JP2552502B2 - Heat resistant film and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-resistant film having a coating layer formed on a substrate and a method for producing the same.

[Conventional technology]

Flexible films and sheets having a thermoplastic resin as a base material (hereinafter collectively referred to as films) are
Due to the flexibility provided in them, they have a high degree of freedom in design and have some degree of insulation, but their use is limited due to generally insufficient heat resistance. There is. Conventionally, among untreated films used as a substrate, there is a film made of engineering plastic such as polyimide (PI) as one having relatively excellent heat resistance, but the resin itself is expensive. In addition, since it requires a high-level processing technique to process the film, it becomes more expensive, and it is difficult to use for general purpose applications. Therefore, in recent years, various researches have been conducted on a film having heat resistance superior to that of an untreated film made of the base material itself, even though an inexpensive thermoplastic resin is used for the base material itself. Various films have been proposed.

One of them is a film based on a composition in which a predetermined additive is mixed with polyvinyl chloride resin (PVC), which is a typical thermoplastic resin that is inexpensive and easily available. However, in the method of improving the heat resistance of the base material by mixing the additive material, it is often necessary to adjust various additives by mixing them in order to obtain the target heat resistance property. It has been pointed out that the transparency and other physical properties also change significantly.

On the other hand, by forming a coating layer on a base material made of a thermoplastic resin, it may be possible to obtain a film having heat resistance characteristics that cannot be obtained by the base material itself. According to such a film, the physical properties such as transparency of the base material itself are not significantly impaired, and the coating layer may provide heat resistance characteristics that cannot be obtained by the base material itself. Conventionally, in such a film, a means of generally baking a coating layer on a base material made of a thermoplastic resin under a low temperature condition where shrinkage or wrinkling does not occur has been considered. However, the heat resistance of the film having the coating layer correlates with the baking temperature of the coating layer, and it was assumed that the degree of improvement in heat resistance would be relatively small when baked at such a low temperature. Further, there is a heat resistant film obtained by impregnating a heat resistant resin such as glass fiber into a sheet shape with a heat resistant resin and laminating it on an existing film, but it tends to lose flexibility as it becomes thicker. However, it has not been perfectly suitable for applications such as a flexible printed wiring board which is thin and requires flexibility. Therefore, in any case, it is difficult to say that the conventional film is still a sufficient heat resistant film.

[Problems to be solved by the invention]

As described above, the heat-resistant film that has been assumed in the past may have some improved heat resistance as compared with the untreated film composed of the base material itself, but it still has sufficient heat resistance. It is hard to say that other existing heat-resistant films are in terms of thickness, flexibility and cost as described above, and other physical properties are impaired when heat resistance is improved by admixture of additives, etc. There is a problem that it is still insufficient as a heat resistant film.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heat resistant film in which a thin film serving as a coating layer is baked on a base material at a high temperature, and a method for producing the same.

[Means for solving problems]

In order to achieve the above object, the heat-resistant film of the present invention, a substrate made of triacetate resin (TAC) or methyl methacrylate resin (MMA), epoxy resin, a thin film of one or two resins selected from melamine resin It is characterized by being baked.

Further, the method for producing a heat-resistant film of the present invention, a substrate composed of TAC or MMA, a phenol resin, an epoxy resin, to form a thin film of one or more resins selected from melamine resin, the thin film flat It is characterized in that it is maintained in the shape-retained state and baked at a temperature of 150 to 300 ° C.

〔Example〕

 Examples of the present invention will be described below.

Figure 1 is a cross-sectional view of a heat-resistant film, where 100 is the base material and 200
Indicates a coating layer composed of a thin film baked on the substrate 100.

The base material 100 is selected from TAC or MMA. TAC is excellent in transparency, flatness, heat resistance, waist strength, flexibility, durability, and mechanical properties, and is used for photographic films, recording tapes, electrical insulating materials, etc. In addition, MMA has excellent transparency as well as heat resistance. The base material 100 is 1 to 350 in terms of workability.
It is desirable that the film has a thickness of about μ. If the thickness is less than 1μ, the handling will be poor and the strength will be insufficient.
If the thickness is thicker than 350μ, there is a risk of lack of design freedom. This thickness is not limited to the above range, and may be thicker if only heat resistance is pursued.

