range, and thus the heat resistance tends to be reduced. When the epoxy value exceeds 18, the storage elastic modulus of the cured product of the viscoelastic resin composition increases and the bending workability tends to decrease as compared with the case where the epoxy value is in the above range.

The epoxy value of the acrylic rubber polymer containing glycidyl acrylate as a monomer unit means a value determined by the following procedure.
1) Weigh accurately 2.5 g of sample (acrylic polymer) in a 100 ml Erlenmeyer flask with a stopper.
2) Add about 20 ml of methyl ethyl ketone (MEK) and stir and dissolve the sample for about 5 minutes.
3) Add 10 ml of N / 10HCl dioxane solution with a whole pipette, stopper and shake lightly to confirm that it is clear and uniform, and leave it for 10 minutes.
4) Add about 4 ml of ethanol, add 5 drops of phenolphthalein indicator, and titrate with 1/10 KOH ethanol solution. The end point is the time when it is colored light pink.
5) Separately, titrate a blank containing no sample in the same manner (blank test).
6) The epoxy value is calculated by the following formula.
Epoxy value (eq / 100 g) = (f × (BT)) / (W × c)
In the above formula, f represents the factor of 1/10 KOH ethanol solution, B represents the titration (ml) of the blank test, T represents the titration (ml) of the sample, and W represents the mass (g) of the sample. C represents the concentration (mass%) of the sample. The above N / 10HCl dioxane solution was prepared by taking 1 ml of concentrated hydrochloric acid with a measuring pipette and 100 ml of dioxane with a graduated cylinder into a 200 ml Erlenmeyer flask with a stopper, shaking well, and mixing well. Use the same thing.

  The viscoelastic resin composition according to the present invention preferably has a storage elastic modulus at 20 ° C. of the cured product of 300 to 1700 MPa. When the storage elastic modulus exceeds 1700 MPa, bending workability tends to decrease and cracks tend to occur. Moreover, when the storage elastic modulus is less than 300 MPa, the tackiness tends to increase and the workability tends to decrease.

  The “storage elastic modulus at 20 ° C. of the cured product” means a value obtained by the following procedure. First, a varnish containing a viscoelastic resin composition is applied to an electrolytic copper foil (made by Furukawa Electric Co., Ltd., trade name “F2-WS-12”) having a thickness of 12 μm so that the coating thickness is about 50 to 100 μm. And heated at 180 ° C. for 60 minutes. Next, the cured resin obtained by removing the copper foil by etching is cut out to about 30 mm × 5 mm, and this is used as a sample for measuring storage elastic modulus. About this measurement sample, a dynamic viscoelasticity curve is obtained by measuring using a dynamic viscoelasticity measuring device “Reogel-E-4000” (manufactured by UBM) under conditions of a measurement length of 20 mm and a measurement frequency of 10 Hz. And let the elastic modulus in 20 degreeC of the obtained dynamic viscoelastic curve be "the storage elastic modulus in 20 degreeC of hardened | cured material."

  The viscoelastic resin composition of the present invention is an elastic mixture in which a plurality of components are blended in order to obtain specific physical properties after curing, and may contain a resin component other than the acrylic rubber polymer. Examples of the resin component include epoxy resin, rubber-modified epoxy resin, SBR, NBR, CTBN, acrylic resin, polyamide, polyamideimide, and silicon-modified polyamideimide.

  Examples of the curable component other than the acrylic rubber polymer contained in the viscoelastic resin composition of the present invention include, for example, an epoxy resin, a polymer compound containing an epoxy group, a polyimide resin, an unsaturated polyester resin, and a polyurethane. Examples thereof include resins, bismaleimide resins, triazine-bismaleimide resins, and phenol resins.

  Among these, the curable component is preferably a thermosetting resin having a plurality of crosslinkable functional groups that are cross-linked by heating, in particular, a polyepoxy compound or an epoxy resin having a plurality of epoxy groups as the crosslinkable functional groups. It is more preferable. Specific examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolak type epoxy resin, Naphthalene skeleton-containing epoxy resin, aralkylene skeleton-containing epoxy resin, phenol biphenyl aralkyl-type epoxy resin, phenol salicylaldehyde novolak-type epoxy resin, phosphorus-containing epoxy resin, lower alkyl group-substituted phenol salicylaldehyde novolak-type epoxy resin, dicyclopentadiene skeleton-containing epoxy Examples include resins, polyfunctional glycidylamine type epoxy resins, and polyfunctional alicyclic epoxy resins.

