JPH0542989B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a thermosetting adhesive sheet used for bonding printed wiring boards to each other, or to bonding a printed wiring board to a base material, copper foil, or the like. [Prior Art] Conventionally, such thermosetting adhesive sheets have been produced by impregnating or coating a base material with a thermosetting resin composition mainly composed of epoxy resin, unsaturated polyester resin, etc. It is produced by molding it into a shape and heating it at an appropriate temperature and time to bring it into a semi-cured state. However, the above thermosetting adhesive sheet has the following drawbacks. First, in order to bring the resin composition into the desired semi-cured state homogeneously and with good reproducibility, it was necessary to strictly control manufacturing conditions such as heating temperature and time. Next, since the adhesive sheet is in a semi-cured state, the curing reaction of the unreacted resin proceeds gradually even at room temperature. Therefore, the storage stability of the adhesive sheet was extremely poor. In addition, as a method for obtaining an adhesive sheet with a uniform and stable semi-cured state without the need to strictly control manufacturing conditions such as heating temperature and heating time, JP-A-56-
No. 114691, a substrate is impregnated with a mixture of an ionizing radiation-curable resin composition that is cured by irradiation with ionizing radiation and a heat-curable resin composition that is not cured by ionizing radiation. Alternatively, an adhesive sheet has been proposed in which only the ionizing radiation-curable resin composition is cured by forming the adhesive sheet into a sheet or film and irradiating it with ionizing radiation. By changing the mixing ratio of the ionizing radiation-curable resin composition and the heat-curable resin composition, the adhesive sheet made of this mixed resin composition can be uniformly and stably produced with the desired semi-cured state. was able to manufacture it. However, this adhesive sheet had the following serious problems. First, since the solvent cannot be removed from the resin composition by irradiating it with ionizing radiation, the resin composition must be of a solvent-free type. However, a solvent-free, low-viscosity ionizing radiation-curable resin composition or heat-curable resin composition that can be sufficiently impregnated into a substrate such as glass cloth has not yet been developed. Further, in order to sufficiently impregnate a base material with these highly viscous resin compositions, special equipment such as vacuum impregnation or ultrasonic impregnation is required. In addition, these resin compositions can be
Even if the viscosity is lowered by adding an unreactive diluent, the cured product has drawbacks such as significant deterioration in properties such as heat resistance and moisture resistance. Further, the ionizing radiation applied to bring the material into a semi-cured state not only damages the base material but also causes serious harm to the human body of the worker. Furthermore, unlike a normal heating furnace, equipment for irradiating ionizing radiation is expensive and has drawbacks such as being very time-consuming for safety and maintenance. Next, the adhesive sheets used in the above-mentioned industrial application fields have not only good adhesive strength but also low resin flowability when heated and pressed to prevent the resin from extruding onto the circuit-forming metal surface or the edge of the base material. is required. Conventional adhesive sheets are made to have flexibility by adding a rubbery component to a thermosetting epoxy resin composition, thereby providing both low flowability and adhesive strength. However, the above adhesive sheet has the following drawbacks. That is, since a rubber-like component is added, there is a drawback that performance such as moisture resistance, heat resistance, chemical resistance, etc. is greatly reduced. The present invention has been made to solve the problems of conventional adhesive sheets as described above, and its purpose is to uniformly and stably obtain the semi-cured state of the adhesive sheet, and to maintain storage stability at room temperature. It also has good adhesion at low flowability.
Moreover, it is an object of the present invention to provide an adhesive sheet that has satisfactory heat resistance, moisture resistance, and chemical resistance. [Means for Solving the Problems] In order to achieve the above object, the inventor of the present invention has conducted extensive research and has discovered that the following adhesive sheet is significantly superior to conventional adhesive sheets. . That is, a thermosetting epoxy resin composition (A),
A thermosetting epoxy methacrylate resin composition (B) that does not cure or is difficult to cure when heated at the curing temperature of (A) above, but cures when heated at a temperature higher than that temperature is mixed with (B), and this mixture ( C) inorganic fiber,
Impregnated or coated on a base material made of at least one kind of organic fiber, or in sheet form,
This is possible by using an adhesive sheet in which only (A) in the mixture (C) is cured by forming it into a film and heating it at the curing temperature of (A). A detailed description of the invention follows. The thermosetting epoxy resin composition (A) used in the present invention contains an epoxy resin and at least one curing agent selected from amine curing agents, polyamide curing agents, and imidazole curing agents as essential components. That is. First, the epoxy resin used in the present invention includes, for example, glycidyl ethers of polyhydric phenols such as bisphenol A, bisphenol F, phenol novolak resin, and cresol novolak resin, polyhydric resins such as butanediol, and polypropylene glycol. Examples include glycidyl-type epoxy resins such as glycidyl ethers of alcohols, glycidyl esters of carboxylic acids such as phthalic acid and tetrahydrophthalic acid, and alicyclic-type epoxy resins obtained by epoxidizing intramolecular olefin bonds with peracetic acid, etc. It will be done. The epoxy curing agent used in the present invention is 50%
One is selected that sufficiently cures the epoxy resin in the temperature range of ~120°C. For example, aliphatic polyamines such as diethylenetriamine and diethylaminopropylamine, alicyclic polyamines such as menzendiamine and isophoronediamine, amine compounds such as aromatic amines such as metaphenylenediamine and diaminodiphenylmethane, and dimer acids. Polyamide compounds produced by condensation with polyamines, 2-methylimidazole, 2-ethyl-4-
Examples include fast-curing imidazole compounds such as methylimidazole. These curing agents are preferably those capable of curing the epoxy resin within the range of 50 to 120°C. This is because if the curing agent has high curing properties at temperatures lower than 50°C, the pot life will be very short, resulting in poor workability, and if the temperature is higher than 120°C, the curing reaction described in (B) will proceed gradually. be. It is desirable to use a hardening agent that can harden the epoxy resin within this temperature range, more preferably within the range of 70 to 100°C. These curing agents are appropriately selected depending on the type of epoxy resin mentioned above and usage conditions. In addition, a tertiary amine such as benzyldimethylamine, a compound having a phenolic hydroxyl group such as salicylic acid, etc. may be used as a curing accelerator, if necessary. Next, the thermosetting epoxy methacrylate resin composition (B) used in the present invention contains an epoxy methacrylate resin, a copolymerizable crosslinking agent, and a radical polymerization initiator as essential components. First, the epoxy methacrylate resin used in the present invention is a bisphenol type epoxy methacrylate resin which is an addition reaction product of a bisphenol A type or bisphenol F type epoxy resin and methacrylic acid, a phenol novolac epoxy resin, or Novolak-type epoxy methacrylate resin, which is the addition reaction product of cresol novolak epoxy resin and methacrylic acid, and aliphatic epoxy, which is the addition reaction product of glycidyl ether-type epoxy resin of polyhydric alcohols and methacrylic acid. The main component is at least one kind of methacrylate resin. Further, in the present invention, epoxy acrylate resin which is an addition reaction product of these epoxy resins and acrylic acid can also be used after being copolymerized with epoxy methacrylate resin, if necessary. Examples of copolymerizable crosslinking agents include acrylic acid esters such as diallyl phthalate, triethylene glycol diacrylate, and trimethylene propane triacrylate, unsaturated compounds that react with epoxy methacrylate resins such as trimethylolpropane trimethacrylate, and polypropylene. A monomer having two or more groups at each end or a prepolymer thereof can be used. It is preferable to use these copolymerizable crosslinking agents that have almost no volatility at temperatures below 120°C, because if they are volatile, the thermosetting epoxy resin composition (A) will be difficult to cure during curing. This is because the copolymerizable crosslinking agent is volatilized and reduced. The amount of the copolymerizable crosslinking agent is preferably 10 to 200 parts by weight, preferably 50 to 100 parts by weight, based on 100 parts by weight of the epoxy methacrylate resin. If it is less than 50 parts by weight, the viscosity of the epoxy methacrylate resin composition (B) will increase, resulting in poor workability.
