JPH0286441A - Continuous manufacture of laminated board - Google Patents

Abstract

PURPOSE:To remove residual bubbles from a laminated board by impregnating long sheetlike fibrous basic materials with specific heat-curable liquid resin and heating the materials in a laminated state under pressure using a double press consisting of an endless belt. CONSTITUTION:Each long sheetlike fibrous basic material is impregnated with heat-curable liquid resin so that at least, a space between the fibers of a basic material is substantially filled. The liquid resin actually does not require a drying process, neither generates any reaction byproduct such as gas or liquid in a curing reaction process. Next, a laminated board is manufactured by curing the material in a laminated state under a thermal pressure using a double belt press consisting of an endless belt. The curing process under a thermal pressure is performed after the impregnation resin is removed from each material impreg nated with resin so that a space generates between the fibers covered with the resin in a non-pressure state.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a method for continuously manufacturing a laminate, and also a metal foil-clad laminate having a metal foil adhered to the surface thereof, and particularly relates to a method for continuously manufacturing a laminate, and in particular a method for continuously manufacturing a laminate with a metal foil attached to the surface of the laminate. The present invention relates to an effective method for producing a laminate suitable for use in printed wiring boards.

"Conventional technology" A long base material such as kraft paper is sufficiently impregnated with a thermosetting resin liquid without leaving any voids, and multiple sheets of this impregnated base material are stacked one on top of the other and pressurized or heated without pressurization. Conventionally, laminates are manufactured continuously by curing a resin liquid.

However, among these methods, curing without pressure forms a thermosetting resin layer between the base materials, and the content of the base material in the resulting laminate is relatively low, resulting in poor strength and They tend to lack mechanical properties such as rigidity.

In order to solve this problem of insufficient base material content, there is a method in which multiple sheets of impregnated base materials that are sufficiently impregnated without leaving any voids are stacked together and cured under pressure using a double belt press, etc., as described above. , it is possible to increase the content of the base material and reduce resin impregnation, but most of the impregnated resin is discharged from the base material when pressurized, easily contaminating surrounding machinery, and the amount of discharge is enormous, so it is difficult to discharge. Regardless of whether it is necessary to recover the resin, there is the disadvantage that the work is very difficult.

``Problems to be Solved by the Invention'' Therefore, the present invention attempts to solve the problems encountered when manufacturing conventional laminates. When a laminate with a large base material content is obtained by impregnating a resin liquid and stacking a plurality of sheets of this impregnated base material and heating and pressurizing them using a double belt press consisting of an endless belt made of resin, the impregnated resin is The object of the present invention is to provide a method for manufacturing a laminate with almost no liquid discharge, practically no residual bubbles, and a high base material content.

[Means for Solving the Problems j] In the method for manufacturing a laminate of the present invention, each of the plurality of elongated sheet-like base materials made of fibers essentially does not require a drying process, and gas is injected during the curing reaction process. In the method for manufacturing a laminate, the laminate is impregnated with a thermosetting resin liquid that does not substantially generate reaction by-products such as liquid and liquid, and is subjected to pressure and heat curing in a laminated state using a double belt press constituted by an endless belt. The curable resin liquid is impregnated to at least the extent that the voids between the base fibers are substantially filled, and the pressure and heat curing is performed to the extent that voids are formed between the fibers covered by the impregnated resin liquid in a non-pressurized state. After removing the impregnated resin liquid from the resin liquid impregnated pot base material or each resin liquid impregnated base material,
A solution to the above problem is that the double belt press has a substantially uniform pressure over the entire pressure zone.

The manufacturing method of the present invention will be explained in detail below.

First, a plurality of long sheet-like base materials are impregnated with a resin liquid. Here, the long sheet-like base material is mainly made of glass fiber-based materials such as long glass fiber cloth and glass non-woven fabric, cellulose-based fibers such as kraft paper, aluminum hydroxide mixed paper, and linter paper. Inorganic materials such as paper and asbestos cloth w4w
, sheet-like or band-like products. When using paper as a sheet-like base material, from the viewpoint of impregnability and quality, the density (bulk density) when air-dried is 0.3 to 0.79/
Paper mainly composed of cellulose fibers such as ca., for example, kraft paper is preferred. When impregnating these sorted base materials with the resin liquid, methylolmelamine, medylolphenol, methylolguanamine, N
- It is preferable to subject the base material to an impregnation drying treatment using a treatment agent such as a methylol compound. That is, such treatment improves the water resistance of the sorted substrate and reduces its hygroscopicity, thereby improving the electrical properties of the resulting product. In this case, the amount of the treatment agent deposited on the substrate is usually about 5 to 35 parts by weight.