  The above resin component or curable component can be blended singly or in combination of two or more as long as the Tg after curing of the viscoelastic resin composition satisfies the above-described conditions.

  When using an epoxy resin, the hardening | curing agent or hardening accelerator can also be used together. As the curing agent, it is preferable to use a compound having a plurality of phenolic hydroxyl groups in one molecule. Examples of such compounds include compounds having two or more hydroxyl groups in one phenyl group such as hydroquinone, compounds containing a plurality of phenol rings or cresol rings in one molecule such as phenol resin and cresol resin, and the like. . These can be used alone or in combination of two or more.

  As the curing accelerator, an amine compound or an imidazole compound is preferably used. Examples of the amine compound include dicyandiamide, diaminodiphenylethane, diaminodiphenylethane, and guanylurea. Examples of imidazole compounds include 2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate. And imidazole compounds such as benzimidazole. Although the content rate of a hardening accelerator can be suitably determined according to the quantity etc. of the epoxy group in a viscoelastic resin composition, generally 0. 0 is based on the solid content whole quantity in a viscoelastic resin composition. It is preferable to set it as 01-10 mass%.

  It is preferable that the viscoelastic resin composition of this invention contains 60-120 mass parts of sclerosing | hardenable components with respect to 100 mass parts of acrylic rubber polymers. When the curable component exceeds 120 parts by mass with respect to 100 parts by mass of the acrylic rubber polymer, the storage elastic modulus of the cured product of the viscoelastic resin composition becomes excessively high, and the flexibility tends to decrease. If the curable component is less than 60 parts by mass with respect to 100 parts by mass of the acrylic rubber polymer, the storage elastic modulus becomes excessively low, and sufficient curing strength cannot be obtained, resulting in a decrease in dimensional stability and a decrease in heat resistance. There is a tendency.

  In this embodiment, the composition, molecular weight, and glycidylmeta of the acrylic rubber polymer contained in the viscoelastic resin composition so that the glass transition temperature after curing is in the range of 20 ° C to 60 ° C and 120 ° C to 160 ° C. It is preferable to adjust the acrylate content or to select and mix other curable components as appropriate. The Tg of the acrylic rubber polymer can be adjusted, for example, by using glycidyl methacrylate, ethyl acrylate, butyl acrylate, and acrylonitrile as monomers for obtaining the acrylic rubber polymer, and appropriately changing the blending amounts thereof. . In addition, the molecular weight of the acrylic rubber polymer can be adjusted, for example, by appropriately changing the polymerization initiator concentration and the polymerization temperature.

  The prepreg 100 can be prepared by impregnating a fiber base material with a varnish in which the above viscoelastic resin composition is dissolved or dispersed in a solvent, and removing the solvent from the varnish by heating at 80 ° C to 180 ° C. . The heating time can be appropriately determined according to the gelation state. Moreover, in this prepreg 100, although the solvent used for the varnish may remain | survive, it is preferable that 80 mass% or more is removed among the solvents contained in the varnish.

  When the fiber base material is impregnated with the varnish in the prepreg 100, the content ratio of the viscoelastic resin composition in the varnish is the total amount of the viscoelastic resin composition and the fiber base material, that is, the mass of the prepreg 100. It is preferable that it is 40-85 mass%. If the content is less than 40% by mass, the resin content is small, so that the adhesive force during bonding with a metal foil or the like tends to decrease. When the content ratio exceeds 85% by mass, the resin tends to flow from the prepreg during adhesion to a metal foil or the like, and there is a tendency that problems such as the prepreg being unable to be set to a predetermined film thickness occur.

  In the prepreg 100, the curing rate of the viscoelastic resin composition is preferably in the range of 10 to 80%. When the curing rate is less than 10%, when integrated with the metal foil, the unevenness of the fiber base material is reflected on the surface of the integrated metal foil layer and the surface smoothness tends to be lowered, and the thickness is controlled. Tend to be difficult. When the curing rate exceeds 80%, the resin component for integration with the metal foil layer is insufficient, the adhesive strength with the metal foil is remarkably reduced, and breakage or cracking occurs during integration with the metal foil. Workability tends to be poor.

