JPH0572873B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to flexible printed wiring boards (hereinafter referred to as
It's called FPC. ), relates to a heat-resistant film or sheet that can be suitably used as an insulating film or sheet for capacitors, motors, etc. [Prior Art] Conventionally, when improving a film or sheet formed from a thermoplastic composition to suit its intended use, it is necessary to impart specific physical properties to the composition corresponding to the intended use. A common method was to incorporate additives suitable for improving the performance. However, with this method, it is often necessary to mix a relatively large amount of additives in order to obtain the target physical property values, and as a result, transparency and other physical property values also increase as the additives are mixed in. The problem of change was pointed out. By the way, the above-mentioned FPC and insulating film or sheet have a high degree of design freedom when designing and mounting devices that achieve smaller size and higher density, so there is a lot of demand for them as electronic devices have become lighter, thinner, and smaller in recent years. It is expected. However, even if one attempts to use a film or sheet with improved target physical properties by the above method for these uses, it may not be possible to obtain the transparency, electrical properties, etc. required for the above uses. Therefore, it is difficult to say that it is suitable for practical use. For this reason, polyimide films have been used as films or sheets that can have the above-mentioned physical properties, but the films themselves are expensive and are not perfect in practical terms. On the other hand, by forming a coating layer on a base material formed from a thermoplastic composition,
Efforts have also been made to obtain films or sheets with physical properties that cannot be obtained from the base material itself. Such films or sheets (hereinafter, films or sheets with a coating layer formed on a base material are collectively referred to as coating sheets) include those with a flame-retardant coating layer formed on a polyethylene terephthalate (PET) base material. Ta. According to this type of coating sheet, the physical properties of the base material itself are not significantly impaired, and the coating layer formed on the base material can provide physical property values that cannot be obtained from the base material itself. Therefore, for example, a coating sheet in which a heat-resistant and flame-retardant coating layer is formed on a flexible base material can be used as an FPC that requires heat-resistant and flame-retardant properties. [Problems to be Solved by the Invention] However, when various considerations are made regarding the suitability of the above-mentioned conventional coating sheets for use in FPCs, it cannot be said that they are sufficient. In other words, the etching conditions, heating conditions, etc. when forming conductive patterns on FPC or soldering are
Because the processing process and usage conditions of FPC are harsh,
The coating layer is required to have excellent physical properties such as adhesion to the base material, solvent resistance, shrinkage resistance, heat resistance, and flame retardancy, but conventional coating sheets do not meet these properties sufficiently. It wasn't something I did. On the other hand, even when considering the suitability of conventional coating sheets for use as insulating films or sheets for capacitors and motors, it is difficult to say that they fully meet the various characteristics required for them. . The present invention improves the above-mentioned situation, and
An object of the present invention is to provide a heat-resistant coating sheet that is inexpensive and has sufficient flexibility as an insulating film or sheet. [Means for Solving the Problems] In order to achieve the above object, the coating sheet of the present invention is provided by applying a condensate of a resol type phenolic resin to one or both sides of a flexible thermoplastic base material using a solvent. The coating layer is formed by baking and thermally curing a coating film of a solution dissolved in . [Examples] Examples of the present invention will be described below. In the figure, 1 is a base material made of flexible thermoplastic plastic, and 2 and 2 are coating layers formed on both sides of the base material 1. This coating layer 2 is made of a condensate of resol type phenolic resin and isopropyl alcohol. A coating film made of a solution dissolved in methanol is baked and cured by heat. As is well known, resol-type phenolic resin is obtained by reacting phenol or cresol with formalin in the presence of a catalyst, but if the coating layer requires high insulation, it is necessary to It is preferable to use a reaction product of cresol and formalin in combination with alcohol. The molar ratio of formalin to phenol or cresol when blending varies depending on the application, but it may be about 1.0 to 5.0 molar as a coating layer for FPC or insulation phenol or sheets. In addition, alkaline catalysts such as NaOH, ammonia, and amines are used as catalysts, but if highly polar catalysts such as NaOH remain in the coating layer, water absorption increases, so when insulation is required, It's inappropriate. The resol type phenolic resin used in the present invention is a condensate of the above reaction, and its molecular weight is
It is about 100-400. When a condensate having a molecular weight in this range is used, the mechanical strength of the coating layer and the manufacturing workability of the coating liquid are good, and the weight of the coating sheet can be easily reduced. Next, methanol and isopropyl alcohol are used as solvents for resol-type phenolic resins. They were selected in consideration of their respective boiling points (methanol boiling point: 64°C, isopropyl alcohol boiling point: 82°C). In addition, as the solvent of the present invention,
Not limited to the above, ethanol (boiling point: 78℃), 1-propanol, (boiling point: 97℃)
