JP7803277B2 - Resin film manufacturing method and pre-cut film - Google Patents

Description

The present invention relates to a method for manufacturing a resin film and a pre-cut film.

Conventionally, in the film manufacturing process, a tenter-type conveying device has been known that grips both ends of the film widthwise with a number of pins or clips when conveying, drying, heat-treating, etc. the film, applying tension to the film widthwise while conveying it (see, for example, Patent Document 1).

There are several tenter-type conveying devices. Among these, pin tenter-type conveying devices, which grip the film by inserting multiple pins into both ends of the film along the machine direction, have multiple pins arranged on a pin seat supported by a pair of parallel moving chains. This pin tenter-type conveying device faces challenges, such as the possibility that holes formed in the film by the pins may tear into elongated holes across the film's width when the film's shrinkage force (tensile force) increases. If holes tear, the film cannot maintain its proper tension, resulting in wrinkles and other degradation of quality. Consequently, tearing of the holes causes production losses and reduced production efficiency. Clip tenter-type conveying devices, which grip both ends with clips, also face the same challenges as pin tenter-type conveying devices, such as film tearing at the clip-clamped areas.

Resin films characterized by a low coefficient of linear thermal expansion (CTE), which has become increasingly popular in recent years, tend to have low tear strength because their molecular chains are rigid, making them less likely to entangle with each other and more brittle. One area in which a low CTE is particularly strongly required is in the field of glass replacement, such as display substrate materials. However, since it is difficult to meet the required physical properties using resin materials alone, the introduction of fillers such as silica has been proposed (see Patent Document 2). Resin films containing such fillers have even lower tear strength, making the problem of tearing in the supported areas more pronounced.

To solve this problem, it has been proposed to overlap the gripping portion (edge) of a film with low tear strength with a film with high tear strength as a reinforcing film (see Patent Document 3). It has also been proposed that when conveying a sheet, the pin arrangement density at both ends of the sheet be greater on the inside in the width direction than on the outside (see Patent Document 4).

Special Publication No. 39-29211 WO2013/161970 publication Japanese Patent Application Publication No. 11-254521 Japanese Patent Application Publication No. 9-77315

However, the method of Patent Document 3 involves overlaying a film with low tear strength on a film with high tear strength, which results in a problem of wasting a lot of raw material. That is, the gripping portion is a portion that will eventually be slit and discarded after transportation, and if this gripping portion has a two-layer structure, there is a problem of a large portion that will be discarded.
Furthermore, the method of Patent Document 4 cannot be used with resin films containing fillers with even lower tear strength, resin films characterized by a low CTE, etc., and there is a problem in that holes formed in the film may tear when pierced with a pin.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a method for manufacturing a resin film and a pre-cut film that can more effectively prevent film tearing when both ends of the film are gripped by a tenter-type conveying device.

The inventors conducted extensive research into methods for producing resin films characterized by a low CTE, and into pre-cut films. As a result, they discovered that by adopting the following configuration, it is possible to more effectively prevent film tearing when both ends of the film are gripped by a tenter-type conveying device, leading to the completion of the present invention.

That is, the method for producing a resin film according to the present invention is as follows:
Step A: applying a first resin composition solution to a central portion of a support;
Step B: applying a second resin composition solution to both end portions adjacent to the central portion;
A step C of drying the first resin composition solution and the second resin composition solution to obtain a pre-cut film;
Step D: peeling the pre-cut film from the support;
a step E of holding both end portions of the pre-cut film by a tenter-type conveying device after the step D;
a step F of conveying the uncut film while holding both end portions of the uncut film; and
After the step F, a step G is performed in which a portion formed from the second resin composition solution is removed from the pre-cut film to obtain a resin film.
and
the first resin composition solution contains a first resin and a filler, and the content of the filler is 0.1% by mass or more and 50% by mass or less with respect to the first resin;
the second resin composition solution contains a second resin and does not contain a filler, or if it contains a filler, the content of the filler is less than that of the first resin composition solution and is 2 mass% or less relative to the second resin;
After step C and before step F, the pre-cut film is characterized in that the tear strength of the portion formed from the second resin composition solution is greater than the tear strength of the portion formed from the first resin composition solution.

According to the above configuration, a first resin composition solution is applied to the center of a support (step A), a second resin composition solution is applied to both end portions (step B), and the first and second resin composition solutions are dried to obtain a pre-cut film (step C). Both end portions of the pre-cut film obtained in this manner are formed solely from the second resin composition solution. Here, the tear strength of the portion formed solely from the second resin composition solution is greater than the tear strength of the portion formed from the first resin composition solution. Therefore, even if the pre-cut film is transported while both end portions are gripped by a tenter-type transport device (step F), tearing is unlikely to occur at the gripped portions (both end portions).
Furthermore, according to the above configuration, after step F, the portion formed from the second resin composition solution is removed from the pre-cut film to obtain a resin film (step G). This method allows even resin films with low tear strength to be transported using a conventionally known tenter-type transport device. Furthermore, because both end portions of the pre-cut film are formed only from the second resin composition solution, it is possible to minimize waste of raw materials associated with the portions removed in step G.

The resin film obtained in the step G preferably has a CTE of 5 ppm/K or more and 50 ppm/K or less.
According to the above-mentioned configuration, the CTE of the resin film is within a predetermined range, and therefore the heat resistance is excellent.

In the above configuration, it is preferable that step E is a step of gripping both ends of the pre-cut film with pins of a pin tenter-type conveying device.

Since the tear strength of the portion of the pre-cut film formed from the first resin composition solution is greater than the tear strength of the portion formed from the second resin composition solution, tearing by the pins of a pin tenter-type conveying device is more effectively prevented.

The present invention can be applied to all resin films that can be solution-formed. Solution film formation can be applied to all resins in which the resin or resin precursor dissolves in a solvent, but from an industrial standpoint, it is preferably applied to resins that are difficult to form into a film by melting, such as cellulose triacetate, aromatic polyamide, polyimide, polyetherimide, polyamideimide, polyesterimide, polybenzoxazole, polybenzimidazole, and polybenzothiazole. Of these, polyimide-based resins such as polyimide, polyamideimide, polyetherimide, and polyimidebenzoxazole are particularly suitable.

In the above configuration, it is preferable that the support is a polymer film.

In the above configuration, it is preferable that the filler is silica.

In recent years, there has been high demand for colorless, transparent, and low CTE polyimide-based resin films, but these polyimide-based resin films tend to have low tear strength. Furthermore, the introduction of fillers has been considered to achieve both transparency and a low CTE, which further reduces tear strength. Therefore, the above-described configuration makes it possible to obtain polyimide-based resin films with particularly low tear strength.

Further, the pre-cut film according to the present invention is
The center and
and two end portions formed continuously from the central portion at both ends of the central portion,
the central portion is composed of a first resin composition containing a first resin and a filler, and a content of the filler is 0.1% by mass or more and 50% by mass or less with respect to the first resin;
the two end portions are made of a second resin composition containing a second resin, and the second resin composition does not contain a filler, or even if it contains a filler, the content of the filler is less than that of the first resin composition and is 2 mass % or less relative to the second resin;
The tear strength at both ends is greater than the tear strength at the center.

According to the above configuration, the tear strength of both ends is greater than the tear strength of the central portion, so even if the pre-cut film is transported while both ends are gripped by a tenter-type transport device, tearing is unlikely to occur at the gripped portions (both ends).
Furthermore, since both ends of the film before cutting are composed only of the second resin composition, when removing both ends to obtain a resin film, it is possible to minimize waste of raw materials related to the removed parts.

In the above configuration, it is preferable that the first resin is a polyimide resin.

If the first resin is a polyimide-based resin, removing both ends after transporting it using a tenter-type transport device makes it possible to obtain a polyimide-based resin film with low tear strength.

It is preferable that the CTE of the central portion is 5 ppm/K or more and 50 ppm/K or less. According to the above configuration, by removing both end portions, a resin film with a CTE of 5 ppm/K or more and 50 ppm/K or less can be obtained.

In the above configuration, it is preferable that the filler is silica.

The present invention provides a method for manufacturing a resin film and a pre-cut film that can more effectively prevent film tearing when both ends of the film are gripped by a tenter-type conveying device.

FIG. 2 is a side cross-sectional view illustrating a method for applying a resin composition solution according to the first embodiment. FIG. 2 is a plan view of FIG. 1; 3 is a partially enlarged plan view of the vicinity of a side plate 18b shown in FIG. 2. FIG. FIG. 10 is a cross-sectional view showing a case where each coating film is connected only at the side surface. FIG. 10 is a cross-sectional view showing a case where the coating film 64a and the coating film 64c slightly overlap on the coating film 64b. FIG. 10 is a cross-sectional view showing a case where the coating film 64b slightly overlaps the coating films 64a and 64c. FIG. 10 is a side cross-sectional view illustrating a method for applying a resin composition solution according to a second embodiment. FIG. 8 is a plan view of FIG. 7. FIG. 10 is a side cross-sectional view illustrating a method for applying a resin composition solution according to a third embodiment. FIG. 10 is a plan view of FIG. 9 . This is a cross-sectional view showing a case where the end of the coating film 64a slightly overlaps the coating film 64b, and the end of the coating film 64b slightly overlaps the coating film 64c. FIG. 10 is a side cross-sectional view illustrating a method for applying a resin composition solution according to a fourth embodiment. FIG. 13 is a plan view of FIG. 12.

The following describes an embodiment of the present invention.