  Here, the curing rate of the viscoelastic resin composition is determined by the following method. First, the fiber base material is impregnated with the varnish of the viscoelastic resin composition. Subsequently, the viscoelastic resin composition impregnated in the fiber base material is cured. At this time, the infrared absorption spectrum of the viscoelastic resin composition before and after the curing treatment is measured. And the reduction | decrease of the peak derived from an epoxy group is tracked and the cure rate of the viscoelastic resin composition after a hardening process is calculated | required.

  FIG. 2 is a partial cross-sectional view showing an embodiment of a conductor-clad laminate according to the present invention. A conductor-clad laminate 200 shown in FIG. 2 includes a substrate 30 obtained by heating and pressing the prepreg 100 and a conductor layer 10 provided on both surfaces of the substrate 30.

  The conductor layer 10 is not particularly limited as long as it is a conductive film. For example, it may be formed of a metal, an organic material, or a composite of both depending on the purpose. The thickness of the conductor layer 10 is preferably 3 μm to 75 μm.

  In this embodiment, the conductor layer is preferably a metal foil. Such a metal foil-clad laminate can be obtained, for example, by stacking metal foils on both sides of the prepreg 100 and heating and pressurizing the metal foil to cure the viscoelastic resin composition in the prepreg 100. The heating at this time is performed at 130 ° C to 250 ° C, preferably 150 ° C to 210 ° C. The pressurization is performed at a pressure of 0.5 MPa to 20 MPa, preferably 1 MPa to 8 MPa.

  As the metal foil, for example, copper foil, aluminum foil, and nickel foil are generally used, but copper foil is preferable. The thickness is preferably 3 to 35 μm in order to increase the flexibility of the metal foil-clad laminate. Moreover, as the metal foil having a thickness of 9 μm or more, an electrolytic copper foil or a rolled copper foil can be selected.

  Examples of the method for superimposing the substrate and the metal foil include a press lamination method and a hot roll continuous lamination method, and are not particularly limited. In the present embodiment, it is preferable to use a hot press lamination method in vacuum from the viewpoint of efficiently forming a metal foil-clad laminate.

  On the other hand, continuous lamination of the prepreg and metal foil through the interval between the hot rolls, the hot roll continuous laminating method in which it is laterally transported to a continuous thermosetting furnace and wound up after curing, the curing of the viscoelastic resin composition during curing This is a preferable method in terms of countermeasures such as wrinkles and breakage due to shrinkage. Curing of the viscoelastic resin composition can be carried out by methods such as thermal curing, ultraviolet curing, and electron beam curing, but a continuous curing method by thermal curing as described above is preferred. In some cases, post-heating treatment for a predetermined time may be performed for quality stabilization after curing and winding.

  The thickness of the conductor-clad laminate 200 is preferably 200 μm or less, and more preferably 20 to 180 μm. If this thickness exceeds 200 μm, the flexibility is lowered, and cracks may easily occur during bending. In addition, a conductor-clad laminate having a thickness of less than 20 μm is extremely difficult to manufacture.

  Embodiments of the conductor-clad laminate of the present invention are not limited to the above-described ones. For example, a plurality of prepregs 100 may be used, and the substrate may be composed of a multilayer fiber reinforced resin layer, or only one side of the substrate. You may provide conductor layers, such as metal foil, in this.

  FIG. 3 is a partial cross-sectional view showing an embodiment of a printed wiring board according to the present invention, which is obtained by forming a wiring pattern on the above-described conductor-clad laminate 200. A printed wiring board 300 shown in FIG. 3 mainly includes the above-described substrate 30 and a wiring pattern 11 formed of patterned conductor layers provided on both surfaces of the substrate 30. A plurality of through holes 70 are formed through the substrate 30 in a direction substantially perpendicular to the main surface, and a metal plating layer 60 having a predetermined thickness is formed on the hole wall of the through hole 70. . The printed wiring board 300 is obtained by forming a wiring pattern on the conductor-clad laminate 200. The wiring pattern can be formed by a conventionally known method such as a subtractive method. The printed wiring board 300 is suitably used as a so-called flexible printed wiring board.

  Moreover, the metal foil with resin of this embodiment is provided with the resin film which consists of the above-mentioned viscoelastic resin composition, and the metal foil provided on the at least one surface of the said resin film. For example, a copper foil, an aluminum foil, or a nickel foil is generally used as the metal foil. However, in the metal foil with a resin of the present embodiment, a copper foil is preferable. The thickness is preferably 3 to 35 μm in order to enhance the flexibility of the metal foil with resin. Moreover, as the metal foil having a thickness of 9 μm or more, an electrolytic copper foil or a rolled copper foil can be selected. The thickness of the resin film is preferably 5 to 90 μm. When the thickness of the resin film is 5 to 90 μm, good flexibility can be maintained.

