KR20170016266A - Method for forming coating layers of thermoplastic polyimide - Google Patents

Abstract

The present invention relates to a method for forming a thermoplastic polyimide coating film on a thermosetting polyimide substrate film, and prepares a highly heat resistant polyimide film capable of thermal bonding, by forming a thermoplastic polyimide coating layer on both surfaces of a substrate film such as a thermosetting polyimide film, instead of multi-simultaneously casting a thermosetting polyimide layer and a thermoplastic polyimide layer, thereby providing a highly heat resistant polyimide film, which is more affordable and has high productivity, by preventing a curl generation or twisting phenomenon of the polyimide film while even using a low-cost coating equipment.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for forming a heat-resistant polyimide coating film capable of high-

The present invention relates to a method for producing a heat-resistant polyimide film by coating a thermoplastic polyimide layer on a base film and drying and heat-treating it in a multi-stage system using hot air and infrared rays to produce a film or sheet made of copper or other metal, To a method of forming a thermoplastic polyimide coating film for providing a polyimide film.

A flexible copper clad laminate (FCCL) is a laminated board for a printed circuit board in which a copper foil is adhered to one side or both sides of a heat-resistant plastic film. The core of a flexible circuit board (FPCB) for devices such as a smartphone and a tablet PC Material. Generally, FCCL is manufactured by bonding a copper foil to a polyimide film having excellent heat resistance by bonding a polyimide film or a polyimide film to a copper foil through an adhesive or the like.

The polyimide film has excellent properties in terms of heat resistance, cold resistance, chemical resistance, electrical insulation and mechanical strength and is widely used for an electric insulating film, a heat insulating film, and a base film of a flexible printed wiring board.

FCCL, which uses a polyimide film (PI film) as an insulating support, is a three-layered (Adhesive type) FCCL in which a copper foil is laminated using an adhesive to a polyimide film, and instead of using an adhesive, a thermoplastic polyimide polyimide (TPI) coating layer, and FCCL having a two-layer structure (TPI adhesive type) in which a copper foil is laminated by providing an adhesive property using a coating layer.

However, since the three-layered FCCL using an adhesive is poor in heat resistance, dimensional stability, transparency, and migration resistance, compared with the easy manufacture and handling and low cost, The demand for a two-layered FCCL using a thermoplastic polyimide film is continuously expanding. In the future, the application of the copper foil to the thermoplastic polyimide in the field of small electronic devices such as mobile phones, tablet PCs and electronic books Demand for two-layer FCCL is expected to steadily increase.

FCCL having a two-layer structure using a thermoplastic polyimide film is excellent in heat resistance, dimensional stability, transparency, migration resistance, and flexural fatigue strength, but is not easy to handle and expensive. FCCL having a two-layer structure using a thermoplastic polyimide film is mainly manufactured by a casting method and a laminating method.

The FCCL having a two-layer structure can be produced by a method in which a thermoplastic polyimide film and a copper foil are laminated without a core film (a core film not used) and a polyimide (PI: a non-thermoplastic polyimide) (A core film application type) in which a thermoplastic polyimide film is laminated on a polyimide film to give an adhesive property and then laminated or adhered to a copper foil (a core film application form). In order to ensure dimensional stability against a high modulus, And a polyimide film in which a non-thermoplastic polyimide (PI) film and a thermoplastic polyimide (TPI) film are laminated together for the property of low hygroscopicity and swelling property are widely used.

The thermoplastic polyimide (TPI) layer may be laminated on both sides or cross section of the non-thermoplastic polyimide film. The film in which the thermoplastic polyimide layer is laminated on the non-thermoplastic (thermosetting) polyimide film can be produced by separately preparing the non-thermoplastic polyimide film and the thermoplastic polyimide film, pressing them to laminate them, It is common to produce a laminated polyimide film by co-extruding a thermoplastic polyimide layer on both sides or both sides of the layer. However, since two different types of polyimide films are produced or pneumatically shipped, since the thermoplastic polyimide film layer and the non-thermoplastic polyimide film layer are simultaneously cast using an expensive multilayer simultaneous extrusion molding machine, And the process ratio is high.

On the other hand, since the imidization of the thermoplastic polyimide is carried out at a very high temperature of 200-300 ° C, there is a problem that curling or distortion occurs in the production of the thermoplastic polyimide film.

Precedent literature

Patent Document 1: Japanese Patent Publication No. 4006779

Patent Document 2: US 6746639

Patent Document 3: Japanese Patent Publication No. 2946416

The present invention relates to a method of forming a coating film of a thermoplastic polyimide on a heat-resistant plastic base film such as a thermosetting polyimide, and more particularly, to a method of forming a coating film of a thermoplastic polyimide film on a thermosetting polyimide film, A thermoplastic polyimide coating layer is formed on both sides of a base film such as a mid film to produce a heat resistant and heat-sealable polyimide film, thereby preventing curling and distortion of the polyimide film while using low-cost coating equipment, And to provide a high heat-resistant polyimide film having high productivity.

The present invention relates to a method of forming a polyimide coating film capable of high temperature thermal fusion bonding on a heat resistant base film, and more particularly, to a method for forming a polyimide coating film on a heat resistant base film by coating a substrate film using a liquid thermoplastic polyimide precursor or an imidized thermoplastic polyimide varnish, And drying and heat treatment in a multistage process to imidize.

At this time, it is preferable to use a thermosetting (non-thermoplastic) polyimide film as the heat-resistant base film. In order to prevent curling due to shrinkage of the coating film upon coating the thermoplastic polyimide on the base film, And then a tension of 5 to 50 N is required after coating the thermoplastic polyimide on one surface of the substrate. The coated substrate is dried at a temperature of 80 to 120 ° C at a low temperature to maintain the tackiness of the coating film, Treating the opposite surface by the same method, drying at a low temperature, drying at a temperature of 120-200 ° C at a middle temperature, and then performing a high-temperature heat treatment at 200-300 ° C again.

In the drying and heat treatment method, hot air is used for low-temperature drying and mid-temperature drying, and infrared light is used for high-temperature heat treatment.

Further, the present invention further includes a step of defoaming the thermoplastic polyimide precursor or varnish before coating, so that the thermoplastic polyimide free from defects on the surface of the film without curling or twisting of the polyimide film, Heat-resistant thermally fusible polyimide film coated thereon. The defoaming step can be done in-line using centrifugal force to secure mass productivity.

  The present invention preferably coating the thermoplastic polyimide precursor or varnish on a substrate film such as a thermosetting polyimide film by a slot die or a comma coating method. In this case, the viscosity of the thermoplastic polyimide varnish is preferably 1,000 to 15,000 cps, more preferably 8,000 to 10,000 cps, and a solid content of 14 to 20%.

As a preferred embodiment of the present invention, the drying time of the thermoplastic polyimide layer coated on the base film is from 1 to 10 minutes, and the base film coated with the thermoplastic polyimide is a multi-step The drying furnace and the heat treatment furnace at a speed of 1-20 m / min.

According to the present invention, the thermoplastic polyimide coating layer on the thermosetting polyimide base film is coated so as to have a final dry thickness of 2-50 탆, more preferably 3-30 탆, and the thermoplastic polyimide coating layer is coated with the copper foil It is preferable to heat-laminate so that the peel strength is 1.2 kgf / cm or more.

In the production of a high heat-resistant thermally fusible polyimide film in which a thermoplastic polyimide layer is laminated on both sides of a thermosetting polyimide base film, conventionally, an expensive multi-simultaneous casting equipment has been used to produce a thermoplastic polyimide layer, Since the three layers of mid-film and thermoplastic polyimide are cast simultaneously, equipment investment and process ratio are high. However, according to the present invention, since the thermoplastic polyimide layer is coated on both sides of the non-thermoplastic polyimide film using low-cost coating equipment, the equipment investment ratio and the process ratio are relatively low, Heat-sealable polyimide film having the same adhesive force as that of the polyimide film product produced by co-extrusion can be obtained.

FIG. 1 is a graph showing a change in heat of a thermoplastic polyimide coating film after coating a thermoplastic polyimide film on a thermosetting polyimide film layer by drying according to the present invention. The glass transition temperature of the coating film is generally 240-300 ° C. / RTI >
FIG. 2 is a graph showing a change in mass of a thermoplastic polyimide coating film after the coating of the thermoplastic polyimide film layer on the thermoplastic polyimide film layer by the method of the present invention. The thermally decomposable polyimide film was dried at about 590 ° C. to 670 ° C. do.
3 is a sectional scanning electron microscope (SEM) photograph of a thermoplastic polyimide layer and a base polyimide film immediately after coating and drying the thermoplastic polyimide on both sides of the thermosetting polyimide film by the manufacturing method according to the present invention.
Fig. 4 is a SEM photograph of the surface of the thermoplastic polyimide coating film after peeling the laminated specimen with the copper foil. Fig. 4 (a) shows a case in which the drying is insufficient and the adhesive force is low, and Fig. 4 .

To prepare a high heat-resistant thermally fusible polyimide film having a thermoplastic polyimide layer coated on both sides of a thermosetting polyimide base film, N-methyl-2-pyrrolidone (NMP) , dimethylacetamide A thermoplastic polyimide precursor (polyamic acid) which is a liquid coating solution using N, N-dimethylacetamide (DMAc), dimethylformamide (DMF) or methyl benzoate as a main solvent, or an imidized oligomer A thermoplastic polyimide varnish (viscosity of 1,000 to 15,000 cps, solid content of 14 to 20%) is prepared.

The prepared liquid thermoplastic polyimide precursor or varnish is applied to a thermosetting polyimide base film by a slot die or a comma Was coated so that the final dry thickness of 2 ~ 50㎛ by coating, by low-temperature drying 80 ~ 120 ^o C, multi-stage drying temperature range in the range of medium temperature drying 120 ~ 200 ^o C, and the high-temperature drying 200 ~ 300 ^o C The respective drying times are set to 1 to 10 minutes, and the peel strength in the case of thermal lamination with the copper foil is adjusted to be 1.2 kgf / cm or more.

In this case, the liquid thermoplastic polyimide precursor or varnish is first coated on one side of the thermosetting polyimide film, and then, in order to minimize curl due to shrinkage of the coating layer during drying, the film is subjected to a tension of 5 to 50 N ), The thermosetting polyimide varnish was coated on the opposite side of the thermosetting polyimide film immediately after the first low-temperature drying to such an extent that the tackiness was eliminated, and the stress due to the contraction of the varnish coating layer was measured Should be offset.

The inventor of the present invention has also found that the fish eye phenomenon occurring in the coating layer after coating the thermoplastic polyimide varnish is mainly caused by bubbles or foreign particles contained in the varnish, It is necessary to subject the thermoplastic polyimide varnish to defoaming and filtering before coating. In the defoaming step, it is preferable to use an inline defoaming device using centrifugal force instead of a vacuum method in order to secure mass productivity, and it is preferable that the filter has a filtering ability of 1 to 50 mu m.

The occurrence of streaks in the slot die coating is caused by the presence of external foreign matter or a thermoplastic polyimide Since the gel lump or foreign particle is a phenomenon caused by blocking the discharge portion of the slot die, the cleanliness of the coating portion is maintained at 500 class, and the transfer line of the thermoplastic polyimide varnish It is necessary to filter at least one foreign object in the middle.

A specific embodiment of the present invention will be described below in each step.

- Step 1: Extraction of base film

- Step 2: Corona and antistatic treatment

- Step 3: Varnish Inline Tubbing

- Step 4: Supply the varnish to the slot die or comma knife through the filter inserted line.

- Step 5: Cross-section varnish coating

- Step 6: 80 ~ 120 ^o C low temperature drying

- Step 7: Reverse side varnish coating

- Step 8 : 120 ~ 200 ^o C with hot air drying

- Step 9: NIR method 200 ~ 300 ^o C high temperature drying

- Step 10 : Inspection of foreign substances and air bubbles in the cured coating film

- Step 11 : Treatment of coating dried film with antistatic agent

- Step 12 : Coated film winding

- Step 13 : Thickness measurement, thermal analysis (DSC, TGA)

- Step 14 : Copper foil and thermal lamination

- Step 15 : peel strength test

- Step 16 : Test for solder bath dipping

A thermoplastic polyimide varnish having a viscosity of 1,000 to 15,000 cps and a solid content of 14 to 20% was prepared. When the viscosity was low in a heat agitator, it was heated to 40 to 60 ^° C at room temperature and high viscosity, (Slot die or comma). The bubbles and the foreign particles contained in the thermoplastic polyimide varnish were removed using an inline de-aerator and a filter, and a non-thermoplastic polyimide film having a thickness of 12.5 to 125 탆 was formed on one surface of the slot die Or the gauge of the comma knife is adjusted to adjust the wet thickness to coat the thermoplastic polyimide.

The non-thermoplastic polyimide film coated with the thermoplastic polyimide varnish is passed through a multistage drying furnace of a roll support or floating type at a speed of 1 to 20 m / min, and firstly, it is dried in a first stage at 80 to 120 ^° C in a hot- It removes more than half of the solvent of the coating film of Meade and removes the stickiness of the coating film.

