JP3982507B2 - Prepreg and metal-clad laminate - Google Patents

Description

  The present invention relates to an epoxy resin composition having excellent flame retardancy without containing a halogen such as bromine, a prepreg using the resin composition, and further, the prepreg is laminated with a metal foil and heated and pressurized to be cured. The present invention relates to a metal-clad laminate useful as a printed wiring material.

  Thermosetting resins typified by epoxy resins are widely used as printed wiring board materials and semiconductor sealing materials because of their excellent adhesion, electrical insulation, chemical resistance, and the like. As a material used for these applications, a compound having a halogen represented by bromine in the molecule has been generally blended for imparting flame retardancy. Incidentally, when a compound having halogen such as bromine in the molecule is blended, a cured product exhibiting excellent flame retardancy can be obtained.

  However, since the resin composition containing halogen as described above and its cured product may generate harmful substances such as hydrogen halide during combustion and may adversely affect the human body and the natural environment. Development of non-halogen epoxy resins and epoxy resin compositions that exhibit excellent flame retardancy without containing halogen has been underway.

  Typical flame retardants containing no halogen include phosphorus-containing compounds and metal hydroxides. Among these, as flame retardant non-halogen phosphorus-containing compounds, for example, phosphaphenanthrene compounds represented by the following general formula (IV) and derivatives thereof are known.

  Patent Document 1 discloses that a phosphorus-modified epoxy resin is obtained by reacting the phosphorus-containing compound with a compound having an epoxy group in the molecule, and this is used in combination with a melamine-modified phenolic curing agent. A technique for producing a flame retardant epoxy resin composition useful as such is disclosed. However, such reactive phosphorus compounds are more expensive than general brominated flame retardants and brominated epoxy resins, and thus have a problem in versatility.

  On the other hand, Patent Document 2 discloses a flame retardant epoxy resin composition containing a condensed phosphate ester-based additive-type phosphorus-containing compound, and this type of additive-type phosphorus-containing compound is a reactive phosphorus-containing compound. Therefore, if it is used as a flame retardant, a non-halogen flame retardant epoxy resin composition can be obtained relatively inexpensively. However, additive-type phosphorus-containing compounds are generally susceptible to hydrolysis due to the influence of moisture in the atmosphere, and when used as printed wiring board materials, they can cause a decrease in insulation properties or have a glass transition temperature. The decrease in mechanical strength may cause deterioration of mechanical strength and heat resistance.

Further, as the curing agent blended in the flame retardant epoxy resin composition as described above, a compound having a triazine skeleton that generates nitrogen gas by thermal decomposition is known. Flame-retardant non-halogen epoxy resin composition using a melamine-modified phenol resin obtained by reacting an amino group-containing triazine compound (typically melamine) with phenol and an aldehyde as a curing agent for epoxy resin Is disclosed. In Patent Document 2, it is difficult to use a compound obtained by subjecting 2 or 3 amino groups in a triazine compound having two or more amino groups to addition condensation reaction of phenol and formaldehyde, respectively, as a curing agent for an epoxy resin. A flammable epoxy resin composition is disclosed.
JP 2002-12655 A JP 2000-336248 A

  The non-halogen epoxy resin composition as described above is blended with a phosphorus-containing compound as a flame retardant, and combined with a nitrogen-containing phenolic resin that generates a large amount of nitrogen gas due to thermal decomposition as a curing agent. Exhibits excellent flame retardant effect. However, non-halogen epoxy resins such as those described above are still improved in terms of storage stability (pot life) as a resin for impregnation and electrical properties (insulation) and mechanical properties after moisture absorption as a cured product. There is room for it.

  The present invention has been made paying attention to the above-mentioned circumstances, and its purpose is not only to provide flame retardancy as a cured product, but also to storage stability as an impregnating resin, and further as a cured product. An object of the present invention is to provide a non-halogen flame retardant epoxy resin composition having even better performance in mechanical and electrical characteristics at an industrially low cost. Another object of the present invention is to provide a non-halogen flame-retardant prepreg as an intermediate product using the non-halogen flame-retardant resin composition, and further, a high-performance non-halogen using the prepreg. It is to provide a flame retardant metal-clad laminate.