  Furthermore, the resin film of this embodiment is provided with the resin film which consists of the above-mentioned viscoelastic resin composition, and the support film provided on the at least one surface of the said resin film. The thickness of the resin film is preferably 5 to 90 μm. When the thickness of the resin film is 5 to 90 μm, good flexibility can be maintained. Further, the material of the support film is not particularly limited as long as it is used for ordinary resin films. For example, a polymer film having heat resistance and solvent resistance such as polyethylene terephthalate, polypropylene, polyethylene, and polyester is preferable. Used for. In the present embodiment, a polyethylene terephthalate film having a thickness of 5 to 200 μm is preferably used as the support film. In addition, such a polymer film may have a single layer structure or a laminated structure in which films having a plurality of compositions are laminated.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

  In this example, the glass transition temperature before curing, the glass transition temperature after curing, and the storage elastic modulus after curing of the viscoelastic resin composition were measured by the following methods.

[Glass transition temperature of acrylic polymer]
The glass transition temperature of the acrylic polymer was calculated from the mixing ratio of each monomer constituting the polymer.

[Glass transition temperature after curing]
First, a varnish containing a viscoelastic resin composition was applied to a copper foil so that the coating thickness was about 50 μm, and heated at 180 ° C. for 1 hour to be cured. Next, the copper foil was removed by etching, and the cured product of the obtained viscoelastic resin composition was cut into a 12.5 mm × 4 mm rectangle, which was used as a test piece for Tg measurement. Next, the test piece was set on a thermomechanical analyzer “TMA2940” (trade name, manufactured by TA Instruments). Cool the jacket with liquid nitrogen, raise the temperature from 25 ° C to 500 ° C (temperature increase rate: 10 ° C / min), then decrease the temperature from 500 ° C to 25 ° C (cooling rate: 40 ° C / min), load The TMA curve was obtained by measuring in 40 g and the tensile mode, and the inflection point of the obtained TMA curve was obtained as Tg.

[Storage modulus after curing]
First, a varnish containing a viscoelastic resin composition is applied to an electrolytic copper foil (made by Furukawa Electric Co., Ltd., trade name “F2-WS-12”) having a thickness of 12 μm so that the coating thickness is about 50 to 100 μm. And heated at 180 ° C. for 60 minutes. Next, the cured resin obtained by removing the copper foil by etching was cut out to about 30 mm × 5 mm, and this was used as a sample for measuring storage elastic modulus. About this measurement sample, using a dynamic viscoelasticity measuring device “Reogel-E-4000” (manufactured by UBM), a dynamic viscoelasticity curve is obtained by measurement under the conditions of a measurement length of 20 mm and a measurement frequency of 10 Hz. The elastic modulus at 20 ° C. of the obtained dynamic viscoelastic curve was taken as the storage elastic modulus after curing.

  The content of ionic impurities in the acrylic rubber polymer used in this example was determined by the following method. First, as a pretreatment, the acrylic rubber polymer was subjected to acid decomposition by the microwave method, allowed to cool, and then fixed with ultrapure water. On the other hand, depending on the impurity ions to be analyzed, impurity ions are analyzed by atomic absorption method (atomic absorption analyzer: Z5010 manufactured by Hitachi, Ltd.) and ICP-AES method (dielectric coupled plasma emission spectrometer: SPS3000 manufactured by Seiko Instruments Inc.). Was quantified.

(Example 1)
The viscoelastic resin composition was adjusted as follows so that the Tg after curing of the viscoelastic resin composition was 30 ° C and 150 ° C. That is, “HM10-M50S” which is a composition containing an acrylic rubber polymer (manufactured by Negami Kogyo Co., Ltd., trade name, weight average molecular weight: 500,000, glycidyl methacrylate (GMA) content: 10% by mass, ion-exchanged water) 100 parts by mass of Tg: -10 ° C. with ionic impurities content of 3 ppm or less by polymerization and ion-exchanged water washing, and “EP-828” (manufactured by Yuka Shell Co., Ltd.) , Trade name, epoxy resin) 60 parts by mass, tetrabromobisphenol A “FG2000” (trade name, manufactured by Teijin Chemicals Ltd.) which is a curing agent, and imidazole “2PZ-CN” which is a curing accelerator ( Shikoku Kasei Co., Ltd. product name) 0.3 parts by mass was mixed. Next, methyl isobutyl ketone (MIBK) was added as a solvent, and the varnish of the viscoelastic resin composition was adjusted so that the viscosity was 850 Pa · s.