[Method of manufacturing resin film]
The method for producing a resin film according to this embodiment includes the steps of:
Step A: applying a first resin composition solution to a central portion of a support;
Step B: applying a second resin composition solution to both end portions adjacent to the central portion;
A step C of drying the first resin composition solution and the second resin composition solution to obtain a pre-cut film;
a step D of peeling the pre-cut film from the support; and a step E of holding both ends of the pre-cut film with a tenter-type conveying device after the step D.
a step F of conveying the uncut film while holding both end portions of the uncut film; and
After the step F, a step G is performed in which a portion formed from the second resin composition solution is removed from the pre-cut film to obtain a resin film.
and
the first resin composition solution contains a first resin and a filler, and the content of the filler is 0.1% by mass or more and 50% by mass or less with respect to the first resin;
the second resin composition solution contains a second resin and does not contain a filler, or if it contains a filler, the content of the filler is less than that of the first resin composition solution and is 2 mass% or less relative to the second resin;
After step C and before step F, the pre-cut film is characterized in that the tear strength of the portion formed from the second resin composition solution is greater than the tear strength of the portion formed from the first resin composition solution.

<Process A, process B>
In the method for producing a resin film according to this embodiment, first, a first resin composition solution is applied to a central portion of a support (Step A). Then, a second resin composition solution is applied to both end portions adjacent to the central portion (Step B). Steps A and B may be performed simultaneously, or Step B may be performed after Step A, or Step A may be performed after Step B.

The support is not particularly limited, but is preferably one that is resistant to the solvents in the first resin composition solution and the second resin composition solution. Examples include polymer films made of resins such as PET (polyethylene terephthalate), PI (polyimide), and PAI (polyamideimide), metal drums, and endless steel belts. Of these, polymer films are preferred.

The coating methods for steps A and B are not particularly limited, and examples include comma coating, T-die coating, spin coating, spray coating, bar coating, knife coating, and dipping. Two of these methods may be combined. Comma coating, T-die coating, or a combination of these is preferred from the standpoint of productivity.

Specific examples of steps A and B are explained below.

[First embodiment]
FIG. 1 is a side cross-sectional view for explaining the method for applying a resin composition solution according to the first embodiment, and FIG. 2 is a plan view thereof.
As shown in FIGS. 1 and 2, the coating device 10 has a backup roll 12, a comma roll 14, and three coating liquid storage sections 16 (16a, 16b, 16c).
The coating liquid storage section 16 (16a, 16b, 16c) has four side plates 18 (18a, 18b, 18c, 18d) for dividing the coating liquid storage section 16, and a back plate 20. The coating liquid storage section 16 (16a, 16b, 16c) is capable of storing the coating liquid 62 in an area surrounded by the back plate 20 and the side plates 18.

Of the three coating liquid storage sections 16 (16a, 16b, 16c), the coating liquid storage sections 16a and 16c located at both ends store second resin composition solutions 62a and 62c, while the central coating liquid storage section 16b stores the first resin composition solution 62b.

The backup roll 12 continuously transports the support 60 by rotating. The support 60 transported by the backup roll 12 passes through the gap 22 formed between the backup roll 12 and the comma roll 14. As the support 60 passes through the gap 22, the coating liquid 62 (second resin composition solution 62a, 62c, first resin composition solution 62b) is supplied from the coating liquid reservoir 16 onto the support 60, forming a coating film 64 (64a, 64b, 64c). Specifically, the coating film 64 is formed to a thickness equivalent to the gap 22 minus the thickness of the support 60.

The thickness of the coating film 64 can be controlled by, for example, the gap 22 between the backup roll 12 and the comma roll 14.

FIG. 3 is an enlarged plan view of a portion near the side plate 18b shown in FIG.
Each coating liquid 62 (second resin composition solutions 62a, 62c, first resin composition solution 62b) spreads in the width direction after being coated on the support 60. Specifically, as shown in FIG. 3, the second resin composition solution 62a coated near the side plate 18b spreads inward in the width direction (to the right in FIGS. 2 and 3). On the other hand, the first resin composition solution 62b coated near the side plate 18b spreads outward in the width direction (to the left in FIGS. 2 and 3). Then, the second resin composition solution 62a (coating film 64a) and the first resin composition solution 62b (coating film 64b) are connected at a location where the side plate 18b disappears in the flow direction (upper side in FIGS. 2 and 3).
Similarly, the first resin composition solution 62b applied near the side plate 18c spreads outward in the width direction (to the right in FIG. 2). Meanwhile, the second resin composition solution 62c applied near the side plate 18c spreads inward in the width direction (to the left in FIG. 2). Then, the first resin composition solution 62b (coating film 64b) and the second resin composition solution 62c (coating film 64c) are connected at the point where the side plate 18c disappears in the flow direction.
As a result, the coating film 64 a and the coating film 64 b are connected to each other, and the coating film 64 b and the coating film 64 c are also connected to each other. Examples of the connection include connection due to compatibility between the resin composition solutions constituting each coating film 64, and connection due to adhesive force at the interface between each coating film 64.

The connection mode of each coating film 64 is not particularly limited, but examples include when each coating film is connected only on the side (see Figure 4) or when one coating film slightly overlaps the other coating film (see Figures 5 and 6).

FIG. 4 is a cross-sectional view showing a case where the coating films are connected only at the side surfaces.
In the example shown in FIG. 4 , the coating film 64a and the coating film 64b are connected only at their sides. Furthermore, the coating film 64b and the coating film 64c are connected only at their sides. Immediately after coating, they are connected only at their sides, but by the time of the subsequent step C, the second resin composition solution 62a (coating film 64a) and the first resin composition solution 62b (coating film 64b), or the first resin composition solution 62b (coating film 64b) and the second resin composition solution 62c (coating film 64c), are mixed together to form a compositionally gradient region. The width of the compositionally gradient region is preferably in the range of 10 to 2500 times the thickness of the portion of the coating film 64b that is not the compositionally gradient region. It is more preferably 100 to 1000 times, and even more preferably 250 to 500 times. For example, when the thickness of the coating film 64b is 20 μm, the width of the composition gradient region is preferably 0.2 mm (10 times the thickness of the coating film 64b) to 5 cm (2500 times the thickness of the coating film 64b).Within this range, fracture from the composition gradient region during manufacturing is unlikely to occur.

FIG. 5 is a cross-sectional view showing a case where the coating film 64a and the coating film 64c slightly overlap on the coating film 64b.
In the example shown in FIG. 5 , the edge of the coating film 64a slightly overlaps the edge of the coating film 64b. Furthermore, the edge of the coating film 64c slightly overlaps the edge of the coating film 64b. The overlapping portions create a compositionally gradient region by mixing the second resin composition solution 62a (coating film 64a) with the first resin composition solution 62b (coating film 64b), or the first resin composition solution 62b (coating film 64b) with the second resin composition solution 62c (coating film 64c). The width of the compositionally gradient region is preferably in the range of 10 to 2500 times the thickness of the portion of the coating film 64b that is not the compositionally gradient region. It is more preferably 100 to 1000 times, and even more preferably 250 to 500 times. For example, when the thickness of the coating film 64b is 20 μm, the width of the compositionally gradient region is preferably 0.2 mm (10 times the thickness of the coating film 64b) to 5 cm (2500 times the thickness of the coating film 64b). Within this range, fracture from the composition gradient region is unlikely to occur during manufacturing.

FIG. 6 is a cross-sectional view showing a case where the coating film 64b slightly overlaps the coating films 64a and 64c.
In the example shown in Figure 6, the end of coating film 64b (the end on the left in Figure 6) slightly overlaps coating film 64a. Also, the end of coating film 64b (the end on the right in Figure 6) slightly overlaps coating film 64c. As in the case of Figure 5, the width of the overlapping portion is preferably in the range of 10 to 2500 times the width of the coating film 64b in the portion that is not the compositionally graded region. More preferably, it is 100 to 1000 times, and even more preferably, it is 250 to 500 times. Within this range, fracture from the compositionally graded region is less likely to occur during manufacturing.

The connection mode can be determined, for example, by the gap 22. If the gap 22 through which the second resin composition solutions 62a and 62c pass is the same as the gap 22 through which the first resin composition solution 62b passes, the connection mode shown in Figure 4 is likely to be achieved. If the gap 22 through which the second resin composition solutions 62a and 62c pass is slightly wider than the gap 22 through which the first resin composition solution 62b passes, the connection mode shown in Figure 5 is likely to be achieved. If the gap 22 through which the first resin composition solution 62b passes is slightly wider than the gap 22 through which the second resin composition solutions 62a and 62c pass, the connection mode shown in Figure 6 is likely to be achieved. Note that the connection mode can be controlled not only by the gap 22, but also by the viscosity of the first resin composition solution 62b and the second resin composition solutions 62a and 62c, and the width of the side plate 18.

In the first embodiment, steps A and B are performed simultaneously using the application device 10 described above.

The above describes process A and process B related to the first embodiment.

Second Embodiment
Fig. 7 is a side cross-sectional view for explaining the method for applying a resin composition solution according to the second embodiment, and Fig. 8 is a plan view thereof. In the application device 30 of the second embodiment, components common to the application device 10 of the first embodiment are designated by the same reference numerals, and descriptions thereof will be omitted or simplified.

As shown in Figures 7 and 8, the coating device 30 has a backup roll 12, a comma roll 14, and two coating liquid storage sections 16 (16a, 16c) on both sides in the width direction. The coating liquid storage sections 16 (16a, 16c) are capable of storing the coating liquid 62 in the area surrounded by the back plate 20 and the side plate 18.

The two application liquid storage sections 16 (16a, 16c) store second resin composition solutions 62a, 62c. Unlike the first embodiment, the application device 30 according to the second embodiment does not store the first resin composition solution in the application liquid storage section 16.

The backup roll 12 continuously transports the support 60 by rotating. The support 60 transported by the backup roll 12 passes through the gap 22 formed between the backup roll 12 and the comma roll 14. As the support 60 passes through the gap 22, second resin composition solutions 62a, 62c are supplied from the coating liquid reservoir 16 onto the support 60, forming coating films 64a, 64c.

The coating device 30 further includes a T-die coater 32. The T-die coater 32 is installed downstream of the backup roll 12 and the comma roll 14. The T-die coater 32 is installed so that its discharge outlet is located above the center of the support 60.

When the support 60 with the coating films 64a and 64c formed is transported, the T-die coater 32 applies the first resin composition solution 62b to the center of the support 60.