In addition, the thermosetting resin liquid referred to in the present invention that essentially does not require a drying process and does not substantially generate reaction by-products such as gas or liquid during the curing reaction process is a conventionally known unsaturated polyester resin. In addition to polyester resins, diallyl phthalate resins, vinyl ester resins, and epoxy acrylate resins, these resins include side chain double bond type resins described below, and these have unsaturated groups in their molecules. It is a resin that is characterized by being cross-linked between groups or via a cross-linking vinyl monomer, and also includes epoxy resins.

These thermosetting resins are suitable because they are in a liquid state with low viscosity when impregnated into a substrate, and have good bonding properties with the substrate when cured after being impregnated into the substrate. The side chain double bond type resin has particularly excellent impregnating properties when used in combination with a crosslinking vinyl monomer.

The above-mentioned side chain double bond type resin is a polymer composed of a main chain and a side chain, where the main chain is a backbone polymer containing vinyl monomer units having a functional group, and the side chains are It refers to a resin that is a branch having a radically reactive carbon-carbon double bond formed through a functional group. The vinyl monomer unit that constitutes the main chain of the side chain double bond type resin is a vinyl monomer unit that has a functional group as an essential unit, and includes vinyl monomer units that do not have a functional group as necessary. , these polymerize to form the main chain. Monomers constituting the above essential units include vinyl monomers having a carboxyl group as a functional group such as acrylic acid, methacrylic acid, maleic anhydride, and maleic acid monoester;
Vinyl monomers having a glycidyl group as a functional group such as glycidyl methacrylate and glycidyl acrylate, and other functional groups such as allyl alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and N-medylol acrylamide. Typical examples include vinyl monomers having a hydroxyl group, with acrylic acid and methacrylic acid being particularly preferred.

In addition, the vinyl monomer unit having a functional group as used herein refers to the case where it is not present as an active functional group when the main chain is formed by polymerization, or when the side chain described below is reacted with the functional group of the monomer in advance. It refers to a type of vinyl monomer unit that has a functional group that serves to form a side chain on the main chain, regardless of whether it is polymerized to form a main chain.

Examples of vinyl monomers without functional groups include styrene,
α-methylstyrene, chlorostyrene, vinyltoluene, vinyl chloride, vinylidene chloride, vinyl bromide, acrylonitrile, ethylene, propylene, butadiene, acrylate, methacrylate, vinyl acetate, vinyl propionate, diester maleate, ethyl vinyl Examples include benzene. The weight average molecular weight of the main chain composed of these vinyl monomer units is preferably from 5.000 to 400,000! 0,000 to 200.000. This value is appropriately selected depending on the type of side chain. This molecular weight affects the physical properties of printed circuit board laminates or electrically insulating laminates and the impregnability into the base material; if it is less than 5°000, the mechanical properties of the laminate after curing will be insufficient; If it exceeds 400,000, the resin impregnation into the sheet-like base material will be poor, which is not preferable. In addition, the amount of monomer units having functional groups in the main chain is related to the density of the side chains and affects the curing reactivity between the side chains, so an appropriate ratio is selected, but the side chain density in the main 111,000 g is Preferably 0.1 to 2 mol, more preferably 0
．． The amount is 4 to 1.5 moles.

The side chain referred to in this side chain double bond type resin is one that has a double bond >C=C at the end or in the middle, and has branches on the main chain via the functional group. or
It is applicable as long as it is possible to form crosslinks between side chains by a radical reaction using a crosslinking vinyl monomer.

Various methods can be employed to introduce a side chain having a double bond at the end of the side chain into the polymer constituting the main chain in this side chain double bond type resin. Some examples are as follows.