Further, if the amount is more than 100 parts by weight, the performance of the cured product will deteriorate, which is not preferable. Next, the radical polymerization initiator is, for example, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-
Di-t-butylperoxyhexane, etc. 100-200℃
It is preferable to use one that decomposes and generates radicals when heated within this range. This is because if radicals are generated at a temperature lower than 100°C, the curing of (B) will proceed while curing of (A), and if it is higher than 200°C, workability during bonding will deteriorate when using an adhesive sheet. This is because the cost of equipment and fuel will be high. More preferably, the temperature range is 120°C to 170°C. Next, the mixing ratio of (A) to (B) is 1/
It is desirable that it be within the range of 9 to 9/1. 1/
If it is smaller than 9, the surface of the produced adhesive sheet will become extremely sticky. If it is larger than 9/1, the proportion of unreacted (B) contained in the adhesive sheet is too small, resulting in a decrease in adhesive strength. Desirably, 3/7 to 7/3 is preferable. In addition to (A) and (B), the composition of the present invention may optionally include a solvent having a boiling point of 120°C or lower, such as acetone or methyl ethyl ketone, a flame retardant,
thixotropy agents, fillers, reactive diluents,
A leveling agent, an antifoaming agent, etc. can be added. The present invention provides the above-mentioned mixed resin composition (C) with inorganic fibers,
Two ways of use are possible: one in which it is impregnated or coated on a base material made of at least one type of organic fiber, and the other in which it is formed into a sheet or film. Examples of the substrate impregnated or coated with the mixture (C) include woven fabrics and nonwoven fabrics made of inorganic fibers such as glass, silica, and asbestos, or organic fibers such as polyester, polyamide, polyamideimide, acrylic, and paper. , pine, or a combination of these materials is used. In addition, the sheet-like adhesive sheet is coated onto a film having releasability such as a fluororesin film using a curtain coater, a roll coater, a knife coater, etc. according to the coating thickness, and then the adhesive sheet described above (A ) by heating at the curing temperature. [Actions of the Invention] The present invention has the following effects by adopting the above-described measures. First, an epoxy resin is generally cured by an addition reaction with a functional group of a curing agent through a ring-opening reaction of an epoxy ring. The curing reaction of an epoxy resin using an amine curing agent, which is a typical curing agent, is shown below. Next, in general, thermosetting epoxy methacrylate resins are cured by radical polymerization of terminal unsaturated groups due to generation of radicals due to decomposition of peroxide. The curing reaction formula of epoxy methacrylate resin is shown below. R-O-O-R' → R-O・ + ・O-R'
...(2) ...(3) In the present invention, the reactivity of the epoxy group and the curing agent shown in formula (1) and the decomposability of the peroxide shown in formula (2) are set in different temperature ranges. Epoxy resin hardeners and peroxides are selected. That is, a thermosetting epoxy resin composition (A) containing an epoxy group and a curing agent that exhibits high reactivity within the range of 50 to 120°C, and a thermosetting epoxy resin composition (A) that exhibits high reactivity within the range of 100 to 200°C. and a thermosetting epoxy methacrylate resin composition (B) containing a peroxide that exhibits properties and generates radicals. When this mixture (C) is impregnated or applied onto a substrate, or formed into a sheet or film, and heated within the range of 50 to 120°C,
By curing only the above (A) in the mixture (C), the above (C) as a whole becomes a semi-cured state. Furthermore, by changing the mixing ratio of (A) and (B), any semi-cured state can be selected. Here, an addition reaction called a Michael reaction between an amine group of a curing agent and a vinyl group of an epoxy methacrylate resin or a copolymerizable crosslinking agent will be described. If (C) above is heated within the range of 50 to 120°C, if a large amount of this Michael reaction occurs, the epoxy methacrylate resin will also harden, so (C) above will not reach the desired semi-cured state. . However, this Michael reaction requires high temperatures to occur unless it is in the presence of a highly basic catalyst.
Even if the above-mentioned (C) in the present invention is heated within the range of 50 to 120°C, almost no Michael reaction occurs. Next, a detailed description will be given of the performance of the adhesive sheet of the present invention. As mentioned above, the adhesive sheet made by the above (C) can be arbitrarily set in a semi-cured state by changing the mixing ratio of the above (A) and the above (B).
Since (B) hardly reacts when heated within the range of 120°C, an adhesive sheet in a stable semi-cured state can always be obtained without strict control of curing conditions. Also, of course, even at room temperature, the above (B)
does not react, so the storage stability of the adhesive sheet is very good. Next, when you want to obtain strong adhesive strength without the resin flowing, if you create the desired semi-cured state by adjusting the mixing ratio of (A) and (B), the curing of (A) will Since the above-mentioned (C) as a whole has the three-dimensional network structure of the above-mentioned (A), it does not melt even when pressed at high temperature and high pressure, so almost no resin flows. However, the adhesive sheet contains unreacted (B), which is the reason why the adhesive strength is increased. The cured product obtained by heating the adhesive sheet of the present invention within the range of 100 to 200°C and also curing the above-mentioned (B) has the excellent heat resistance of the cured epoxy resin because it forms an interpenetrating polymer network structure. It is possible to obtain a cured product that combines the properties of hardness, moisture resistance, chemical resistance, and high adhesiveness with the excellent flexibility, high toughness, and impact resistance of cured epoxy methacrylate resin. [Examples] Next, the present invention will be specifically explained using Examples, but the present invention is not limited to the following Examples. In the following examples, all "parts" mean "parts by weight." Example 1 Bisphenol A type epoxy resin (average molecular weight
100 parts of 950 E-1001 (manufactured by Yuka Ciel Co., Ltd.) and 12.5 parts of Laromin C-260 (manufactured by BASF Corporation) as a curing agent were mixed to obtain composition (a). In addition, 100 parts of bisphenol A type epoxy methacrylate resin (Neopol 8104, manufactured by Nippon U-Pica Co., Ltd. with an average molecular weight of 1000),
75 parts of diallyl phthalate (manufactured by Osaka Soda Co., Ltd.) as a copolymerizable crosslinking agent and 1.8 parts of Percyl D(F) (manufactured by NOF Corporation) as a radical polymerization initiator were mixed to form composition (b). Make it a thing. Then, the composition (a) and the composition (b) were mixed at a ratio of 2:1, and methyl ethyl ketone was added so that the viscosity was 100 cPs to prepare a varnish for an impregnating agent. Next, a glass cloth having a thickness of 30 μm was impregnated with this impregnating varnish, and dried and cured at 80° C. for 40 minutes to obtain an adhesive sheet. Example 2 In Example 1, 100 parts of NK ester TMPT (manufactured by Shin Nakamura Kogyo Co., Ltd.) was used as a copolymerizable crosslinking agent, and Perbutyl D (manufactured by Nippon Oil & Fats Co., Ltd.) was used as a radical polymerization initiator.