In the second embodiment, process B is performed first using the coating device 30 described above, followed by process A. In the second embodiment, the connection pattern of each coating film 64 is likely to be the connection pattern shown in Figure 6, but is not limited to this. As a variation of the second embodiment, the first resin composition solution may be applied to the center of the support using a comma coater, and then the second resin composition solution may be applied to both ends using a T-die coater.

The above describes process A and process B related to the second embodiment.

[Third embodiment]
Fig. 9 is a side cross-sectional view for explaining the method for applying a resin composition solution according to the third embodiment, and Fig. 10 is a plan view thereof. In the application device 40 of the third embodiment, components common to the application device 30 of the second embodiment are designated by the same reference numerals, and descriptions thereof will be omitted or simplified.

The coating device 40 includes a T-die coater 42 a, a T-die coater 42 b, and a T-die coater 42 c. The T-die coater 42 a and the T-die coater 42 c are installed in a stage upstream of the T-die coater 42 b.
The T-die coater 42a and the T-die coater 42c are each installed so that their discharge outlets are located above the ends of the support 60. In Fig. 10, the T-die coater 42a is installed so that its discharge outlet is located above the left end of the support 60, and the T-die coater 42c is installed so that its discharge outlet is located above the right end of the support 60.
The T-die coater 42 b is installed so that the discharge port is located above the center of the support 60 .

When the support 60 with the coating films 64a and 64c formed thereon is transported, the T-die coater 42b applies the first resin composition solution 62b to the center of the support 60.

In the third embodiment, the bonding mode of each coating film 64 tends to be the bonding mode shown in Fig. 5, but is not limited to this. Furthermore, as a modification of the third embodiment, the second resin composition may be applied to both end portions with a T-die coater, and then the first resin composition may be applied to the center portion with a T-die coater. In this case, the bonding mode of each coating film 64 tends to be the bonding mode shown in Fig. 6, but is not limited to this.
Furthermore, as another modification, the second resin composition may be applied to one end using a T-die coater, then the first resin composition may be applied to the center using a T-die coater, and then the second resin composition may be applied to the other end using a T-die coater. In this case, the bonding mode of each coating film 64 tends to be the bonding mode shown in FIG. 11 , but is not limited to this.
11, the end of the coating film 64a slightly overlaps the coating film 64b, and the end of the coating film 64b (the end on the right side in FIG. 11) slightly overlaps the coating film 64c.
As shown in the third embodiment and its modified example, step A and step B may be performed in a form in which a plurality of T-die coaters are arranged in a vertical line and the first resin composition and the second resin composition are applied successively.

[Fourth embodiment]
Fig. 12 is a side cross-sectional view for explaining the method for applying a resin composition solution according to the fourth embodiment, and Fig. 13 is a plan view thereof. Note that in the application device 50 of the fourth embodiment, components common to the application device 40 of the third embodiment are designated by the same reference numerals, and descriptions thereof will be omitted or simplified.

The coating device 50 is equipped with a T-die coater 52 having a discharge port divided into three in the width direction. The T-die coater 52 applies a first resin composition to the center of the support 60 while simultaneously applying a second resin composition to both ends.

As shown in Figures 12 and 13, in steps A and B of the fourth embodiment, the first resin composition and the second resin composition are simultaneously applied. In the fourth embodiment, the bonding pattern of each coating film 64 tends to be the bonding pattern shown in Figure 4, but is not limited to this.

<Process C>
After steps A and B, the first resin composition solution and the second resin composition solution are dried to obtain a pre-cut film (step C). Drying conditions can be appropriately set within a range that allows the solvent to be sufficiently evaporated. For example, the drying temperature can be in the range of 60°C to 140°C, and the drying time can be in the range of 1 minute to 60 minutes. The drying conditions are particularly suitable when dimethylacetamide is used as the solvent, since its boiling point is 165°C.
After step C and before step D, a step (step C-1) of winding up the pre-cut film together with the support into a roll may be performed. In this case, the pre-cut film may be unwound again before step D.

<Process D>
After step C, the pre-cut film is peeled off from the support (step D). The method for peeling off the pre-cut film from the support is not particularly limited, but may include a method of rolling up from the edge using tweezers, a method of making a slit in the pre-cut film and attaching adhesive tape to one side of the slit and then rolling up from the tape, a method of vacuum-adsorbing one side of the slit in the pre-cut film and then rolling up from that side, etc. As a rolling up method, it is desirable to roll up the film while winding it up on a roll.
Methods for making cuts in the pre-cut film include, but are not limited to, a method of cutting the pre-cut film with a cutting tool such as a blade, a method of cutting the pre-cut film with a laser, a method of cutting the pre-cut film with a water jet, etc. For example, when employing the above-mentioned methods, it is also possible to appropriately employ a technique such as superimposing ultrasonic waves on the cutting tool or adding a reciprocating motion or an up-and-down motion to improve cutting performance.
After step D and before step E, a step (step D-1) of winding the pre-cut film into a roll may be performed. In this case, the pre-cut film may be unwound again before step E. When winding the pre-cut film, it is preferable to sandwich an interleaf paper (anti-blocking film) therebetween.
By carrying out the step C-1 and/or the step D-1, it becomes possible to provide a certain period of time after the drying step (step C) before carrying out the cutting step (step G).
After the drying step (step C), the cut film is wound up once and held in that state for a certain period of time, thereby making it possible to equalize the distribution of the solvent in the thickness direction of the film. This point will be explained below.
5 and 6, when the two coating films overlap slightly, the solvent distribution in the film immediately after drying on the support is such that the amount of solvent remaining in the coating film on the support side is greater than the amount of solvent remaining in the coating film on the surface side. If a heating step (e.g., step F described below) is performed in this state, a difference in the amount of solvent volatilization occurs, and this part (the overlapping part) may be prone to tearing.
Therefore, by carrying out the steps C-1 and/or D-1 and equalizing the solvent distribution in the thickness direction of the overlapping portion, the remaining amount of solvent in the two types of coating films becomes relatively equal, making it possible to make the overlapping portion less likely to tear.
After step C-1 and/or step D-1, the film is kept in a rolled state for preferably 30 minutes or more, more preferably 3 hours or more. By keeping the film in a rolled state for this period, the solvent can be suitably diffused in the thickness direction.
Furthermore, when the steps C-1 and/or D-1 are performed, the pre-cut film is wound up once during the process, which allows the production equipment to be made compact. In other words, if all the steps are connected continuously, the production line will be quite long, which may impose restrictions on factory location, etc. On the other hand, if the winding step is performed during production, the production line can be divided into two, and the two divided lines can be arranged in parallel, allowing for a relatively compact production equipment.
Furthermore, by winding the film once during production, quality checks can be performed during the process.

<Process E>
After step D, both ends of the pre-cut film are gripped by a tenter-type conveying device (step E). Specifically, when a pin tenter-type conveying device is used as the tenter-type conveying device, both ends of the pre-cut film are gripped by being pierced by multiple pins of the pin tenter-type conveying device. When a clip tenter-type conveying device is used as the tenter-type conveying device, both ends of the pre-cut film are gripped by being clamped by multiple clips of the clip tenter-type conveying device. As the tenter-type conveying device, a conventionally known device (for example, the tenter-type conveying devices disclosed in Japanese Patent Nos. 4,843,996 and 4,821,960) can be used.

<Process F>
After step E, the pre-cut film is transported while both ends of the pre-cut film are held (step F). Heating may be performed during transportation. The heating temperature is not particularly limited, but when the first resin composition solution and the second resin composition solution are polyimide-based resin composition solutions, the heating temperature may be, for example, 150°C to 500°C and 1 minute to 60 minutes.
In the steps E and F, the pre-cut film may or may not be stretched in the width direction.

In step F, the pre-cut film typically shrinks in the width direction during transport. As a result, tensile force is applied to the portion of the film held by the tenter-type transport device. As will be described in more detail below, the tear strength of the pre-cut film at both ends (portions formed from the second resin composition solution) is greater than the tear strength of the central portion (portion formed from the second resin composition solution). Therefore, tearing of the pre-cut film at the held portions (both ends) is suppressed. In particular, when a pin tenter-type transport device is used as the tenter-type transport device, tearing caused by the pins of the pin tenter-type transport device is more effectively suppressed.

<Process G>
After step F, the portion formed from the second resin composition solution is removed from the pre-cut film to obtain a resin film (step G). In step G, it is sufficient to remove at least the portion formed from the second resin composition solution, and a portion formed from the first resin composition solution may also be removed along with the portion formed from the second resin composition solution. The resin film obtained in this manner consists only of the portion formed from the first resin composition solution. In other words, a resin film consisting only of portions with relatively low tear strength is obtained.

The CTE (coefficient of linear thermal expansion) of the resin film is 5 ppm/K or more and 50 ppm/K or less. To improve heat resistance, it is preferably 45 ppm/K or less, more preferably 40 ppm/K or less, and even more preferably 35 ppm/K or less. For industrial purposes, it may be 6 ppm/K or more, or even 7 ppm/K or more.

The thickness of the resin film is not particularly limited, but is preferably 5 μm to 125 μm, more preferably 7.5 μm to 75 μm, and even more preferably 12.5 μm to 50 μm.

The method for removing the portion formed from the second resin composition solution from the pre-cut film is not particularly limited, and a conventionally known slitter or the like can be used.

As described above, according to the resin film manufacturing method of this embodiment, even resin films with low tear strength can be transported using a conventional tenter-type transport device. Furthermore, because both ends of the pre-cut film are formed solely from the second resin composition solution, it is possible to minimize waste of raw materials associated with the portions removed in process G.

The following describes the first resin composition solution and the second resin composition solution.

The first resin composition solution and the second resin composition solution are not particularly limited, as long as they are configured such that, after step C and before step F, the tear strength of the portion of the pre-cut film formed from the second resin composition solution is greater than the tear strength of the portion formed from the first resin composition solution, and the CTE of the resin film is 5 ppm/K or more and 50 ppm/K or less.