(a) One epoxy group of a compound having a jepoxy group, such as the diglycidyl ether type epoxy group of bisphenol, is reacted with the carboxyl group of the main chain functional group, and the remaining epoxy group is reacted with acrylic acid or methacrylic acid. Make it react.

(a) The carboxyl group of the main chain functional group and glycidyl acrylate or glycidyl methacrylate are subjected to an ester reaction.

(1) The epoxy group of the main chain functional group and acrylic acid, such as methacrylic acid, are subjected to an ester reaction.

(1) Hydroxyethyl (
(Meth) acrylate is reacted to prepare a reactant containing monoisonanate as a main component and containing almost no diisocyanate compound, and the isocyanate contained in this reactant is reacted with the hydroxyl group of the main chain polymer.

In the exemplified method, the main chain was copolymerized first, but it goes without saying that the reaction for forming the side chain was first carried out, and these monomers were finally monopolymerized or copolymerized to form an acryloyl group at the end of the side chain. Alternatively, a side chain double bond type resin containing a methacryloyl group may be produced.

In addition, crosslinking vinyl monomers include styrene, vinyltoluene, chlorostyrene, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate,
Included are butyl methacrylate, lauryl methacrylate, benzyl methacrylate, dibutyl maleate, dioctyl maleate, vinyl acetate, vinyl propionate, divinylbenzene, and the like. These monomers may be used in combination of two or more.

Furthermore, if necessary, a halogen-containing flame retardant imparting component and a flame retardant aid such as phosphoric acid ester, antimony trioxide, or aluminum hydroxide may be added to the thermosetting resin liquid used for impregnating the base material. It's okay.

When the thermosetting resin is used, a curing catalyst such as a polymerization initiator is added thereto.

The viscosity of this resin is preferably about 0.05 to 500 voids at 25°C.

In other words, if it exceeds 500 voids, impregnation into the base material becomes poor and bubbles tend to remain in the resulting laminate, while if it is 0.05 void, the impregnability is good but the double layer described below This is because when pressurizing with a belt press, the amount of resin discharged to obtain a bubble-free laminate becomes large, which is undesirable.

Next, methods for removing the excess resin liquid from the cartridge-like base material include a method of absorbing the resin liquid by reducing pressure, a method of blowing high-pressure air to scatter the resin liquid, and a method of removing the resin liquid by passing it between a pair of rolls. Various methods can be employed, such as a method in which the resin is removed under pressure. In particular, a method in which the resin is passed between rolls and removed under pressure is preferred because it allows continuous processing and allows adjustment of the amount of resin removed.

In this case, the resin liquid may be removed by removing excess resin from each of a plurality of sheet base materials impregnated with the resin liquid, and then laminating these materials, or after laminating a plurality of sheet base materials. , excess resin may be removed. Furthermore, the removal of the resin liquid is related to the pressure applied in the pressure and heat curing process using a double belt press, which will be described later. Adjustment is made so that exactly the same amount of resin or slightly less resin is removed. In other words, if the amount of resin removed here is too large, air bubbles will remain in the laminate obtained as a product after double pressing, reducing the moisture resistance of the laminate. This is because if the amount is too small, the amount of resin discharged during processing using a double belt press will increase, which will interfere with the processing.

Specifically, when removing excess resin liquid, the amount of resin remaining in the sheet-like base material is 110% or less of the amount of cured resin in the laminate that can be obtained as a product, and in particular, the discharged resin should not be recovered. In some cases, it is economical and desirable to carry out the process until it becomes 101% or less.

Thereafter, a plurality of sheet-like base materials impregnated with the above-mentioned resin liquid are laminated and subjected to pressure and heat curing treatment using a double belt press. The double belt press according to the present invention which maintains substantially uniform pressure over the entire pressure zone is constructed by installing stainless steel endless belts with a thickness of approximately Lmw above and below, and stacking them between the bottom endless belt and the bottom endless belt. The resin liquid-impregnated base material is sandwiched between the endless belts and can be pressurized and heated while being fed out, and has a structure in which the pressure of the pressure band between the endless belts becomes substantially equal.

