JPS61215054A - Laminated film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to adhesive technology for laminating copper-clad printed circuits for sheet coils for flat motors, for example, and particularly for bonding technology that has high heat resistance and high lamination density. The present invention relates to a laminated film that can be used in thin, high-density laminations to achieve excellent adhesive performance and insulation performance.

<Prior art and its problems> For example, when laminating copper-clad printed circuits for sheet coils for flat motors, one conventional method is to impregnate glass fiber with thermosetting resin or thermoplastic resin. The circuit is bonded using prepared prepreg to ensure circuit lamination and insulation.

This method is a common method for laminating ordinary printed circuits, but since the density of the lamination is limited by the thickness of the prepreg, it is not suitable for high-density lamination. In order to achieve high-density lamination, both sides of polyester for insulation (
A laminated film is used in which a thermosetting adhesive diluted with a solvent is coated on one side) and the solvent is volatilized.

Although this method uses a complete set of laminating equipment and uses a solvent, (1) traces of the solvent become minute irregularities, resulting in uneven thickness.

(2) Residual solvent causes foaming during heat curing.

(3) Adhesion failure is likely to occur due to residual solvent.

(4) Galvanic corrosion is likely to occur due to gases sorbed by residual solvent.

There were some drawbacks.

In addition, some attempts have been made to bond adhesives that harden at room temperature by brushing, etc., but they have no storage stability and are not easy to work with, and the adhesive strength when heated is significantly inferior. It has its drawbacks and cannot be called an excellent technology.

OBJECT OF THE INVENTION The present invention aims to provide a volatile-free laminated film to be produced in a completely solvent-free process, thereby eliminating the numerous disadvantages caused by residual solvents, especially for high-density The present invention aims to provide a laminated film that can be used as a heat-resistant laminated film for copper-clad printed circuits.

<Structure of the Invention> The present invention provides a laminated film in which a layer of a thermosetting solvent-free adhesive with a softening point of 3O-Zoo' (!) is provided on one or both sides of a polyester film.

The laminated film of the present invention will be explained in more detail below.

In the laminated film of the present invention, a polyester film is used as the base material. Examples of films that are currently widely sold include Mylar (Dupont), Lumirror (Toshi), and Diafoil (Mitsubishi Plastics), all of which are polyester films with almost the same performance.

The thickness of the base material can range from several microns to several hundred microns, but in consideration of both film strength and lamination density, a base material of 10 to 20 microns is preferably used.

As is well known, polyester film has higher heat resistance than polyethylene or polypropylene and is an excellent material for electrical insulation films, but it is also a material that is difficult to bond to the other side, so various improvements have been made to the adhesive and pre-adhesion treatment. being done. The adhesives shown in the examples of the present invention adhere well to polyester films without any surface treatment, but in cases where the adhesion is somewhat weak, effective adhesion can be expected by performing plasma treatment. . However, in this case, it should be noted that the plasma treatment causes coloration and a decrease in strength of the film, and this is more pronounced as the film becomes thinner.

Solvent-free adhesives mean, of course, that no solvent is mixed during manufacturing, but they also have zero volatile content.
．． It is also required that the content be 5 wt% or less. Therefore, especially when adding a low molecular weight non-reactive material for any purpose, care must be taken regarding the boiling point of the material.

A thermosetting adhesive is a chemical reaction that is promoted by heat, and the polymers and prepolymers connect with each other to form a three-dimensional network structure and solidify. It refers to adhesives that obtain adhesive strength through force, covalent bonds, or ionic bonds, and typical examples include epoxy adhesives, acrylic adhesives, phenolic resin adhesives, and polyimide adhesives.

It is preferable to use a specially prepared device for the coating method, without using a normal laminating device. It can be implemented if This method is an example of a specific coating method, and it goes without saying that other coating methods may be used.

Table 1: Coating method As mentioned above, there are epoxy adhesives, acrylic adhesives, etc., and these will be explained in detail.

It is preferable to use an epoxy resin that is solid at room temperature or a mixture of it and an epoxy resin that is liquid at room temperature, in which a burnability imparting agent, a filler, etc. are added if necessary, and a latent hardener is added. Ru. The coating process is carried out at 80-100' (3
The viscosity at this time is several thousand voids or less, and it is possible to form a sheet using a comma coater. In particular, the polyester may be surface-treated or an adhesion promoter or a coupling agent may be added to enhance the adhesion to the polyester film.

Acrylic 7: An acrylic monomer, an acrylic oligomer mixed with acrylic rubber if necessary, and a peroxide or the like as a catalyst are used. The process is similar to that used for epoxy adhesives, including adding fillers and anti-sagging agents for flow control.

It is preferable to use the above-mentioned adhesive having a softening point of 30 to 100° C. as measured by the Ba1l & Ring method. If the softening point is less than 30℃, during gluing work,
This is because the adhesive is highly sticky and hinders work, and when the temperature exceeds 100°C, the viscosity immediately before curing is too high and the adhesive layer becomes thick.

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.

(Example-1) Table-2 Adhesive formulation (softening point: 52°C) Using the coating equipment shown in Figure 1, the adhesive listed in Table-2 was released by heating with 80°C hot water. On the pattern paper, 40, 80IL, 120. It was applied to a thickness of . A polyester film (12JL) was laminated thereon and wound up to create a single-sided coated film.