(Comparative Example 1)
A varnish of a viscoelastic resin composition was prepared in the same manner as in Example 1 except that the glycidyl methacrylate content in the acrylic rubber polymer was 0% by mass.

(Comparative Example 2)
The varnish of the viscoelastic resin composition was adjusted in the same manner as in Example 1 except that the acrylonitrile content in the acrylic rubber polymer was 4% by mass so that the Tg of the acrylic rubber polymer was −22 ° C.

(Comparative Example 3)
The varnish of the viscoelastic resin composition was adjusted in the same manner as in Example 1 except that the acrylonitrile content in the acrylic rubber polymer was 42% by mass so that the Tg of the acrylic rubber polymer was 2 ° C.

(Comparative Example 4)
A varnish of a viscoelastic resin composition was prepared in the same manner as in Example 1 except that the weight average molecular weight of the acrylic rubber polymer was changed to 1.1 million.

(Comparative Example 5)
A varnish of a viscoelastic resin composition was prepared in the same manner as in Example 1 except that the weight average molecular weight of the acrylic rubber polymer was changed to 250,000.

(Comparative Example 6)
A varnish of a viscoelastic resin composition was prepared in the same manner as in Example 1 except that the glycidyl methacrylate content in the acrylic rubber polymer was 17% by mass.

<Preparation of prepreg and copper clad laminate>
The varnishes prepared in the above Examples and Comparative Examples were each impregnated with a vertical coating machine onto a glass cloth “# 1027” (Unitika Ltd., trade name) having a thickness of about 20 μm, and the drying furnace temperature was Was set to 150 ° C., and the solvent was removed by heating and drying at a line speed of 1.5 m / min to obtain a prepreg. In addition, the resin content and base material thickness of the obtained prepreg are shown in Table 1.

  A laminate in which a high-stretched electrolytic copper foil “F2S18” (product name, manufactured by Furukawa Circuit Foil Co., Ltd.) having a thickness of 18 μm is laminated on both surfaces of the prepreg obtained above so that its roughened surface is combined with the prepreg is 100 t. A double-sided copper-clad laminate was produced by heating and pressurizing using a vacuum press machine at 180 ° C. for 40 minutes under a vacuum press condition of 4 MPa.

<Characteristic evaluation of prepreg and double-sided copper-clad laminate>
[Copper foil peel strength]
About the obtained double-sided copper clad laminated board, the peeling test of the 90 degree direction was done, and the maximum load at that time was made into copper foil peel strength. The results are shown in Table 1.

[Evaluation of heat resistance]
The double-sided copper-clad laminate was cut into a 50 mm × 50 mm square and used as a sample for evaluation. The sample for evaluation was floated on molten solder at 288 ° C. The state of the sample for evaluation at that time was visually observed, and the time until an abnormality such as blistering or peeling was observed was measured. It means that heat resistance, such as solder heat resistance, is excellent, so that this time is long. The results are shown in Table 1. In the table, “5 minutes or more” means that no blistering or peeling was observed even after 5 minutes.

[Base material tack]
The probe tack test was performed. Specifically, after a 40 ° C. heating probe was pressed against a prepreg placed on a stage heated to 40 ° C., the maximum load when it was peeled off was determined and used as a tack. At this time, the probe diameter was 5 mm, the probe speed was 30 mm / min, the load for pressing the probe was 100 gf, and the probe contact time was 2 seconds. A similar test was performed on five test pieces, and the average value was obtained. As the measuring apparatus, a probe tack tester (Resca Co., Ltd. tack tester) according to JISZ0237-1991 was used. The tack was evaluated according to the following criteria. The results are shown in Table 1.
OK: The specimen does not change when the probe leaves.
NG: The test piece changes when the probe leaves.