℃), alcohols such as butanol (boiling point: 99.5℃), and methyl ethyl ketone (MEK, boiling point:
80℃) Methyl isobutyl ketone (MIBK, boiling point:
116°C), toluene (boiling point: 110°C), and xylene (boiling point: 140°C) can be selected in consideration of manufacturing workability and wettability and adhesion of the coating liquid.
Of course, the above-mentioned solvents including methanol and isopropyl alcohol may be used alone or in combination as appropriate. A particularly preferred blending ratio is, for example, 80 parts of a mixed solution of methanol and isopropyl alcohol as a solvent to 20 parts of the condensate of resol type phenolic resin, but is not limited to this. Condensate 10-30
The solvent may be, for example, 90 to 70 parts of a mixed solution of methanol and isopropyl alcohol. If the amount of condensate of the resol type phenol resin is less than 10 parts, the coating liquid will lack storage stability and problems such as secondary aggregation will occur, while if it exceeds 30 parts, the viscosity of the coating liquid will become too high and the coating process will be difficult. Not only does this deteriorate the properties and make it difficult to form a coating layer of uniform thickness, but also foaming and orange peel (mandarin orange peel) occur during baking, resulting in unfavorable surface conditions. In addition, in order to form a coating layer with a uniform thickness with good workability, the viscosity of the coating liquid must be adjusted to between 2 and 2.
It is desirable to adjust it to about 20CPS. In order to adjust the viscosity, it is effective to adjust the amount of solvent used. It is desired that the coating layer be as thin as possible in the range of 10μ or less (dry), with a particularly preferred range of 2 to 5μ. A coating layer with a thickness of more than 10 μm is more appropriately called a paint film, and when it becomes this thick, cracks and cracks due to bending, peeling from the base material, etc. are likely to occur. Therefore, it is not suitable as a coating layer of the coating sheet of the present invention, which requires flexibility. Moreover, the reason why the particularly preferable thickness of the coating layer is set to the above range is that it is sufficient to satisfy flexibility, good adhesion, heat resistance, and flame retardance. Since flexibility is required for FPCs and insulating films or sheets as described above, the base material needs to be flexible. Stretched as such a base material
Heat-resistant materials such as PET, polyarylate (PAL), polycarbonate (PC), polyvinyl chloride resin (PVC), polyphenylene sulfide resin (PPS), polysulfon resin (PSF), polyether sulfon resin (PES), etc. Plastics can be suitably used, and these have excellent tear strength, thermal elasticity, etc., and are highly flexible. The base material needs to have a thickness of about 6 to 125μ. If the base material is thinner than 6μ, not only will it not have the mechanical strength to withstand actual use as FPC, insulation film or sheet, etc., but it will also have poor heat resistance. It has poor characteristics and tends to cause trouble in soldering, etc. When the base material thickness is thicker than 125μ, it becomes difficult to ensure sufficient flexibility. The baking temperature of the coating film formed on the base material (coating film) is preferably about 200°C,
The baking temperature is set at a temperature at which the coating film is thermally cured and adheres uniformly and firmly to the substrate. Such a temperature range is 180-230°C. If the baking temperature is lower than 180℃, the baking will be insufficient and sufficient adhesion and hardness will not be obtained.If the baking temperature is higher than 230℃, it will cause bleeding from the base material and a decrease in other physical properties. This is because disadvantages such as large shrinkage and wrinkles occur. Next, an experimental example will be explained. [Example] Preparation of coating liquid A phenolic resin varnish with a resin solid content of 60% (Pryophene 5010 manufactured by Dainippon Ink and Chemicals Co., Ltd.) was selected as a condensate of a resol type phenolic resin, and this resol type phenolic resin 100 A coating liquid was prepared by mixing 100 parts of methanol and 100 parts of isopropyl alcohol as solvents and stirring and mixing with a closed type stirrer. Formation of Coating Layer The coating liquid obtained above was held on a film-like base material of a predetermined thickness to form coating films of various thicknesses, and the coating films were cured by baking at a predetermined temperature for a predetermined period of time. . Experimental results and discussion Next, we will discuss the substrate and type of the invented product, the method of forming the coating film, the baking temperature, the baking time,
Table 1 shows the thickness of the coating film, the thickness of the coating layer, etc. In the second section, the characteristics of the invented product and a commercially available flame-retardant coating sheet (a commercially available product with a flame-retardant coating layer formed on a PET base material) are compared. In addition, the manufactured coating sheets are shown as invention products 1, 2, 3, and 4. Among invention products 1 to 4 shown in Table 1, invention products 1 and 2 have a coating layer formed on one side, and invention products 3 and 4 have a coating layer formed on both sides. The present invention includes both sides,
Both single-sided and single-sided configurations are included, and are appropriately selected depending on the application. Also,