For the coating layer 200 made of a thin film, one kind or two or more kinds of resins selected from a phenol resin, an epoxy resin and a melamine resin are used. The phenol resin, epoxy resin, and melamine resin may be used as an aqueous solution or an alcohol solution, or may be used as they are. Coating layer 20
The resin to form 0 needs to be varnished, 1
It is necessary to cure at a temperature of 50 to 300 ° C. and have adhesiveness to the substrate. Specifically, phenolic resin,
There are cases where the epoxy resin and the melamine resin are used alone, and cases where two or more kinds of the phenol resin, the epoxy resin, and the melamine resin are used in combination.

The phenol resin may be a straight phenol resin or a modified phenol resin. Alcohols such as methanol and isopropanol (IPA) are used as this solvent. Modified phenolic resins include phenolic resins such as epoxy-modified, melamine-modified, and inorganic-modified (B ₂ O ₃ , P ₂ O ₅ ). Particularly, when a melamine-modified or epoxy-modified phenolic resin is used, high adhesion to the substrate is achieved. Sex is secured. Of these two, the epoxy-modified phenolic resin exhibits particularly high adhesion. In addition, a surfactant and a fine powder filler of organic, inorganic, or metal may be appropriately added to the coating solution as needed. In this case, the organic fine powder filler is, for example, a fine powder of Si-Ti-CO or benzoguanamine, and the inorganic fine powder filler is, for example, a fine powder of silicon carbide (SiC) or boron nitride (BN). However, aluminum oxide (Al
A fine powder such as ₂ O ₃ ) is used. When melamine resin is used as the coating layer, high transparency can be maintained. The above is an example, and the thin film for forming the coating layer should be appropriately selected in consideration of its properties and suitable for the purpose of use of the film to be produced. Further, as the melamine resin and the epoxy resin, generally known ones are used. Further, each of the phenol resin, melamine resin and epoxy resin may be used as a modified product or derivative.

It is desirable that the thickness of the thin film after baking is 1 to 10 μ in dry, and sufficient heat resistance and flame retardancy can be obtained even with such a thickness.

The coating layer 200 is a thin film formed by applying the above-mentioned aqueous solution, alcohol solution or resin to the base material 100 to form a thin film at 150 to 300 ° C.
However, if the baking temperature is too high, not only bleeding from the base material 100 and other physical property values are lowered, but also problems such as large shrinkage and wrinkles are likely to occur, and the performance as a film is impaired. . The baking temperature capable of maintaining the performance as a film is 300 ° C or lower. Baking temperature is 1
If it is lower than 50 ° C, sufficient heat resistance and adhesion cannot be obtained. Further, it is desirable that the baking time is set to about 0.5 to 5 minutes. Here, it should be noted that baking is performed not only by setting the temperature condition in the above range but also by maintaining the substrate 100 in a flat shape without causing slack.

By the way, if specific tension is positively applied to the base material 100 during heat treatment to prevent slack, the base material 100 is forcibly stretched and it becomes difficult to maintain its shape. However, in the method of the present invention, when the base material 100 is flatly held so as not to cause slack without positively applying a tensile force to the base material 100 during the heat treatment, as a result, the base material 100 is It is possible that tensile forces may be applied and are then within the scope of the method of the invention. When shape-retaining and baking are performed in this manner, the heat resistance of the thin film formed on the surface, combined with shape retention, causes the base material 100 to deform despite being heated at a temperature higher than its melting point. However, a high degree of smoothness is imparted to the film surface. In order to enhance the smoothness of the film surface, a drum may be used to press the film from above and below.

FIG. 2 is a flow sheet of manufacturing steps for carrying out the method for manufacturing a heat-resistant film of the present invention. Reference numeral 1 is a base material feeding machine, 2 is a dipping coater for coating liquid or coating resin, 3 is a drying furnace, 4 is a baking furnace, 5 is a trimming device, and 6 is a winding machine. As is clear from the figure, the base material 100 delivered from the delivery machine 1 has a thin film of the coating liquid or coating resin formed on one or both surfaces thereof while passing through the dipping coater 2, and the thin film is fed to the drying furnace 3. It is dried while passing. Then, the substrate 10
While passing 0 in a flat shape, the thin film is baked at a predetermined temperature while passing through the baking furnace 4 to form a coating layer. The film thus obtained is trimmed and then wound up by the winder 6.