  The non-halogen flame retardant epoxy resin composition according to the present invention that has been able to solve the above-described problems is an aromatic condensed phosphate ester represented by the following general formula (I) that does not contain a halogen element ( a), an epoxy resin (b) having two or more epoxy groups in one molecule, and a nitrogen-containing alkylphenol-based resin curing agent (c) represented by the following general formula (II) and / or (III) are essential. It is characterized by containing it as a component.

  In the resin composition of the present invention, the content ratio of the epoxy resin (b) and the nitrogen-containing alkylphenol-based resin curing agent (c) is the nitrogen-containing alkylphenol-based to the epoxy equivalent 1 of the epoxy resin (b). The hydroxyl group equivalent ratio of the resin curing agent (c) is preferably in the range of 0.4 to 1.2, and the compounding amount of the aromatic condensed phosphate (a) is the epoxy resin (b). It is preferable that it is the range of 10-40 mass parts with respect to 100 mass parts of sum total with the said nitrogen-containing alkylphenol-type resin hardening | curing agent (c).

  The non-halogen flame-retardant resin prepreg of the present invention is a non-halogen flame-retardant epoxy resin composition that satisfies the above requirements, such as inorganic fibers such as glass fibers, carbon fibers, and metal fibers, aramid fibers, polyester fibers, and polyamide fibers. It is impregnated into a base material made of organic fiber such as acrylic fiber, polytetrafluoroethylene fiber, etc., and is made into an intermediate material for curing molding by semi-curing, one or a plurality of this prepreg are stacked, If a metal foil such as copper, aluminum, silver, tin, nickel is disposed on at least one surface and heated and pressed, a non-halogen flame-retardant metal-clad laminate useful as a printed wiring material can be obtained. These prepregs and laminates are also included in the scope of the present invention.

  The non-halogen flame-retardant epoxy resin composition according to the present invention has excellent storage stability as an impregnating resin, and has excellent mechanical and electrical properties as a cured product, and is industrial. It can be manufactured relatively inexpensively and is extremely useful as a material for printed wiring boards.

The aromatic condensed phosphate ester (a) used as a flame retardant in the present invention is a phosphorus-containing compound represented by the general formula (I), wherein the alkyl groups represented by R ^{1 to} R ⁸ are: The same or different means a methyl group, an ethyl group, a propyl group, or a butyl group. Among these alkyl groups, the most versatile are a methyl group and an ethyl group. In particular, an aromatic condensed phosphate ester in which all of the alkyl groups are methyl groups is recommended as being easily available and excellent in flame retardancy. The aromatic condensed phosphoric acid ester having such a structure can be obtained as, for example, trade name “PX-200” manufactured by Daihachi Chemical Co., Ltd.

  Next, the epoxy resin (b) used in the present invention has at least 2 in the molecule in order to have crosslinking reactivity on the condition that the molecule does not contain a halogen element in accordance with the original purpose intended by the present invention. Any epoxy resin may be used as long as it has one epoxy group, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, alicyclic epoxy resin, Polyglycidyl ether compound of polyfunctional phenol, polyglycidyl ether compound of polyfunctional alcohol, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin which is glycidyl etherified product of polycondensate of phenols and formaldehyde Etc. It is. These epoxy resins can be used alone or in combination of two or more in any combination as necessary.

  Among these, bisphenol A type epoxy resin, novolac type epoxy resin, and a combination of these two types are most suitable in consideration of performance such as heat resistance, moisture resistance, and adhesiveness required as a laminate material.

  Further, the nitrogen-containing alkylphenol-based resin curing agent (c) used in the present invention acts as a curing agent for the above-described epoxy resin (b), so that the curing agent itself has an effect of improving flame retardancy. Nitrogen-containing alkylphenol compounds having a total of 5 or 6 nitrogen atoms including a triazine skeleton and 2 or 3 amino groups in the molecular structure are used. That is, by having a large number of nitrogen atoms in the molecule, a large amount of nitrogen gas is generated as a decomposition gas at the time of combustion, and together with the coexistence with the aromatic condensed phosphate ester (a) described above, A composition that exhibits excellent flame retardancy while being a system is provided.

  Moreover, when the nitrogen-containing alkylphenolic resin curing agent (c) represented by the general formulas (II) and (III) is combined with the aromatic condensed phosphate ester (a) represented by the general formula (I), The conventional halogen-based flame-retardant printed wiring board material has an action of suppressing its hydrolyzability even in a humid atmosphere, provides storage stability as a resin composition, and exhibits excellent electrical insulation. It has a high glass transition temperature at the same level as the above and gives an excellent heat-resistant cured product.