To give a more detailed example of such a double belt press, ① A plurality of rows of roll pairs are arranged to sandwich the upper and lower belts and apply pressure to the belts, and the roll diameter is 50 m or less and the roll pitch and opening are - The ratio of the diameters of the holes is 1.
A system that reduces the pressure drop between rolls by keeping it below 2. In this case, the position of the roll may be of a fixed type, or of a type that is arranged between a pressure plate provided above and below the endless belt and the endless belt and revolves around the pressure plate.

■ A system in which the upper and lower belts are sandwiched, a pressure plate is placed to apply pressure to the belt, and a pressure medium is press-fitted and circulated between the pressure plate and the endless belt for the purpose of lubrication.

■ A container for storing pressure medium is provided between the upper and lower endless belts, and the opening of this container is configured to be in contact with the endless belt, so that the endless belt is directly suppressed by the pressure medium. For example, Tokukai Showa 6
2-212111 and the like.

Among these, the pressure medium storage type shown in (1) is particularly suitable because the pressure difference is small over the entire pressure zone. In other words, if there is a large pressure distribution in the pressure zone,
It becomes difficult to selectively discharge air bubbles from the base material impregnated with resin liquid.
Moreover, air is likely to be re-entrained in the pressurized band. Therefore, the variation in pressure in the pressure band is preferably ±50% or less, and preferably ±5 Kg/am” or less.

The pressure applied during processing in such a double belt press is appropriately selected in order to control the content of the base material in the laminate to be produced, and although it varies depending on the type of base material and resin liquid usually used, it is 1 kg/cm. ”100 from G
K g/cm”G, preferably 10 Kg/
cm'G to 50Kg/Cm''G. In this case,
When the pressure is lower than IKg/am''G, not only is it difficult to increase the base material content, but the effect of removing air bubbles is also small, and the laminate is likely to have air bubbles mixed in. On the other hand, when the pressure is 100 K
g/cm"G, it is not only unnecessary for removing air bubbles (but also the base material content in the resulting laminate becomes too large, which tends to cause deterioration in strength such as delamination). .

Further, the processing temperature in the double belt press described above varies depending on the type of resin liquid used, the type of curing catalyst, etc., but is usually in the range of 50°C to 200°C. That is, if the temperature is lower than 50°C, the time required for curing is too long and it is uneconomical, and if the temperature exceeds 200°C, the curing progresses rapidly, causing problems such as internal distortion and foaming.

According to such a double belt press, air bubbles mixed in the sheet-like base material from which the excess resin liquid has been removed can be selectively removed to the outside of the base material. That is,
After the excess resin liquid has been removed from the sheet-like base material, air is mixed in from the outside to generate bubbles. and,
In this way, from a base material impregnated with a resin liquid that has been contaminated with air and generated bubbles, it is not possible to obtain a substantially bubble-free laminate even if the base material is pressurized using a static press or a roll press and cured by heating. Alternatively, even if a laminate with relatively few bubbles was obtained, some resin liquid was discharged.

However, if the handle material impregnated with resin liquid containing air bubbles is continuously pressurized using the double belt press of the present invention, the air bubbles mixed into the base material will be released in the direction of movement of the base material in the pressure zone. It is pushed out in the opposite direction and eliminated.

Therefore, the laminate obtained after the double belt press treatment is substantially bubble-free. In addition, when pressurizing and heating with this double belt press, excess resin liquid is removed from the sheet-like base material in advance, so a large amount of resin liquid is prevented from being discharged. , can be omitted.

The laminate obtained by such pressure heat treatment usually has a base material content (% by weight of the base material in the laminate), although it varies depending on the type of base material and thermosetting resin used. is about 30 to 80% by weight, for example, when kraft paper and side chain double bond type resin are combined, 3
Approximately 5 to 60% by weight is preferred. That is, if the kraft paper content is less than 35% by weight, the mechanical strength, especially the bending strength and bending rigidity, of the resulting laminate will be low, while if it exceeds 60% by weight, it will not only easily cause delamination. This is because punchability and moisture resistance are undesirably lowered. Note that the base material content can be easily adjusted by changing the molding pressure of the double belt press.

In addition, the thickness of the laminate obtained in this way is as follows:
Although it varies depending on the type of base material etc. and the purpose of the laminate, it is usually 0.
．． It is approximately 5 to 3.0 mm.