The procedure was the same as in Example 1 except that 2 parts of (manufactured by) were used. Example 3 In Example 1, (a) composition and (b) composition were mixed at 1:1.
The procedure was the same as in Example 1 except that the mixture was mixed in step 1. Example 4 Bisphenol A type epoxy resin (average molecular weight
100 parts of 380 E-828 (manufactured by Yuka Ciel Co., Ltd.) and 40 parts of Kayahard AA (manufactured by Nippon Kayaku Co., Ltd.) as a curing agent were mixed to form a composition (a'). In addition, bisphenol A type methacrylate resin (average molecular weight
1000, Neopol 8104 manufactured by Nippon U-Pica Co., Ltd.) 100 copies,
75 parts of diallyl phthalate (manufactured by Osaka Soda Co., Ltd.) as a copolymerizable crosslinking agent and 1.8 parts of Percyl D(F) (manufactured by Nippon Oil & Fats Co., Ltd.) as a radical polymerization initiator were mixed to form composition (b'). Make it a thing. Then, the (a') composition and the (b') composition were mixed at a ratio of 2:1 to obtain a coating varnish. Next, this varnish was applied onto a Teflon film using a knife coater and cured at 100° C. for 90 minutes to obtain an adhesive sheet with a coating thickness of 50 μm. Example 5 In Example 4, 100 parts of NK ester TMPT (manufactured by Shin-Nakamura Kagaku Co., Ltd.) was used as a copolymerizable crosslinking agent, and Perbutyl D (manufactured by NOF Corporation) was used as a radical polymerization initiator.
The procedure was the same as in Example 4, except that 2 parts (manufactured by) were used. Example 6 Example 4 was the same as Example 4 except that the composition (a') and the composition (b') were mixed at a ratio of 1:1. Comparative Example A Commercially available prepreg adhesive sheet. Comparative Example B Commercially available adhesive sheet in sheet form. The adhesive sheets obtained in the above examples and the commercially available adhesive sheets of comparative examples were evaluated by the following method, and the results are shown in the table. (Rate of change over time): The calorific value before and after heat treatment at 100° C. for 2 hours was measured by DSC, and the change was determined from the formula shown below. Rate of change over time = (Calorific value before heat treatment - Calorific value after heat treatment) / Calorific value before heat treatment × 100 (Protrusion of resin): Cut a 2 cm diameter hole in the center of an adhesive sheet cut into 10 cm squares, and cut it at a temperature of 170°C. ,
After molding under press conditions of a pressure of 40 kgf/cm ² and a pressing time of 60 minutes, the maximum length of the resin protruding into the holes was measured. (Adhesive strength): (Normal state) An adhesive sheet is sandwiched between a 35 μm thick copper plate and a glass epoxy board, and the adhesive sheet is placed between 170℃ and 40℃.
After pressing at Kgf/cm ² for 60 minutes, the pieces were cut into 1 cm width and the peel strength was measured. (After heat treatment): Peel strength after 240 hours at 150℃. (After moisture absorption): Peel strength after 100 hours at PCT (121°C, 2 atm). As is clear from the table, the rate of change over time for each example was almost 0, which means that there is almost no hardness even before and after heat treatment.