In the present invention, among the compounds represented by the general formulas (II) and (III), substituents represented by R ¹ , R ² and R ³ are specified as alkyl groups having 1 to 4 carbon atoms. This is extremely important in improving the storage stability (pot life) of the flame-retardant epoxy resin composition according to the present invention or the prepreg obtained by impregnating the resin composition and semi-curing it. Incidentally, any ^one of R ¹ , R ² , and R ³ that is a hydrogen atom is highly reactive, and a resin composition obtained by blending it with an epoxy resin (a) or the like is impregnated into a base material. The storage stability of the semi-cured prepreg is poor, leaving a problem in handling at the time of practical use. However, all of the substituents represented by R ¹ , R ² , and R ³ are alkyl groups, and the reactivity is low, and the prepreg prepared using the curing agent is very excellent in terms of storage stability. It will be.

  Commercially available products of such nitrogen-containing phenolic resin curing agent (c) include Dainippon Ink and Chemicals' trade name “LA-7052”, Gunei Chemical Industry's trade name “PS-6313”, Hitachi Chemical. An industrial product name “ML9010” or the like can be given. These nitrogen-containing phenolic resin curing agents can be used alone or in combination of two or more in any combination as necessary.

  The non-halogen epoxy resin composition according to the present invention contains the aromatic condensed phosphate ester (a), the epoxy resin (b) and the nitrogen-containing alkylphenol resin curing agent (c) as essential components. The blending amount of the aromatic condensed phosphoric acid ester (a) is in the range of 10 to 40 parts by mass with respect to 100 parts by mass of the total of the epoxy resin (b) and the curing agent (c). Is desirable. When the amount is less than 10 parts by mass, the flame retardancy tends to be insufficient, and when it exceeds 40 parts by mass, the heat resistance of the resin cured product and the electrical characteristics after moisture absorption are insufficient. A more preferable blending amount is 15 parts by mass or more and 35 parts by mass or less.

  Moreover, the compounding quantity of the said nitrogen-containing phenol-type resin hardening | curing agent (c) is 0.4 or more and 1.2 or less in the hydroxyl equivalent ratio of this resin hardening | curing agent (c) with respect to the epoxy equivalent 1 of an epoxy resin (a). It is desirable to be in the range. Outside this range, the reaction between the resin curing agent (c) and the epoxy resin (a) becomes sufficient, and the heat resistance and moisture resistance of the cured product may be insufficient, and the glass transition temperature is lowered. A more preferable blending amount is 0.5 or more and 1.0 or less in terms of the hydroxyl equivalent ratio of the resin curing agent (c) to the epoxy equivalent 1 of the epoxy resin (a).

  The epoxy resin composition of the present invention is required to contain the above three components, but if necessary, a curing accelerator that is usually used for promoting thermosetting of the epoxy resin may be further blended. Preferred curing accelerators include imidazole compounds such as 2-ethyl-4-methylimidazole. These curing accelerators can be used singly or in combination of a plurality of kinds, and the addition amount thereof is used in a small amount sufficient to promote the curing of the resin composition.

  It is also possible to add an inorganic filler to the epoxy resin composition of the present invention. Examples of inorganic fillers include known substances such as silica, alumina, talc, mica, aluminum hydroxide, magnesium hydroxide, clay, titanium oxide, silicon nitride, glass beads, and glass hollow spheres. There is no particular limitation as long as it does not deteriorate the properties of the epoxy resin composition and the prepreg using the same, and the laminated board, but it can be used alone or in combination of two or more, but from the viewpoint of flame retardancy, Metal hydroxides such as aluminum hydroxide and magnesium hydroxide are preferred.

  In addition, an appropriate amount of a heat stabilizer, an antioxidant, an antistatic agent, a plasticizer, a pigment, a dye, a colorant, or the like can be contained according to required characteristics.

  As a method of mixing the above raw material components, for example, a solvent mixing method in which each component is uniformly dissolved or dispersed in a solvent such as benzene, toluene, xylene, acetone, methyl ethyl ketone, or melt mixing while heating using a kneading extruder or the like. However, the method is not limited to these methods.