In Table 2, various properties of the untreated film on which no coating layer was formed are also listed. Furthermore, Company A's product is a melamine/polyester mixed resin with Br and P compounds added, Company B's is an epoxy resin with a phosphorus nitrogen compound added, and Teijin PNB-2 is a mixture of vinyl chloride and vinyl acetate. The polymer solution was mixed with methyl ethyl ketone: ethyl acetate: toluene = 1:1:1, tetrabromobisphenol A was added as a flame retardant, dibutyl phosphate was added as a curing catalyst, and butyl etherified melamine resin was added. It is something that From Table 2, except for Invention 2, the optical properties (haze: cloudiness) of the invented products are 10 or less, which is not inferior to commercially available flame-retardant coating sheets, and the adhesion and heat shrinkage rate are better than commercially available products. It turns out that it is also excellent. Furthermore, the tensile strength is greater than that of an untreated film, and various electrical properties are equal to or superior to those of an untreated film. Furthermore, it has sufficient flame retardancy and chemical resistance. Table 3 shows the peeling state of the coating film depending on the baking temperature. In Table 3, ○ represents almost no peeling of the paint film, × represents significant peeling of the paint film, and Δ represents a state where the paint film partially peels off. From Table 3, it can be seen that the baking temperature is 180°C and the baking time is 6 minutes or more.
However, it has been found that when the baking temperature exceeds 230°C, the strength of the base film as a base material decreases significantly. Therefore, exposed to high temperature conditions
When used for applications such as FPCs, adjust the baking time and set the preferable baking temperature to 180 to 230.
It can be judged that it is appropriate to set the temperature at ℃. Table 4 shows the results of an investigation into the suitability of the products of the present invention for use as FPCs or insulating films or sheets. In Table 4, single-sided treated products are those in which a coating layer is formed on one side of the base material and a conductive pattern is formed on the coating layer using copper foil, and double-sided treated products are those in which a coating layer is formed on both sides of the base material. A conductive pattern is formed on the coating layer using copper foil. In addition, untreated PET represents a commercially available FPC that uses PET as a base material, and polyimide represents a commercially available FPC that uses polyimide as a base material. Table 4 shows that the invented product is significantly superior to commercially available FPCs based on polyimide in terms of water absorption. In addition, from Tables 2 and 4, untreated products (based on PET) also have heat resistance and flame retardancy.
It can be seen that there is an improvement compared to . The test method for each item in Tables 2 and 4 is as follows. Adhesion: Cut the coating film in a grid pattern with a razor blade, attach 24mm wide cellophane tape to the above coating film, and visually observe whether the coating film peels off when the cellophane tape is suddenly removed. do. Solvent resistance/chemical resistance: According to JIS C-6481 5.13,
Immerse in each of acetone, MEK, toluene, and trichlene for 5 minutes at room temperature. ○ is a state where there is almost no peeling or dissolution of the paint film, × is a state where peeling or dissolution of the paint film is observed and it comes off when rubbed with a cloth, △
indicates a state in which peeling or dissolution of the coating film is observed, and it partially comes off when rubbed with a cloth. Etching resistance: After immersing in a 10% aqueous solution of FeCl ₃ (ferric chloride) at 40°C for 10 minutes, washing with water, further immersing in a 5% NaOH aqueous solution at 20°C for 15 minutes, and then washing with water. ○ indicates almost no peeling of the paint film,
× indicates a state in which the coating film is significantly peeled off. Flexibility: Conforms to JIS P-8115. ○ means there is almost no peeling of the coating after 200 repeated bending, × means
This shows that the paint film has significantly peeled off after being bent repeatedly 200 times. Solder heat resistance: 5cm of film laminated with copper foil
Cut into 5 cm pieces and immerse in a 230°C solder bath for 30 seconds. ○ represents a state in which there is no melt shrinkage, and × represents a state in which melt shrinkage or coating peeling occurs. Adhesion to copper foil: 180 according to JIS C-6481 5.7
The peel strength was measured. ○ means the peel strength at 10 mm width is 1Kg/ ^cm2 or more, △ means the peel strength at 10 mm width is 500g to 1Kg/ ^cm2 , × means the peel strength at 10mm width is 500g or less . Water absorption rate: According to JIS C-6481 (5.14). The water absorption rate was measured after immersion in water for 24 hours. Flame resistance: Judgment is based on UL-94 VTM method.

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〔Effect of the invention〕

As explained above, the heat-resistant coating sheet of the present invention exhibits sufficient heat resistance and flame retardancy even when PET, PC, and PAL, which are cheaper than highly functional films or sheets, are used as the base material. In addition, it has excellent flexibility, and has excellent adhesion between the coating layer and the base material and etching resistance of the coating layer.
Because it has excellent solvent resistance and shrinkage resistance, it is not only suitable for use as FPCs in manufacturing processes and usage conditions that involve particularly harsh temperature and etching conditions, but also for insulating films or sheets and various other uses. It can also be used for general purposes. In addition, the coating layer has excellent transparency, so from this point of view,
It can be suitably used as an FPC.

[Brief explanation of the drawing]

The figure is a sectional view of a coating sheet according to an embodiment of the present invention. 1...Base material, 2...Coating layer.

Claims (1)

[Claims] 1 (1) A coating layer was formed on one or both sides of a flexible thermoplastic base material by baking and thermosetting a coating film of a solution of a resol type phenolic resin condensate dissolved in a solvent. A heat-resistant film or sheet characterized by: