JPH0587377B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a polyimide film known as a heat-resistant plastic film, and more specifically, it provides a polyimide film that has a small heat shrinkage rate and is excellent in isotropy. Polyimide film has a high degree of heat resistance, cold resistance, chemical resistance, electrical insulation, mechanical strength, and other excellent properties, so it is used as an electrical insulation film.
It is extremely useful and widely used in various applications, including electric wire coating tape. (Prior Art and Problems) Polyimide films have conventionally been used for flexible printed circuit boards and the like by laminating them with copper foil. Particularly in recent years, the need for fine pattern processing has been increasing in accordance with market demands such as weight reduction of electronic components. For these reasons, operations such as heating during the flexible printed circuit board manufacturing process cause shrinkage of the polyimide film, resulting in problems such as misalignment of the fine pattern. Furthermore, when used as a base film for high-density magnetic recording, processes that generate high heat such as sputtering and vacuum deposition are required, and an even higher degree of heating dimensional stability is required. In response to such market demands, current polyimide films are
The disadvantage is that the dimensional shrinkage rate during heating in the width direction (TD direction) exhibits anisotropy, and the absolute amount thereof is as large as 0.1 to 0.2%. (Means for Solving the Problems) As a result of intensive studies to overcome these drawbacks, the present inventors have reduced the heating shrinkage rate to 0.1% or less, more preferably 0.05% or less, and achieved good heating. The present invention was achieved by discovering a film processing method for obtaining a polyimide film having dimensional stability and isotropy. That is, the polyimide film is heated under substantially no tension, preferably at a temperature of 150°C or higher and 420°C or lower, more preferably at a temperature of 200°C or higher and 400°C or lower.
That is, as will be described later, the temperature range is one that allows the molecules constituting the polyimide film to move and does not cause thermal deterioration, for 1 second to 60 hours, preferably 10 hours.
It has been found that heating shrinkage rate can be reduced to 0.1% or less by heating for more than 10 seconds or more and less than 10 hours, and then cooling to room temperature. At the same time, the anisotropy can be greatly improved. A polyimide film with improved stability was successfully obtained. By heating the polyimide film under substantially no tension, the molecules constituting the polyimide film are allowed to move freely, and the distortion in the mutual arrangement of the molecules is corrected.
The subsequent cooling under substantially tension-free conditions fixes and achieves a relatively stable molecular alignment state. This is thought to be due to the effect of improving the thermal dimensional stability of the polyimide film. Although it is generally said that such an effect cannot be expected with a low-crystalline polymer film such as polyimide film, the present inventors focused on the slight molecular orientation of the polyimide film, and found that it has virtually no effect. The present invention was arrived at by discovering processing under tension. Furthermore, if this heat treatment is carried out in air, that is, in the presence of oxygen, the polyimide film may be slightly colored, as will be described in the Examples section below. This is thought to be due to the polyimide film being deteriorated by oxidation. It has been confirmed that such a phenomenon can be prevented by performing the treatment in the presence of an inert gas such as nitrogen, that is, in a substantially oxygen-free condition. To sum up the above explanation, the present invention provides a method for heating a polyimide film under substantially no tension, and then
A cooling process is applied to improve the heating dimensional stability and anisotropy of the polyimide film, resulting in a polyimide film that is extremely useful as an electronic material, such as a base film for microfabricated patterns or a base film for high-density magnetic recording. This provides industrial advantage. The present invention will be explained in more detail. The specific method of heating and then cooling used in the present invention is a batch method in which the film is processed in a heating oven in the form of a roll, or a continuous method equipped with an unwinding and winding machine. Any method of continuously processing the film in a heating furnace, ie, a continuous method, can be adopted. The polyimide film used as a raw material in the present invention is a polyimide film obtained by polycondensation of aromatic tetracarboxylic dianhydride and aromatic diamine, and the present invention can be applied to polyimide films of any thickness. However, it is preferably applicable to a film having a nominal thickness of 7.0 μm or more and 125 μm or less. Furthermore, especially for thin polyimide films of 40μ or less, by taking measures such as loosening the winding tension, the above treatment can be applied without wrinkles even in the batch method. A polyimide film having good heating dimensional stability and improved anisotropy is obtained. (Example) Next, an example of the present invention will be shown. However, the present invention
The present invention is not limited to the following examples. Furthermore, in each of the following examples, evaluation measurements of heating dimensional stability, that is, heating shrinkage rate, were carried out as follows. Evaluation and measurement method of heat shrinkage rate Evaluation and measurement were performed according to the heat shrinkage rate test method of JIS-C-2318 (1975) electrical polyester film section 6.3.5. However, the length is measured using a continuing microscope, and 1/
Measured with an accuracy of 1000mm. Regarding the test temperature and time, what is written as 150℃±3℃ is 200℃±3℃×2 hours or 300℃±3℃×
Evaluation measurements were carried out after changing the duration to 30 minutes. Reference Example 1 Approximately equal moles of pyromellitic acid dianhydride and 4,4'-diaminodiphenyl ether were reacted in N,N-dimethylacetamide to obtain a polyamic acid solution. Thereafter, the polyamic acid solution was converted into polyimide using a continuous film forming device and simultaneously dried and solidified to form a polyimide film, which was wound up using a continuous winding device to form a film with a nominal thickness of 25 μm and a width of 1016 mm.
A polyimide film roll with a length of 1500 m was obtained. Reference example 2 Same as reference example 1, nominal thickness 75μ and 1016mm
A roll of polyimide film with a width and length of 1500m was created. Examples 1 and 2 The polyimide film roll obtained in Reference Example 1 or Reference Example 2 was placed in a heating oven adjusted to a predetermined temperature, and after being left for a predetermined time, the heating was stopped and the temperature was raised to room temperature over about 10 hours. After slowly cooling to , it was taken out from the heated oven. Examples 3, 4, and 5 The treatment shown in Examples 1 and 2, in which the heating oven in Examples 1 and 2 was a heating oven filled with nitrogen gas, was performed. Examples 6, 7, 8, 9, 10 Using the continuous heating furnace shown in Figure 1, Reference Example 1
Alternatively, the polyimide film obtained in Reference Example 2 was continuously processed at a predetermined temperature and a predetermined line speed shown in Table 1. Table 1 shows the results of measuring the heat shrinkage rate of the films treated in the above examples.

[Table] (Effects of the Invention) As shown in the examples, the polyimide film of the present invention exhibits the effect that the heat shrinkage rate is greatly reduced and its anisotropy is also greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a continuous heating furnace in which the polyimide film of the present invention is continuously produced. 1... Heating furnace, 2... Rod heater, 3... Unwinding machine,
4... Winder, 5... Cooling fan, 6... Exhaust duct.

Claims (1)

[Claims] 1. A material with improved heat shrinkability obtained by heating at 150°C or more and 420°C or less for 1 second or more and less than 60 hours under substantially no tension, and then cooling to room temperature. polyimide film. 2 Claim 1 whose thickness is 7.0 to 125μ
Polyimide film as described in Section. 3. The polyimide film according to claim 1, wherein the heating is performed in a substantially oxygen-free atmosphere. 4. The polyimide film according to claim 1, wherein the shrinkage length in all directions on the film surface after being left at 200°C for 2 hours is 0.1% or less of the length before being left. 5. The polyimide film according to claim 1, wherein the shrinkage length in all directions on the film surface after being left at 300°C for 30 minutes is 1.00% or less of the length before being left.