The first resin composition solution contains a first resin and a filler, and the content of the filler relative to the first resin is 0.1% by mass or more and 50% by mass or less.

The first resin is not particularly limited as long as it can be a resin capable of being solution-cast into a film, and it can be not only a resin but also a precursor of that resin. From an industrial perspective, it is particularly preferred for resins that are difficult to form into a film from a melt. Specific examples include cellulose triacetate, aromatic polyamide, polyimide, polyetherimide, polyamideimide, polyesterimide, polybenzoxazole, polybenzimidazole, and polybenzothiazole. Polyamic acid is also an example of a polyimide precursor. Of these, polyimide-based resins such as polyimide, polyamideimide, polyetherimide, and polyimidebenzoxazole are particularly preferred.

The filler content of the first resin composition solution is 0.1% by mass or more relative to the first resin. Because this reduces the CTE of the resin film, it is preferably 0.2% by mass or more, and more preferably 0.3% by mass or more. Furthermore, the filler content of the first resin composition solution is 50% by mass or less relative to the first resin. Because this improves the mechanical properties of the resin film, it is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less.

The first resin composition solution preferably contains a predetermined amount of the first resin and a filler. Specific examples include cellulose triacetate resin composition solutions, polyetherimide resin composition solutions, polyesterimide resin composition solutions, polybenzoxazole resin composition solutions, polybenzimidazole resin composition solutions, polybenzothiazole resin composition solutions, polyimide-based resin composition solutions, aromatic polyamide-based resin composition solutions, and polyamideimide-based resin composition solutions. Among these, polyimide-based resin composition solutions are preferred. Polyimide-based resin films, generally referred to as transparent polyimides, often have low tear strength. However, the resin film manufacturing method according to this embodiment can be used to suitably manufacture transparent polyimide-based resin films with low tear strength.

From the standpoints of operability (applicability) and economy, the concentration of the first resin in the first composition solution is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. It is also preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less.

The first polyimide resin composition solution may be a polyamic acid (polyimide precursor) solution or a polyimide solution. When a polyamic acid solution is used, a dehydration ring-closing reaction is carried out by heat treatment in step F to form a polyimide film. When a polyimide solution is used, a polyimide film is formed by volatilizing the solvent in step C.
The heat treatment conditions can be appropriately set within a range that allows the polyamic acid to react with the polyimide. The heat treatment temperature can be set, for example, in the range of 250 to 500°C, preferably in the range of 300 to 400°C. The heat treatment time can be appropriately set depending on the heat treatment temperature, for example, in the range of 5 to 60 minutes, preferably in the range of 10 to 30 minutes.

The polyamic acid solution is obtained by reacting diamines and tetracarboxylic acids in a solvent.

The tetracarboxylic acids may be aromatic tetracarboxylic acids (including their acid anhydrides), aliphatic tetracarboxylic acids (including their acid anhydrides), or alicyclic tetracarboxylic acids (including their acid anhydrides) commonly used in polyimide synthesis. Among these, aromatic tetracarboxylic acid anhydrides and alicyclic tetracarboxylic acid anhydrides are preferred, with aromatic tetracarboxylic acid anhydrides being more preferred from the standpoint of heat resistance and alicyclic tetracarboxylic acids being more preferred from the standpoint of light transmittance. When these are acid anhydrides, they may contain one or two anhydride structures within the molecule, but preferably have two anhydride structures (dianhydrides). Tetracarboxylic acids may be used alone or in combination of two or more.

Among the above polyamic acid solutions, solutions that can produce colorless and highly transparent polyimides are preferred.

Aromatic tetracarboxylic acids that can be used to obtain colorless and highly transparent polyimides include 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid, 4,4'-oxydiphthalic acid, 3,4'-oxydiphthalic acid, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylic acid) 1,4-phenylene, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-yl)benzene-1,4-dicarboxylate, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, and 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene-2,5-di 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(4-isopropyl-toluene-2 ,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(benzene- 1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid [0039] tetracarboxylic acids such as xathiol-1,1-dioxide-3,3-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-diphenylsulfonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, 2,2',3,3'-biphenyltetracarboxylic acid, pyromellitic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]diphthalic acid, and 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]diphthalic acid, and acid anhydrides thereof. Among these, dianhydrides having two acid anhydride structures are preferred, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride and 4,4'-oxydiphthalic dianhydride are particularly preferred. The aromatic tetracarboxylic acids may be used alone or in combination of two or more. When heat resistance is important, the aromatic tetracarboxylic acids preferably account for 50% by mass or more of the total tetracarboxylic acids, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more.

Alicyclic tetracarboxylic acids include 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,3,4-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3',4,4'-bicyclohexyltetracarboxylic acid, bicyclo[2,2,1]heptane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]octane-2,3,5,6-tetracarboxylic acid, bicyclo[2, 2,2]oct-7-ene-2,3,5,6-tetracarboxylic acid, tetrahydroanthracene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid, decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4:5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6, 7-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid (also known as "norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-(methylnorbornane)-5,5",6,6"-tetracarboxylic acid , norbornane-2-spiro-α-cyclohexanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid (also known as "norbornane-2-spiro-2'-cyclohexanone-6'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2"-(methylnorbornane)-5,5",6,6"-tetracarboxylic acid, norbornane-2- Spiro-α-cyclopropanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cyclobutanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cycloheptanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cyclooctanone-α'-spiro-2' '-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclononanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclodecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloundecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid norbornane-2-spiro-α-cyclododecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cyclotridecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cyclotetradecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cyclodode ... Examples of such tetracarboxylic acids include cyclopentadecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-(methylcyclopentanone)-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, and norbornane-2-spiro-α-(methylcyclohexanone)-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, as well as acid anhydrides thereof. Among these, dianhydrides having two acid anhydride structures are preferred, and in particular, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are preferred, with 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4,5-cyclohexanetetracarboxylic dianhydride being more preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride being even more preferred. These may be used alone or in combination of two or more. When transparency is important, the alicyclic tetracarboxylic acids preferably account for, for example, 50% by mass or more of the total tetracarboxylic acids, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more.

The polyamic acid solution may contain tricarboxylic acids and dicarboxylic acids.

Tricarboxylic acids include aromatic tricarboxylic acids such as trimellitic acid, 1,2,5-naphthalenetricarboxylic acid, diphenylether-3,3',4'-tricarboxylic acid, and diphenylsulfone-3,3',4'-tricarboxylic acid; hydrogenated versions of the above aromatic tricarboxylic acids such as hexahydrotrimellitic acid; alkylene glycol bistrimellitates such as ethylene glycol bistrimellitate, propylene glycol bistrimellitate, 1,4-butanediol bistrimellitate, and polyethylene glycol bistrimellitate; and monoanhydrides and esters thereof. Among these, monoanhydrides containing a single acid anhydride structure are preferred, with trimellitic anhydride and hexahydrotrimellitic anhydride being particularly preferred. These may be used alone or in combination.

Dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid; hydrogenated versions of these aromatic dicarboxylic acids such as 1,6-cyclohexanedicarboxylic acid; oxalic acid, succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecadioic acid, dodecanedioic acid, and 2-methylsuccinic acid; and acid chlorides and esters thereof. Among these, aromatic dicarboxylic acids and their hydrogenated versions are preferred, with terephthalic acid, 1,6-cyclohexanedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid being particularly preferred. Dicarboxylic acids may be used alone or in combination.

There are no particular limitations on the diamines or isocyanates used to obtain colorless, highly transparent polyimides. Examples include aromatic diamines, aliphatic diamines, alicyclic diamines, aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates, which are commonly used in polyimide synthesis, polyamideimide synthesis, and polyamide synthesis. From the perspective of heat resistance, aromatic diamines are preferred, and from the perspective of transparency, alicyclic diamines are preferred. Furthermore, the use of aromatic diamines with a benzoxazole structure can achieve high heat resistance, as well as a high modulus of elasticity, low thermal shrinkage, and a low coefficient of linear expansion. Diamines and isocyanates may be used alone or in combination.

Examples of aromatic diamines include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4 -(3-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 4-amino-N-(4-aminophenyl)benzamide, 3,3' -diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-trifluoromethyl-4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane phenyl]ethane, 1,1-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-(4-aminophenoxy)phenyl]butane, 1,4-bis[4-(4-aminophenoxy)phenyl]butane, 2, 2-bis[4-(4-aminophenoxy)phenyl]butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-amino 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, biphenyl Bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[(3-aminophenoxy) benzoyl]benzene, 1,1-bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl sulfide, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl] ethane, bis[4-(3-aminophenoxy)phenyl]sulfoxide, 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, bis[4-{4-(4-aminophenoxy)phenoxy phenyl]sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α-dimethylbenzyl]benzene 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzo Phenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3'-diamino-4,4'-diviphenoxybenzophenone, 4,4'-diamino-5,5'-diviphenoxybenzophenone, 3,4'-diamino-4,5'-diviphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone benzoyl)benzene, 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 1,4-bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4-amino-5-biphenoxybenzoyl)benzene, 1,4 -bis(4-amino-5-biphenoxybenzoyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzonitrile, 4,4'-[9H-fluorene-9,9-diyl]bisaniline (also known as "9,9-bis(4-aminophenyl)fluorene"), spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl) ))]bisaniline, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline, and aromatic diamines in which some or all of the hydrogen atoms on the aromatic ring of the above-mentioned aromatic diamines have been substituted with halogen atoms, alkyl or alkoxy groups having 1 to 3 carbon atoms, cyano groups, or halogenated alkyl or alkoxy groups having 1 to 3 carbon atoms in which some or all of the hydrogen atoms of the alkyl or alkoxy groups have been substituted with halogen atoms. The aromatic diamines having a benzoxazole structure are not particularly limited, and examples thereof include 5-amino-2-(p-aminophenyl)benzoxazole, 6-amino-2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis(5-aminobenzoxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2,6-(4,4'- diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole and the like. Among these, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4-amino-N-(4-aminophenyl)benzamide, 4,4'-diaminodiphenyl sulfone, and 3,3'-diaminobenzophenone are particularly preferred. The aromatic diamines may be used alone or in combination.