Furthermore, on the polyester side of the single-sided coated film rolled up together with the release paper, adhesive was applied to the desired thickness in the same manner as before, and the film was rolled up to create a double-sided coated film.

Using a film coated with 601L adhesive on both sides, two sheets of rolled copper foil with a thickness of 40IL were bonded together.
Pressing was performed at 80° C. for 3 minutes. In this way, a bonded copper foil having a total thickness of 100 g was obtained. Note that the excess adhesive is flowing out from the sides. Since the adhesive thickness is 20IL including the 12g polyester film thickness, the adhesive thickness on one side is 411. It can be considered as a separate adhesive layer.

This bonded copper foil was cut to a width of LC and subjected to a T-peel test, and the results shown in Table 3 were obtained.

Table 3 Peeling test (Example 1) Note: Tensile speed 50 in/in (Comparative example 1) The adhesive shown in Table 2 was solvent-free and was used in Example 1. Melt this adhesive with MEK and add 70% 5ol
Got the id dope. This dope is a condensed milk-like liquid and can be applied to a polyester film at room temperature. This dope was coated on the same polyester film as used in Example 1 using a spatula, and dried in an oven at 100° C. for 20 minutes to obtain a double-sided coated laminate film for a copper-clad laminate. This was laminated with rolled copper foil of 40p thickness according to the same procedure as in Example-1, and the total thickness was 1O.
A bonded copper foil of OIL was obtained. Table 4 shows the results of the T-peel test for Comparative Example 1.

Table 4 Peel Test (Comparative Example-1) The peel strength is about 50% lower on average than in Example-1 over the entire temperature range measured. This is only because a solvent was used.

Furthermore, referring to the point that Comparative Example-1 is inferior to Example-1, in the composition shown in Table-2, dicyandiamide is
Although it does not dissolve in the epoxy resin and/or MEK and is dispersed as fine particles, these particles settle when the adhesive is dissolved in MEK. For this reason, it requires constant stirring during use, which is complicated.

(Comparative Example 2) The same dope as in Comparative Example 1 was applied to a polyester film, the drying time was shortened, and the drying temperature was increased instead. After drying in an oven at 110° C. for 10 minutes, the same measurements as in Example-1 and Comparative Example-1 were performed. Regarding drying time, the production of such laminated films is usually done on a line, and the film flows along the line, but the line length required for each process depends on the speed of the line. This means that it is the product of the time required for the process. Temporarily increase the line speed to 2-3
For the drying conditions of Comparative Example-1, m/min is 40~
A 60m drying zone is required. Comparative Example 2 has the advantage that the distance is only 20 to 30 m. In Example=1 no drying zone is required at all.

Table 5 shows the results of the T-peel test for Comparative Example 2.

Table-5 Peeling test (Comparative example-2) It can be seen that the strength is even lower than that of Comparative Example-1.

In Comparative Example-2, a foaming phenomenon that was not observed in Example-1 or Comparative Example-1 appears. This is one of the direct causes of the decrease in adhesive strength (peel strength) and is clearly a result of the use of the solvent.

(Example-2) Table-6 Adhesive formulation Softening point: 45°C An acrylic adhesive composition having the formulation shown in Table-6 was molded into a laminated film in the same manner as in Example-1, and in the same manner as the others. A T-peel test was conducted on the laminated copper foil. Table 7 shows the test results. However, the copper foil used was electrolytic copper foil.

Table 7 Peeling test (Example 2) (Comparative example 3) A dope with a solid content of 80% was prepared by dissolving the composition shown in Table 6 in Doolol, and the same procedure as in Example 2 was made. A laminated film was made using the method described above, and a T-peel test was conducted on the laminated copper foil in the same manner as the others. Table 8 shows the test results. However, the copper foil used was electrolytic copper foil.

Table 8 Peel test (Comparative example 3) As can be seen from the results in Table 8, the adhesive strength was significantly lower than that of the same adhesive without solvent (listed in Table 7, Example 2). There is. Particularly at 150°C, the degree of decrease is remarkable. When the condition of the bonded surface was visually observed, it was observed that many random air bubbles were generated, and it was assumed that the residual solvent was vaporized during the curing process, and this was the cause. (Comparative Example 4) The same adhesive dope as in Comparative Example 3 was used, but only the drying conditions were changed to 100°C for 40 minutes to ensure sufficient drying of the solvent. The laminated film obtained in this way is free of solvent, but at the same time, the acrylic monomer volatilizes so much that curing does not progress sufficiently.
At lower temperatures, the peeling force is 200 to 400 g/cm, but it is close to adhesion, and the adhesive layer is thick (220JL when laminated with 40μ copper foil). ) It is also impossible to compare the data (it is a well-known fact that the thicker the adhesive layer, the stronger the peeling will be).

As explained above, the laminated film for copper foil printed circuits, etc. according to the present invention can not only be manufactured using a simple device that does not require a solvent drying zone or a solvent recovery device, but also can be manufactured using a conventional solvent-based adhesive. It has the advantage of eliminating disadvantages such as foaming and poor adhesion (deterioration).

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus for producing the laminated film of the present invention. Explanation of symbols 1...111f'7 paper, 2...heat roll, 3...
... Comma coater, 4... Pasting roll, 5...
・Heat roll, 6... Winding roll, 7... Tension roll, 8... Polyester film

Claims (1)

[Claims] Softening point 30 on one or both sides of polyester film
A laminated film provided with a layer of thermosetting solvent-free adhesive at ~100°C.