In the above, the base material before entering the dipping coater 2
It is useful to increase the surface activity of the base material 100 by subjecting it to a primer treatment or corona discharge treatment, and to subject the base material 100 to an electrostatic removal treatment or a dust removal treatment in order to enhance the adhesion of the coating layer.

FIGS. 3 and 4 show an example of an apparatus for maintaining the shape-retaining state.
It is shown in the figure. This device comprises a pair of left and right endless rotating bodies formed by connecting a large number of endless clip mechanisms 10 shown in FIG.
11, 11 are attached to the base 12 so that one ends thereof or the other ends thereof can individually approach and separate from each other. As shown in FIG. 4, in the clip mechanism 10, the bracket 14 provided on the support base 13 has a position where the claw 15 at the tip of the base material 100 grips the support base 13 and the support base 13. An arm 16 is attached so as to be displaceable between the arm 16 and the position approaching the bracket 14 side, and a spring for constantly urging the claw 15 toward the pinching position side between the arm 16 and the bracket 14. The outer peripheral portion of the control rotary plate 18 provided on the winding roller of the endless rotary body 11 is mounted on the upper end portion of the arm 16 by interposing 17
It corresponds to 19 from the side.

In the above structure, when the endless rotary body 11 is rotationally driven in the direction of the arrow in the figure, the arm 16 of the clip mechanism 10 is moved to the position of the phantom line in FIG. The claw 15 swings away from the support base 13, and at other portions, the arm 16 returns to the position shown by the solid line in the figure, and the claw 15 corresponds to the support base 13. Therefore, when the base material 100 on which the thin film is formed is fed between the pair of endless rotating bodies 11, 11,
Both ends of the base material are clipped at the entrance of the device.
After being supported by 10 as shown by the solid line in FIG. 4, it reaches the outlet portion of the same device as it is, and the holding is released at this outlet portion. Here, for the base material 100 made of a thermoplastic resin that expands by heating, a pair of endless rotating bodies 11,
Make the interval of 11 gradually wider as it approaches the exit side,
For a base material 100 (for example, a stretched base material) made of a thermoplastic resin that shrinks by heating, if the above-mentioned interval is gradually narrowed as it approaches the outlet side, the base material during passage through the baking furnace 4 Since the substrate 100 does not sag, the substrate 100 does not flow, the substrate 100 is maintained in a flat shape, and the surface smoothness is not impaired. It should be noted that FIG. 3 illustrates a case where a base material made of a synthetic resin that shrinks by heating is fed by an imaginary line.

As described above, when the substrate is held flat and the thin film is baked, the substrate does not shrink or wrinkle, and the performance of the film is not impaired. In particular, in the present invention, since the baking temperature is relatively high, it is important to keep the shape of the substrate flat.

 Next, an experimental example will be described.

[Experimental example]

Table 1 shows the type of substrate, the type of coating layer, the thickness, etc. of the film produced by the present invention (hereinafter referred to as heat resistant film), and Tables 2 and 3 show the heat resistant film 1 and heat resistance. The various properties of film 2 are shown. Also, the fourth
The table shows the characteristics of untreated film (hereinafter referred to as comparative product), which has TAC, MMA, and PI as base materials and has no coating layer.

From Tables 2 to 4, the heat resistance of the heat resistant films 1 and 2 is significantly improved compared to the respective base materials (comparative products 1 and 2) which are untreated films, and the coating layers have excellent heat resistance. As a result, it can be seen that the heat resistance of the film using TAC as the base material is close to that of the film containing PI alone as the base material (comparative product 3). For example, the heat resistance of the heat resistant film 1 is the lower limit of the baking temperature condition of the present invention. Fifteen
Even when it is baked at 0 ° C, it is improved by about 10 ° C as compared with the untreated film made of only the TAC substrate (Comparative product 1). Then, the heat resistance of the heat resistant film 1 when the baking temperature is set to a high temperature, for example, 270 ° C. or higher approaches the heat resistance of the untreated film made of only PI (Comparative Product 3). From this, it can be seen that the heat-resistant films 1 and 2 can be upgraded in heat-resistant properties as compared with the untreated film. Therefore, it is apparent that the application range of these heat resistant films 1 and 2 is expanded as compared with the application of the untreated film. Further, the heat shrinkage rate is higher than that of the base materials TAC and MMA, and the higher the baking temperature, the better the shrinkage resistance.

Further, the heat-resistant films 1 and 2 have higher heat resistance as the baking temperature of the thin film is higher, and the flame retardancy is equivalent to that of the comparative product 3,
The adhesion between the base material and the coating layer, solvent resistance, alkali resistance, etc. are generally good for each of the invention products, and the water absorption is significantly smaller than that of Comparative product 3. It is also found that the alkali resistance is superior to that of the comparative product 3.

By the way, by utilizing the flexibility of a film whose base material is a thermoplastic resin, a flexible printed wiring board (FPC) or a base film of a capacitor or a transparent electrode,
Attempts have been made to use it in the fields of electronics such as heat-resistant conductive films, liquid crystal films, and IC carrier tapes, membranes used for dialysis and diffusion, interior materials for aircraft and automobiles, and nuclear power related fields. When the above film is used, heat resistance and flame retardancy are required according to its processing conditions and usage conditions. For example, when it is used as a base film for FPC, it is exposed to high temperatures during soldering, and therefore heat resistance and flame retardancy at a soldering temperature of about 250 ° C. are required. From the above table, it is clear that the heat-resistant film 1 baked at 270 ° C or higher can be used as a material that can meet this demand, and by using it, the flexibility of the FPC for curved surfaces can be utilized. There is an advantage that it can be deployed. Further, the interior materials of aircrafts and automobiles are required to have flame retardancy, which is satisfied by all heat-resistant films obtained by the production method of the present invention.

 Next, a test method and the like of each item will be described.

Adhesion: Make a lattice-like cut on the coating layer with a leather blade, 24
A cellophane tape with a width of mm is attached, and the presence or absence of peeling of the coating film when the cellophane tape is rapidly peeled off is visually observed. O indicates that there was almost no peeling. The heat resistant films 1 and 2 are not peeled off.

Solvent resistance: According to JIS C-6481 5.13, dip each in acetone, MEK, toluene and trichlene for 5 minutes at room temperature. O indicates that peeling or dissolution was hardly observed, and X indicates that peeling or dissolution of the coating film was observed and the coating film was released by rubbing. The heat-resistant films 1 and 2 have sufficient solvent resistance, and it can be understood from this that they can sufficiently withstand etching treatment and the like.

Heat resistance: Cut a film with copper foil stuck on it to a size of 5 cm x 5 cm,
In the oil bath or solder bath at each temperature shown in the table
Soak for 10 seconds.

Flame retardance: Judged by UL-94 VTM.

〔The invention's effect〕

As explained above, the heat-resistant film of the present invention exhibits sufficient heat resistance and flame retardancy, and it is possible to obtain a thin film having excellent flexibility, and the adhesion between the coating layer and the substrate. Since it has excellent properties, solvent resistance, shrinkage resistance, etc., it is also used as an insulating film, heat-resistant conductive film, membrane, etc. in the field of electrical materials, industrial materials and construction materials, and other food packaging, medical, clothing, etc. It can be used universally.

Further, the manufacturing method of the heat-resistant film of the present invention, a thin film is formed on the substrate, because it is to maintain the flat shape of the film is baked, the baking temperature is 150 ~ 300 ℃ high temperature However, there is an advantage that the manufactured heat-resistant film does not have wrinkles.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of the heat-resistant film of the present invention, FIG. 2 is a flow sheet showing a manufacturing process of the heat-resistant film of the present invention, and FIG. 3 is an apparatus for maintaining a shape of a base material. FIG. 4 is a schematic partially cutaway side view of the clip mechanism. 100 …… Base material, 200 …… Coating layer.

Claims (2)

(57) [Claims] 1. A heat resistant film comprising a base material made of a triacetate resin or a methyl methacrylate resin, and a thin film of one or two kinds of resins selected from an epoxy resin and a melamine resin baked on the base material. 2. A state in which a thin film of one or more resins selected from a phenol resin, an epoxy resin, and a melamine resin is formed on a substrate made of a triacetate resin or a methyl methacrylate resin, and the thin film is kept flat. A method for producing a heat-resistant film, characterized in that the film is maintained at 150 ° C. and baked at a temperature of 150 to 300 ° C.