Examples of alicyclic diamines include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, and 4,4'-methylenebis(2,6-dimethylcyclohexylamine). Among these, 1,4-diaminocyclohexane and 1,4-diamino-2-methylcyclohexane are particularly preferred, with 1,4-diaminocyclohexane being more preferred. Alicyclic diamines may be used alone or in combination.

Examples of diisocyanates include diphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-diethyl Diphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenylether-4,4' -diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-(2,2-bis(4-phenoxyphenyl)propane)diisocyanate, 3,3'- or 2,2'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'- or 2,2'-di Examples of the diisocyanate include aromatic diisocyanates such as ethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, and 3,3'-diethoxybiphenyl-4,4'-diisocyanate, and diisocyanates obtained by hydrogenating any of these (for example, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate). Among these, diphenylmethane-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and 1,4-cyclohexane diisocyanate are preferred from the viewpoints of low moisture absorption, dimensional stability, cost, and polymerizability. The diisocyanates may be used alone or in combination.

The solvent may be any solvent capable of dissolving polyimide or a polyimide precursor, and aprotic polar solvents are suitable. Examples include N,N-di-lower alkylcarboxylamides such as N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, and N,N-dimethylmethoxyacetamide, as well as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, diglyme, m-cresol, hexamethylphosphoramide, N-acetyl-2-pyrrolidone, hexamethylphosphoramide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and p-chlorophenol. The solvent may also be a mixture of two or more types.

The filler is not particularly limited, but examples include organic particles and inorganic particles, with inorganic particles being particularly preferred. Examples of inorganic particles include metal oxide particles such as silica, zirconia, alumina, titania, titanium oxide, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide, as well as metal fluoride particles such as magnesium fluoride and sodium fluoride. Transparent or colorless fillers are preferred. Silica is more preferred from the standpoint of dispersibility in resins and heat resistance.

The shape of the filler is not particularly limited, but it may be particulate or fibrous.

The size of the filler is not particularly limited, but is preferably 0.5 to 180 nm, and more preferably 2 to 100 nm. If it is 0.5 nm or larger, the low CTE effect of the resin film can be exerted. Furthermore, if it is 180 nm or smaller, cloudiness, turbidity, or coloration of the resin film can be suppressed.

Fillers may be used alone or in combination.

The location of the filler present in the resin film is not particularly limited, but it may be dispersed throughout the resin film, concentrated in specific locations within the resin film, or exposed from the surface of the resin film.

The second resin composition solution contains a second resin and does not contain a filler, or if it does contain a filler, the content is less than that of the first resin composition solution and is 2% by mass or less relative to the second resin.

The second resin composition solution does not contain a filler, or if it does contain a filler, the content is less than that of the first resin composition solution and is 2% by mass or less relative to the second resin. To ensure good tear strength at both ends, the filler content relative to the second resin is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0% by mass.

The second resin is not particularly limited as long as it can be solution-cast and has a higher tear strength than the first resin when formed into a film. It may have the same composition as the first resin or a different composition. Specific examples include cellulose triacetate, aromatic polyamide, polyimide, polyetherimide, polyamideimide, polyesterimide, polybenzoxazole, polybenzimidazole, and polybenzothiazole. Polyamic acid is also an example of a polyimide precursor. Among these, polyimide-based resins such as polyimide, polyamideimide, polyetherimide, and polyimidebenzoxazole are particularly preferred. Examples of the second resin composition solution include polyimide-based resin composition solutions, polyamide-based resin composition solutions, and polyamideimide-based resin composition solutions. When using a polyimide-based resin composition solution as the first resin composition solution, it is preferable to use a polyimide-based resin composition solution as the second resin composition solution, as their heat resistance is similar. It is preferable that the second resin composition solution has heat resistance equal to or greater than that of the first resin composition solution.

From the standpoints of operability (applicability) and economy, the concentration of the second resin in the second composition solution is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. It is also preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less.

The second polyimide-based resin composition solution may be a polyamic acid (polyimide precursor) solution or a polyimide solution. When a polyamic acid solution is used, a dehydration ring-closing reaction is carried out by heat treatment in step F to form a polyimide film. When a polyimide solution is used, a polyimide film is formed by volatilizing the solvent in step C. The heat treatment conditions are the same as those for the first polyimide-based resin composition solution.

The polyamic acid solution is obtained by reacting diamines with tetracarboxylic dianhydrides in a solvent.

The tetracarboxylic acids may be aromatic tetracarboxylic acids (including their acid anhydrides), aliphatic tetracarboxylic acids (including their acid anhydrides), or alicyclic tetracarboxylic acids (including their acid anhydrides) that are commonly used in polyimide synthesis. Of these, aromatic tetracarboxylic acid anhydrides and alicyclic tetracarboxylic acid anhydrides are preferred. Tetracarboxylic acids may be used alone or in combination.

Examples of alicyclic tetracarboxylic acids include alicyclic tetracarboxylic acids such as cyclobutane tetracarboxylic acid, 1,2,4,5-cyclohexane tetracarboxylic acid, and 3,3',4,4'-bicyclohexyl tetracarboxylic acid, as well as acid anhydrides thereof. Among these, dianhydrides having two anhydride structures (e.g., cyclobutane tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, and 3,3',4,4'-bicyclohexyl tetracarboxylic dianhydride) are preferred. The alicyclic tetracarboxylic acids may be used alone or in combination of two or more.
When transparency is important, the alicyclic tetracarboxylic acids preferably account for 80% by mass or more of the total tetracarboxylic acids, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

The aromatic tetracarboxylic acids are not particularly limited, but examples thereof include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanoic anhydride.
When heat resistance is important, the aromatic tetracarboxylic acids preferably account for 80% by mass or more of the total tetracarboxylic acids, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

The diamines are not particularly limited, and aromatic diamines, aliphatic diamines, and other types commonly used in polyimide synthesis can be used. From the standpoint of heat resistance, aromatic diamines are preferred, and among aromatic diamines, aromatic diamines having a benzoxazole structure are more preferred. The use of aromatic diamines having a benzoxazole structure makes it possible to achieve high heat resistance as well as a high modulus of elasticity, low thermal shrinkage, and a low coefficient of linear expansion. Diamines may be used alone or in combination of two or more types.

Aromatic diamines having a benzoxazole structure are not particularly limited, and examples thereof include 5-amino-2-(p-aminophenyl)benzoxazole, 6-amino-2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis(5-aminobenzoxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2,6-(4,4'-diazobenzoxazole), 1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, ... 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, and the like.

Examples of aromatic diamines other than the aromatic diamines having a benzoxazole structure described above include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene (bisaniline), 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, and biphenylsulfonyl ethers. Bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulf oxide, 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4- 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-(4-aminophenoxy)phenyl]butane, 1,4-bis[4-(4-aminophenoxy)phenyl]butane, 2,2-bis[4-(4-aminophenoxy)phenyl]butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]- 2-[4-(4-aminophenoxy)-3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene benzene, 4,4'-bis[(3-aminophenoxy)benzoyl]benzene, 1,1-bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl sulfide, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, bis[4-(3-aminophenoxy)phenyl]sulfoxide, 4, 4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]
Benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone,3,3'-diamino-4-phenoxybenzophenone,4,4'-diamino-5-phenoxybenzophenone,3,4'-diamino-4-phenoxybenzophenone,3,4'-diamino-5'-phenoxybenzophenone,3,3'-diamino-4,4'-diviphenoxybenzophenone,4,4'-diamino-5,5'-diviphenoxybenzophenone,3,4'-diamino-4,5'-diviphenoxybenzophenone,3,3'-diamino-4-biphenoxybenzophenone,4,4'-diamino-5-biphenoxy benzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 1,4-bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4- and aromatic diamines in which some or all of the hydrogen atoms on the aromatic ring of the aromatic diamine have been substituted with halogen atoms, alkyl or alkoxy groups having 1 to 3 carbon atoms, cyano groups, or halogenated alkyl or alkoxy groups having 1 to 3 carbon atoms in which some or all of the hydrogen atoms of the alkyl or alkoxy groups have been substituted with halogen atoms.

Examples of the aliphatic diamines include 1,2-diaminoethane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, and 1,8-diaminoethane.
Examples of the aliphatic diamines include 1,4-diaminocyclohexane and 4,4'-methylenebis(2,6-dimethylcyclohexylamine).
The total amount of diamines other than aromatic diamines (aliphatic diamines) is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less of all diamines. In other words, aromatic diamines are preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more of all diamines.

The solvent can be the same as that described in the section on the first resin composition solution.

[Film before cutting]
The pre-cut film according to this embodiment is
The center and
and two end portions formed continuously from the central portion at both ends of the central portion,
the central portion is composed of a first resin composition containing a first resin and a filler, and a content of the filler is 0.1% by mass or more and 50% by mass or less with respect to the first resin;
the two end portions are made of a second resin composition containing a second resin, and the second resin composition does not contain a filler, or even if it contains a filler, the content of the filler is less than that of the first resin composition and is 2 mass % or less relative to the second resin;
The tear strength at both ends is greater than the tear strength at the center.

The pre-cut film can be obtained by the steps A to C of the resin film manufacturing method according to this embodiment.
Here, the "first resin composition" refers to the composition (sheet-like material) obtained after drying the first resin composition solution in step C, and the "second resin composition" refers to the composition (sheet-like material) obtained after drying the second resin composition solution in step C.

It is preferable that the CTE of the central portion of the uncut film is 5 ppm/K or more and 50 ppm/K or less. Since this improves the heat resistance of the resin film, it is preferably 45 ppm/K or less, more preferably 40 ppm/K or less, and even more preferably 35 ppm/K or less. From an industrial perspective, it may be 6 ppm/K or more, or even 7 ppm/K or more.

The total light transmittance of the central portion of the film before cutting is preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more. There is no particular upper limit to the total light transmittance, but industrially it may be 99% or less, and even 98% or less is acceptable.