  The epoxy resin composition of the present invention thus obtained is halogen-free and has excellent flame retardancy, is excellent in heat resistance and moisture resistance properties, and is excellent in storage stability. It can be used effectively as a fixing material, electrical insulating material, fiber reinforced composite material, coating material, molding material, adhesive material, etc.

  Among them, the epoxy resin composition of the present invention is useful as a laminate for use in the electrical and electronic fields mainly composed of printed wiring boards, taking advantage of its excellent heat resistance and electrical characteristics, and its representative form is a prepreg. It is use as.

  That is, the prepreg of the present invention is obtained by impregnating a base material with the above epoxy resin composition and semi-curing the base material. As the base material, various glass cloths such as roving cloth and chopped mat, carbon fiber cloth, metal fiber cloth and the like. Woven knitted fabrics and nonwoven fabrics obtained from synthetic fibers such as inorganic fiber fabrics, aramid fibers, wholly aromatic polyester fibers, polyamide fibers, acrylic fibers and polytetrafluoroethylene fibers, as well as linen and natural cellulosic fabrics can be used. . Among these, glass fiber cloth and carbon fiber cloth are the most versatile.

  A method for producing a prepreg using these base materials is not particularly limited, but a general method is that the epoxy resin composition is dissolved or dispersed in a solvent, and this is immersed in a sheet made of the base material. (Dipping), impregnation by any method such as coating, drying at a relatively low temperature such that the epoxy resin is not completely cured to remove the solvent, and semi-curing to such an extent that the resin does not stick.

  Then, depending on the application, one or a plurality of the prepregs are superposed, and a metal foil such as copper, aluminum, silver, tin, nickel, etc. is superposed on one side, and then the epoxy resin is integrally heated and pressed. When cured, the flame retardant metal-clad laminate of the present invention is obtained. Since this metal-clad laminate can form an electric / electronic circuit by patterning one or both sides of the metal material, it can be effectively used as a substrate material for printed wiring.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1
As an epoxy resin component, 39 parts by mass of a bisphenol A type epoxy resin (epoxy equivalent 480), 39 parts by mass of a cresol novolac resin (epoxy equivalent 220), and 22 parts by mass of a triazine ring-containing cresol novolac resin as a resin curing agent ( Dainippon Ink Chemical Co., Ltd. trade name “LA-7052” , hydroxyl group equivalent 120), 0.05 part by weight of 2-ethyl-4-methylimidazole (trade name “2E4MZ” manufactured by Shikoku Kasei Kogyo Co., Ltd.) as a curing accelerator, 30 parts by mass of phosphate ester flame retardant (trade name “PX-200”, manufactured by Daihachi Chemical Co., Ltd.) is used as the aromatic condensed phosphate ester flame retardant, and methyl ethyl ketone as a solvent is added to these to obtain a solid content. The epoxy resin composition was adjusted so that it might become 65 mass%.

  This was applied to and impregnated into a glass fiber woven fabric, and heated and dried at 160 to 180 ° C. for 5 minutes to produce a prepreg. 8 sheets of the obtained prepregs are stacked, and a copper foil having a thickness of 18 μm is stacked on both sides of the laminate, followed by heating and pressing at 180 ° C. for 120 minutes, and a double-sided copper-clad laminate having a thickness of 1.6 mm Got.

Example 2
Both sides were prepared in the same manner as in Example 1 except that 50 parts by mass of aluminum hydroxide (trade name “CL-303” manufactured by Sumitomo Chemical Co., Ltd.) was additionally blended as an inorganic filler when the epoxy resin composition was produced. A copper clad laminate was obtained.

Comparative Examples 1-3, Reference Examples 1-4
A double-sided laminate was produced in the same manner as in Example 1 with the formulation shown in Table 1 below. The curing agent used in Comparative Example 1 was a triazine ring-containing phenol novolak resin (trade name “EXB-9824” manufactured by Dainippon Ink & Chemicals, hydroxyl equivalent: 120), and the curing agent used in Comparative Example 2 was dicyandiamide ( Nippon Carbide Corporation trade name “DICY”) and the curing agent used in Comparative Example 3 are bisphenol A type novolak resins (Dainippon Ink Chemicals trade name “VH-4240”, hydroxyl equivalent: 118).