When manufacturing metal foil-clad laminates, metal foil is usually introduced onto the outer surface of the sheet-like base material, which is the outermost layer of multiple sheet-like base materials from which excess resin liquid has been removed, and a double belt is formed. Pressure and heat treatment is performed using a press.

As the metal foil, electrolytic copper foil intended for use in printed circuit boards is preferred from the viewpoint of corrosion resistance, etching property, and adhesiveness, but electrolytic iron foil, aluminum foil, etc. may also be used. In addition, these metal foils usually have a thickness of lO~100
It is preferable that the adhesive surface be roughened to improve adhesiveness.

An adhesive is preferably used to bond the metal foil and the resin-impregnated base material. The adhesive is preferably a liquid or semi-fluid adhesive that does not generate unnecessary reaction by-products during the curing process, that is, an adhesive that preferably has a viscosity of 5000 voids or less.

From this point of view, for example, epoxy-acrylate adhesives, epoxy resin adhesives, polyisonanate adhesives, or various modified adhesives thereof are suitable. As the epoxy adhesive, a mixture of a bisphenol A type epoxy resin and a curing agent such as a polyamide resin or amines is suitable.

By introducing such an adhesive, it is possible to produce a metal foil-clad laminate that has excellent adhesive strength of metal foil, and also has excellent solder heat resistance and electrical insulation properties.

When the adhesive is used in a state where it is applied to metal foil, after application, it may be heat-treated at 60 to 150°C for 2 to 7 minutes to prevent preliminary curing to a semi-cured state. The thickness of the adhesive film is 10~
It may be about 100 μm, and 20 to 50111 is particularly suitable.

"Examples" The present invention will now be described in more detail with reference to Examples.

(Preparation of side chain double bond type resin) A separable flask (3000 m1) equipped with a stirrer, a thermometer with a gas introduction tube, a reflux condenser, and a dropping funnel.
2), methacrylic acid (35 g, 0.41 mol), methyl ethyl ketone (400 g), styrene monomer (800 g)
g, 7.7 mol), azobisisobutyronitrile (5,
0 g) Dodecyl mercaptan (12 g) was charged, and polymerization was carried out at 75 to 80° C. for 10 hours under a nitrogen atmosphere. Hydroquinone (0.5 g) was added to inhibit polymerization. The polymerization rate of styrene monomer was 76%, and the polymerization rate of methacrylic acid was 93%, and a polymer-containing liquid containing a styrene-methacrylic acid copolymer having a polymerization average molecular weight of about 50,000 was obtained.

In addition, another reactor with the same configuration as above was installed with "Epicoat 82".
7J (trade name of epoxy resin, manufactured by Yuka Shell Epoxy Co., Ltd.) (360 g, 1 mol), methacrylic acid (138 g, 1 mol)
．． 6 mol), benzyldimethylamine (1.2 g), and parabenzoquinone (0.12 g) were charged, and the mixture was reacted at 120° C. under a nitrogen atmosphere for 3 hours. After the reaction, the acid value became almost zero, and a vinylation reagent containing an epoxy resin containing an unsaturated group was obtained. Add the entire amount of the previously prepared polymer-containing liquid to the vinylation reagent, add triphenylphosphine (5 g) and rosebenzoquinone (0.1 Og) and heat to distill off the methyl ethyl ketone solvent at a boiling point of 110 ° C.
The reaction was carried out at the same temperature for 5 hours.

After the reaction, the unsaturated group-containing epoxy resin is about 1
It became 5%. Heat evaporation was continued at 11 g of 30-50 mm with intermittent addition of styrene monomer (1000 g). The operation was terminated when the amount of methyl ethyl ketone detected in the distillate became 0.1% or less. The thus obtained resin liquid containing the curable prepolymer has a non-volatile content of 52
It was a yellow-brown liquid with a viscosity of 6.12 voids (25°C), which was obtained by overlapping the flames.

(Examples and Comparative Examples) Commercially available long kraft paper (weighing 135 g/m', density 0
．． 49 g/cm') N-methylolmelamine (
Made by Nippon Carbide Co., Ltd.: NiResin S-305) on paper 10
It was applied in an amount of 20 parts by weight to 0 parts by weight, and dried and hardened to obtain a treated substrate.

Next, the treated base material is continuously impregnated with various thermosetting resin liquids containing a curing catalyst, and the eight sheets are introduced between pressure rolls in a stacked state, and a double belt press is used to apply pressure. The excess resin liquid was removed in accordance with the above.

Thereafter, continuous pressure and heat curing was performed using a double belt press to obtain a laminate and a single-sided copper foil-clad laminate. Here, the processing conditions include a heating temperature of 100°C and a processing time of 5.
After exiting the double belt press, the sheets were cut, stacked in a large number of sheets, and further post-treated at 120° C. for 1 hour. Further, the continuous pressing force was selected from the range of 3 to 50 Kg/cm'.

The mechanical strength of the laminate thus produced was examined by a bending test, and the amount of resin liquid discharged by double belt pressing was also examined, and the results are shown in Table 1. In addition, as a comparative example, after impregnating the base material in the resin liquid, we did not remove the excess (double belt press treatment).
Comparative Example I) and products obtained by changing the molding pressure to various values using the method of the present invention described above (Comparative Examples 2 to 4) were prepared, and their mechanical strength etc. were examined in the same manner as the products of the present invention described above.
The results are shown in Table 2.

From these results, the laminates obtained according to the present invention (Examples 1 to 7) have no residual air bubbles, have sufficient mechanical (bending) strength, and can be easily removed from the resin liquid using a white double belt press. It was confirmed that the amount of emissions was also small.

"Effects of the Invention" As explained above, according to the method for continuously manufacturing a laminate of the present invention, a plurality of fibrous sheet-like substrates each having a length of one length are impregnated with a thermosetting resin liquid, and the laminated board is laminated. In the method for producing a laminate in which the laminate is cured under pressure and heat using a double belt press constituted by an endless belt, impregnation with the facilitative resin liquid is performed at least to the extent that the voids between the base fibers are substantially filled; The impregnated resin liquid was removed from each resin liquid-impregnated base material or each resin liquid-impregnated base material to the extent that voids were formed between the fibers covered with the impregnated resin liquid in the non-pressurized state. Since the double belt press has a substantially uniform pressure over the entire pressure band, a laminate with almost no remaining air bubbles and a high base material content can be effectively produced. In addition, since the excess resin liquid is removed in advance when double belt pressing is performed, it is possible to prevent a large amount of resin liquid from being discharged. Difficult recovery of drained liquid can be omitted.

Furthermore, the obtained laminate is sufficiently pressurized by a double belt press and has a high base material content, so
It has excellent mechanical strength such as bending strength and elastic modulus.

Claims (4)

[Claims] (1) Thermosetting properties that essentially do not require a drying process for each long sheet-like base material made of fibers, and do not substantially generate reaction by-products such as gas or liquid during the curing reaction process. In a method for producing a laminate, the laminate is impregnated with a resin liquid and cured under pressure and heat using a double belt press constituted by an endless belt in a laminated state, wherein at least the voids between the base fibers are substantially The above-mentioned pressure and heat curing is performed until it is buried in the
This is done after the impregnated resin liquid is removed from each resin liquid impregnated base material or resin liquid impregnated laminate to the extent that voids are created between the fibers covered with the impregnated resin liquid in the non-pressurized state, and the double belt press is applied. A method for continuously manufacturing a laminate, characterized in that the pressure is substantially uniform over the entire pressure zone. (2) The laminate according to claim 1, wherein the double belt press constituted by the endless belt has a pressurizing chamber having the endless belt as one constituent surface, and uses fluid as a pressure and heat medium. Continuous manufacturing method. (3) Pressure of 1 to 100 kg by double belt press
3. The method for continuously manufacturing a laminate according to claim 1 or 2, wherein the laminate is in the range of /cm^2. (4) Cover at least one side of the laminate with metal foil after removing the impregnated resin liquid from the base material and before pressing with the double belt press, at the start of pressing with the double belt press, or after pressing with the double belt press. 3. The method for continuously manufacturing a laminate according to claim 1, wherein the laminates are stacked one on top of the other.