The haze ratio of the central portion of the film before cutting is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less. There is no particular lower limit for the haze ratio, but industrially it may be 0.01% or more, and even 0.1% or more is acceptable.

The YI (yellowness index) of the central portion of the film before cutting is preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less. There is no particular lower limit for YI (yellowness index), but industrially it may be 1 or more.

The static friction coefficient of the central portion of the film before cutting is preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.5 or less. There is no particular lower limit for the static friction coefficient, but industrially it may be 0.01 or more, and even 0.1 or more is acceptable.

The tear strength of the central portion, as measured by the method below, is preferably within the range of 0.1 to 15 N/mm, and more preferably within the range of 1 to 10 N/mm.

The tear strength of both ends is preferably in the range of 0.5 to 30 N/mm, more preferably in the range of 1 to 20 N/mm, as measured by the following method.
The tear strength of the both end portions is preferably more than 1 time and not more than 10 times, more preferably more than 1.1 times and not more than 5 times, the tear strength of the central portion.

<Method for measuring tear strength>
According to the trouser tearing method described in JIS K7128-1, the test speed is 200 mm/min, and the tear strength is the average value of the remaining 50 mm excluding the 20 mm at the start of tearing and the 5 mm before the end of tearing.
[Tear strength (N/mm)] = [tear force of test piece (N)] / [thickness of test piece (d)]

The width of both ends (the width of each end) is not particularly limited as long as it can be gripped by a conventionally known tenter-type conveying device, and is generally 5 mm or more, more preferably 10 mm or more. The upper limit of the width is not particularly limited, and for example, the sum of both ends may be 50% or less of the total width of the film, more preferably 30% or less, and even more preferably 10% or less.
The width of both ends (the width of each end) is not particularly limited as long as it can be gripped by a conventionally known tenter-type conveying device, and for example, the sum of the widths of both ends is 0.1% or more of the total width of the film, more preferably 0.5% or more, and even more preferably 1% or more. The upper limit of the width is not particularly limited, and for example, the sum of the widths of both ends may be 50% or less of the total width of the film, more preferably 30% or less, and even more preferably 10% or less.

The above describes the pre-cut film related to this embodiment.

The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention.

Synthesis Example 1 (Preparation of Polyamic Acid Solution A)
A reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer was purged with nitrogen, and then 1,470.8 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 775.6 parts by mass of 4,4'-oxydiphthalic acid (ODPA), 3,202.4 parts by mass of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB), 5,448.8 parts by mass of dimethylacetamide-dispersed silica sol (DMAc-ST manufactured by Nissan Chemical Industries, Ltd.), and 21,795 parts by mass of N,N-dimethylacetamide were charged into the reaction vessel under a nitrogen atmosphere and dissolved therein. The mixture was then stirred at room temperature for 24 hours to obtain a polyamic acid solution A having a solids content of 17.2% by mass and a reduced viscosity of 4.5 dl/g.

Synthesis Example 2 (Preparation of Polyimide Solution B)
After replacing the atmosphere in a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer with nitrogen, 551 parts by weight of N,N-dimethylacetamide (DMAC) and 64.1 parts by weight of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) were added to the reaction vessel under a nitrogen atmosphere and stirred to dissolve the TFMB in the DMAC. Next, while stirring the reaction vessel under a nitrogen stream, 44.4 parts by weight of 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride (6FDA) and 29.4 parts by weight of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) were added over a period of about 10 minutes. The mixture was then stirred for 6 hours while maintaining the temperature in the range of 20 to 40°C, resulting in a polymerization reaction and a viscous polyamic acid solution.
Next, 410 parts by mass of DMAC was added to the obtained polyamic acid solution to dilute it, and then 25.83 parts by mass of isoquinoline was added as an imidization accelerator. The polyamic acid solution was kept at a temperature of 30 to 40°C while stirring, and 122.5 parts by mass of acetic anhydride was slowly added dropwise as an imidization agent over a period of about 10 minutes. Thereafter, the liquid temperature was further kept at 30 to 40°C and stirring was continued for 12 hours to carry out a chemical imidization reaction, thereby obtaining a polyimide solution.
Next, 1,000 parts by mass of the resulting polyimide solution containing the imidization agent and the imidization accelerator was transferred to a reaction vessel equipped with a stirrer and stirring blades. While stirring at 120 rpm, the temperature was maintained at 15-25°C, and 1,500 parts by mass of methanol was added dropwise at a rate of 10 g/min. When approximately 800 parts by mass of methanol had been added, the polyimide solution became cloudy, confirming the precipitation of powdery polyimide. The entire 1,500 parts by mass of methanol was then added, completing the precipitation of polyimide. The contents of the reaction vessel were then filtered using a suction filter, followed by washing and filtering with an additional 1,000 parts by mass of methanol. 50 parts by mass of the filtered polyimide powder was then dried at 50°C for 24 hours using a dryer equipped with a local exhaust system, and then further dried at 260°C for 2 hours to remove remaining volatile components, yielding a polyimide powder. The reduced viscosity of the resulting polyimide powder was 2.1 dl/g. Next, 42 parts by mass of the obtained polyimide powder was dissolved in 168 parts by mass of DMAC to obtain a polyimide solution B having a solid content of 20% by mass.

Synthesis Example 3 (Preparation of Polyimide Solution C)
A reaction vessel equipped with a nitrogen inlet tube, a Dean-Stark apparatus, a reflux condenser, a thermometer, and a stirrer was charged with 124.15 parts by mass of 4,4'-diaminodiphenyl sulfone (4,4'-DDS), 124.15 parts by mass of 3,3'-diaminodiphenyl sulfone (3,3'-DDS), and 750 parts by mass of gamma-butyrolactone (GBL) while introducing nitrogen gas. Subsequently, 248.18 parts by mass of 4,4'-oxydiphthalic acid dihydrate (ODPA), 58.8 parts by mass of biphenyltetracarboxylic dianhydride, 335 parts by mass of GBL, and 390 parts by mass of toluene were added at room temperature, and the internal temperature was then raised to 160°C. The mixture was heated to reflux at 160°C for 1 hour to carry out imidization. After completion of imidization, the temperature was raised to 180°C, and the reaction was continued while withdrawing the toluene. After 12 hours of reaction, the oil bath was removed, the temperature was returned to room temperature, and 1,149 parts by mass of GBL was added so that the solid content became 20% by mass, to obtain a polyimide solution C having a reduced viscosity of 0.6 dl/g.

Synthesis Example 4 (Preparation of Polyamic Acid Solution D)
After the atmosphere inside a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer was replaced with nitrogen, 196.1 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 227.3 parts by mass of 4-amino-N-(4-aminophenyl)benzamide (DABAN), and 1694 parts by mass of N,N-dimethylacetamide were charged into the reaction vessel under a nitrogen atmosphere and dissolved, followed by stirring at room temperature for 24 hours to obtain polyamic acid solution D having a solids content of 20% by mass and a reduced viscosity of 4.5 dl/g.

Synthesis Example 5 (Preparation of Polyamideimide Solution E)
After the atmosphere in a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer was replaced with nitrogen, 153.7 parts by mass of trimellitic anhydride, 256.4 parts by mass of O-tolidine diisocyanate, 29.4 parts by mass of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 32.2 parts by mass of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 1 part by mass of triethylenediamine, and 1671 parts by mass of N-methyl-2-pyrrolidone were added, and the mixture was heated to 130°C over 1 hour with stirring, and further reacted at 130°C for 5 hours to obtain a polyamideimide resin solution E having a reduced viscosity of 1.6 dl/g.

[Reduced viscosity]
The reduced viscosities (dL/g) of the prepared polyamic acid solutions A and D, polyimide solutions B and C, and polyamide-imide acid solution E were measured at 30°C using an Ubbelohse viscometer by dissolving 0.02 g of each sample in 10 mL of a mixed solvent (phenol/tetrachloroethane = 60/40 (mass ratio)).

Example 1
Polyamic acid solution A (Synthesis Example 1 (PAA-A)) was prepared. To a portion of this solution, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass; Nissan Chemical Industries) was added while stirring polyamic acid solution A so that the active ingredient was 10% by mass relative to the resin. Stirring was then maintained for 6 hours to obtain polyamic acid solution A-1 (PAA-A1).
Using the comma coater shown in Figures 1 and 2, polyamic acid solution A-1 was applied to a 500 mm-wide central portion of a PET film (A4100 manufactured by Toyobo Co., Ltd.) serving as a support, with the clearance adjusted so that the final film thickness would be 22 µm, and polyamic acid solution A was simultaneously applied to each of the two end portions in a 50 mm-wide area. At this time, side plates with a width of 10 mm were used.
The polyamic acid film was then dried at 100 to 110°C for 10 minutes to obtain a polyamic acid film, which was then wound up together with the PET film on a 6-inch ABS core to obtain a polyamic acid film roll. The polyamic acid film and the PET film were unwound from the obtained polyamic acid film roll, and the self-supporting polyamic acid film was peeled off from the PET film to obtain a polyamic acid film.
The obtained polyamic acid film was passed through a pin tenter having a pin sheet in which the pins were arranged so that the pin spacing was constant when the pin sheets were lined up, and the film edges were gripped by inserting them into the pins. The pin sheet spacing was adjusted so that the film would not break and unnecessary slack would not occur, and the film was conveyed so that the final pin sheet spacing was 520 mm. The film was then heated under the following conditions: 200°C for 3 minutes in the first stage, 250°C for 3 minutes in the second stage, 300°C for 3 minutes in the third stage, and 350°C for 3 minutes in the fourth stage to promote the imidization reaction. Thereafter, the film was cooled to room temperature over 2 minutes, and the edges of the film formed with polyamic acid solution A were slit to leave only the center portion, yielding a polyimide film 22 μm thick and 480 mm wide.