  The physical properties of the double-sided copper-clad laminates obtained in Examples 1 and 2 and Comparative Examples 1 to 3 and Reference Examples 1 to 4 were evaluated by the following methods. The results are also shown in Table 1.

(Flame retardance)
After the entire surface of each test laminate was etched, the flame retardancy was evaluated according to the 20 mm vertical test method specified in UL94-1993.

(Stripping strength)
The peel strength between the outermost layer copper foil and the insulating layer (epoxy resin layer) in each test laminate was measured according to JIS-C6481.

(Glass-transition temperature)
The glass transition temperature (Tg) was measured according to JIS-C6481 about what etched the whole surface of the inner layer material of each test laminated board.

(Dielectric constant)
The dielectric constant of each test laminate was measured according to JIS-C6481.

(Volume resistivity)
The volume resistivity of each test laminate was measured according to JIS-C6481.

(Insulation resistance between circuits)
One prepreg obtained in the above-mentioned Examples, Comparative Examples and Reference Examples was prepared, and 18 μm thick copper foils were superposed on both sides, and then heated and pressed at 180 ° C. for 120 minutes, and the thickness was 0.2 mm. A double-sided copper-clad laminate is obtained. Then, a skewer circuit as shown in FIG. 1 is formed on one surface of the laminate. Further, one prepreg is laminated on the side where the circuit is formed, and a copper foil having a thickness of 18 μm is overlaid thereon, followed by heat-press molding at 180 ° C. for 120 minutes to obtain a three-layer laminate.

  Then, the copper foils on the front and back surfaces are removed by etching (FIG. 2 is a schematic enlarged cross-sectional view), and the resin portion is removed from the surface to expose the terminal portion (left and right square portions in FIG. 1). Then, while a direct current of 50 V was continuously applied between both terminals, the substrate was treated at 125 ° C. and a humidity of 85% for 100 hours, and then the insulation resistance between circuits after the treatment was measured.

(Curing time change rate)
About each prepreg obtained above, the curing time of the prepreg after processing for 100 hours at the initial stage and 40 degreeC and 50% of humidity was measured based on JIS-C-6521, and the change rate of the curing time was calculated | required.

  As is apparent from Table 1, the examples are non-halogen flame retardant copper clad laminates that do not contain halogen elements that satisfy the requirements of the present invention. Evaluations of −0 to V−1 are obtained. In addition, phosphoric acid ester flame retardant, which may be hydrolyzed, is used, but the insulation resistance between circuits after moisture absorption remains sufficiently high, and the performance that is practical in terms of glass transition temperature and peel strength. Is maintained. Moreover, it turns out that it has the outstanding storage stability compared with a comparative example.

  On the other hand, the performance of any of the comparative examples is insufficient and does not meet the object of the present invention.

It is an internal circuit figure of the insulation resistance value measurement sample between circuits used for performance evaluation. It is a schematic sectional drawing of the insulation resistance value measurement sample between circuits.

Claims (4)

None of which contains a halogen element, an aromatic condensed phosphate ester (a) represented by the following general formula (I), an epoxy resin (b) having two or more epoxy groups in one molecule, and the following general formula impregnated with formula (II) and / or (III) a nitrogen-containing alkylphenol resin curing agent represented by (c) a non-halogen flame retardant epoxy resin composition you as essential components to the substrate, it is semi-cured A non-halogen flame-retardant resin prepreg characterized by

The content ratio of the epoxy resin (b) and the nitrogen-containing alkylphenol resin curing agent (c) is a hydroxyl group equivalent ratio of the nitrogen-containing alkylphenol resin curing agent (c) to the epoxy equivalent 1 of the epoxy resin (b). non-halogen flame retardant resin prepreg according to claim 1 in a 0.4 to 1.2. The blending amount of the aromatic condensed phosphate (a) is 10 to 40 parts by mass with respect to 100 parts by mass of the total of the epoxy resin (b) and the nitrogen-containing alkylphenol resin curing agent (c). non-halogen flame retardant resin prepreg according to claim 1 or 2. The non-flammable prepreg according to any one of claims 1 to 3, wherein one or a plurality of the flame-retardant prepregs are overlapped, and a metal foil is disposed on at least one surface thereof and heated and pressed. Halogen flame retardant metal-clad laminate.

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