In this state, another side of the non-thermoplastic polyimide film is coated by adjusting the discharge amount of the slot die or the gauge of the comma knife so that the final dry thickness of the thermoplastic polyimide is 2 to 50 μm by the same method.

In the second step, drying is carried out at 120 to 200 ^° C. in a hot air mode, and the remaining solvent is completely blown away, and at the same time, imidization reaction is caused. In the third step, the imidization reaction is completed by drying at 200 to 300 ^° C., A polyimide film coated with thermoplastic polyimide on both sides is wound around a 3 "or 6" diameter branch tube.

The thickness of the thermoplastic polyimide coating film was measured with a dial gauge or a scanning electron microscope by peeling a sample of a proper size from the coated and dried film, and using DSC and TGA for thermal analysis, And mass changes were measured and are shown in Figs. 1 and 2.

Immediately after drying, the cross section of the coating film and the surface after peeling were observed with a scanning electron microscope (Figs. 3 and 4)

Silicone-treated copper foil and thermal lamination (post-curing, post-curing) and heat lamination (treatment at a glass transition temperature of 240 to 300 ^° C and a pressure of 20 to 40 kgf / cm ² for 1 to 20 minutes) The peel strength of one specimen was measured by UTM as shown in Table 1 below.

Table 1 . The peel strength (thermoplastic polyimide layer thickness: 5 to 7 占 퐉, copper foil thickness: 18 占 퐉) measured by UTM after heat-lamination of the post-cured thermoplastic polyimide-

Silane-bonded copper foil and thermally laminated specimens were immersed in a solder bath at 280-320 ^° C for 60 seconds. The results showed no swelling or peeling, which proved sufficient heat resistance.

Claims (11)

A method of forming a heat resistant polyimide coating film capable of high temperature thermal fusion bonding, comprising the steps of coating a substrate film using a liquid thermoplastic polyimide precursor or an imidized oligomeric thermoplastic polyimide varnish, drying and heat treating in a multi- , ≪ / RTI &
Coating the thermoplastic polyimide on one surface of the substrate film to prevent curling due to shrinkage of the formed coating film;
The method comprising, while maintaining the tension of 5-50N in the base film, the low temperature dry enough to eliminate the stickiness of the coating film formed at a temperature of 80-120 ^o C;
Coating the thermoplastic polyimide on the opposite side of the base film immediately after the low temperature drying;
Drying the coating film formed on both sides at a temperature of 120-200 ^° C at a low temperature; And
And drying the coating film on both sides at a temperature of 200-300 ^° C again,
Further comprising defoaming the thermoplastic polyimide precursor or the varnish prior to coating the thermoplastic polyimide precursor or varnish on the substrate film. ≪ RTI ID = 0.0 > 11. < / RTI > The method for forming a heat-resistant polyimide coating film according to claim 1, wherein the base film is a non-thermoplastic polyimide film. The method for forming a heat resistant polyimide coating film according to claim 1, wherein the thermoplastic polyimide precursor or varnish is coated on the base film by a slot die or a comma coating method. The method according to claim 1, wherein the defoaming step is an in-line method using centrifugal force. The method for forming a polyimide coating film according to claim 1, wherein the low-temperature drying and the mesophilic drying are performed using hot air, and the high-temperature drying is performed using infrared light. The method according to claim 1, wherein the thermoplastic polyimide varnish has a viscosity of 1,000 to 15,000 cps and a solid content of 14 to 20%. The method for forming a heat resistant polyimide coating film according to claim 1, wherein the drying time for each temperature section is 1-10 minutes. The method according to any one of claims 1 to 7, wherein the base film on which the thermoplastic polyimide coating film is formed is passed through a multi-stage drying furnace of a roll support or floating type at a speed of 1-20 m / A method for forming a polyimide coating film having heat resistance. The method for forming a heat resistant polyimide coating film according to claim 1, wherein the thermoplastic polyimide coating layer is coated so as to have a final dry thickness of 3-30 占 퐉. The method according to claim 1, wherein the thermoplastic polyimide coating film has a peel strength of 1.2 kgf / cm or more by thermal lamination with a copper foil after drying, so that the heat-resistant polyimide coating film is formed. The thermoplastic polyimide precursor as claimed in claim 1, wherein a polyimide polymer in a gel state and a filter for removing foreign substances are inserted in the middle of the transfer line during the transfer of the thermoplastic polyimide precursor or varnish for coating. A method for forming a polyimide coating film.

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