JPH0441581A - Adhesive composition for flexible board - Google Patents

Abstract

PURPOSE:To obtain an adhesive composition for a flexible board which is excellent in heat resistance, particularly, in heat-resistant adhesiveness by compounding a specific acrylonitrile-butadiene copolymeric rubber with an epoxy resin. CONSTITUTION:An adhesive composition comprising an epoxy resin and an acrylonitrile-butadiene copolymeric rubber in which not less than 90% of the double bonds derived from the constituting conjugated diene monomer are hydrogenated and the vart derived from the unsaturated nitrile unit amounts to 33 to 45wt.% of the copolymeric rubber, the content of the copolymeric rubber amounting to 15 to 35wt.% per 100 parts by weight of the epoxy resin. The composition is an adhesive composition for a flexible board provided with well-balanced characteristics such as flexibility, heat-resistance, electrical property, adhesiveness and soldering heat resistance. This adhesive composition can provide a highly reliable flexible board since it is particularly excellent in heat resistant adhesiveness and satisfies the UL specifications.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an adhesive composition for flexible substrates with improved heat-resistant adhesive properties.

<Conventional technology> As electric/electronic equipment, small precision equipment, etc. become lighter, thinner, and smaller, the area occupied by wiring has become smaller, and flexible wiring boards (hereinafter referred to as FP), which enable three-dimensional wiring with a high degree of freedom, are becoming more and more popular.
The demand for C) is becoming increasingly high.
The flexible substrate, which is the substrate material of this FPC, is made by bonding a metal foil, such as a copper foil or an aluminum foil, and a plastic film, such as a polyimide film or a polyethylene terephthalate film, with an adhesive.

Incidentally, the properties required for such flexible substrates are wide-ranging, including mechanical, chemical, electrical properties, long-term heat resistance, and flame retardancy, but the characteristics of the adhesive used in particular are
This has a large impact on the characteristics of the flexible substrate itself.
Therefore, as electrical and electronic equipment becomes more multifunctional and diversified,
There is a growing need for adhesives that have a good balance of properties such as flexibility, heat resistance, electrical (resistance) properties, adhesiveness, and soldering heat resistance, and that provide high reliability.

Conventionally, adhesives in this field have been made with epoxy resin as the main ingredient, which has excellent adhesiveness, heat resistance, and electrical properties, and to which thermoplastic resins, rubber, etc. that are compatible with the epoxy resin have been added to give flexibility. has been widely used. More specifically, modified acrylonitrile is an epoxy resin into which NBR and, if necessary, at least 1 ai functional groups selected from epoxy groups, hydroxyl groups, carboxyl groups, amino groups, alkyl ester groups, etc. are introduced. Those with added nitrile rubber such as butadiene copolymer (e.g., JP-A-62-499627) Those with acrylic resin added to epoxy resin (e.g., JP-A-64-36670)
etc. have been used.

However, nitrile rubber and acrylic resin have double bonds in their molecules, so they have poor heat resistance and heat-resistant adhesive properties. In this case, the heat resistance and heat-resistant adhesion of the adhesive layer were significantly reduced and could not be put to practical use.

In addition, in order to provide adhesives with the above-mentioned properties in a well-balanced manner, studies have been conducted from the perspective of the main agent.For example, phenolic resin adhesives whose main ingredient is phenolic resin, and adhesives using special epoxy resins are being developed. (Unexamined Japanese Patent Publication No. 01301
No. 778) etc. have also been proposed.

However, it is generally known that phenolic resin adhesives tend to absorb moisture and have poor soldering heat resistance.

<Problems to be Solved by the Invention> As mentioned above, as an adhesive composition for flexible substrates, it is necessary to blend a composition with a good balance of various properties such as flexibility, heat resistance, electrical properties, adhesiveness, and soldering heat resistance. is very difficult.

The present invention has been made in view of these circumstances, and aims to provide an adhesive composition for flexible substrates that has excellent heat resistance, particularly heat-resistant adhesion, and maintains the level of conventional adhesives in other properties. purpose.

Means for Solving the Problems The present invention provides an epoxy resin and an acrylonitrile-butadiene copolymer rubber, in which 90% or more of the double bonds derived from the conjugated diene of the constituent monomers are hydrogenated, and a copolymer rubber containing 33 to 45% by weight of a unit portion from unsaturated nitrile, and the copolymer rubber content is 15 to 3 parts by weight based on 100 parts by weight of the epoxy resin.
5 parts by weight of an adhesive composition for a flexible substrate.

The present invention will be explained in detail below.

The epoxy resin used in the present invention is not particularly limited as long as it is an epoxy resin.

General-purpose epoxy resins include glycidyl ether epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, novolak epoxy resin, and brominated epoxy resin, as well as cycloaliphatic epoxy resins, glycidyl ester epoxy resins, Examples include glycidylamine-based epoxy resins, heterocyclic epoxy resins, etc. In addition, epoxy resins modified with amine groups, oxazolidinone groups, or urethane are also known, so one or more of these may be used. Just use it.

In addition, from the viewpoints of adhesion, heat resistance, compatibility with the copolymer rubber described later, flame retardance, workability, etc., glycidyl ether type,
Epoxy resins such as those modified with oxazolidinone are preferred.

The copolymer rubber used in the present invention is a copolymer rubber having heat resistance, and is a rubber having the following structure obtained by hydrogenating NBR or the like.

That is, it is an acrylonitrile-butadiene copolymer rubber in which 90% or more of the double bonds derived from the conjugated diene of the constituent monomers are hydrogenated, and the unit portion from unsaturated nitrile is 33 to 45% by weight. It is a copolymer rubber containing.

Here, unit portions 33-451 from unsaturated nitriles!
The amount is %. If it is less than 33% by weight, the adhesiveness with the film will be poor, and if it exceeds 4511% by weight, the electrical properties will be poor.

In addition, 90% or more of the double bonds derived from the conjugated diene of the constituent monomers (butadiene, isoprene, etc.) are hydrogenated, but if the hydrogenation is less than 90%, the desired improvement in heat resistance will not be achieved. I can't.

Specific examples of such copolymer rubbers include acrylonitrile-butadiene copolymer rubber, acrylonitrile-isoprene copolymer rubber, acrylonitrile-butadiene-isoprene copolymer rubber, and acrylonitrile-butadiene-copolymer rubber.
Hydrogenated rubbers include methyl acrylate copolymer rubber, acrylonitrile-butadiene-styrene copolymer rubber, acrylonitrile-ethylene-butadiene copolymer rubber, acrylonitrile-butyl acrylate nitoxyethyl acrylate vinylnorporene copolymer rubber, etc. It will be done. However, only a few of these are currently produced industrially.

These copolymer rubbers may be used alone or in combination of two or more, and in some cases in combination with other rubbers within the scope of the invention.

In the present invention, the copolymer rubber is 15 to 35 parts by weight, preferably 25 to 30 parts by weight, based on 100 parts by weight of the epoxy resin.
Use parts by weight. If it is less than 15 parts by weight, heat resistance,
In particular, the heat-resistant adhesiveness and flexibility are insufficient, and on the other hand, if it exceeds 35 parts by weight, the heat resistance, especially the heat-resistant adhesiveness and electrical properties are poor, which is not preferable.

In addition to the above-mentioned essential components, the adhesive composition for flexible substrates of the present invention contains an epoxy resin curing agent. Examples of curing agents for epoxy resins include aromatic amine compounds such as diaminodiphenylmethane and metaphenylenediamine, aliphatic amine compounds such as diethylenetriamine and influorondiamine, acid anhydrides such as methylhexahydrophthalic anhydride, Furthermore, polyamide resin,
In addition to imidazoles, latent curing agents such as boron trifluoride-amine complex, dicyandiamide, organic acid hydrazide, etc. are known, but not limited to these examples, other commonly used curing agents can also be used. may be used.

In addition, preferable curing agents used in the present invention include aromatic diamine compounds and aliphatic diamine compounds.

Furthermore, various additives can be added to the adhesive composition of the present invention. Examples include curing accelerators, inorganic fillers, flame retardants and flame retardant aids, anti-aging agents, and the like.

The curing accelerator is one that promotes ring-opening polymerization of epoxy groups, and compounds having alcoholic and phenolic hydroxyl groups, such as n-butanol and phenol, can be used.

Inorganic fillers are used to improve coatability, insulation, soldering heat resistance, etc., and examples include alumina and silica.

As the flame retardant, aluminum hydroxide, phosphate ester compounds, brominated aromatic compounds, etc. are used.

Further, in order to enhance the flame retardant effect of the halogen flame retardant, a flame retardant aid such as antimony trioxide or antimony pentoxide may be used in combination.

For the shell, adding flame retardants or flame retardant aids to the adhesive composition
This is not preferred because it significantly reduces adhesive strength. However, it is preferable to use surface-treated antimony pentoxide as a flame retardant aid because flame retardancy can be imparted without reducing adhesive strength.

As the anti-aging agent, a hindered phenol compound or the like is used.

The adhesive composition of the present invention can be obtained by mixing each component in a conventional manner, and when producing a flexible substrate, it is mixed with metal foil such as copper foil or aluminum foil, polyimide film, polyethylene terephthalate film, etc. It can be used for adhesion with films such as, but after mixing each component, it is applied in the form of a film with a thickness of about 15 to 30 μm, and it is cured to a certain extent to reach a so-called B stage state. It is better.

<Examples> Next, the present invention will be described in more detail based on Examples.

(Example) Various adhesive compositions whose compositions are shown in Table 1 were manufactured by conventional methods, and copper foil and polyimide film were bonded together using these adhesives. 1-3 at 150-170℃
The material was cured for a period of time to produce a flexible copper clad board.
For these samples, the adhesive strength under normal conditions and after heat aging, and the MIT bending durability were measured.

To measure the adhesive strength, use copper foil 1 mm wide (base material width 10 mm).
Using samples etched with
After leaving the sample in an oven at 0° C. for a predetermined period of time, the 90 degree peel strength was measured using a tensile tester. The tensile speed is 50 mm
I did it in 7 minutes.

The MIT bending durability was evaluated using an MIT bending tester using a sample obtained by etching a copper foil with a width of 0.5 mm (substrate width 15 mm).

The loading conditions were a bending jig radius of 0.8 mm, a static load of 0.5 Kgf, and a bending speed of 175 times/min, and the number of bends at which an abnormality occurred in the sample was expressed.

The results are shown in FIG. 1, FIG. 2, and Table 1. FIG. 1 is a graph showing the relationship between thermal deterioration time and adhesive strength for Example 4 and Comparative Example 1.

As is clear from the figure, in Comparative Example 1, in which ordinary NBR was added, the adhesive strength significantly decreased due to short-term thermal deterioration, whereas in contrast, highly hydrogenated NB, which has very few double bonds,
In Example 4, in which R was added, the decrease in adhesive strength due to thermal deterioration was very small.

The second section is Z, S which is Takagi tNBR as a copolymer rubber.
, C-2275 is a graph showing the relationship between normal adhesive strength or MIT folding durability and copolymer rubber content.

From the figure, it is clear that the normal adhesive strength is maximum when the copolymer rubber content is about 28 parts by weight, and that the adhesive strength is insufficient when the copolymer rubber content is less than 15 parts by weight or more than 35 parts by weight. Furthermore, the MIT folding durability increases as the copolymer rubber content increases, but it is clear that the effect of the copolymer rubber is saturated at about 35 parts by weight.

Furthermore, as shown in Table 1, with respect to the adhesive strength after thermal deterioration, all of the Examples showed that even after being subjected to thermal deterioration at 150°C for 10 days, the adhesive strength was at least at least as high as the initial (normal) adhesive strength. The adhesive strength was 50%, and the heat-resistant adhesiveness was significantly deteriorated compared to Comparative Example 1 (10%). In the examples, most of the samples satisfied the UL standard (adhesion strength after thermal deterioration of 150'C for 110 days was 0.54 g/cm or more).

Furthermore, the MIT bending resistance, which is one of the indicators of flexibility, can be maintained at the conventional level in the example.

<Effects of the Invention> The present invention provides an adhesive composition for a flexible substrate that has well-balanced properties such as flexibility, heat resistance, electrical properties, adhesiveness, and soldering heat resistance.

The adhesive composition of the present invention has particularly high heat-resistant adhesion properties (concerns, UL
Since it satisfies the standards, the invention makes it possible to provide highly reliable flexible substrates.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between thermal deterioration time and adhesive strength indicated by 90 degree peel strength. FIG. 2 is a graph showing the relationship between the normal adhesive strength or MIT bending durability indicated by 90 degree peel strength and the content of copolymer rubber which is highly hydrogenated NBR. F I G. Pubishi inferior/n 21 days Y interval

Claims (1)

[Claims] (1) Epoxy resin and acrylonitrile-butadiene copolymer rubber, in which 90% or more of the double bonds derived from the conjugated diene of the constituent monomers are hydrogenated, and the unit portion derived from unsaturated nitrile is hydrogenated. 33-45% by weight
An adhesive composition for a flexible substrate, characterized in that the content of the copolymerized rubber is 15 to 35 parts by weight based on 100 parts by weight of the epoxy resin.