[Table] This shows that the transformation is not progressing. This shows that the adhesive sheet of the present invention has extremely excellent storage stability at room temperature. Furthermore, it can be seen that if the ratios of (A) and (B) are the same, the amount of resin extrusion is approximately the same, and the amount of resin extrusion can be controlled arbitrarily depending on the ratio. On the other hand, good adhesive strength results were obtained even when the amount of resin protruding was small. Moreover, it was revealed that the decrease in adhesive strength after heat treatment or moisture absorption was smaller than that of the comparative example, and the heat resistance and moisture resistance were good. [Effects of the Invention] As is clear from the Examples, the adhesive sheet of the present invention had the following advantages. 1. Since the above (B) hardly reacts at the heating temperature used to form the semi-cured state, an adhesive sheet always having a uniform semi-cured state can be obtained. 2. Since (B) does not react even at room temperature, an adhesive sheet with extremely excellent storage stability can be obtained. 3. The resin flow can be determined by the mixing ratio of (A) and (B), and a stable flow can always be obtained. 4. Since unreacted (B) is present in the adhesive sheet, good adhesive strength can be obtained even when the resin flow is small. 5. Since it does not contain rubbery components, it has excellent heat resistance, moisture resistance, and chemical resistance. As described above, it is possible to obtain an adhesive sheet with extremely superior performance compared to conventional adhesive sheets, so it is industrially useful.

Claims (1)

[Scope of Claims] 1. A thermosetting epoxy resin composition (A), which does not cure or is difficult to cure when heated at the curing temperature of (A), and which cures when heated at a higher temperature. Curable epoxy methacrylate resin composition (B)
This mixture (C) is formed into a sheet or film, and heated at the curing temperature of (A) to cure only the (A) in the mixture (C). A thermosetting adhesive sheet characterized by: 2 The above (A) is an epoxy resin, an amine curing agent,
The thermosetting adhesive sheet according to claim 1, characterized in that it contains at least one type of curing agent selected from a polyamide curing agent and an imidazole curing agent as an essential component. 3. Thermosetting according to claim 1 or 2, characterized in that the curing agent contained in (A) is a curing agent capable of curing the epoxy resin within the range of 50 to 120°C. Adhesive sheet. 4 The above (B) is a bisphenol type epoxy methacrylate resin in which methacrylic acid is added to a bisphenol type epoxy resin, a novolak type epoxy methacrylate resin in which methacrylic acid is added to a novolak type epoxy resin, and a polyhydric alcohol. At least one selected from aliphatic epoxy methacrylate resins obtained by adding methacrylic acid to glycidyl ether type epoxy resins, a copolymerizable crosslinking agent, and a radical polymerization initiator as essential components. A thermosetting adhesive sheet according to any one of claims 1 to 3, characterized in that: 5 The radical polymerization initiator contained in (B) above is 100
The thermosetting adhesive sheet according to any one of claims 1 to 4, characterized in that it decomposes and generates radicals within a temperature range of -200°C. 6 The mixing ratio of (A) to (B) is 1/9 to
The thermosetting adhesive sheet according to any one of claims 1 to 5, wherein the thermosetting adhesive sheet is within the range of 9/1. 7 A thermosetting epoxy resin composition (A) and a thermosetting epoxy methacrylate resin that does not harden or hardens when heated at the curing temperature of (A), but hardens when heated at a higher temperature. Composition (B)
The mixture (C) is impregnated or applied onto a base material made of at least one of inorganic fibers and organic fibers, and heated at the curing temperature of (A). A thermosetting adhesive sheet characterized in that only (A) in C) is cured. 8 The above (A) is an epoxy resin and an amine curing agent,
8. The thermosetting adhesive sheet according to claim 7, which contains at least one type of curing agent selected from a polyamide curing agent and an imidazole curing agent as an essential component. 9. Thermosetting according to claim 7 or 8, characterized in that the curing agent contained in (A) is a curing agent capable of curing the epoxy resin within the range of 50 to 120°C. Adhesive sheet. 10 The above (B) is a bisphenol type epoxy methacrylate resin in which methacrylic acid is added to a bisphenol type epoxy resin, a novolak type epoxy methacrylate resin in which methacrylic acid is added to a novolak type epoxy resin, and polyhydric alcohols. The essential components are at least one selected from aliphatic epoxy methacrylate resins obtained by adding methacrylic acid to glycidyl ether type epoxy resins, a copolymerizable crosslinking agent, and a radical polymerization initiator. A thermosetting adhesive sheet according to any one of claims 7 to 9. 11 The radical polymerization initiator contained in (B) above is
Claims 7 to 10, characterized in that it decomposes and generates radicals within the range of 100 to 200°C.
The thermosetting adhesive sheet according to any one of the above. 12 The mixing ratio of (A) to (B) is 1/9 to
The thermosetting adhesive sheet according to any one of claims 7 to 11, wherein the thermosetting adhesive sheet is within the range of 9/1.