[Evaluation of dimensional stability]
After etching the copper foils of the double-sided copper-clad laminates of the 250 mm square examples and comparative examples, drying was performed at 80 ° C. for 30 minutes to obtain test substrates. Subsequently, the distance between the two fixed points in the TD direction and the two fixed points in the MD direction of the test substrate was measured. Next, the test substrate was left in an 80 ° C., 90% RH atmosphere for 30 minutes, or in a 260 ° C., 90% RH atmosphere for 30 seconds. Then, the distance between the fixed points in the TD direction and the fixed point in the MD direction of the test substrate was measured, and a change in the distance was calculated as a dimensional change rate. A smaller dimensional change rate means higher dimensional stability. The results are shown in Table 1.

[Evaluation of bending workability]
A test piece having a size of 10 mm in width and 100 mm in length was cut out from a wiring board obtained by etching the copper foil of the copper-clad laminate. The test piece was placed on a table with a pin having a diameter (R) of 0.1 mm, 0.25 mm, or 0.50 mm, respectively. And the presence or absence of the generation | occurrence | production of the crack when a test piece was locally bent was observed by reciprocating a roller on the test piece of the part in which the pin is pinched. Evaluation was performed according to the following criteria. The smaller the occurrence of cracks (whitening), the higher the bending workability. The results are shown in Table 1.
○: No abnormality △: Whitening due to partial cracking ×: Whitening due to overall cracking

[Evaluation of room temperature storage stability]
The obtained prepreg was stored at room temperature (20 ± 2 ° C.) for 90 days. And the amount of resin flows in the prepreg before storage and after storage was measured by a mill flow measurement method. Using the obtained value, the resin flow retention was determined by the following formula. The larger the numerical value of the resin flow retention rate, the higher the room temperature storage stability. The results are shown in Table 1.
Resin flow retention rate (%)
= [Resin flow amount after storage] / [Resin flow amount before storage] × 100

[Evaluation of dust generation]
The obtained prepreg was dropped on a black paper from a position having a height of 50 cm. The number of dusts generated immediately after that was measured for 30 seconds using a particle counter “Model 227” (trade name, measurement method: semiconductor laser light source side method light scattering) manufactured by Transtec Corporation. In the measurement, particles of 5 μm or more were detected as dust. The results are shown in Table 1.

  As shown in Table 1, the copper-clad laminate produced using the viscoelastic resin composition of Example 1 was not observed in the heat resistance test at 288 ° C. for 5 minutes or more, and the heat resistance was not observed. It was excellent. Even in the pin gauge bending test, the laminate was free from cracks during bending, and could be bent arbitrarily and had sufficient bending workability. Further, in the evaluation of dimensional stability, the dimensional change rate was less than 0.03%, indicating good dimensional stability. Moreover, the prepreg produced using the viscoelastic resin composition of Example 1 showed sufficient resin flow retention in evaluation of normal temperature storage stability, and it turned out that it is excellent in normal temperature storage stability. Furthermore, the prepreg produced using the viscoelastic resin composition of Example 1 has a very small amount of dust generation compared to a general wiring board prepreg in the evaluation of dust generation, and is difficult to generate dust. It was confirmed.

  In contrast, in the copper-clad laminate produced using the viscoelastic resin composition of Comparative Example 1, no cracks were observed in the evaluation of bending workability. However, blistering was observed in 5 seconds in the solder heat resistance test, and the heat resistance was insufficient. The copper-clad laminate produced using the viscoelastic resin composition of Comparative Example 2 had insufficient heat resistance, and peeling was observed in 10 seconds or less when the solder heat resistance at 288 ° C. was used. Further, the prepreg had a large adhesiveness, and the workability was extremely poor. The copper clad laminate produced using the viscoelastic resin composition of Comparative Example 3 was cracked during bending in a pin gauge bending test, and the bending workability was insufficient. It has been found that the prepreg impregnated with the viscoelastic resin composition of Comparative Example 4 is not sufficiently impregnated with the resin and causes voids, and cannot be used as a wiring board material. Moreover, the copper clad laminated board produced using the viscoelastic resin composition of the comparative example 4 was inadequate in heat resistance and bending workability. Since the prepreg impregnated with the viscoelastic resin composition of Comparative Example 5 had a low viscosity of the varnish made of the viscoelastic resin composition, it was revealed that the appearance of the prepreg was poor and could not be used as a wiring board material. The copper-clad laminate produced using the viscoelastic resin composition of Comparative Example 6 had a low copper foil peel strength and an insufficient bending workability.