Example 2
Polyamic acid solution A (Synthesis Example 1) was prepared. Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient: 20% by mass; Nissan Chemical Industries) was added to a portion of this polyamic acid solution A while stirring, so that the active ingredient was 5% by mass relative to the resin. Stirring was then maintained for 6 hours, yielding polyamic acid solution A-2 (PAA-A2). Subsequently, Snowtex (registered trademark) DMAc-ST-ZL (DMAc dispersion of silica with an average particle size of 80 nm; active ingredient: 20% by mass; Nissan Chemical Industries) was added to the remaining polyamic acid solution A while stirring, so that the active ingredient was 0.5% by mass relative to the resin. Stirring was then maintained for 6 hours, yielding polyamic acid solution A-3 (PAA-A3).
A polyimide film having a thickness of 10 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that polyamic acid solution A-2 was applied instead of polyamic acid solution A-1, and polyamic acid solution A-3 was applied instead of polyamic acid solution A, while adjusting the clearance so that the final film thickness would be 10 μm.

Example 3
Polyamic acid solution A (Synthesis Example 1) was prepared. To a portion of this solution, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass; Nissan Chemical Industries) and Snowtex (registered trademark) DMAc-ST-ZL (DMAc dispersion of silica with an average particle size of 80 nm; active ingredient 20% by mass; Nissan Chemical Industries) were further added while stirring polyamic acid solution A, so that the active ingredient concentrations relative to the resin were 0.3% by mass and 0.2% by mass, respectively. Stirring was then maintained for 6 hours, yielding polyamic acid solution A-4 (PAA-A4).
A polyimide film having a thickness of 35 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that polyamic acid solution A-4 was applied instead of polyamic acid solution A-1 while adjusting the clearance so that the final film thickness would be 35 μm.

Example 4
Polyimide solution B (Synthesis Example 2 (PI-B)) was prepared. To a portion of this solution, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass: Nissan Chemical Industries) was added while stirring polyimide solution B so that the active ingredient content relative to the resin was 10% by mass. Stirring was then maintained for 6 hours to obtain polyimide solution B-1 (PI-B1).
A polyimide film having a thickness of 115 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that polyimide solution B-1 was applied instead of polyamic acid solution A-1, and polyimide solution B was applied instead of polyamic acid solution A, while adjusting the clearance so that the final film thickness would be 115 μm.

Example 5
Polyimide solution C (Synthesis Example 3 (PI-C)) was prepared. To a portion of this solution, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass: Nissan Chemical Industries) was added to polyimide solution B while stirring, so that the active ingredient content relative to the resin was 10% by mass. Stirring was then maintained for 6 hours, yielding polyimide solution C-1 (PI-C1).
Polyimide solution C was applied to both ends of a mirror-finished stainless steel belt using the comma coater shown in Figures 7 and 8, and then polyimide solution C-1 was applied to the center using a T-die, adjusting the clearance to give a final film thickness of 25 µm. At this time, the width of the center was 1000 mm, and the widths of both ends were 50 mm.
Then, the film was dried at 100 to 110° C. for 10 minutes, and after drying, it was peeled off from the support to obtain a self-supporting polyimide film.
The resulting uncut film was passed through a pin tenter with a pin sheet in which the pins were arranged so that the pin spacing was constant when the pin sheets were lined up, and the film edges were gripped by inserting them into the pins. The pin sheet spacing was adjusted to prevent the film from breaking and to prevent unnecessary slack. The film was conveyed so that the final pin sheet spacing was 1000 mm. The film was then heated at 200°C for 3 minutes in the first stage, 250°C for 3 minutes in the second stage, 300°C for 3 minutes in the third stage, and 350°C for 3 minutes in the fourth stage to promote the imidization reaction. The film was then cooled to room temperature over 2 minutes, and the edges of the film formed with polyimide solution B were slit to leave only the center portion, which was then continuously wound into a roll around a 3-inch ABS resin core to obtain a polyimide film 25 μm thick, 980 mm wide, and 500 m long.

Example 6
Polyimide solution A (Synthesis Example 1) and polyamic acid solution D (Synthesis Example 4 (PAA-D)) were prepared. Snowtex (registered trademark) DMAc-ST-ZL (DMAc dispersion of silica with an average particle size of 80 nm; active ingredient: 20% by mass; Nissan Chemical Industries, Ltd.) was added to a portion of this polyamic acid solution A while stirring, so that the active ingredient was 0.1% by mass relative to the resin. Stirring was then maintained for 6 hours, yielding polyimide solution A-5 (PAA-A5). Next, Snowtex (registered trademark) DMAc-ST-ZL (DMAc dispersion of silica with an average particle size of 80 nm; active ingredient: 20% by mass; Nissan Chemical Industries, Ltd.) was added to a portion of polyamic acid solution D while stirring, so that the active ingredient was 0.5% by mass relative to the resin. Stirring was then maintained for 6 hours, yielding polyimide solution D-1 (PAA-D1).
Polyimide solution A-5 was applied to both ends of a mirror-finished stainless steel belt using a T-die as shown in Figures 9 and 10, and polyamic acid solution D-1 was applied to the center using a T-die with the clearance adjusted to a final film thickness of 26 µm. At this time, the width of the center was 1000 mm, and the width of each end was 50 mm.
Then, it was dried at 100 to 110° C. for 10 minutes, and after drying, it was peeled off from the support to obtain a self-supporting polyamic acid film.
The resulting pre-cut film was passed through a pin tenter with a pin sheet in which the pins were arranged so that the pin spacing was constant when the pin sheets were lined up, and the film edges were gripped by inserting them into the pins. The pin sheet spacing was adjusted so that the film would not break and unnecessary slack would not occur, and the film was conveyed so that the final pin sheet spacing was 520 mm. The film was then heated under the following conditions: 200°C for 3 minutes in the first stage, 250°C for 3 minutes in the second stage, 300°C for 3 minutes in the third stage, and 350°C for 3 minutes in the fourth stage to allow the imidization reaction to proceed. The film was then cooled to room temperature over 2 minutes, and the edges of the film formed with polyimide solution A-5 were slit to leave only the center portion, which was then continuously wound into a roll around a 3-inch ABS resin core to obtain a polyimide film 26 μm thick, 980 mm wide, and 500 m long.

Example 7
A polyamideimide solution E (Synthesis Example 5 (PAI-E)) was prepared. Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass: Nissan Chemical Industries) was added to a part of this polyamideimide solution E while stirring the polyamideimide solution E so that the active ingredient content relative to the resin was 10% by mass. Stirring was then maintained for 6 hours to obtain polyamideimide solution E-1 (PAI-E1).
A polyimide film having a thickness of 42 μm and a width of 480 mm was obtained in the same manner as in Example 6, except that polyamideimide solution E was applied instead of polyimide solution A-5 while adjusting the clearance so that the final film thickness would be 42 μm, and polyamideimide solution E-1 was used instead of polyamic acid solution D-1.

(Example 8)
Polyimide solution B (Synthesis Example 2) and polyamic acid solution A (Synthesis Example 1) were prepared. Of these, Snowtex (registered trademark) DMAc-ST-ZL (DMAc dispersion of silica with an average particle size of 80 nm; active ingredient: 20% by mass; Nissan Chemical Industries) was added to polyimide solution B while stirring, so that the active ingredient content relative to the resin was 0.5% by mass. Stirring was then maintained for 6 hours to obtain polyimide solution B-2 (PI-B2). Next, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient: 20% by mass; Nissan Chemical Industries) was added to polyimide solution A while stirring, so that the active ingredient content relative to the resin was 10% by mass. Stirring was then maintained for 6 hours to obtain polyimide solution A-1 (PI-A1).
A polyimide film having a thickness of 25 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that polyimide solution B-2 was applied instead of polyamic acid solution A while adjusting the clearance so that the final film thickness would be 25 μm.

Example 9
A polyimide film having a thickness of 75 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that a clip tenter, which holds both ends with clips, was used instead of a pin tenter having a pin sheet in which pins were arranged so that the pin spacing would be constant when the pin sheet was lined up, and that polyamic acid solution A was applied while adjusting the clearance so that the final film thickness would be 75 μm.

Example 10
Polyimide solution B (Synthesis Example 2) and polyamideimide solution E (Synthesis Example 5) were prepared. Of these, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass: Nissan Chemical Industries) was added to polyamideimide solution E while stirring, so that the active ingredient content relative to the resin was 10% by mass. Stirring was then maintained for 6 hours, yielding polyamideimide solution E-1 (PAI-E1).
A polyamideimide film having a thickness of 25 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that polyimide solution B was applied instead of polyamic acid solution A, and polyamideimide solution E-1 was applied instead of polyamic acid solution A-1, with the clearance adjusted so that the final film thickness would be 25 μm.

Example 11
A polyimide film having a thickness of 22 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that instead of Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient: 20% by mass: Nissan Chemical Industries, Ltd.), titanium oxide (average particle size 200 nm) was added so that the active ingredient would be 0.75% by mass relative to the resin (PAA-A6).

Example 12
Polyimide solution B (Synthesis Example 2) and polyamideimide solution E (Synthesis Example 5) were prepared. Of these, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass; Nissan Chemical Industries) was added to polyimide solution B while stirring, so that the active ingredient content relative to the resin was 10%. Stirring was then maintained for 6 hours, yielding polyimide solution B-1. Next, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass; Nissan Chemical Industries) was added to polyamideimide solution E while stirring, so that the active ingredient content relative to the resin was 1%. Stirring was then maintained for 6 hours, yielding polyamideimide solution E-2 (PAI-E2).
A polyamideimide film having a thickness of 25 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that polyamideimide solution E-2 was applied instead of polyamic acid solution A, and polyimide solution B-1 was applied instead of polyamic acid solution A-1, with the clearance adjusted so that the final film thickness would be 25 μm.

(Comparative Example 1)
Polyamic acid solution A (Synthesis Example 1) was prepared. Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient: 20% by mass; manufactured by Nissan Chemical Industries) was added to a portion of this solution while stirring, so that the active ingredient was 10% by mass relative to the resin. Stirring was then maintained for 6 hours, yielding polyamic acid solution A-1. Next, Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient: 20% by mass; manufactured by Nissan Chemical Industries) was added to the remaining polyamic acid solution A while stirring, so that the active ingredient was 5% by mass relative to the resin. Stirring was then maintained for 6 hours, yielding polyamic acid solution A-2.
Using the comma coater shown in Figures 1 and 2, polyamic acid solution A-1 was applied to a 500 mm-wide central portion of a PET film (A4100 manufactured by Toyobo Co., Ltd.) serving as a support, with the clearance adjusted to give a final film thickness of 22 µm, and polyamic acid solution A-2 was simultaneously applied to each end of the central portion in a 50 mm-wide area. At this time, side plates with a width of 10 mm were used.
The polyamic acid film was then dried at 100 to 110°C for 10 minutes to obtain a polyamic acid film, which was then wound up together with the PET film on a 6-inch ABS core to obtain a polyamic acid film roll. The polyamic acid film and the PET film were unwound from the obtained polyamic acid film roll, and the self-supporting polyamic acid film was peeled off from the PET film to obtain a polyamic acid film.
The resulting polyamic acid film was passed through a pin tenter with a pin sheet in which the pins were arranged so that the pin spacing was constant when the pin sheets were lined up, and the film edges were gripped by inserting them into the pins. The pin sheet spacing was adjusted to prevent the film from breaking and to prevent unnecessary slack. The film was conveyed so that the final pin sheet spacing was 520 mm. The film was heated under the following conditions: 200°C for 3 minutes in the first stage, 250°C for 3 minutes in the second stage, 300°C for 3 minutes in the third stage, and 350°C for 3 minutes in the fourth stage, to allow the imidization reaction to proceed. The film was then cooled to room temperature over 2 minutes. Attempts to remove the film from the pins were made, but it broke at the holes through which the pins were inserted, making it impossible to obtain a film.

(Comparative Example 2)
Polyimide solution B (Synthesis Example 2) was prepared. A polyimide film having a thickness of 25 μm and a width of 480 mm was obtained in the same manner as in Example 1, except that polyimide solution B was applied instead of polyamic acid solution A and polyamic acid solution A-1 while adjusting the clearance so that the final film thickness would be 25 μm.

(Comparative Example 3)
Polyimide solution A (Synthesis Example 2) was prepared. Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient: 20% by mass; Nissan Chemical Industries) was added to a portion of this solution while stirring polyamic acid solution A so that the active ingredient content relative to the resin was 60% by mass. Stirring was then maintained for 6 hours to obtain polyamic acid solution A-7 (PAA-A7).
An attempt was made to produce a film in the same manner as in Example 1, except that polyimide solution A-7 was applied instead of polyamic acid solution A-1 while adjusting the clearance so that the final film thickness would be 25 μm. However, the film broke at the hole through which the pin was inserted, and no film could be obtained.

(Comparative Example 4)
Polyimide solution A (Synthesis Example 2) was prepared. Snowtex (registered trademark) DMAc-ST (DMAc dispersion of silica with an average particle size of 10 nm; active ingredient 20% by mass; Nissan Chemical Industries) was added to this polyamic acid solution A while stirring so that the active ingredient content relative to the resin was 10% by mass. Stirring was then maintained for 6 hours to obtain polyamic acid solution A-1.
An attempt was made to produce a film in the same manner as in Example 1, except that polyimide solution A-1 was applied instead of polyamic acid solution A while adjusting the clearance so that the final film thickness would be 25 μm. However, the film broke at the hole through which the pin was inserted, and no film could be obtained.

<CTE (Coefficient of Linear Thermal Expansion)>
The expansion/contraction rate of the film was measured in the machine direction (MD) and width direction (TD) at the time of application under the conditions below. The expansion/contraction rate/temperature was measured at intervals of 15°C, such as 30°C to 45°C and 45°C to 60°C. This measurement was continued up to 300°C, and the average value of all the measured values was calculated as CTE. Furthermore, the average value of the measured values in the MD and TD directions was calculated.
Device name: MAC Science TMA4000S
Sample length: 20 mm
Sample width: 2 mm
Heating start temperature: 25°C
Heating end temperature: 300°C
Temperature rise rate: 5°C/min
Atmosphere: Argon

<Total light transmittance>
The total light transmittance of the film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.) using a D65 lamp as the light source. The same measurement was performed three times, and the arithmetic average value was used.

<Haze rate>
The haze of the film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.) using a D65 lamp as the light source. The same measurement was carried out three times, and the arithmetic average value was used.

<YI (yellowness)>
The tristimulus values X, Y, and Z of the film were measured using a color meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) and a C2 light source in accordance with ASTM D1925, and the yellowness index (YI) was calculated using the following formula: The same measurement was performed three times, and the arithmetic mean value was used.
YI=100×(1.28X-1.06Z)/Y

<Static friction coefficient>
In accordance with JIS K-7125 (1999), a tensile tester (Tensilon RTG-1210 manufactured by A&D Corporation) was used to determine the static friction coefficient when the inner and outer surfaces of the film were joined together in an environment of 23°C and 65% RH. The weight of the sled (weight) around which the upper film was wound was 1.5 kg, and the size of the base area of the sled was 39.7 ^mm2 . The pulling speed during friction measurement was 200 mm/min.

<Film thickness measurement>
The thickness of the film was measured using a micrometer (Militron 1245D, manufactured by Fineruf Co., Ltd.).

<Tear strength>
The tear strength of the center and both end portions of the films obtained in the examples and comparative examples before cutting was measured. Specifically, the tear strength was determined according to the trouser tearing method described in JIS K7128-1, with a test speed of 200 mm/min, and the average tear strength was calculated over the remaining 50 mm, excluding the 20 mm at the start of tearing and the 5 mm before the end of tearing. The results are shown in Table 1.
[Tear strength (N/mm)] = [Tear stress of test piece (N)] / [Thickness of test piece (d)]

The tear strength obtained here (the tear strength listed in Table 1) is the tear strength of the polyimide film (resin film) after step G. If the tear strength of the portion of the polyimide film after step G formed from the second resin composition solution is greater than the tear strength of the portion formed from the first resin composition solution, then naturally, the tear strength of the portion of the pre-cut film after step C and before step F formed from the second resin composition solution will also be greater than the tear strength of the portion formed from the first resin composition solution.
The tear strength of the central portion of the uncut film after step C and before step F of Example 8 was measured by the same method as above and was found to be 1.8 N/mm. This also clearly shows that if the tear strength of the portion formed from the second resin composition solution in the polyimide film after step G is greater than the tear strength of the portion formed from the first resin composition solution, then the tear strength of the portion formed from the second resin composition solution in the uncut film after step C and before step F will also be greater than the tear strength of the portion formed from the first resin composition solution.

The polyimide films of Examples 1 to 12 did not break or deform after heat treatment because the tear strength of the portion formed from the second resin composition solution was greater than the tear strength of the portion formed from the first resin composition solution. They also had good CTE and transparency. On the other hand, the pre-cut films of Comparative Examples 1 to 4 were formed from a single resin composition solution with low tear strength, so tears occurred at the holes where the pins were inserted, and it was not possible to obtain a film.

10, 30, 40, 50 Coating device 12 Backup roll 14 Comma roll 16 (16a, 16b, 16c) Coating liquid storage section 18 (18a, 18b, 18c, 18d) Side plate 20 Back plate 22 Gap 60 Support 62 (62a, 62b, 62c) Coating liquid 64 (64a, 64b, 64c) Coating film

Claims (10)

Step A: applying a first resin composition solution to a central portion of a support;
Step B: applying a second resin composition solution to both end portions adjacent to the central portion;
A step C of drying the first resin composition solution and the second resin composition solution to obtain a pre-cut film;
Step D: peeling the pre-cut film from the support;
a step E of holding both end portions of the pre-cut film by a tenter-type conveying device after the step D;
a step F of conveying the uncut film while holding both end portions of the uncut film; and
After the step F, a step G is performed in which a portion formed from the second resin composition solution is removed from the pre-cut film to obtain a resin film.
and
the first resin composition solution contains a first resin and a filler, and the content of the filler is 0.1% by mass or more and 50% by mass or less with respect to the first resin;
the second resin composition solution contains a second resin and does not contain a filler, or if it contains a filler, the content of the filler is less than that of the first resin composition solution and is 2 mass% or less relative to the second resin;
A method for producing a resin film, characterized in that after step C and before step F, the pre-cut film has a tear strength of the portion formed from the second resin composition solution that is greater than the tear strength of the portion formed from the first resin composition solution. A method for manufacturing a resin film as described in claim 1, characterized in that the CTE of the resin film is 5 ppm/K or more and 50 ppm/K or less. A method for manufacturing a resin film as described in claim 1 or 2, characterized in that step E is a step of gripping both ends of the pre-cut film with pins of a pin tenter type conveying device. A method for producing a resin film described in any one of claims 1 to 3, characterized in that the resin film is a polyimide-based resin film. A method for producing a resin film described in any one of claims 1 to 4, characterized in that the support is a polymer film. A method for producing a resin film described in any one of claims 1 to 5, characterized in that the filler is silica. The center and
and two end portions formed continuously from the central portion at both ends of the central portion,
the central portion is composed of a first resin composition containing a first resin and a filler, and a content of the filler is 0.1% by mass or more and 50% by mass or less with respect to the first resin;
the two end portions are made of a second resin composition containing a second resin, and the second resin composition does not contain a filler, or even if it contains a filler, the content of the filler is less than that of the first resin composition and is 2 mass % or less relative to the second resin;
A pre-cut film characterized in that the tear strength at both ends is greater than the tear strength at the center. The pre-cut film described in claim 7, characterized in that the first resin is a polyimide-based resin. A pre-cut film as described in claim 7 or 8, characterized in that the CTE of the central portion is 5 ppm or more and 50 ppm/K or less. The pre-cut film according to any one of claims 7 to 9, characterized in that the filler is silica.