(Example 2)
Viscoelasticity was the same as in Example 1 except that the number of washings with ion-exchange water in the preparation of the acrylic rubber polymer “HM10-M50S” was increased and the content of ionic impurities was less than 1 ppm. A varnish of the resin composition was prepared.

(Reference Example 1)
An acrylic rubber polymer having the same composition as the acrylic rubber polymer “HM10-M50S”, polymerized in ordinary industrial water, and washed with ordinary industrial water (content of ionic impurities: 6 ppm) The varnish of the viscoelastic resin composition was prepared in the same manner as in Example 1 except that.

  Using the varnishes prepared in the above Examples and Reference Examples, prepregs and copper clad laminates were produced in the same manner as in the above Example 1 and Comparative Examples 1-6. About the obtained prepreg and double-sided copper clad laminated board, the characteristic evaluation was performed similarly to the above. The results are shown in Table 2 together with the results of Example 1.

As shown in Table 2, the copper clad laminate produced using the viscoelastic resin composition of Example 2 has a higher resin flow retention than that of Example 1 and Reference Example 1, and is extremely stable at room temperature storage. It turned out to be excellent.

1 is a perspective view showing an embodiment of a prepreg according to the present invention. It is a fragmentary sectional view showing one embodiment of a conductor clad laminated board concerning the present invention. It is a fragmentary sectional view showing one embodiment of a printed wiring board concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Conductor layer, 11 ... Wiring pattern, 30 ... Board | substrate, 60 ... Metal plating layer, 70 ... Through-hole, 100 ... Pre-preg, 200 ... Conductor-clad laminated board, 300 ... Printed wiring board.

Claims (20)

An acrylic rubber polymer containing 1 to 15% by mass of glycidyl methacrylate as a monomer unit, having a weight average molecular weight (Mw) of 300,000 to 1,000,000 and a glass transition temperature in the range of −20 ° C. to 0 ° C .; A curable component other than the acrylic rubber polymer,
A viscoelastic resin composition having a glass transition temperature after curing in the range of 20 ° C to 60 ° C and 120 ° C to 160 ° C.   The viscoelastic resin composition according to claim 1, wherein the acrylic rubber polymer is polymerized in ion-exchanged water and washed with ion-exchanged water.   The viscoelastic resin composition according to claim 1 or 2, wherein an ionic impurity in the acrylic rubber polymer is 3 ppm or less.   The viscoelastic resin composition according to any one of claims 1 to 3, wherein the curable component other than the acrylic rubber polymer is an epoxy resin.   The viscoelastic resin composition as described in any one of Claims 1-4 whose epoxy values of the said acrylic rubber polymer are 2-18.   The viscoelastic resin composition according to any one of claims 1 to 5, wherein a storage elastic modulus at 20 ° C is 300 to 1700 MPa.   A prepreg obtained by impregnating a fiber base material with the viscoelastic resin composition according to any one of claims 1 to 6.   The prepreg according to claim 7, wherein the fiber base material is a glass cloth, and the thickness of the glass cloth is 10 to 80 μm.   The prepreg according to claim 7 or 8, comprising 40 to 85% by mass of the viscoelastic resin composition.   The board | substrate obtained by heating and pressurizing the prepreg as described in any one of Claims 7-9.   A conductor-clad laminate comprising the substrate according to claim 10 and a conductor layer provided on at least one surface of the substrate.   The conductor-clad laminate according to claim 11, wherein the substrate has a thickness of 20 to 100 μm.   The conductor-clad laminate according to claim 11 or 12, wherein the conductor layer is a copper foil having a thickness of 3 to 35 µm.   The conductor-clad laminate according to any one of claims 11 to 13, wherein the thickness is 200 µm or less.   Metal foil with resin provided with the resin layer which consists of a viscoelastic resin composition as described in any one of Claims 1-6, and metal foil provided on the at least one surface of this resin layer.   The metal foil with a resin according to claim 15, wherein the metal foil is a copper foil having a thickness of 3 to 35 μm.   The metal foil with resin of Claim 15 or 16 whose thickness of the said resin layer is 5-90 micrometers.   A resin film provided with the resin layer which consists of a viscoelastic resin composition as described in any one of Claims 1-6, and the support film provided on the at least one surface of this resin layer.   The resin film according to claim 18, wherein the support film is a polyethylene terephthalate film having a thickness of 5 to 200 μm.   The resin film of Claim 18 or 19 whose thickness of the said resin layer is 5-90 micrometers.

Images